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computed tomography (ct) and magnetic resonance imaging (MRi) can quantify muscle mass and quality. However, it is still unclear if ct and MRi derived measurements can be used interchangeable. In this prospective study, fifty consecutive participants of a cancer screening program underwent same day low-dose chest ct and MRi. cross-sectional areas (cSA) of the paraspinal skeletal muscles were obtained. CT and MRI muscle fat infiltration (MFI) were assessed by mean radiodensity in Hounsfield units (HU) and proton density fat fraction (MRi pDff), respectively. cSA and Mfi were highly correlated between CT and MRI (CSA: r = 0.93, P < 0.001; MFI: r = − 0.90, P < 0.001). Mean CSA was higher in CT compared to MRI (46.6cm 2 versus 43.0cm 2 ; P = 0.05) without significance. Based on MRI pDff , a linear regression model was established to directly estimate skeletal muscle fat content from ct. Bland-Altman plots showed a difference between measurements of − 0.5 cm 2 to 7.6 cm 2 and − 4.2% to 2.4% regarding measurements of cSA and Mfi, respectively. in conclusion, the provided results indicate interchangeability of ct and MRi derived imaging biomarkers of skeletal muscle quantity and quality. comparable to MRi pDff , skeletal muscle fat content can be quantified from CT, which might have an impact of analyses in larger cohort studies, particularly in sarcopenia patients. Decrease in skeletal muscle quantity and quality, commonly termed sarcopenia, is known as a strong risk factor for adverse outcomes in several chronic and malignant diseases. Sarcopenia was shown to have high socioeconomic and personal burden and leads to impaired activity in daily life, decreased mobility, loss of independency and a higher mortality 1-3. Initially, sarcopenia was considered to be an age-related phenomenon 4. However, it is now increasingly realized that sarcopenia may also occur in younger patients, for example secondary due to systemic diseases. Moreover, it was realized that sarcopenia may not be captured by conventional anthropometric measurements such as body mass index (BMI) or waist-to-hip-ratio, particularly in obese patients 1,5. Amount and quality of skeletal muscles can be assessed by cross-sectional imaging modalities such as computed tomography (CT) and magnetic resonance imaging (MRI). Previous studies indicate that both modalities may provide imaging based quantitative biomarkers of sarcopenia, and that these biomarkers may reveal prognostic information in various severe diseases 6-10. Thereby, cross sectional areas (CSA) of skeletal muscles at distinct anatomical landmarks were shown to provide accurate surrogates of total skeletal muscle amount and therefore may be used to identify patients with low muscle mass 1,6,7. The most common approaches to estimate skeletal muscle amount are determination of circumferential skeletal muscle area or psoas muscle area, both typically obtained at lumbar vertebral levels 1. However, these landmarks are frequently not captured in several imaging protocols, although sarcopenia is known to b...

Background Myocardial injury and inflammation on cardiac MRI in patients suffering from coronavirus disease 19 (COVID-19) have been described in recent publications. Concurrently, a chronic COVID-19 syndrome (CCS) after COVID-19 infection has been observed manifesting with symptoms like fatigue and exertional dyspnea. Purpose To explore the relationship between CCS and myocardial injury and inflammation as an underlying cause of the persistent complaints in previously healthy individuals. Materials and Methods In this prospective study from January 2021 to April 2021, study participants without known cardiac or pulmonary diseases prior to COVID-19 infection with persisting CCS symptoms like fatigue or exertional dyspnea after convalescence and healthy control participants underwent cardiac MRI. Cardiac MRI protocol included T1 and T2 relaxation times, extracellular volume (ECV), T2 signal intensity ratio, and late gadolinium enhancement (LGE). Student t test, Mann-Whitney U test, and χ 2 test were used for statistical analysis. Results 41 participants with CCS (39±13 years; 18 men) and 42 control participants (39±16 years; 26 men) were evaluated. Median time between initial mild to moderate COVID-19 disease without hospitalization and cardiac MRI was 103 days (interquartile range: 88-158). Troponin T levels were normal. Parameters indicating myocardial inflammation and edema were comparable between participants with CCS and control participants: T1 relaxation time (978±23 ms vs 971±25 ms; P=.17), T2 relaxation time (53±2 ms vs 52±2 ms; P=.47), T2 signal intensity ratio (1.6±0.2 vs 1.6±0.3; P=.10). Visible myocardial edema was present in none of the participants. Three of 41 (7%) participants with CCS demonstrated non-ischemic LGE compared to none in the control group (0 of 42 [0%]; P=.07). None of the participants fulfilled the 2018 Lake Louise criteria for the diagnosis of myocarditis. Conclusion Individuals without hospitalization for COVID-19 and with CCS did not demonstrate signs of active myocardial injury or inflammation on cardiac MRI. See also the editorial by Lima and Bluemke .

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