Purpose Admission infarct core lesion size is an important determinant of management and outcome in acute (<9 hrs) stroke. Our purpose was to: (1) determine the optimal CT perfusion (CTP) parameter to define infarct core using various post-processing platforms, and (2) establish the degree of variability in threshold values between these different platforms. Methods We evaluated 48 consecutive cases with vessel occlusion and admission CTP and DWI within 3 hours of each other. CTP was acquired with a “second-generation” 66-second biphasic cine protocol, and post-processed using “standard” (from two vendors, “A-std” and “B-std”) and “delay-corrected” (from one vendor, “A-dc”) commercial software. ROC curve analysis was performed comparing each CTP parameter - both absolute and normalized to the contralateral uninvolved hemisphere - between infarcted and non-infarcted regions, as defined by co-registered DWI. Results Cerebral blood flow (CBF) had the highest accuracy (ROC “area under curve”, AUC), for all three platforms (p<0.01). The maximal AUC's for each parameter were: absolute CBF 0.88, CBV 0.81, and MTT 0.82, and relative CBF 0.88, CBV 0.83, and MTT 0.82. Optimal ROC operating point thresholds varied significantly between different platforms (Friedman test, p<0.01). Conclusion Admission absolute and normalized “second-generation” cine acquired CT-CBF lesion volumes correlate more closely with DWI defined infarct core than do those of CT-CBV or MTT. Although limited availability of DWI for some patients creates impetus to develop alternative methods of estimating core, the marked variability in quantification amongst different post-processing software limits generalizability of parameter map thresholds between platforms.

Sildenafil administration during testicular torsion decreased ischemia/reperfusion cellular damage. The results of biochemical studies suggest that, reduction of oxidative stress by sildenafil may have a major role in its cytoprotective effects.

Purpose To characterize the spatial pattern of cerebral ischemic vulnerability to hypoperfusion in stroke patients. Methods We included 90 patients who underwent admission CT perfusion (CTP) and MRI within 12 hours of ischemic stroke onset. Infarcted brain lesions (“core”) were segmented from admission diffusion-weighted-imaging (DWI), and - along with the CTP parameter maps - coregistered onto MNI-152 brain space, which was parcellated into 125 mirror cortical and subcortical regions per hemisphere. We tested the hypothesis that the percent infarction increment per unit relative cerebral blood flow (rCBF) reduction differs statistically between regions using regression analysis to assess the interaction between regional rCBF and region variables. Next, for each patient, a “vulnerability index” (VI) map was constructed with voxel values equaling the product of that voxel’s rCBF and infarction probability (derived from the MNI-152-transformed, binary, segmented DWI lesions). Voxel-based rCBF threshold for core was determined within the upper 20th percentile of VI map voxel values. Results Different regions had different percent infarction increase per unit rCBF reduction (p=0.001). The caudate body, putamen, insular ribbon, paracentral lobule, precentral, middle and inferior frontal gyri had the highest ischemic vulnerability to hypoperfusion. A voxel-based rCBF threshold of <0.42 optimally distinguished infarct core in the highly-vulnerable regions, whereas rCBF <0.16 distinguished core in the remainder of the brain. Conclusion We demonstrated regional ischemic vulnerability of the brain to hypoperfusion in acute stroke patients. Location specific - rather than whole-brain - rCBF thresholds may provide a more accurate metric for estimating infarct core using CTP maps.