Hoffman E J, Huang S C, Phelps M E
J Comput Assist Tomogr. 1979 Jun;3(3):299-308. doi: 10.1097/00004728-197906000-00001.
The effect of object size on the capability of positron emission computed tomography to measure isotope concentrations in a cross section was studied. The relationship between the apparent isotope concentration in an image and the true concentration was measured as a function of object size for three instrument resolutions and four convolution filters. The relationship between image size and object size was also measured under the same conditions. Depression of apparent isotope concentration in an image for objects equal in size to the instrument resolution (FWHM) was significant (50% for a cylinder and 25% for a bar). For objects larger than 1.0 FWHM, accurate object sizes can be estimated from the images. Thus, reasonably accurate and practical schemes of compensation for object size effects can be implemented for objects larger than 1.0 FWHM. Accuracy in quantitating isotope concentrations in smaller objects is seriously compromised by the loss of sensitivity to the object size and the large correction factors required to compensate for instrument response. The results of the measurements were found to be in good agreement with theoretical predictions for ideal systems of comparable resolution.
研究了物体大小对正电子发射计算机断层扫描在横截面中测量同位素浓度能力的影响。针对三种仪器分辨率和四种卷积滤波器，测量了图像中表观同位素浓度与真实浓度之间的关系，该关系是物体大小的函数。在相同条件下，还测量了图像大小与物体大小之间的关系。对于大小与仪器分辨率（半高宽）相等的物体，图像中表观同位素浓度的降低很显著（圆柱体为50%，棒状体为25%）。对于大于1.0个半高宽的物体，可以从图像中估计出准确的物体大小。因此，对于大于1.0个半高宽的物体，可以实施合理准确且实用的物体大小效应补偿方案。较小物体中同位素浓度定量的准确性因对物体大小敏感性的丧失以及补偿仪器响应所需的大校正因子而严重受损。测量结果与具有可比分辨率的理想系统的理论预测结果吻合良好。
