Hoshino Takashi, Ichikawa Katsuhiro, Terakawa Syouichi, Katsuma Yasuyuki, Fujimura Ichirou, Ueda Yuuji, Miura Youhei, Nishimura Kenji
Department of Radiology, Ishinkai Yao General Hospital.
Nihon Hoshasen Gijutsu Gakkai Zasshi. 2012;68(12):1624-30. doi: 10.6009/jjrt.2012_jsrt_68.12.1624.
The purpose of this study was to evaluate the effect of an iterative reconstruction method (IR) on shape reproducibility in three-dimensional (3D) computed tomography images. We used an IR (sinogram-affirmed iterative reconstruction: SAFIRE) implemented in a 64-channel multi slice computed tomography system (Siemens, SOMATOM Definition AS). We scanned a simulated vessel phantom with 180-HU vessel contrast at various radiation doses and reconstructed axial images of filtered back projection (FBP) and SAFIRE. Then we reconstructed multi-planar reconstruction (MPR) and volume rendering (VR) images from the axial images. Roundness was evaluated from MPR images and vessel surface roughness was evaluated from pixel value profiles of a vessel in VR images and visual evaluation by radiological technologists. In comparison on equivalent dose, the roundness and roughness were improved with increase of SAFIRE strength level. However, in comparison on equivalent noise (standard deviation: SD) of axial images, SAFIRE strength levels of 2 to 5 were significantly inferior to FBP (p<0.05). SAFIRE strength of 1 with a dose reduction of 19% maintained the shape reproducibility in all evaluations. Therefore, it would be not appropriate to use the SD of axial image as index for the dose reduction rate determination of 3D-CT images.
本研究的目的是评估迭代重建方法（IR）对三维（3D）计算机断层扫描图像中形状再现性的影响。我们使用了一种在64通道多层计算机断层扫描系统（西门子，SOMATOM Definition AS）中实现的IR（正弦图确认迭代重建：SAFIRE）。我们在不同辐射剂量下用180 HU的血管造影剂扫描了一个模拟血管体模，并重建了滤波反投影（FBP）和SAFIRE的轴向图像。然后我们从轴向图像重建了多平面重建（MPR）和容积再现（VR）图像。从MPR图像评估圆度，并从VR图像中血管的像素值剖面和放射技师的视觉评估来评估血管表面粗糙度。在等效剂量比较中，随着SAFIRE强度水平的增加，圆度和粗糙度得到改善。然而，在轴向图像的等效噪声（标准差：SD）比较中，SAFIRE强度水平2至5明显低于FBP（p<0.05）。SAFIRE强度为1且剂量降低19%在所有评估中均保持了形状再现性。因此，将轴向图像的SD用作确定3D-CT图像剂量降低率的指标是不合适的。
