Magnetic resonance imaging with true fast imaging with steady-state precession and half-Fourier acquisition single-shot turbo spin-echo sequences in cases of suspected placenta accreta

Bladder involvement in placenta accreta spectrum disorder with placenta previa: MRI findings and outcomes correlation

BACKGROUND

Placental accreta spectrum (PAS) disorder with bladder involvement can be associated with maternal and neonatal morbidity. Magnetic resonance imaging (MRI) may provide accurate preoperative diagnoses.

OBJECTIVE

This study had 2 aims: to retrospectively review the MRI findings for bladder involvement in PAS with placental previa and to correlate bladder involvement with maternal and neonatal outcomes.

MATERIALS AND METHODS

MRI images of 48 patients with severe PAS (increta and percreta) with placenta previa/low-lying placenta were evaluated by 2 experienced radiologists blinded to the final diagnoses. Nine MRI findings and stepwise logistic regression analysis were assessed to identify predictive MRI findings for bladder involvement. The correlations between PAS patients with bladder involvement and clinical outcomes were analyzed using Fisher's exact test.

RESULTS

Of the 48 patients, 27 did not have bladder involvement, while 21 did. Logistic regression analysis identified 2 predictive MRI features for bladder involvement. They were abnormal vascularization (OR,6.94; 95 %CI,1.05-45.75) and loss of the chemical shift line at the uterovesical interface (OR, 4.41; 95 %CI, 0.63-30.98). The sensitivity and specificity of the combined MRI features were 38.1 % and 100 %, respectively (p = 0.001). A significant correlation was found between bladder involvement and massive blood loss during surgery (p = 0.022).

CONCLUSIONS

PAS with bladder involvement was significantly correlated with massive surgical blood loss. Prenatally, the disorder was predicted with high specificity by the combination of loss of chemical shift artifacts in the steady-state free precession sequence and abnormal vascularization at the uterovesical interface on MRI.

Assessment of postpartum haemorrhage for placenta accreta: Is measurement of myometrium thickness and dark intraplacental bands using MRI helpful?

Background

This study aimed to investigate the predictive values of magnetic resonance imaging (MRI) myometrial thickness grading and dark intraplacental band (DIB) volumetry for blood loss in patients with placenta accreta spectrum (PAS).

Methods

Images and clinical data were acquired from patients who underwent placenta MRI examinations and were diagnosed with PAS from March 2015 to January 2021. Two radiologists jointly diagnosed, processed, and analysed the MR images of each patient. The analysis included MRI-based determination of placental attachment, as well as myometrial thickness grading and DIB volumetry. The patients included in the study were divided into three groups according to the estimated blood loss volume: in the general blood loss (GBL) group, the estimated blood loss volume was < 1000 ml; in the massive blood loss (MBL) group, the estimated blood loss volume was ≥ 1000 ml and < 2000 ml; and in the extremely massive blood loss (ex-MBL) group, the estimated blood loss volume was ≥ 2000 ml. The categorical, normally distributed, and non-normally distributed data were respectively analysed by the Chi-square, single-factor analysis of variance, and Kruskal–Wallis tests, respectively. The verification of correlation was completed by Spearman correlation analysis. The evaluation capabilities of indicators were assessed using receiver operating characteristic curves.

Results

Among 75 patients, 25 were included in the GBL group, 26 in the MBL group, and 24 in the ex-MBL group. A significant negative correlation was observed between the grade of myometrial thickness and the estimated blood loss (P < 0.001, ρ = − 0.604). There was a significant positive correlation between the volume of the DIB and the estimated blood loss (P < 0.001, ρ = 0.653). The areas under the receiver operating characteristic curve of the two MRI features for predicting blood loss ≥ 2000 ml were 0.776 and 0.897, respectively.

Conclusions

The grading and volumetric MRI features, myometrial thickness, and volume of DIB, can be used as good prediction indicators of the risk of postpartum haemorrhage in patients with PAS.

Treatment of Placenta Increta With High-Intensity Focused Ultrasound Ablation and Leaving the Placenta in situ: A Multicenter Comparative Study

Objective

To explore the feasibility of simple high-intensity focused ultrasound (HIFU) ablation for placenta increta.

