Breath-hold MR measurements of fat fraction, T1, and T2* of water and fat in vertebral bone marrow

PurposeTo assess the feasibility of measuring the fat fraction, T-1 and T-2* relaxation times of water and fat signals in vertebral bone marrow using breath-hold magnetic resonance imaging (MRI) gradient echo images of the spine. Materials and MethodsMRI experiments were performed at 1.5T on eight healthy volunteers (35.1 15.7 years, five men and three women) using two sagittal four-echo 3D gradient echo volumetric interpolated breath-hold examination (VIBE Dixon) sequences acquired at two different flip angles (5 degrees and 15 degrees). The water/fat decomposition was performed in the vertebral bodies of L1 to L5 by fitting the signal to a function that depends on the echo time and the flip angle to calculate the fat fraction (FF) and T-1 and T-2* relaxation times of water and fat signals. Repeatability was assessed by scanning one volunteer six times. ResultsThe mean fat fraction over L1 to L5 was 33 +/- 8%. The mean T-1 and T-2* of water and fat signals were respectively T-1w = 701 +/- 151 msec, T-2*(w) = 13.7 +/- 2.9 msec, T-1f = 334 +/- 113 msec, and T-2*(f) = 11.4 +/- 2.7 msec. When considering each vertebra separately, the fat fraction increased from L1 to L5 and the T-1w decreased from L1 to L5. The mean coefficients of variation obtained from the repeatability study were 8% (FF), 11% (T-1w), 17% (T-1f), 8% (T-2*(w)), and 27% (T-2*(f)). ConclusionThe method introduced in the current study allows for the measurement of the fat fraction and water and fat relaxation times, with a total acquisition time of less than 40 seconds. J. Magn. Reson. Imaging 2016;44:549-555.