MRI of normal and pathological fetal lung development

Congenital Chest Lesions and Interventions

Anomalies of the fetal chest require advanced imaging with ultrasound and MR imaging as well as expertise on the part of the interpreting pediatric radiologist. Congenital diaphragmatic hernia and congenital lung malformation are the most frequently seen, and in both conditions, the radiologist should provide both detailed anatomic description and measurement data for prognostication. This article provides a detailed approach to imaging the anatomy, in-depth explanation of available measurements and prognostic value, and keys to identifying candidates for fetal intervention. Less common congenital lung tumors and mediastinal and chest wall masses are also reviewed.

Functional MRI assessment of the lungs in fetuses that deliver very Preterm: An MRI pilot study

OBJECTIVES

To compare mean pulmonary T2* values and pulmonary volumes in fetuses that subsequently spontaneously delivered before 32 weeks with a control cohort with comparable gestational ages and to assess the value of mean pulmonary T2* as a predictor of preterm birth < 32 weeks' gestation.

METHODS

MRI datasets scanned at similar gestational ages were selected from fetuses who spontaneously delivered < 32 weeks of gestation and a control group who subsequently delivered at term with no complications. All women underwent a fetal MRI on a 3 T MRI imaging system. Sequences included T2-weighted single shot fast spin echo and T2* sequences, using gradient echo single shot echo planar sequencing of the fetal thorax. Motion correction was performed using slice-to-volume reconstruction and T2* maps generated using in-house pipelines. Lungs were manually segmented and volumes and mean T2* values calculated for both lungs combined and left and right lung separately. Linear regression was used to compare values between the preterm and control cohorts accounting for the effects of gestation. Receiver operating curves were generated for mean T2* values and pulmonary volume as predictors of preterm birth < 32 weeks' gestation.

RESULTS

Datasets from twenty-eight preterm and 74 control fetuses were suitable for analysis. MRI images were taken at similar fetal gestational ages (preterm cohort (mean ± SD) 24.9 ± 3.3 and control cohort (mean ± SD) 26.5 ± 3.0). Mean gestational age at delivery was 26.4 ± 3.3 for the preterm group and 39.9 ± 1.3 for the control group. Mean pulmonary T2* values remained constant with increasing gestational age while pulmonary volumes increased. Both T2* and pulmonary volumes were lower in the preterm group than in the control group for all parameters (both combined, left, and right lung (p < 0.001 in all cases). Adjusted for gestational age, pulmonary volumes and mean T2* values were good predictors of premature delivery in fetuses < 32 weeks (area under the curve of 0.828 and 0.754 respectively).

CONCLUSION

These findings indicate that mean pulmonary T2* values and volumes were lower in fetuses that subsequently delivered very preterm. This may suggest potentially altered oxygenation and indicate that pulmonary morbidity associated with prematurity has an antenatal antecedent. Future work should explore these results correlating antenatal findings with long term pulmonary outcomes.

The upper airway parameters: the potential diagnostic clues for congenital intrathoracic lesions

BACKGROUND

The diagnosis of congenital intrathoracic lesions still has limitations. The airway development was influenced by intrathoracic factors. Whether the diagnostic value of the upper airway parameters in congenital intrathoracic lesions has not been confirmed.

OBJECTIVES

We aimed to compare fetal upper airway parameters between normal fetuses and fetuses with intrathoracic lesions, and we tried to verify its diagnostic value in intrathoracic lesions.

METHODS

This was an observational case-control study. In the control group, 77 women were screened at 20-24 weeks' gestational age, 23 were screened at 24-28 weeks' gestational age, and 27 were screened at 28-34 weeks' gestational age. In the case group, 41 cases were enrolled (6 cases of intrathoracic bronchopulmonary sequestration, 22 of congenital pulmonary airway malformations, and 13 of congenital diaphragmatic hernia). Fetal upper airway parameters (tracheal width, the narrowest lumen width, and width of the subglottic cavity and laryngeal vestibule) were measured using ultrasound equipment. The correlations between fetal upper airway parameters and gestational age, and the differences in fetal upper airway parameters between cases and controls, were analyzed. The standardized airway paraments were acquired, and their potential diagnostic value for congenital intrathoracic lesions were analyzed.

RESULTS

The fetal upper airway parameters of both groups were positively correlated with the gestational age: The control group, tracheal width (R² = 0.569, p < 0.001), narrowest lumen width (R² = 0.429, p < 0.001), subglottic cavity width (R² = 0.551, p < 0.001), laryngeal vestibule width (R² = 0.349, p < 0.001). The case group (tracheal width R² = 0.474, p < 0.001) narrowest lumen width (R² = 0.425, p < 0.001), subglottic cavity width (R² = 0.623, p < 0.001), laryngeal vestibule width (R² = 0.347, p < 0.001). Fetal upper airway parameters of the cases group were smaller than those of the controls group. The tracheal width in fetuses with congenital diaphragmatic hernia was the smallest among the other case groups studied. The standardized tracheal width has the best diagnostic value for congenital intrathoracic lesions in the standardized airway paraments (the area under the ROC curve was 0.894), and has a high diagnostic value for congenital pulmonary airway malformations and congenital diaphragmatic hernia (the area under the ROC curve was 0.911 and 0.992, respectively).

CONCLUSION

Fetal upper airway parameters differ between normal fetuses and fetuses with intrathoracic lesions, and might offer potential diagnostic clues for congenital intrathoracic lesions.

Reproducibility of 2D versus 3D radiomics for quantitative assessment of fetal lung development: a retrospective fetal MRI study

PURPOSE

To investigate the reproducibility of radiomics features extracted from two-dimensional regions of interest (2D ROIs) versus whole lung (3D) ROIs in repeated in-vivo fetal magnetic resonance imaging (MRI) acquisitions.

METHODS

Thirty fetal MRI scans including two axial T2-weighted acquisitions of the lungs were analysed. 2D (lung at the level of the carina) and 3D (whole lung) ROIs were manually segmented using ITK-Snap. Ninety-five radiomics features were extracted from 2 and 3D ROIs in initial and repeat acquisitions using Pyradiomics. Radiomics feature intra-class correlation coefficients (ICC) were calculated between 2 and 3D ROIs in the initial acquisition, and between 2 and 3D ROIs in repeated acquisitions, respectively.

RESULTS

MRI data of 11 (36.7%) female and 19 (63.3%) male fetuses acquired at a median 25 + 0 gestational weeks plus days (GW) (interquartile range [IQR] 23 + 4 - 27 + 0 GW) were assessed. Median radiomics feature ICC between 2 and 3D ROIs in the initial MRI acquisition was 0.733 (IQR 0.313-0.814, range 0.018-0.970). ICCs between radiomics features extracted using 3D ROIs in initial and repeat acquisitions (median 0.908 [IQR 0.824-0.929, range 0.335-0.996]) were significantly higher compared to 2D ROIs (0.771 [0.699-0.835, 0.048-0.965]) (p < 0.001).

CONCLUSION

Fetal MRI radiomics features extracted from 3D whole lung segmentation masks showed significantly higher reproducibility across repeat acquisitions compared to 2D ROIs. Therefore, fetal MRI whole lung radiomics features are robust diagnostic and potentially prognostic tools in the image-based in-vivo quantitative assessment of lung development.

