Tissue characterization of uterine fibroids with an intravoxel incoherent motion model: The need for T2 correction.

Abstract

Diminished signal intensity of uterine fibroids in T2 -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. To investigate the influence of T2 correction on the estimation of IVIM model parameters for characterizing uterine fibroid tissue. Prospective. Fourteen women with 41 fibroids (12 Type I and 29 Type II, per Funaki classification) underwent diffusion-weighted imaging and T2 mapping. Diffusion-weighted images (b values: 0, 20, 40, 60, 100, 200, 400, 600, 800, 1000 s/mm2 ) and T2 maps were obtained at 1.5T. The effect of uterine fibroid T2 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 (Dc , , fc ) T2 correction. The relationship of T2 with D and the T2 -corrected perfusion volume fraction (fc ) was also examined. D-values and f-values estimated with and without T2 correction were compared by using a two-tailed Student's t-test. 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 mm2 /s, P = 0.78; f: 23.64 ± 4.87% vs. 25.27 ± 7.46%, P = 0.49). For Type I and Type II fibroids, fc was lower than f, and fc of Type II fibroids was significantly higher than that of Type I fibroids (Type I vs. Type II, fc : 7.80 ± 1.88% vs. 11.82 ± 4.13%, P = 0.003). Both D and fc exponentially increased with the increase of fibroid T2 as functions: and respectively. D asymptotically approached 1.79 × 10-3 mm2 /s, and fc approached 21.74%. T2 correction is important when using IVIM-based models to characterize uterine fibroid tissue. 2 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2018;48:994-1001.