Cerebral blood flow measurements using quantitative SPECT. Comparison with PET

The dual table autoradigography (DTARG) quantitative single photon emission computed tomography (QSPECT) method using 123I-IMP was performed on 15 patients with unilateral major cerebral artery occlusive diseases. Severity of hemodynamic brain ischemia was classified into three stages (stages 0 to II) based upon the vasodilative function calculated from cerebral blood flow (CBF) values at rest and during acetazolamide challenge. This staging by DTARG QSPECT was compared with staging of hemodynamic brain ischemia also classified into stage 0 to stage II by 15O gas inhalation steady state method using positron emission tomography (PET). Out of 15 patients, 10 patients diagnosed as stage II in QSPECT and PET (decreased baseline CBF with deceased vascular response below 10% increase by QSPECT and elevation of oxygen extraction fraction by PET). Two patients showed concordant stage I conditions for both methods (vascular response between 10 and 30% increase or normal baseline CBF with vascular response below 10% increase by QSPECT and elevation of cerebral blood volume by PET). The remaining 3 patients showed stage II conditions according QSPECT in spite of stage I diagnosis based on PET. Baseline CBF values by QSPECT showed significantly high correlation (r=0.786) to data aquired by PET. Although DTARG QSPECT has a tendency to overestimate the severity of hemodynamic brain ischemia, it provides high accuracy of 80% in this staging as compared with PET. These results suggest that DTARG QSPECT has a high clinical value in managing patients with cerebrovascular occlusive diseases. (author)