Hosokawa Shota, Inoue Kazumasa, Kano Daisuke, Shimizu Fuminori, Koyama Kazuya, Nakagami Yoshihiro, Muramatsu Yoshihisa, Fukushi Masahiro
Department of Radiological Sciences, Graduate School of Human Health Sciences, Tokyo Metropolitan University, 7-2-10 Higashiogu, Arakawa-ku, Tokyo, 116-8551, Japan.
Department of Radiation Oncology, National Cancer Center Hospital East, 6-5-1 Kashiwanoha, Kashiwa, Chiba, 277-8577, Japan.
Radiol Phys Technol. 2017 Jun;10(2):204-212. doi: 10.1007/s12194-016-0386-x. Epub 2016 Dec 28.
Whereas Monte Carlo (MC) simulation is widely utilized in estimation of the scatter component, a simulation model which can calculate the scatter fraction (SF) of each patient is needed for making an accurate image quality assessment for clinical PET images based on the noise equivalent count. In this study, an MC simulation model was constructed which can calculate the SF for various phantoms. We utilized the Geant4 toolkit based on MC simulation to make a model of a PET scanner with a scatter phantom, and SFs calculated with this model were compared with the SF (SF: 44%) measured with use of an actual PET scanner. Additionally, the SF values for an anthropomorphic phantom were calculated from its voxel phantom. Furthermore, we evaluated the impact on the SF due to the difference in the source distribution inside the phantom. The SF calculated from the scatter phantom in the MC simulation was 44%, the same as the SF value. The average SF for the anthropomorphic phantom was 41%, but there was a maximum of 14 percentage points difference between each scan range, and the maximum difference in the SF was 8 percentage points for the difference in the source distribution. We constructed an MC simulation model which can calculate SFs for various phantoms. The SF was confirmed to be affected significantly by the source distribution. We judged that the actually measured SF obtained from the PET scanner with the scatter phantom was not suitable for the assessment of the quality of all patient images.
虽然蒙特卡罗（MC）模拟在散射分量估计中被广泛应用，但为了基于噪声等效计数对临床PET图像进行准确的图像质量评估，需要一个能够计算每个患者散射分数（SF）的模拟模型。在本研究中，构建了一个可以计算各种体模SF的MC模拟模型。我们利用基于MC模拟的Geant4工具包制作了一个带有散射体模的PET扫描仪模型，并将用该模型计算的SF与使用实际PET扫描仪测量的SF（SF：44%）进行了比较。此外，从体素体模计算出了仿真人体体模的SF值。此外，我们评估了体模内源分布差异对SF的影响。MC模拟中从散射体模计算出的SF为44%，与SF值相同。仿真人体体模的平均SF为41%，但每个扫描范围之间的最大差异为14个百分点，源分布差异导致的SF最大差异为8个百分点。我们构建了一个可以计算各种体模SF的MC模拟模型。证实SF受源分布的显著影响。我们判断，从带有散射体模的PET扫描仪获得的实际测量SF不适用于评估所有患者图像的质量。
