The Role of Fetal MRI in the assessment of lung anomalies

Abstract

Congential lung anomalies are being detected more frequently nowadays at routine prenatal examination . They classified according toembryologic ,radiologic ,pathologic and clinical viewpoints . The timing of congenital lung malformations and their pathogenesis can be related to specific time points in each of the five embryological developmental stages.They can range from small and asymptomatic entities to large space-occupying masses that require immedi¬ate surgical treatment An understanding of the in utero complications associated with fetal chest masses is essential for appropriate monitoring during pregnancy, treatment recommendations, and delivery management. Ultrasonography (US) is the modality routinely used to screen for fetal anomalies: It is noninva¬sive, inexpensive, and widely available and can provide real-time studies without ionizing radia¬tion. Most US scans are diagnostic, but even in experienced hands they have technical limitations, especially in cases of advanced gestational age, patient obesity, oligohydramnios, improper fetal position . In recent years, MR become a valuable diagnostic modalitiy complementary to Ultrasongraphy . MR imaging offers several technical advantages over US, including a larger field of view, fewer limitations due to the ability to visu¬alize fetal anatomy regardless of fetal presentation and size . The fetal MR imaging shows specific effect in most frequently found lung abnormalities. It can be used to distin¬guish different types of congenital pulmonary airway malformations, identify the anomalous vessels of pulmonary sequestration, and assess the func¬tional effects of bronchogenic cysts. Balanced sequences (steady-state free precession sequences) allow performance of unenhanced thoracic vascular studies, which are useful in the diagnosis of intralobar or ex-tralobar sequestration. It can also give idea about associated cardiovascular anomalies or any associated extrathoracic congintal anomalies. In summary,Prenatal US and MRI showed a high accuracy in the diagnosis of isolated congenital lung lesions with typical imaging findings. However, overall characterization rates were low, because of both a high percentage of complex lesions and of lesions with nonspecific imaging findings, but MRI was better than US in characterizing complex lesions,and providing ad-ditional data useful in establishing prognosis and perinatal management of congenital lung anomalies.