Efficient Ultrasound Image Analysis Models with Sonographer Gaze Assisted Distillation.

Recent automated medical image analysis methods have attained state-of-the-art performance but have relied on memory and compute-intensive deep learning models. Reducing model size without significant loss in performance metrics is crucial for time and memory-efficient automated image-based decision-making. Traditional deep learning based image analysis only uses expert knowledge in the form of manual annotations. Recently, there has been interest in introducing other forms of expert knowledge into deep learning architecture design. This is the approach considered in the paper where we propose to combine ultrasound video with point-of-gaze tracked for expert sonographers as they scan to train memory-efficient ultrasound image analysis models. Specifically we develop teacher-student knowledge transfer models for the exemplar task of frame classification for the fetal abdomen, head, and femur. The best performing memory-efficient models attain performance within 5% of conventional models that are 1000× larger in size

Multimodal Convolutional Neural Networks to Detect Fetal Compromise During Labor and Delivery

The gold standard to assess whether a baby is at risk of oxygen deprivation during childbirth, is monitoring continuously the fetal heart rate with cardiotocography (CTG). The aim is to identify babies that could benefit from an emergency operative delivery (e.g., Cesarean section), in order to prevent death or permanent brain injury. The long, dynamic and complex CTG patterns are poorly understood and known to have high false positive and false negative rates. Visual interpretation by clinicians is challenging and reliable accurate fetal monitoring in labor remains an enormous unmet medical need. In this work, we applied deep learning methods to achieve data-driven automated CTG evaluation. Multimodal Convolutional Neural Network (MCNN) and Stacked MCNN models were used to analyze the largest available database of routinely collected CTG and linked clinical data (comprising more than 35000 births). We also assessed in detail the impact of the signal quality on the MCNN performance. On a large hold-out testing set from Oxford (n= 4429 births), MCNN improved the prediction of cord acidemia at birth when compared with Clinical Practice and previous computerized approaches. On two external datasets, MCNN demonstrated better performance compared to current feature extraction-based methods. Our group is the first to apply deep learning for the analysis of CTG. We conclude that MCNN hold potential for the prediction of cord acidemia at birth and further work is warranted. Despite the advances, our deep learning models are currently not suitable for the detection of severe fetal injury in the absence of cord acidemia - a heterogeneous, small, and poorly understood group. We suggest that the most promising way forward are hybrid approaches to CTG interpretation in labor, in which different diagnostic models can estimate the risk for different types of fetal compromise, incorporating clinical knowledge with data-driven analyses

Small for Gestational Age Babies After 37 Weeks: An Impact Study of a Risk Stratification Protocol.

OBJECTIVES: Although no clear evidence exists, many international guidelines advocate early term delivery of small for gestational age (SGA) fetuses. The aim of this study was to determine whether a protocol that included monitoring SGA fetuses beyond 37 weeks affected perinatal and maternal outcomes. METHODS: The impact of the introduction in 2014 of a protocol for management of SGA, which included risk stratification with surveillance and expectant management after 37 weeks for lower risk babies (Group 2), was compared with the previous strategy, which recommended delivery at around 37 weeks (Group 1). Data from all referred SGA babies over a 39 month period were analyzed. RESULTS: In group 1 there were 138 SGA babies; in group 2 there were 143. The mean gestation at delivery was 37 + 4 and 38 + 2 weeks respectively (p = 0.04). The incidence of neonatal composite adverse outcomes was lower in Group 2 (9% v 22% v; p < 0.01) as was neonatal NNU admission (13% v 42%; p < 0.01). Induction of labour and caesarean section rates were lower, and vaginal delivery (83% v 60%; p < 0.01) was higher in group 2. Most of the differences were due to delayed delivery of SGA babies that were stratified as low risk. CONCLUSIONS: This study suggests that protocol-based management of SGA babies may improve outcomes and that identification of moderate SGA should not alone prompt delivery. Larger numbers are required to assess any impact on perinatal mortality

International standards for early fetal size and pregnancy dating based on ultrasound measurement of crown-rump length in the first trimester of pregnancy.

