Xe-133 rCBF measurement reproducibility and normal limits of asymmetry

New software for determination of regional cerebral blood flow (rCBF) has been added to equipment using Xe-133 inhalation and 32 p-m tubes in a helmet-like configuration (NOVO Cerebrograph 32c). The authors examined the reproducibility of rCBF measurements and the degree of asymmetry acceptable as normal. The 2 parameters studied were initial slope index (ISI) and CBF15, both heavily weighted toward the fast clearing compartment (largely grey matter) and relatively free of slow compartment (blurring). In 3 normal volunteers and 7 patients with non-focal stable neurologic disease ISI and CBF15 repeated within 24 hours could vary by as much as 18% and 29-33% respectively (2 s.d. limits) in stable individuals with no focal disease. In 7 patients with documented stable cerebrovascular disease, reproducibility for ISI was 19-22%, CBF15 22-23%, independent of age