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RE: Thalium Stress Test
Thalium 201 (and not thallium 210) and technetium 99m are used to perform
myocardial perfusion imaging. [201Tl] thallous chloride was almost
universally employed for the detection of ischaemia.
Traditionally, [201Tl] thallous chloride is injected (i.v.) at peak exercice
and the exercice continued for a further minute. The activity administered
is 60-80 MBq (2 mCi) and the effective dose equivalent is 15-20 mSv (1850
mrem).
Of the 99mTc 2-methoxy-isobutyl-isonitrile (SestaMIBI or MIBI) and
diphosphene Tetrofosmin have been most completely evaluated. Tetrofosmin is,
however, easier to prepare than MIBI. The activity administered is 400 MBq
and the effective dose equivalent is 8 mSv (800 mrem).
There is now considerable evidence for the utility of both 201Tl and the
99mTc labelled agents in the detection of coronary artery disease.
Sensitivity and specificity are generally accepted to be of the order of 80%
and 90% respectively, and are generally superior to exercice
electrocardiography. In addition to the detection of coronary disease,
important information is available about the site of ischaemia and extent.
I'm radiopharmacist and not physician but for your friend I think that the
stress test can be useful because he has experienced some central chest
pain. But I'm not really worried : your friend is young and I understood
that the pain is not constant. So don't worry !
"These are my opinions and my opinions only!"
Jean-René Jourdain
-----Message d'origine-----
De : Tonry, Louie L MAJ EAMC [mailto:Louie.Tonry@se.amedd.army.mil]
Envoyé : lundi 8 janvier 2001 17:55
À : Multiple recipients of list
Objet : RE: Thalium Stress Test
This sounds to me as being an unnecessary test given the limited
information. However to comment on the information provided, I'd make the
following observations.
1. Cardiac imaging is now done frequently with technetium
cardiolite. Some physicians prefer Tl-210 but the half-life is longer and
will likely lead to a higher exposure to the patient.
2. Based on the history (and giving the disclaimer that I'm not a
physician), I probably wouldn't be reluctant to not have the test if I were
the patient unless there were other reasons such as history or other events
before or after this one.
3. The dose though is quite low. The cardiolite results in a total
body absorbed dose of ~0.5 rem - though higher than background, not
something I'd worry about.
There are certainly other diagnostic procedures that can be
preformed but rad tracer stress testing is a good procedure. It identifies
areas of muscle that have limited uptake due to poor uptake of the tracer.
This poor uptake can be caused by limited blood flow to the muscle. I would
note that if this test is read as positive, the next likely place your
friend will find himself is in the cath lab and that does result in high
doses.
"These are my opinions and my opinions only!"
Louie Tonry
louie.tonry@se.amedd.army.mil
-----Original Message-----
From: GRAHNK@aol.com [mailto:GRAHNK@aol.com]
Sent: Monday, January 08, 2001 11:23 AM
To: Multiple recipients of list
Subject: Thalium Stress Test
OK,
Here's one for all you medical folks out there. One of my people (40 year
old male) had a 3 week bout with pneumonia last year. This year when
exposed
to cold outside air (0 degrees and below) he has experienced some central
(sternum) chest pain that goes away when he doesn't breathe the cold air.
He
doesn't have any history or family history of cardiac illness.
His family practice physician (not a cardiologist) has ordered a thalium
stress test. He's been asking me and we're both wondering why? It's not
clear what the doc is looking for.
Does this make sense from an ALARA perspective? Is there an alternate
diagnostic procedure that doesn't involve radioactive material? i.e. echo
or
stress echo
If he proceeds with this procedure what might his expected dose be?
Thanks
Kelly Grahn
Illinois Department of Nuclear Safety
West Chicago Field Office
grahnk@aol.com
or
grahn@idns.state.il.us
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information can be accessed at http://www.ehs.uiuc.edu/~rad/radsafe.html