Methods

Ninety-five patients after a vaginal delivery were enrolled in this retrospective cohort study, 53 patients were treated with simple HIFU ablation, and 42 patients were treated with HIFU followed by uterine curettage.

Results

All 95 patients were successfully treated with a single-session HIFU procedure, and in the control group, the necrotic placental tissue was removed with curettage. Vaginal hemorrhage did not occur in either group. The duration of bloody lochia was 25.9 ± 8.6 days in the sHIFU group and 24.2 ± 8.8 days in the control group (P > 0.05). The median serum human chorionic gonadotropin (HCG) level was 3,222 mIU/mL and 2,838 mIU/mL in the sHIFU and control groups, respectively, which decreased and returned to normal within 30 days, and the differences were not significantly on comparing the blood HCG level in the two groups at 7, 15, and 30 days after HIFU (all P > 0.05). Decreased menstrual volume occurred in 85.71% of patients in the control group, which was higher than that in the sHIFU group (23.08%) (χ² = 6.839, P < 0.001). During 2–8 years of follow-up, six pregnancies occurred in the sHIFU group without any recurrence of placenta increta, three pregnancies occurred in the control group, and one patient developed a repeat placenta increta.

Conclusion

Simple HIFU treatment is safe and effective for postpartum placenta increta and leaving the placenta in situ. It is a promising option for patients who wish to preserve their fertility and conceive.

The history of magnetic resonance imaging and its reflections in Acta Radiologica

The first reports in Acta Radiologica on magnetic resonance imaging (MRI) were published in 1984, four years after the first commercial MR scanners became available. For the first two years, all MR papers originated from the USA. Nordic contributions started in 1986, and until 2020, authors from 44 different countries have published MR papers in Acta Radiologica. Papers on MRI have constituted, on average, 30%-40% of all published original articles in Acta Radiologica, with a high of 49% in 2019. The MR papers published since 1984 document tremendous progress in several areas such as magnet and coil design, motion compensation techniques, faster image acquisitions, new image contrast, contrast-enhanced MRI, functional MRI, and image analysis. In this historical review, all of these aspects of MRI are discussed and related to Acta Radiologica papers.

Magnetic Resonance Imaging of Placenta Accreta Spectrum: A Step-by-Step Approach

Placenta accreta spectrum (PAS) is an abnormal placental adherence or invasion of the myometrium or extrauterine structures. As PAS is primarily staged and managed surgically, imaging can only guide and facilitate diagnosis. But, imaging can aid in preparations for surgical complexity in some cases of PAS. Ultrasound remains the imaging modality of choice; however, magnetic resonance imaging (MRI) is required for evaluation of areas difficult to visualize on ultrasound, and the assessment of the extent of placenta accreta. Numerous MRI features of PAS have been described, including dark intraplacental bands, placental bulge, and placental heterogeneity. Failure to diagnose PAS carries a risk of massive hemorrhage and surgical complications. This article describes a comprehensive, step-by-step approach to diagnostic imaging and its potential pitfalls.

Nonfetal Imaging During Pregnancy: Placental Disease

Placenta is a vital organ that connects the maternal and fetal circulations, allowing exchange of nutrients and gases between the two. In addition to the fetus, placenta is a key component to evaluate during any imaging performed during pregnancy. The most common disease processes involving the placenta include placenta accreta spectrum disorders and placental masses. Several systemic processes such as infection and fetal hydrops can too affect the placenta; however, their imaging features are nonspecific such as placental thickening, heterogeneity, and calcifications. Ultrasound is the first line of imaging during pregnancy, and MR imaging is reserved for problem solving, when there is need for higher anatomic resolution.

Society of Abdominal Radiology (SAR) and European Society of Urogenital Radiology (ESUR) joint consensus statement for MR imaging of placenta accreta spectrum disorders

OBJECTIVES

This study was conducted in order to establish the joint Society of Abdominal Radiology (SAR) and European Society of Urogenital Radiology (ESUR) guidelines on placenta accreta spectrum (PAS) disorders and propose strategies to standardize image acquisition, interpretation, and reporting for this condition with MRI.

