Extending the capabilities of ultrasound for skeletal muscle assessment

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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.