Expectant management of advanced abdominal pregnancies: Is it justifiable?

OBJECTIVE

To evaluate the outcome of a case series of women with advanced abdominal pregnancies (AAP) who underwent expectant management.

STUDY DESIGN

A retrospective study that utilized prospective data of 46 women who were admitted for expectant management at a tertiary hospital in Durban, South Africa. All data was analyzed descriptively and presented in percentages.

RESULTS

The average period of expectant management was 27 days; thirty-three (72 %) of the 46 women were discharged from the hospital with live babies. There were 11 (24 %) neonatal deaths and two cases of stillbirths. There were no maternal deaths and morbidity was minimal.

CONCLUSION

When diagnosed after the 24th week of gestation, an option is expectant management which includes careful patient selection, prolonged hospitalization, and close antenatal fetal and maternal surveillance to achieve fetal viability. Management by experienced clinicians and a multidisciplinary team in a tertiary institution is recommended. Informed consent needs to take into consideration the risks with interventional laparotomy, social separation from family and friends, and the guarded perinatal outcome.

Clinical Analysis of Fetal Lung Development Index and Pregnancy Outcome in Pregnant Women with Gestational Diabetes Mellitus with Satisfactory Blood Glucose Control

Objective

To explore the regularity of fetal lung development of pregnant women with gestational diabetes mellitus (GDM) with satisfactory blood glucose control and the clinical analysis with pregnancy outcome.

Methods

120 GDM pregnant women with satisfactory blood glucose control (GDM group) and 200 normal pregnant women undergoing prenatal examination (Control group) from 31 to 38 ^{+ 6} weeks of gestation were included. The two groups of pregnant women were divided into 8 time periods according to the gestational age, respectively. The parameters of Doppler flow velocity curve of fetal main pulmonary artery, diameter lines of fetal lung development, mode of delivery, neonatal weight, neonatal asphyxia, neonatal respiratory distress syndrome (NRDS), and neonatal pneumonia were, respectively, compared and analyzed between the two groups.

Results

Acceleration time (AT) and AT/ejection time (AT/ET) were positively correlated with gestational age, and AT/ET showed stronger correlation than AT, while no significant difference in AT and AT/ET between the two groups (P > 0.05). There was a positive correlation between the diameter of fetal lung development and gestational age, but there was no significant difference between the two groups (P > 0.05). In addition, there was no significant difference between the two groups in fetal delivery mode, neonatal weight, neonatal asphyxia, NRDS, and neonatal pneumonia (P > 0.05).

Conclusion

AT/ET may be a potential index to evaluate fetal lung maturity. There was no difference in fetal lung development and neonatal birth outcome between pregnant women with satisfactory GDM blood glucose control and the normal pregnant women. The pregnancy of GDM pregnant women lasts until the end of 37∼38 weeks, and the neonatal incidence rate is decreased. The key is to manipulate the blood glucose in the normal range.

Fetal Thoracic Circumference and Lung Volume and Their Relation to Fetal Size and Pulmonary Artery Blood Flow

OBJECTIVE

Research on early origins of lung disease suggests the need for studying the relationships of thoracic and lung size with fetal size and pulmonary circulation. The primary aim of this study is therefore to explore the associations between fetal thoracic circumference, lung volume, and fetal size. We also aim to assess if lung volume and thoracic circumference are associated with fetal pulmonary artery blood flow velocity measures.

METHODS

Cross-sectional assessment of singleton pregnancies from the general population (n = 447) at 30 gestational weeks (GW) was performed using ultrasound measurement of fetal thoracic circumference, lung volume, head and abdominal circumference, and femur length. We obtained Doppler blood flow velocity measures from the proximal branches of the fetal pulmonary artery. Associations between variables were studied using Pearson's correlation and multiple linear regression analyses.

RESULTS

Both thoracic circumference and lung volume correlated with fetal size measures, ranging from r = 0.64 between thoracic circumference and abdominal circumference, to r = 0.28 between lung volume and femur length. Adjustment for gestational age, maternal nicotine use, pre-pregnancy body mass index, and fetal sex marginally influenced the associations with abdominal circumference. The correlations of thoracic circumference and lung volume with pulmonary artery blood flow velocity measures were weak (r ≤ 0.17).

CONCLUSION

We found moderate to low correlation between thoracic circumference, lung volume, and fetal size at 30 GW. The closest relationship was with the abdominal circumference. We found low correlations of thoracic circumference and lung volume with pulmonary artery blood flow velocity measures.

MRI in Pregnancy and Precision Medicine: A Review from Literature

Magnetic resonance imaging (MRI) offers excellent spatial and contrast resolution for evaluating a wide variety of pathologies, without exposing patients to ionizing radiations. Additionally, MRI offers reproducible diagnostic imaging results that are not operator-dependent, a major advantage over ultrasound. MRI is commonly used in pregnant women to evaluate, most frequently, acute abdominal and pelvic pain or placental abnormalities, as well as neurological or fetal abnormalities, infections, or neoplasms. However, to date, our knowledge about MRI safety during pregnancy, especially about the administration of gadolinium-based contrast agents, which are able to cross the placental barrier, is still limited, raising concerns about possible negative effects on both the mother and the health of the fetus. Contrast agents that are unable to cross the placenta in a way that is safe for the fetus are desirable. In recent years, some preclinical studies, carried out in rodent models, have evaluated the role of long circulating liposomal nanoparticle-based blood-pool gadolinium contrast agents that do not penetrate the placental barrier due to their size and therefore do not expose the fetus to the contrast agent during pregnancy, preserving it from any hypothetical risks. Hence, we performed a literature review focusing on contrast and non-contrast MRI use during pregnancy.

Comparison of fetal lung maturation in fetuses with intrauterine growth restriction with control group, using lung volume, lung/liver and lung/muscle signal intensity and apparent diffusion coefficient ratios on different magnetic resonance imaging sequences

PURPOSE

To compare lung volume, lung apparent diffusion coefficient (ADC) and signal intensity ratio (SIR) on different magnetic resonance imaging (MRI) sequences between intrauterine growth restriction (IUGR) fetuses and the control group.

MATERIALS AND METHODS

49 IUGR and 58 non-IUGR fetuses were imaged using 3 Tesla MRI units. Total lung volume (TLV), lung/liver SIR (LLSIR) and lung/muscle SIR (LMSIR) in T1 and T2-weighted sequences and lung/liver ADC ratio (LLADCR) and lung/muscle ADC ratio (LMADCR) were assessed.

RESULTS

LLSIR and LMSIR were significantly higher in the T1-weighted sequence (p-value: .03) and LLADCR and LMADCR were significantly lower on diffusion-weighted imaging (DWI) in IUGR fetuses compared to the control group (p-value: .01). There was no significant difference in SIRs in the T2-weighted sequence between the two groups. Although TLV was increased with gestational age in both groups, it was significantly lower in the IUGR group (mean: 82 ± 22.7 ml vs. 110.8 ± 18 ml, p-value: <.001).

CONCLUSION

The T1-weighted sequence and DWI seem to be better than the T2-weighted sequence for assessing the faint difference of lung maturity between groups. However, SIR differences were not as meaningful as TLV differences and this could be related to the complex maturation process in IUGR fetuses as the effect of higher endogenous corticosteroids.

