The Use And Abuse Of CT Scanners

David Mills is as a research scientist at the cutting edge of medical imaging. His work doesn’t involve the scanners you might find yourself being thrust into in a hospital should you be unfortunate enough to injure yourself. He’s working with a higher grade of equipment, he pushes the boundaries of the art with much smaller, very high resolution CT scanners for research at a university dental school.

He’s also a friend of Hackaday and we were excited for his talk on interesting uses for CT scanners at EMF Camp this summer. David takes us into that world with history of these tools, a few examples of teeth and bone scans, and then delves into some of the more unusual applications to which his very specialist equipment has been applied. Join me after the break as we cover the lesser known ways to put x-ray technology to work.

CT Scanning Old Documents

What do acorns and CT scanners have to do with old documents? Printed records degrade over time and eventually, just the act of unfurling a scroll can spell doom for ancient artifacts. Left untouched, the information is still there and clever use of x-rays can read it.

Flythrough of a CT Scannned scroll via the Apocalypto Project

It turns out that fruits like acorns were the source material for the ink used on many historical documents. David uses a scan of an acorn colonised by parasitic gall wasps to illustrate how mineralisation in an acorn can be easily seen in a CT scan. The same should be possible with the mineralisation of inks in the documents.

The first tests of this technique were performed on a set of rolled-up parchment mediaeval manorial records from Norfolk, England. They were able to produce a readable virtual unrolling! After this breakthrough they were approached by a postal museum in the Netherlands with a set of 17th-century unopened letters, an ongoing project that presents a particular challenge due to contamination from both powdered seashells used by the authors to absorb surplus ink, and from lead in the wax seals used upon the envelopes.

The Salvation of Classic British Comedy

Earlier this year we covered the discovery and recovery of some very old, very rare, and very damaged film. That was some of David Mills’ work! It seems in the world of historical scanning that once you have a success, word gets around and you are besieged with interesting artifacts.

The BBC had some heavily degraded triacetate film stock containing a lost episode from the British comedy duo Eric Morecambe and Ernie Wise, and wanted to retrieve what they could from it. To say it was in awful condition is an understatement.

This type of film releases acetic acid as it decomposes, further accelerating damage to the film. As with the written scrolls, trying to unroll this film would destroy it. David’s team first used a laser cutter to segment the fused film reel into pieces small enough for the scanner. They have retrieved recognisable images from it, but there is still much work to do. In conjunction with a BBC team they are developing software to aid in the post processing to help remove distortion, and soon hope to revive one of those British traditions: a new Morecambe and Wise Christmas TV show.

Sometimes You Just Have to Have Some Fun

Of course like any of us, having access to rare and awesome tools leads to some fun side projects. David x-rays his lunch, and has competitions on social media to guess what he’s eating today. Wondering what an x-ray emitter looks like while running, they’ve scanned an iPhone with its camera rolling. The resulting video came complete with white spots from x-rays interfering with the camera. He also mentions imaging a non-functional pound shop USB hub that proved to have all ports wired in parallel and a black epoxy blob with no chip underneath. It seems a pound only goes so far.

Most of us will never encounter a CT scanner, but David’s talk gives us an entertaining and informative journey into this exciting field. Check it out, it’s a worthy way to spend half an hour.

22 thoughts on “The Use And Abuse Of CT Scanners

  1. ” Wondering what an x-ray emitter looks like while running, they’ve scanned an iPhone with its camera rolling.”

    That alone is interesting. The hazards of selfies. :-)

    If costs came down and married to a 3D printer interesting things could happen.

    1. Every time I’ve gotten a dental X-ray recently, I’ve held my phone up on the other side of my face, rolling a video the whole time. Haven’t been able to discern any speckles yet, but I think that’s a good thing!

      1. thx for clearing that up. it was very confusing, was reading it over and over and over again, just to wonder how the hell does the iphone emit xrays lol, that would have been a marvel of technology

  2. it is very nice to have these kind of medical imagine devices, but at the current state it can only detect some kind of a real bad news problems, for example few years back i had a crazy strong dizziness from one moment to the next, so they did a brain-scan but found no problem at all, all i had to do was to wait for a week or so and the dizziness was gone, no medicine, no procedure, no nothing, so what i’m saying is that we need more resolution with these scanning machines

    1. To increase spacial resolution (to see smaller things) while maintaining the same signal to noise ratio (to keep a reasonable contrast and low noise) you need you increase the x-ray intensity by 10^4.

      You run the risk of ablating the patient as you scan them.

  3. A friend from our makerspace has a daughter who recently graduated from med school. While she was a student she and one of her advisors gave him some CT scans of bony parts. He found that someone had written software to convert the format to stl files. He printed scale skulls, vertebrae, and such for the school. They were incredibly cool.

  4. Interesting how the lead content in the old letter seals caused all of those starburst-like artifacts. A number of years ago I worked on some experimental software to effect automatic bone cancellation for CT angiograms. One of the data sets I tried to process was from a person who had suffered a gunshot wound to the head (years prior). Fragments of lead from the bullet, still embedded in the bone, produced the same kinds of star bursts. This messed up my bone cancellation algorithm and was one issue I was never able to overcome.

    1. It’s a problem with simple back projection reconstruction algorithms, essentially there is missing data in those regions (too few x-rays made it through to be detected). The algorithm projects a lot of zeros over that region and the result is the star-burst like artefacts.

      There are more complicated reconstruction algorithms that can make a better stab at producing something useful in those regions, we don’t often need them, so we have not really invested much time in working with them. As I’m starting to image more objects that do exhibit these issues I’m going to be working on getting better reconstruction algorithms running.

  5. “Earlier this year we covered the discovery and recovery of some very old, very rare, and very damaged film.” the link points to the recent article on 3D printing, not the target article.

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