PET图像中球形病灶的部分容积效应及其影响因素

依据形成部分容积效应的理论，由计算机模拟球形病灶（直径2～30 mm）位于各种背景（背景与病灶强度之比为0～0.7）中时，PET设备（分辨率3～15 mm）的成像实验。计算模拟图像中病灶的像素最大值、平均值及半高宽，由此探讨球形病灶PET成像的部分容积效应与相关影响因素间的关系，为进一步建立部分容积效应校正方法提供依据。结果表明：对于任一分辨率和背景强度，图像上病灶信号强度的最大值及平均值随病灶直径的增大而呈S形增加；对于任一病灶直径和背景强度，病灶强度的最大值及平均值随分辨率的增大而呈倒S形减小；对于任一病灶直径和分辨率，病灶强度的最大值及平均值随背景强度线性增加，以背景为基点时，高出背景的病灶强度（最大值、平均值）与相应病灶真值之比不随背景强度变化；对任一病灶直径和分辨率，病灶半高宽不随背景强度变化；当病灶直径大于分辨率时，病灶半高宽与其真实直径很接近，但随分辨率变差，其接近程度也变差；当病灶直径小于分辨率时，病灶半高宽基本不再随直径变小而变小，而是基本等于空间分辨率，并保持不变。

Partial Volume Effect and Its Influence Factors for Sphere Lesion PET Images

To investigate the partial volume effect (PVE) and its influence factors for sphere lesion positron emission tomography (PET) images and provide the basis for PVE correction, the computer simulation experiments for PET imaging were performed. According to the theory of PVE formation, PET images of the sphere lesions with diameter of 2.30 mm were simulated with computer program in the ratio of background to lesion of 0-0.7 under system resolution of 3.15 mm. The maximum and the average pixel values and the width of the lesion images were calculated. The results show that the maximum and average pixel values increase with the lesion diameter in S shape under every system resolution and background. The maximum and average pixel values decrease in inverse S shape with the increasing of the system resolution under every lesion diameter and background. The maximum and average pixel values linearly increase with the increasing of background under every lesion diameter and system resolution. The width of the lesion image is independent of the background under every lesion diameter and system resolution. The FWHM of the lesion image is close to the lesion diameter for the lesion which size is larger than system resolution and the difference increases with the system resolution value, it doesn’t change with the lesions which size is smaller than system resolution and it is equal to the system resolution.