RT Journal Article
SR Electronic
T1 Effect of Technetium-99m on Iodine-131 Thyroid Uptake Measurements
JF Journal of Nuclear Medicine Technology
JO J. Nucl. Med. Technol.
FD Society of Nuclear Medicine
SP 68
OP 71
VO 13
IS 2
A1 Wasserman, Herman J.
A1 Klopper, Johannes F.
A1 Erlank, Petro
YR 1985
UL http://tech.snmjournals.org/content/13/2/68.abstract
AB Following administration of 2.5–5.0 mCi [99mTc]pertechnetate, several hundred microcuries may be present in the necks of hyperthyroid patients after 6 hr. Coincidence summing of Tc-99m photons may disturb I-131 uptake measurements in such patients if an oral diagnostic dose of I-131 is administered immediately after completion of a [99mTc]pertechnetate scintigram. Using a lower discriminator level of 300 keV, false increases of 10%–50% may occur at 6 hr. The 24-hr uptake is also affected if an I-131 predose measurement is performed after administration of the Tc-99m dose. The authors have shown that these errors may be prevented by using a 1-mm lead filter in front of the scintillation detector. The attenuation of Tc-99m photons by the filter effectively eliminates summation pulses while it reduces the I-131 countrate by approximately 28%.