Question

3. A patient is administered 111 MBq (3 mCi) of 131 as a treatment for Graves' disease. Uptake studies show that the thyroid rapidly absorbs 60% of the administered dosage. The biological and radiological half-life of 131I is 2 days and 8.01 days, respectively. The average energy per transformation of 131I is 0.230 MeV/transformation. Assuming that the uptake of 131I in the thyroid is very rapid (i.e., instantaneous), calculate the initial dose rate and the total dose (commitment) to the thyroid from this treatment. a. b. (1.6 x10-13 Joule/MeV; mthyroid-600g)

Answer 1

3. Grave's disease is an auto-immune disease characterized by elevated levels of thyroid stimulating receptor (TSH) receptor antibodies with increased production of thyroid hormone.

The incidence shows that 60-80% hyperthyroidism has Graves Disease.

One of the treatment options of the disease is Radio-active Iodine therapy (RAI), also called!-131 therapy.

When selecting the appropriate dose of RAI, it is controversial.

A fixed-dose regime is more convenient to use

Here the patient is administered 111MBq (3mci) of I 131 as a treatment for Grave's disease.

The biological Half-life of I 131 is 2 days and 8.01 days.

The average energy per transformation of I 131 is 0.2320 MeV/transformation

Here the uptake of I 131 is very rapid.

Thus the dose of I 131 is:

a. Initial dose rate is 370 MBq

b. The total dose to the thyroid from this treatment is 0.27REM (rem)