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The dangers of Xray units?

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hak8or

Tue May 01 2012, 08:06PM

Registered Member #2025 Joined: Fri Mar 13 2009, 05:39PM
Location:
Posts: 16

Hello 4hv! I normally lurk here, but I decided to actually post for once.

I took apart an xray machine, used to measure bone density, and I would like to ask before I go further with taking it apart. Is there anything I should know about, for safety sake, when I am taking it apart? I am mainly concerned with the Xray sensor under the finger, as it seems to be sealed very tightly, with the use of screws and even glue, or is it just sealed to have an airtight environment keeping out dust? I would also like to take apart the xray head but it seems to be incredibly well sealed, which leads me to believe that it might be sealed like that for good reason, any ideas on if there may be anything of risk to us humans inside it? Also, feel free to ask for my pictures if needed, I will happily oblige. :)

Here are my current teardown pictures: Teardown Forum I posted this in

I am sorry if this is in the wrong section of the forum, I don't know if it should go in this section, Projects, or General Chatting.

Steve Conner

Wed May 02 2012, 08:10AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Looks like a very interesting dumpster find!

The X-ray head is probably lined with lead for radiation shielding, and filled with dielectric oil. Lead is mildly poisonous, so don't go hacksawing it and eating the metal filings.

More importantly, don't tear it apart if you think you might want to use it later.

It is sealed to prevent the oil from leaking out and making a mess, and also to stop moisture getting into the oil.

The sensor is probably glued firmly shut to ensure that no stray light can get in. It is probably made from a CMOS or CCD camera chip with a piece of fluorescent screen stuck to it to increase sensitivity. And obviously this combination is very sensitive to visible light as well as X-rays.

If it was me, I'd have wanted to get it working before tearing it apart. Or better still, hack into the computer section to access the raw image data.

hak8or

Wed May 02 2012, 05:13PM

Registered Member #2025 Joined: Fri Mar 13 2009, 05:39PM
Location:
Posts: 16

Thank you so much for help! :)

I was thinking that it was sealed like that because the oil was going under the surface metal, but now I know that I am right by your confirmation. I presume the oil function is for cooling the xray anode plate, and also as an insulator for the very high voltage transformer and wiring?

For some reason it did not pop into my head at all that it could just be using a fluorescent screen and behind that a normal cmos or ccd image sensor, kind of bummed that it was not something more exciting. :P

I am just curious though, do new dental xray machines have a sensor that directly receives the xrays and generates an image, or do we still use a fluorescent screen with just a higher resolution CCD/CMOS image sensor?

Lastly, I was too excited to just get it to work first, I really wanted to look inside, heh. Since taking apart the xray head seems like an extremely messy process, not to mention I have no idea how to even begin to disassemble it without letting some lead fly, I will leave it alone and instead focus on finding out the software side of things. I don't know enough about Xrays or any electromagnetic radiation to feel that I can safely mess with this guy turned on and disassembled, so I will stick with software for now. :P

Again, thanks a bunch for your help! :)

Proud Mary

Wed May 02 2012, 07:13PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

hak8or wrote ...

I am just curious though, do new dental xray machines have a sensor that directly receives the xrays and generates an image, or do we still use a fluorescent screen with just a higher resolution CCD/CMOS image sensor?

Google digital dental imaging

sparky99

Tue Jul 10 2012, 05:01AM

Registered Member #1159 Joined: Fri Dec 07 2007, 02:10AM
Location: Hudson Valley of NY State
Posts: 84

My guess is that inside the X-ray head is a Blumlein HV generator feeding a cold cathode x-ray tube. The cold cathode tube may not be in oil, but the blumlein generator definately will be. I had a few portable x-ray machines made by Golden engineering and still have the Blumlein generator from one. Let me know if you want to see pictures.

Sparky99

Wolfram

Tue Jul 10 2012, 06:47AM

Registered Member #33 Joined: Sat Feb 04 2006, 01:31PM
Location: Norway
Posts: 971

This is a continous unit, so it won't have the blumlein generator. Most likely would be a ferrite step-up transformer feeding a three or four stage voltage multiplier. This is the most common configuration for high-frequency x-ray heads.

I wouldn't dismantle the x-ray head if you plan on making x-rays. It tends to be a bit messy and since you already have the driver electronics there should be no need to do so.

Also, I don't think you should dismantle the sensor, the scintillator (Gd2O2S:Tb or possibly CsI:Tl) is probably deposited directly on the sensor chip. Large scintillation screens can be had cheaply on eBay in the form of intensifying screens from x-ray cassettes.

I think modern dental x-ray sensors can be either CCD or CMOS-based, and the scintillator can be either Gd2O2S:Tb or CsI:Tl. Older sensors were often based on CID imaging chips as they were less affected by radiation than CCD and CMOS, but advances in image sensor technology has made them redundant.

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