Temporal Correlation Analysis of Penumbral Dynamics in Focal Cerebral Ischemia

103

Background and Purpose-We have developed a dynamic CT method to measure absolute cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT). In this study we evaluated the ability of CT-derived functional maps to detect infarction in a rabbit model of focal cerebral ischemia. Methods-Sequential dynamic CT studies were performed at 2 different slices in 5 control rabbits and another 8 after induction of focal cerebral ischemia. The size of critically ischemic tissue was correlated to size of infarction measured by postmortem 2,3,5-triphenyltetrazolium chloride staining. In the control rabbits, short-term variability of the parameters was assessed by ANOVA analysis. Results-In 7 of 8 animals of the ischemia group, cerebral infarction was visible on 2,3,5-triphenyltetrazolium chloride staining, constituting 16.7Ϯ10.6% of the ipsilateral hemisphere. Good agreement of CBF functional maps with tissue specimens was found with respect to size and location of infarction. Best prediction of infarction was found for thresholds of CBF Ͻ10 mL/100 g per minute (mean size, 17.5Ϯ13.4%; rϭ0.95) and MTT Ͼ6 seconds (mean size, 15.6Ϯ13.5%; rϭ0.85), with regression slopes close to unity. CBV maps were less predictive of occurrence of infarction, especially in cases of small infarction. The short-term variability of CBF, CBV, and MTT in the control group was 10.9%, 15.2%, and 19.9%, respectively. Conclusions-Functional

Section: Discussionmentioning

confidence: 99%

Section: Nabavi Et Al Perfusion Mapping Using Ct To Predict Cerebral mentioning

confidence: 99%

Perfusion Mapping Using Computed Tomography Allows Accurate Prediction of Cerebral Infarction in Experimental Brain Ischemia

Nabavi

Cenic

Henderson

et al. 2001

103

“…This view is supported by the recent experimental studies that the hemodynamics in the penumbra was characterized by delays in bolus transit time due to a perfusion through the collateral channels. [31][32][33] Is there any effect of hypervolemia and hypovolemia on evolving ischemic brain damage? Heiss et al studied the relationship between hemodynamic and metabolic failures in acute cerebral infarction and progressive derangement of periinfarct viable tissue in humans.…”

Section: Discussionmentioning

confidence: 99%

Cerebral Blood Volume in Acute Brain Infarction

Hatazawa

Shimosegawa

Toyoshima

et al. 1999

102

Background and Purpose-The aim of this study was to correlate the abnormality in cerebral blood volume (CBV) measured by dynamic susceptibility contrast-enhanced MRI with that in cerebral blood flow (CBF) estimated by single-photon emission CT with [ 99m Tc]hexamethylpropylenamine-oxime in patients with acute ischemic stroke. Methods-Nine patients with unilateral occlusion of either the middle cerebral artery or the internal carotid artery (4 men and 5 women; meanϮSD age, 74.4Ϯ11.6 years) were studied within 6 hours after stroke onset. The relative CBV (relCBV) and CBF (relCBF) in the lesions were defined relative to the contralateral mirror regions. Results-In the brain regions with mild (relCBF Ն0.60), moderate (0.40ՅrelCBFϽ0.60), and severe (relCBF Ͻ0.40) hypoperfusion, the mean relCBV values were 1.29Ϯ0.31, 0.94Ϯ0.49, and 0.30Ϯ0.22, respectively. The relCBV was significantly elevated in the brain areas with mild hypoperfusion (PϽ0.001) and significantly reduced in the brain areas with severe hypoperfusion (PϽ0.001). The relCBF was significantly better than the relCBV in predicting the evolution of infarction (PϽ0.02). The probability of evolving infarction for the hypervolemic (relCBV Ͼ1.0) regions was significantly lower than that for hypovolemic (relCBV Ͻ1.0) regions in the relCBF range between 0.40 and 0.50 (PϽ0.02). Conclusions-In acute ischemic stroke within 6 hours of onset the CBV can be either increased, normal, or decreased, depending on the severity of hypoperfusion. The increased CBV has a protective effect on evolving infarction. Although the CBF is a better predictor of tissue outcome, the CBV measurement may help detect potentially salvageable brain tissue in the penumbra with compromised blood flow. (Stroke. 1999;30:800-806.)

“…[17][18][19] Lo et al 19 used CT and TC to estimate the time lag between a contralateral reference function and the pixel of interest, essentially an estimate of TT delay. This technique suffers from limitations similar to those of TT or TTP maps, discussed below.…”

Section: Discussionmentioning

confidence: 99%

Rapid Perfusion Abnormality Estimation in Acute Stroke With Temporal Correlation Analysis

Lee

et al. 2003

Background and Purpose-Determination of the presence or absence of ischemic penumbra through diffusion-perfusion mismatch requires rapid delineation of both abnormalities. Although singular value decomposition-based perfusion parameter estimation has offered valuable insights into the underlying cerebral hemodynamics, the associated postprocessing procedures have limited its widespread use. We explored the utility of a simple technique to define perfusion abnormality in acute stroke patients. Methods-Twenty acute stroke patients were studied. The MR dynamic contrast approach was used to obtain cerebral blood flow, cerebral blood volume, and mean transit time (MTT). Temporal correlation was used to correlate 4 reference functions-an arterial input function (AIF), a normal tissue function, a lesion function, and a venous output function-with dynamic contrast MR images, and correlation coefficients (CCs) were calculated pixel by pixel. In addition, chronic-state T2-weighted images were coregistered onto the images acquired acutely for assessing the sensitivity and specificity of CC-defined lesion. Results-Statistically significant differences in cerebral blood flow and MTT were found between CC-defined normal and abnormal tissues with all 4 reference functions used. When the final infarct volume was used as the gold standard, a similar sensitivity between MTT (78%) and AIF (76%) CC-defined lesion was obtained, whereas the specificity was higher for AIF (61%) than that obtained with MTT-defined lesion (52%). Conclusions-We explored CC maps as a simpler alternative of estimating perfusion abnormality, and results demonstrated the potential clinical utility of a correlation-based technique for estimating brain perfusion status. (Stroke.