[ RadSafe ] Gamma detector proves less invasive, more accurate for seed migra tion

[John Jacobus]

Since the scintillation scannning method seems to be
superior in reducing the false-negative detection of
seeds, I would think that it is superior to x-ray or
fluoro.  It would nice to see some estimate of
additional radiation doses using those modalities.

Sounds like they scanned the patients with a thin NaI
probe with a lead collimator, then took a x-ray film
for documentation.  

--- Roy.Herren at med.va.gov wrote:

> The following article appeared today on
> AuntMinnie.com.  I would appreciate
> your thoughts, and feedback on this issue.
> 
> Any opinions in this e-mail are solely those of the
> author, and are not
> represented as those of the VA Medical Center San
> Francisco, CA, the Dept.
> of Veterans Affairs, or the US Government.
> 
> Roy Herren
> Physical Science Technician
> Radiation Safety Branch of the Radiology Department
> Veterans Affairs Medical Center San Francisco, CA
>
===================================================================
> 
> Gamma detector proves less invasive, more accurate
> for seed migration
> 6/15/2005
> By: Shalmali Pal
> 
> 
>  
> 
> Now that scintillator-based detectors are on the
> scene, x-rays should be
> jettisoned for assessing embolized seed migration in
> the lungs, according to
> radiation oncologists in Canada.
> 
> "The seed-migration detector appears to be
> convenient, cost-effective and
> noninvasive ... (and) doesn't expose patients to any
> additional radiation,"
> wrote Dr. Janelle Morrier and colleagues in a poster
> presentation at the
> 2005 American Brachytherapy Society (ABS) meeting in
> San Francisco.
> 
> For this study, 155 patients (8,717 seeds) at Laval
> University in Quebec
> were scanned for seed migration in a one-year
> period. The detector was
> composed of a gamma scintillation probe and a count
> rate meter. An in-house
> collimation cap was added to the detection window of
> the probe, the authors
> said. Detector response profiles were first taken
> with and without the
> collimator using an iodine-125 seed and a water
> phantom.
> 
> The results showed a seed migration rate of 0.47%,
> or 41 out of 8,717 seeds.
> Twenty-one percent of the patients had at least one
> embolized seed. The
> migration detector found all of the dislodged seeds
> versus radiographs,
> which found 68%, and fluoroscopy, which found 90%.
> Four seeds were found
> with the detector but were not seen with either
> imaging modality, the
> authors stated.
> 
> Seed migration based on fluoroscopy alone would have
> led to a 12.1%
> false-negative rate; with x-ray alone, the
> false-negative rate would have
> been 39.4%.
> 
> "Moreover, fluoroscopy and radiographs would have
> required ... an extra
> radiation dose," they wrote. "The recommendation to
> perform chest
> radiographs to scan the lung for embolized seeds
> should be revised as the
> scintillator-based seed-migration detection presents
> a superior efficacy and
> a lower false-negative rate." The researchers also
> suggested that x-ray be
> reserved for documentation of positive migration
> cases. 
> 
> By Shalmali Pal
> AuntMinnie.com staff writer
> June 15, 2005

+++++++++++++++++++
"Every now and then a man's mind is stretched by a new idea and never shrinks back to its original proportion." -- Oliver Wendell Holmes, Jr.

-- John
John Jacobus, MS
Certified Health Physicist
e-mail:  crispy_bird at yahoo.com


		
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