Shishido Hiroki, Otsuka Nobuaki, Tominaga Takahiro
Medical Engineering and Technology, Graduate Course in Integrated Human Sciences, Hiroshima International University.
Nihon Hoshasen Gijutsu Gakkai Zasshi. 2006 Jun 20;62(6):855-62. doi: 10.6009/jjrt.62.855.
The purpose of this study was to determine the best bed overlaps in PET/CT 3D acquisition to reconstruct a transverse image with uniform quality not depending on axial slice position. First, the value of the image contrast ratio, non-uniformity (NU) value, and coefficient of variation (COV) were examined in the image of a cylindrical phantom at each slice position. The image-contrast ratio was almost constant in all slice images, and the NU value and COV were also constant in the slice images up to 13 and 19 slices from the center, respectively, but these values increased with closeness to the edge of the detector. Secondly, COV and image contrast ratios at different sizes of (18)F-FDG concentration (phi 19 mm, phi 16 mm, phi 13 mm, phi 10 mm) were examined in the case of overlapping the bed frame with 11, 15, and 21 slices in acquiring data in 3D mode. In 21 and 15 slices overlapping in acquisition, the image contrast ratios for all concentrations were greater than 0.13, which was the threshold image contrast ratio needed to identify FDG concentration from the background image with naked eye scanning under our conditions. However, in 11 slices with overlapping acquisition, the image-contrast ratio for a phi 10 mm concentration were close to or less than 0.13 in the all slice images. As a result, 15 overlapping slices was a reasonable minimum number of slices to identify a phi 10 mm (18)F-FDG concentration while maintaining the image quality in PET/CT 3D acquisition in our institution.
本研究的目的是确定PET/CT三维采集中最佳的床位重叠情况，以重建质量均匀且不依赖于轴向切片位置的横向图像。首先，在圆柱形体模图像的每个切片位置检查图像对比度、不均匀性（NU）值和变异系数（COV）。所有切片图像中的图像对比度几乎恒定，在距中心分别达13层和19层的切片图像中，NU值和COV也恒定，但这些值随着靠近探测器边缘而增加。其次，在以三维模式采集数据时，研究了床架分别与11层、15层和21层重叠的情况下，不同大小（18）F-FDG浓度（19mm、16mm、13mm、10mm）时的COV和图像对比度。在采集时15层和21层重叠的情况下，所有浓度的图像对比度均大于0.13，这是在我们的条件下通过肉眼扫描从背景图像中识别FDG浓度所需的阈值图像对比度。然而，在采集时11层重叠的情况下，在所有切片图像中，10mm浓度的图像对比度接近或小于0.13。结果，在我们机构的PET/CT三维采集中，15层重叠切片是在保持图像质量的同时识别10mm（18）F-FDG浓度的合理最小切片层数。
