Computed tomography-based psoas skeletal muscle area and radiodensity are poor sentinels for whole L3 skeletal muscle values

Abstract

Summary Background and aims Computed tomography (CT)-based measurement of skeletal muscle cross-sectional area (CSA) and Hounsfield unit (HU) radiodensity are used to assess the presence of sarcopenia and myosteatosis, respectively. The validated CT-based technique involves analysis of skeletal muscle at the third lumbar vertebral (L3) level. Recently there has been increasing interest in the use of psoas muscle alone as a sentinel. However, this technique has not been extensively investigated or compared with the previous validated standard approach. Methods Portovenous phase CT images at the L3 level were identified retrospectively from a single institution in 150 patients who had non-emergency scans and were analysed by a single assessor using SliceOmatic software v5.0 (TomoVision, Canada). Manual segmentation based upon validated HU thresholds for skeletal muscle density was performed for all skeletal muscle, as well as the individual muscle groups. The muscle CSA and mean radiodensity of each group were compared against the whole L3 slice values. Results When compared with whole L3 slice CSA, anterior abdominal wall CSA had the strongest correlation (r = 0.9315, p < 0.0001) followed by paravertebral (r = 0.8948, p < 0.0001), then psoas muscle (r = 0.7041, p < 0.0001). The mean ± SD density of the psoas muscle (42 ± 8.4 HU) was significantly higher than the whole slice radiodensity (32.3 ± 9.5 HU, p < 0.0001), with paravertebral radiodensity being a more accurate estimation (34.5 ± 10.8 HU). There was a significant difference in the prevalence of myosteatosis when the density measured from the psoas was compared with that of the whole L3 skeletal muscle (27.7% vs. 66.0%, p < 0.0001). Conclusion Whole L3 slice CSA correlated positively with psoas muscle CSA but was subject to wide variability in results. Psoas muscle radiodensity was significantly greater than whole L3 slice density and resulted in underestimation of the prevalence of myosteatosis. Given the lack of equivalence from individual muscle groups, we recommend that further work be undertaken to investigate which muscle group, or indeed whether the gold standard of whole L3 skeletal muscle, provides the best correlation with clinical outcomes.

The relationship between computed tomography derived skeletal muscle index, psoas muscle index and clinical outcomes in patients with operable colorectal cancer

“…This was despite that PMA may be affected by different degenerative spinal pathologies [17]. Indeed, there was a moderate correlation between SMA and PMA (r ¼ 0.70) in non-cancer patients [18]. Therefore, PMA is a reasonable substitute, and has been reported to be associated with greater postoperative complications in patients with CRC (see Table S2) [10e15,24].…”

“…Specifically, CT derived muscle radiodensity is dependent on cardiac output at the time of scan and varied proportions of intramuscular blood supply to the individual muscles in accordance with pathophysiological and health status. It may be that MRI is a better modality to assess skeletal muscle quality in patients with cancer [18]. Therefore, further work is required to determine the anatomical basis for CTderived muscle density measurements [28,29], this will in turn enable better standardisation of the methodology.…”

“…However, Rutten et al reported in 150 patients with advanced ovarian cancer, a weaker correlation (r ¼ 0.5) [17]. Furthermore, Rollins et al reported that, in 150 non-cancerous, non-emergency patients, SMA and PMA were moderately correlated (r ¼ 0.7) [18]. Therefore, it is not clear whether the prognostic value of SMA reflects that of PMA.…”

Prediction of abdominal CT body composition parameters by thoracic measurements as a new approach to detect sarcopenia in a COVID-19 cohort

“…The MRA was determined from the whole abdominal muscle at L3 after application of the muscle-specific threshold (Fig. 1 d) to avoid underestimation of myosteotosis which can occur if measurements are restricted to, e.g., the psoas muscle 26 . Whole-body fat mass [kg] and visceral fat mass [kg] were calculated as proposed by Zopf et al, who have proven good agreement to bioelectrical impedance analysis (BIA) body composition results 13 .…”

Assessment of Muscle Quantity, Quality and Function

“… 33 , 34 Recently, psoas muscle SMA alone has been of interest as a marker of muscle mass; however, inter-individual variation in the relative proportion of SMA between the psoas muscle and other paravertebral muscles or anterior abdominal wall muscles at the L3 level has been reported. 35 , 36 …”