Objective: The brain uptake ratio (BUR) method for the (99m)Tc-ECD SPECT, a non-invasive measurement method of rCBF, has been used in clinical practice in Japan, because it is simple to use. However, the accuracy of this method is limited, as it has problems in the determination of input function and the regression equation. The purpose of this study is to improve the BUR method by reconstructing the determination process of the input function and regression equation based on measurement of the rCBF by H (2) (15) O PET.
Method: The input function was obtained by setting the region of interest on the ascending aorta instead of the aortic arch. The 3DSRT algorithm was used to obtain the anatomically standardized rCBF, and developed a semi-automatic analyzing software using C++ in order to stabilize the repeatability of the improved BUR (IBUR) method. The regression equation for the IBUR method was obtained by the H (2) (15) O PET rCBFs in 15 patients with the arterial blood sampling method. All the measurements in this study were performed with the patient in the resting state.
Result: A good correlation was observed between the rCBF values measured by H (2) (15) O PET and the regional BURs measured by the IBUR method (r = 0.86, p < 0.0001). The rCBF values were calculated for only 5 min using a semi-automatic analyzing software.
Conclusion: The BUR method was improved by changing the location of the input function from the aortic arch to the ascending aorta based on arterial blood flow dynamics, and reconstructing regression equation based on the rCBF values obtained using H (2) (15) O PET. This finding indicates the potential clinical usefulness of this method.