Wipe Tests in Nuclear Medicine

[lambert@HAL.HAHNEMANN.EDU]

I have been asked to recommend appropriate instrumentation for performing 
package (and room wipes) in our nuclear cardiology department.  I want 
to poll RSO's at medical institutions to see what type of instrumentation 
is used for this purpose at their facility.

We have examined a thin (end) window GM and rate meter with (as expected)
unsatisfactory results.  I have considered a scaler retrofit to the
ratemeter, but this would not solve the inherent inefficiency of the GM
detector.  We also looked at a 1" x 1 mm NaI(Tl) scintillation crystal
with rate meter with better but with borderline results.  In both 
situations, we have kept geometry constant using a planchette tray. 

I am considering these options:

  o  Scaler (such as Ludlum model 1000) with shielded NaI well detector.
  o  Scaler/SCA (such as Ludlum model 2200) with shielded NaI well detector.
  o  Capintech CAPRAC-R Well / Wipe Counter
  o  Capintech CAPRAC Wipe Test / Well Counter
  o  Biodex Atomlab 50 Wipe Test Counter
  o  Victoreen Deluxe Wipe Test Counter

Does anyone out there have any experience with these devices for 
measuring Tc-99m (and some Tl-201)?

Can anyone explain how the Victoreen actually works?  The literature says
it is a thin window GM with an efficiency of 0.3%.  Since the reporting
level on package wipes is 2200 dpm / 100 sq cm., the LLD has to be less
than 6 cpm (2000 dpm * 0.003 cpm/dpm).  I find it hard to believe that the
background would be low enough to measure this in a nuclear cardiology hot
lab (even behind lead bricks).  Does anyone have any experience with this
device, or am I missing something? 

Thanks, 

Kent Lambert
LAMBERT@hal.hahnemann.edu

All questions have been thoughtfully
considered and well researched, the 
answers on the other hand have not.
My opinions remain unendorsed.