Technical evaluation of in vivo abdominal fat and IMCL quantification using MRI and MRSI at 3 T.
OBJECTIVE
The objectives of this study were to develop protocols that measure abdominal fat and calf muscle lipids with magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS), respectively, at 3 T and to examine the correlation between these parameters and insulin sensitivity.


METHODS
Ten nondiabetic subjects [five insulin-sensitive (IS) subjects and five insulin-resistant (IR) subjects] were scanned at 3 T. Visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) were segmented semiautomatically from abdominal imaging. Intramyocellular lipids (IMCL) in calf muscles were quantified with single-voxel MRS in both soleus and tibialis anterior muscles and with magnetic resonance spectroscopic imaging (MRSI).


RESULTS
The average coefficient of variation (CV) of VAT/(VAT+SAT) was 5.2%. The interoperator CV was 1.1% and 5.3% for SAT and VAT estimates, respectively. The CV of IMCL was 13.7% in soleus, 11.9% in tibialis anterior and 2.9% with MRSI. IMCL based on MRSI (3.8+/-1.2%) were significantly inversely correlated with glucose disposal rate, as measured by a hyperinsulinemic-euglycemic clamp. VAT volume correlated significantly with IMCL. IMCL based on MRSI for IR subjects was significantly greater than that for IS subjects (4.5+/-0.9% vs. 2.8+/-0.5%, P=.02).


CONCLUSIONS
MRI and MRS techniques provide a robust noninvasive measurement of abdominal fat and muscle IMCL, which are correlated with insulin action in humans.
Li
Xiaojuan
X
Musculoskeletal Quantitative Imaging Research, Department of Radiology, University of California, San Francisco, CA 94107, USA. xiaojuan.li@radiology.ucsf.edu <xiaojuan.li@radiology.ucsf.edu>
Youngren
Jack F
JF
Hyun
Ben
B
Sakkas
Giorgos K
GK
Mulligan
Kathleen
K
Majumdar
Sharmila
S
Masharani
Umesh B
UB
Schambelan
Morris
M
Goldfine
Ira D
ID
D050153:Abdominal Fat / Q000033:anatomy & histology*; D000328:Adult; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007333:Insulin Resistance; D007866:Leg; D008055:Lipids / Q000032:analysis*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000378:metabolism*
D008055:Lipids