Department of Radiology, Changhai Hospital of Shanghai, The Second Military Medical University, No.168 Changhai Road, Shanghai, 200433, China.
Cancer Imaging. 2018 Nov 15;18(1):43. doi: 10.1186/s40644-018-0177-1.
To explore the effect of b-value distributions on the repeatability and diagnostic performance of the ADC value in rectal cancer patients using multiple b-values and mono-exponential model diffusion-weighted imaging (DWI).
Thirty-two preoperative rectal cancer patients, without receiving neoadjuvant therapy, were scanned on a 3 Tesla magnetic resonance imaging scanner using DWI with 10 b-values ranging from 0 to 2000 s/mm. The apparent diffusion coefficient (ADC) value was calculated using a mono-exponential model and 31 b-value combinations consisting of 2 to 10 b-values were explored. Regions of interest with the maximum cross-sectional tumour size were outlined on the ADC map by two independent observers. Intraclass correlation coefficients (ICC), coefficient of variation (CV), and Bland-Altman plots between the two observers were calculated and evaluated to determine repeatability. Areas under receiver operating characteristic curves (AUCs) were evaluated for rectal cancer characterization. Correlations between the mean ADC values and T stage were assessed using the Spearman correlation coefficient (ρ). α (= ICC + AUC + |ρ|- CV - |bias|) was defined and used to assess the optimal b-value distribution.
Postoperative pathology tests revealed 4 patients with T1, 10 patients with T2, and 18 patients with T3 stages. There were no significant difference in age and sex between the two groups (T1-2 vs. T3). Excellent reproducibility was observed for ADC values between two observers with ICC and CV values ranging from 0.920 to 0.998, and 1.475 to 5.568%, respectively. The mean percent difference and ρ between the paired measurements was ranged from - 2.7 to 1.2% and from - 0.759 to - 0.407, respectively. The b-value combinations with the top three α values were b(0, 1000 s/mm), b(500, 1500, 2000 s/mm) and b(100, 1000, 1500 s/mm) for α = 2.581, 2.571 and 2.569, respectively.
The number of b-values and their distributions influenced the repeatability of the ADC values and their diagnostic performance. The optimal b-value combination was 0 and 1000 s/mm for DWI examination of rectal cancer patients.
本研究旨在探讨使用多 b 值和单指数模型扩散加权成像（DWI）时，b 值分布对直肠癌患者 ADC 值重复性和诊断性能的影响。
32 例术前直肠癌患者未接受新辅助治疗，在 3.0T 磁共振成像扫描仪上进行 DWI 扫描，b 值范围为 0 至 2000 s/mm，共 10 个。使用单指数模型计算表观扩散系数（ADC）值，并探讨了由 2 至 10 个 b 值组成的 31 种 b 值组合。两位独立观察者在 ADC 图上勾画最大肿瘤横截面积的感兴趣区。计算两位观察者之间的组内相关系数（ICC）、变异系数（CV）和 Bland-Altman 图，并进行评估，以确定重复性。评估受试者工作特征曲线（ROC）下面积（AUC）以用于直肠癌特征描述。使用 Spearman 相关系数（ρ）评估平均 ADC 值与 T 分期之间的相关性。定义了α（= ICC+AUC+|ρ|-CV-|偏倚|）并用于评估最佳 b 值分布。
术后病理检查显示 4 例患者为 T1 期，10 例患者为 T2 期，18 例患者为 T3 期。两组间（T1-2 与 T3）在年龄和性别上无显著差异。两位观察者之间的 ADC 值具有极好的可重复性，ICC 值范围为 0.920 至 0.998，CV 值范围为 1.475 至 5.568%。配对测量的平均百分比差异和ρ值范围分别为-2.7%至 1.2%和-0.759 至-0.407。α值为 2.581、2.571 和 2.569 时，最佳 b 值组合分别为 b（0、1000 s/mm）、b（500、1500、2000 s/mm）和 b（100、1000、1500 s/mm）。
b 值的数量及其分布影响 ADC 值的重复性及其诊断性能。对于直肠癌患者的 DWI 检查，最佳 b 值组合为 0 和 1000 s/mm。
