Digital x-ray machine

[jon.oman]

This week I had to get a couple of x-rays. I had assumed that film was still being used for large x-rays. It turns out that this is not the case. The x-ray tech used a holder that was about 14x17 inches in size. No film. I asked to see the holder, and she removed the dark slide. All I could see was a white surface. It appears to be a large digital senser of some sort. She did not know how it works. Can anyone shed some light on how this works? Could something like this be used in a studio?

[Nathan Potter]

Yes, these gadgets are becoming pervasive in the medical industry. The sensors are one of two complex solid state device types. Semiconducting selenium is a direct conversion material that can absorb an Xray photon producing a charge that is stored until read out. I think these are so far generally low resolution but good enough for general purposes, say 75 to 200 um pixels.

The indirect type (using Samsung as an example) employs a scintilator material that produces light from absorbing an xray photon then that light is detected by a semiconductor device Thin Film Transistor (TFT) or similar device that stores the charge, then is read out to a computer. Samsungs newer version of this is 3072 X 3072 pixels (9.4MP) over a nominally 46 X 46 cm. plate. When I view these images the resulting intrinsic Dmax is not great but of course the radiologist can do some pretty sophisticated enhancements by computer. Don't know the cost of these but I'm guessing that they are in the vicinity of that for a flat panel screen of that area with additional embedded costs for packaging so perhaps in the 2000 to 4000 dollar range for a 16 X 16 inch unit.

In discussions on this forum a few of us have alluded to the possibility that this technology could be a path to low cost Large Format image sensors. My two cents is that to achieve the required volume for a profitable business the photo image sensor version would need to ride along with other high volume applications in a flat panel fabrication facility that is flexible enough in process flow to enable several sensor types in the same line. Pixel size would also need to be reduced compared to what is now used for standard flat panels which is slightly greater than the eye resolution at standard reading distances. Volume is everything.

Nate Potter, Austin TX.

[jon.oman]

Thanks for the information Nate. Maybe we will have something similar in the studio, in the future.