Hackaday Prize Entry: A $100 CT Scanner

What do you do when you’re dad’s a veterinarian, dumped an old x-ray machine in your garage, and you’re looking for an entry for The Hackaday Prize? Build a CT scanner, of course. At least that’s [movax]’s story.

[movax]’s dad included a few other goodies with the x-ray machine in the garage. There were film cassettes that included scintillators. By pointing a camera at these x-ray to visible light converting sheets, [movax] can take digital pictures with x-rays. From there, it’s just building a device to spin around an object and a lot – a lot – of math.

Interestinly, this is not the first time a DIY CT scanner has graced the pages of Hackaday. [Peter Jansen] built a machine from a radiation check source, a CMOS image sensor, and a beautiful arrangement of laser cut plywood. This did not use a proper x-ray tube; instead, [Peter] was using the strongest legally available check source (barium 133). The scan time for vegetables and fruit was still measured in days or hours, and he moved on to build an MRI machine.

With a real source of x-rays, [movax]’s machine will do much better than anything the barium-based build could muster, and with the right code and image analysis, this could be used as a real, useful CT scanner.

The 2015 Hackaday Prize is sponsored by:

21 thoughts on “Hackaday Prize Entry: A $100 CT Scanner

  1. Once upon a time, a Brazilian guy found an old x-ray machine on garbage. He opened it and found a shiny dust. He distributed caesium chloride for people in his family, and some people ate it.

    Yes, we have the only case in history of ingestion of radioactive material. And it was caused by an x-ray out of inspection, so be careful with it!

    1. You are referring to the Goiânia accident, and it was a radiation therapy machine *not* an x-ray machine. A therapy machine uses radiation from an isotope to kill tumors.


      Cesium emits beta and gamma rays, of which beta is blocked by most things (but can give you burns). Gamma is penetrating and can be used to selectively kill tumor tissue.

      In contrast, X-rays are generated by accelerating electrons in a vacuum and slamming them into a tungsten target. It’s entirely an electronic process, the device contains no radioactive isotopes, and it’s generally safe to disassemble.

      He should take appropriate safety precautions when running the machine, but there’s no risk of radioactive contamination.

      None whatsoever.

      1. The only risk with a powered-down x-ray tube is if it has a beryllium window, which is toxic, though you only tend to get these on lower-energy tubes in things like x-ray spectrometers.
        It is unfortunate that the same hazard symbol is used for x-rays and radioisotopes considering how different the hazards are.

      2. X-rays can also be generated by peeling scotch tape off a roll under vacuum.

        True story. The electric discharge of the glue bonds breaking provides the accelerating voltage, and you can see the glow if you pull the tape in a dark room.

          1. You’re both ‘kinda correct.

            Scotch Tape X-rays peak around 15keV, but there is significant emission at higher energies. The 25keV emission is only a factor of 10 less than the peak.

            The veterinary-grade X-ray machine he’s using for the project is rated at 100kV, which also peaks at 25keV; meaning, the majority of photons generated by that machine have that energy (and tapers off with higher energies).

            And then when you add in exposure time and capture efficiency of the sensor, it turns out you *can* use scotch tape to take X-ray photos, for thin subjects such as fingers and hands. Twenty(ish) seconds of exposure for a hand.

            This link is an easy read, and is *really* interesting:


            The problem with scotch tape generation is collimation: the energy isn’t focused, so the images turn out fuzzy. Also it’s more difficult to keep the patient still over the longer exposure times.

            It’s not *entirely* clear whether this would be useful for poverty-stricken areas. The effect is easy to reproduce – another paper I’ve read mentions 120 mTorr vacuum, which isn’t terribly difficult for an amateur. Experimentation by a creative hacker might turn this into a cheap X-ray system suitable for hands and feet, maybe arms and legs.

            Easy to reproduce, potential for discovery/improvement, possibly world-changing… where have I heard that before?

            (I was researching X-rays as a potential method of igniting the reaction of my project.)

    2. That is nowhere near the only case in history of ingesting radioactive material. Google “radium girls.” Also google “nuclear fallout” and “Cher-fucking-nobyl.”

  2. Couple this with a 3D printer and the texture wrapping from the earlier post and how long will it be before someone makes a life size copy of themselves for next year’s April fools. (may take longer than a year to print)

  3. I starting to get annoyed at posts about “$100 “, but then down in the text, requires that you have access to some very specific resource, like an old x-ray machine or something of the like. I wouldn’t mind it too much if the headline was “$100 CT scanner, just add scintillator”. As it is now, it kind of implies that all I need is the $100 and I”m good to go…

      1. That’s the tube alone, you still need the mutliple-tens of kilovolts DC power supply…Also, the tube will probably need some kind of collimation filter…

  4. These pie-in-the-sky non-projects are really annoying. Anyone can claim that they’re going to build a ct-scanner for $100, but until they’ve got a working prototype, it’s nothing but an ego trip fantasy for them and a waste of time for the rest of us. Please print articles only if the submitter is able to demonstrate that they have actually accomplished something real.

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