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Computer Tomography-Based Psoas Skeletal Muscle Area and Radiodensity are Poor Sentinels for Whole L3 Skeletal Muscle Values

Rollins, Katie E.; Gopinath, Aravin; Awwad, Amir; Macdonald, Ian A.; Lobo, Dileep N.


Katie E. Rollins

Aravin Gopinath

Amir Awwad

Ian A. Macdonald

Professor of Gastrointestinal Surgery


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.

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.

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).

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.


Rollins, K. E., Gopinath, A., Awwad, A., Macdonald, I. A., & Lobo, D. N. (2020). Computer Tomography-Based Psoas Skeletal Muscle Area and Radiodensity are Poor Sentinels for Whole L3 Skeletal Muscle Values. Clinical Nutrition, 39(7), 2227-2232.

Journal Article Type Article
Acceptance Date Oct 2, 2019
Online Publication Date Oct 14, 2019
Publication Date 2020-07
Deposit Date Oct 10, 2019
Journal Clinical Nutrition
Print ISSN 0261-5614
Electronic ISSN 1532-1983
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 39
Issue 7
Pages 2227-2232
Keywords Computed tomography; Psoas; Skeletal muscle; Sarcopenia; Hounsfield Unit; Density
Public URL
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