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Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
James wrote ...
Get some lead sheet, 1mm thick should be plenty adequate for 50 kVp x-rays.
If we take operating conditions Va 50 kV, Ia 4 mA, filter Al 1mm, the dose rate at a distance of 50 cm will be 5 - 6 Gy/hr depending on beam geometry etc.
The addition of Pb shielding 1 mm will reduce the dose rate at 50 cm to roughly 50 mGy/hr - an unaccceptably high figure.
Registered Member #33
Joined: Sat Feb 04 2006, 01:31PM
Location: Norway
Posts: 971
I don't think the MacGyver method will work very well. X-ray developer and fixer should work just fine for developing photographic paper, as both x-ray film and photographic paper are based on the same chemistry.
Edit: I did some googling, and it turns out developing with orange juice is actually possible, and coffe supposedly works even better. It's doesn't work nearly as well as proper developer, of course, but it's actually possible.
Photographic paper is going to have a very low ISO, so it's not practical for direct exposures with a dental x-ray machine (or with a 2X2), you need an intensifying screen unless you want an exposure time of many hours. Ideally you would want blue-emitting x-ray screens, as I don't think photographic paper is sensitized to green light.
Proud Mary wrote ...
James wrote ...
Get some lead sheet, 1mm thick should be plenty adequate for 50 kVp x-rays.
If we take operating conditions Va 50 kV, Ia 4 mA, filter Al 1mm, the dose rate at a distance of 50 cm will be 5 - 6 Gy/hr depending on beam geometry etc.
The addition of Pb shielding 1 mm will reduce the dose rate at 50 cm to roughly 50 mGy/hr - an unaccceptably high figure.
Where are these figures from? They sound unrealistically high.
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
Anders M. wrote ...
I don't think the MacGyver method will work very well. X-ray developer and fixer should work just fine for developing photographic paper, as both x-ray film and photographic paper are based on the same chemistry.
Photographic paper is going to have a very low ISO, so it's not practical for direct exposures with a dental x-ray machine (or with a 2X2), you need an intensifying screen unless you want an exposure time of many hours. Ideally you would want blue-emitting x-ray screens, as I don't think photographic paper is sensitized to green light.
Proud Mary wrote ...
James wrote ...
Get some lead sheet, 1mm thick should be plenty adequate for 50 kVp x-rays.
If we take operating conditions Va 50 kV, Ia 4 mA, filter Al 1mm, the dose rate at a distance of 50 cm will be 5 - 6 Gy/hr depending on beam geometry etc.
The addition of Pb shielding 1 mm will reduce the dose rate at 50 cm to roughly 50 mGy/hr - an unaccceptably high figure.
Where are these figures from? They sound unrealistically high.
I used RadPro, Anders and then verified its estimate against other sources. As you know, estimates of this kind are never going to be especially accurate, and are designed to err on the side of caution, but they serve very well to give an idea of the order of hazards involved.
Registered Member #33
Joined: Sat Feb 04 2006, 01:31PM
Location: Norway
Posts: 971
Proud Mary wrote ...
Anders M. wrote ...
I don't think the MacGyver method will work very well. X-ray developer and fixer should work just fine for developing photographic paper, as both x-ray film and photographic paper are based on the same chemistry.
Photographic paper is going to have a very low ISO, so it's not practical for direct exposures with a dental x-ray machine (or with a 2X2), you need an intensifying screen unless you want an exposure time of many hours. Ideally you would want blue-emitting x-ray screens, as I don't think photographic paper is sensitized to green light.
Proud Mary wrote ...
James wrote ...
Get some lead sheet, 1mm thick should be plenty adequate for 50 kVp x-rays.
If we take operating conditions Va 50 kV, Ia 4 mA, filter Al 1mm, the dose rate at a distance of 50 cm will be 5 - 6 Gy/hr depending on beam geometry etc.
The addition of Pb shielding 1 mm will reduce the dose rate at 50 cm to roughly 50 mGy/hr - an unaccceptably high figure.
Where are these figures from? They sound unrealistically high.
I used RadPro, Anders and then verified its estimate against other sources. As you know, estimates of this kind are never going to be especially accurate, and are designed to err on the side of caution, but they serve very well to give an idea of the order of hazards involved.
Your numbers suggest that the radiation from an x-ray tube operating at 50kV is attenuated two orders of magnitude by 1mm of lead, but this graph that you posted earlier states that even half a millimeter of lead will attenuate the x-rays by five orders of magnitude.
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
Anders M. wrote ...
Your numbers suggest that the radiation from an x-ray tube operating at 50kV is attenuated two orders of magnitude by 1mm of lead, but this graph that you posted earlier states that even half a millimeter of lead will attenuate the x-rays by five orders of magnitude.
I don't see any contradiction here. The figures in the graph are derived from probablistic energy-dependent half-values without reference to fluence, whilst the figures I have proposed are for dose rates in Gy/hr 50 cm from the anode at beam cone centre.
Registered Member #33
Joined: Sat Feb 04 2006, 01:31PM
Location: Norway
Posts: 971
What is the practical difference between those two figures, why is there such a large difference between them, and why are the numbers from RadPro more applicable? I'm just trying to learn more about this, and this seems a bit counterintuitive to me.
Registered Member #1412
Joined: Thu Mar 27 2008, 04:07PM
Location: Taipei Taiwan
Posts: 278
I test MacGyver's method.But I use some overdue vitamin pills and ammonia.It works but ofcourse very low quality.(not with X-ray,With ordinary negative film)
This is the very first time I develop photo.
But my dad was VERY VERY angry about the smell of ammonia.
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
Anders M. wrote ...
What is the practical difference between those two figures, why is there such a large difference between them, and why are the numbers from RadPro more applicable? I'm just trying to learn more about this, and this seems a bit counterintuitive to me.
Here is a paper by Ray McGinnis, designer of RadPro, on some of the assumptions he used in the calculator design:
Registered Member #33
Joined: Sat Feb 04 2006, 01:31PM
Location: Norway
Posts: 971
Yes, I've seen reports of people using NaCO3 together with orange juice, so this should work fine. Here is some more info about developing film with coffee.
Photographic paper is sensitive to x-rays, but it's less sensitive to x-rays (and light) than film, because paper usually has a much lower ISO rating (5-25 according to some forum posts I found) than film (100-3000 usually).
Proud Mary wrote ...
Anders M. wrote ...
What is the practical difference between those two figures, why is there such a large difference between them, and why are the numbers from RadPro more applicable? I'm just trying to learn more about this, and this seems a bit counterintuitive to me.
Here is a paper by Ray McGinnis, designer of RadPro, on some of the assumptions he used in the calculator design:
Shielding Equations and Buildup Factors Explained
I would think that the numbers from the NIST graph would me more applicable in this case, as these are the guidlines used for x-ray shielding in practice. The numbers from RadPro are based on theoretical calculations with a lot of unrealistic assumptions. To quote from the RadPro website: "It should always overestimate the amount of shielding required because e-max for the tube head is used when in reality the device produces an entire energy spectrum from lower energies up to e-max.". I think overestimate is a mild word in this case, as assuming all of the energy is at e-max is quite a bold assumption.
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Homemade X-ray machine question
