Background and purpose
Recent Japanese EC-IC Bypass Trial (JET Study) showed that the EC-IC Bypass was beneficial for stroke prevention in patients with Stage2 hemodynamic cerebral ischemia determined by quantified CBF-SPECT imaging 1 . Stratification of hemodynamic cerebral ischemia was essential for patients' enrollment in this trial. However, standardization of quantified stratification of hemodynamic cerebral ischemia using CBF-SPECT imaging has not been established yet. In this paper, we evaluated newly developed two CBF-SPECT analysis as standardized techniques for improving measurement accuracy and judgment accuracy.
Methods
Twenty patients with atherothrombotic stroke were involved in this study. Using quantified CBF-SPECT imaging such as IMP-ARG method 2 , Stage2 hemodynamic cerebral ischemia was defined as CBF in the affected MCA territories less than 80% of mean CBF of normal subjects and vascular reserve (VR) [(acetazolamide-activated CBF - Resting CBF) / Resting CBF×100%] less than 10%. For improving measurement accuracy, Dual table ARG (DTARG) analysis was developed to provide same-day quantification of both resting CBF and acetazolamide-activated CBF using split dose of CBF tracer (IMP) and common arterial input function. For improving judgment accuracy, segmental extraction estimation (SEE) analysis 3 was introduced to present resting CBF, acetazolamide-activated CBF, VR, and stratification of hemodynamic cerebral ischemia unfolded pixel-by-pixel on the standardized brain surface images using 3-dimensional stereotactic surface projections (3D-SSP) technique 4 .
Results
Using DTARG method, both resting and acetazolamide-activated CBF-SPECT could be quantified pixel-by-pixel using dual table look-up method without an error of different input functions. Stage2 hemodynamic cerebral ischemia in symptomatic hemisphere was easily detected in comparison with two-day quantification of both resting CBF and acetazolamide-activated CBF in all patients. Using SEE analysis, severity of hemodynamic cerebral ischemia could be estimated from stereotactic and quantitative viewpoints based on standardized vascular territories without an arbitrary ROI analysis. Territories of Stage2 hemodynamic cerebral ischemia were displayed in 3D-SSP views in all patients.
Conclusion
Standardization of quantified stratification of hemodynamic cerebral ischemia using CBF-SPECT imaging will be important issue in decision-making of indication of EC-IC Bypass surgery for cerebral ischemia. Both DTARG method and SEE analysis could be clinically applied as standardized techniques to improve measurement accuracy and judgment accuracy.