Development of the automated Patlak plot method and its verification in clinical examples

The Patlak plot method is widely used in general clinical practice to calculate mean cerebral blood flow (mCBF) because it does not require arterial blood sampling and the procedure used is relatively simple. However, it has been pointed out that the calculation is affected by operator subjectivity and experience, and reproducibility is poor when the operator changes. The Patlak plot method consists of the following three procedures: (1) a region of interest (ROI) in the normal cerebral hemisphere is chosen to obtain the time-activity curve; (2) an ROI in the aortic arch is determined to obtain the time-activity curve; and (3) graphic analysis of the two time-activity curves is performed, and mCBF is determined from the slope of the graph. In this study, we automated all three of the above procedures, enabling analysis that is not affected by operator subjectivity or experience. Considering the verification result shown below: (1) automation of an ROI setup of a cerebral hemisphere and an aortic arch was possible in all examples; (2) the point of graphic analysis was set in the error range of 1% - 2% of straight line domains; (3) in comparison with the conventional method in 55 cases, the mean of absolute percentage error was 3.1±2.5%; (4) in 17 cases that did not accept a right-and-left difference in SPECT, the mean of absolute percentage error of right and left mCBF was 1.3±0.9%. It was thought that the processing algorithm was appropriate. Moreover, it was thought that the technique of graphic analysis proposed for this study served as an aid to dissolution of the “ambiguity” of the Patlak plot method.