Motor stimulation response by technetium-99m hexamethylpropylene amine oxime split-dose method and single photon emission tomography

We applied the technetium-99m hexamethylpropylene amine oxime (99mTe-HMPAO) split-dose method in order to evaluate the feasibility of assessing cerebral blood flow (CBF) changes with single photon emission tomography (SPET) during a motor activation task. Eleven normal subjects were studied using the Tomomatic 564 (Medimatic, DK). Five subjects were studied twice at rest and 6 subjects at rest and during a motor task performance (finger opposition movements). A total of 28 mCi of 99mTc-HMPAO was injected in 2 doses with a 1:3 ratio. The first scan was obtained after injection of 7 mCi at rest in all subjects. The second scan was obtained a few minutes later, after injection of the remaining dose (21 mCi), under similar resting conditions or during a motor task performance. The mean brain uptake was proportional to the amount of tracer injected and to the acquisition time for both the first scan (5263 ± 1266 counts x mCi x min) and the second (5034.4 ± 966 counts x mCi x min). The grey/white matter ratio was 1.67 ± 0.019 and 1.67 ± 0.097 for the two scans, respectively. A three-way analysis of variance (ANOVA) for repeated measure showed no significant effects of side, slice and region of interest (ROI) on the CBF in the 5 subjects studied twice at rest, and the mean regional CBF change was -0.2% ± 5%. In the 6 subjects studied at rest and during motor activation, the image subtraction analysis showed a significant CBF increase in the primary motor cortex contralateral to the stimulated side (15% ± 7%, n = 6) and medially in the supplementary motor area (22% ± 12%, n = 4). Our results indicate that the split-dose method allows the detection of a local CBP response to motor activation using 99mTc-HMPAO in a single imaging session.