x-ray homemade

Sigurthr · Apr 6, 2016

S_L is on the correct side of the issue here. We do not say 1mW lasers are safe to stare directly into because there are too many factors in play, even though they're several times below the threshold for damage. You don't really know the output of the unit until it is tested - first and foremost.

My DIY X-Ray unit puts out over 120R/hr (33mR/sec) of 45KeV photons. Yeah, at <5sec that's not too much to worry about for rare exposures. However, at 30sec you're talking about 1REM of exposure! That's plenty to cause a burn.

monkeydan · Apr 6, 2016

Just wonder what you are going to do with this thing?

Seoul_lasers · Apr 6, 2016

Sigurthr said:
S_L is on the correct side of the issue here. We do not say 1mW lasers are safe to stare directly into because there are too many factors in play, even though they're several times below the threshold for damage. You don't really know the output of the unit until it is tested - first and foremost.

My DIY X-Ray unit puts out over 120R/hr (33mR/sec) of 45KeV photons. Yeah, at <5sec that's not too much to worry about for rare exposures. However, at 30sec you're talking about 1REM of exposure! That's plenty to cause a burn.

Yes, thanks again for backup. I worry about people getting the wrong idea that these are safe and giving themselves an accidental burn by not having proper safety checks. Again, I can't stress enough... SAFETY first and foremost. :beer:
Good point Sigurthr, and excellent example about your tube emissions btw!!

Benm · Apr 7, 2016

REM is an obsolete unit, but it should equate to about 0.01 Sievert. 120 REM/hr sould be 1.2 Sv/hr which would be acutely dangerous if you were exposed for something in the order of an hour (not a few seconds).

I'm not entirely sure what happened in that fluoroscopy case, but those units used to put out a LOT of power before digital imaging became the norm. The skin damage you see is just the start of the problem. X-Rays do indeed penetrate tissues deeply, which is kind of the point as you want to make a decent amount of them come out the other end to produce the image.

Since there is no information on how long after exposure that picture was taken it's hard to estimate the dose, but if that damage is solely from x-rays it must have been a very high one. I'd actually reckon something in the order of 10 Sievert which would have been likely-fatal if the entire body were exposed to the radiation.

Question is if a dental x-ray head could do that to you. Answer is that it probably can if you keep your hand in the beam for several hours. But then again, why on earth would you? If you just want to take a photo of what the bones in your hand look like, a few seconds should be enough even with a crude fluorescent screen as the imaging converter.

I don't recommend you try this because of the long term risks, but your hand will not end up looking like the one in the photo if you do. It will if you do it 1000s of times shortly after eachother though.

Sigurthr · Apr 7, 2016

Yeah, I still use REM, can't help it; it's what I was taught ages ago. I guess it shows my age.

Re: fluoro dose incidents; even modern units can cause these types of accidents because many modern units have an automatic power adjustment mechanism which measures the xray flux exiting the target and adjusts intensity automatically to maintain image brightness. It can reduce total dose delivered if it is set up properly, but for example if it is not set up properly and a higher density or thickness target is used than expected it will actually worsen the dose in an effort to maintain brightness. Such an incident is taught to Rad Techs; a patient placed their arm in the beam path underneath the sterile cover, totally unnoticed by the techs. The beam target was on their side abdomen and the beam window was only 2"^2 or so. The bicep intercepted the beam path and the fluoro unit increased dose about 4x to compensate for the reduced transmission level. It wasn't discovered until the day after the procedure when an ulceration was discovered on the arm. It took multiple surgeries, skin grafts, and many months to close the wound. Much of the muscle was lost and the patient is permanently damaged. Techs are actually supposed to weigh the patients and take diameter measurements to work out a necessary xray hardness and dose rate BEFORE the first exposure. However, in the interest of speed, most imaging locations have opted to forgo this precaution and instead take a blind exposure at an assumed safe level and then make adjustments from there.

