tag:theconversation.com,2011:/fr/topics/xray-436/articlesXray – The Conversation2018-02-25T21:11:05Ztag:theconversation.com,2011:article/903932018-02-25T21:11:05Z2018-02-25T21:11:05ZCurious Kids: Is x-ray vision possible?<figure><img src="https://images.theconversation.com/files/203702/original/file-20180129-100902-1us2up.png?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">X-ray vision is not only possible, it already exists -- but using computers, not eyes.</span> <span class="attribution"><span class="source">Marcella Cheng/The Conversation</span>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span></figcaption></figure><p><em>This is an article from <a href="https://theconversation.com/au/topics/curious-kids-36782">Curious Kids</a>, a series for children. The Conversation is asking kids to send in questions they’d like an expert to answer. All questions are welcome – serious, weird or wacky!</em> </p>
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<p><strong>Dear CSIRO, My name is Finn and I’m eight. I would like to know please if making x-ray vision is possible? Thank you so much for your help. – Finn, age 8, Brisbane.</strong> </p>
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<p>Hi Finn. Thanks for your question. X-ray vision is not only possible, it already exists! The science is called radiography. </p>
<p>As you know, human eyes don’t have x-ray vision. But we can use radiography machines to allow our eyes to see inside things the human eye cannot.</p>
<p>Radiography machines use different types of radiation (such as x-rays, visible light, or microwaves) to look inside objects. Some machines make a photograph of the object, called a radiograph, while others let you watch the object move and change in real time. </p>
<p>To make a simple radiograph using x-rays, for example, you need to shine your x-rays on the object you would like to see through. The x-rays pass right through the air and lighter stuff inside the object but are stopped by heavy or thick stuff (like bones). On the other side of the object you need a few fancy cameras, called “detectors”. The detectors produce the x-ray image by collecting the x-rays that make it through the object.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/203369/original/file-20180125-107937-1ifr4kb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/203369/original/file-20180125-107937-1ifr4kb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=437&fit=crop&dpr=1 600w, https://images.theconversation.com/files/203369/original/file-20180125-107937-1ifr4kb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=437&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/203369/original/file-20180125-107937-1ifr4kb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=437&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/203369/original/file-20180125-107937-1ifr4kb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=550&fit=crop&dpr=1 754w, https://images.theconversation.com/files/203369/original/file-20180125-107937-1ifr4kb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=550&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/203369/original/file-20180125-107937-1ifr4kb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=550&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A radiograph of a person’s arm, showing the x-ray source (the generator), the object (the man’s arm) and the detectors.</span>
<span class="attribution"><span class="source">Wikimedia</span></span>
</figcaption>
</figure>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-how-do-x-rays-see-inside-you-85895">Curious Kids: How do x-rays see inside you?</a>
</strong>
</em>
</p>
<hr>
<p>There are several radiography machines that you may have used before – such as a medical or dental x-ray machine. If you hurt your hand playing sport, a doctor may use x-rays to make a radiograph of your hand to see if you’ve broken a bone. The x-rays pass straight through the soft parts of your hand but are stopped by the thick and strong bones. The doctor uses the radiograph to see if the bones of your hand and fingers are broken. </p>
<p>At some point in your life, you will probably visit an airport. You might have been to one already. In the security line at the airport, you put your bag on the conveyor belt and it passes through an x-ray radiography machine. The operator can look right through your suitcase – without even touching it – to see what’s inside and make sure there’s nothing dangerous in there. You can then pick up your bag after it comes out of the machine without ever having to open it.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/203366/original/file-20180125-107940-1hgcore.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/203366/original/file-20180125-107940-1hgcore.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=465&fit=crop&dpr=1 600w, https://images.theconversation.com/files/203366/original/file-20180125-107940-1hgcore.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=465&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/203366/original/file-20180125-107940-1hgcore.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=465&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/203366/original/file-20180125-107940-1hgcore.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=584&fit=crop&dpr=1 754w, https://images.theconversation.com/files/203366/original/file-20180125-107940-1hgcore.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=584&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/203366/original/file-20180125-107940-1hgcore.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=584&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Baggage x-ray of a backpack. Can you identify some of the items inside?</span>
<span class="attribution"><span class="source">www.farlabs.edu.au</span></span>
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</figure>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-how-does-pain-medicine-work-in-the-body-82495">Curious Kids: How does pain medicine work in the body?</a>
</strong>
</em>
</p>
<hr>
<p>What else can you see using radiography? Scientists and engineers have designed powerful radiography machines that can see through objects much more interesting than a suitcase. </p>
<p>You can use these machines to see right through cars and trucks to check what they are carrying. You can see the flow of water or oil through big metal pipes. You can shine x-rays through walls, aeroplane wings, and even nuclear reactors to look for cracks or other problems that the human eye cannot see. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/203370/original/file-20180125-107971-1pufal1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/203370/original/file-20180125-107971-1pufal1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=306&fit=crop&dpr=1 600w, https://images.theconversation.com/files/203370/original/file-20180125-107971-1pufal1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=306&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/203370/original/file-20180125-107971-1pufal1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=306&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/203370/original/file-20180125-107971-1pufal1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=385&fit=crop&dpr=1 754w, https://images.theconversation.com/files/203370/original/file-20180125-107971-1pufal1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=385&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/203370/original/file-20180125-107971-1pufal1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=385&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Neutrons, another type of radiation, work differently than x-rays. Neutrons can shine straight through heavy objects like metals but are stopped by lighter objects. This picture is a neutron radiograph showing a soft flower inside a thick and heavy lead box.</span>
<span class="attribution"><span class="source">darpa.mil</span></span>
</figcaption>
</figure>
<p>Scientists and engineers also use radiography to help museums look inside very old objects that are too delicate to touch. This way, they can learn more about the object without breaking it. This has been used to see a 2000 year old mummy still inside a coffin, to see inside statues and paintings and to check whether objects in the museum are real or fake. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/203368/original/file-20180125-107967-mau8n1.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/203368/original/file-20180125-107967-mau8n1.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=376&fit=crop&dpr=1 600w, https://images.theconversation.com/files/203368/original/file-20180125-107967-mau8n1.PNG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=376&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/203368/original/file-20180125-107967-mau8n1.PNG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=376&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/203368/original/file-20180125-107967-mau8n1.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=473&fit=crop&dpr=1 754w, https://images.theconversation.com/files/203368/original/file-20180125-107967-mau8n1.PNG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=473&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/203368/original/file-20180125-107967-mau8n1.PNG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=473&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A computed tomography (CT) scan of an ancient Egyptian mummy.</span>
<span class="attribution"><span class="source">British Museum</span></span>
</figcaption>
</figure>
<p>The catch is – these machines use computers to make x-ray vision, not human eyes. If you believe the world needs Superman-style x-ray vision, become a scientist or engineer and make it happen!</p>
<p><em>Hello, curious kids! Have you got a question you’d like an expert to answer? Ask an adult to send your question to us. You can:</em></p>
<p><em>* Email your question to curiouskids@theconversation.edu.au
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<figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=376&fit=crop&dpr=1 600w, https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=376&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=376&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=472&fit=crop&dpr=1 754w, https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=472&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=472&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption"></span>
<span class="attribution"><a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
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<p><em>Please tell us your name, age and which city you live in. You can send an audio recording of your question too, if you want. Send as many questions as you like! We won’t be able to answer every question but we will do our best.</em></p><img src="https://counter.theconversation.com/content/90393/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Chanel Tissot is a member of the Australian Nuclear Association and Women in Nuclear Australia. </span></em></p>Human eyes don’t have x-ray vision. But we can use radiography machines to allow our eyes to see inside things the human eye cannot.Chanel Tissot, Postdoctoral Fellow, Nuclear Engineer, CSIROLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/150292013-09-16T02:43:00Z2013-09-16T02:43:00ZThe science of medical imaging: X-rays and CT scans<figure><img src="https://images.theconversation.com/files/29631/original/szcjshkq-1377050500.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Computed tomography uses computer-analysed X-rays to produce 'slices' of the body.</span> <span class="attribution"><span class="source">U.S. Pacific Fleet</span></span></figcaption></figure><p><em>Our short series, the Science of Medical Imaging, examines the technology behind non-invasive methods of creating images of the human body. In this article, we discuss the technique of transmission imaging, in which the radiation source originates from outside the patient.</em></p>
