Department of Diagnostic Radiology, The University of Hong Kong, Hong Kong.
Institute of Diagnostic and Interventional Radiology, University Hospital of Zurich, Switzerland.
Korean J Radiol. 2020 Feb;21(2):218-227. doi: 10.3348/kjr.2019.0232.
This study aimed to find the optimal number of b-values for intravoxel incoherent motion (IVIM) imaging analysis, using simulated and data from cervical cancer patients.
Simulated data were generated using literature pooled means, which served as reference values for simulations. data from 100 treatment-naïve cervical cancer patients with IVIM imaging (13 b-values, scan time, 436 seconds) were retrospectively reviewed. A stepwise b-value fitting algorithm calculated optimal thresholds. Feed forward selection determined the optimal subsampled b-value distribution for biexponential IVIM fitting, and simplified IVIM modeling using monoexponential fitting was attempted. IVIM parameters computed using all b-values served as reference values for data.
In simulations, parameters were accurately estimated with six b-values, or three b-values for simplified IVIM, respectively. data showed that the optimal threshold was 40 s/mm² for patients with squamous cell carcinoma and a subsampled acquisition of six b-values (scan time, 198 seconds) estimated parameters were not significantly different from reference parameters (individual parameter error rates of less than 5%). In patients with adenocarcinoma, the optimal threshold was 100 s/mm², but an optimal subsample could not be identified. Irrespective of the histological subtype, only three b-values were needed for simplified IVIM, but these parameters did not retain their discriminative ability.
Subsampling of six b-values halved the IVIM scan time without significant losses in accuracy and discriminative ability. Simplified IVIM is possible with only three b-values, at the risk of losing diagnostic information.
本研究旨在通过模拟数据和宫颈癌患者的数据，找到最佳的体素内不相干运动（IVIM）成像分析的 b 值数量。
使用文献汇总均值生成模拟数据，作为模拟的参考值。回顾性分析了 100 例未经治疗的宫颈癌患者的 IVIM 成像数据（13 个 b 值，扫描时间为 436 秒）。采用逐步 b 值拟合算法计算最佳阈值。前馈选择确定了双指数 IVIM 拟合的最佳子采样 b 值分布，并尝试了使用单指数拟合的简化 IVIM 建模。使用所有 b 值计算的 IVIM 参数作为 数据的参考值。
在模拟中，分别使用 6 个 b 值或简化 IVIM 的 3 个 b 值可以准确估计参数。数据显示，鳞状细胞癌患者的最佳阈值为 40 s/mm²，采集 6 个 b 值（扫描时间为 198 秒）的子样本可以得到与参考参数无显著差异的参数（个体参数误差率小于 5%）。腺癌患者的最佳阈值为 100 s/mm²，但无法确定最佳子样本。无论组织学亚型如何，简化 IVIM 仅需要 3 个 b 值，但这些参数不再具有鉴别能力。
在不显著降低准确性和鉴别能力的情况下，子采样 6 个 b 值可将 IVIM 扫描时间减半。仅使用 3 个 b 值可实现简化 IVIM，但可能会丢失诊断信息。
