Matsumoto Keiichi, Matsuura Hajime, Minota Eiri, Sakamoto Setsu, Nakamoto Yuji, Senda Michio
Department of Image-based Medicine, Institute of Biomedical Research and Innovation.
Nihon Hoshasen Gijutsu Gakkai Zasshi. 2004 Nov;60(11):1564-73. doi: 10.6009/jjrt.kj00003326581.
The standardized uptake value (SUV) is a relative measure of tracer uptake in tissue used in (18)F-FDG PET. However, the quality of ordered subset expectation maximization (OS-EM) images is sensitive to the number of iterations, because a large number of iterations leads to images with checkerboard noise. The main advantage of data acquisition in the three-dimensional (3D) mode is the high sensitivity to better exploit the intrinsic spatial resolution and the lower injection dose given to patients. In the 3D mode, the scatter fraction is higher, and, for a given administered dose, the random fraction is higher than that in the two-dimensional mode, which implies that correction methods need to be more accurate. Moreover, in clinical oncology (18)F-FDG PET studies, patients have a wide variety of body shapes and sizes, which may impact image statistics. Consequently, it is necessary to make constant the acquisition (true) counts. The purpose of this study was to optimize injection dose and acquisition time in consideration of body mass index (BMI) for 3D whole-body (18)F-FDG PET.
A dedicated PET scanner, SIEMENS ECAT EXACT HR(+), was used to scan images of clinical data. The injection dose for BMI of <14-19, 19-22, 22-25, and 25< (kg/m(2)) were, 92.5 MBq, 111.0 MBq, 129.5 MBq, and 148.0 MBq, respectively. The emission scan time per bed position for BMI of <14-19, 19-22, 22-25, and >25 (kg/m(2)) were, 120, 120, 180, and 240 sec, respectively. A total of 20 patient subjects were evaluated as to true counts per bin (T/bin) of sinogram data and measured activity concentrations for the region of interest in the liver section.
T/bin was stable using an optimized protocol that took into consideration the BMI for any type of body morphology. The overall coefficient of variation was 7.27% for radioactivity concentration. Additionally, Gaussian filtering (8 mm FWHM) after reconstruction by the OS-EM method provided stable SUV values even when the iteration number was increased 30 times over.
Optimization of injection dose and acquisition time indicated that BMI was a clinically useful acquisition protocol for 3D whole-body (18)F-FDG PET.
标准化摄取值（SUV）是用于（18）F-FDG PET的组织中示踪剂摄取的相对测量值。然而，有序子集期望最大化（OS-EM）图像的质量对迭代次数敏感，因为大量迭代会导致图像出现棋盘格噪声。三维（3D）模式下的数据采集的主要优点是对更好地利用固有空间分辨率具有高灵敏度，并且给患者的注射剂量较低。在3D模式下，散射分数较高，并且对于给定的给药剂量，随机分数高于二维模式，这意味着校正方法需要更准确。此外，在临床肿瘤学（18）F-FDG PET研究中，患者具有各种各样的体型和尺寸，这可能会影响图像统计。因此，有必要使采集（真实）计数恒定。本研究的目的是考虑体重指数（BMI）来优化3D全身（18）F-FDG PET的注射剂量和采集时间。
使用专用PET扫描仪SIEMENS ECAT EXACT HR(+)扫描临床数据图像。BMI为<14-19、19-22、22-25和25<（kg/m²）时的注射剂量分别为92.5 MBq、111.0 MBq、129.5 MBq和148.0 MBq。BMI为<14-19、19-22、22-25和>25（kg/m²）时每个床位的发射扫描时间分别为120、120、180和240秒。总共评估了20名患者受试者的正弦图数据的每箱真实计数（T/bin）以及肝脏切片感兴趣区域的测量活性浓度。
使用考虑了任何体型的BMI的优化方案，T/bin是稳定的。放射性浓度的总体变异系数为7.27%。此外，即使迭代次数增加30倍，通过OS-EM方法重建后进行高斯滤波（8 mm半高宽）也能提供稳定的SUV值。
注射剂量和采集时间的优化表明，BMI是3D全身（18）F-FDG PET的一种临床上有用的采集方案。
