Fwd: Mini C-Arms

[Ccja@aol.com]

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Forwarded message:
From:	gaw@USA.NET (Jerry White)
Sender:	medphys@LISTS.WAYNE.EDU (Medical Physics Listserver)
Reply-to:	MEDPHYS@LISTS.WAYNE.EDU (Medical Physics Mailing List)
To:	MEDPHYS@LISTS.WAYNE.EDU (Multiple recipients of list MEDPHYS)
Date: 97-08-07 03:20:48 EDT

I hate to be contrary, but for at least some of the mini C-arms, lead 
aprons are not needed.  The typical Fluoroscan system (it has ~ 10 cm to 
cone face and 35 cm SID) has an itty-bitty II and very low tube current. 
The 1.9 cm Al phantom drives it to about 60 kVp and 70 uA, a typical 
hand or wrist would be even less.  Scatter measurements are about 2 
mR/hr at 50 cm from the II.  Staff other than the physician would need 
50 to 100 hours of fluoro time to hit even the 100 mR level.  The doc is 
a little closer, but still not in an area with significant exposure 
levels.  By contrast, a standard C-arm has about 10x that level of 
scatter/leakage.

The procedures often involve a fair amount of time putting tiny pins 
into fingers or wrists, the orthopods find the lead apron uncomfortable 
and a hindrance.  They have only short periods of fluoro to check 
position of the pins, a typical procedure could be 30 min of pin 
manipulation with 30 sec of fluoro.  The Apron is more trouble than it’s 
worth.  We badge these people and don’t see anything significant.

The new OEC mini C-arms are bigger, I don’t have the scatter data handy 
tonight on one of them, but the analysis is not a lot different.

Jerry White
gaw@usa.net