Tomographic Studies of rCBF with [ 99m Tc]-HM-PAO SPECT in Patients with Brain Tumors: Comparison with C 15 O 2 Continuous Inhalation Technique and PET

In 10 patients with malignant gliomas, the intracerebral distribution of [^99mTc]–hexamethylpropyleneamine oxime ([^99mTc]–HM-PAO) was studied with single photon emission computed tomography (SPECT) in comparison with C¹⁵O₂ steady-state inhalation technique to measure cerebral blood flow using positron emission tomography (PET). In all instances, the cerebral [^99mTc]–HM-PAO distribution was comparable with the regional pattern of cerebral blood flow (rCBF) observed with PET. This was confirmed by a significant correlation of tumor to cortex and tumor to white matter ratios between these two experimental methods. However, the contrast between high and low activity regions in the SPECT scans was significantly less than that in the PET scans. Contrast enhancement of the SPECT scans was accomplished using a correction formula proposed by Lassen.