Feasibility of assessment of skeletal muscle mass on a single cross-sectional image at the level of the fourth thoracic vertebra

Abstract

Background: Skeletal muscle mass (SMM) determined on computed tomography (CT) is emerging as a novel imaging biomarker. Cross-sectional area (CSA) of SMM at the level of the third lumbar vertebra (L3) on abdominal imaging is considered the clinical reference standard for measuring SMM. In certain patient groups, such as those with oncological or non-oncological lung disease like COVID-19, a chest CT may be available while an abdominal CT is not. The purpose of this study was to investigate whether determining SMM on a chest CT is a feasible alternative to abdominal CT. Research question: What is the correlation between SMM measurements at the level of L3 and the level of the fourth thoracic vertebra (Th4)? Study design and methods: In this study we retrospectively analyzed abdominal and thoracic series of whole-body CT-scans of trauma patients (N = 47) and head and neck cancer patients (N = 194). All abdominal muscles were delineated on a single axial slice at the level of L3. The erector spinae, levator scapulae, rhomboideus minor and major and pectoralis minor and major muscles were delineated on a single axial slice at the level of Th4. CSA of the muscles at Th4 and the L3 level were compared using linear regression, and a multivariate linear regression model was established. Results: Muscle CSA at level Th4 strongly correlates with L3 muscle CSA (r = 0.791, p < 0.05). A multivariate model incorporating the patient characteristics arm positioning, age, sex, and weight achieved a stronger correlation (r = 0.856, p < 0.05). Interpretation: Skeletal muscle CSA measured at the level of Th4 is a feasible alternative to measurements at L3. This allows diagnosing low SMM using clinically available thoracic CT-scans. SMM measurements at the level of Th4 may become a prognostic or triage tool when faced with mechanical ventilator shortage.

Nutritional Risk Assessment Scores Effectively Predict Mortality in Critically Ill Patients with Severe COVID-19

“…In the setting of COVID-19, it became evident that fat tissue assessment and the analysis of muscle mass, typically analyzed in the lumbar region on abdominal CT scans, must be validated with surrogates on thoracic CT acquisitions, since this quickly became the gold standard to assess COVID-19 disease severity. One report from a Dutch study group has indicated that skeletal muscle mass determined on a thoracic CT scan appeared to correlate well to measurements on the lumbar region on scans belonging to the same patient [ 15 ]. However, the role of various fat-tissue and muscle mass measurements on thoracic CT scans in predicting a worse outcome has yet to be clearly defined.…”

“…To circumvent the need for interleukin-6, which might not be part of the biological armamentarium of each hospital, mNUTRIC excludes its value from the calculation formula, providing non-inferior risk assessment [ 14 ]. Indicators of malnutrition and sarcopenia derived from standard thoracic CT scans, such as fat tissue amount and disposition, muscle mass, or muscle density were also analyzed in the setting of COVID-19, with most protocols aiming to extrapolate data typically measured on abdominal imaging [ 15 , 16 , 17 ].…”

A comparison of CT derived body composition at thoracic T4, T12 with lumbar L3 vertebral levels in patients with rectal cancer – which one should we utilise?

“…This therefore led to a poorer reproducibility as it was not clear as to where the boundaries of the muscles around the scapula and arm might be. Previous studies encountered a similar such problem and overcame this by including only the pectorals, intercostals and muscles of the back in their CSA measurements (20,21). The variation of the partial exclusion of the muscles seen in the scans at T4 indicates that this level may not be best as the SMI measures would not be reproducible if a patient was to have subsequent scans.…”

Measurement of Sarcopenia in Head and Neck Cancer Patients and Its Association With Frailty

“…CSMA at level Th4 strongly correlates with L3 CSMA (r = 0.791). A multivariate model (prediction formula) incorporating the patient characteristics arm positioning (downwards or upwards), age, sex, and weight achieved an even stronger correlation (r = 0.856) ( 47 ). It can be concluded that CSMA measured at these levels is a feasible alternative to measurements at L3, particularly when assessment at level C3 is not possible.…”