<p>Since the first incarnation of the computed tomography (<a href="https://en.wikipedia.org/wiki/X-ray_computed_tomography">CT</a>) scanner in 1975, devised by British engineer <a href="http://www.nobelprize.org/nobel_prizes/medicine/laureates/1979/hounsfield-bio.html">Godfrey Hounsfield</a> (for which he was awarded the Nobel prize in 1979), the use of the technique has exploded. </p>
<p>In the US alone, approximately <a href="http://www.usatoday.com/story/news/nation/2013/03/21/ct-scan-concerns/2005729/">70 million CT scans</a> are performed annually. </p>
<p>So why are they so popular?</p>
<p>Compared to <a href="https://theconversation.com/the-science-of-medical-imaging-spect-and-pet-14086">emission imaging</a> - a useful technique for detecting whether a tumour is present - transmission imaging, such as CT, can show precisely where the tumour is located with respect to surrounding organs. </p>
<p>The best-known form of transmission imaging is the medical <a href="https://en.wikipedia.org/wiki/Radiography">radiograph</a>, commonly referred to as an X-ray, as it uses an <a href="https://en.wikipedia.org/wiki/X-ray_generator">X-ray generator</a> as the source of photons to collect data on the medium that they pass through. </p>
<h2>The science behind radiographs</h2>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/27148/original/x8fxp956-1373349194.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/27148/original/x8fxp956-1373349194.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/27148/original/x8fxp956-1373349194.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=649&fit=crop&dpr=1 600w, https://images.theconversation.com/files/27148/original/x8fxp956-1373349194.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=649&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/27148/original/x8fxp956-1373349194.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=649&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/27148/original/x8fxp956-1373349194.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=815&fit=crop&dpr=1 754w, https://images.theconversation.com/files/27148/original/x8fxp956-1373349194.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=815&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/27148/original/x8fxp956-1373349194.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=815&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption"></span>
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<p>Figure A shows a simplified cartoon of a radiograph of a broken bone in 2D. </p>
<p>In the cartoon, the X-ray generator (source) is shown in red. The source produces 100 X-rays (yellow) at all six locations. The number of X-rays that reach the film (shown in the figure, left) is determined by the thickness of bone each X-ray beam (yellow arrow) intersects (assuming the bone is of uniform density). </p>
<p>The thicker the section of bone, the more electrons an X-ray encounters and the more likely it is the X-ray gets scattered or absorbed, and won’t reach the film. </p>
<p>The collective term for scattering and absorption is <a href="http://en.wikipedia.org/wiki/Attenuation">attenuation</a>. Therefore, a thicker section of bone attenuates more of the incident X-rays giving a <a href="http://en.wikipedia.org/wiki/Negative_%28photography%29">negative</a> image of the bone on the film.</p>
<p>Each material has an <a href="http://en.wikipedia.org/wiki/Attenuation_coefficient">attenuation coefficient</a>. This is a number showing how many X-rays of a given energy would pass through a material of a given density and thickness. </p>
<p>In reality your bones are not uniform in density and are surrounded by muscle and tissue, all with varying densities. So the radiograph maps the average attenuation coefficient along the path of the X-ray beam. </p>
<p>As we all know, a traditional radiograph only gives you a single 2D projection. This works well for a broken arm, but in parts of the body where there are different organs in the way, the 2D image gives clinicians no sense of the depth perspective as all of the body parts in the scan appear to sit on top of each other. </p>
<h2>Two to three dimensions</h2>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/27147/original/w5kx92zm-1373349082.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/27147/original/w5kx92zm-1373349082.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/27147/original/w5kx92zm-1373349082.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=572&fit=crop&dpr=1 600w, https://images.theconversation.com/files/27147/original/w5kx92zm-1373349082.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=572&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/27147/original/w5kx92zm-1373349082.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=572&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/27147/original/w5kx92zm-1373349082.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=719&fit=crop&dpr=1 754w, https://images.theconversation.com/files/27147/original/w5kx92zm-1373349082.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=719&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/27147/original/w5kx92zm-1373349082.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=719&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption"></span>
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<p>In order to obtain a more useful 3D image, clinicians have to take a series of 2D images (projections) at different angles and then perform a reconstruction step in software - known as CT.</p>
<p>Figure B (above right) shows a cartoon of a CT scanner at its starting position with no rotation. </p>
<p>The detector (green) is divided into small pixels (p1 to p20) to record the number of X-ray interactions (intensity) at each pixel location. </p>
<p>Placed between the source and the detector is a cranial phantom called the <a href="http://en.wikipedia.org/wiki/Shepp-Logan_Phantom">Shepp-Logan Phantom</a>. The word “phantom” refers to an industry standard representation that is agreed on by researchers so that they know they are comparing apples with apples.</p>
<p>The cranial phantom is in greyscale. The different colours of the components of the phantom are materials of different density, where white is the most dense and represents the skull.</p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/27137/original/xcvvnsg7-1373345166.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/27137/original/xcvvnsg7-1373345166.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/27137/original/xcvvnsg7-1373345166.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=405&fit=crop&dpr=1 600w, https://images.theconversation.com/files/27137/original/xcvvnsg7-1373345166.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=405&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/27137/original/xcvvnsg7-1373345166.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=405&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/27137/original/xcvvnsg7-1373345166.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=509&fit=crop&dpr=1 754w, https://images.theconversation.com/files/27137/original/xcvvnsg7-1373345166.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=509&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/27137/original/xcvvnsg7-1373345166.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=509&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
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</figure>
<p>In Figure C, the source of X-rays has been turned on. The varying numbers of counts in each detector pixel are due to differing densities and thicknesses of material that each X-ray beam intersects. </p>
<p>Instead of writing the actual number of X-rays that each pixel will detect, the intensity is shown here as a horizontal strip of colour on the right side of the image. In this greyscale colour strip, black represents a high intensity (lots of X-rays passing through this particular section of the head) and white is low intensity. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/27130/original/b4m3wdd5-1373343629.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/27130/original/b4m3wdd5-1373343629.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/27130/original/b4m3wdd5-1373343629.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=443&fit=crop&dpr=1 600w, https://images.theconversation.com/files/27130/original/b4m3wdd5-1373343629.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=443&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/27130/original/b4m3wdd5-1373343629.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=443&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/27130/original/b4m3wdd5-1373343629.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=556&fit=crop&dpr=1 754w, https://images.theconversation.com/files/27130/original/b4m3wdd5-1373343629.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=556&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/27130/original/b4m3wdd5-1373343629.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=556&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
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</figcaption>
</figure>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/27131/original/3rgx75hh-1373343657.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/27131/original/3rgx75hh-1373343657.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/27131/original/3rgx75hh-1373343657.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=401&fit=crop&dpr=1 600w, https://images.theconversation.com/files/27131/original/3rgx75hh-1373343657.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=401&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/27131/original/3rgx75hh-1373343657.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=401&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/27131/original/3rgx75hh-1373343657.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=504&fit=crop&dpr=1 754w, https://images.theconversation.com/files/27131/original/3rgx75hh-1373343657.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=504&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/27131/original/3rgx75hh-1373343657.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=504&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption"></span>
</figcaption>
</figure>
<p>Figure D shows what happens when the source and detector is rotated around the patient by 10 degrees. The intensity detected in pixels p1 to p20 is now stacked below that from the 0 degree projection on the right hand side of the image.</p>
<p>Figure E shows what happens when the process of rotating by 10 degrees repeats, and the intensity measurements are recorded all the way around to 180 degrees. </p>
<p>The clinician ends up with an intensity image with pixel position along one axis and rotation angle along the other axis. This image is called a <a href="http://en.wikipedia.org/wiki/Sinogram">sinogram</a>. Image reconstruction software analyses the sinogram to form an accurate anatomical representation of the patient’s skull.</p>
<h2>Reconstruction</h2>
<p>Getting from a sinogram to the image of what’s inside the patient is not trivial. The mathematics that unlocked this technique were first developed by the mathematician <a href="http://en.wikipedia.org/wiki/Johann_Radon">Johann Radon</a> in 1917. </p>
<p>Modern implementations of image reconstruction that enable fast and accurate reconstruction are based on work published by <a href="http://en.wikipedia.org/wiki/Larry_Shepp">Larry Shepp</a> and <a href="http://en.wikipedia.org/wiki/Benjamin_F._Logan">Benjamin Logan</a> (who have the phantom named after them) in 1974. </p>
<p>While CT scans have many benefits, the doctor must weigh up the pros and cons before prescribing it. On one hand, a CT scan provides essential detail that can aid diagnosis; on the other, radiation doses from CT are typically more than 100 times those from a conventional radiograph. </p>
<p>As such, the risk of inducing DNA damage that can <a href="https://theconversation.com/ct-scans-can-triple-risk-of-brain-cancer-leukemia-7532">lead to cancer</a> must be properly assessed, especially in children.
