[en] A super high sensitivity slant hole (SHS-SL) collimator was designed. The gamma camera used with this collimator was able to move close to the patient's head and obtain satisfactory count rates (130 kcpm-178 kcpm in a hemisphere) with a low dosage (10 mCi) of Xe-133. To validate this rCBF measurement system three studies were carried out: a comparative evaluation was performed against the flow values with the intracarotid Xe-133 injection (i.c.) method, reproducibility of flow values was assessed from two serial i.v. measurements, and flow values were compared with clinical severity of the patients. The comparative study showed good correlation in the hemispheric and regional values between the two methods. In the reproducibility study, the variation coefficients in the hemispheric and regional values between the two serial measurements were 5.0% and 7.3%-14.2% for gray matter flow, 5.2% and 7.9%-12.9% for initial slope index. The reproducibility was as good as those with the i.c. method reported. The hemispheric flow values from our gamma camera system correlated well with the clinical severity of cerebrovascular disease. (orig./HP)