Diagnostic Threshold Values of Cerebral Perfusion Measured With Computed Tomography for Delayed Cerebral Ischemia After Aneurysmal Subarachnoid Hemorrhage

Abstract

Background and Purpose-Early diagnosis of delayed cerebral ischemia (DCI) after aneurysmal subarachnoid hemorrhage is critical but difficult. We analyzed diagnostic threshold values of CT perfusion for use in detection of DCI in patients with subarachnoid hemorrhage. Methods-We prospectively enrolled patients with subarachnoid hemorrhage with CT perfusion on admission and at time of clinical deterioration or after 1 week if no deterioration occurred. The gold standard was the clinical diagnosis of DCI based on all clinical, laboratory, and imaging data except CT perfusion. Patients with failed imaging (nϭ6) and other causes of deterioration (nϭ45) were excluded for the current study. We measured CT perfusion values, including cerebral blood volume, blood flow, mean transit time (MTT), and time to peak in predefined regions of interest and then compared absolute perfusion and perfusion asymmetry for patients with and without DCI. Diagnostic threshold values for DCI were evaluated and sensitivity and specificity calculated for optimal thresholds. Results-Of 85 eligible patients with subarachnoid hemorrhage, 50 had DCI; 35 patients with no clinical deterioration comprised the reference group. Cerebral blood flow was significantly lower, MTT higher, and perfusion asymmetry larger in patients with DCI. We found that largest absolute MTT and the MTT difference between hemispheres were good diagnostic tests. Diagnostic threshold values with optimal sensitivity and specificity were an MTT of 5.9 seconds and an MTT difference of 1.1 second. Conclusion-Thresholds

Volume perfusion CT (VPCT) for the differential diagnosis of patients with suspected cerebral vasospasm: Qualitative and quantitative analysis of 3D parameter maps

“…Median age of the included patients was 51 years (range 36-82). Nineteen patients had an SAH caused by an aneurysm rupture, which was treated either by neurosurgical clipping (10) or endovascular coiling (9). Four patients had an SAH as a result of a vessel dissection or due to an operative or interventional bleeding complication (Table 1).…”

“…Recent studies [9,21,25] increasingly focus on quantitative CT perfusion measurements in order to determine quantitative diagnostic thresholds. In addition to the qualitative analysis of perfusion deficits our quantitative results show that the absolute values of TTD, TTS, MTT, TTP and CBF in the affected brain differ significantly in comparison to the contralateral not affected brain parenchyma.…”

Impact of image denoising on image quality, quantitative parameters and sensitivity of ultra-low-dose volume perfusion CT imaging

“…The simulation method used by Tong and Wintermark to validate their approach, however, is unrealistic in the sense that neither slice-to-slice variation nor tissue dependency of noise magnitude was taken into account in their noise addition algorithm. Because the slice-to-slice difference in head size may have a bigger impact on noise magnitude than reduction in tube current, their simulation results by using a simple noise addition technique might include mixed effects of reduced tube current VPCT has also been shown to be an effective tool for the monitoring of vasospasm in patients with subarachnoid haemorrhage [14][15][16][17]. In these cases, multiple successive VPCT scans are often obtained in the same patient.…”

Evaluating the diagnostic accuracy of CT perfusion in patients with cerebral vasospasm after aneurysm rupture: a meta-analysis

“…First, other pathological conditions, like edema and infection, might also affect cerebral perfusion (3,4). If the author did not carefully identify the perfusion changes causing by other pathology, the results of CT perfusion could be blurred and false-positive findings were produced.…”