<br></p>
<p><strong>Further reading:</strong><br>
<a href="https://theconversation.com/the-science-of-medical-imaging-spect-and-pet-14086">SPECT and PET</a><br>
<a href="https://theconversation.com/the-science-of-medical-imaging-magnetic-resonance-imaging-mri-15030">MRI</a></p><img src="https://counter.theconversation.com/content/15029/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Matthew Dimmock does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Our short series, the Science of Medical Imaging, examines the technology behind non-invasive methods of creating images of the human body. In this article, we discuss the technique of transmission imaging…Matthew Dimmock, Researcher in Medical Imaging and X-ray Science, Australian SynchrotronLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/174322013-08-29T03:19:04Z2013-08-29T03:19:04ZEureka! X-ray vision can find hidden gold<figure><img src="https://images.theconversation.com/files/29987/original/4p5wyy87-1377579693.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Australian gold mines can yield as little as 1g of gold per tonne of rock – but X-rays can detect minuscule amounts of gold and save billions of dollars.</span> <span class="attribution"><span class="source">Ben Cooper</span></span></figcaption></figure><p>Globally, the minerals industry is operating in an increasingly challenging environment. Lower and more volatile metal prices, declining ore grades, increasing production costs, environmental pressures and mounting global competition all affect the sector.</p>
<p>At CSIRO we are working with the minerals industry to develop new technologies that will help maintain global competitiveness - and we recently <a href="http://www.csiro.au/Portals/Media/CSIRO-uses-x-ray-vision-to-detect-unseen-gold.aspx">announced</a> a new X-ray technology to do just this. </p>
<p>It has the potential to boost productivity and save the Australian gold industry hundreds of millions of dollars a year.</p>
<h2>The challenges of producing gold</h2>
<p>Gold in Australia is normally mined at very low grades - as little as <a href="http://www.nature.com/nature/journal/v495/n7440_supp/full/495S4a.html">one gram of gold for every tonne of rock</a>. Explorers looking for new gold deposits, and the people running mines or monitoring extraction plants, need a really sensitive detection method.</p>
<p>The industry standard analysis, <a href="http://en.wikipedia.org/wiki/Metallurgical_assay#Fire_assay_.2F_cupellation">fire-assay</a>, is complex, laborious and destroys samples by fusing them at temperatures up to 1,200C. </p>
<p>The process is normally carried out in centralised laboratories. This can lead to turn-around times of several days, particularly if materials are sent in from remote locations. Running a large processing plant is like trying to drive a truck looking only in the rear view mirror.</p>
<p>The lack of real-time feedback is one of the factors contributing to a typical gold plant only extracting 65-85% of the gold present in mined rock. And with Australia producing around A$10 billion worth of gold last year, billions of dollars worth of gold is potentially going to waste. </p>
<p>Even a 5% improvement in recovery efficiency would be worth half a billion dollars a year. Huge amounts of water and energy are required to extract gold, so this would also pay dividends in reducing the resources embedded in every ounce of metal.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/29980/original/brbrk86d-1377576380.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/29980/original/brbrk86d-1377576380.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/29980/original/brbrk86d-1377576380.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=650&fit=crop&dpr=1 600w, https://images.theconversation.com/files/29980/original/brbrk86d-1377576380.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=650&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/29980/original/brbrk86d-1377576380.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=650&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/29980/original/brbrk86d-1377576380.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=817&fit=crop&dpr=1 754w, https://images.theconversation.com/files/29980/original/brbrk86d-1377576380.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=817&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/29980/original/brbrk86d-1377576380.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=817&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption"></span>
<span class="attribution"><span class="source">CSIRO</span></span>
</figcaption>
</figure>
<h2>Our X-ray method</h2>
<p>Developed over the past decade, our method uses powerful <a href="https://theconversation.com/explainer-what-is-the-electromagnetic-spectrum-8046">X-rays</a>, similar to those that <a href="https://theconversation.com/explainer-what-is-cancer-1673">treat cancer patients</a>, to irradiate gold in ore samples. </p>
<p>The X-rays force nuclei at the heart of any gold atoms present into an excited state and this results in the gold atoms becoming weakly radioactive for just a few seconds. </p>
<p>A highly sensitive detector picks up the radiation emitted by the gold and reads out the level of the precious metal.</p>
<p>The big benefits of the method are simplicity, speed and accuracy. Up to half a kilogram of material is packed into a plastic jar and fed into the analyser. A few minutes later, the analysis is complete and the sample is returned unchanged. </p>
<p>As the method is completely non-destructive, the sample can be subjected to further testing if required. </p>
<p>Measuring a large mass of material improves accuracy. This is especially true for gold, as distribution can be very patchy even in a rich ore deposit.</p>
<p>One of the great advantages of using nuclear analysis is that it is sensitive to all forms of gold. It doesn’t matter what chemical or physical form the gold takes, or whether the sample is a solid or a liquid. If gold atoms are there, they will be seen and counted.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/29988/original/9836vjfv-1377579794.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/29988/original/9836vjfv-1377579794.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/29988/original/9836vjfv-1377579794.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=374&fit=crop&dpr=1 600w, https://images.theconversation.com/files/29988/original/9836vjfv-1377579794.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=374&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/29988/original/9836vjfv-1377579794.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=374&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/29988/original/9836vjfv-1377579794.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=470&fit=crop&dpr=1 754w, https://images.theconversation.com/files/29988/original/9836vjfv-1377579794.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=470&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/29988/original/9836vjfv-1377579794.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=470&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption"></span>
<span class="attribution"><span class="source">CSIRO</span></span>
</figcaption>
</figure>
<h2>Proving the new technology</h2>
<p>While the science behind using X-rays to find gold has been known for decades, achieving the necessary sensitivity was a major challenge. CSIRO combined the latest developments in high-power X-ray sources and radiation detectors with advanced computer modelling. This lead to an analyser capable of detecting gold at levels nearly ten times lower than previous systems. </p>
<p>We have recently completed tests in collaboration with the Canadian technology company <a href="http://www.mevex.com/">Mevex</a> which showed that our prototype analyser is capable of measuring gold two to three times more accurately than commercial laboratory fire-assay. We are now exploring how to bring the technology to market with Australian and international partners.</p>
<p>A X-ray based analysis system would probably be first used in a commercial assay laboratory. But things get really exciting when you think what might be possible beyond that. A complete, fully automated system could be packaged into a couple of shipping containers. This could be trucked out and dropped down for real-time, on-the-spot analysis in remote locations.</p>
<p>Some of the prospects for the technology include speeding up the exploration for gold and three-dimensional mapping of deposits by monitoring the spoil produced as bore-holes are being drilled. Helping to control the billion-dollar concentrator plants used to process gold ore would be another important application.</p>
<p>Any new technology is a jigsaw puzzle built around what starts out as just a crazy idea. The most satisfying part of working as an applied scientist is nurturing some of those ideas into the real world.</p>
<p>Rapid X-ray analysis is set to make a huge difference to the productivity and competitiveness of the gold industry. </p><img src="https://counter.theconversation.com/content/17432/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>As a result of this research, CSIRO has completed paid consulting work with industry.</span></em></p>Globally, the minerals industry is operating in an increasingly challenging environment. Lower and more volatile metal prices, declining ore grades, increasing production costs, environmental pressures…James Tickner, Office of the Chief Executive Science Leader, CSIROLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/137652013-05-30T05:52:55Z2013-05-30T05:52:55ZCutting-edge particle physics could bring cancer therapy home<figure><img src="https://images.theconversation.com/files/23556/original/3vnzf72n-1368392274.jpg?ixlib=rb-1.1.0&rect=0%2C39%2C1320%2C924&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The Hadron Collider was built to find the Higgs Boson but it might also help us discover better ways to treat cancer.</span> <span class="attribution"><span class="source">PA/CERN</span></span></figcaption></figure><p>The recent case of Neon Roberts <a href="http://www.guardian.co.uk/society/2012/dec/21/neon-roberts-radiotherapy-mother-wishes">and the legal dispute</a> over his treatment for a brain tumour threw the spotlight on the potential risks of using radiotherapy to treat complex cancers in children.</p>
