Purpose: Ultrashort echotime (UTE) sequences aim to improve the signal yield in pulmonary magnetic resonance imaging (MRI). We demonstrate the initial results of spiral 3-dimensional (3D) UTE-MRI for combined morphologic and functional imaging in pediatric patients. Methods: Seven pediatric patients with pulmonary abnormalities were included in this observational, prospective, single-center study, with the patients having the following conditions: cystic fibrosis (CF) with middle lobe atelectasis, CF with allergic bronchopulmonary aspergillosis, primary ciliary dyskinesia, air trapping, congenital lobar overinflation, congenital pulmonary airway malformation, and pulmonary hamartoma. Patients were scanned during breath-hold in 5 breathing states on a 3-Tesla system using a prototypical 3D stack-of-spirals UTE sequence. Ventilation maps and signal intensity maps were calculated. Morphologic images, ventilation-weighted maps, and signal intensity maps of the lungs of each patient were assessed intraindividually and compared with reference examinations. Results: With a scan time of ∼15 seconds per breathing state, 3D UTE-MRI allowed for sufficient imaging of both “plus” pathologies (atelectasis, inflammatory consolidation, and pulmonary hamartoma) and “minus” pathologies (congenital lobar overinflation, congenital pulmonary airway malformation, and air trapping). Color-coded maps of normalized signal intensity and ventilation increased diagnostic confidence, particularly with regard to “minus” pathologies. UTE-MRI detected new atelectasis in an asymptomatic CF patient, allowing for rapid and successful therapy initiation, and it was able to reproduce atelectasis and hamartoma known from multidetector computed tomography and to monitor a patient with allergic bronchopulmonary aspergillosis. Conclusion: 3D UTE-MRI using a stack-of-spirals trajectory enables combined morphologic and functional imaging of the lungs within ~115 second acquisition time and might be suitable for monitoring a wide spectrum of pulmonary diseases.
RI of the lungs is technically challenging because of physical limitations such as inherently low proton density and intrinsically short T2* relaxation times, resulting in a low signal-to-noise ratio. Ultrashort echo time (UTE) sequences address these limitations with a minimized echo time (TE) (< 100 µsec) to accomplish the readout shortly after excitation (1-5).Two three-dimensional (3D) UTE gradient-echo sequences have been proposed that allow for full 3D coverage of the lungs. Using a stack-of-spirals trajectory (6), Mugler et al introduced fast image acquisition within a single breath hold (7). Another approach, by Mendes Pereira et al (10), implemented a "Koosh ball" (a toy ball made of rubber filaments radiating from its center) trajectory (8,9) to a self-navigated 3D UTE sequence. Here, sampling of the k-space center signal (direct current [DC] signal) during each readout allows for k-space separation into different breathing states (11-13), enabling freebreathing imaging within a few minutes.Recently, two studies explored functional lung imaging with UTE MRI, providing images with proton density-weighted contrast, high signal-to-noise ratio, and high spatial resolution, as well as simultaneous functional information (10,14). However, the literature regarding 3D UTE MRI is sparse, and the effect of different breathing maneuvers on functional image analyses has not been sufficiently investigated. Our hypothesis was that functional image analysis of the lung can be performed similarly when performing UTE sequences at single breathhold and at free-breathing acquisition.Therefore, the purpose of this study was to compare a 3D stack-of-spirals UTE sequence during breath hold and a self-navigated Koosh ball UTE sequence at free breathing to discern image quality and suitability This copy is for personal use only. To order printed copies, contact
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