Lecture 4 Answers by Margaret Larkin

margaretlarkin — 2014-02-19 01:41:58 UTC

Eugene, Eric, Anthony, Michael, Grace

1. Why is it necessary to reduce the oxidation state of 99mTc from 7+ to 4+ ?

margaretlarkin — 2014-02-19 01:43:04 UTC

Technetium’s oxidation state must be reduced in order to make it more reactive. Tc-99m becomes more reactive when it is reduced.

^99mTc in the 7+ oxidation state is a nonreactive species. In order for ^99mTc to label a compound it must first be reduced to a 4+ state.

It is necessary to reduce the oxidation of ^99mTc from 7+ to 4+ because the 7+ oxidation state is not very reactive.

^99mTc is reduced to the 4+ oxidation state to make it more reactive.

Tc must be reduced to a lower oxidation number than 7+ to make it more reactive.

2. Why is freshly eluted 99mTc necessary in HMPAO kits?

margaretlarkin — 2014-02-19 01:43:42 UTC

Tin is needed for the reduction of technetium and the tin content in HMPAO kits is limited. ^99mTc can decay into ⁹⁹Tc and they compete with each other in all chemical reactions. Therefore freshly eluted ^99mTc is required to maximize the labeling yield. The kit will break down over time and will not cross the blood brain barrier as easily if fresh eluted Tc-99m is not used. Also, maximum

labeling yield occurs with freshly eluted Tc-99m.

HMPAO kits require a limited amount of Sn2+. Freshly eluted ^99mTc must be used to maximize labeling efficiency.

Freshly eluted ^99mTc is necessary because the limited amount of tin available for reduction of ^99mTc in the kits and the competition by ⁹⁹Tc both lower the labeling yield. Using freshly eluted ^99mTc will maximize the labeling yield.

The tin content in HMPAO kits is limited, and therefore freshly eluted 99mTC is required for maximum labeling yield.

3. The pertechnetate ion is similar to which other ion in the body?

margaretlarkin — 2014-02-19 01:45:00 UTC

iodide

4. What is the hottest organ in the body at 30 minutes post injection of technetium?

margaretlarkin — 2014-02-19 01:45:41 UTC

stomach

5. What is different about the uptake of Tc vs the uptake of Iodine in the thyroid gland?

margaretlarkin — 2014-02-19 01:45:58 UTC

the thyroid gland will trap technetium but will not organify it.

Tc-99mO4 cannot be organified like iodide can

The Thyroid gland will trap Tc^99m but not organify it. Iodine is organified by the thyroid.

In the thyroid gland, Tc is trapped by the thyroid gland similar to iodine but Tc is not

organified as iodine would be.

The thyroid gland will trap Tc thru active transport, but not organify it.

6. Which cells in the brain trap technetium?

margaretlarkin — 2014-02-19 01:46:14 UTC

choroid plexus