<p>Radiotherapy is an effective way of targeting cancerous tumours but it can also affect the surrounding healthy tissues. Unpleasant side effects can include permanent damage to precious organs or the appearance of new cancers caused by the radiation - these are particularly difficult problems in growing children. Proton beam radiotherapy, which uses high energy charged particles (CPs) to target cancers more directly, can be less damaging than using X-rays but is hugely expensive. </p>
<p>Scientists behind the Large Hadron Collider at CERN are <a href="http://www.telegraph.co.uk/science/large-hadron-collider/10003417/Large-Hadron-Collider-scientists-developing-new-cancer-treatments.html">planning to develop the technology</a> - built to discover the higgs boson particle - to futher study how CPs can be used to kill cancer cells while limiting the amount of radiation for surrounding healthy tissues. </p>
<p>The project is not yet funded and would require considerable multinational support but the scientists at CERN are at the cutting edge of particle physics research and the opportunity to develop proton beam therapy is an important one.</p>
<p>In children, the risk of new cancers caused by radiation (which can appear two to 50 years after treatment) could be cut by using CPs. The reduction in unnecessary radiation should also make it more effective as a therapy for children with rare cancers - in the brain or the spine for example - and improve the quality of life for patients cured after radiation alongside other treatments such as surgery and chemotherapy.</p>
<p>But CPs and proton beam therapy is costly, largely because of the initial cost of the equipment. Expensive particle accelerators have only recently become commercially available and the treatment is only available <a href="http://www.clatterbridgecc.nhs.uk/patients/treatment/protontherapy/">in one hospital in the UK</a> which treats eye tumours. Since 2008, the majority of young people funded by the NHS are referred overseas.</p>
<p>This is where the Large Hadron Collider, the world’s largest particle accelerator, could prove useful in improving our knowledge of these beams and how different types of cells react to intense, localised radiation produced by these beams.</p>
<p>When a fast charged particle is used in treatment, it leaves a “dose” of ions (atoms with an electrical charge) along its path. The clustering of this ionisation changes according to the type of tissue and the distance the particle travels. Too much clustering of radiation in some areas causes bigger biological effects, which can be measured using something called the relative biological effect(RBE).</p>
<p>In principle, this RBE effect requires treatment to be varied according to different types of cancer in different parts of the body. In a brain cancer, for example, if the area around the tissue being treated contains important structures such as optic nerves which link the eyes to the brain, then serious damage will occur if the relative biological effect RBE is larger in these nerves than in the tumour. This could lead to blindness. This is less important in tissues such as the lungs and the special case of the liver, which is able to regenerate. Getting the sums wrong, though, could mean that too little radiation is sent to the tumour.</p>
<p>At present the scope for research in hospital-based CP centres is limited but there is considerable potential to develop CP technology, its dependability, accuracy and how someone receiving treatment goes through the process, with greater use of automation and computers.</p>
<p>Scientists at CERN are already working to develop smaller proton beam devices that could be used in hospitals and have also identified one type of particle accelerator that could be modified in order to study RBE. This can also be tested on “phantoms” - artificial humanoid body like shapes - to simulate the conditions within the body. </p>
<p>High quality imaging technology such as CT and MR scanners are also essential to the success of CP therapy, but if this type of therapy is developed further and costs brought down, it means that more people - and children - will be able to have their treatment here at home. </p><img src="https://counter.theconversation.com/content/13765/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Bleddyn Jones has previously received grants form Medical Research Council UK</span></em></p>The recent case of Neon Roberts and the legal dispute over his treatment for a brain tumour threw the spotlight on the potential risks of using radiotherapy to treat complex cancers in children. Radiotherapy…Bleddyn Jones, Professor of Clinical Radiation Biology, University of OxfordLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/80462012-08-15T05:09:02Z2012-08-15T05:09:02ZExplainer: what is the electromagnetic spectrum?<figure><img src="https://images.theconversation.com/files/13994/original/bkzhp6vb-1344391570.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Imagine a magic prism for the entire range of electromagnetic waves.</span> <span class="attribution"><span class="source">TORLEY</span></span></figcaption></figure><p>Visible light forms part of the electromagnetic spectrum. So do emissions from TV and radio transmitters, mobile phones and the energy inside microwave ovens. </p>
<p>The X-rays used in <a href="http://www.wisegeek.com/what-is-diagnostic-imaging.htm">diagnostic imaging</a> and the materials used in advanced positron emission tomography scanners (<a href="http://www.betterhealth.vic.gov.au/bhcv2/bhcarticles.nsf/pages/PET_scan">PET</a>) also form part of this amazing range of <a href="http://en.wikipedia.org/wiki/Radiation">radiations</a> which share some features in common.</p>
<h2>Why electromagnetic?</h2>
<p>As the name implies, they have <a href="http://www.niehs.nih.gov/health/topics/agents/emf/">electric and magnetic fields</a> associated with them. Although it is a bit complicated to demonstrate these fields in the case of light and X-rays, it is quite easy to picture with <a href="http://science.hq.nasa.gov/kids/imagers/ems/radio.html">radio-waves</a>.</p>
<p>Consider the wires shown below, in which an electric charge has been placed at the tips as shown (don’t worry about the technicalities – it’s a bit like the static charge that appears in dry hair when combed vigorously). </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/13978/original/pmftqh9n-1344389240.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/13978/original/pmftqh9n-1344389240.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=511&fit=crop&dpr=1 600w, https://images.theconversation.com/files/13978/original/pmftqh9n-1344389240.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=511&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/13978/original/pmftqh9n-1344389240.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=511&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/13978/original/pmftqh9n-1344389240.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=642&fit=crop&dpr=1 754w, https://images.theconversation.com/files/13978/original/pmftqh9n-1344389240.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=642&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/13978/original/pmftqh9n-1344389240.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=642&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Electric field (E) due to positive and negative charge separated by a distance (d).</span>
<span class="attribution"><span class="source">Andrew Wood.</span></span>
</figcaption>
</figure>
<p>This pair of charges (plus and minus) sets up an electric field, with the imaginary field lines shown. If now the charge is allowed to flow along the wire, this will set up a magnetic field as shown by the concentric circles. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/13981/original/68nbvkky-1344389457.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/13981/original/68nbvkky-1344389457.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=327&fit=crop&dpr=1 600w, https://images.theconversation.com/files/13981/original/68nbvkky-1344389457.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=327&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/13981/original/68nbvkky-1344389457.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=327&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/13981/original/68nbvkky-1344389457.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=411&fit=crop&dpr=1 754w, https://images.theconversation.com/files/13981/original/68nbvkky-1344389457.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=411&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/13981/original/68nbvkky-1344389457.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=411&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Magnetic field (B) due to the flow of electric charge along the wires.</span>
<span class="attribution"><span class="source">Andrew Wood</span></span>
</figcaption>
</figure>
<p>A long way away from this arrangement (which is called a <a href="http://www.radio-electronics.com/info/antennas/dipole/dipole.php">dipole antenna</a>) the electric and magnetic fields are at right angles. If the charge generator alternates between having plus and minus at the top, the field direction will also alternate, as shown, with a time period T between positive-going peaks (1 cycle).</p>
<p>Since the generator has to do work to alternately put charge one way and then the other, this work (energy) is constantly streaming from the wires, out into the surrounds. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/13980/original/r39s95g2-1344389320.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/13980/original/r39s95g2-1344389320.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=361&fit=crop&dpr=1 600w, https://images.theconversation.com/files/13980/original/r39s95g2-1344389320.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=361&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/13980/original/r39s95g2-1344389320.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=361&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/13980/original/r39s95g2-1344389320.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=454&fit=crop&dpr=1 754w, https://images.theconversation.com/files/13980/original/r39s95g2-1344389320.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=454&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/13980/original/r39s95g2-1344389320.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=454&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">As the charge alternates between positive to negative at the upper wire in Figure 1, the direction of the E and B fields alternate with a smooth transition (“sinusoid”) between the positive and negative peaks. The distance in time between two successive similar peaks is called the “period” T.</span>
