Gavin Hamilton PhD, Abstract Co-Author: Nothing to Disclose

Michael Simca Middleton PhD, MD, Presenter: Research Consultant, Siemens AG, Erlangen, Germany Research Consultant, Confirma, Inc, Bellevue, WA Grant, General Electric Company Stockholder, General Electric Company Grant, Bayer AG, Montville, NJ

Jeffrey Schwimmer MD, Abstract Co-Author: Nothing to Disclose

Nicholas Pinto, Abstract Co-Author: Nothing to Disclose

Richard Znamirowski BS, Abstract Co-Author: Nothing to Disclose

Claude B. Sirlin MD, Abstract Co-Author: Research grant, Bayer AG, West Haven, CT Research grant, General Electric Company, Fairfield, CT Research grant, Bracco Group

To examine the magnitude of the variability of the T2 of water and fat measured by Liver 1H MR spectroscopy.

The acquisition of liver 1H MRS data at a single TE assumes that T2 variability of the water and fat peaks does not affect the accuracy of hepatic fat quantification. We collected spectra at multiple TEs in subjects with suspected fatty liver to measure the range of T2 seen. Liver MR spectra were obtained on a 1.5T Symphony scanner (Siemens Medical Solutions). STEAM spectra (TR 1500 ms, voxel size 20 x 20 x 20 mm, 6 signal averages) were collected at TE 20, 30, 40, 50 and 60ms. The spectra were quantified in the time domain, using the AMARES (1) algorithm included in MRUI (2). The T2 of the water, CH2 (2.1 ppm), CH2 (1.3 ppm) and CH3 (0.9 ppm) peaks, as well as the composite fat peak (which treats the sum of the individual fat peak areas in the range 0.5-3 ppm as single peak) were calculated by least squares linear fitting log peak area against TE. To ensure enough signal to measure fat T2, only subjects with CH2 (1.3) / Water > 10% were included, giving 20 subjects.

The mean T2 of water was 35.2 ms with a range from 22.4 - 44.1 ms. For the fat peaks the mean and range was as follows: CH2 (2.1 ppm) mean 39.2 ms, range 23.0 - 76.1 ms; CH2 (1.3 ppm) mean 75.5 ms, range 37.0 - 106.2 ms; CH3 (0.9 ppm) mean 45.0 ms, range 27.7 - 78.6 ms; and composite fat mean 64.0 ms, range 35.1 - 92.7ms. There was no correlation between T2s of individual peaks.

There is large range of variability in the T2 of both water and fat. Thus measurement of T2 is may allow more accurate absolute quantification of liver fat.

The accuracy of liver fat level measured by MR Spectroscopy in fatty liver diesease is improved by measuring T2 of fat and water in each patient.

Hamilton, G, Middleton, M, Schwimmer, J, Pinto, N, Znamirowski, R, Sirlin, C, In Vivo Variability of the T2 of Hepatic Fat and Water Measured by MR Spectroscopy.  Radiological Society of North America 2008 Scientific Assembly and Annual Meeting, February 18 - February 20, 2008 ,Chicago IL. http://archive.rsna.org/2008/6019754.html