Muscle-associated triglyceride measured by computed tomography and magnetic resonance spectroscopy

Objective: Muscle triglyceride can be assessed in vivo using computed tomography (CT) and H-1 magnetic resonance spectroscopy (MRS), two techniques that are based on entirely different biophysical principles. Little is known, however, about the cross-correlation between these techniques and their test-retest reliability. Research Methods and Procedures: We compared mean muscle attenuation (MA) in soleus and tibialis anterior (TA) muscles measured by CT with intra- and extramyocellular lipids (IMCL and EMCL, respectively) measured by MRS in 51 volunteers (26 to 72 years of age, BMI = 25.5 to 39.3 kg/m(2)). MA of midthighs was also measured in a subset (n = 19). Test-retest measurements were performed by CT (n = 6) and MRS (n, 10) in separate sets of volunteers. Results: MA of soleus was significantly associated with IMCL (r = -0.64) and EMCL, which by multiple regression analysis was explained mostly by IMCL (p < 0.001) rather than EMCL (beta = -0.010, p = 0.94). Muscle triglyceride was lower in TA than in soleus, and MA of TA was significantly correlated with EMCL (r = -0.40) but not IMCL (r = -0.16). By CT, MA of midthighs was correlated with MA in soleus (r = 0.40, p = 0.07) and whole calf (r = 0.62, p < 0.05). Finally, both MA and IMCL were highly reliable in soleus (coefficient of variation = <2% and 6.7%, respectively) and less reliable in TA (4% and 10%, respectively). Discussion: These results support the use of both CT and MRS as reliable methods for assessing skeletal muscle lipid.