乳腺癌的弥散加权 MRI：使用合成 b 值提高病变可见度和图像质量。
Diffusion-Weighted MRI of Breast Cancer: Improved Lesion Visibility and Image Quality Using Synthetic b-Values.
机构信息
Department of Biomedical Imaging and Image Guided Therapy, Division of Molecular and Gender Imaging, Medical University of Vienna, Austria.
Department of Radiology, Breast Imaging Service, Memorial Sloan Kettering Cancer Center, New York, New York, USA.
出版信息
J Magn Reson Imaging. 2019 Dec;50(6):1754-1761. doi: 10.1002/jmri.26809. Epub 2019 May 28.
BACKGROUND
Diffusion-weighted imaging (DWI) is an MRI technique with the potential to serve as an unenhanced breast cancer detection tool. Synthetic b-values produce images with high diffusion weighting to suppress residual background signal, while avoiding additional measurement times and reducing artifacts.
PURPOSE
To compare acquired DWI images (at b = 850 s/mm ) and different synthetic b-values (at b = 1000-2000 s/mm ) in terms of lesion visibility, image quality, and tumor-to-tissue contrast in patients with malignant breast tumors.
STUDY TYPE
Retrospective.
POPULATION
Fifty-three females with malignant breast lesions.
FIELD STRENGTH/SEQUENCE: T w, DWI EPI with STIR fat-suppression, and dynamic contrast-enhanced T w at 3T.
ASSESSMENT
From acquired images using b-values of 50 and 850 s/mm , synthetic images were calculated at b = 1000, 1200, 1400, 1600, 1800, and 2000 s/mm . Four readers independently rated image quality, lesion visibility, preferred b-value, as well as the lowest and highest b-value, over the range of b-values tested, to provide a diagnostic image.
STATISTICAL TESTS
Medians and mean ranks were calculated and compared using the Friedman test and Wilcoxon signed-rank test. Reproducibility was analyzed by intraclass correlation (ICC), Fleiss, and Cohen's κ.
RESULTS
Relative signal-to-noise and contrast-to-noise ratios decreased with increasing b-values, while the signal-intensity ratio between tumor and tissue increased significantly (P < 0.001). Intermediate b-values (1200-1800 s/mm ) were rated best concerning image quality and lesion visibility; the preferred b-value mostly lay at 1200-1600 s/mm . Lowest and highest acceptable b-values were 850 s/mm and 2000 s/mm . Interreader agreement was moderate to high concerning image quality (ICC: 0.50-0.67) and lesion visibility (0.70-0.93), but poor concerning preferred and acceptable b-values (κ = 0.032-0.446).
DATA CONCLUSION
Synthetically increased b-values may be a way to improve tumor-to-tissue contrast, lesion visibility, and image quality of breast DWI, while avoiding the disadvantages of performing DWI at very high b-values.
LEVEL OF EVIDENCE
3 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;50:1754-1761.
背景
扩散加权成像（DWI）是一种磁共振成像技术，具有作为增强型乳腺癌检测工具的潜力。合成 b 值产生具有高扩散加权的图像，以抑制残留的背景信号，同时避免额外的测量时间并减少伪影。
目的
比较恶性乳腺肿瘤患者获得的 DWI 图像（b = 850 s/mm ）和不同的合成 b 值（b = 1000-2000 s/mm ）在病变可见性、图像质量和肿瘤-组织对比度方面的差异。
研究类型
回顾性。
人群
53 名患有恶性乳腺病变的女性。
磁场强度/序列：T w ，带有 STIR 脂肪抑制的 DWI EPI，以及 3T 下的动态对比增强 T w 。
评估
从使用 b 值为 50 和 850 s/mm 的采集图像中，计算了 b 值为 1000、1200、1400、1600、1800 和 2000 s/mm 的合成图像。四位读者独立评估了图像质量、病变可见性、首选 b 值以及在测试的 b 值范围内最低和最高 b 值，以提供诊断图像。
统计检验
使用 Friedman 检验和 Wilcoxon 符号秩检验计算中位数和平均秩，并进行比较。使用组内相关系数（ICC）、Fleiss 和 Cohen's κ 分析可重复性。
结果
随着 b 值的增加，相对信噪比和对比噪声比降低，而肿瘤与组织之间的信号强度比显著增加（P < 0.001）。中间 b 值（1200-1800 s/mm ）在图像质量和病变可见性方面被评为最佳；首选 b 值主要位于 1200-1600 s/mm 。最低和最高可接受的 b 值分别为 850 s/mm 和 2000 s/mm 。读者间在图像质量（ICC：0.50-0.67）和病变可见性（0.70-0.93）方面的一致性为中等至高，但在首选和可接受的 b 值方面一致性较差（κ = 0.032-0.446）。
数据结论
合成增加的 b 值可能是一种提高乳腺 DWI 肿瘤-组织对比度、病变可见性和图像质量的方法，同时避免在非常高的 b 值下进行 DWI 的缺点。
证据水平
3 级 技术功效：第 2 阶段 J. 磁共振成像 2019；50：1754-1761。
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