Rare-earth screens do have some disadvantages: they're more expensive than hi-plus screens and the quantum mottle is greater. I'm won't define quantum mottle in this brief. If you want quantum mottle explained more accurately than most of us will need to know, see An Introduction to the Physics of Diagnostic Radiology by Edward Christensen, MD, Thomas Curry, MD, and James Dowdey, PhD.
In general, quantum mottle is seen only when intensifying screens are used at high kVp output. The result is film which appears slightly fuzzy, but does not significantly diminish their diagnostic quality. The life expectancy of hi-plus screens is three years, rather than five years for the rare-earth screens. However, with proper care, this may be extended.
The best way to care for screens is to keep them clean and store them upright, never flat. By keeping the screens clean, better quality films can be produced.
Screens are best cleaned with a solution containing an antistatic compound and a mild detergent. There are commercials screen cleaners available: warm water and a very mild soap can be used. The solution should be applied gently with a soft, lint-free cloth. Never rub vigorously; never use your fingernails or a sharp object to remove particles. To dry, place the cassette on its edge like an open book. Make sure it is thoroughly dried before reloading. Screens should be cleaned every two to three months unless it is a very busy office, then at least once a month. You may be amazed at the quality of your films if you just take some time to care for your screens.
Deborah Pate, DC, DACBR
San Diego, California
Note from Deborah Pate:
To the Readers of "DC" and the chiropractic community:
This note is regarding my last article in the June 18th issue, "Setting up a Technique Chart." I suggested using your CA in lieu of a phantom for determining technique factors. This is illegal and unethical. I have no excuses for this suggestion, it is a totally irresponsible statement and I will take full responsibility for may imprudent advise. I sincerely hope the readers of "DC" and other members of my profession will accept my apologies.
There is a penetrameter with a correction factor set up that comes with the Supertech, so that exposing a phantom or a person is not necessary to calculate factors. It is never necessary to expose anyone to radiation for the purpose of determining technique factors. I wish to retract this statement and apologize for even suggesting it.
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