Clinical utility and reliability of sup(81m)Kr SPECT images applied to posterior circulation

The instrument used in this study has a sensitivity of 28,000 counts/mCi/cm3 for sup(99m)Tc and a spatial resolution of approximately 20mm full width at a half-maximum. The tomographic images were obtained by the continuous infusion of sup(81m)Kr at the base of the ascending aorta. Material was subsequently studied in 49 cases that met the conditions of: 1) obstructive vertebrobasilar system lesions (8 cases), 2) no ischemic cerebrovascular diseases (10), or 3) ischemic cerebrovascular disorders in anterior circuration (31). The reproducibility, as studied in 20 cases, was satisfactory. 6 cases were compared with a stable Xe CT CBF map that had regional depressions similar to those of the sup(81m)Kr SPECT images. In the 2nd group, 8 of the 10 cases showed a mild laterality on cerebellar perfusion images obtained by SPECT, as did 29 of the 31 in the 3rd group; among them, 2 cases with a recently completed stroke revealed a marked depression in the ipsilateral cerebellar hemisphere to the side of the hemiplegia. Cases of the lst group showed generally depressed perfusion images of the brain stem or cerebellum, and the low-density areas of X-ray CT were comparable to the lower perfusional regions on SPECT. The authors concluded that posterior perfusion images obtained by sup(81m)Kr SPECT were affected by occlusive vertebrobasilar-system lesions as well as by carotid-system lesions and cerebellar functions, and that this method for evaluating hemodynamics will be of much more clinical use in repeated studies to demonstrate the changes in posterior cicuration in course or by some loadings with subclinical characteristics, for this paper includes the first report on cerebellar functional images, though it is restricted by the low-spatial resolution from defining the architecture of the posterior fossa in detail. (authro)