Breath-hold MRI in evaluating patients with pectus excavatum

Pectus excavatum (PE) is a congenital condition in which the sternum is displaced posteriorly with associated changes in the adjacent costal cartilages. The aetiology of PE is uncertain although various underlying abnormalities of the diaphragm have been implicated. There is sparse information regarding the use of fast MRI in evaluating the deformity. Our aims were to use fast MRI to evaluate static and respiratory-related dynamic chest wall characteristics, the extent of cardiac displacement and diaphragmatic excursion in patients. FLASH and TurboFLASH MR sequences in axial and coronal planes were performed on the thoraces of six young patients with PE and six individually matched healthy controls during full inspiratory and full expiratory breath-holds. The Pectus Index was derived from chest wall measurements using axial images. The distances of the left and right cardiac borders from the midline were measured using axial images, and excursion of the dome of each hemidiaphragm was measured using coronal images. The degree of sternal depression worsened substantially in expiration. Anterior chest wall movement was similar in the two groups. Patients had significantly flatter chests than the controls. There was a trend towards leftward cardiac displacement in the patients (maximum distance between left heart border and midline during full expiration 99.5 mm in patients and 91.8 mm in controls). The right diaphragmatic dome excursion was greater than the left in the controls (53.6 mm and 47.4 mm, respectively), but this was not seen in the patients (50.2 mm and 50.4 mm, respectively). It is concluded that fast MRI is very informative in evaluating skeletal abnormalities, chest wall motion, and cardiac and diaphragmatic changes seen in PE.