Increasing Sampling Interval in Cerebral Perfusion CT: Limitation for the Maximum Slope Model

Rationale and Objectives: The aim of this study was to evaluate increased sampling intervals on cerebral dynamic perfusion computed tomographic (PCT) imaging calculated using software relying on the maximum slope model. Materials and Methods: PCT data sets from 32 patients with suspected acute stroke were acquired with a sampling interval of 1 image/s. The PCT data sets were modified to simulate sampling intervals of 2, 3, and 4 seconds. Maps of cerebral blood flow (CBF), cerebral blood volume, and time to peak (TTP) were calculated using software relying on the maximum slope model. Parenchymal and vascular peak enhancement; absolute values of CBF, cerebral blood volume, and TTP in the nonischemic hemisphere; and ischemic area in the different perfusion maps were measured. Results: Parenchymal peak enhancement of the nonischemic hemisphere was statistically significantly decreased in all simulated data sets with >1-second sampling intervals (P<.001). Absolute CBF and TTP values in the nonischemic hemisphere were increased in all simulated data sets with >1-second sampling intervals (P=.044-001 and P=.008-001, respectively). The ischemic area was significantly underestimated for CBF and TTP in all simulated data sets with >1-second sampling intervals (P=.022-005 and P=.019-005, respectively). Conclusions: Sampling intervals of >1 second on PCT imaging calculated using software relying on the maximum slope model significantly after absolute CBF and TTP values and the size of ischemia in CBF and TTP. Thus, increasing the sampling interval on dynamic PCT imaging cannot be recommended in combination with this algorithm.