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Inverse Association of Longitudinal Variations in Fat Tissue Radiodensity and Area
Giulia Besutti1,2, Marta Ottone3, Efrem Bonelli4
1Radiology Unit, Azienda USL-IRCSS di Reggio Emilia, 42123 Reggio Emilia, Italy.
Diagnostics (Basel, Switzerland)
|July 12, 2025
Summary
Increased fat tissue radiodensity on CT scans may indicate recent weight loss, potentially explaining its link to poor prognosis in cancer patients. This study found inverse associations between fat area and radiodensity variations in COVID-19 survivors.
Area of Science:
- Radiology
- Medical Imaging
- Body Composition Analysis
Background:
- Increased computed tomography (CT)-derived fat tissue radiodensity is linked to poor prognosis in cancer.
- The underlying mechanisms for this association remain unclear.
- One hypothesis suggests increased radiodensity reflects adipocyte fat droplet loss, indicating recent weight loss.
Purpose of the Study:
- To investigate the association between longitudinal changes in fat tissue radiodensity and fat area.
- To test the hypothesis that increased radiodensity is a proxy for weight loss.
- To evaluate these associations in a cohort of severe COVID-19 pneumonia survivors.
Main Methods:
- Retrospective review of baseline and follow-up chest CT scans (2-3 months) from 196 COVID-19 survivors.
- Measurement of subcutaneous adipose tissue (SAT), visceral adipose tissue (VAT), and intermuscular adipose tissue (IMAT) areas and densities at the T7-T8 vertebrae.
- Calculation of longitudinal variations and evaluation of associations using linear models adjusted for age and sex.
Main Results:
- Longitudinal variations in SAT area were inversely associated with SAT radiodensity variations (adjusted coefficient [coeff] -0.89, p=0.03).
- A similar, stronger inverse association was observed for IMAT (adjusted coeff -2.1, p<0.01).
- No significant association was found for VAT.
Conclusions:
- Longitudinal changes in subcutaneous and intermuscular adipose tissue area and density are inversely related.
- Decreased fat area (weight loss) may contribute to increased adipose tissue radiodensity.
- This finding supports the hypothesis that increased fat radiodensity reflects weight loss, potentially explaining its prognostic significance in oncological settings.
