Hirofumi Sawamoto

Serial Semiquantitative Imaging of Brain Damage Using Micro-SPECT and Micro-CT After Endothelin-1–Induced Transient Focal Cerebral Ischemia in Rats

In this study, we validated the use of 99mTc-hexamethylpropyleneamine oxime (99mTc-HMPAO) micro-SPECT combined with micro-CT for semiquantification of the infarct size after an experimental stroke in rats and compared our observations with those obtained from histology. This imaging strategy was applied to measure the longitudinal effect of mild hypothermia on the progression of brain damage after stroke in rats. Methods: The endothelin-1 model was used to elicit a transient focal cerebral ischemia in rats. This resulted in a reproducible insult in which the core is represented by the striatum and the penumbra by the cortex. Micro-SPECT and micro-CT images were taken at 1, 3, and 7 d after infusion of endothelin-1 and compared with those taken before the insult. After the last acquisition, rats were sacrificed and the infarct volume was determined via Nissl staining. The results obtained with micro-SPECT and micro-CT were compared with histology at the same time points. Mild hypothermia (33°C) was induced for 2 h, starting 20 min after the insult. Results: Brain damage was estimated using micro-SPECT and micro-CT and was reproducible with minimal interobserver variability. Normothermic stroke rats had reduced 99mTc-HMPAO uptake at 1 and 3 d after the insult, whereas hypothermia improved damage after stroke. These findings corroborate with histology at the same time points. At 1 wk after the insult, no reduction of radioactive uptake was observed in any treatment group. Conclusion: Micro-SPECT and micro-CT allow quick and reproducible semiquantification of brain damage as an interesting alternative to histology to measure the extent of infarcted tissue in small animals after stroke.

Clinical role of 123I-IMP SPECT for the differential diagnosis of ocular malignant melanoma: a time-course analysis.

ObjectiveTo evaluate the efficacy of 123I-IMP single photon emission computed tomography (SPECT) for the diagnosis of ocular malignant melanoma (MM). MethodsThirty-eight patients (18 males, 20 females) clinically suspected of having ocular MM were retrospectively examined in this study. The age of patients ranged from 8 to 81 years (mean 55.6 years). Twelve patients were finally diagnosed as having ocular MM. Orbital SPECT images were taken 15 min, 4 h, 24 h and 48 h after intravenous injection of 111–222 MBq (3–6 mCi) 123I-IMP. 123I-IMP uptake in the orbital tumor was visually evaluated as−(negative),±(equivocal), or+(positive). The uptake index (UI) and increase ratios (IRs) were calculated. ResultsFor visual evaluation, the accuracy of 123I-IMP for the diagnosis of MM was 73.7% (15 min), 81.6% (4 h), 81.6% (24 h) and 86.8% (48 h). When UI and IR were calculated on both the MM and non-MM groups, the UI and IR of the MM group were significantly higher than those of the non-MM group (P<0.001). Moreover, the highest sensitivity (100%) and accuracy (94.7%) were obtained 48 h after 123I-IMP administration when the cut-off value of UI was defined as 1.90. ConclusionsThis study shows that 123I-IMP SPECT is useful for the diagnosis of ocular MM. The UI values 48 h after the injection were efficient for the differentiation between MM and non-MM lesions.