Btw, regarding dental xray heads; One of the dangers is improper intrinsic shielding. There's a few news articles about inexpensive portable units being sold in the east which are largely made of plastic and have insufficient shielding. Dose rates delivered to the doctors holding the portable units exceeded dose rates delivered to the patient. I don't think this is applicable here, but it is something to note when not remotely operating the unit. The other major danger is when someone repurposes a head and does not use an OEM controller. It has been reported that users were unaware the unit was ON until much time passed, resulting in large accumulated doses. Most small heads can run unlimited duty cycle, and have no visible indication that they are running.

Seoul_lasers · Apr 7, 2016

Sigurthr said:
Yeah, I still use REM, can't help it; it's what I was taught ages ago. I guess it shows my age.

Re: fluoro dose incidents; even modern units can cause these types of accidents because many modern units have an automatic power adjustment mechanism which measures the xray flux exiting the target and adjusts intensity automatically to maintain image brightness. It can reduce total dose delivered if it is set up properly, but for example if it is not set up properly and a higher density or thickness target is used than expected it will actually worsen the dose in an effort to maintain brightness. Such an incident is taught to Rad Techs; a patient placed their arm in the beam path underneath the sterile cover, totally unnoticed by the techs. The beam target was on their side abdomen and the beam window was only 2"^2 or so. The bicep intercepted the beam path and the fluoro unit increased dose about 4x to compensate for the reduced transmission level. It wasn't discovered until the day after the procedure when an ulceration was discovered on the arm. It took multiple surgeries, skin grafts, and many months to close the wound. Much of the muscle was lost and the patient is permanently damaged. Techs are actually supposed to weigh the patients and take diameter measurements to work out a necessary xray hardness and dose rate BEFORE the first exposure. However, in the interest of speed, most imaging locations have opted to forgo this precaution and instead take a blind exposure at an assumed safe level and then make adjustments from there.

Btw, regarding dental xray heads; One of the dangers is improper intrinsic shielding. There's a few news articles about inexpensive portable units being sold in the east which are largely made of plastic and have insufficient shielding. Dose rates delivered to the doctors holding the portable units exceeded dose rates delivered to the patient. I don't think this is applicable here, but it is something to note when not remotely operating the unit. The other major danger is when someone repurposes a head and does not use an OEM controller. It has been reported that users were unaware the unit was ON until much time passed, resulting in large accumulated doses. Most small heads can run unlimited duty cycle, and have no visible indication that they are running.

The problem you highlighted is exactly what went wrong to the poor fellow in the picture I posted.
The burn in question I believe caused the patient to loose several of his fingers as the damage to the cells also included bone tissue. Nasty!!

This wasn't a very long exposure either. :thinking:
That's why I am encouraging (strongly) safety with X-ray tubes.

Benm · Apr 8, 2016

For the internal shielding: that is where your geiger counter may actually be useful - it will blare away meaninglessly in the beam path, but if you stand behind the x-ray emitter it should not pick up that much radiation, and hopefully give a usable figure of how much.

The 'how much' part is rather important. The upper exposure limit for radiological workers is 50 mSv/YEAR in the US, and 20 mSv in most of europe. So if your meter is indicating something like 10 uSv/hour you could remain under those conditions for 5000 hours every year. Given normal working hours this would be an acceptable environment to work in, though not desirable.

And to give an order of magnitude: actually having dental x-rays taken exposes you to only 10 uSv a time, but remember how fast those things go - done in a second! I'm not sure if there are power controls beyond what you currently have in dental applications though, so it could be outputting more than normal.

Benm · Apr 9, 2016

Nice results!

I see you're getting a fair number of hot pixels on the photos though - is that just background radiation hitting the scintillator or cause by something else?

Sigurthr · Apr 9, 2016

Very, very nice results! I'm surprised that camera performed so well.

The hot pixels are because he's doing direct beam path imaging. If he used a mirror at 45-degrees to reflect the image 90-degrees off axis this will be eliminated, but it's often more trouble than worth unless the problem is severe. His images look really good though and he's able to use a very short exposure time too. My exposures are typically between 5sec and 30sec, but the camera I use has a very high density glass lens and steel casing so it can be direct beam path with very little hot pixels.

