Comparison of EPISTAR and T₂*-weighted gadolinium-enhanced perfusion imaging in patients with acute cerebral ischemia

Purpose: To compare echo-planar imaging with signal targeting and alternating radiofrequency (EPISTAR), an arterial spin-labeling technique, to a T₂*-weighted gadolinium-enhanced (T₂*-WGE) MR perfusion technique for the evaluation of acute cerebrovascular disease. Method: Twenty-one EPISTAR and T₂*-WGE perfusion studies were performed on 18 patients with the clinical diagnosis of acute stroke (12 men, 6 women, age range 34 to 89 years, mean age 68 years). For qualitative analysis, perfusion studies of both techniques were grouped into categories (hyperper-fusion, normal perfusion, delayed perfusion, or absent perfusion) and compared with a Wilcoxon signed rank test. Quantitative analysis was performed using signal intensity measurements in a region of interest that was defined by diffusion- weighted imaging abnormalities. These signal intensity measurements were compared with a mirror region in the contralateral unaffected hemisphere. Signal intensity ratios (infarcted region versus the unaffected contralateral region) were calculated and compared using a paired t test. Results: Qualitative analysis demonstrated agreement between the two techniques in 17 of 21 studies (hyperfusion, n = 3 patients; normal perfusion, n = 3; delayed perfusion, n = 4; and absent perfusion, n = 7). In four studies, the two techniques disagreed when EPISTAR demonstrated absent and T₂*-WGE perfusion demonstrated delayed perfusion (p > 0.05). Quantitative analysis revealed a mean signal intensity ratio of 0.73 ± 0.79 for the T₂*-WGE perfusion technique and 0.69 ± 0.68 for the EPISTAR technique (p > 0.05). Conclusion: The noninvasive EPISTAR technique can assess perfusion abnormalities similarly to the T₂*-WGE perfusion technique and may provide a valuable alternative in the diagnosis of acute stroke patients. Differences between the two techniques can be explained by the applied inflow times in the EPISTAR technique.