<span class="attribution"><span class="source">Andrew Wood</span></span>
</figcaption>
</figure>
<p>This is why it is called “radiation”, because it is radiating outwards. In fact, at a particular point, the fields will appear to be moving past at a particular speed.</p>
<p>This speed is the velocity of light (which in vacuum is 3 x 10<sup>8</sup> m/s, or 300,000 km/s). Even if the electromagnetic waves are invisible radio-waves or X-rays, for example, they still go at this speed. The energy spreads out over a larger and larger area as it moves away from the source, often the same in all directions. </p>
<p>In this case, the area it spreads over is the area of a sphere (4 r<sup>2</sup> ), thus there is an “<a href="http://www.portraitlighting.net/inversesquare_law.htm">inverse square law</a>” of energy density, since for a particular area (1 cm<sup>2</sup> , say) the energy falls by a factor of 1/r<sup>2.</sup></p>
<p>The other thing to notice is that if the wave is travelling at the speed of light ( c ) and the time for 1 cycle is T, then the length of 1 cycle (wavelength) is c x T. The table below shows the wavelengths of typical forms of radiation.</p>
<h2>Why spectrum?</h2>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/13986/original/23dtwnfq-1344390088.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/13986/original/23dtwnfq-1344390088.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=428&fit=crop&dpr=1 600w, https://images.theconversation.com/files/13986/original/23dtwnfq-1344390088.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=428&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/13986/original/23dtwnfq-1344390088.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=428&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/13986/original/23dtwnfq-1344390088.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=538&fit=crop&dpr=1 754w, https://images.theconversation.com/files/13986/original/23dtwnfq-1344390088.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=538&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/13986/original/23dtwnfq-1344390088.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=538&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Diagram of a dispersion prism.</span>
<span class="attribution"><span class="source">Wikicommons</span></span>
</figcaption>
</figure>
<p>A spectrum is what you get by passing light through a glass prism – the white light is split into its component colours.</p>
<p>Imagine a magic prism which could do this for the entire range of electromagnetic waves. Such a device does not exist, but if it did, wavelengths ranging from thousands of kilometres (<a href="http://hps.org/hpspublications/articles/elfinfosheet.html">Extremely Low Frequency</a> or ELF) through to sizes smaller than an atom would be produced. </p>
<p>For the radio-frequencies, there is a device, called a <a href="http://www.radio-electronics.com/info/t_and_m/spectrum_analyser/spectrum_analyzer.php">spectrum analyser</a>, which does this for particular ranges. Modern mobile telephony uses “<a href="http://www.ausairpower.net/OSR-0597.html">spread spectrum</a>” technology, so a network analyser can be used to measure the amount of <a href="http://en.wikipedia.org/wiki/Radio_frequency">radio frequency</a> (RF) energy spread out over a range of frequencies, much in the same way a glass prism does for light.</p>
<h2>Why ionising and non-ionising?</h2>
<p>Although both RF and X-rays are referred to as radiation, they interact with the body in a fundamentally different way: X-rays can remove electrons from atoms (turning them into <a href="http://www.microncorp.com/energaire/ions.html">ions</a>, hence ionising), whereas RF cannot (hence non-ionising). </p>
<p>The reason that exposure to high intensities of X-rays (and other rays, such as gamma rays and X-rays) is linked to cancer, is that the ionisation can lead to changes in genetic material which cannot be repaired. </p>
<p>Non-ionising radiation has not been shown to do this. The main effect of RF radiation is to cause heating (as in a microwave oven). Lower frequencies (such as ELF) can lead to the direct stimulation of nerves and muscles, rather than heating.</p>
<p>Using computer models of the human body (consisting of elements as small as 1mm cubes, and with the electrical properties of different types of tissue represented appropriately) it is possible to compute how much increase in temperature there will be in the parts of the head next to a mobile phone handset, when in operation. </p>
<p>With blood-flow properly included, the increase in temperature is much less than 1ºC, in fact much less than the natural variation in temperature over a 24-hour cycle.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/13991/original/98zgbrw8-1344391126.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/13991/original/98zgbrw8-1344391126.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=429&fit=crop&dpr=1 600w, https://images.theconversation.com/files/13991/original/98zgbrw8-1344391126.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=429&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/13991/original/98zgbrw8-1344391126.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=429&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/13991/original/98zgbrw8-1344391126.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=539&fit=crop&dpr=1 754w, https://images.theconversation.com/files/13991/original/98zgbrw8-1344391126.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=539&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/13991/original/98zgbrw8-1344391126.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=539&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The electromagnetic spectrum.</span>
<span class="attribution"><span class="source">NASA</span></span>
</figcaption>
</figure>
<h2>Natural vs “unnatural”</h2>
<p>There are now many who are concerned about “<a href="http://www.guardian.co.uk/technology/2007/jan/18/guardianweeklytechnologysection4">electrosmog</a>” – the soup of emissions from consumer electronics that, to a greater or lesser extent, we are all exposed to (such as wireless routers, Bluetooth connections, smart meters). </p>
<p>It is perhaps comforting that, even before the advent of modern technologies, we were still exposed to various forms of electromagnetic radiation, principally from the sun (ranging from ultraviolet, through visible to infra-red), but also from natural (ionising) radioactivity, from various rocks such as granite and uranium ores. </p>
<p>In addition to the relatively strong magnetic field of Earth, various atmospheric phenomena, such as lightning, produce ELF and RF fields. </p>
<p>Remember also that the heart, brain, muscles and nerves all have electrical currents associated with them: diagnostic systems such as the well-known <a href="http://www.scholarpedia.org/article/Electroencephalogram">electroencephalogram</a> measure body-generated electric fields and more advanced systems also measure the magnetic fields generated by the brain and other organs. </p>
<p>There is no evidence that the introduction of radio broadcasting at the start of the 20th century was associated with an increased incidence of disease. Life expectancies in general have increased significantly over the last 100 years, with a contribution from superior diagnostic procedures (computed tomography – which uses X-rays; and magnetic resonance imaging – which uses RF and strong magnetic fields) that exploitation of the electromagnetic spectrum has allowed.</p>
<p><br>
<em>See more <a href="https://theconversation.com/topics/explainer">Explainer articles</a> on The Conversation.</em></p><img src="https://counter.theconversation.com/content/8046/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Andrew W Wood collaborates with scientists and engineers employed by Telstra Corporation and his self-managed superannuation fund includes Telstra shares (around 5%). He receives funding from NHMRC and in the past from ARC, Telstra and some electrical utilities. He is affiliated with the Australian Radiation Protection and Nuclear Safety Agency (ARPANSA).</span></em></p>Visible light forms part of the electromagnetic spectrum. So do emissions from TV and radio transmitters, mobile phones and the energy inside microwave ovens. The X-rays used in diagnostic imaging and…Andrew W Wood, Chair, Department of Biomedical and Health Sciences, Swinburne University of TechnologyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/63432012-04-12T04:42:39Z2012-04-12T04:42:39ZStreeton, Da Vinci and the science of seeing art’s secrets<figure><img src="https://images.theconversation.com/files/9509/original/bxstph2k-1334196571.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The collision of art and science is producing some impressive results.</span> <span class="attribution"><span class="source">CSIRO, Australian Synchrotron and National Gallery of Victoria</span></span></figcaption></figure><p>The ability to see through walls and other objects <a href="http://www.ncbi.nlm.nih.gov/pubmed/6676715">Superman-style</a> is surely high on the wish-list for many children. </p>
<p>Sadly, with the purchase of a child’s first pair of <a href="http://www.flickr.com/photos/akhir/4524376496/lightbox/">novelty X-ray glasses</a>, such dreams rapidly fade – plastic glasses do not create superpowers or enhance vision.</p>
<p>Until recently, we scientists felt a similar disappointment when we applied X-ray technology to paintings.</p>
<p>But thanks to technological advances and the
<a href="http://www.ncbi.nlm.nih.gov/pubmed/22414158">analysis of an Arthur Streeton self-portrait</a> we’ve managed to bring art and science together in a fascinating way.</p>
<p>Historically, artists have been known to recycle canvases by painting over their artwork to save money. Up until the early part of the 20th century, this was often done with white lead paint.</p>
<p>What we’re trying to do is use X-ray technology to look through the lead paint and see the artwork that was first laid on to a canvas.</p>
