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A project log for Taking digital xray shots for cheap (< 300$)

Reverse engineering a Trophy DigiPan digital xray image sensor for 2D and CT 3D images.

Niklas FauthNiklas Fauth 02/26/2018 at 10:240 Comments

While for the test pattern only the 5V rail is required, for actual xray acquisition the DigiPan also needs +/- 15V. So the first step was to build a suitable power supply.



This laser-cutted box contains all what is necessary to operate the DigiPan:

The output of the ISO1176 is connected to one of the logic analyzer inputs. Also the 5V DigiPan power is connected to one input. This is not necessary however it allows to trigger sampling on rising edge of this power rail and thus to the test image sent out at power up, which makes testing way easier.


To slide the DigiPan during exposure we used a linear guide with a built in brushed motor. Speed control by controlling the motors voltage was sufficient at this point. Here is a video of the setup used to capture the first images:


https://twitter.com/FauthNiklas/status/964989555601559553


The xray device used for this is a modern handheld fluoroscope used for sports medicine. Output power is 40W at 20-80keV with a very narrow, well focused beam. You can recognize the spot size in the taken images:

The picture height represents the full sensor resolution of 1244 pixel. This is the xray of a BeagleBone Green. Two thinks you might notice:

The black horizontal line in the middle:

The DigiPan operates standalone, there is no way to start an exposure electrically. Also movement of the panel is a requirement of acquisition, but doesn't start one. The way this sensor triggers is that few pixels in the middle of the CCD are covered from the scintillator. If light level around these pixels rises, the sensor is exposed to xrays and image acquisition is triggered. 

The round spot:

As said before, the xray beam is very narrow. It is focused in a way no radiation sidepasses the original detector with 50mm diameter. This, combined with some lag caused by the detection of xray to trigger the acquisition, causes this weird, round shape with one side slightly cut of.

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