METHODS

The published evidence-based data and the opinion of experts were combined using the RAND-UCLA Appropriateness Method and formed the basis for these consensus guidelines. The responses of the experts to questions regarding the details of patient preparation, MRI protocol, image interpretation, and reporting were collected, analyzed, and classified as "recommended" versus "not recommended" (if at least 80% consensus among experts) or uncertain (if less than 80% consensus among experts).

RESULTS

Consensus regarding image acquisition, interpretation, and reporting was determined using the RAND-UCLA Appropriateness Method. The use of a tailored MRI protocol and standardized report was recommended.

CONCLUSIONS

A standardized imaging protocol and reporting system ensures recognition of the salient features of PAS disorders. These consensus recommendations should be used as a guide for the evaluation of PAS disorders with MRI.

KEY POINTS

• MRI is a powerful adjunct to ultrasound and provides valuable information on the topography and depth of placental invasion. • Consensus statement proposed a common lexicon to allow for uniformity in MRI acquisition, interpretation, and reporting of PAS disorders. • Seven MRI features, namely intraplacental dark T2 bands, uterine/placental bulge, loss of low T2 retroplacental line, myometrial thinning/disruption, bladder wall interruption, focal exophytic placental mass, and abnormal vasculature of the placental bed, reached consensus and are categorized as "recommended" for diagnosing PAS disorders.

MRI evaluation of the placenta from normal variants to abnormalities of implantation and malignancies

Even though the placenta has been known for millennia, it is still considered one of the most complex and least understood human organs. Imaging of the placenta is gaining attention due to its impact on fetal and maternal outcomes. MRI plays a vital role in evaluation of inconclusive cases by ultrasonography. It enables precise mapping of placental abnormalities for proper multidisciplinary planning and management. In this article we provide a comprehensive in-depth review of the role of antenatal MR in evaluating "The Placenta." We will describe the protocols and techniques used for MRI of the placenta, review anatomy of the placenta, describe MRI features of major placental abnormalities including those related to position, depth of implantation, hemorrhage, gestational trophoblastic neoplasia, and retained products of conception and discuss the added value of MRI in the management and preoperative planning of such abnormalities. Level of Evidence: 3 Technical Efficacy Stage: 5 J. Magn. Reson. Imaging 2019;50:1702-1717.

Morphological evaluation of cervix using MRI at 32 to 36 weeks of gestation: Findings for predicting invasive placenta previa

This study is to investigate the role of cervical morphology evaluated by magnetic resonance imaging (MRI) in predicting invasive placenta previa (IPP).Totally 105 cases of pregnant women underwent prenatal placental MRI at 32 to 36 weeks of gestation for suspected IPP were included in this study. Cervical morphology (cervical length and placental protrusion) was evaluated independently by 2 radiologists. The association between the cervical morphology and surgery findings was analyzed.Totally, 57 pregnant women were confirmed as IPP. For invasion degree, there were 17 cases with placenta percreta and 40 with accreta. For invasion topography, there were 27 cases with S1 invasion and 30 with S2 invasion. The sensitivity and specificity for the MRI sign of placental protrusion in evaluating cervical invasion of IPP were 100% and 100%, respectively. All the 7 IPP patents with cervical invasion received total hysterectomy and had severe blood loss (3500-6000 mL). The IPP patients with S2 invasion had shorter cervical length than those with S1 invasion (2.66 ± 0.66 cm vs 3.24 ± 0.64 cm, P <.001). However, cervical lengths did not correlate with the degree of invasion (placenta percreta vs placenta accreta: 2.82 ± 0.86 vs 2.99 ± 0.60, P = .21).Placental protrusion is a reliable MRI sign for cervical invasion of IPP, and cervical lengths correlate with the invasion topography.

Utility of diffusion-weighted MR imaging in the diagnosis of placenta accreta spectrum abnormality

PURPOSE

The aim of this study was to evaluate the utility of added DWI sequences as an adjunct to traditional MR imaging in the evaluation of abnormal placentation in patients with suspicion for placenta accreta spectrum abnormality or morbidly adherent placenta (MAP).

