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Skeletal Muscle Area on CT: Determination of an Optimal Height Scaling Power and Testing for Mortality Risk
Louis Blankemeier1, Lawrence Yao2, Jin Long3
1Department of Electrical Engineering, Stanford University, Stanford, CA.
AJR. American Journal of Roentgenology
|October 25, 2023
Summary
This study suggests using a height scaling power of 1 for skeletal muscle index (SMI) calculations, rather than the conventional power of 2. This revised method improves the prediction of all-cause mortality from CT scans.
Area of Science:
- Radiology
- Gerontology
- Medical Imaging
Background:
- Sarcopenia diagnosis commonly uses skeletal muscle index (SMI) calculated with height squared.
- This method may not be optimal for assessing muscle mass from CT scans.
Purpose of the Study:
- Determine the optimal height scaling power for skeletal muscle area (SMA) on CT.
- Evaluate the impact of this optimal power on SMI's ability to predict mortality.
Main Methods:
- Retrospective analysis of 16,575 patients undergoing abdominal CT.
- Determined optimal height scaling power using allometric and statistical independence analyses.
- Assessed mortality prediction using Cox proportional hazards models.
Main Results:
- Optimal height scaling power varied by age and sex, generally closer to 1 than 2.
- SMI with a height scaling power of 1 showed improved prediction of all-cause mortality in men and women compared to power of 2.
- The concordance index was significantly higher with a scaling power of 1.
Conclusions:
- A height scaling power of 1 is recommended for SMI computation over the conventional power of 2.
- This adjustment can enhance the clinical utility of CT-based sarcopenia assessment for risk stratification.
