Hashimoto Naoki, Morita Keishin, Tsutsui Yuji, Himuro Kazuhiko, Baba Shingo, Sasaki Masayuki
Department of Health Sciences, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan; and.
Division of Radiology, Department of Medical Technology, Kyushu University, Fukuoka, Japan.
J Nucl Med Technol. 2018 Sep;46(3):268-273. doi: 10.2967/jnmt.117.204735. Epub 2018 Mar 29.
Recent advancements in clinical PET/CT scanners have improved the detectability of small lesions. However, the ideal reconstruction parameters for detecting small lesions have not yet been sufficiently clarified. The purpose of this study was to investigate the detectability of subcentimeter spheres using a clinical PET/CT scanner. We used a clinical PET/CT scanner to obtain the data of a National Electrical Manufacturers Association body phantom consisting of 6 small spheres (inner diameters, 4.0, 5.0, 6.2, 7.9, 10, and 37 mm) containing F solution. The background activity was 2.65 kBq/mL, and the sphere-to-background ratio was 8. The PET data obtained for 2 and 120 min were reconstructed using ordered-subsets expectation maximization (OSEM), OSEM + point-spread function (PSF), and OSEM + time-of-flight (TOF) with voxel sizes of 2.04 × 2.04 × 2.00 mm (2-mm voxels) and 4.07 × 4.07 × 3.99 mm (4-mm voxels). A gaussian filter was not used. The image quality was evaluated by visual assessment, as well as by physical assessment of the detectability index and recovery coefficients. According to the visual assessment, the detectability of the spheres improved using TOF and a longer acquisition. Using the OSEM+TOF model, the smallest visually detected spheres were 5 mm in diameter with a 120-min acquisition and 6 mm in diameter with a 2-min acquisition. According to physical assessment, the detectability of spheres 10 mm or smaller using the OSEM+TOF image was superior to that using the OSEM image. In addition, the detectability of each hot sphere and recovery coefficient with 2-mm voxels was superior to that with 4-mm voxels. Although OSEM+PSF images showed less background noise, detectability and the recovery coefficient were not improved for spheres 8 mm or smaller. The TOF model with 2-mm voxels improved the detectability of subcentimeter hot spheres on a clinical PET/CT scanner.
临床正电子发射断层扫描/计算机断层扫描（PET/CT）扫描仪的最新进展提高了小病灶的可检测性。然而，用于检测小病灶的理想重建参数尚未得到充分阐明。本研究的目的是使用临床PET/CT扫描仪研究亚厘米级球体的可检测性。我们使用临床PET/CT扫描仪获取了一个美国国家电气制造商协会（National Electrical Manufacturers Association）体模的数据，该体模由6个含有氟溶液的小球体（内径分别为4.0、5.0、6.2、7.9、10和37毫米）组成。背景活度为2.65 kBq/mL，球体与背景的比值为8。使用有序子集期望最大化（OSEM）、OSEM + 点扩散函数（PSF）和OSEM + 飞行时间（TOF）重建了采集2分钟和120分钟获得的PET数据，体素大小分别为2.04×2.04×2.00毫米（2毫米体素）和4.07×4.07×3.99毫米（4毫米体素）。未使用高斯滤波器。通过视觉评估以及对可检测性指数和恢复系数的物理评估来评价图像质量。根据视觉评估，使用TOF和更长的采集时间可提高球体的可检测性。使用OSEM+TOF模型，在采集120分钟时，视觉上可检测到的最小球体直径为5毫米，在采集2分钟时为6毫米。根据物理评估，使用OSEM+TOF图像对10毫米或更小的球体的可检测性优于使用OSEM图像。此外，2毫米体素的每个热球体的可检测性和恢复系数优于4毫米体素。尽管OSEM+PSF图像显示出较少的背景噪声，但对于8毫米或更小的球体，可检测性和恢复系数并未提高。具有2毫米体素的TOF模型提高了临床PET/CT扫描仪上亚厘米级热球体的可检测性。