<p>In doing this, we might find hidden images or changes in the development of the image by the artist.</p>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/9511/original/qqwf5xcj-1334205050.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/9511/original/qqwf5xcj-1334205050.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=797&fit=crop&dpr=1 600w, https://images.theconversation.com/files/9511/original/qqwf5xcj-1334205050.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=797&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/9511/original/qqwf5xcj-1334205050.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=797&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/9511/original/qqwf5xcj-1334205050.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1001&fit=crop&dpr=1 754w, https://images.theconversation.com/files/9511/original/qqwf5xcj-1334205050.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1001&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/9511/original/qqwf5xcj-1334205050.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1001&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
<span class="attribution"><span class="source">Phantom Leap</span></span>
</figcaption>
</figure>
<p>But it’s not that simple.</p>
<p>One of the key challenges posed by historical paintings is the composition of the paint, which contains heavy elements – including lead and mercury – that obscure traditional X-ray images. (Think of it as an unintentional version of those lead gowns you are asked to wear during medical X-rays to protect your insides). </p>
<p>It’s only in the last couple of years with the advent of more advanced <a href="http://serc.carleton.edu/research_education/geochemsheets/techniques/XRF.html">X-ray fluorescence (XRF) spectroscopy</a> techniques that we have been able to generate a much clearer picture of what lies beneath some of the world’s most significant works of art.</p>
<p>In 2010, the use of XRF spectroscopy <a href="http://www.bbc.co.uk/news/entertainment-arts-10670133">hit the headlines</a> when the French National Museum used it to perform an analysis of Da Vinci’s Mona Lisa.</p>
<p>In that instance experts were able to probe the 500-year-old masterpiece without even taking it down from the wall, providing unique insight into the mind of the artist.</p>
<p>The scan revealed each layer of glaze, paint and <a href="http://en.wikipedia.org/wiki/Pigment">pigment</a>, and gave researchers a better understanding of Da Vinci’s painstaking shading technique, known as <a href="http://www.britannica.com/EBchecked/topic/537371/sfumato">“sfumato”</a>.</p>
<p>One of the key strengths of XRF spectroscopy (which can be performed at synchrotrons and is thereby known as Synchrotron XRF) imaging is its ability to reveal the distribution of the pigments of underlying brushstrokes.</p>
<p>The technique characterises a wide range of pigments, and because different pigments were favoured, or came into use as artists’ colours at specific times in history, it can ultimately indicate provenance and attribution. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/AS_vkwdvpCU?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<p>Synchrotron XRF uses a beam of high-energy X-rays to penetrate each layer of paint, creating a more complete picture of the strokes, chemicals and materials on a canvas.</p>
<p>This information is analysed and translated into elemental data sets which are used to reveal images and other elements previously invisible.</p>
<p>Some recent research at CSIRO by my colleagues and I saw us using a beamline at the <a href="http://www.synchrotron.org.au/">Australian Synchotron</a> to analyse a self-portrait by Australian impressionist artist <a href="http://adb.anu.edu.au/biography/streeton-sir-arthur-ernest-8697">Arthur Streeton</a>. </p>
<p>Our analysis of the painting, which is in the <a href="http://www.ngv.vic.gov.au/.">National Gallery of Victoria’s</a> care, was not just concerned with unearthing the image hidden underneath thick layers of lead-based white paint, but also perfecting the technique which would allow us to perform an in-depth analysis of the painting without damaging it.</p>
<p>Before performing any work on the Streeton painting, we applied historic paints actually used by Streeton to canvas swatches and irradiated them with a dose 1,000-times greater than the actual scanner would expose the painting to.</p>
<p>At no point was damage observed. This is important because if art galleries are going to give us access to paintings, they want to know we aren’t going to damage them, and rightly so. </p>
<p>The next challenge was to ensure a stable environment to house the painting in – similar to the carefully controlled conditions and climate at the National Gallery of Victoria.</p>
<p>To perform a scan of the painting we used the CSIRO-developed <a href="http://www.csiro.au/en/Outcomes/Materials-and-Manufacturing/Maia-x-ray-microprobe-elemental-imaging-system.aspx">Maia scanner</a>, one of the most advanced in the world.</p>
<p>One of the main advantages of the Maia scanner is that it allows paintings to be scanned quickly, minimising the time the artwork needs to be away from the gallery. It also allows the entire painting to be scanned, not just a cross-section.</p>
<p>(Cross-sections from paintings are in the order of a quarter of a millimetre or smaller, and are taken judiciously to understand the materials and paint layer structure. They are painstaking and time-consuming to prepare for analysis.)</p>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/9510/original/fjr6b248-1334197998.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/9510/original/fjr6b248-1334197998.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=901&fit=crop&dpr=1 600w, https://images.theconversation.com/files/9510/original/fjr6b248-1334197998.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=901&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/9510/original/fjr6b248-1334197998.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=901&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/9510/original/fjr6b248-1334197998.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1132&fit=crop&dpr=1 754w, https://images.theconversation.com/files/9510/original/fjr6b248-1334197998.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1132&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/9510/original/fjr6b248-1334197998.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1132&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">XRF spectroscopy revealed new information about the creation of the Mona Lisa.</span>
<span class="attribution"><span class="source">Joaquín Martínez Rosado</span></span>
</figcaption>
</figure>
<p>Our scan of the Streeton painting using the synchrotron with the Maia detector took 22 hours – about a fifth of the time it would take us to perform using traditional XRF techniques. </p>
<p>Using the tunability (ability to select the exact energy of the X-ray beam used) and monochromatic (very narrow frequency) properties of the synchrotron beam we were able to obtain the maximum amount of information about elements that lay under the surface of the painting. </p>
<p>This despite the thick layer of white lead-based paint that covered it. </p>
<p>The images we captured were at tens of megapixels and with a <a href="http://micro.magnet.fsu.edu/primer/java/digitalimaging/processing/spatialresolution/">spatial resolution</a> (the size of the smallest detectable element) of tens of microns, where one micron is a millionth of a metre.</p>
<p>The result was a very clear image of Arthur Streeton’s self-portrait (see main image above) and the development of a new process for analysing paintings quickly and without impact on the integrity of the painting.</p>
<p>Given the ubiquitous use of lead white paint in historic paintings, our hope is that this technique will be applied to other artworks in the future.</p>
<p>This is an exciting prospect for science, but could be quite a confronting concept for the art world. The complexity of the science involved will be a new realm for art historians and curators and may even result in some theories about particular artists being upturned. </p>
<p>There is no doubt there are dozens of paintings out there with questions against their authenticity or origin. As this technique is gradually refined there will be fewer places for the secrets of art to hide.</p>
<p>Of course, others might argue that those secrets are part of what makes art attractive.</p><img src="https://counter.theconversation.com/content/6343/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Deborah Lau does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>The ability to see through walls and other objects Superman-style is surely high on the wish-list for many children. Sadly, with the purchase of a child’s first pair of novelty X-ray glasses, such dreams…Deborah Lau, Research Program Leader, Surfaces and Nanosciences, CSIROLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/40462012-03-28T19:45:52Z2012-03-28T19:45:52ZEminence or evidence? The ethics of using untested treatments<figure><img src="https://images.theconversation.com/files/9083/original/xj972khq-1332913767.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">New therapies that haven't yet been clinically proven may still be used ethically under certain circumstances.</span> <span class="attribution"><span class="source">Juraj Kubica</span></span></figcaption></figure><p><strong>TRANSPARENCY AND MEDICINE – A series examining issues from ethics to the evidence in evidence-based medicine, the influence of medical journals to the role of Big Pharma in our present and future health.</strong></p>
<p><strong>Today, Loane Skene considers circumstances in which it may be appropriate for a relatively untested treatment to be offered to patients.</strong></p>
<p>There are times when a new therapy seems superior to existing treatments. But is it ethical to offer people a new treatment that some clinicians believe from treating their patients is effective (“eminence-based” treatment), but which hasn’t been subject to properly designed clinical trials (“evidence-based” treatment)?</p>
<p>One example of such a treatment is charged particle therapy (CPT), which uses protons or light ions, such as carbon, to treat cancerous tumours instead of conventional X-ray therapy. CPT is about 2.4 times more expensive and it hasn’t been subject to randomized clinical trials.</p>
<p>Generally, we expect such trials to take place before an alternative treatment is used to treat patients. But some experts in the field believe there’s sufficient evidence from physics and reported cases to show that CPT has advantages over conventional X-ray treatment. </p>
<p>CPT can be confined more closely to the region to be treated, for instance, whereas conventional techniques are much broader and bring with them the risk of affecting healthy tissue as well as the tumour. </p>