Bilateral lung transplantation during pregnancy after ECMO for influenza-A caused ARDS

Pregnant women with influenza-A have an increased risk of developing acute respiratory distress syndrome (ARDS). Extracorporeal membrane oxygenation (ECMO) can be used as salvage therapy, with lung transplantation as a therapeutic option. However, successful bilateral lung transplantation during pregnancy has never been reported before. We herein report the case of a 34-year-old primipara, who was diagnosed with ARDS caused by influenza-A-induced pneumonia at early gestation. After considering all possible therapeutic options and being fully dependent on VV-ECMO support, she underwent bilateral lung transplantation. The transplantation with intraoperative central VA-ECMO support was successfully performed with good recovery after an initial primary graft dysfunction. The pregnancy was prolonged until 29⁺⁵  gestational weeks. The newborn exhibited growth retardation and was initially stabilized, but later died due to severe, hypoxic respiratory failure and pulmonary hypertension. In conclusion, lung transplantation is a possible salvage therapy for patients with severe lung failure following ARDS during pregnancy. However, it places the mother and unborn child at risk. A multi-professional approach is warranted to diagnose and treat complications at an early stage.

Emerging magnetic resonance imaging techniques in open spina bifida in utero

Magnetic resonance imaging (MRI) has become an essential diagnostic modality for congenital disorders of the central nervous system. Recent advancements have transformed foetal MRI into a clinically feasible tool, and in an effort to find predictors of clinical outcomes in spinal dysraphism, foetal MRI began to unveil its potential. The purpose of our review is to introduce MRI techniques to experts with diverse backgrounds, who are involved in the management of spina bifida. We introduce advanced foetal MRI postprocessing potentially improving the diagnostic work-up. Importantly, we discuss how postprocessing can lead to a more efficient utilisation of foetal or neonatal MRI data to depict relevant anatomical characteristics. We provide a critical perspective on how structural, diffusion and metabolic MRI are utilised in an endeavour to shed light on the correlates of impaired development. We found that the literature is consistent about the value of MRI in providing morphological cues about hydrocephalus development, hindbrain herniation or outcomes related to shunting and motor functioning. MRI techniques, such as foetal diffusion MRI or diffusion tractography, are still far from clinical use; however, postnatal studies using these methods revealed findings that may reflect early neural correlates of upstream neuronal damage in spinal dysraphism.

Fetal body MRI for fetal and perinatal management

Fetal magnetic resonance imaging (MRI) has become a valuable adjunct to ultrasound (US) in diagnosing fetal abnormalities. This review is intended to highlight the contribution of MRI in parental counselling and perinatal treatment. A state-of-the-art fetal MRI protocol with experts of maternal-fetal medicine present in the MRI suite allows emphasis on patient-centred care and maximises therapeutic options.

Fetal ultrasound and magnetic resonance imaging: a primer on how to interpret prenatal lung lesions

Fetal lung lesions include common lesions such as congenital pulmonary airway malformation (CPAM), bronchopulmonary sequestration (BPS) and combined CPAM-BPS hybrid lesions, as well as less common entities including congenital lobar emphysema/obstruction, bronchial atresia, bronchogenic cysts and rare malignant pulmonary lesions such as pleuropulmonary blastoma. Fetal lung lesions occur in approximately 1 in 15,000 live births and are thought to arise from a spectrum of abnormalities related to airway obstruction and malformation, with the lesion type depending on the timing of insult, level of bronchial tree involvement, and severity of obstruction. Lesions vary from small and asymptomatic to large and symptomatic with significant mass effect on surrounding structures. Accurate diagnosis and characterization of these anomalies is crucial for guiding patient counseling as well as perinatal and postnatal management. The goal of this review is to provide an overview of normal fetal lung appearance and imaging features of common and uncommon lesions on both ultrasound and MR imaging, and to discuss key aspects in reporting and evaluating the severity of these lesions.

Assessment of BOLD response in the fetal lung

OBJECTIVE

Assessment of lung development and maturity is of utmost importance in prenatal counseling. Blood oxygen level-dependent (BOLD) effect MRI was developed for functional evaluations of organs. To date, no data are available in fetal lungs and nothing is known about the existence of a BOLD effect in the lungs. The aim of our study was to evaluate if a BOLD response could be detected in fetal lungs.

MATERIALS AND METHODS

From January 2014 to December 2016, 38 healthy pregnant women were prospectively enrolled. After a routine scan on a 1.5-T MRI device (normoxic period), maternal hyperoxia was induced for 5 min before the BOLD sequence (hyperoxic period). R2* was evaluated by fitting average intensity of the signal, both for normoxic (norm) and hyperoxic (hyper) periods.

RESULTS

A significant BOLD response was observed after maternal hyperoxia in the lungs with a mean R2* decrease of 12.1 ± 2.5% (p < 0.001), in line with the placenta response with a mean R2* decrease of 19.2 ± 5.9% (p < 0.0001), confirming appropriate oxygen uptake. Conversely, no significant BOLD effect was observed for the brain nor the liver with a mean ∆R2* of 3.6 ± 3.1% (p = 0.64) and 2.8 ± 3.7% (p = 0.23).

CONCLUSION

This study shows for the first time in human that a BOLD response can be observed in the normal fetal lung despite its prenatal "non-functional status." If confirmed in congenital lung and chest malformations, this property could be used in addition to the lung volume for a better prediction of postnatal respiratory status.

KEY POINTS

• Blood oxygen level-dependent (BOLD) effect MRI was developed for functional evaluations of organs and could have interesting implications for the fetal organs. • Assessment of lung development is of utmost importance in prenatal counseling, but to date no data are available in fetal lungs. • BOLD response can be observed in the normal fetal lung opening the way to studies on fetus with pathological lungs.

Magnetic Resonance Imaging in Pregnancy with Intrauterine Growth Restriction: A Pilot Study

Objective

Intrauterine growth restriction (IUGR) is a major cause of late stillbirth, though not all compromised babies remain small or are considered growth restricted as pregnancy progresses. Fetal Magnetic Resonance Imaging (f-MRI) represents a second-line tool to study pregnancies with IUGR fetuses. The aim of our study was to evaluate the usefulness of f-MRI on predicting fetal growth and the offspring's perinatal respiratory outcome.

Design

All f-MRI performed between 2014 and 2016 in Siena were analysed. Pregnancies with IUGR (Study group (SG)) were recruited together with a control population (Control group (CG)), coupled for gestational age (GA) at the time of f-MRI (mean GA 31 wks). Neonatal information was collected. The f-MRI protocol consisted of T2w images. Six regions of interest (ROI) were placed as follows: 2 on the lung, 2 on the liver, and 2 on the amniotic fluid. The signal intensities (SI) of each ROI were measured. The SI lung to liver ratio (SI lung/liver) and SI lung to amniotic fluid ratio (SI lung/amniotic fluid) were obtained for each fetus. Each ratio was compared between SG and CG. Therefore, SG was divided into two subgroups: adequate and small for gestational age (AGA and SGA) newborns. All measurements were related to offspring's perinatal respiratory outcome.

