Re: mini-C-arms

[Ccja@aol.com]

Some of the states have exempted these devices from the requirement that
aprons be worn, and some have not. Some exempted them originally, then had
second thoughts and rescinded the exemption. My point is that I'd first
determine if it's a matter of basic regulatory compliance (as opposed to
ALARA compliance), where you are. If the state requires it, then your people
must be in aprons (unless you want to try for a variance, which would
probably be far more trouble than it'd be worth; no doubt it'd go over as a
lead balloon with the unions and your possibly pregnant nurses).
It may be true, as Joel implies, that few, or no, States did their own
testing of the units. It doesn't follow that the numbers they were given
weren't good. Our Dept of Health sent me a copy of an intercomparative
document, for the OEC6600 and Fluoroscan, written by a senior medical
physicist at a large university medical center. He used a modified ANSI
extremity phantom (it was cut down to 1/2 the standard length and width), at
70kVp/95uamp. He saw entrance exposure rates (without backscatter) of
380mR/min (HVL=2.7mm Al) and 404mR/min (HVL=3.0mm Al) for the two machines,
respectively. His measurements of the scattered radiation were not
significantly different at distances from 50 cm (5mR/h) to 20 cm (40 and 39
mR/h, respectively). At 10 cm the OEC rate was 140 mR/h and the Fluoroscan's
was 183.
I've heard anecdotes of beam-times as long as 90 minutes. Frankly, as in
interventional radiology, I worry about the surgeon's hands, as much as
anything. Has any had any luck getting them to wear ring badges?

chris alston
ccja@aol.com