MATERIALS AND METHODS

The study was approved by local ethics committee. The subjects included pregnant women with prenatal MRI performed between July 2013 to July 2015. All imaging was performed on a Philips 1.5T MR scanner using pelvic phased-array coil. Only T2-weighted and diffusion-weighted imaging (DWI) series were compiled for review. Two randomized imaging sets were created: set 1 included T2-weighted series only (T2W); set 2 included T2W with DWI series together (T2W + DWI). Three radiologists, blinded to history and pathology, reviewed the imaging, with 2 weeks of time between the two image sets. Sensitivity, specificity, and overall accuracy for MAP were calculated and compared between T2W only and T2W + DWI reads. Associations between imaging findings and invasion on pathology were tested using the Chi-squared test. Confidence scores, inter-reader agreement, and systematic differences were documented.

RESULTS

A total of 17 pregnant women were included in the study. 8 cases were pathologically diagnosed with MAP. There were no significant differences in the diagnostic accuracy between T2W and T2W + DWI in the diagnosis of MAP in terms of overall accuracy (62.7% for T2W vs. 68.6% for T2W + DWI, p = 0.68), sensitivity (70.8% for T2W vs. 95.8% for T2W + DWI, p = 0.12), and specificity (55.6% for T2W vs. 44.4% for T2W + DWI, p = 0.49). There was no significant difference in the diagnostic confidence between the review of T2W images alone and the T2W + DWI review (mean 7.3 ± 1.8 for T2W vs. 7.5 ± 1.8 for T2W + DWI, p = 0.37).

CONCLUSION

With the current imaging technique, addition of DWI sequence to the traditional T2W images cannot be shown to significantly increase the accuracy or reader confidence for diagnosis of placenta accreta spectrum abnormality. However, DWI does improve identification of abnormalities in the placental-myometrial interface.

Endovascular Interventions for the Morbidly Adherent Placenta

Morbidly adherent placentas are a spectrum of abnormalities ranging from placental invasion of the myometrium to invasion past the myometrium and muscular layers into adjacent structures. This entity is becoming more prevalent recently with increased number of cesarean deliveries. Given the high risk of morbidity and mortality, this was traditionally treated with pre-term planned cesarean hysterectomy. However, recently, uterine preservation techniques have been implemented for those women wishing to preserve future fertility or their uterus. Early identification is crucial as studies have shown better outcomes for women treated at tertiary care facilities by a dedicated multidisciplinary team. Interventional radiologists are frequently included in the care of these patients as there are several different endovascular techniques which can be implemented to decrease morbidity in these patients both in conjunction with cesarean hysterectomy and in the setting of uterine preservation. This article will review the spectrum of morbidly adherent placentas, imaging, as well as the surgical and endovascular interventions implemented in the care of these complex patients.

Diagnostic accuracy of magnetic resonance imaging in detecting the severity of abnormal invasive placenta: a systematic review and meta-analysis

INTRODUCTION

Accurate prenatal diagnosis of abnormally invasive placenta (AIP) is fundamental because it significantly reduces maternal morbidities.

MATERIAL AND METHODS

Medline, Embase, CINAHL and the Cochrane databases were searched. The primary aim of the present review was to elucidate the diagnostic accuracy of prenatal magnetic resonance imaging (MRI) in recognizing the severity of AIP, defined as the depth and topography of invasion. The secondary aim was to ascertain the strength of association between each MRI sign and the depth of placental invasion and to test their individual predictive accuracy in detecting such invasion. Inclusion criteria were studies on women who had prenatal MRI for ultrasound suspicion or the presence of clinical risk factors for AIP. Estimates of sensitivity, specificity, positive and negative likelihood ratios and diagnostic odds ratio were calculated using the hierarchical summary receiver characteristics curve model, and individual data random-effect logistic regression was used to calculate OR.

RESULTS

Twenty studies (1080 pregnancies undergoing MRI mainly for the ultrasound suspicion of AIP) were included. MRI showed a sensitivity of 94.4% [95% confidence interval (CI) 15.8-99.9], 100% (95% CI 75.3-100) and 86.5% (95% CI 74.2-94.4) for detection of placenta accreta, increta and percreta, respectively; the corresponding values for specificity were 98.8% (95% CI 70.7-100), 97.3% (95% CI 93.3-99.3), 96.8% (95% CI 93.5-98.7). MRI identified 100% of cases with S1 and 100% of those with S2 invasion confirmed at surgery. Among the different MRI signs, intra-placental dark bands showed the best sensitivity for the detection of placenta accreta, increta and percreta; as well as abnormal intra-placental vascularity, uterine bulging was associated with a higher risk of increta and percreta, exophitic mass and bladder tenting with placenta percreta.

