Sarcopenia, More Than Just Muscle Atrophy: Imaging Methods for the Assessment of Muscle Quantity and Quality

Abstract

Background Sarcopenia, a progressive reduction of muscle mass and function, is associated with adverse outcomes in the elderly. Sarcopenia and muscle atrophy are not equal processes. Low muscle strength in association with muscle quantity/quality reduction is currently the optimal method for assessing sarcopenia. There is a practical need for indirect measurement of muscle strength using state-of-the-art imaging techniques. Methods The following provides a narrative, broad review of all current imaging techniques for evaluating muscles and identifying sarcopenia, including DEXA, CT, MRI, and high-resolution ultrasound, their main strengths, weaknesses, and possible solutions to problems regarding each technique. Results and Conclusion Well-recognized imaging methods for the assessment of muscle mass are explained, including evaluation with DEXA, CT, and MRI muscle quantity assessment, ultrasound evaluation of muscle thickness and CSA, and their correlations with established muscle mass calculation methods. A special focus is on imaging methods for muscle quality evaluation. Several innovative and promising techniques that are still in the research phase but show potential in the assessment of different properties of muscle quality, including MRI DIXON sequences, MRI spectroscopy, Diffusion Tensor Imaging, ultrasound echo intensity, ultrasound elastography, and speed-of-sound ultrasound imaging are briefly mentioned. Key Points: Citation Format

The Relationship Between Intramural Fat Accumulation and Sarcopenia on MR Enterography Exams in Patients with Crohn’s Disease

“…Exact or functional muscle mass in these patients might be overestimated due to myosteatosis, which should be considered in the assessment of sarcopenia in patients with CD. Myosteatosis, a term comprising intermuscular, intramuscular, and/or intramyocellular fat, negatively correlates with muscle strength, quality, or function [13]. Muscle strength and quality are better than mass in predicting the presence of sarcopenia and adverse outcomes [8].…”

“…bidity/mortality and an independent risk factor for many diseases [13]. Sarcopenia may regress with proper treatment and close follow-up [9].…”

“…[3,5,10]. Opportunistic imaging uses routine imaging exams to obtain new imaging biomarkers and cut-off values and to obtain additional useful information [13]. Routine MRE examinations can also be used to evaluate sarcopenia and myosteatosis as an example of opportunistic imaging.…”

Thigh muscle thickness on ultrasonography for diagnosing sarcopenia: The Kyoto‐Kameoka study

“…Therefore, reliability can be controlled through adequate training. Another limitation of ultrasonography is that the measurement sites are not unified for the assessment 33 …”

Editorial: Let your muscles do the talking—what can muscle quality tell us about hepatic fibrosis?

“…The authors showed that radiation exposure is negligible and ideas for ultrasound alternatives are being developed. 9 However, with adjusted hazard ratios of about 1.3 per change in category of low-attenuation "skeletal muscle index", the question is if the resources spent in order to pare down the at-risk population by a few percent are larger than those that could be saved.…”