Tissue characterization of uterine fibroids with an intravoxel incoherent motion model: The need for T 2 correction

Background Diminished signal intensity of uterine fibroids in T 2 ‐weighted images is routinely used as a qualitative marker of fibroid hypoperfusion. However, quantitative classification of fibroid perfusion with intravoxel incoherent motion (IVIM) model‐based metrics is not yet clinically accepted. Purpose To investigate the influence of T 2 correction on the estimation of IVIM model parameters for characterizing uterine fibroid tissue. Study Type Prospective. Population Fourteen women with 41 fibroids (12 Type I and 29 Type II, per Funaki classification) underwent diffusion‐weighted imaging and T 2 mapping. Field Strength Diffusion‐weighted images ( b values: 0, 20, 40, 60, 100, 200, 400, 600, 800, 1000 s/mm 2 ) and T 2 maps were obtained at 1.5T. Assessment The effect of uterine fibroid T 2 variation on IVIM model parameters (diffusion coefficient, perfusion coefficient, and perfusion volume fraction) were numerically modeled and experimentally evaluated without ( D, D*, f ) and with ( D c ,D c * , f c ) T 2 correction. The relationship of T 2 with D and the T 2 ‐corrected perfusion volume fraction ( f c ) was also examined. Statistical Test D‐ values and f‐ values estimated with and without T 2 correction were compared by using a two‐tailed Student's t ‐test. Results Type II fibroids had higher D and f than Type I fibroids, but the differences were not significant (Type I vs. Type II, D : 0.83 ± 0.20 vs. 0.80 ± 0.25 mm 2 /s, P  = 0.78; f : 23.64 ± 4.87% vs. 25.27 ± 7.46%, P  = 0.49). For Type I and Type II fibroids, f c was lower than f , and f c of Type II fibroids was significantly higher than that of Type I fibroids (Type I vs. Type II, f c : 7.80 ± 1.88% vs. 11.82 ± 4.13%, P  = 0.003). Both D and f c exponentially increased with the increase of fibroid T 2 as functions:D c ( T 2 ) = − 1.52 × 10 − 3 ⋅ e − 3.42T 2290+ 1.84 × 10 − 3andf c ( T 2 ) = − 0.2336 ⋅ e − 3.217T 2290+ 0.2269 , respectively. D asymptotically approached 1.79 × 10 −3 mm 2 /s, and f c approached 21.74%. Data Conclusion T 2 correction is important when using IVIM‐based models to characterize uterine fibroid tissue. Level of Evidence : 2 Technical Efficacy : Stage 1 J. Magn. Reson. Imaging 2018;48:994–1001.