Two-Compartment Perfusion MR IVIM Model to Investigate Normal and Pathological Placental Tissue

J Magn Reson Imaging. 2023 Jun 17. doi: 10.1002/jmri.28858. Online ahead of print.

ABSTRACT

BACKGROUND: Perfusion and diffusion coexist in the placenta and can be altered by pathologies. The two-perfusion model, where f₁ and, f₂ 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/mm² -mono-exponential decay fit. IVIM metrics were quantified to fix f₁ + f₂ = 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<0.05 indicated a statistically significant difference.

RESULTS: There was a significant difference in f₁ between FGR and SGA, and significant differences in f₂ and f_IVIM between normal and FGR. The percreta + increta group showed the highest f₁ values (Cohen’s d = -2.66). The f₂ 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 f₂ 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 f₂ 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.

PMID:37329218 | DOI:10.1002/jmri.28858