Measuring Sarcopenia via Psoas Muscle Area

Sarcopenia was assessed by measuring the cross sectional area of the right and left psoas muscles (total psoas muscle area=TPA). TPA was measured at the level of L3 on the first image with both vertebral spines visible. Measurements were performed in a semi-automated fashion with manual outlining of psoas muscle borders and setting the density threshold between −30 and 110 Hounsfield Units (HU; Fig. 1). This allowed for automatic calculation of psoas muscle area by excluding vasculature and areas of fatty infiltration based on HU. The measured psoas area was then normalized for height, as per convention for body composition measurements (TPA mm²/m²).^{29 (link)-31 (link)}