Results

SI lung/liver was linearly related with GA at the time of f-MRI and with EFW. SI lung/amniotic fluid was significantly higher in SG than in CG (p = 0,014). In contrast, among SG, lower values of SI lung/amniotic fluid were found in the SGA compared to AGA (p = 0,036). The days of oxygen supply were higher in the SGA subgroup than in the AGA subgroup (p = 0,028).

Conclusions

SI lung/liver increases with fetal lung maturation and appears to be useful to estimate intrauterine fetal growth. SI lung/amniotic fluid seems to be a reliable predictive index to distinguish the IUGR fetuses that can recover their growth from those that were born SGA. f-MRI represents a promising frontier to predict IUGR fetus outcome, thus contributing to ameliorate the perinatal management.

As Long as the Breath Lasts: In Utero Exposure to Ramadan and the Occurrence of Wheezing in Adulthood

While prenatal exposure to Ramadan has been shown to be negatively associated with general physical and mental health, studies on specific organs remain scarce. In this study, we explored whether Ramadan exposure during pregnancy affects the occurrence of wheezing, a main symptom of obstructive airway disease. Using data from the Indonesian Family Life Survey collected between 1997 and 2008 (waves 2-4), we compared wheezing occurrence among adult Muslims who had been in utero during Ramadan with that in adult Muslims who had not been in utero during Ramadan. Wheezing prevalence was higher among adult Muslims who had been in utero during Ramadan, independent of the pregnancy phase in which the exposure to Ramadan occurred. Moreover, this association tended to increase with age, being strongest among those aged about 45 years or older. This is in line with fetal programming theory, suggesting that impacts of in utero exposures often manifest only after reproductive age. Particularly strong associations were detected for smokers. The respiratory system of prenatally exposed Muslims thus seems to perform worse in mitigating later ex utero harmful influences such as smoking. This study suggests that exposure to Ramadan during pregnancy may have lasting consequences for adult lung functionality.

Fetal Lung Volumes by MRI: Normal Weekly Values From 18 Through 38 Weeks' Gestation

OBJECTIVE

The purpose of this study is to establish normal total fetal lung volume reference ranges from 18 to 38 weeks' gestation at 1-week intervals.

MATERIALS AND METHODS

A retrospective analysis of 665 patients who underwent fetal MRI at two tertiary fetal centers from 2001 to 2013 was performed. Total fetal lung volume was measured in at least two planes, either manually or using a 3D workstation. The mean, median, SD, minimum, maximum, and lower and upper quartiles for total fetal lung volume were determined per gestational week. A t test was used to compare our values to previously reported values. A new formula to calculate total fetal lung volume derived from our data was created using a regression model. Comparisons between total fetal lung volume obtained by different imaging planes and manual versus semiautomatic calculation were also performed.

RESULTS

The mean normal total fetal lung volume showed a weekly increase from 18 through 35 weeks' gestation. Means were compared with the expected total fetal lung volume generated by the Rypens formula, showing statistically significant lower mean total fetal lung volume from week 19 to week 22 (p < 0.05). Comparison between our data-derived total fetal lung volume formula and the Rypens formula showed very similar values at every gestational age. No difference in total fetal lung volume was seen when comparing imaging planes or manual versus semiautomatic methods.

CONCLUSION

Measured mean total fetal lung volume values at 19-22 weeks are significantly lower than those predicted by the Rypens formula. Therefore, we propose preferential use of our values for prenatal counseling and delivery planning.

Magnetic resonance assessment of fetal lung maturity: comparison between signal intensity and volume measurement

PURPOSE

We evaluated the associations between gestational age (GA) and lung-to-liver signal intensity ratio (LLSIR) and fetal lung volume (FLV) using magnetic resonance imaging (MRI). Moreover, we evaluated the reproducibility of these measurements.

MATERIALS AND METHODS

LLSIR and FLV were measured using single-shot fast spin-echo MRI in 88 consecutive fetuses. The Spearman test was used to assess the relationships between (1) LLSIR and GA, and (2) FLV and GA in 81 fetuses without lung abnormalities. Intra- and inter-observer reliabilities were assessed using intra-class correlation coefficients (ICCs).

RESULTS

Overall, GA and LLSIR were significantly correlated (r = 0.62, p < 0.001). However, GA and LLSIR were only significantly correlated during the third trimester (before third trimester: r = 0.39, p = 0.08; during third trimester: r = 0.46, p < 0.001). Overall, GA and FLV were significantly correlated (r = 0.72, p < 0.001). FLV was significantly correlated with GA before (r = 0.86, p < 0.001) and during the third trimester (r = 0.47, p < 0.001). All ICCs were above 0.90.

CONCLUSIONS

LLSIR and FLV are useful for the assessment of fetal lung maturity and are highly reproducible. Before the third trimester, FLV is more suitable than LLSIR for the evaluation of fetal lung maturity.

Seventeen years of prenatal magnetic resonance imaging at the Institute of Mother and Child in Warsaw

Purpose

The purpose of this paper is to summarise and to present the experience of the main Polish centre for prenatal magnetic resonance imaging (MRI) and to discuss the place and role of MRI in antenatal diagnosis, management, and counselling.

Material and methods

Retrospective analysis of the examinations performed in the years 2001-2017.

Results

In total, 1221 medical records and/or image files were collected. The full documentation of ultrasonography and MRI referrals, reports, and images was not available in every case. During the first three years 98 pregnant women were examined (approximately 33 per year, one study per fortnight). After purchase of own MR scanner, the number of examinations grew constantly, reaching 208 in 2017, which means almost one per day, and the highest number was eight in one day. We examined 45 pairs of twins, including three pairs of conjoined twins.

Conclusions

MRI at our Institute is a practically used second-line foetal imaging tool, necessary to confirm, complete, or correct sonographic diagnoses, with important impact on clinical decisions concerning management of pregnancy and of the neonate, termination of pregnancy, choice of the time, place, and mode of delivery, and neonatal care, as well as on counselling. In experienced hands, MRI is to date the last and the best non-invasive method of diagnosis in utero. It is frequently requested by the interdisciplinary team for foetal diagnosis and therapy and routinely performed in everyday practice.

Postmortem Characteristics of Lung Hypoplasia at Diaphragmatic Hernia: MRI – Pathomorphological Comparisons

Purpose: the study of postmortem MRI possibilities for the diagnosis of lung hypoplasia in congenital diaphragmatic hernia.

Materials and methods. A comparison of the results of postmortem MRI study and data of pathoanatomical autopsy of 23 newborns was performed. In group I, the bodies of 10 deceased newborns with congenital diaphragmatic hernia without operative intervention were examined. In group II – the bodies of 7 newborns who died after surgery for congenital diaphragmatic hernia. Group III (control) included 6 bodies of newborns without diaphragmatic hernia and signs of lung hypoplasia. Before the autopsy, an MRI study was performed on a 3T Magnetom Verio device (Siemens, Germany) in standard T1 and T2 modes. The volumes of the lungs and chest cavity were calculated in the analysis of the tomograms data and their 3D reconstruction. The stage of the lung development and number of radial alveoli were identified at the microscopic study of histological preparations.

