Musculoskeletal fat imaging and quantification by high-resolution metabolite cycling magnetic resonance spectroscopic imaging at 3 T: A fast method to generate separate distribution maps of lipid components

Purpose To provide a rapid, non-invasive fat quantification technique capable of producing separate lipid component maps. Methods The calf muscles in 5 healthy adolescents (age 12-16 years; BMI = 20 ± 3 Kg/m 2 ) were scanned by two different fat fraction (FF) quantification methods. A high-resolution, density-weighted concentric ring trajectory (DW-CRT) metabolite cycling (MC) magnetic resonance spectroscopic imaging (MRSI) technique was implemented to collect data with 0.25 mL resolution within 3 minutes and 16 seconds. For comparative purposes, the standard Dixon technique was performed. The two techniques were compared using structural similarity (SSIM) analysis. Additionally, the difference in the distribution of each lipid over the adolescent calf muscles was assessed based on the MRSI data. Results The proposed MRSI technique provided individual FF maps for eight musculoskeletal lipids identified by LCModel analysis (L09, L11, L13, L15, L21, L23, L53, and L55) with mean SSIM indices of 0.19, 0.04, 0.03, 0.50, 0.45, 0.04, 0.07, and 0.12, respectively compared to that of Dixon’s FF map. Further analysis of voxels with zero SSIM demonstrated an increased sensitivity of FF lipid maps from data acquired using this MRSI technique over the standard Dixon technique. The trend of lipid spatial distribution over calf muscles was consistent with previously published findings in adults. Conclusion The advantages of this MRSI technique make it a useful tool when individual lipid FF maps are desired within a short scanning time.