OBJECTIVES: There are no international standards for relating fetal crown-rump length (CRL) to gestational age (GA), and most existing charts have considerable methodological limitations. The INTERGROWTH-21(st) Project aimed to produce the first international standards for early fetal size and ultrasound dating of pregnancy based on CRL measurement. METHODS: Urban areas in eight geographically diverse countries that met strict eligibility criteria were selected for the prospective, population-based recruitment, between 9 + 0 and 13 + 6 weeks' gestation, of healthy well-nourished women with singleton pregnancies at low risk of fetal growth impairment. GA was calculated on the basis of a certain last menstrual period, regular menstrual cycle and lack of hormonal medication or breastfeeding in the preceding 2 months. CRL was measured using strict protocols and quality-control measures. All women were followed up throughout pregnancy until delivery and hospital discharge. Cases of neonatal and fetal death, severe pregnancy complications and congenital abnormalities were excluded from the study. RESULTS: A total of 4607 women were enrolled in the Fetal Growth Longitudinal Study, one of the three main components of the INTERGROWTH-21(st) Project, of whom 4321 had a live singleton birth in the absence of severe maternal conditions or congenital abnormalities detected by ultrasound or at birth. The CRL was measured in 56 women at < 9 + 0 weeks' gestation; these were excluded, resulting in 4265 women who contributed data to the final analysis. The mean CRL and SD increased with GA almost linearly, and their relationship to GA is given by the following two equations (in which GA is in days and CRL in mm): mean CRL = -50.6562 + (0.815118 × GA) + (0.00535302 × GA(2) ); and SD of CRL = -2.21626 + (0.0984894 × GA). GA estimation is carried out according to the two equations: GA = 40.9041 + (3.21585 × CRL(0.5) ) + (0.348956 × CRL); and SD of GA = 2.39102 + (0.0193474 × CRL). CONCLUSIONS: We have produced international prescriptive standards for early fetal linear size and ultrasound dating of pregnancy in the first trimester that can be used throughout the world

Reduction in twin stillbirth following implementation of NICE guidance.

OBJECTIVE: There has been an unprecedented fall in the rate of stillbirth in twin pregnancy in the UK. It is contested whether implementation of the National Institute for Health and Care Excellence (NICE) guidance on the antenatal management of uncomplicated twin pregnancies has contributed to this change. The aim of this study was to investigate whether the implementation of NICE guidance was associated with a reduction in the rate of stillbirth in twin pregnancies delivered in a large UK hospital. METHODS: This was a retrospective cohort study including all twin pregnancies delivered at St George's Hospital, London, UK, between 2000 and 2018. Data were analyzed according to two time periods: before implementation of the NICE guidance on twins (before June 2013; pre-NICE) and after its implementation (after June 2013; post-NICE). The exclusion criteria were higher-order multiple gestations, pregnancies of unknown chorionicity, pregnancies complicated by miscarriage, those that underwent termination and those diagnosed with vanishing twin. The main outcome was stillbirth. Other outcomes included neonatal death (NND), admission to the neonatal intensive care unit (NICU) and emergency Cesarean section. We planned a priori a sensitivity analysis according to chorionicity. The chi-square test and Mann-Whitney U-test were used to compare outcomes between the study groups. RESULTS: We included in the analysis 1666 twin pregnancies (3332 fetuses), of which 1114 pregnancies (2228 fetuses) were delivered before and 552 pregnancies (1104 fetuses) after June 2013. Of those, 1299 were dichorionic and 354 were monochorionic diamniotic. The incidence of stillbirth was significantly lower in the post-NICE than in the pre-NICE group (3.6 per 1000 births vs 13.5 per 1000 births; P = 0.008). The reduction in stillbirth rate was from 8.5 to 3.6 per 1000 births (P = 0.161) in dichorionic and from 33.6 to 3.8 per 1000 births (P = 0.011) in monochorionic diamniotic twin pregnancies. There was no significant difference in the rates of NND (P = 0.625), NICU admission (P = 0.506) or emergency Cesarean section (P = 0.820) between the two groups. The median gestational age at delivery was significantly lower in the post-NICE than in the pre-NICE group (median 36.3 vs 36.9 weeks; P  70% in the stillbirth rate in twin pregnancies was noted after implementation of the NICE guidance. This reduction was statistically significant in monochorionic, but not dichorionic, twin pregnancies. The improvement in twin pregnancy outcome was achieved without a concomitant increase in NND, admission to the NICU or emergency Cesarean section. © 2020 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of the International Society of Ultrasound in Obstetrics and Gynecology

Lower uterine segment placental thickness in women with abnormally invasive placenta.

