Influence of weight-adjusted contrast enhancement on CT-derived skeletal muscle measures: A retrospective proof-of concept comparative study between Danish females and males.

BACKGROUND: Computed Tomography (CT) has an underutilized potential for evaluating body composition in clinical settings. Often conducted with intravenous contrast (IVC), CT scans yield unused body composition data due to unclear effects on skeletal muscle area (SMA), skeletal muscle index (SMI), and muscle density (SMD). OBJECTIVE: This study investigates whether weight-adjusted IVC influences SMA, SMI, and SMD differently in female and male compared to non-contrast abdominal CT. Additionally, the study explores associations between contrast and non-contrast assessed SMA, SMI, SMD, and demographic factors. METHODS: A comparative observational retrospective study was conducted on Danish patients who underwent consecutive four-phased contrast-enhanced abdominal CT scans (non-contrast, arterial, venous, and late venous phases). Muscle measures were evaluated using validated semi-automated threshold-based software by three independent raters. RESULTS: The study included 72 patients (51 male, 21 female) with a mean age of 59 (55, 62) years. Weight-adjusted IVC increased SMA by up to 3.28 cm2 (CI: 2.58, 3.98) corresponding to 2.4% (1.8, 2.9) in late venous phase compared to non-contrast CT. Analysis between sexes showed no difference in the effects of IVC on SMA and SMI between female and male. However, females exhibited a higher increase in SMD during the venous by a mean of 1.7 HU 0.9; 2.5) and late venous phases with a mean HU of 1.80 (1.0; 2.6) compared to males. Multivariate regression analysis indicated an association between the differences in SMD and sex during venous (-1.38 , 95%CI: - 2.48, -0.48) and late venous phases (-1.23, 95% CI: -2.27, -0.19) CONCLUSION: Weight-adjusted IVC leads to increased SMA, SMI, and SMD. While SMA and SMI differences were consistent across the sexes, females exhibited a significantly higher SMD increase than male in the venous and late venous phases. Further investigations are necessary to determine the applicability of SMD as a muscle quality proxy in IVC CT scans.

Association between the Static and Dynamic Lung Function and CT-Derived Thoracic Skeletal Muscle Measurements-A Retrospective Analysis of a 12-Month Observational Follow-Up Pilot Study.

BACKGROUND: Patients with chronic obstructive pulmonary disease (COPD) with low skeletal muscle mass and severe airway obstruction have higher mortality risks. However, the relationship between dynamic/static lung function (LF) and thoracic skeletal muscle measurements (SMM) remains unclear. This study explored patient characteristics (weight, BMI, exacerbations, dynamic/static LF, sex differences in LF and SMM, and the link between LF and SMM changes. METHODS: A retrospective analysis of a 12-month prospective follow-up study patients with stable COPD undergoing standardized treatment, covering mild to severe stages, was conducted. The baseline and follow-up assessments included computed tomography and body plethysmography. RESULTS: This study included 35 patients (17 females and 18 males). This study revealed that females had more stable LF but tended to have greater declines in SMM areas and indices than males (-5.4% vs. -1.9%, respectively), despite the fact that females were younger and had higher LF and less exacerbation than males. A multivariate linear regression showed a negative association between the inspiratory capacity/total lung capacity ratio (IC/TLC) and muscle fat area. CONCLUSIONS: The findings suggest distinct LF and BC progression patterns between male and female patients with COPD. A low IC/TLC ratio may predict increased muscle fat. Further studies are necessary to understand these relationships better.

Ethnic differences in CT derived abdominal body composition measures: a comparative retrospect pilot study between European and Inuit study population.

Understanding ethnic variations in body composition is crucial for assessing health risks. Universal models may not suit all ethnicities, and there is limited data on the Inuit population. This study aimed to compare body composition between Inuit and European adults using computed tomography (CT) scans and to investigate the influence of demographics on these measurements. A retrospective analysis was conducted on 50 adults (29 Inuit and 21 European) who underwent standard trauma CT scans. Measurements focused on skeletal muscle index (SMI), various fat indices, and densities at the third lumbar vertebra level, analyzed using the Wilcoxon-Mann-Whitney test and multiple linear regression. Inuit women showed larger fat tissue indices and lower muscle and fat densities than European women. Differences in men were less pronouncehd, with only Intramuscular fat density being lower among Inuit men. Regression indicated that SMI was higher among men, and skeletal muscle density decreased with Inuit ethnicity and age, while visceral fat index was positively associated with age. This study suggests ethnic differences in body composition measures particularly among women, and indicates the need for Inuit-specific body composition models. It higlights the importance of further research into Inuit-specific body composition measurements for better health risk assessment.

Association between thoracic and third lumbar CT-derived muscle mass and density in Caucasian patients without chronic disease: a proof-of-concept study.

BACKGROUND: Computed tomography (CT) is increasingly used in the clinical workup, and existing scan contains unused body composition data, potentially useful in a clinical setting. However, there is no healthy reference for contrast-enhanced thoracic CT-derived muscle measures. Therefore, we aimed at investigating whether there is a correlation between each of the thoracic and third lumbar vertebra level (L3) skeletal muscle area (SMA), skeletal muscle index (SMI), and skeletal muscle density (SMD) at contrast-enhanced CT in patients without chronic disease. METHODS: A proof-of-concept retrospective observational study was based on Caucasian patients without chronic disease, who received CT for trauma between 2012 and 2014. Muscle measures were assessed using a semiautomated threshold-based software by two raters independently. Pearson's correlation between each thoracic level and third lumbar and intraclass correlation between two raters and test-retest with SMA as proxy parameters were used. RESULTS: Twenty-one patients (11 males, 10 females; median age 29 years) were included. The second thoracic vertebra (T2) had the highest median of cumulated SMA (males 314.7 cm2, females 118.5 cm2) and SMI (97.8 cm2/m2 and 70.4 cm2/m2, respectively). The strongest SMA correlation was observed between T5 and L3 (r = 0.970), the SMI between T11 and L3 (r = 0.938), and the SMD between the T10 and L3 (r = 0.890). CONCLUSIONS: This study suggests that any of the thoracic levels can be valid to assess skeletal muscle mass. However, the T5 may be most favourable for measuring SMA, the T11 for SMI, and T10 for SMD when using contrast-enhanced thoracic CT. RELEVANCE STATEMENT: In COPD patients, a CT-derived thoracic muscle mass assessment may help identify who would benefit from focused pulmonary rehabilitation: thoracic contrast-enhanced CT conducted as part of the standard clinical workup can be used for this evaluation. KEY POINTS: • Any thoracic level can be used to assess thoracic muscle mass. • Thoracic level 5 is strongly associated with the 3rd lumbar muscle area. • A strong correlation between the thoracic level 11 and the 3rd lumbar muscle index. • Thoracic level 10 is strongly associated with the 3rd lumbar muscle density.