RE: A Question for Power Reactor Types and others with portal monitors.

["Vernig, Peter G." <Peter.Vernig@MED.VA.GOV>]

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



__________________________________

Do you Yahoo!?

Yahoo! Small Business $15K Web Design Giveaway 

http://promotions.yahoo.com/design_giveaway/

************************************************************************

You are currently subscribed to the Radsafe mailing list. To

unsubscribe, send an e-mail to Majordomo@list.vanderbilt.edu  Put the

text "unsubscribe radsafe" (no quote marks) in the body of the e-mail,

with no subject line. You can view the Radsafe archives at

http://www.vanderbilt.edu/radsafe/