Results.As a result of the postmortem MRI study, it was established that the observations of group I are characterized by minimal lung volumes. The mean lung volume on the side of the diaphragmatic hernia was 4.1 times less than the contralateral lung (p < 0.01), and the mean values of the volume of both lungs were 4.6 times less than the corresponding values of the control group (p < 0.01) . The average value of the specific volume of the lungs in newborns who died as a result of congenital diaphragmatic hernia (group I) was 8.8%, which is 4.2 times less than the control group (p < 0.01) and was accompanied by histological signs of hypoplasia. The operation in Group II observations led to an increase in lung size. However, the specific volume of the lungs in this group remained by 18.6% less than the control group, and on histological specimens there were signs of lung hypoplasia.

Conclusion.The postmortem MRI of dead newborns allows for an objective quantification of lung volumes and verifies the presence of hypoplasia. This helps to clarify the pathogenesis and determine the immediate cause of death. Indices of specific lung volume relative to the chest cavity of less than 20% indicate lung hypoplasia as the immediate cause of death of the newborn.

Pulmonary hypoplasia

To survive the transition to extrauterine life, newborn infants must have lungs that provide an adequate surface area and volume to allow for gas exchange. The dynamic activities of fetal breathing movements and accumulation of lung luminal fluid are key to fetal lung development throughout the various phases of lung development and growth, first by branching morphogenesis, and later by septation. Because effective gas exchange is essential to survival, pulmonary hypoplasia is among the leading findings on autopsies of children dying in the newborn period. Management of infants born prematurely who had disrupted lung development, especially at the pre-glandular or canalicular periods, may be challenging, but limited success has been reported. Growing understanding of stem cell biology and mechanical development of the lung, and how to apply them clinically, may lead to new approaches that will lead to better outcomes for these patients.

Prenatal prediction of pulmonary hypoplasia

Pulmonary hypoplasia, although rare, is associated with significant neonatal morbidity and mortality. Conditions associated with pulmonary hypoplasia include those which limit normal thoracic capacity or movement, including skeletal dysplasias and abdominal wall defects; those with mass effect, including congenital diaphragmatic hernia and pleural effusions; and those with decreased amniotic fluid, including preterm, premature rupture of membranes, and genitourinary anomalies. The ability to predict severe pulmonary hypoplasia prenatally aids in family counseling, as well as obstetric and neonatal management. The objective of this review is to outline the imaging techniques that are widely used prenatally to assess pulmonary hypoplasia and to discuss the limitations of these methods.

Review of surgical and anesthetic management for esophageal atresia with tracheoesophageal fistula, unilateral pulmonary agenesis and dextrocardia

Association of unilateral severe pulmonary atresia or agenesis and esophageal atresia (EA) with or without tracheoesophageal fistula (TEF) and dextrocardia is a rare and highly lethal combination. We report a case of a full-term female infant who had EA with TEF, right lung agenesis, and dextrocardia. Repair of the fistula took place on day of life 3. We describe anesthetic and surgical concerns of this patient's case which are keys to a good operative outcome as well as follow-up for the patient.

Magnetic resonance imaging of fetal persistent left superior vena cava

This study aimed to evaluate the diagnostic accuracy of fetal magnetic resonance imaging (MRI) for persistent left superior vena cava (LSVC). Prenatal echocardiography (echo) and/or ultrasound (US) and MRI data for 49 fetuses with persistent LSVC, confirmed via postnatal diagnoses between January 2010 and October 2015, were retrospectively reviewed. All prenatal MRI was performed at 1.5 T. Imaging sequences included steady-state free-precession (SSFP), single-shot turbo spin echo (SSTSE), and other sequences. All 49 cases of fetal persistent LSVC were correctly diagnosed via MRI, but only 34 cases (69.4%) were correctly diagnosed via an initial US and/or echo before MRI. Of the 15 cases that were not correctly diagnosed via US and/or echo, 8 had congenital heart diseases (CHDs) and 7 were without CHDs; however, they were associated with extracardiac abnormalities or maternal obesity. Thirty-five cases were associated with other cardiovascular abnormalities; 8, with extracardiac abnormalities; and 6, with no associated condition. In 44 (89.8%) cases, the innominate veins were absent; the remaining cases had innominate veins. In 14.3% of patients (7 cases), the persistent LSVC drained directly into the atrium. Fetal MRI can detect persistent LSVC and play an adjunctive role along with US in the evaluation of persistent LSVC.

Human fetal lung morphometry at autopsy with new modeling to quantitate structural maturity

OBJECTIVES

To demonstrate a simplified morphometric procedure, including a new model for acinar structural maturity, applicable to autopsy fetal lung and present reference values for these parameters.

STUDY DESIGN

Cases with autopsy consent for research were studied. To simplify analysis only critical morphometric parameters were measured to allow calculation of gas-exchange surface area.

SUBJECT SELECTION

A total of 58 fetuses, 16-40 weeks were included. Subjects were rejected with any condition predisposing to pulmonary hypo/hyperplasia, significant maceration, or if lung weight/bodyweight or microscopy identified pulmonary hypoplasia or lung growth disorders.

METHODOLOGY

Lungs were inflation fixed, weights and volumes determined, sampled, then returned to the body. Volume densities (V_V ) of parenchyma/non-parenchyma and air-space/gas-exchange tissue, gas-exchange surface density (S_V ), and total surface area (SA) were determined. The number, mean radius, and septal thickness of modeled airspace-spheres were calculated. Equations were generated for each parameter function of gestation and bodyweight.

RESULTS

From 16 to 40-week weights and volumes increased as power functions from ∼4 g/mL to ∼90 g/mL. Parenchyma/non-parenchyma changed little-75:25 (16 weeks) to 71:29 (term). Parenchyma was 10% airspace:90% tissue early and 50:50 by term. Gas-exchange S_V increased from 175 to 450 cm² /cm³ and total SA increased from 0.059 to 4.793 m² . There were 3.31 × 10⁶ airspace-spheres, 12 µ radius, septal thickness 30 µ at 16 weeks, increasing to 56.92 × 10⁶ , 26 µ radius, septal thickness 13 µ by term.

CONCLUSIONS

Morphometry can feasibly be performed at autopsy, providing more informative quantitative data on lung structural development than current methods utilized. This reference data set compares well with published data.

Fetal imaging and therapy for CDH-Current status

In congenital diaphragmatic hernia (CDH), herniation of the abdominal organs into the fetal chest causes pulmonary hypoplasia and pulmonary hypertension, the main causes of neonatal mortality. As antenatal ultrasound screening improves, the risk of postnatal death can now be better predicted, allowing for the identification of fetuses that might most benefit from a prenatal intervention. Fetoscopic tracheal occlusion is being evaluated in a large international randomized controlled trial. We present the antenatal imaging approaches that can help identify fetuses that might benefit from antenatal therapy, and review the evolution of fetal surgery for CDH to date.

Fetal MRI at 3T-ready for routine use?

Fetal MR now plays an important role in the clinical work-up of pregnant females. It is performed mainly at 1.5 T. However, the desire to obtain a more precise fetal depiction or the fact that some institutions have access only to a 3.0 T scanner has resulted in a growing interest in performing fetal MR at 3.0 T. The aim of this article was to provide a reference for the use of 3.0 T MRI as a prenatal diagnostic method.

