Laboratory of Imaging Biomarkers, Université Paris Cité, Inserm, CRI, Paris, France.
Department of Pathology, AP-HP, Beaujon University Hospital Paris Nord, Clichy, France.
J Magn Reson Imaging. 2023 Aug;58(2):403-414. doi: 10.1002/jmri.28543. Epub 2022 Nov 30.
In magnetic resonance elastography (MRE), the precision of the observed mechanical depends on the ratio between mechanical wavelength and spatial resolution. Since the mechanical wavelength may vary with actuation frequency, between patients and depending on position, a unique spatial resolution may not always generate an optimal ratio for multifrequency acquisitions, in patients with varying degrees of disease or in mechanically heterogeneous organs.
To describe an MRE reconstruction algorithm that adjusts the ratio between shear wavelength and pixel size, by locally resampling the matrix of shear displacement, and to assess its performance relative to existing reconstructions in different use cases.
Prospective.
Four phantoms, 20 healthy volunteers (5 men, median age 34, range 20-56) and 46 patients with nonalcoholic fatty liver disease (37 men, median age 63, range 33-83).
FIELD STRENGTH/SEQUENCE: A 3 T; gradient-echo elastography sequence with 40 Hz, 60 Hz, and 80 Hz frequencies.
For each algorithm, phantoms stiffness were compared against their nominal values, repeatability was calculated in healthy volunteers, and diagnostic performance in detecting advanced liver fibrosis was assessed in 46 patients.
Linear regression was used to evaluate the agreement between stiffness values and phantoms stiffnesses. Bland-Altman method was used to evaluate repeatability in volunteers. The ability to diagnose advanced fibrosis was assessed by receiver operating curve analysis (with Youden index thresholds). Significance was considered at P value of 0.05.
From the linear regression, the slope closest to 1 is provided by MARS (40 Hz) and k-MDEV (60H, 80 Hz). Repeatability index was best with MDEV (23%) and lowest with k-MDEV (53%). The best performance in detecting advanced fibrosis was provided by MARS at 40 Hz (area under the operating curve, AUC = 0.88), k-MDEV and MARS at 60 Hz (AUC = 0.91), and multimodel direct inversion (MMDI) and MARS at 80 Hz (AUC = 0.90).
MARS shows the best diagnostic performance to detect advanced fibrosis and the second-best results in phantoms after k-MDEV.
Stage 2.
在磁共振弹性成像（MRE）中，观察到的力学精度取决于力学波长与空间分辨率之间的比值。由于机械波长可能随激励频率变化，在不同患者之间以及取决于位置，因此对于多频采集，并非总是会为具有不同疾病程度或在机械上不均匀的器官的患者生成一个最佳的空间分辨率比值。
描述一种 MRE 重建算法，通过局部重采样剪切位移矩阵来调整剪切波长与像素大小之间的比值，并评估其在不同应用场景中相对于现有重建算法的性能。
前瞻性。
四个体模、20 名健康志愿者（5 名男性，中位年龄 34 岁，范围 20-56 岁）和 46 名非酒精性脂肪性肝病患者（37 名男性，中位年龄 63 岁，范围 33-83 岁）。
磁场强度/序列：3T；梯度回波弹性成像序列，频率分别为 40Hz、60Hz 和 80Hz。
对于每种算法，将体模的刚度与标称值进行比较，在健康志愿者中计算重复性，在 46 名患者中评估检测晚期肝纤维化的诊断性能。
线性回归用于评估刚度值与体模刚度之间的一致性。Bland-Altman 方法用于评估志愿者的重复性。通过接收者操作特征曲线分析（采用 Youden 指数阈值）评估诊断晚期纤维化的能力。P 值小于 0.05 被认为具有统计学意义。
从线性回归来看，斜率最接近 1 的是 MARS（40Hz）和 k-MDEV（60Hz、80Hz）。重复性指数最好的是 MDEV（23%），最差的是 k-MDEV（53%）。在检测晚期纤维化方面，40Hz 的 MARS（曲线下面积 AUC=0.88）、60Hz 的 k-MDEV 和 MARS（AUC=0.91）以及 80Hz 的多模型直接反演（MMDI）和 MARS（AUC=0.90）的性能最佳。
MARS 在检测晚期纤维化方面表现出最佳的诊断性能，仅次于 k-MDEV 在体模方面的表现。
1。
2 级。
