Structural and perfusion magnetic resonance imaging of congenital lung malformations

Congenital lung malformations

Congenital lung malformations (CLMs) are rare developmental anomalies of the lung, including congenital pulmonary airway malformations (CPAM), bronchopulmonary sequestration, congenital lobar overinflation, bronchogenic cyst and isolated congenital bronchial atresia. CLMs occur in 4 out of 10,000 live births. Postnatal presentation ranges from an asymptomatic infant to respiratory failure. CLMs are typically diagnosed with antenatal ultrasonography and confirmed by chest CT angiography in the first few months of life. Although surgical treatment is the gold standard for symptomatic CLMs, a consensus on asymptomatic cases has not been reached. Resection, either thoracoscopically or through thoracotomy, minimizes the risk of local morbidity, including recurrent infections and pneumothorax, and avoids the risk of malignancies that have been associated with CPAM, bronchopulmonary sequestration and bronchogenic cyst. However, some surgeons suggest expectant management as the incidence of adverse outcomes, including malignancy, remains unknown. In either case, a planned follow-up and a proper transition to adult care are needed. The biological mechanisms through which some CLMs may trigger malignant transformation are under investigation. KRAS has already been confirmed to be somatically mutated in CPAM and other genetic susceptibilities linked to tumour development have been explored. By summarizing current progress in CLM diagnosis, management and molecular understanding we hope to highlight open questions that require urgent attention.

The argument for utilising magnetic resonance imaging as a tool for monitoring lung structure and function in pediatric patients

INTRODUCTION

Although historically challenging to perform in the lung, technological advancements have made Magnetic Resonance Imaging (MRI) increasingly applicable for pediatric pulmonary imaging. Furthermore, a wide array of functional imaging techniques has become available that may be leveraged alongside structural imaging for increasingly sensitive biomarkers, or as outcome measures in the evaluation of novel therapies.

AREAS COVERED

In this review, recent technical advancements and modern methodologies for structural and functional lung MRI are described. These include ultrashort echo time (UTE) MRI, free-breathing contrast agent-free, functional lung MRI, and hyperpolarized gas MRI, amongst other techniques. Specific examples of the application of these methods in children are provided, principally drawn from recent research in asthma, bronchopulmonary dysplasia, and cystic fibrosis.

EXPERT OPINION

Pediatric lung MRI is rapidly growing, and is well poised for clinical utilization, as well as continued research into early disease detection, disease processes, and novel treatments. Structure/function complementarity makes MRI especially attractive as a tool for increased adoption in the evaluation of pediatric lung disease. Looking toward the future, novel technologies, such as low-field MRI and artificial intelligence, mitigate some of the traditional drawbacks of lung MRI and will aid in improving access to MRI in general, potentially spurring increased adoption and demand for pulmonary MRI in children.

Congenital lung abnormalities on magnetic resonance imaging: the CLAM study

OBJECTIVES

Follow-up of congenital lung abnormalities (CLA) is currently done with chest computer tomography (CT). Major disadvantages of CT are exposure to ionizing radiation and need for contrast enhancement to visualise vascularisation. Chest magnetic resonance imaging (MRI) could be a safe alternative to image CLA without using contrast agents. The objective of this cohort study was to develop a non-contrast MRI protocol for the follow-up of paediatric CLA patients, and to compare findings on MRI to postnatal CT in school age CLA patients.

METHODS

Twenty-one CLA patients, 4 after surgical resection and 17 unoperated (mean age 12.8 (range 9.4-15.9) years), underwent spirometry and chest MRI. MRI was compared to postnatal CT on appearance and size of the lesion, and lesion associated abnormalities, such as hyperinflation and atelectasis.

RESULTS

By comparing school-age chest MRI to postnatal CT, radiological appearance and diagnostic interpretation of the type of lesion changed in 7 (41%) of the 17 unoperated patients. In unoperated patients, the relative size of the lesion in relation to the total lung volume remained stable (0.9% (range - 6.2 to + 6.7%), p = 0.3) and the relative size of lesion-associated parenchymal abnormalities decreased (- 2.2% (range - 0.8 to + 2.8%), p = 0.005).

