Virtual bronchoscopy in the fetus

Prenatal ultrasonic features of a mediastinal teratoma: A case report and literature review

Fetal mediastinal teratomas represent only 10% of congenital teratomas in children and 2.6% of all mediastinal masses in children. Teratomas have multifactorial etiology, such as chromosomal abnormalities. Fetal mediastinal teratomas are rare. Mediastinal teratomas can cause hydrops fetalis, fetal demise, and neonatal respiratory distress; therefore, accurate perinatal management and interventions are very important. We describe a case of fetal mediastinal teratoma wherein the cystic fluid in the fetal tumor was aspirated and confirmed by surgical pathology after birth at the authors' center. The teratoma in this case was characterized by a large single cystic mass with clear borders in the anterosuperior mediastinum, which grew rapidly and was closely related to the thymus. The infant was healthy at birth, and the tumor was surgically removed the age of 1 year. The postoperative course was uneventful, and the patient was in good health 6 years postoperatively. This case and literature review suggests that ultrasound examination can accurately diagnose fetal mediastinal teratomas, which is beneficial to provide an accurate basis for fetal prenatal intervention and treatment. Additionally, an important ultrasound feature of a fetal unicystic mediastinal teratoma is a saddle-shaped mass with clear boundaries, which provided an accurate reference for the diagnosis of a fetal cystic mediastinal teratoma by prenatal ultrasonography.

EXIT-to-airway: Fundamentals, prenatal work-up, and technical aspects

Ex-utero intrapartum treatment (EXIT) is a delivery strategy developed to manage a variety of prenatally diagnosed conditions in the transition to newborn life. This procedure allows control and provides time for intervention in otherwise life-threatening malformations, such as congenital upper airway obstructions. EXIT-to-airway has changed the outcome of fetuses with these anomalies. The main purpose of this intervention is to improve the safety of establishing a reliable airway at birth. Maximal but controlled uterine relaxation to maintain feto-maternal perfusion and thus gas exchange, while keeping the fetal and maternal well-being are the paradigms of any type of EXIT. The most important aspect of fetal airway management is to consolidate a highly trained, well-coordinated, multidisciplinary team that is prepared for every contingency. A comprehensive prenatal assessment, including ultrasound, fetal echocardiogram, fetal MRI, and genetic testing is imperative for patient selection. Extensive preoperative planning, ad-hoc team meetings, and surgical simulations for challenging cases are critical strategies to achieve the best outcomes. This article outlines the prenatal work-up, decision making, technical aspects, and principles for a successful EXIT-to-airway procedure.

Congenital High Airway Obstruction Syndrome (CHAOS): Virtual Navigation in the Fetal Airways After Intrauterine Endoscopic Treatment

BACKGROUND

Congenital high airway obstruction syndrome (CHAOS) involves the partial or complete obstruction of the fetal upper airways, usually caused by atresia or stenosis of the larynx or trachea. The obstruction of bronchial tree leads to lung distension, diaphragmatic eversion, and cardiac dysfunction, which can result in fetal death.

CASE

A primigravid 19-year-old was diagnosed with CHAOS at 19³ weeks gestation. Virtual navigation using magnetic resonance imaging (MRI) data was used to visualize the fetal airways after intrauterine endoscopic laser decompression. A perforation in the fetal larynx/trachea was identified and the diagnosis was modified to tracheal stenosis. Cesarean delivery occurred at 31⁵ weeks using an ex utero intrapartum treatment (EXIT) procedure. The neonatology team were unable to perform intubation, suggesting a final diagnosis of tracheal atresia. The male newborn weighed 1920 g and died 1 hour later.

CONCLUSION

3D virtual bronchoscopy is a non-invasive approach to visualizing the fetal upper airways and can be used to diagnose and manage CHAOS.

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.

