Re: RE: CORRECTED INFO RE GAMMAMED HDR UNITS

[James Myers <JHM@nrc.gov>]

Ron,

This is a very simple, I hope, explanation.  (If not, I'm sure I'll hear about it!)

The high dose rate afterloaders (HRDs) are used to treat cancer.  There are several manufacturers and there has been a couple design variations over the years.   Essentially, they store the radioactive source in a "safe" within the machine.   Catheters are placed into the tumor according to a treatment plan and are connected to the afterloader by guide tubes.  The afterloader's computer pushes a source, usually about 10 Ci of Ir-192,  on a drive cable through the guide tube and into the pre-placed catheters and retracts the source when the treatment plan is completed.   Some HDRs can cycle the source between several catheters during a single treatment.  A single treatment takes only a short time due to the high dose rate from the source.   Usually the treatment is delivered in "fractions" over several days.  

Advantanges over the old "manual" brachytherapy technique.   

High dose rate delivered in fractions directly to the tumor (or very close to it).
Fast treatment time 
Precise dose delivery and execution of the treatment plan
Higher patient throughput due to decreased treatment time
Mobility....small size lets it be put on a vehicle and taken to different use locations so more patients can be treated over a larger geographic area
Low exposure to operators since its operated remotely!!!!!!!

Disadvantages

Complex machine that requires special training and experience to use it effectively and safely and like everything....its subject to operator error and mechanical problems from time to time.  

Personally, I think HDRs are neat machines and provide lots of benefit to patients and workers over the old manual methods.  Hope this helps and I'm sure others will chime in with more detail.

Just my opinion.....

Jim Myers
jhm@nrc.gov
 
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