Re: Beta Emitters and Dose Calibrators

[carol marcus <csmarcus@ucla.edu>]

At 02:45 PM 10/8/99 -0500, you wrote:
>Carol- You wrote:
>
>"Your assumption that more precision is needed for therapy than
>diagnosis is dead wrong.  Many diagnostic tests require more precision
>because of the technique and data processing involved.  Any old amount of
>I-131 can treat hyperthyroidism, and if it isn't enough the first time, you
>give a second or third dose.  The same patient can go to 2 doctors, and one
>could prescribe 2 mCi and the other 30 mCi
>and each doctor would manage to cure the disease.  
>
>Ciao, Carol"
>
>
>Darn!  I hate it when I'm dead wrong.  But seriously, is your hyperthyroidism
>argument really representative?  There must be a fairly wide safety margin 
>between a theraputic dose and a harmful dose when you're hitting the thyroid
>with I-131.  I would doubt whether any other theraputic nuclear medicine has
>as high a safety margin, just based on what I know about the dosimetry and
>metabolism of radioiodines (correct me if I'm wrong).  And who knows what the 
>future will bring in the area of B- oncology agents.  Safety margins for 
>potentially life saving oncology treatment may be much slimmer.  As you know,
>this is a dynamic field with lots of possiblities on the horizon.  I guess
>my main point is that it does not seem prudent to so quickly and casually
>dismiss the accuracy of beta emitter assays as a non-issue with no
>impact on the patient.
>
>
>John Laferriere, CHP
>DuPont Pharmaceuticals Co.
>Medical Imaging Division
>john.r.laferriere@dupontpharma.com
>Standard Disclaimers
>
>
>
>
>
>
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Dear John:

At present, the hyperthyroid situation is representative. Unlike radiation
oncology, we cannot control absorbed doses to a high degree of accuracy,
although some of the brachytherapy absorbed doses are similarly imprecise.

As I said, when it becomes an issue, docs will be the first to push
engineers and physicists to make it possible to measure pure beta emitters
with more accuracy.  

As I envision the future of therapy nuclear medicine, if there is any future
with the dysfunctional behavior of FDA, NRC and HCFA, we will eventually
need personal dosimetry and accurate activity measurement.  However, with
NRC selling licenses to docs who have absolutely no idea how to approach
personal dosimetry,  it is difficult to imagine what will happen.  The best
thing would be to end NRC's "medical" program so that the requirements for
Authorized User physicians can be something other than a fraudulent federal
farce based on NRC's need to collect User Fees. Many states are really fed
up with NRC's lax licensing, and would appropriately tighten up standards if
they could eradicate the heavy hand of White Flint.

Ciao, Carol

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