A New Regression Equation for super(123)I-IMP Non-invasive Cerebral Blood Flow Measurement Using the Graph Plot Method

Purpose: A graph plot (GP) methodusing 123I-N-isopropyl-p-iodoamphetamine (123I-IMP) has been proposed as a simple andnon-invasive estimation of quantitative cerebral bloodflow (CBF). A regression equation for the GP methodwas estimatedby the data of resting state. Therefore, the accuracy of CBF values in high flow range may be an underestimated possibility in this method.The aim of this study was to formulate a new regression equation for the GP methodby the data of resting state andacetazolamide (ACZ) challenge, andto clarify the accuracy of it. Methods: The images of 26 consecutive patients who underwent both 123I-IMP chest radioisotope-angiography (RIA) andsingle photon emission computedtomography (SPECT) examinations were usedto construct the new regression equation. Examinations of the resting state andACZ challenge were performedin different days. All patients were analyzedby both the GP methodandautoradiography (ARG) methodwhich is the conventional examination with the one-point arterial bloodsampling. A linear regression equation between the index of the input function was obtainedby the GP methodandCBF value of ARG. The linear regression equation basedon the resting data was comparedwith the equation basedon the resting andACZ challenge (rest+stress) data. Results: Goodliner correlation was obtainedbetween the index of the input function obtainedby the GP methodandCBF value of the ARG methodin the rest+stress state (y=2.75x+15.1, r=0.78). In contrast, correlation results between the index of the input function obtainedby the GP methodandCBF value of the ARG methodin the resting state was expressed as y=2.28x+18.4, r=0.54 rCBF values basedon the resting data was 20% underestimated in the high flow range comparedwith values basedon the rest+stress data. Conclusion: The new linear regression equation for the GP methodis useful for clinical study. Key words: non-invasive cerebral blood flow measurement method, graph plot (GP), autoradiography (ARG), 123I-N-isopropyl-p-iodoamphetamine (123I-IMP)