Prostate magnetic resonance imaging: Multiexponential T2 decay in prostate tissue

Purpose To investigate the T2 decay in prostate tissue for multiexponentiality and to assess how the biexponential model relates to established T2W contrast. Materials and Methods A 32‐echo spin‐echo sequence was performed on 16 volunteers. Six single‐voxel decay curves were sampled from each prostate. Prediction accuracies were assessed by jackknifing for the mono‐, bi‐, and triexponential models. The differences were evaluated by cross‐validated analysis of variance (CVANOVA). Multiple linear regression was performed to assess the relation between parameters in the biexponential model and the contrast in T2W images. Results Mono‐, bi‐, and triexponential models were preferred in 8 (10%), 72 (86%), and 4 (5%) cases, respectively. The biexponential short T2 was 64 msec (range 43 to 92 msec) and the long T2 was 490 msec (range 161 to 1319 msec). The fitted signal fraction, f, of the long T2 component was 27% (range 3% to 80%). The adjusted R2 was 75.1% for the full regression model and decreased by 0.9%, 1.3%, and 39.2% when short T2, long T2, and f were removed from the model, respectively. Conclusion Prostatic T2 decay was, in general, biexponential. The differences between the T2 components were large enough for accurate quantification. The T2W image contrast was primarily predicted by the biexponential signal fractions. J. Magn. Reson. Imaging 2008;28:1166–1172. © 2008 Wiley‐Liss, Inc.