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X-ray general
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You are currently reading a thread in /p/ - Photography

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Thinking of getting my own tube after having a play with a dental unit.

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>>2763739
have fun with cancer
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>>2763744
Nothing a few lead blocks, a good dosimeter and good old inverse square won't solve. The only real danger if it's fired straight down is backscatter.
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>>2763739
I've always wondered - in modern xray machines giving digital files as output - what's the sensor? It used to be xray film and that makes sense for xrays of large body parts - it has to be large. Do they really make ccd-like sensors the size of a human chest nowadays?
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>>2763754
They do. It's usually a scintillating medium (converts ionising radiation to visible light photons) coupled to a scintillating plate (lead with a shit ton of parallel holes drilled in it, since there aren't X-ray lenses) because direct exposure of the CCDs to X-rays would fuck them up beyond belief.

They're unbelievably expensive and fat fucks break them.
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>>2763757
Interesting, I'd wondered about this too.

I haven't had an X-Ray in a while, but last time I did, in maybe 2011 or so, they shot it on film but then fed it into some crazy contraption that developed and scanned it all in one big box and it spit it out as a digital file in addition to the film plate.
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>>2763759
It's still a lot cheaper for low volume places to use film. You have to pretty much use a fully digital X-ray machine constantly to justify the price, especially if the films are relatively small, such as in a dental surgery.
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>>2763757
So effectively, without the scintillating medium/plate layers they really are fucking large format black&white CCD sensors, holy fug.
What resolutions are we talking about here? (i.e. what res are the output image files - I'll be guessing smaller sensors have higher resolution, larger ones don't have to resolve as much since for detailed imaging you're sent to a CT or MRI scan anyway.)
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>>2763807
More or less. Resolution and bit depth massively depends on the unit, for example, this unit is 6.6 megapixels
http://www.fujifilm.com/products/medical/digital_radiography/fdr_devo_ii_g35

They'll also turn down the resolution (i.e. averaging multiple pixels) to get better sensitivity and therefore be able to reduce the dose as required as well do other things with how each pixel is read, similar to ISO.

A CT scanner is actually simpler, it's just a 2D sensor (like on a conventional scanner) which takes a continuous reading as it spirals (or does a series of circular passes) around your body. The computer then does some fancy processing which I can't even begin to understand to build up a 2D slice, these are combined to get a 3D output. MRIs are even more complex, they fire off a magnetic pulse which energises water molecules in your body, then they record the radio waves emitted and an even more cunning bit of processing converts these signals to a 2D slice.
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>>2763829
How is a CT scanner simpler? It's still an x-ray machine.
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>>2763871
In terms of the sensor. It's only a 1D (typo in the last post) sensor. On the other hand, it has to spin at several hundred RPM:
https://www.youtube.com/watch?v=cjtHNxf01tQ
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>>2763877
These things fucking blow my mind. The fact that they can spin something that big that fast, keep it balanced, and maintain complicated electronic connections while doing it is insane.
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