2020 年 76 巻 2 号 p. 193-202
Specific binding ratio (SBR) is mainly used as a quantitative index of dopamine transporter scintigraphy, although it was reported that standardized uptake value (SUV) is useful for clinical diagnosis in recent years. The aim of this study is to evaluate whether xSPECT is useful for SUV in dopamine transporter scintigraphy. xSPECT is a recently developed, high-resolution image reconstruction technique that transforms single photon emission computed tomography (SPECT) to a computed tomography (CT) coordinate system. Furthermore, low-penetration high-resolution (LPHR), which there has been no previous physical evaluation report was also evaluated. The radioactive concentration of the image with xSPECT is automatically calculated by the periodic sensitivity calibration and one volume sensitivity calibration. In the case of images with conventional reconstruction methods as filtered back projection (FBP) and ordered subset expectation maximization (OSEM), the calibration factor related to the photon count and radioactive concentration was calculated from measuring a cylinder phantom filled with Iodine-123. Radioactive concentrations of the SUV factor were measured by SPECT data acquisition with the striatal phantom in various conditions. Radioactive concentrations with conventional reconstruction methods had a lower value (for example, with FBP it was 7.53 kBq/ml, with OSEM it was 7.22 kBq/ml) compared to the actual measurement value, although that with xSPECT (12.45 kBq/ml) got close to the actual measurement value (14.68 kBq/ml). LPHR showed an approximation to low-energy high-resolution (LEHR) in terms of spatial resolution and scatter fraction estimated from energy windows. The quantitative accuracy of radioactive concentration was the highest under xSPECT.
