1 Institute of Clinical Radiology, LMU University of Munich-Campus Grosshadern, Marchioninistrasse 15, 81377 Munich, Germany.
AJR Am J Roentgenol. 2014 Sep;203(3):582-8. doi: 10.2214/AJR.13.11632.
OBJECTIVE: The purpose of our study was to determine the optimum combination of b values for calculating the apparent diffusion coefficient (ADC) using a diffusion-weighted (DW) single-shot turbo spin-echo (TSE) sequence in the differentiation between acute benign and malignant vertebral body fractures. SUBJECTS AND METHODS: Twenty-six patients with osteoporotic (mean age, 69 years; range, 31.5-86.2 years) and 20 patients with malignant vertebral fractures (mean age, 63.4 years; range, 24.7-86.4 years) were studied. T1-weighted, STIR, and T2-weighted sequences were acquired at 1.5 T. A DW single-shot TSE sequence at different b values (100, 250, 400, and 600 s/mm(2)) was applied. On the DW images for each evaluated fracture, an ROI was manually adapted to the area of hyperintense signal intensity on STIR-hypointense signal on T1-weighted images. For each ROI, nine different combinations of two, three, and four b values were used to calculate the ADC using a least-squares algorithm. The Student t test and Mann-Whitney U test were used to determine significant differences between benign and malignant fractures. An ROC analysis and the Youden index were used to determine cutoff values for assessment of the highest sensitivity and specificity for the different ADC values. The positive (PPV) and negative predictive values (NPV) were also determined. RESULTS: All calculated ADCs (except the combination of b = 400 s/mm(2) and b = 600 s/mm(2)) showed statistically significant differences between benign and malignant vertebral body fractures, with benign fractures having higher ADCs than malignant ones. The use of higher b values resulted in lower ADCs than those calculated with low b values. The highest AUC (0.85) showed the ADCs calculated with b = 100 and 400 s/mm(2), and the second highest AUC (0.829) showed the ADCs calculated with b = 100, 250, and 400 s/mm(2). The Youden index with equal weight given to sensitivity and specificity suggests use of an ADC calculated with b = 100, 250, and 400 s/mm(2) (cutoff ADC, < 1.7 × 10(-3) mm(2)/s) to best diagnose malignancy (sensitivity, 85%; specificity, 84.6%; PPV, 81.0%; NPV, 88.0%). CONCLUSION: ADCs calculated with a combination of low to intermediate b values (b = 100, 250, and 400 s/mm(2)) provide the best diagnostic performance of a DW single-shot TSE sequence to differentiate acute benign and malignant vertebral body fractures.
目的：本研究旨在确定使用单次激发弥散加权（DW）自旋回波（TSE）序列在区分急性良性和恶性椎体骨折时计算表观弥散系数（ADC）的最佳 b 值组合。
材料与方法：研究对象为 26 例骨质疏松性椎体骨折患者（平均年龄 69 岁；范围 31.5-86.2 岁）和 20 例恶性椎体骨折患者（平均年龄 63.4 岁；范围 24.7-86.4 岁）。在 1.5T 上采集 T1 加权、短 TI 反转恢复（STIR）和 T2 加权序列。应用不同 b 值（100、250、400 和 600 s/mm²）的 DW 单次激发 TSE 序列。对于每个评估的骨折，在 DW 图像上手动将 ROI 适配到 STIR 低信号强度上 T1 加权图像的高信号强度区域。对于每个 ROI，使用两种、三种和四种 b 值的九种不同组合，使用最小二乘法算法计算 ADC。使用 Student t 检验和 Mann-Whitney U 检验来确定良性和恶性骨折之间的显著差异。使用 ROC 分析和 Youden 指数来确定不同 ADC 值的最高灵敏度和特异性的截断值。还确定了阳性（PPV）和阴性预测值（NPV）。
结果：除了 b = 400 s/mm²和 b = 600 s/mm²的组合外，所有计算的 ADC（除了 b = 400 s/mm²和 b = 600 s/mm²的组合外）在良性和恶性椎体骨折之间均显示出统计学上的显著差异，良性骨折的 ADC 高于恶性骨折。使用较高的 b 值会导致 ADC 值低于使用低 b 值计算的值。最高 AUC（0.85）显示 b = 100 和 400 s/mm² 计算的 ADC，第二高 AUC（0.829）显示 b = 100、250 和 400 s/mm² 计算的 ADC。灵敏度和特异性权重相等的 Youden 指数表明，使用 b = 100、250 和 400 s/mm²（截断 ADC，<1.7×10(-3)mm²/s）计算 ADC 可最佳诊断恶性肿瘤（灵敏度，85%；特异性，84.6%；PPV，81.0%；NPV，88.0%）。
结论：低至中等 b 值（b = 100、250 和 400 s/mm²）组合计算的 ADC 提供了 DW 单次激发 TSE 序列在区分急性良性和恶性椎体骨折方面的最佳诊断性能。
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