CONCLUSION

Non-contrast-enhanced chest MRI was able to identify all CLA-related lung abnormalities. Changes in radiological appearance between MRI and CT were related to CLA changes, patients' growth, and differences between imaging modalities. Further validation is needed for MRI to be introduced as a safe imaging method for the follow-up of paediatric CLA patients.

KEY POINTS

• Non-contrast-enhanced chest MRI is able to identify anatomical lung changes related to congenital lung abnormalities, including vascularisation. • At long-term follow-up, the average size of congenital lung abnormalities in relation to normal lung volume remains stable. • At long-term follow-up, the average size of congenital lung abnormalities associated parenchymal abnormalities such as atelectasis in relation to normal lung volume decreases.

Neonatal cardiorespiratory imaging-a multimodality state-of-the-art review

Advanced cardiorespiratory imaging of the chest with ultrasound (US), computed tomography (CT) and magnetic resonance imaging (MRI) plays an important role in diagnosing respiratory and cardiac conditions in neonates when radiography and echocardiography alone are not sufficient. This pictorial essay highlights the particularities, clinical indications and technical aspects of applying chest US, cardiac CT and cardiorespiratory MRI techniques specifically to neonates, summarising the first session of the European Society of Paediatric Radiology's cardiothoracic task force.

Pediatric large airway imaging: evolution and revolution

Infants and children often present with respiratory symptoms referable to the airway. For these pediatric patients, airway imaging is frequently performed to evaluate for underlying disorders of the large airway. Various imaging modalities have been used to evaluate the pediatric large airway, and pediatric airway imaging techniques have continued to evolve. Therefore, clear understanding of the status and new advances in pediatric large airway imaging is essential for practicing radiologists to make timely and accurate diagnoses, which can lead to optimal pediatric patient management.

Magnetic resonance imaging for congenital lung malformations

Congenital lung malformations are most often identified on prenatal US screening. Fetal MRI is often performed to further evaluate these lesions. Although some of these lesions might cause prenatal or early postnatal symptoms that require urgent management, the majority are asymptomatic at birth and might be subtle or invisible on chest radiographs. Postnatal imaging is frequently deferred until 3-6 months of age, when surgery or long-term conservative management is contemplated. High-quality imaging and interpretation is needed to assist with appropriate decision-making. Contrast-enhanced chest CT, typically with angiographic technique, has been the usual postnatal imaging choice. In this review, the author discusses and illustrates the indications and use of postnatal MR imaging for bronchopulmonary malformations as well as some differential diagnoses and the advantages and disadvantages of MR versus CT.

Pediatric Congenital Lung Malformations: Imaging Guidelines and Recommendations

Congenital lung malformations are a spectrum of developmental anomalies comprised of malformations of the lung parenchyma, airways, and vasculature. Imaging assessment plays a pivotal role in the initial diagnosis, management, and follow-up evaluation of congenital lung malformations in the pediatric population. However, there is currently a lack of practical imaging guidelines and recommendations for the diagnostic imaging assessment of congenital lung malformations in infants and children. This article reviews the current evidence regarding the imaging evaluation of congenital lung malformations and provides up-to-date imaging recommendations for pediatric congenital lung malformations.

Clinical application of ultrashort echo-time MRI for lung pathologies in children

Lung magnetic resonance imaging (MRI) is considered to be challenging, because the low proton density of the tissue, fast signal decay, and respiratory artefacts hamper adequate image quality. MRI of the lungs and thorax is increasingly used in the paediatric population, because it is a radiation-free alternative to chest CT. Recently, ultrashort echo-time (UTE) sequences have been introduced into clinical MRI protocols, in order to improve the contrast-to-noise ratio due to reduced susceptibility artefacts and to depict structural alterations comparable to CT. The purpose of this review is to provide an overview of various clinical conditions and pathologies in the paediatric chest depicted by an UTE sequence, the so-called three-dimensional (3D) Cones sequence, in comparison with conventional MRI sequences. Besides describing typical features of cystic fibrosis, we present UTE application in other more or less common paediatric lung pathologies, for instance, interstitial pneumopathies, pulmonary infections, and congenital pulmonary malformations.

