Sugisawa Koichi, Ichikawa Katsuhiro, Minamishima Kazuya, Hasegawa Masakazu, Yamada Yoshitake, Jinzaki Masahiro
Graduate School of Medical Science, Kanazawa University.
Department of Radiological Technology, Keio University Hospital.
Nihon Hoshasen Gijutsu Gakkai Zasshi. 2017;73(8):636-645. doi: 10.6009/jjrt.2017_JSRT_73.8.636.
The purpose of this study was to evaluate the effect of the virtual monochromatic spectral images (VMSI) and the model-based iterative reconstruction (MBIR) images, to evaluate the influence of the aperture size (40- and 20-mm beam) on renal pseudoenhancement (PE) compared with the filtered back projection (FBP) images.
The renal compartment-CT phantom was filled with iodinated contrast material diluted to the attenuation of 180 Hounsfield units (HU) at 120 kV. The water-filled spherical structures, which simulate cyst, were inserted into the renal compartment. Those diameters were 7, 15 and 25 mm. These were scanned by conventional mode (helical scan, 120 kV-FBP) and dual energy mode. 70 keV-VMSI were reconstructed from the dual energy mode, and MBIR images were reconstructed from conventional mode at 40- and 20-mm aperture. Additionally, the phantom was scanned using non-helical mode with 20-mm aperture, and FBP images were reconstructed. The CT value of the PE for cyst areas was measured for these images.
The CT values of the cysts were 20.0-14.3 HU on the FBP images, 12.8-12.7 HU on the 70 keV-VMSI (PE-inhibition ratio was 36.0-11.2%) and 16.2-14.0 HU on the MBIR images (19.0-2.1%), respectively, at 40-mm aperture. The PE-inhibition ratio scanned by 20-mm aperture was improved by 28.0% with FBP, 32.8% with 70 keV-VMSI and 29.6% with MBIR compared with 40-mm aperture. One of the FBP images with non-helical mode was 11.6 HU.
The best CT technique to minimize PE was the combination of 70 keV-VMSI and 20-mm aperture.
本研究旨在评估虚拟单色光谱图像（VMSI）和基于模型的迭代重建（MBIR）图像的效果，与滤波反投影（FBP）图像相比，评估孔径大小（40毫米和20毫米束）对肾脏伪强化（PE）的影响。
肾脏分区CT体模填充稀释至120 kV时衰减为180亨氏单位（HU）的碘化造影剂。将模拟囊肿的充满水的球形结构插入肾脏分区。其直径分别为7毫米、15毫米和25毫米。这些结构通过传统模式（螺旋扫描，120 kV - FBP）和双能模式进行扫描。从双能模式重建70 keV - VMSI，从传统模式在40毫米和20毫米孔径下重建MBIR图像。此外，使用20毫米孔径的非螺旋模式扫描体模，并重建FBP图像。测量这些图像中囊肿区域的PE的CT值。
在40毫米孔径下，囊肿在FBP图像上的CT值为20.0 - 14.3 HU，在70 keV - VMSI上为12.8 - 12.7 HU（PE抑制率为36.0 - 11.2%），在MBIR图像上为16.2 - 14.0 HU（19.0 - 2.1%）。与40毫米孔径相比，20毫米孔径扫描的PE抑制率在FBP下提高了28.0%，在70 keV - VMSI下提高了32.8%，在MBIR下提高了29.6%。非螺旋模式的一张FBP图像为11.6 HU。
将70 keV - VMSI和20毫米孔径相结合是使PE最小化的最佳CT技术。