Special Considerations in Neonatal Mechanical Ventilation

Care of infants supported with mechanical ventilation is complex, time intensive, and requires constant vigilance by an expertly prepared health care team. Current evidence must guide nursing practice regarding ventilated neonates. This article highlights the importance of common language to establish a shared mental model and enhance clear communication among the interprofessional team. Knowledge regarding the underpinnings of an open lung strategy and the interplay between the pathophysiology and individual infant's response to a specific ventilator strategy is most likely to result in a positive clinical outcome.

Why do we need more data on MR volumetric measurements of the fetal lung?

Fetal lung hypoplasia is associated with a series of congenital anomalies, particularly the congenital diaphragmatic hernia. Evaluation of the severity of the lung hypoplasia is important for parental counseling, assessment of prognosis and planning of postnatal management. Although a large number of studies have been performed to measure fetal lung volumes in order to predict outcome, there are little data on fetuses younger than 24 weeks of gestation, the age when parental counseling is crucial if termination is considered. Few studies have evaluated prognosis of lung hypoplasia in fetuses with congenital chest anomalies other than congenital diaphragmatic hernia. We review the studies on measurements of the fetal lung volumes by MRI.

Foetal and infant growth patterns, airway resistance and school-age asthma

BACKGROUND AND OBJECTIVE

Preterm birth, low birth weight and rapid infant weight gain are associated with increased risks of asthma symptoms in childhood. The underlying mechanism may include persistently higher airway resistance (Rint). The aim of our study was to examine the associations of longitudinally measured foetal and infant growth characteristics with Rint and asthma outcomes in school-age children.

METHODS

This study was embedded in a population-based prospective cohort study in Rotterdam, The Netherlands. Foetal growth was estimated by ultrasound in the second and third trimesters. Infant growth was measured at birth, 3, 6 and 12 months. At age 6 years, Rint was measured, and information about wheezing and asthma was obtained by questionnaires. The number of subjects per analysis differed per available outcome (3954-5066 subjects).

RESULTS

Longitudinal growth analyses showed that school-age children with increased Rint had lower foetal length growth and weight gain, and lower infant length growth. Children with persistent wheezing until age 6 years and physician-diagnosed asthma had a higher Rint compared with children who never wheezed or without asthma (difference z-scores Rint: 0.58 (0.19, 0.97) and 0.55 (0.15, 0.95), respectively).

CONCLUSION

Rint in school-age children is influenced by foetal growth restriction and is associated with asthma outcomes. See article, page 574.

High-Resolution (1)H NMR Spectroscopy Discriminates Amniotic Fluid of Fetuses with Congenital Diaphragmatic Hernia from Healthy Controls

Lung hypoplasia in congenital diaphragmatic hernia (CDH) is a life-threatening birth defect. Severe cases can be offered tracheal occlusion to boost prenatal lung development, although defining those to benefit remains challenging. Metabonomics of (1)H NMR spectra collected from amniotic fluid (AF) can identify general changes in diseased versus healthy fetuses. AF embodies lung secretions and hence might contain pulmonary next to general markers of disease in CDH fetuses. AF from 81 healthy and 22 CDH fetuses was collected. NMR spectroscopy was performed at 400 MHz to compare AF from fetuses with CDH against controls. Several advanced feature extraction methods based on statistical tests that explore spectral variability, similarity, and dissimilarity were applied and compared. This resulted in the identification of 30 spectral regions, which accounted for 80% variability between CDH and controls. Combination with automated classification discriminates AF from CDH versus healthy fetuses with up to 92% accuracy. Within the identified spectral regions, isoleucine, leucine, valine, pyruvate, GABA, glutamate, glutamine, citrate, creatine, creatinine, taurine, and glucose were the most concentrated metabolites. As the metabolite pattern of AF changes with fetal development, we have excluded metabolites with a high age-related variability and repeated the analysis with 12 spectral regions, which has resulted in similar classification accuracy. From this analysis, it was possible to distinguish between AF from CDH fetuses versus healthy controls independent of gestational age.

Fast Volume Reconstruction From Motion Corrupted Stacks of 2D Slices

Capturing an enclosing volume of moving subjects and organs using fast individual image slice acquisition has shown promise in dealing with motion artefacts. Motion between slice acquisitions results in spatial inconsistencies that can be resolved by slice-to-volume reconstruction (SVR) methods to provide high quality 3D image data. Existing algorithms are, however, typically very slow, specialised to specific applications and rely on approximations, which impedes their potential clinical use. In this paper, we present a fast multi-GPU accelerated framework for slice-to-volume reconstruction. It is based on optimised 2D/3D registration, super-resolution with automatic outlier rejection and an additional (optional) intensity bias correction. We introduce a novel and fully automatic procedure for selecting the image stack with least motion to serve as an initial registration target. We evaluate the proposed method using artificial motion corrupted phantom data as well as clinical data, including tracked freehand ultrasound of the liver and fetal Magnetic Resonance Imaging. We achieve speed-up factors greater than 30 compared to a single CPU system and greater than 10 compared to currently available state-of-the-art multi-core CPU methods. We ensure high reconstruction accuracy by exact computation of the point-spread function for every input data point, which has not previously been possible due to computational limitations. Our framework and its implementation is scalable for available computational infrastructures and tests show a speed-up factor of 1.70 for each additional GPU. This paves the way for the online application of image based reconstruction methods during clinical examinations. The source code for the proposed approach is publicly available.

Quantitative Anatomy of the Growing Lungs in the Human Fetus

Using anatomical, digital, and statistical methods we examined the three-dimensional growth of the lungs in 67 human fetuses aged 16-25 weeks. The lung dimensions revealed no sex differences. The transverse and sagittal diameters and the base circumference were greater in the right lungs while the lengths of anterior and posterior margins and the lung height were greater in the left lungs. The best-fit curves for all the lung parameters were natural logarithmic models. The transverse-to-sagittal diameter ratio remained stable and averaged 0.56 ± 0.08 and 0.52 ± 0.08 for the right and left lungs, respectively. For the right and left lungs, the transverse diameter-to-height ratio significantly increased from 0.74 ± 0.09 to 0.92 ± 0.08 and from 0.56 ± 0.07 to 0.79 ± 0.09, respectively. The sagittal diameter-to-height ratio significantly increased from 1.41 ± 0.23 to 1.66 ± 0.18 in the right lung, and from 1.27 ± 0.17 to 1.48 ± 0.22 in the left lung. In the fetal lungs, their proportionate increase in transverse and sagittal diameters considerably accelerates with relation to the lung height. The lung dimensions in the fetus are relevant in the evaluation of the normative pulmonary growth and the diagnosis of pulmonary hypoplasia.