CONCLUSION

Prenatal MRI has an excellent diagnostic accuracy in identifying the depth and the topography of placental invasion. However, these findings come mainly from studies in which MRI was performed as a secondary imaging tool in women already screened for AIP on ultrasound and might not reflect its actual diagnostic performance in detecting the severity of these disorders.

Placental recess accompanied by a T2 dark band: a new finding for diagnosing placental invasion

PURPOSE

Our aim was to assess the usefulness of a new magnetic resonance imaging (MRI) finding, the placental recess, for diagnosing placental invasion.

METHODS

This retrospective study included 51 patients (mean age 34.1 years, range 26-43 years) with suspected placental invasion who underwent cesarean section. Preoperative MRI was performed using a 1.5-T unit and included axial, sagittal, and coronal T2-weighted imaging (T2WI) with half-Fourier fast spin-echo sequences. Overall, 9 patients showed placental invasion, and 42 did not. Placental recess was defined as a placental deformity with contraction of the placental surface and outer rim of the uterus accompanied by a T2 dark band. Two radiologists independently assessed the presence of the placental recess and conventional findings including uterine bulging, abnormal placental vascularity, placental heterogeneous intensity on T2-weighted imaging (T2WI), and the T2 dark band. Fisher's two-sided exact test was used to compare findings between patients with and without placental invasion. Interobserver reliability was assessed using the kappa statistic.

RESULTS

MRI features had interobserver reliability of >0.40. Placental recess yielded the highest kappa value (0.898). Significant differences were identified between patients with and without placental invasion regarding abnormal placental vascularity, placental heterogeneous intensity, a T2 dark band, and the placental recess on T2WI (p = 0.0282, 0.0003, 0.0003, <0.0001, respectively). The placental recess had sensitivity, specificity, positive and negative predictive values, and accuracy of 56, 100, 100, 91, and 92%, respectively.

CONCLUSION

The placental recess was useful for diagnosing placental invasion, with high interobserver variability and accuracy.

The gravid uterus: MR imaging and reporting of abnormal placentation

Appropriate placentation is critical to maternal and fetal outcomes. Abnormal placentation, including placenta previa and morbidly adherent placenta, is increasing in incidence and is associated with multiple risk factors including advanced maternal age and history of prior cesarean delivery. Magnetic resonance imaging (MRI) is increasingly used in assessing the type and extent of abnormal placentation, often leading to modifications in surgical approach. Here, we review the MRI features and appropriate reporting of placenta previa and the placenta accreta spectrum.

MRI of Placenta Accreta, Placenta Increta, and Placenta Percreta: Pearls and Pitfalls

OBJECTIVE

The purpose of this article is to provide a primer for radiologists performing MRI for suspected placenta accreta, illustrating normal and abnormal findings and diagnostic pitfalls. Appropriate examination indications and recommendations for optimizing image acquisition and interpretation are summarized.

CONCLUSION

MRI increases the accuracy of the workup of high-risk patients and aids in multidisciplinary delivery planning to improve maternal outcome. Reader accuracy and confidence require adherence to examination performance, image interpretation criteria, and awareness of common pitfalls.

Prenatal MR imaging diagnosis of placental invasion

PURPOSE

The aim of the study was to evaluate the characteristic imaging features and performance of prenatal magnetic resonance (MR) imaging in the diagnosis of placental invasion.

METHODS

This retrospective study was approved by our institutional review board and written informed consent was waived. Twenty-eight patients (age range 26-39 years; mean age, 33.8 ± 3.1 years) with suspected placental invasion underwent prenatal MR imaging, including 7 patients with placental invasion and 21 without. Two radiologists assessed the presence of seven previously described MR imaging findings associated with placental invasion. Sensitivity, specificity, positive and negative predictive values, and accuracy were calculated. The diagnostic performance was also determined by a receiver-operating-characteristic curve analysis.

