Functional diagnosis of placenta accreta by intravoxel incoherent motion model diffusion-weighted imaging.

OBJECTIVES: To investigate the diagnostic value of intravoxel incoherent motion (IVIM) DWI for placenta accreta by comparing diffusion and perfusion characteristics of placentas with accreta lesions (APs) with those of normal placentas (NPs).

METHODS: Twenty-five pregnant women with AP and 24 with NP underwent 3-T magnetic resonance examinations with IVIM-DWI. The perfusion percentage (f), pseudo-diffusion coefficient (D*), and diffusion coefficient (D) values were calculated from different ROIs: the entire-plane of the AP (AP-ROI) and NP (NP-ROI) and the implanted (IR-ROI) and non-implanted region (NIR-ROI) of the AP. The AP-ROIs and NP-ROIs were compared using covariance analysis; the IR-ROIs and NIR-ROIs were compared using the Wilcoxon signed-rank test. ROC curves were produced to evaluate the parameters for predicting placenta accreta.

RESULTS: The f and D* values for the AP-ROIs ([45.0 ± 7.63]%, [11.64 ± 2.15]mm2 /s) were significantly higher than those for the NP-ROIs ([31.85 ± 5.96]%, [9.04 ± 3.13]mm2 /s) (both p < 0.05); the IR-ROIs (54.8%, 14.03 mm2 /s) were also significantly higher than the NIR-ROIs (37.4%, 11.4 mm2 /s) (both p < 0.05). No significant differences were found between the D values of the AP-ROIs and NP-ROIs (p > 0.05) or of the IR-ROIs and NIR-ROIs (p > 0.05). The areas under the curve for f and D* of the ROC curves were 0.93 and 0.79, respectively.

CONCLUSIONS: These results suggest that the IVIM parameters f and D* can be used to quantitatively evaluate the higher perfusion of AP when compared with NP. Furthermore, IVIM may be a useful functional diagnostic technique to predict placenta accreta.

KEY POINTS: • Intravoxel incoherent motion (IVIM) may be a useful diagnostic technique to quantitatively estimate the perfusion of the placenta. • The perfusion percentage (f) and pseudo-diffusion coefficient (D*) values differed significantly between placentas with accreta lesions and normal placentas. • ROC curves showed that perfusion percentage (f) and pseudo-diffusion coefficient (D*) values could accurately predict placenta accreta.