Inoue Kazumasa, Sato Takashi, Kitamura Hideaki, Ito Masaaki, Tsunoda Yoshiyuki, Hirayama Akira, Kurosawa Hideo, Tanaka Takashi, Fukushi Masahiro, Moriyama Noriyuki, Fujii Hirofumi
Graduate School of Health Science, Tokyo Metropolitan University, Tokyo, Japan.
Ann Nucl Med. 2008 Jul;22(6):465-73. doi: 10.1007/s12149-007-0141-9. Epub 2008 Aug 1.
Improvement in the diagnostic accuracy of lymph node (LN) metastases of colorectal cancer by optimizing the reconstruction parameters was studied, including a phantom study and clinical studies.
In the experimental study, the contrast ratio was evaluated using a standard image quality phantom, changing the iteration number of ordered subsets expectation maximization algorithm from 2 to 6. In the clinical study, 89 patients with preoperative colorectal cancer who received 18F-2-deoxy-2-fluoro-D: -glucose positron emission tomography/computed tomography (PET/CT) were studied. Their LN metastases were visually assessed when systematically changing the iteration number, and the optimal iteration number was determined. After the appropriate cut-off value of maximum standardized uptake value was determined, the improvement of the diagnostic accuracy of LN metastases was evaluated for the proximal nodes and the distal ones using the reconstructed images with the optimal iteration number. This was compared with the conventional method that had an iteration number of 2.
In the phantom study, it was confirmed that the contrast ratio improved when the iteration number increased. In clinical evaluation, the optimal iteration number was determined to be 5 by visual assessment. When the cut-off value of 1.5 was used, which happened to be the best number, the sensitivity/specificity/accuracy improved from 52%/91%/72% to 77%/89%/83% for the proximal nodes, and from 63%/90%/84% to 91%85%/87% for the distal nodes, respectively.
When the iteration number of the reconstruction algorithm was optimized, the sensitivity of LN metastasis improved by more than 20%, and the accuracy exceeded 80%. Optimization of the image reconstruction parameters in the diagnosis of LN metastases using PET/CT is clinically important.
通过优化重建参数，研究提高结直肠癌淋巴结（LN）转移诊断准确性的方法，包括体模研究和临床研究。
在实验研究中，使用标准图像质量体模评估对比率，将有序子集期望最大化算法的迭代次数从2更改为6。在临床研究中，对89例术前结直肠癌患者进行了18F-2-脱氧-2-氟-D-葡萄糖正电子发射断层扫描/计算机断层扫描（PET/CT）检查。系统地改变迭代次数时，对其LN转移进行视觉评估，并确定最佳迭代次数。在确定最大标准化摄取值的合适截断值后，使用具有最佳迭代次数的重建图像评估近端和远端LN转移诊断准确性的提高情况。将其与迭代次数为2的传统方法进行比较。
在体模研究中，证实随着迭代次数增加，对比率提高。在临床评估中，通过视觉评估确定最佳迭代次数为5。当使用截断值1.5（恰好是最佳数值）时，近端淋巴结的敏感性/特异性/准确性分别从52%/91%/72%提高到77%/89%/83%，远端淋巴结的敏感性/特异性/准确性分别从63%/90%/84%提高到91%/85%/87%。
当重建算法的迭代次数优化后，LN转移的敏感性提高超过20%，准确性超过80%。在使用PET/CT诊断LN转移时优化图像重建参数具有重要临床意义。
