Ahmed Gouda1,2, Saqib Basar1,2, Siavash Khallaghi1,2, Javad Khaghani1,2, Saurabh Garg1,2 , Madhurima Datta1,2 ,Yosef Chodakiewitz2, and Sam Hashemi1,2
1 Vigilance Health Imaging Network Inc, Vancouver, Canada
2 Prenuvo Inc, Vancouver, Canada
Purpose:
Establishing normative aging curves is imperative to understand the aging process and allows for interventions when deviations occur, to that end the purpose of this study is to establish the normative curves for the musculoskeletal system of the lower limbs.
Materials and Methods:
T1-weighted whole-body MRI sequences were utilized in two datasets: 72 scans for segmentation and another 21,464 patients for establishing the normative. The deep learning (DL) model quantifies the thigh and calf muscles relative to femur and tibial bones using 3D nnU-Net segmentation. To ensure consistency in 3D sectional measurements, the leg bones and their corresponding muscles were rotated to align with the axial axis. This enabled the division of the lower limb into nine overlapped sections (P1 to P9), with subsequent computation and normalization of muscle volumes based on bone length, as illustrated in Figure A. Regression analysis was performed on the normalized muscle volumes to generate normative curves, which were further stratified by gender and plotted against ages ranging from 18 to 85 years old.
Results:
As depicted in Figure B, Normative analysis shows a decline in thigh muscle volume for both genders from their 30s, with females experiencing earlier reduction in calf muscle volume by their late 40s, and males in their mid-50s. Detailed 3D section analysis reveals more age-related variations than total muscle volumes. Thigh and calf muscle sections farther from the belly continue to decline with age, while the muscle belly increases during the 30s before declining faster afterwards. Similarly, 3D sections covering the gastrocnemius muscle belly increase until age 60 for males and 50 for females, followed by a faster decline.
Conclusion:
DL-based analysis of lower limb muscles provides a powerful means to quantify volume differences across genders and ages. By scrutinizing 3D muscle sections, we gain insights into how muscle volumes change at different parts of the muscle.
Clinical Relevance Statement:
3D segmental and whole lower limb musculoskeletal analysis aids radiologists in quantifying volume variations in muscle belly, origin and insertion, facilitating muscle degeneration risk assessment. This capability enables longitudinal tracking of volume changes, aiding in the diagnosis of conditions like Muscular Dystrophy and
Amyotrophic Lateral Sclerosis (ALS).
Figure 1: Visualizing 3D Sections from P1 to P9, along with normative curves depicting lower limb volume changes across ages 18 to 85 years.
