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RE: A Question for Power Reactor Types and others with portal mon itors.
Tl-201 is produced by Tl-203 + P --> Pb-201 + 3n -->
Tl-201 (EC) in 9.4 hours. Also, Tl-203 + P --> Pb-200
+ 4n --> Tl-200 (Beta decay) in 21.5 hr.
That is what I get from
http://www.nuclearonline.org/PI/Mallinckrodt%20Thallium.pdf
I am looking at an old text book that mentions the
Tl-203 + n --> Tl-204 reaction. I am wondering if
that is in error based on what I see from the
manufacturer's insert. (Will need to check on this)
I am not surprised that your patient set off the trash
monitors. They are probably large NaI detectors, like
the kind used by Homeland Insecurity people.
--- "Vernig, Peter G." <Peter.Vernig@med.va.gov>
wrote:
> John,
>
> The impurities listed on the package insert I have
> for Tl-201 are only
> Tl-200 and Tl-202, and Pb-203 and of those only
> Tl-202 has a half life
> longer than Tl-201. Where did Tl-204 come from?
>
> As an aside, I just checked a patient who had a 250
> mCi administration of
> I-131 ten days ago. My ion chamber [Bicron RSO-5]
> just barely budged off
> zero on the 0 - 5 mR/hr scale. I would hesitate to
> say it detected anything
> but say 0.05 mR/hr. He set off our trash alarm, NaI
> 1.5 inch Bicron system
> at about 10 feet.
>
> Any opinions expressed in this message are mine
> alone and do not necessarily
> represent those of the Eastern Colorado VA Health
> Care System, The
> Department of Veterans Affairs, or the United States
> Government.
>
> Peter G. Vernig
> Radiation Safety Officer, VA Eastern Colorado Health
> Care System, 1055
> Clermont St. Denver, CO 80220, ATTN: RSO MS 115;
> peter.vernig@med.va.gov;
> personal peter_vernig@hotmail.com; 303.399.8020 ext.
> 2447, FAX: 303.393-5026
> Alternate fax 303-377-5686
> "...whatever is true, whatever is noble, whatever is
> right, whatever is
> pure, whatever is lovely, whatever is admirable, if
> anything is found to be
> excellent or praiseworthy, let your mind dwell on
> these things."
> Paul of Tarsus
>
>
> -----Original Message-----
> From: John Jacobus [mailto:crispy_bird@yahoo.com]
> Sent: Thursday, April 08, 2004 1:48 PM
> To: Flood, John; Sewell, Linda;
> Peter.Vernig@MED.VA.GOV;
> Radsafe@list.vanderbilt.edu
> Subject: RE: A Question for Power Reactor Types and
> others with portal
> mon itors.
>
>
> I picked a bone imaging agent as the Tc-99m labeled
> compound has a fairly long retention in the bone.
> The
> limiting factor in this case is the half-life of the
> Tc-99m. (Also, the number I gave assumes all is
> taken
> up in the bone. Generally, the patient empties
> their
> bladder before the first image is taken).
> Obviously,
> other imaging compounds would have shorter effective
> half lives.
>
> Thallium is analgous to potassium, so its effective
> half life will be based on both the excretion of
> potassium and the half life of the radioisotope.
> Generally, you see the Tl-204 for quite sometime.
>
> One possible reason for more heart scans using
> Tl-201
> is the ease of the procedure. There have also been
> articles recommending that patients who arrive at
> Emergency Rooms demonstrating heart problems be
> given
> a nuclear medicine scan prior to admission. If the
> patient does not show signs of heart disease, they
> are
> not admitted. Saves hundreds of bucks.
>
> Have you ever done a spectral analysis of the Tc-99m
> injected patients to see what the radionuclide is?
>
> --- "Flood, John" <FloodJR@NV.DOE.GOV> wrote:
> > -----Original Message-----
> > From: John Jacobus [mailto:crispy_bird@YAHOO.COM]
> > Sent: Thursday, April 08, 2004 10:51 AM
> >
> > "If a patient is given a bone scan
> > with 30 mCi of Tc-99m, after 3 days there may
> still
> > be
> > 7 microcuries of activity present."
> >
> > Actually, there may be AS MUCH AS 7 uCi remaining.
>
> > The effective half-life
> > will also include the biological elimination rate,
> > and varies greatly from
> > individual to individual.
> >
> > "Tl-201 is only used for heart scans. While it is
> > has
> > a half life of 3 days, there are Tl-202 and Tl204
> > contaminates. However, you do not retain thallium
> > chloride."
> >
> > Again, this is heavily related to biological
> > elimination rates. Our
> > experience is that Tc-99m is rarely detectable for
> > more than 10 days and
> > usually undetectable in a week or less, but Tl-201
> > cases remain detectable
> > longer. The longest lived of our cases (a month
> > each) were both Tl-201
> > stress tests.
> >
> > And our experience probably mimics others - the
> > overwhelming majority of
> > detectable medical uses are Tc-99m, with Tl-201
> > second - the stress test
> > business is booming (thanx to baby boomers, no
> > doubt).
> >
> > The other big player is therapeutic I-131 thyroid
> > treatments - not only can
> > they last a long time, they are detectable from a
> > great distance.
> >
> > Bob Flood
> > Nevada Test Site
>
>
> =====
> +++++++++++++++++++
> "Those who have not known the joy of standing up for
> a great cause of
> justice have not known what makes living
> worthwhile."
> Paul Painleve, regarding the Dreyfus Affair, 1895
>
> -- John
> John Jacobus, MS
> Certified Health Physicist
> e-mail: crispy_bird@yahoo.com
>
> __________________________________
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=====
+++++++++++++++++++
"Those who have not known the joy of standing up for a great cause of justice have not known what makes living worthwhile."
Paul Painleve, regarding the Dreyfus Affair, 1895
-- John
John Jacobus, MS
Certified Health Physicist
e-mail: crispy_bird@yahoo.com
__________________________________
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