Evaluation of efficacy of a drug for improving cerebral blood flow using subtraction SPECT with 99mTc-HMPAO and Patlak plotting

Subtraction SPECT, which being useful for evaluation of a drug improving cerebral blood flow (CBF), and Patlak plotting (PP) were examined for their possibility to predict and judge the efficacy of the drug during its long-term treatment. Ten patients with cerebral infarction >1 month after crisis (5 males and 5 females, mean age of 71.9 y) were firstly measured for their brain perfusion index by PP after intravenous administration of 370-740 MBq of 99mTc-HMPAO (hexamethyl propylene amine oxime). Then, they were given with oral dose of nilvadipine (4 mg) and 4 hr after this, the 1st SPECT was performed. The 2nd SPECT with the additional same dose of 99mTc-HMPAO was done to obtain subtraction images 16 min after the 1st SPECT. Nilvadipine was repeatedly given for 1 month and the 3rd SPECT was carried out. In subtraction positive 4 cases, clinical symptoms were improved together with improvement of CBF in normal hemispheres while, in negative 5 cases, no improvements were observed. Subtraction SPECT and PP were thus found useful for the present purpose. (K.H.)