The Effects of Hemodynamic Alterations on Lung Volumes in Fetuses with Tetralogy of Fallot: An MRI Study

This study assessed whether the presence of tetralogy of Fallot (TOF) affects fetal lung development and whether these fetuses are at risk of pulmonary hypoplasia (PH). Furthermore, we investigated whether the degree of the concomitant pulmonary valve (PV) stenosis or a stenosis in the branch pulmonary arteries correlates with the fetal lung volume. Lung volumetry was performed in 16 fetuses with TOF who underwent MRI between gestational weeks 21 and 35 and in 22 controls. Fetal biometric data and the diameters of the PVs were evaluated by ultrasound. PV and branch pulmonary artery diameters were standardized (z-scores), and fetal lung volume/fetal body weight (FLV/FBW) ratios (ml/g) were calculated. The mean FLV/FBW ratio (0.031 ± 0.009 ml/g) in the TOF group was statistically significantly lower than in the control group (0.041 ± 0.009 ml/g; P = 0.003). None of the fetuses with TOF met the criterion for PH. FLV did not correlate with the degree of PV stenosis, but rather with the presence of a significant stenosis in at least one branch pulmonary artery. The presence of TOF moderately affects fetal lung growth, which is apparently not dependent on the degree of the PV stenosis. However, only an additional stenosis in at least one branch pulmonary artery was associated with a small FLV, but not with PH. Thus, reduced pulmonary blood flow may be offset by additional factors, such as the ability to establish a sufficient collateral system and to alter structural vascular size and, thus, pulmonary vascular resistance.

Perinatal Thoracic Mass Lesions: Pre- and Postnatal Imaging

Chest masses present a common problem in the perinatal period. Advances in prenatal ultrasound, supplemented by fetal magnetic resonance imaging, now allow early detection and detailed characterization of many thoracic lesions in utero. As such, in asymptomatic infants, assessment with postnatal computed tomography or magnetic resonance imaging can often be delayed for several months until the time at which surgery is being contemplated. Bronchopulmonary malformations comprise most of the thoracic masses encountered in clinical practice. However, a variety of other pathologies can mimic their appearances or produce similar effects such as hypoplasia of a lung or both lungs. Understanding of the key differentiating clinical and imaging features can assist in optimizing prognostication and timely management.

Determination of fetal lung maturity using magnetic resonance imaging signal intensity measurements

PURPOSE

The objective of this study was to determine if magnetic resonance signal intensity measurements can be used to predict gestational age and hence fetal lung maturity.

METHODS

This institutional review board-approved study was a retrospective review of 394 fetal magnetic resonance imaging cases from a single institution for the years 2001 to 2011. For each case, T1- and T2-weighted sequences were selected for data collection. A single reviewer obtained 10 regions of interest (when possible) from each scan (fetal lung, fetal liver, fetal muscle, fetal spleen, and maternal urine, for both T1- and T2-weighted sequences). The medical record was searched for relevant information including best estimate of gestational age, Apgar scores, karyotype, and fetal diagnosis. A variety of organ-to-organ ratios and direct organ signal intensity measurements were assessed for correlation with gestational age.

RESULTS

Three hundred thirty-five cases met inclusion criteria with gestational ages ranging from 17 to 39 weeks (mean, 28.6 weeks). A significant relationship between magnetic resonance signal intensity ratios and gestational age was demonstrated on the T2 lung-to-liver, T2 lung-to-spleen, T2 lung-to-muscle, T1 lung-to-liver, and T1 lung-to-spleen ratios (P < 0.05). T2 lung-to-liver and T2 lung-to-muscle demonstrated the strongest relationship with gestational age (best correlation r = 0.483, P < 0.001). T1 lung-to-liver and T1 lung-to-spleen demonstrated inverse relationships with gestational age (r = -0.174 [P = 0.03] and r = -0.236 [P = 0.02], respectively).

CONCLUSIONS

A significant correlation between multiple signal intensity ratios and gestational age is demonstrated. However, the large variances preclude a clinically useful relationship.

Fetal MRI: A Technical Update with Educational Aspirations

Fetal magnetic resonance imaging (MRI) examinations have become well-established procedures at many institutions and can serve as useful adjuncts to ultrasound (US) exams when diagnostic doubts remain after US. Due to fetal motion, however, fetal MRI exams are challenging and require the MR scanner to be used in a somewhat different mode than that employed for more routine clinical studies. Herein we review the techniques most commonly used, and those that are available, for fetal MRI with an emphasis on the physics of the techniques and how to deploy them to improve success rates for fetal MRI exams. By far the most common technique employed is single-shot T2-weighted imaging due to its excellent tissue contrast and relative immunity to fetal motion. Despite the significant challenges involved, however, many of the other techniques commonly employed in conventional neuro- and body MRI such as T1 and T2*-weighted imaging, diffusion and perfusion weighted imaging, as well as spectroscopic methods remain of interest for fetal MR applications. An effort to understand the strengths and limitations of these basic methods within the context of fetal MRI is made in order to optimize their use and facilitate implementation of technical improvements for the further development of fetal MR imaging, both in acquisition and post-processing strategies.

Prognostic usefulness of derived T2-weighted fetal magnetic resonance imaging measurements in congenital diaphragmatic hernia

OBJECTIVE

To determine the usefulness of various parameters based on T2-weighted fetal magnetic resonance (MR) imaging measurements of the uninvolved lung for the neonatal prognosis of congenital diaphragmatic hernia (CDH).

MATERIAL AND METHODS

We used ultrasonography and MR imaging to study 28 fetuses with CDH. We retrospectively analyzed a) on fetal ultrasonography, the observed-to-expected lung to head ratio (O/E LHR) and the position of the liver, and b) on fetal MR imaging, the lung-liver signal ratio (LLSR) and the lungcerebrospinal fluid ratio (L/CSF SR). To determine the prognostic value of these parameters, we compared them with the following postnatal parameters: survival, pulmonary hypertension, need for oxygen supplementation, and need for extracorporeal membrane oxygenation.

RESULTS

We found significant differences between O/E LHR and the need for postnatal extracorporeal membrane oxygenation (P=.033) and postnatal survival (P=.01). We also found significant differences in LLSR between fetuses that survived more than 45 days and those that died within 45 days (1.91 vs. 2.56; P=.039).

CONCLUSIONS

In fetuses with CDH, the LLSR correlates with postnatal survival and can potentially be used as a prognostic parameter in CDH.

Unilateral pulmonary agenesis: a report of four cases, two diagnosed antenatally and literature review

Pulmonary agenesis is a rare congenital malformation of lung development defined as complete absence of lung tissues, bronchi, and pulmonary vessels; it may be uni- or bilateral. The right-sided form carries the poorest prognosis due to severity of co-existent anomalies. Its diagnostic circumstances are variables: first reported cases were diagnosed at autopsy, but early postnatal as well as fortuitous discovery have been reported. In recent years, progress in obstetrical imaging has made antenatal diagnosis possible so that fetal ultrasound and MRI allow early diagnosis and refinement by permitting the elimination of differential diagnoses (diaphragmatic hernia, cystic adenomatoid malformation of the lung, giant lobar emphysema, and situs inversus). This anomaly is compatible with normal life provided co-existent malformations are thoroughly investigated and managed in a multidisciplinary setting. We report four cases of lung agenesis two of which were diagnosed antenatally at 23rd and 30th weeks of gestation respectively. Our aim is to describe the circumstances having led to diagnosis and report both follow-up and outcome of our patients.

Volumetric growth of the lungs in human fetuses: an anatomical, hydrostatic and statistical study

Purpose

The prenatal assessment of lung volume is becoming increasingly important in determining survival in both preterm infants and newborns affected by pulmonary hypoplasia. This study aimed to examine the lung volumes in the human fetus at varying gestational ages.

