Schlaeger Sarah, Sollmann Nico, Zoffl Agnes, Becherucci Edoardo Aitala, Weidlich Dominik, Kottmaier Elisabeth, Riederer Isabelle, Greve Tobias, Montagnese Federica, Deschauer Marcus, Schoser Benedikt, Zimmer Claus, Karampinos Dimitrios C, Kirschke Jan S, Baum Thomas
Department of Diagnostic and Interventional Neuroradiology, School of Medicine, Klinikum rechts der Isar, Technical University of Munich, Ismaninger Str. 22, 81675 Munich, Germany.
TUM-Neuroimaging Center, Klinikum rechts der Isar, Technical University of Munich, 81675 Munich, Germany.
Diagnostics (Basel). 2021 Jun 8;11(6):1056. doi: 10.3390/diagnostics11061056.
(1) Background and Purpose: The skeletal muscles of patients suffering from neuromuscular diseases (NMD) are affected by atrophy, hypertrophy, fatty infiltration, and edematous changes. Magnetic resonance imaging (MRI) is an important tool for diagnosis and monitoring. Concerning fatty infiltration, T-weighted or T-weighted DIXON turbo spin echo (TSE) sequences enable a qualitative assessment of muscle involvement. To achieve higher comparability, semi-quantitative grading scales, such as the four-point Mercuri scale, are commonly applied. However, the evaluation remains investigator-dependent. Therefore, effort is being invested to develop quantitative MRI techniques for determination of imaging markers such as the proton density fat fraction (PDFF). The present work aims to assess the diagnostic value of PDFF in correlation to Mercuri grading and clinically determined muscle strength in patients with myotonic dystrophy type 2 (DM2), limb girdle muscular dystrophy type 2A (LGMD2A), and adult Pompe disease. (2) Methods: T-weighted two-dimensional (2D) DIXON TSE and chemical shift encoding-based water-fat MRI were acquired in 13 patients (DM2: = 5; LGMD2A: = 5; Pompe disease: = 3). Nine different thigh muscles were rated in all patients according to the Mercuri grading and segmented to extract PDFF values. Muscle strength was assessed according to the British Medical Research Council (BMRC) scale. For correlation analyses between Mercuri grading, muscle strength, and PDFF, the Spearman correlation coefficient (r) was computed. (3) Results: Mean PDFF values ranged from 7% to 37% in adults with Pompe disease and DM2 and up to 79% in LGMD2A patients. In all three groups, a strong correlation of the Mercuri grading and PDFF values was observed for almost all muscles ( > 0.70, < 0.05). PDFF values correlated significantly to muscle strength for muscle groups responsible for knee flexion ( = -0.80, < 0.01). (4) Conclusion: In the small, investigated patient cohort, PDFF offers similar diagnostic precision as the clinically established Mercuri grading. Based on these preliminary data, PDFF could be further considered as an MRI-based biomarker in the assessment of fatty infiltration of muscle tissue in NMD. Further studies with larger patient cohorts are needed to advance PDFF as an MRI-based biomarker in NMD, with advantages such as its greater dynamic range, enabling the assessment of subtler changes, the amplified objectivity, and the potential of direct correlation to muscle function for selected muscles.
（1）背景与目的：患有神经肌肉疾病（NMD）的患者骨骼肌会受到萎缩、肥大、脂肪浸润和水肿变化的影响。磁共振成像（MRI）是诊断和监测的重要工具。关于脂肪浸润，T加权或T加权DIXON涡轮自旋回波（TSE）序列可对肌肉受累情况进行定性评估。为了实现更高的可比性，通常应用半定量分级量表，如四点Mercuri量表。然而，评估仍依赖于研究者。因此，人们正在努力开发定量MRI技术以确定成像标志物，如质子密度脂肪分数（PDFF）。本研究旨在评估PDFF与Mercuri分级以及2型强直性肌营养不良（DM2）、2A型肢带型肌营养不良（LGMD2A）和成人庞贝病患者临床测定的肌肉力量之间的相关性及诊断价值。（2）方法：对13例患者（DM2：n = 5；LGMD2A：n = 5；庞贝病：n = 3）进行了T加权二维（2D）DIXON TSE和基于化学位移编码的水脂MRI检查。根据Mercuri分级对所有患者的九块不同大腿肌肉进行评分，并进行分割以提取PDFF值。根据英国医学研究委员会（BMRC）量表评估肌肉力量。为了分析Mercuri分级、肌肉力量和PDFF之间的相关性，计算了Spearman相关系数（r）。（3）结果：成人庞贝病和DM2患者的平均PDFF值在7%至37%之间，LGMD2A患者高达79%。在所有三组中，几乎所有肌肉的Mercuri分级与PDFF值均呈强相关性（r > 0.70，P < 0.05）。负责膝关节屈曲的肌肉群的PDFF值与肌肉力量显著相关（r = -0.80，P < 0.01）。（4）结论：在这个小规模的研究患者队列中，PDFF提供了与临床确立的Mercuri分级相似的诊断精度。基于这些初步数据，在评估NMD患者肌肉组织脂肪浸润时，可进一步将PDFF视为基于MRI的生物标志物。需要更大患者队列的进一步研究来推进PDFF作为NMD中基于MRI的生物标志物，其优点包括更大的动态范围，能够评估更细微的变化、更高的客观性以及与特定肌肉的肌肉功能直接相关的潜力。