RESULTS

Three MR imaging findings (uterine bulging, heterogeneous signal intensity in the placenta on T2-weighted images, and hypointense intraplacental bands on T2-weighted images) were significantly more common in patients with placental invasion than in those without (P = 0.020-0.023). The presence of at least two of these three imaging findings yielded a sensitivity, specificity, positive and negative predictive values, and accuracy of 100, 86, 67, 95, and 89%, respectively.

CONCLUSIONS

The presence of at least two of the three characteristic prenatal MR imaging findings strongly supports a diagnosis of placental invasion.

Evaluation of interobserver variability and diagnostic performance of developed MRI-based radiological scoring system for invasive placenta previa

PURPOSE

To evaluate the interobserver variability and diagnostic performance of a developed magnetic resonance imaging (MRI)-based scoring system for invasive placenta previa.

MATERIALS AND METHODS

Prenatal MR images of 70 women were retrospectively evaluated, 18 of whom were diagnosed with invasive placenta. The six MR features (dark band on T2 -weighted images, intraplacental abnormal vascularity, placental bulge, heterogeneous placenta, myometrial thinning, and placental protrusion sign) were scored on 5-point Likert scale separately, and the cumulative radiological score (CRS) was defined as the sum of each score. Two more experienced radiologists (readers A and B) and two less experienced residents (readers C and D) calculated the CRS. Interobserver variability was assessed by measuring the intraclass correlation coefficient. Diagnostic performance was evaluated by means of receiver operating characteristic (ROC) analysis.

RESULTS

Interobserver variability for CRS was excellent for the more experienced radiologists (0.85), and good for all readers (0.72) and the less experienced residents (0.66). The area under the ROC curve (Az) and accuracy (Acc) for CRS were significantly higher or equivalent to those of other MR features for all readers (Az and Acc for reader A; CRS, 0.92, 91.4%; intraplacental T2 dark band, 0.83, P = 0.009, 81.4%, P = 0.03; intraplacental abnormal vascularity, 0.9, P = 0.3, 90.0%, P = 1.00; placental bulge, 0.81, P = 0.0008, 80.0%, P = 0.02; heterogeneous placenta, 0.85, P = 0.11, 74.3%, P = 0.002; myometrial thinning, 0.84, P = 0.06, 60.0%, P < 0.0001; placental protrusion sign, 0.81, P = 0.01, 81.4%, P = 0.26).

CONCLUSION

This developed MRI-based scoring system demonstrated excellent or good interobserver variability, and good diagnostic performance for invasive placenta previa. J. Magn. Reson. Imaging 2016;44:573-583.

Prenatal identification of invasive placentation using magnetic resonance imaging: systematic review and meta-analysis

OBJECTIVE

To assess systematically the performance of prenatal magnetic resonance imaging (MRI) in diagnosing the presence, degree and topography of disorders of invasive placentation and to explore the role of the different MRI signs in predicting these disorders. The diagnostic accuracy of ultrasound and MRI in the detection of invasive placentation was also compared.

METHODS

MEDLINE, EMBASE, CINAHL and The Cochrane Library, including The Cochrane Database of Systematic Reviews, Database of Abstracts of Reviews of Effects and The Cochrane Central Register of Controlled Trials, were searched electronically utilizing combinations of the relevant medical subject heading terms, keywords and word variants for 'invasive placentation' and 'magnetic resonance imaging'. Only prospective studies reporting a diagnosis of invasive placentation at the time of MRI and retrospective studies in which the radiologist was blinded to the final results were included in the analysis. The MRI signs explored were: uterine bulging, heterogeneous signal intensity, dark intraplacental bands on T2 weighted sequences, focal interruption of the myometrium and tenting of the bladder. Summary estimates of sensitivity, specificity, positive and negative likelihood ratios (LR+, LR-) and diagnostic odds ratio (DOR) were based, depending on the number of studies, upon DerSimonian-Laird random-effect or hierarchical summary receiver-operating characteristics models.

