Original investigationsThe effect of varying user-selected input parameters on quantitative values in CT perfusion maps1
Section snippets
Materials and methods
CT perfusion datasets from three patients were analyzed in this study. All patients presented with acute middle cerebral artery infarction; two on the right side and one on the left side. Two male and one female patients were included in the study. The age range was 30–63 years of age. These three datasets were acquired at two different institutions on GE HiSpeed and LightSpeed CT scanners (General Electric Medical Systems, Milwaukee, WI). The protocol for performing CT perfusion used cine mode
Results
All three patients had acute middle cerebral artery territory infarctions identified on MR diffusion-weighted imaging. A total of 192 CTP maps were constructed (64 maps per patient).
Overall, the changes in the CTP quantitative values were most significant in the infarct core compared with the unaffected gray and white matter sampled from the contralateral side. The unaffected gray and white matter did not necessarily reflect these changes, likely because of their higher quantitative values. In
Discussion
In this article, we have confirmed and underscored the theoretical prediction that major variations of either arterial ROI placement or arterial and venous ROI size had no significant effect on the mean CBF, CBV, and MTT values at the infarct core (P > .05). Even minor variations, however, in the choice of venous ROI placement, or in pre- and postenhancement cut-off time point values significantly altered the quantitative values for each of the deconvolution based CTP maps by as much as
Conclusion
To limit potential quantitative error in constructing deconvolution-based CT perfusion maps, we recommend using a standardized procedure for the selection of the user-defined parameters that are required to calculate the CBV, CBF, and MTT maps. Two specific guidelines for constructing CT perfusion maps include: (1) avoid partial volume averaging by selecting the largest vessel perpendicular to the imaging plane for the arterial and venous ROIs, choosing an ROI pixel size to fit the lumen of the
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