The Effect of Scan Duration on the Measurement of Perfusion Parameters in CT Perfusion Studies of Brain Tumors

RATIONALE AND OBJECTIVES: The aim of this study was to investigate the effect of scan duration on the measurement of blood flow (BF), blood volume (BV), and permeability-surface area product (PS) in patients undergoing computed tomography (CT) perfusion for brain tumors. MATERIALS AND METHODS: CT perfusion scans were performed in 14 patients with malignant glioma. Patients were scanned for 150 seconds, and BF, BV, and PS were assessed for scan durations of 150, 120, 90, and 60 seconds. Systematic, random, and percentage errors associated with shorter scan durations were calculated. Repeated-measures analyses of variance with paired t tests were used to compare the perfusion values measured from different scan durations. Systematic and random errors were correlated with scan duration. RESULTS: No effect of scan duration on BF and BV values was noted (P > .05). PS values were not affected by scan duration except in the tumor rim, in which they were significantly higher at 60 seconds (P < .01). Median percentage error was highest at 60 seconds for tumor core PS (median, 32.1%; interquartile range, 16.5%-43.0%). Tumor rim BV and PS and tumor core BF were correlated with scan durations (r = 0.42, -0.50, and -0.50, respectively; P < .01). Random errors were negatively correlated with scan durations for all tissue types (P ≤ .01) except for white matter BV. CONCLUSIONS: A scan duration of ≤60 seconds is not warranted for the measurement of PS in brain tumors. A scan duration of ≥90 seconds is recommended.