A Multimodality Navigation System for Endoscopic Fetal Surgery: A Phantom Case Study for Congenital Diaphragmatic Hernia

This article presents a multi-modality tracking and navigation system achieved by merging optical tracking and ultrasound imaging into a novel navigation software to help in surgical pre-planning and real-time target setting and guidance. Fetal surgeries require extensive experience in coordination of hand-eye-ultrasound-surgical equipment, knowledge, and precise assessment of relative anatomy. While there are navigation systems available for similar constrained working spaces in arthroscopic and cardiovascular procedures, fetal minimally invasive surgery does not yet have a dedicated navigation platform capable of supporting robotic instruments that can be adapted to the set of unique procedures. This article discusses the testing of the novel multi-modality navigation system in a phantom environment developed for this purpose. The outcomes suggest that the subjects demonstrated an increase in average reaching accuracy by about 60% and an overall reduction in time taken by 33.6%. They also showed higher levels of confidence in reaching the targets, which was visualised from the pattern of trajectory of movements during the procedure. To evaluate the navigation system, a phantom surgical environment was found necessary. Therefore, the article also discusses the details of the development of a fetal phantom environment for congenital diaphragmatic hernia for surgical testing, evaluation, and training. A surgical procedure was conducted on the phantom using the proposed tracking navigation system and using only ultrasound.

Applicability of three-dimensional imaging techniques in fetal medicine

Objective

To generate physical models of fetuses from images obtained with three-dimensional ultrasound (3D-US), magnetic resonance imaging (MRI), and, occasionally, computed tomography (CT), in order to guide additive manufacturing technology.

Materials and Methods

We used 3D-US images of 31 pregnant women, including 5 who were carrying twins. If abnormalities were detected by 3D-US, both MRI and in some cases CT scans were then immediately performed. The images were then exported to a workstation in DICOM format. A single observer performed slice-by-slice manual segmentation using a digital high resolution screen. Virtual 3D models were obtained from software that converts medical images into numerical models. Those models were then generated in physical form through the use of additive manufacturing techniques.

Results

Physical models based upon 3D-US, MRI, and CT images were successfully generated. The postnatal appearance of either the aborted fetus or the neonate closely resembled the physical models, particularly in cases of malformations.

Conclusion

The combined use of 3D-US, MRI, and CT could help improve our understanding of fetal anatomy. These three screening modalities can be used for educational purposes and as tools to enable parents to visualize their unborn baby. The images can be segmented and then applied, separately or jointly, in order to construct virtual and physical 3D models.

Comparison Between 1.5-T and 3-T MRI for Fetal Imaging: Is There an Advantage to Imaging With a Higher Field Strength?

OBJECTIVE

Fetal MRI at 3 T is emerging as a promising modality for evaluating fetal anatomy. The objective of this study was to compare the quality of images obtained with commonly used fetal imaging sequences at 1.5 T and 3 T. We hypothesized that the visualization and anatomic detail of fetal structures would be better at 3 T than at 1.5 T.

MATERIALS AND METHODS

A retrospective search of the radiology department database at our institution identified 58 fetal MRI examinations performed at 3 T to evaluate body abnormalities during the period from July 2012 to February 2014. A blind comparison was conducted between these examinations and 58 1.5-T MRI examinations of age-matched fetuses undergoing evaluation for similar abnormalities during the same period. The anatomic structures analyzed included the bowel, liver, kidney, airway, cartilage, and spine. Scores for the depiction of anatomic structures ranged from 0 to 4, with 4 denoting the best depiction.

RESULTS

Fetal imaging at 3 T was associated with higher imaging scores in the evaluation of the cartilage and spine when single-shot turbo spin-echo (SSTSE) and steady-state free precession (SSFP) sequences were used and in the assessment of most structures (e.g., bowel, liver, kidney, cartilage, and spine) when SSFP sequences were used. The mean scores for all structures evaluated with the use of SSTSE sequences were higher when MRI was performed at 3 T than at 1.5 T; similar findings were noted when SSFP sequences were used. Evaluation of imaging scores with regard to gestational age showed that scores improved with increasing gestational age on 1.5-T MRI but not on 3-T MRI. Overall, more imaging artifacts were found when imaging was performed at 3 T than at 1.5 T.

