Evaluation of intra-cellular lipid of skeletal muscle by 《'1》H-MR spectroscopy: in vivo and phantom study

Objective To elucidate the spectrum of lipid peaks in 1H-MRS of skeletal muscle and it's interpretation,to investigate the utility of 1H-MRS in evaluating intramyecellular lipid (IMCL).Methods 1H-MRS was acquired in vivo on tibialis anterior muscle (TA) and soleus muscle (S) on 5 healthy volunteers.The spectrum of the lipid peak between 0.80 and 1.80 ppm was observed with different angle between the long axis of the calf and B0.Ex vivo phantom was an cluster of capillary tubers filled with soybean oil and fat emulsion,simulating the extramyecellular lipid (EMCL) and IMCL,respectively.The spectra of the lipid peaks were compared using different angles between the phantom and Bo field.Results The lipid spectrum split to 3 to 4 peaks between 0.80 and 1.80 ppm on calf muscles,with 0.20 to 0.30 ppm interval between each neighbouring peak.The methylene peak of EMCL shifted to the right when the angle between long axis of the calf and B0 increased.The phantom could simulate the spectrum of 1H-MRS of the muscle,presenting two peaks with 0.20 to 0.30 ppm chemical shift difference between 0.80 and 1.80 ppm.They are methyl triglyceride and methylene,representing IMCL and EMCL,respectively.The peak splitting could be attributed to the high ordered muscle fibers and their chemical shift difference between inta-and extra-cellular distribution.The interval of IMCL and EMCL peaks attenuated when the angle between the muscle fiber and B0 increased from 0 to the magic angle(54.7°).Conclusion On 1H- MRS spectrum,the peak of the EMCL and IMCL splits.This indicated that 1H-MRS is an applicable method to detect IMCL noninvasively.TA is an optimizing muscle for 1H-MRS study. Key words: Magnetic resonance spectroscopy;  Skeletal muscle;  Phantom study;  Triglyceride; Myocellular lipid