Improving A Homebrew CT Scanner With Barium


[Peter] has been working on his homebrew CT scanner for a while, and it’s finally become something more than a spinning torus of plywood. He’s managed to image the inside of a few pieces of produce using an off-the-shelf radiation detector and a radioactive barium source

When we last saw [Peter]’s CT scanner, he had finished the mechanical and electronic part of the Stargate-like device, but the radioactive source was still out of reach. He had initially planned on using either cadmium 109 or barium 133. Both of these presented a few problems for the CT scanner.

The sensor [Peter] is a silicon photodiode high energy particle detector from Radiation Watch this detector was calibrated for cesium with a detection threshold of around 80keV. This just wasn’t sensitive enough to detect 22keV emissions from Cd109, but a small add-on board to the sensor can recalibrate the threshold of the sensor down to the noise floor.

Still, cadmium 109 just wasn’t giving [Peter] the results he wanted, resulting in a switch to barium 133. This was a much hotter source (but still negligible in the grand scheme of radioactivity) that allowed for a much better signal to noise ratio and shorter scans.

With a good source, [Peter] started to acquire some data on the internals of some fruit around his house. It’s still a slow process with very low resolution – the avocado in the pic above has 5mm resolution with an acquisition time of over an hour – but the whole thing works, imaging the internal structure of a bell pepper surprisingly well.

22 thoughts on “Improving A Homebrew CT Scanner With Barium

  1. Beware the viagra-laced hidden div on the top of the site… Looks like his site was hacked.
    If you visit it with the NoScript extension or something like that, you are safe…
    Other than that, nice build! I liked the build mode (avoid hot-glue!) used.

  2. Weird use for the barium. Barium (barium sulfate suspension more specifically) is usually a contrast material. It’s basically metal suspended in liquid. Being metal, it absorbs (like lead) X-Rays to a certain degree, so you get contrast in your images. (coats your GI Tract–nastiest thing you’ll ever drink)

    Also, CT is basically multiple X-Ray imagines computed axially into 3D images. (hence CaT being acronym for Computed Axial Tomography) This project sounds more like atomic imaging. (aka nuclear med) That’s when they inject a radioactive isotope into your blood stream and then take imaging of the radiation you give off. But that’s usually not 3D that I can remember, so it sounds more like MRI, only detecting radiation over RF.

    Cool project.

    1. Some corrections:

      He’s using a barium isotope- has nothing to do with barium as a contrast agent.

      The barium emits gamma rays which means this is gamma imaging. Has nothing to do with MRI.

  3. Interesting, as I am working on improving the sensitivity of my existing counters.

    Its worth noting that the commercial X-ray imaging systems use collimators, which are parallel bars in layers stacked up so off axis X-rays are deflected and not counted.
    A crude variant can be made from Veroboard electroplated with lead or so I heard :-)

    1. Really?

      A ~1 tesla magnetic field is “easier to make” than a tiny radioactive source that you can order on the web.

      Superconducting magnets, liquid helium temperatures, etc. etc.


  4. Have you considered using super-resolution to improve the image? The process involves taking many images while moving the imager slightly, and merging the resulting images using clever mathematics.

  5. Re. tubes, yes you can indeed.
    Re. images, the resolution may be poor but it is still better than anything I’ve seen on such a minimal budget.
    For comparative purposes, a cheap X-ray dental unit head (just the head, no HVPSU) is over £9000 and 80% of that is in the certification needed to legally sell it to a medical practitioner.

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