Novel Thoracic MRI Approaches for the Assessment of Pulmonary Physiology and Inflammation

Excessive pulmonary inflammation can lead to damage of lung tissue, airway remodelling and established structural lung disease. Novel therapeutics that specifically target inflammatory pathways are becoming increasingly common in clinical practice, but there is yet to be a similar stepwise change in pulmonary diagnostic tools. A variety of thoracic magnetic resonance imaging (MRI) tools are currently in development, which may soon fulfil this emerging clinical need for highly sensitive assessments of lung structure and function. Given conventional MRI techniques are poorly suited to lung imaging, alternate strategies have been developed, including the use of inhaled contrast agents, intravenous contrast and specialized lung MR sequences. In this chapter, we discuss technical challenges of performing MRI of the lungs and how they may be overcome. Key thoracic MRI modalities are reviewed, namely, hyperpolarized noble gas MRI, oxygen-enhanced MRI (OE-MRI), ultrashort echo time (UTE) MRI and dynamic contrast-enhanced (DCE) MRI. Finally, we consider potential clinical applications of these techniques including phenotyping of lung disease, evaluation of novel pulmonary therapeutic efficacy and longitudinal assessment of specific patient groups.

Revising the classification of lung sequestrations

PURPOSES

The classification of lung sequestrations distinguishes between extralobar and intralobar types, according to their venous drainage - systemic vs pulmonary - and the presence or absence of independent pleura. However, imaging, surgical and/or pathological findings often differ from this description. The objectives of this article are to quantify the percentage of lung sequestrations that do not fit the classic description of extra- and intralobar types and to evaluate the accuracy of the currently used classification.

METHODS

A retrospective search identified all children with a confirmed lung sequestration diagnosed and treated in our Hospital over the last 10 years. Two senior pediatric radiologists reviewed their contrast-enhanced computed tomography chest scans and evaluated the main anatomical features that define sequestrations, including pleura, arterial and venous pattern, airways and lung parenchyma. We compared the imaging-, surgical- and pathological findings to those described for extra- and intralobar sequestrations.

RESULTS

25 children (20 M, 5 F) conform the series. Only 13 lesions (52%) filled all criteria described for an extra- or intralobar sequestration. The remaining 12 lesions (48%) had at least one differing criteria, including incomplete independent pleura (n = 2; 8%), mixed systemic and pulmonary arterial supply (n = 1; 4%) or venous drainage (n = 3; 12%), normal connection to airway (n = 1; 4%) and/or coexistent congenital lung anomalies (n = 11; 44%).

CONCLUSION

Lung sequestrations seem to represent a spectrum of anomalies rather than separated entities. Therefore, a detailed description of their main anatomical features could be more relevant for clinicians and surgeons that the rigid distinction in intra- and extralobar sequestration currently applied.

Pulmonary sequestration: What the radiologist should know

Pulmonary sequestration consists of a nonfunctioning mass of lung tissue, either sharing the pleural envelope of the normal lung (intralobar) or with its own pleura (extralobar), lacking normal communication with the tracheobronchial tree and receiving its arterial supply by one or more systemic vessels. It is the second most common congenital lung anomaly according to pediatric case series, but its real prevalence is likely to be underestimated, and imaging plays a key role in the diagnosis and treatment management of the condition and its potential complications. We will give a brief overview of the pathophysiology, clinical presentation and imaging findings of intra- and extralobar pulmonary sequestration, with particular reference to multidetector computed tomography as part of a powerful and streamlined diagnostic approach.