Introduction Ultrasound signs of abnormal placental invasion are subjective in nature. We tested the hypothesis that placental thickness in the lower uterine segment is increased when there is abnormally invasive placenta (AIP) in women with a low‐lying placenta. Material and methods Retrospective analysis of data of placental thickness in women with ultrasound evidence of major placenta previa or a low‐lying anterior placenta was done. The diagnosis of AIP was confirmed both intraoperatively and on histopathology for those managed by partial myometrial excision with uterine conservation or by hysterectomy. Results In all, 131 records were available for analysis after exclusion of 33 cases due to unsuitable images and eight cases without pregnancy outcomes. The diagnosis of AIP was confirmed in 28 (21.4%) of the 131 cases. The lower segment placental thickness was significantly higher in women with AIP (median = 50.3 mm, IQR: 42.7‐64.3) than in those with normal placentation (median = 30.9 mm, IQR: 22.9‐42.2, P < 0.001). Logistic regression analysis showed that previous cesarean section and placental thickness on ultrasound were independent predictors for AIP. Conclusions Lower uterine segment placental thickness is increased in women with AIP compared with those with noninvasive placentation. This association constitutes a pragmatic objective sign and may be of clinical value in improving prenatal detection of AIP in women with placental implantation in the lower uterine segment. Prospective studies are necessary to ascertain lower segment placental thickness as a predictor for AIP

Plane Localization in 3-D Fetal Neurosonography for Longitudinal Analysis of the Developing Brain.

The parasagittal (PS) plane is a 2-D diagnostic plane used routinely in cranial ultrasonography of the neonatal brain. This paper develops a novel approach to find the PS plane in a 3-D fetal ultrasound scan to allow image-based biomarkers to be tracked from prebirth through the first weeks of postbirth life. We propose an accurate plane-finding solution based on regression forests (RF). The method initially localizes the fetal brain and its midline automatically. The midline on several axial slices is used to detect the midsagittal plane, which is used as a constraint in the proposed RF framework to detect the PS plane. The proposed learning algorithm guides the RF learning method in a novel way by: 1) using informative voxels and voxel informative strength as a weighting within the training stage objective function, and 2) introducing regularization of the RF by proposing a geometrical feature within the training stage. Results on clinical data indicate that the new automated method is more reproducible than manual plane finding obtained by two clinicians

Diagnostic accuracy of midtrimester antenatal ultrasound for multicystic dysplastic kidneys

OBJECTIVES: To establish the diagnostic accuracy of obstetric ultrasound at a tertiary fetal medicine centre in the prenatal detection of unilateral and bilateral MCDK in fetuses where this condition was suspected; and to undertake a systematic review of the literature on this topic. METHODS: Retrospective observational study of all cases with an antenatal diagnosis of either unilateral or bilateral MCDK referred to a regional tertiary fetal medicine unit between 1997 and 2015. Postnatal diagnosis was confirmed by postnatal ultrasound reports or postmortem examination. The accuracy for prenatal ultrasound in the diagnosis of MCDK was calculated. We also performed a review of the literature using a systematic search strategy, regarding the prenatal diagnosis and diagnostic accuracy of MCDK. RESULTS: We included 144 women in the analysis; 37 (25.7%) opted for pregnancy termination (due to unilateral MCDK with additional abnormalities, bilateral suspected MCDK or severe obstructive uropathy). In 126 women all pre- and postnatal data were available, including 104 livebirths; 19 who opted for TOP and where PM was available; and 3 that had an intrauterine fetal death. Two infants died shortly after birth, (due to known bilateral MCDK and known cranial vault defect). The overall number of postnatally confirmed MCDK was 100: of these 98 were diagnosed prenatally (true positive), while 2 were thought to be hydronephrosis prenatally (false negative) and the diagnosis of MCDK was made after birth. In 9 cases the initial antenatal diagnosis of suspected MCDK was revised, either later in pregnancy (n = 2) or postnatally (n = 7). The overall diagnostic accuracy of MCDK reported in the existing literature was found to range from 53.3 to 100%. MCDK was isolated in the majority of cases, while in 29% of cases was found to be associated with other renal and extra-renal fetal abnormalities. CONCLUSIONS: Our study suggests that the diagnostic accuracy for the use of antenatal ultrasound to detect postnatal MCDK was about 91% and can therefore be used to guide antenatal counselling. However, prenatal or postnatal revision of the diagnosis occurs in about 7% of cases and parents should be counselled appropriately

Ultrasound methodology used to construct the fetal growth standards in the INTERGROWTH-21st Project

A unified protocol is essential to ensure that fetal ultrasound measurements taken in multicentre research studies are accurate and reproducible. This paper describes the methodology used to take two-dimensional, ultrasound measurements in the longitudinal, fetal growth component of the INTERGROWTH-21st Project. These standardised methods should minimise the systematic errors associated with pooling data from different study sites. They represent a model for carrying out similar research studies in the future