CONCLUSION

An overall advantage to performing fetal imaging at 3 T was made evident by the higher imaging scores obtained with 3-T MRI versus 1.5-T MRI when different fetal anatomic structures were evaluated. These higher scores were predominantly associated with use of SSFP sequences. The findings of this study and future advancements in MRI software and 3-T protocols may allow optimal visualization and examination of fetal pathologic abnormalities, thus better identifying fetal and maternal needs both prenatally and postnatally.

Computer-assisted surgical planning and intraoperative guidance in fetal surgery: a systematic review

Fetal surgery has become a clinical reality, with interventions for twin‐to‐twin transfusion syndrome (TTTS) and spina bifida demonstrated to improve outcome. Fetal imaging is evolving, with the use of 3D ultrasound and fetal MRI becoming more common in clinical practise. Medical imaging analysis is also changing, with technology being developed to assist surgeons by creating 3D virtual models that improve understanding of complex anatomy, and prove powerful tools in surgical planning and intraoperative guidance.

We introduce the concept of computer‐assisted surgical planning, and present the results of a systematic review of image reconstruction for fetal surgical planning that identified six articles using such technology.

Indications from other specialities suggest a benefit of surgical planning and guidance to improve outcomes. There is therefore an urgent need to develop fetal‐specific technology in order to improve fetal surgical outcome. © 2015 The Authors. Prenatal Diagnosis published by John Wiley & Sons Ltd.

What's already known about this topic?

Fetal surgery has now become a clinical reality, with interventions such as laser treatment for twin‐to‐twin transfusion syndrome (TTTS) and open fetal surgery for spina bifida demonstrated in randomised control trials to improve neonatal outcome

Other specialities are increasingly utilising computer‐assisted surgical planning software, with evidence that this can improve outcome

What does this study add?

We feel that there is an urgent need to develop fetal‐specific technology for surgical planning as it is likely to play an important role in improving outcomes from fetal surgery

Physical model from 3D ultrasound and magnetic resonance imaging scan data reconstruction of lumbosacral myelomeningocele in a fetus with Chiari II malformation

Rapid prototyping is becoming a fast-growing and valuable technique for physical models in case of congenital anomalies. Manufacturing models are generally built from three-dimensional (3D) ultrasound, computed tomography, and fetal magnetic resonance imaging (MRI) scan data. Physical prototype has demonstrated to be clinically of value in case of complex fetal malformations and may improve antenatal management especially in cases of craniosynostosis, orofacial clefts, and giant epignathus. In addition, it may enhance parental bonding in visually impaired parents and have didactic value in teaching program. Hereby, the first 3D physical model from 3D ultrasound and MRI scan data reconstruction of lumbosacral myelomeningocele in a third trimester fetus affected by Chiari II malformation is reported.

Virtual bronchoscopy for evaluating cervical tumors of the fetus

We report on four cases of fetal cervical tumor, comprising three lymphangiomas and one teratoma, evaluated by ultrasound and magnetic resonance imaging (MRI) between 26 and 37 weeks' gestation. The aim was to investigate the use of virtual bronchoscopy to evaluate fetal airway patency in each case. A three-dimensional (3D) model of the airway was created from overlapping image layers generated by MRI. The files obtained were manipulated using 3D modeling software, allowing the virtual positioning of observation cameras, adjustment of lighting parameters and creation of simulated 3D movies for analysis of a virtual path through the model. In all fetuses, fetal airway patency was clearly demonstrated by virtual bronchoscopy and this was confirmed postnatally. MRI with virtual bronchoscopy could become a useful tool for studying fetal airway patency in cases of cervical tumor.