Two‐Compartment Perfusion <scp>MR IVIM</scp> Model to Investigate Normal and Pathological Placental Tissue

Abstract

Background Perfusion and diffusion coexist in the placenta and can be altered by pathologies. The two‐perfusion model, where f 1 and, f 2 are the perfusion‐fraction of the fastest and slowest perfusion compartment, respectively, and D is the diffusion coefficient, may help differentiate between normal and impaired placentas. Purpose Investigate the potential of the two‐perfusion IVIM model in differentiating between normal and abnormal placentas. Study‐Type Retrospective, case–control. Population 43 normal pregnancy, 9 fetal‐growth‐restriction (FGR), 6 small‐for‐gestational‐age (SGA), 4 accreta, 1 increta and 2 percreta placentas. Field Strength/Sequence Diffusion‐weighted‐echo planar imaging sequence at 1.5 T. Assessment Voxel‐wise signal‐correction and fitting‐controls were used to avoid overfitting obtaining that two‐perfusion model fitted the observed data better than the IVIM model (Akaike weight: 0.94). The two‐perfusion parametric‐maps were quantified from ROIs in the fetal and maternal placenta and in the accretion zone of accreta placentas. The diffusion coefficient D was evaluated using a b ≥ 200 sec/mm 2 ‐mono‐exponential decay fit. IVIM metrics were quantified to fix f 1 + f 2 = f IVIM . Statistical‐Tests ANOVA with Dunn‐Sidák's post‐hoc correction and Cohen's d test were used to compare parameters between groups. Spearman's coefficient was evaluated to study the correlation between variables. A P ‐value&lt;0.05 indicated a statistically significant difference. Results There was a significant difference in f 1 between FGR and SGA, and significant differences in f 2 and f IVIM between normal and FGR. The percreta + increta group showed the highest f 1 values (Cohen's d = −2.66). The f 2 between normal and percreta + increta groups showed Cohen's d = 1.12. Conversely, f IVIM had a small effective size (Cohen's d = 0.32). In the accretion zone, a significant correlation was found between f 2 and GA ( ρ = 0.90) whereas a significant negative correlation was found between f IVIM and D ( ρ = −0.37 in fetal and ρ = −0.56 in maternal side) and f 2 and D ( ρ = −0.38 in fetal and ρ = −0.51 in maternal side) in normal placentas. Conclusion The two‐perfusion model provides complementary information to IVIM parameters that may be useful in identifying placenta impairment. Level of Evidence 2 Technical Efficacy Stage 1

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