<p>Some doctors have been offering the treatment to their patients and more than 70,000 people have now been treated worldwide with CPT, mainly for eye tumours. </p>
<h2>Ethics of untested treatment</h2>
<p>These issues were considered at <a href="http://www.ptcri.ox.ac.uk/CPTREthics/index.shtml">a recent, cross-disciplinary, international workshop</a> hosted by the Oxford Martin School. </p>
<p>The workshop was described as a world first because of its focus on the ethical process for introducing a specific alternative treatment in the face of scientific uncertainty. </p>
<p>A resulting report is yet to be published but the following are some of the principles for proceeding ethically with new treatments. They are based on my impression of discussions at the workshop and not the report itself:</p>
<ul>
<li><p>It’s ethical to enrol patients in a randomized clinical trial if there’s some uncertainty or reasonable doubt about whether one treatment or another is better. This is the principle of equipoise that justifies medical research. </p></li>
<li><p>In deciding whether there’s reasonable doubt about the efficacy of a treatment, a comprehensive range of stakeholders from various disciplines should be consulted, including those with different views. </p></li>
<li><p>A thorough review of current practice, open to the public, should be undertaken, including a review of the available evidence and the quality of that evidence. </p></li>
<li><p>Even if this process establishes a “reasoned” disagreement in the community of scientific experts, or finds a lack of evidence about the better alternative (making a randomized clinical trial ethically justifiable) that doesn’t mean it’s always ethically necessary or desirable to conduct such a trial. </p></li>
<li><p>There may be sufficient reason to offer the alternative treatment if there’s evidence from data sharing – reports from researchers and clinicians worldwide on the use of an alternative therapy for their patients. </p></li>
<li><p>To be statistically sound, all patients treated with this therapy would need to be recorded, perhaps overseen by an independent organization, including any negative results and side-effects, using standardized protocols and data collection. </p></li>
<li><p>Even if clinical trials are ethically justified, individual clinicians are not ethically required to enrol their patients in a trial. Exercising clinical judgment, they may disagree with other experts, have limited facilities to use the new therapy, or believe their patients aren’t suitable for the new treatment. </p></li>
<li><p>Patient or community representatives, who can understand the risks for patients, should be consulted about whether particular research and clinical treatment should proceed. </p></li>
<li><p>Research ethics committees should be responsible for protecting participants from undue risks. They would do this by ensuring risks are minimized by sound study design and are reasonable in view of the knowledge to be gained. </p></li>
<li><p>Patients are entitled to decide for themselves whether to participate in a clinical trial, weighing up quality of life and survival, and taking risks to help the community, guided by their own clinician on the accepted principles of informed consent. </p></li>
</ul>
<h2>Applying these principles to CPT</h2>
<p>Some experts strongly believe CPT has great potential and can ethically be used before clinical trials have been conducted. </p>
<p>Other clinicians say there’s limited evidence about the efficacy and safety of CPT and studies to date have been mainly retrospective with small numbers. </p>
<p>They say:</p>
<ul>
<li><p>tissues may be affected differently by different types of radiation; </p></li>
<li><p>it’s difficult to ensure the particles in CPT are delivered to the precise target; and, </p></li>
<li><p>if there’s an error, consequences may be serious for the patient, such as paralysis and double incontinence when treating a tumour near the spine. </p></li>
</ul>
<p>This disagreement among the community of experts justifies clinical trials being undertaken. Research ethics committees would then assess the potential risks for patients before approving the trials. </p>
<p>Clinicians would decide whether to enrol particular patients. And patients would decide whether to participate if offered the opportunity.</p>
<p>But CPT could ethically continue to be offered to patients without clinical trials if clinicians are willing to do this, subject to ethical oversight and patient consent. In Australia, the approval of the Therapeutic Goods Administration would presumably also be required.</p>
<p>There is some evidence that CPT is effective and more information will be collected as more treatments are offered. The number of machines and centres offering CPT is increasing exponentially, doubling every eight years, so it is increasingly being funded and used.</p>
<p>If there is a reasoned disagreement between experts about new treatment, a clinical trial is justified but treatment can ethically be given in the interim if there is other evidence of its efficacy from case reports and data sharing.</p>
<p><strong>This is the fourth part of Transparency and Medicine. You can read other instalments by clicking the links below:</strong> </p>
<p><strong>Part One: <a href="https://theconversation.com/power-and-duty-is-the-social-contract-in-medicine-still-relevant-3941">Power and duty: is the social contract in medicine still relevant?</a></strong></p>
<p><strong>Part Two: <a href="https://theconversation.com/big-debts-in-small-packages-the-dangers-of-pens-and-post-it-notes-4949">Big debts in small packages – the dangers of pens and post-it notes</a></strong></p>
<p><strong>Part Three: <a href="https://theconversation.com/show-and-tell-conflicts-of-interest-undeclared-for-clinical-guidelines-3890">Show and tell: conflicts of interest undeclared for clinical guidelines</a></strong></p>
<p><strong>Part Five: <a href="https://theconversation.com/dont-show-me-the-money-the-dangers-of-non-financial-conflicts-5013">Don’t show me the money: the dangers of non-financial conflicts</a></strong></p>
<p><strong>Part Six: <a href="https://theconversation.com/ghosts-in-the-machine-better-definition-of-author-may-stem-bias-4288">Ghosts in the machine: better definition of author may stem bias</a></strong></p>
<p><strong>Part Seven: <a href="https://theconversation.com/clearing-the-air-why-more-retractions-are-good-for-science-6008">Clearing the air: why more retractions are good for science</a></strong></p>
<p><strong>Part Eight: <a href="https://theconversation.com/pharmas-influence-over-published-clinical-evidence-5325">Pharma’s influence over published clinical evidence</a></strong></p>
<p><strong>Part Nine: <a href="https://theconversation.com/insight-into-how-pharma-manipulates-research-evidence-a-case-study-4071">Insight into how pharma manipulates research evidence: a case study</a></strong></p>
<p><strong>Part Ten: <a href="https://theconversation.com/why-data-from-published-trials-should-be-made-public-5599">Why data from published trials should be made public</a></strong></p>
<p><strong>Part Eleven: <a href="https://theconversation.com/open-disclosure-why-doctors-should-be-honest-about-errors-4070">Open disclosure: why doctors should be honest about errors</a></strong></p>
<p><strong>Part Twelve: <a href="https://theconversation.com/reaching-full-and-open-disclosure-for-universities-medical-schools-and-doctors-6004">Reaching full and open disclosure for universities, medical schools and doctors</a></strong></p>
<p><strong>Part Thirteen: <a href="https://theconversation.com/ethics-of-accepting-suppliers-gifts-in-the-business-v-medical-world-3968">Ethics of accepting suppliers’ gifts in the business v medical world</a></strong></p>
<p><strong>Part Fourteen: <a href="https://theconversation.com/conflicts-of-interest-in-guideline-development-the-nhmrc-responds-6395">Conflicts of interest in guideline development: the NHMRC responds</a></strong></p>
<p><strong>Part Fifteen: <a href="https://theconversation.com/consumer-input-in-medicines-australias-code-of-conduct-review-6370">Consumer input in Medicines Australia’s code of conduct review</a></strong></p><img src="https://counter.theconversation.com/content/4046/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Loane Skene does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>TRANSPARENCY AND MEDICINE – A series examining issues from ethics to the evidence in evidence-based medicine, the influence of medical journals to the role of Big Pharma in our present and future health…Loane Skene, Professor of Law & Adjunct Professor, Faculty of Medicine Dentistry and Health Sciences, The University of MelbourneLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/20492011-06-29T04:13:16Z2011-06-29T04:13:16ZBone of contention: can wrist X-rays really reveal the age of people smugglers?<figure><img src="https://images.theconversation.com/files/1977/original/aapone-20091022000208288746-indonesia-australia-sri_lanka-immigration-refugees-original.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The AFP is using wrist x-rays to determine whether refugee boat crew members should face a 5-year jail term.</span> <span class="attribution"><span class="source">AAP</span></span></figcaption></figure><p>The current Australian Federal Police practice of using<a href="http://www.betterworldbooks.com/radiographic-atlas-of-skeletal-development-of-the-hand-and-wrist-id-0804703981.aspx?PageVersion=Alt"> X-rays of the hand/wrist to assess the age of Indonesian crew members of boats bringing refugees to Australia is based on a method developed in the 1950s</a>. The technique is outdated, inaccurate and raises ethical concerns.</p>
<p>If the crew members, who claim to be under 18, are found to be adults, they must face mandatory five-year jail terms under people smuggling laws.</p>
<p>Hand/wrist X-ray examination was designed as a tool to assess the general physical development of children rather than to determine chronological age, and its degree of error is unknown but likely to be quite large. </p>
<p>Biological variation in human development means that any assessment of age based on analysis of anatomical growth markers is only an estimate, and will inevitably contain a degree of error. </p>
<p>While there’s no foolproof way to determine the exact age of an individual without verified birth date documentation, there <em>are</em> better methods available. </p>
<p>The size of inherent error in determining age depends, in large measure, on the estimation methods used so it behoves the government to use better tools in what is a determination with very serious ramifications. </p>
