Sensitivity of rCBF to focal lesions.

The ability of the 133Xenon inhalation method to lateralize cerebral infarctions visible on CT scan was tested in 39 patients. At each of 7 hemispheric regions the flow rate in the lesioned hemisphere was divided by that in the unaffected hemisphere and this ratio was compared with the corresponding ratio for normal subjects. The fast compartment relative flow f1 correctly lateralized the lesion in only 6 patients with no false lateralizations. If the fast compartment relative weight w1 was also considered, the correct lateralizations were increased to about 50%. With the less well-known ISI and the Fractional Flow considered together, the laterality of the lesion was identified correctly in 85% of cases, with no false lateralizations.