Department of Radiology and Nuclear Medicine, Amsterdam Movement Sciences, Amsterdam University Medical Center, Amsterdam, The Netherlands.
Center for Child Development, Exercise and Physical Literacy, Wilhelmina Children's Hospital, University Medical Center Utrecht, Utrecht, The Netherlands.
NMR Biomed. 2022 Jul;35(7):e4696. doi: 10.1002/nbm.4696. Epub 2022 Feb 14.
Quantitative magnetic resonance imaging (qMRI) is frequently used to map the disease state and disease progression in the lower extremity muscles of patients with spinal muscular atrophy (SMA). This is in stark contrast to the almost complete lack of data on the upper extremity muscles, which are essential for carrying out daily activities. The aim of this study was therefore to assess the disease state in the upper arm muscles of patients with SMA in comparison with healthy controls by quantitative assessment of fat fraction, diffusion indices, and water T2 relaxation times, and to relate these measures to muscle force. We evaluated 13 patients with SMA and 15 healthy controls with a 3-T MRI protocol consisting of DIXON, diffusion tensor imaging, and T2 sequences. qMRI measures were compared between groups and related to muscle force measured with quantitative myometry. Fat fraction was significantly increased in all upper arm muscles of the patients with SMA compared with healthy controls and correlated negatively with muscle force. Additionally, fat fraction was heterogeneously distributed within the triceps brachii (TB) and brachialis muscle, but not in the biceps brachii muscle. Diffusion indices and water T2 relaxation times were similar between patients with SMA and healthy controls, but we did find a slightly reduced mean diffusivity (MD), λ1, and λ3 in the TB of patients with SMA. Furthermore, MD was positively correlated with muscle force in the TB of patients with SMA. The variation in fat fraction further substantiates the selective vulnerability of muscles. The reduced diffusion tensor imaging indices, along with the positive correlation of MD with muscle force, point to myofiber atrophy. Our results show the feasibility of qMRI to map the disease state in the upper arm muscles of patients with SMA. Longitudinal data in a larger cohort are needed to further explore qMRI to map disease progression and to capture the possible effects of therapeutic interventions.
定量磁共振成像（qMRI）常用于描绘脊髓性肌萎缩症（SMA）患者下肢肌肉的疾病状态和疾病进展。这与上肢肌肉几乎完全缺乏数据形成鲜明对比，而上肢肌肉对于进行日常活动至关重要。因此，本研究旨在通过定量评估脂肪分数、扩散指数和水 T2 弛豫时间，来评估 SMA 患者的上臂肌肉疾病状态，并将这些测量值与肌肉力量相关联。我们评估了 13 名 SMA 患者和 15 名健康对照者，使用 3-T MRI 方案，包括 DIXON、弥散张量成像和 T2 序列。在组间比较 qMRI 测量值，并与定量肌测法测量的肌肉力量相关联。与健康对照组相比，所有 SMA 患者的上臂肌肉的脂肪分数均显著增加，且与肌肉力量呈负相关。此外，脂肪分数在肱三头肌（TB）和肱二头肌内呈异质性分布，但在肱二头肌内无此分布。SMA 患者和健康对照组之间的扩散指数和水 T2 弛豫时间相似，但我们发现 SMA 患者的 TB 中平均弥散度（MD）、λ1 和 λ3 略有降低。此外，MD 与 SMA 患者 TB 中的肌肉力量呈正相关。脂肪分数的变化进一步证实了肌肉的选择性易损性。弥散张量成像指数的降低，以及 MD 与肌肉力量的正相关，表明肌纤维萎缩。我们的研究结果表明 qMRI 可用于描绘 SMA 患者的上臂肌肉疾病状态。需要更大的队列进行纵向数据研究，以进一步探索 qMRI 来描绘疾病进展，并捕捉可能的治疗干预效果。