Given that the exposure is "only" 35R/hr and his exposures are <5sec I'd say he's operating relatively safely - well done!

Benm · Apr 10, 2016

I suppose the camera lens system helps to keep those hot pixels appearing if it is of decent size and composition. A couple of centimeters of glass could actually be a decent x-ray shield depending on the type of glass.

In these shots it certainly is not annoying to watch, although i wonder if it could do permanent harm to the sensor over time. If you are holding the camera and see hot pixels popping up like that it's probably best to make your way out, but if it's on a remote tripod... well, let's see how it fares

Seoul_lasers · Apr 12, 2016

Benm said:
I suppose the camera lens system helps to keep those hot pixels appearing if it is of decent size and composition. A couple of centimeters of glass could actually be a decent x-ray shield depending on the type of glass.

In these shots it certainly is not annoying to watch, although i wonder if it could do permanent harm to the sensor over time. If you are holding the camera and see hot pixels popping up like that it's probably best to make your way out, but if it's on a remote tripod... well, let's see how it fares

***Most certainly X-rays will cause permanent damage to the image sensor if it there is a direct strike to the sensors surface.
Definitely take precautions to shield the sensor from the radiation via Pb glass or multiple layers.

Hot pixels are a sign of intense charge saturation at the pixel site. If they stay on the image after you've turned off the x-ray you have damaged the sensor.

Benm · Apr 13, 2016

Any idea on what determines if the damage is permanent?

It's fairly obvious that things like x-ray/gamma but also beta radiation cause hot pixels in images and videos, but often they are not permanent and the affected pixels continue to work as usual when taking pictures away from radiation afterwards.

I'm a bit hesitant to call this one: people travel with digital cameras through airport security all the time, and these units get exposed to many such screenings when you do a lot of travel. I've never heard of someone certainly getting hot or dead pixels due to x-ray security screening.

Perhaps it makes a difference that the device is usually off when screened, but then again i'm not sure why -that- would make a difference either.

Sigurthr · Apr 13, 2016

There should be no permanent pixel damage. People have put GoPros through electron beam irradiators (at thousands of R/hr) and had no damage.

Benm · Apr 14, 2016

Guess the airport screening stuff won't put a dent in it then.

I'm flying next week, guess it might be nice to actually leave the phone cam recording as it goes through the scanner - i wonder if that will produce any visible hot pixels. I don't really care if the camera in that gets a damaged pixel or two.

Would it be dangerous to a camera to leave it on long exposure when going though, like just setting it to a minute or bulb mode with a lens cover on?

Sigurthr · Apr 15, 2016

That should work fine, Benm. There are a few *really inaccurate* faux geiger-mueller apps for smartphones which do just this; relying on hot pixels to detect incident ionizing radiation.

Also, I've blasted my iphone with 120R/hr for over 1min continuous while doing radiography. No damage or errors what-so-ever.

Benm · Apr 16, 2016

That's good to hear. I doubt a smartphone camera could be of any use to quantify radiation unless it had a scintillator in front of it, and even then i have my doubts on it detecting radiation levels below 'run for your life' reliably.

I'll try to put my phone through the scanner while recording video - perhaps something interesting will pop up.

Afaik the carry on luggage scanners don't put out that much energy, but the ones used to inspect checked bagage do. I'm not sure if i have anything that i can check in whilst keeping recording for the duration of a flight though. I'm sure it will last long enough to capture the xray on departure, but not too sure it will save the video properly when the batteries die sometime after before i can press 'stop'.

x-ray homemade

Sigurthr

0

monkeydan

0

Seoul_lasers

0

Benm

0

Sigurthr

0

Seoul_lasers

0

Benm

0

Benm

0

Sigurthr

0

Benm

0

Seoul_lasers

0

Benm

0

Sigurthr

0

Benm

0

Sigurthr

0

Benm

0

Online statistics

Forum statistics

Share this page