Tl-201 Cardiovascular Dose

["Carbaugh, Eugene H" <gene.carbaugh@pnl.gov>]

As a non-medical HP (internal dosimetrist), I don't usually want to try
to second guess to the detail you requested what was done in any single
nuclear medicine procedure.  I would suggest for definitive answers you
recommend to the worker that he pose these questions to the nuclear
medicine people or the cardiologist who prescribed the procedure.

However, I do find NCRP Report No. 100, "Exposure of the U.S. Population
from Diagnostic Medical Radiation," to be a useful compilation of
summary information about doses associated with typical procedures.
Table 4.19 in that report lists 7.1 mSv as the typical effective dose
equivalent for a cardiovascular exam, with 45.5 mGy (Table 4.17) for the
male gonadal dose from a 111 MBq Tl-201 chloride administration.

ICRP-53 tabulates a 0.23 mGy/MBq effective dose equivalent coefficient
for Tl-201, along with a specific organ dose coefficients of 0.56
mGy/MBq (testis), 0.54 mGy/MBq (kidney), 0.36 mGy/MBq (lower large
intestinal wall), 0.34 mGy/MBq (bone surfaces), and 0.23 mGy/MBq
(heart).  Others are tabulated, too.

I also have a Journal of the Society of Radiological Protection article
(4:2, 1984) by T. Smith, "Internal Exposure of Patients and Staff in
Diagnostic Nuclear Medicine Procedures," which I have found to be a
useful reference for medical doses.  Table 1 of that article shows a
Tl-201 procedure of 74 MBq giving an effective dose equivalent of 16
mSv, with the organs receiving the highest dose to be the testes (50
mGy) and the kidneys (24 mGy).

Gene Carbaugh, CHP
Internal Dosimetry
Radiation Protection Services
Pacific Northwest National Laboratory
Richland, WA

gene.carbaugh@pnl.gov