RESULTS

A total of 18 studies involving 1010 pregnancies at risk for invasive placentation were included. The overall diagnostic accuracy of MRI in detecting the presence of invasive placentation was: sensitivity, 94.4% (95% CI, 86.0-97.9%); specificity, 84.0% (95% CI, 76.0-89.8%); LR+, 5.91 (95% CI, 3.73-9.39); LR-, 0.07 (95% CI, 0.02-0.18); DOR, 89.0 (95% CI, 22.8-348.1). MRI had a high predictive accuracy in assessing both the depth and topography of placental invasion. All five MRI signs showed good predictive accuracy in the diagnosis of disorders of invasive placentation. There was no difference in either the sensitivity (P = 0.24) or the specificity (P = 0.91) between ultrasound and MRI for the detection of invasive placentation.

CONCLUSIONS

Prenatal MRI is highly accurate in diagnosing disorders of invasive placentation. Ultrasound and MRI have comparable predictive accuracy. Large population-based studies are needed in order to assess whether ultrasound can predict the depth and topography of placental invasion as reliably as can MRI.

Imaging for acute pelvic pain in pregnancy

Acute pelvic pain in pregnancy presents diagnostic and therapeutic challenges. Standard imaging techniques need to be adapted to reduce harm to the foetus from X-rays because of their teratogenic and carcinogenic potential. Ultrasound remains the primary imaging investigation of the pregnant abdomen. Magnetic resonance imaging (MRI) has been shown to be useful in the diagnosis of gynaecological and obstetric problems during pregnancy and in the setting of acute abdomen during pregnancy. MRI overcomes some of the limitations of ultrasound, mainly the size of the gravid uterus. MRI poses theoretical risks to the foetus and care must be taken to minimise these with the avoidance of contrast agents. Teaching Points • Ultrasound and MRI are the preferred investigations for acute pelvic pain during pregnancy. • Ultrasound remains the primary imaging investigation because of availability and portability. • MRI helps differentiate causes of acute pelvic pain when ultrasound is inconclusive.

MR imaging of the placenta: what a radiologist should know

Imaging of the placenta can have a profound impact on patient management, owing to the morbidity and mortality associated with various placental conditions. Placental conditions affecting the mother and fetus include molar pregnancies, placental hematoma, abruption, previa, accreta, vasa previa, chorioangioma, and retained products of conception. Although uncommon, abnormalities of the placenta are important to recognize owing to the potential for maternal and fetal morbidity and mortality. Sonography remains the first imaging modality for evaluation of the placenta. Magnetic resonance (MR) imaging has many unique properties that make it well-suited for imaging of the placenta: the multi-planar capabilities, the improved tissue contrast that can be obtained using a variety of pulse sequences and parameters and the lack of ionizing radiation; MR imaging can be of added diagnostic value when further characterization is required. In this article, we review the appearances and the role of MRI in diagnosis and management of these conditions. We present our clinical perspective on diagnosing these challenging problems with MRI and review the imaging findings that can lead to a correct diagnosis.

[Placenta accreta: screening, management and complications]

Abnormal placental invasion can result in major obstetric haemorrhage during delivery. The most important risk factors are the following: previous caesarean delivery, placenta praevia maternal age over 35, smoking, previous myomectomy, dilatation and curettage. When placenta accreta is suspected on ultrasound, an RMI can complete the diagnostic. Therefore, patients must be managed, as far as possible, in a reference centre, by a trained medical team. Birth must be planned in order to decrease complications rate. Treatment can consist in radical management (caesarean-hysterectomy) or conservative management (preservation of both uterus and placenta). Conservative management allows patients to keep fertility but can also decrease blood loss during delivery. Side effects of this therapy are secondary haemorrhage, sepsis, long-term follow-up and vaginal loss. There are few studies describing fertility after conservative management, but it seems to be a secure treatment for future pregnancies. Embolization can be a very useful, already demonstrated, help when massive haemorrhage occurs. Management of placenta accreta is multidisciplinary and patients must be informed of all options. Treatment is decided regarding history of the patients, operative findings and peri-partum blood loss.