Materials and methods

Using anatomical, hydrostatic (water displacement according to Archimedes’ patent) and statistical methods (one-way ANOVA test for paired data and post-hoc Bonferroni test, Kolmogorov–Smirnov test, Levene’s test, Student’s t test, regression analysis), volumes of the right and left lungs were measured in 67 human fetuses of both sexes (35 males, 32 females) aged 16–25 weeks, derived from spontaneous abortions and stillbirths.

Results

No male–female differences concerning the right and left pulmonary volumes were found. The mean volume of the right lung increased from 1.43 ± 0.25 to 8.45 ± 2.66 cm³, according to the cubic function y = –1.592 + 0.0007 × age³ ± 0.851 (R² = 0.84). The volumetric growth of the left lung, from 1.24 ± 0.22 to 6.78 ± 3.03 cm³, followed the cubic model y = –1.110 + 0.0005 × age³ ± 0.794 (R² = 0.78). The total pulmonary volume increased from 2.67 ± 0.47 to 15.22 ± 5.58 cm³, in accordance with the cubic model y = –2.729 + 0.0012 × age³ ± 1.598 (R² = 0.83). The mean volumes of the right and left lungs accounted for 54.9 ± 2.0 and 45.1 ± 2.0 %, respectively, of the total lung volume.

Conclusions

No sex differences are found between the lung volumes in the fetus. The growth of fetal lung volume follows a three-degree polynomial function. Throughout the analyzed period the two lungs grow proportionately to each other, with the volumetric predominance of the right lung. The lung volumes in the fetus are of great relevance in the evaluation of the normal pulmonary growth and the diagnosis of pulmonary hypoplasia.

Motion corrected 3D reconstruction of the fetal thorax from prenatal MRI

In this paper we present a semi-automatic method for analysis of the fetal thorax in genuine three-dimensional volumes. After one initial click we localize the spine and accurately determine the volume of the fetal lung from high resolution volumetric images reconstructed from motion corrupted prenatal Magnetic Resonance Imaging (MRI). We compare the current state-of-the-art method of segmenting the lung in a slice-by-slice manner with the most recent multi-scan reconstruction methods. We use fast rotation invariant spherical harmonics image descriptors with Classification Forest ensemble learning methods to extract the spinal cord and show an efficient way to generate a segmentation prior for the fetal lung from this information for two different MRI field strengths. The spinal cord can be segmented with a DICE coefficient of 0.89 and the automatic lung segmentation has been evaluated with a DICE coefficient of 0.87. We evaluate our method on 29 fetuses with a gestational age (GA) between 20 and 38 weeks and show that our computed segmentations and the manual ground truth correlate well with the recorded values in literature.

Magnetic resonance fetal right lung volumetry and its efficacy in predicting postnatal short-term outcomes of congenital left-sided diaphragmatic hernia

AIM

We aimed to investigate whether the ratio of magnetic resonance imaging (MRI)-measured right lung volume (RLV) to ultrasonography-estimated bodyweight (RLV/BW) and observed-to-expected (o/e) RLV are of diagnostic value in predicting postnatal outcomes of left congenital diaphragmatic hernia (CDH).

MATERIAL AND METHODS

We included 32 CDH patients and 34 control subjects. Manually outlined fetal right lung areas on MRI were multiplied by the slice thickness and added to determine the entire volume. The association between RLV and RLV/BW with gestational age in the controls was examined using regression analysis. RLV/BW and o/e RLV were compared between surviving and non-surviving neonates with CDH.

RESULTS

The expected fetal RLV was derived using the formula RLV (mm(3)) = 1.717 × (gestational weeks)(2.82). In the controls, RLV/BW was nearly constant during the third trimester. The 27 survivors with CDH had a median RLV/BW of 10.7 and a median o/e RLV of 60.0, whereas the five non-surviving neonates had a median RLV/BW of 4.3 and a median o/e RLV of 22.6; the differences were statistically significant.

CONCLUSION

Assessment of fetal lungs by MRI volumetry is reliable for clinical use. RLV/BW and o/e RLV are potential predictors of postnatal outcomes of left CDH.

[Fetal magnetic resonance imaging of thoracic and abdominal malformations]

CLINICAL/METHODICAL ISSUE

Diagnosis and differential diagnosis of fetal thoracic and abdominal malformations.

STANDARD RADIOLOGICAL METHODS

Ultrasound and magnetic resonance imaging (MRI).

METHODICAL INNOVATIONS

In cases of suspected pathologies based on fetal ultrasound MRI can be used for more detailed examinations and can be of assistance in the differential diagnostic process.

PERFORMANCE

Improved imaging of anatomical structures and of the composition of different tissues by the use of different MRI sequences.

ACHIEVEMENTS

Fetal MRI has become a part of clinical routine in thoracic and abdominal malformations and is the basis for scientific research in this field.

PRACTICAL RECOMMENDATIONS

In cases of thoracic or abdominal malformations fetal MRI provides important information additional to ultrasound to improve diagnostic accuracy, prognostic evaluation and surgical planning.

[Indications and technique of fetal magnetic resonance imaging]

CLINICAL/METHODICAL ISSUE

Evaluation and confirmation of fetal pathologies previously suspected or diagnosed with ultrasound.

STANDARD RADIOLOGICAL METHODS

Ultrasound and magnetic resonance imaging (MRI).

METHODICAL INNOVATIONS

Technique for prenatal fetal examination.

PERFORMANCE

Fetal MRI is an established supplementary technique to prenatal ultrasound.

ACHIEVEMENTS

Fetal MRI should only be used as an additional method in prenatal diagnostics and not for routine screening.

PRACTICAL RECOMMENDATIONS

Fetal MRI should only be performed in perinatal medicine centers after a previous level III ultrasound examination.

Fetal MRI: An approach to practice: A review

MRI has been increasingly used for detailed visualization of the fetus in utero as well as pregnancy structures. Yet, the familiarity of radiologists and clinicians with fetal MRI is still limited. This article provides a practical approach to fetal MR imaging. Fetal MRI is an interactive scanning of the moving fetus owed to the use of fast sequences. Single-shot fast spin-echo (SSFSE) T2-weighted imaging is a standard sequence. T1-weighted sequences are primarily used to demonstrate fat, calcification and hemorrhage. Balanced steady-state free-precession (SSFP), are beneficial in demonstrating fetal structures as the heart and vessels. Diffusion weighted imaging (DWI), MR spectroscopy (MRS), and diffusion tensor imaging (DTI) have potential applications in fetal imaging. Knowing the developing fetal MR anatomy is essential to detect abnormalities. MR evaluation of the developing fetal brain should include recognition of the multilayered-appearance of the cerebral parenchyma, knowledge of the timing of sulci appearance, myelination and changes in ventricular size. With advanced gestation, fetal organs as lungs and kidneys show significant changes in volume and T2-signal. Through a systematic approach, the normal anatomy of the developing fetus is shown to contrast with a wide spectrum of fetal disorders. The abnormalities displayed are graded in severity from simple common lesions to more complex rare cases. Complete fetal MRI is fulfilled by careful evaluation of the placenta, umbilical cord and amniotic cavity. Accurate interpretation of fetal MRI can provide valuable information that helps prenatal counseling, facilitate management decisions, guide therapy, and support research studies.