Preliminary Study Of Functional Magnetic Resonance Imaging On Placenta Accreta

Part 1 The evaluation of oxygenation function in the normal placenta and placenta accreta by BOLD-MRIObjective: Our study aimed to investigate the changes of oxygenation level and its distribution characteristics in normal placenta after hyper-oxygen inhalation,and to explore the effect of the placenta accreta on placental oxygenation function preliminarily.Methods: Total 25 cases of normal placenta and placenta accreta were prospectively included in this study.16 cases were confirmed of the normal placenta and 9 cases were placenta accreta by pathology / operation.All patients performed BOLD-MRI examinations for 10 minutes.Pregnant women breathed room air during the first 3 minutes and oxygen for the last 7 minutes by mask.The region of interesting(ROI)was sketched by post-processing workstation of Siemens.The normal placenta was sketched the global placenta(Nor-p),the placenta-uterus side(Nor-u)and the placenta-fetal side(Nor-f)respectively in two planes well displayed.The implanted placenta sketched the global placenta(Imp-p)in well-displayed planes including the implanted site,and also the placenta-uterus side(Imp-u)and the placenta-fetal side(Imp-f)respectively.The renal parenchyma of pregnant women was sketched as Pre-r.The BOLD signal values increasing over time of each ROI was obtained and the signal increment percentage(?BOLD%)was calculated.The ?BOLD%-time curves were drawn by spss24.The differences of ?BOLD% in last 3min of groups were compared.Independent sample t test was used between the normal and implanted placenta,paired sample t test was used between the two sides of placenta.Results: After oxygen inhalation,the ?BOLD%-time curves increased significantly during 4-7min of each ROI except for Pre-r.Then it leveled off.The ?BOLD% in the last 3min was obtained as the platform.The mean ?BOLD% of Nor-f(16.25±1.3)%was higher than the Nor-u(12.89±1.2)%.The Imp-p(17.74±1.6)% was higher than Nor-p(14.38±1.2)%.And the ?BOLD% of the Imp-f was higher than that of Imp-u,the ?BOLD% of the Imp-f/ u were higher than those of the Nor-f/ u respectively.The t test showed that there were significant difference between above control groups(p<0.01).Conclusion: BOLD-MRI can assess the physiological oxygenation status of the placenta and has a potential to detect changes of placental oxygenation.Moreover,implanted placenta lesions have no obvious damage to the oxygenation function of placental villi,which provides a certain basis for no clinical intervention of oxygen supply for cases of placenta accreta.Part 2 Investigation of the value of diffusion-weighted imaging of intravoxel incoherent motion imaging for the diagnosis of placenta accretaPurpose: To investigate the diagnostic value of intravoxel incoherent motion(IVIM)diffusion-weighted imaging(DWI)by comparing the diffusion and perfusion characteristics between invasive placenta(IP)and normal placenta(NP).Methods: Twenty-four pregnant women with IP at 24-36.4 weeks and 25 cases with NP at 26-37 weeks underwent 3 T MR examination with IVIM-DWI of 7 different b values(0,50,100,150,400,700,1000 s/mm2).The perfusion percentage(f),pseudo-diffusion coefficient(D *),and diffusion coefficient(D)values were calculated from regions of interest(ROIs): entire placenta of NP(NP-ROI)and IP(IP-ROI),the implanted placental region(IPr-ROI)and non-implanted placental region(NIPr-ROI)of IP.The differences between the NP-ROIs and IP-ROIs were compared by covariance analysis,while the IPr-ROIs and NIPr-ROIs by paired-sample t-test.The Receiver operating characteristic curves(ROC)were produced to evaluate the values of parameters for predicting IP.Results: The values of f(45.0±7.63)% and D*(11.64±2.15)mm2/s in the IP-ROIs were significantly higher than those in the NP-ROIs(31.85±5.96)% and(9.04±3.13)mm2/s(p < 0.05),as well as in IPr-ROIs(55.52 ± 8.14%),(13.27 ± 3.58 mm2/s)compared with those in NIPr-ROIs(36.19 ± 4.63 %),(10.70 ± 3.02 mm2/s)(p < 0.05).There were significant differences of the D values between IPr-ROIs and NIPr-ROIs(p =0.035),but not between the IP-ROIs and NP-ROIs(p > 0.05).The Area Under the Curve(AUC)of the f,D* and D from the ROC curves for predicting IP were 0.93,0.79 and 0.40,respectively.Conclusion: These results suggested that the parameters of IVIM could quantitatively evaluate the perfusion and diffusion characteristics of the placenta.IVIM may be a useful functional technique with good performance to diagnose IP.