Feasibility of diffusion-weighted MRI for defining placental invasion

The purpose of this clinical note is to describe the feasibility of using diffusion-weighted imaging for diagnosing placental invasion with a case of placenta increta and six cases without it. Diffusion-weighted imaging (DWI) at a b-value of 1000 sec/mm(2) can clearly define the border between the placenta and myometrium because only the placenta shows very high signal intensity. The corresponding image at a b-value of 0 sec/mm(2) shows the myometrium with high signal intensity compared with the surrounding fat. Therefore, fusion of the two images can be used additionally to visualize thickness of the myometrium. As a result, DWI can be used to visualize the focal thinning of the myometrium caused by placenta increta, which has been difficult to diagnose on conventional magnetic resonance imaging sequences without contrast enhancement. However, the use of DWI for placental invasion should be determined following careful consideration of its risks and benefits, as fetus safety has not been established.

Evaluation of sonographic diagnostic criteria for placenta accreta

PURPOSE

To compare the diagnostic value of reported sonographic criteria for placenta accreta and to develop a composite score system for antenatal evaluation.

METHOD

Sixty-six women at risk for placenta accreta were examined for 9 cases of placenta accreta that were confirmed at delivery. The performance of previously reported gray-scale and Doppler sonographic criteria for the diagnosis of placenta accreta was analyzed individually. A composite score system was developed by combining selected sensitive or specific sonographic criteria, and its performance was evaluated.

RESULTS

The criteria of obliteration of retroplacental clear space, a myometrial thickness of <1 mm, presence of vessels bridging placenta and uterine margin, disruption of the placental-uterine wall interface, and vessels crossing the sites of interface disruption showed a statistically significant association with placenta accreta. The disruption of the placental-uterine wall interface and the presence of vessels crossing these sites were the only 2 individual criteria that could distinguish placenta accreta from non-accreta, which could also be achieved by our composite score system using a cutoff value of 40, with a sensitivity of 89% and specificity of 98%.

CONCLUSION

The diagnostic performance of the sonographic diagnostic criteria used in the diagnosis of placenta accreta varies, and a composite score system improves the overall accuracy.

MORBID ADHERENT PLACENTA: PREDICTION, DIAGNOSIS AND MANAGEMENT

Morbid adherent placenta (MAP), also known as placenta accreta, increta or percreta, is one of the main causes of maternal morbidity and mortality. Its incidence has noticeably increased in the last few decades, a fact directly related to the increase in caesarean sections. There is a close relation between iterative caesarean sections and MAP. This connection is of vital importance, since caesarean rates have risen worldwide, especially in the countries where there is the possibility of caesarean section on demand.

Placenta Accreta: A Review of Current Advances in Prenatal Diagnosis

Placenta accreta is a life-threatening obstetrical condition requiring a multidisciplinary approach. Despite identified obstetrical risk factors, the diagnosis is often made at the time of delivery. Recent advances in biology could allow a prenatal screening of placenta accreta with the identification of biological markers in maternal blood including cell-free fetal DNA, placental mRNA, and DNA microarray. These promising technologies can detect the presence of anomalies and should play a future role in developing a better understanding of placental invasion. Ultrasound imaging is popular due to its low cost and accessibility and widely used for the screening of placenta location and potential abnormal development. This exam is associated with high sensitivity and specificity for diagnosis of placenta accreta when specific defined criteria are used for the diagnosis. A placental MRI provides a morphological description, as well as recently demonstrated topographical information that optimizes diagnosis and surgical management. The screening of placenta accreta should be improved with the use of a combination of these diagnostic techniques and benefit high-risk populations with a reduction in morbidity.

Antenatal diagnosis of placenta accreta: a review

The incidence of placenta accreta should rise steadily over the next century as the frequency of Cesarean sections and advanced maternal age, both independent risk factors, increases. Patients who are at risk should be identified before an ultrasound examination and the characteristic findings searched for. In the first trimester, these include a low-lying sac that appears to be attached to the anterior wall of the uterus. As early as 16 weeks irregular vascular sinuses appear, which have turbulent flow within. The bladder wall may appear interrupted or have small bulges of the placenta into the bladder space. Absence of the normal echolucent space between the placenta and myometrium is not a reliable sign by itself, since this space may be absent in normal patients with an anterior placenta. Color Doppler will show that some of the placental sinuses traverse the uterine wall. Magnetic resonance imaging has not yet been shown to aid in the diagnosis, but in the future, with improvement of resolution and shortened sequences, it should be particularly useful in identifying the patients that have placenta percreta.