<h2>The inherent fallibility of hand/wrist x-rays</h2>
<p>Hand/wrist X-rays rely on an anatomical atlas of standard hand/wrist X-rays taken of a group of 1000 middle-class American children from birth to nineteen years in the 1930s and 1940s. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/1974/original/2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/1974/original/2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/1974/original/2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/1974/original/2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/1974/original/2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=565&fit=crop&dpr=1 754w, https://images.theconversation.com/files/1974/original/2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=565&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/1974/original/2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=565&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">X-ray of the wrists of a six-year-old child.</span>
<span class="attribution"><span class="source">Richard Bassed</span></span>
</figcaption>
</figure>
<p>This atlas displays standard skeletal development at three-month intervals during the first year of life; six-month intervals from one to five years; and one year intervals thereafter, up to 19. </p>
<p>At no point does this technique claim to be able to determine chronological age; it was designed as a tool for health workers to better assess children’s skeletal development and overall growth.</p>
<p>Quite clearly, the major drawback when using this technique today is that individuals included in the atlas grew up on the other side of the world more than 60 years ago. The economic circumstances and general public health then aren’t comparable to what prevails now.</p>
<p>It’s clearly unlikely an American child in the 1940s developed at the same rate at which an Iraqi, Afghani, Indonesian or indeed an Australian child will develop today.</p>
<p>Even if the atlas accurately reflected current growth trends, it would still be of limited use in predicting chronological age. </p>
<p>The variability inherent in the model means that for a boy predicted to be 17 years old, there is a standard deviation of 15.4 months. This means that the boy’s age could have the possible range of 17 plus or minus two-and-a-half years. He could therefore, be aged anywhere from 14.5 to 19.5 years. </p>
<p>Plainly, if the question being asked is whether or not this person is an adult or still a minor, this method cannot possibly provide an accurate answer.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/1978/original/11.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/1978/original/11.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=839&fit=crop&dpr=1 600w, https://images.theconversation.com/files/1978/original/11.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=839&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/1978/original/11.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=839&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/1978/original/11.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1055&fit=crop&dpr=1 754w, https://images.theconversation.com/files/1978/original/11.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1055&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/1978/original/11.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1055&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">X-ray of an older child’s wrist – at approximately 11 or 12 years old.</span>
<span class="attribution"><span class="source">Richard Bassed</span></span>
</figcaption>
</figure>
<h2>Ethical concerns</h2>
<p>There are also medico-ethical and legal considerations involved in conducting radiological procedures – with no defined medical need – on living people. </p>
<p>These are yet to be adequately addressed by the government. </p>
<p>Comprehensive age assessment of living individuals necessarily involves the use of ionising radiation – X-rays – with unavoidable radiation exposure. </p>
<p>While this exposure is not at a level sufficient to cause immediate harm, it does raise the total lifetime dose of radiation experienced by the individual. </p>
<p>Medical imaging is continually advancing, and development of methods such as ultrasound, MRI, and more focused low-dose CT technology may, in the future, resolve some of these issues. </p>
<p>Unfortunately, the most accurate assessment of a person’s age requires examination of internal skeletal and dental structures and that can’t be done without X-rays. </p>
<p>If age estimation were limited, as some have suggested, to an external physical examination, then the potential for gross error in either over or under estimating age would be great. </p>
<p>But we still need a considered debate about the risks and ethics associated with the use of X-rays for non-medical purposes versus the benefits of more accurate age assessments in the interests of justice.</p>
<h2>Better methodologies</h2>
<p>There are other available, proven methods for assessing age. These include physical examination by a suitably qualified medical practitioner, coupled with assessment of the degree of dental development and assessment of other skeletal elements such as the clavicle (collar bone), which has a far longer development time than the wrist, and can be used to assess age well into the 20s. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/1971/original/6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/1971/original/6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=599&fit=crop&dpr=1 600w, https://images.theconversation.com/files/1971/original/6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=599&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/1971/original/6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=599&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/1971/original/6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=752&fit=crop&dpr=1 754w, https://images.theconversation.com/files/1971/original/6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=752&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/1971/original/6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=752&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The clavicle or collar bone is a better measure of age.</span>
<span class="attribution"><span class="source">Richard Bassed</span></span>
</figcaption>
</figure>
<p>Still, <a href="http://www.sciencedirect.com/science/article/pii/S0379073809003703">many of these methods were developed from research conducted decades ago</a> and on populations which geographically, environmentally, and nutritionally do not accurately reflect current population demographics. </p>
<p>Some of these systems, especially those describing dental development, have proven to be quite adequate for people under 15 years of age and have served the profession well. </p>
<p>But <a href="http://www.ncbi.nlm.nih.gov/pubmed/20022437">recent research </a>suggests these older methods may not be as accurate as was once thought for young individuals, and it is suspected that they may be substantially more inaccurate for individuals older than 15 years of age. </p>
<p>In recent years, partly as a result of <a href="http://www.nap.edu/openbook.php?record_id=12589">a report into the state of forensic science in the United States</a>, there have been increasing calls for forensic science to improve the evidence basis for its conclusions. </p>
<p>For forensic anthropologists and odontologists, this includes improving age estimation methods, especially developing new reference standards for particular populations, and devising a more scientifically robust definition of the error and range in age estimations.</p>
<p>New research is now <a href="http://www.ncbi.nlm.nih.gov/pubmed/16182943">focusing on the development of multifactorial methods for age estimation</a>, whereby a combination of methods provides the age estimate with the smallest possible error. </p>
<p>Techniques able to provide age estimates at least twice as precise as any that have been previously used have been developed for older teenage individuals.</p>
<p>The <a href="http://www.springerlink.com/content/4h76841k36q73411/">development of the third molar, for instance, probably provides the best way to discriminate between an adult and a child</a>, and <a href="http://www.ncbi.nlm.nih.gov/pubmed/8454998">should be part of any age assessment procedure for late teenage individuals</a>.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/1969/original/3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/1969/original/3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=557&fit=crop&dpr=1 600w, https://images.theconversation.com/files/1969/original/3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=557&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/1969/original/3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=557&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/1969/original/3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=700&fit=crop&dpr=1 754w, https://images.theconversation.com/files/1969/original/3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=700&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/1969/original/3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=700&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Third molar development is the best way to distinguish an adult from a child.</span>
<span class="attribution"><span class="source">Richard Bassed</span></span>
</figcaption>
</figure>
<p>These new methods still have an inherent degree of error due to unavoidable development variability, but at least they are based on modern populations more closely resembling individuals who are most often targeted for age estimation. </p>
<p>And they are far more accurate than the outdated hand/wrist method currently in use, involve no greater radiation exposure, are based on modern population data, have a smaller error margin, and are just as simple to apply in practice.</p><img src="https://counter.theconversation.com/content/2049/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Richard Bassed does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>The current Australian Federal Police practice of using X-rays of the hand/wrist to assess the age of Indonesian crew members of boats bringing refugees to Australia is based on a method developed in the…Richard Bassed, Forensic dentist and doctoral student, Monash UniversityLicensed as Creative Commons – attribution, no derivatives.