GRADIENT-ECHO MAGNETIC-RESONANCE SIGNAL DECAY IN A PORCINE VERTEBRAL BODY MODEL - INFLUENCE OF CHEMICAL-SHIFT

Rationale and objectives. This study investigates how magnetic resonan ce (MR) signal and T2 of trabecular bone are affected by chemical shi ft. Methods. Five pigs were sacrificed, and 150 gradient-echo MR image s with increasing echo times (TEs) were obtained of the lumbar spine. Two vertebrae were excised, defatted, and imaged. Commercial fat-prote in emulsions with 40%, 27%, and 15% concentrations of fat were studied . Regions of interest in subcutaneous fat (n = 3), bladder (n = 4), ve rtebral body (n = 10), and defatted vertebral body (n = 10) were used to study de cay of signal intensity. Results. MR signal intensity of t he vertebrae decreased with a superimposed modulation. The periodicity was 4.65 msec (range, 4.60-4.68 msec). At a TE of 0 msec, a phase shi ft of 24 degrees (range, 14 degrees-37 degrees), which corresponds to a shift in TE of 0.31 msec at 1.5 T, was present. In the fat-protein e mulsions, the amplitude of the modulation increased with the amount of fat. Conclusion. Chemical shift and the amount of fat affects T2 mea surements.