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Re: leaded glasses
Some comments regarding Sandy's forwarded excerpts from MedPhysics.
I believe the acute threshold dose for cataract induction for beta/gamma/X-ray exposure to the lens of the eye is 200 rem (please correct me fellowradsafers if I am wrong). A few years ago there was an article published in the Health Physics journal noting that cumulative exposures to the lens of the eye greater than 800 rem had been linked to visual impairment (I don't remember exactly the type of impairment indicated in the article). I use the information in the tables below when giving training lectures to nurses, techs and physicians who participate in fluoro procedures. If any one is interested in the reference these numbers came from, please contact me via my e-mail address.
Est. Dose During 1 Catheterization Study
Cardiologist - 56 mrad
Radiographer - 2 mrad
Nurse - 23 mrad
Est. Dose During 1 Angioplasty
Cardiologist - 104 mrad
Radiographer - 5 mrad
Nurse - 52 mrad
Depending upon physician caseload and fluoro output and on-time, it may be possible that some physicians could come very close or possibly exceed 800 rad in a working lifetime. A nurse's lens of the eye exposure could be about half that of the physician. Each department (urology, cardiology, etc.) of course, will have different exposure potentials. Another Health Physics Journal article indicated that monthly exposures have been seen to vary from 0 to >2,500 mrem for badges worn at the collar level. Some fluoro units are not equipped with shielding to help reduce scatter radiation and scatter radiation can be significant. For example, some moble C-arm units can produce exposures of 100-200 mR/hour next to the patient and 10-20 mR/hour at the unit controls. Some cardiac cath bi-plane units can produce exposures of 200-300 mR/hour at tableside and 30-50 mR/hour at 1 meter. And beam-on time can be 20-30 minutes. So, in keeping with the ALARA philosophy, wearing leaded safety glasses can be viewed as good safety practice (especially if it helps reduce incident exposure to the lens of the eye by 50%). It is a recommendation that I make to fluoro staff during our training sessions.
At 03:04 PM 9/18/98 -0500, you wrote:
>Andy,
>
>Here are some excerpts I maintained from the MedPhysics
>Listserver, which addressed a question such as yours. Hope this
>helps a bit.
>---------------
>
>Post Number 1
>
>Interesting considerations. With regard to glasses, there was a
>paper in Medical Physics many years ago showing that they really
>do not reduce the dose to the eye much, perhaps 50%. This is
>due to the fact that the head provides significant backscatter to the
>eye. I would question if they are really cost effective, especially if
>one takes a look at the doses required for cataract production.
>----------------
>
>Post Number 2
>
>My recollection is that the "threshold" for cataract induction (over a
>"lifetime" of radiation) is approximately 5 Gy. (15 rem per year x
>30 years = only 450 rem; close but no cigar). And so, I will
>concede that if an individual stayed within the ALARA limits AND if
>radiation were the _only_ cataract-inducing agent to which the
>individual were subjected, there shouldn't be any problem.
>
>------------------
>Sandy Perle
>Technical Director
>ICN Dosimetry Division
>ICN Plaza
>3300 Hyland Avenue
>Costa Mesa, CA 92626
>Office: (800) 548-5100 x2306
>Fax: (714) 668-3149
>
>sandyfl@earthlink.net
>sperle@icnpharm.com
>
>ICN Dosimetry Website:
>http://www.dosimetry.com
>
>Personal Website:
>http://www.geocities.com/CapeCanaveral/1205
>
>"The object of opening the mind, as of opening
>the mouth, is to close it again on something solid"
> - G. K. Chesterton -
>
>The opinions expressed are solely, absolutely, positively, definitely those of the author, and NOT my employer
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