Extending the capabilities of ultrasound for skeletal muscle assessment

超声在临床上（诊断肌肉骨骼损伤）和研究中对肌肉大小的变化进行量化是非常依赖的。有趣的是，超声波的功能可能会超出这些常规用途，用于测量肌肉成分（脂肪浸润）和细胞内代谢。然而，这一领域还处于起步阶段，需要做更多的工作来推进这些尖端的超声技术。长期目的：推进超声无创测量肌肉成分和代谢的应用。磁共振成像（MRI）、计算机断层扫描和肌肉活检传统上用于量化肌肉脂肪浸润。不幸的是，这些方法受到诸如高成本、暴露于电离辐射和侵入性等障碍的限制。考虑到肌肉回声强度（像素亮度）与脂肪浸润直接对应，超声波可能是一种可行的替代方法。但是，可靠性与回波强度（一个简单的结果）有关，因为它与皮下脂肪组织厚度和仪器设置高度混淆。高阶超声纹理分析（像素之间的空间关系）可能是解决这一问题的新方法。此外，特定的质地特征与葡萄糖稳态标志物相关，而葡萄糖稳态直接受肌肉脂肪浸润的影响。这项开创性的研究处于代谢分析的前沿，但肌肉脂肪浸润和葡萄糖代谢之间关系的确切性质——因为它们与超声波有关——需要充分阐明。短期目标：1)系统地定义个体高阶纹理特征与骨骼肌成分和代谢之间的关系；2)创建一个准确可靠的基于算法的度量（“肌肉质量指数”或MQI），使用超声纹理分析对肌肉成分进行评分；3)测试MQI在检测肌肉成分和代谢变化方面的功效。我的实验室主要以人类作为实验模型来探索创新的超声技术。HQP将获得使用金标准（MRI）和新兴（超声）技术以及复杂的生化技术（稳定同位素示踪剂）进行身体成分分析的技能。我们将使用脂质输注和脂肪负荷方案来测试超声MQI检测肌肉成分和代谢变化的能力。学员还将学习备受追捧的编码技能，这是开发算法以生成我们的新MQI所不可或缺的。这个项目的实际成果（MQI）将通过扩大肌肉生理学家的研究能力，极大地推进NSE，并将我的实验室定位为尖端超声检查的国际领导者。重要的是，MQI将增加未充分研究和公平的人群，他们可能会反对像活检这样的侵入性手术。

Ultrasound is heavily relied upon in clinic (to diagnose musculoskeletal injuries) and in research to quantify changes in muscle size. Intriguingly, the capabilities of ultrasound may extend beyond these conventional uses to the measurement of muscle composition (fat infiltration) and intracellular metabolism. However, this field is in its infancy, and significantly more work is needed to advance these cutting-edge ultrasound techniques. LONG-TERM OBJECTIVE: To advance the use of ultrasound to non-invasively measure muscle composition and metabolism. Magnetic resonance imaging (MRI), computed tomography, and muscle biopsies are traditionally used to quantify muscle fat infiltration. Unfortunately, these methods are limited by barriers such as high cost, exposure to ionizing radiation, and invasiveness. Ultrasound may be an accessible alternative, given that muscle echointensity (pixel brightness) corresponds directly with fat infiltration. But, reliability is a concern with echointensity (a simplistic outcome) since it is highly confounded by subcutaneous adipose tissue thickness and instrument settings. Higher-order ultrasound texture analysis (spatial relationships between pixels), may be a novel solution to this problem. Furthermore, specific texture features correlate with markers of glucose homeostasis, which is directly affected by muscle fat infiltration. This ground-breaking research is at the forefront of metabolic profiling, but the exact nature of the relationships between muscle fat infiltration and glucose metabolism - as they pertain to ultrasound - needs to be fully elucidated. Short-term objectives: O1)Systematically define the relationships between individual higher-order texture features and skeletal muscle composition and metabolism, O2)Create an accurate and reliable algorithm-based metric (the "Muscle Quality Index" or MQI) that uses ultrasound texture analysis to score muscle composition, O3)Test the efficacy of the MQI in detecting changes in muscle composition and metabolism. My lab focuses on humans as an experimental model to explore innovative ultrasound techniques. HQP will acquire skills in body composition analysis using gold-standard (MRI) and emerging (ultrasound) technologies, as well as sophisticated biochemical techniques (stable isotope tracers). We will use lipid infusions and fat-loading protocols to test the ability of the ultrasound MQI in detecting changes in muscle composition and metabolism. Trainees will also learn highly-sought after coding skills, which are integral to developing the algorithm to generate our novel MQI. The tangible outcome of this program (the MQI) will greatly advance the NSE by expanding the research capabilities of muscle physiologists, and position my lab as an international leader in cutting-edge ultrasonography. Importantly, the MQI will increase inclusion of understudied and equity-deserving populations who may be averse to invasive procedures like biopsies.