Medical Physics Department, University Hospital S. Orsola-Malpighi, Via Massarenti 9, 40138 Bologna, Italy.
Comput Math Methods Med. 2013;2013:103476. doi: 10.1155/2013/103476. Epub 2013 Apr 16.
In order to extract quantitative parameters from PET images, several physical effects such as photon attenuation, scatter, and partial volume must be taken into account. The main objectives of this work were the evaluation of photon attenuation in small animals and the implementation of two attenuation correction methods based on X-rays CT and segmentation of emission images. The accuracy of the first method with respect to the beam hardening effect was investigated by using Monte Carlo simulations. Mouse- and rat-sized phantoms were acquired in order to evaluate attenuation correction in terms of counts increment and recovery of uniform activity concentration. Both methods were applied to mice and rat images acquired with several radiotracers such as(18)F-FDG, (11)C-acetate, (68)Ga-chloride, and (18)F-NaF. The accuracy of the proposed methods was evaluated in heart and tumour tissues using (18)F-FDG images and in liver, kidney, and spinal column tissues using (11)C-acetate, (68)Ga-chloride, and (18)F-NaF images, respectively. In vivo results from animal studies show that, except for bone scans, differences between the proposed methods were about 10% in rats and 3% in mice. In conclusion, both methods provide equivalent results; however, the segmentation-based approach has several advantages being less time consuming and simple to implement.
为了从 PET 图像中提取定量参数，必须考虑几种物理效应，如光子衰减、散射和部分容积。这项工作的主要目标是评估小动物中的光子衰减，并实现基于 X 射线 CT 和发射图像分割的两种衰减校正方法。使用蒙特卡罗模拟研究了第一种方法对束硬化效应的准确性。为了评估计数增加和均匀活性浓度恢复方面的衰减校正，获取了小鼠和大鼠大小的体模。将这两种方法应用于用几种放射性示踪剂（如(18)F-FDG、(11)C-乙酸盐、(68)Ga-氯化物和(18)F-NaF）获得的小鼠和大鼠图像。使用(18)F-FDG 图像评估心脏和肿瘤组织中提出方法的准确性，使用(11)C-乙酸盐、(68)Ga-氯化物和(18)F-NaF 图像评估肝脏、肾脏和脊柱组织中的准确性。动物研究的体内结果表明，除了骨扫描外，这两种方法在大鼠中的差异约为 10%，在小鼠中的差异约为 3%。总之，这两种方法提供了等效的结果；然而，基于分割的方法具有几个优点，即耗时更少且易于实现。
