Optimized 3D ultrashort echo time pulmonary MRI

Abstract

Purpose To optimize 3D radial ultrashort echo time MRI for high resolution whole-lung imaging. Methods 3D radial ultrashort echo time was implemented on a 3T scanner to investigate the effects of: (1) limited field-of-view excitation, (2) variable density readouts, and (3) radial oversampling. Improvements in noise performance and spatial resolution were assessed through simulation and phantom studies. Their effects on lung and airway visualization in five healthy male human subjects (mean age 32 years) were compared qualitatively through blinded ordinal scoring by two cardiothoracic radiologists using a nonparametric Friedman test (P < 0.05). Relative signal difference between endobronchial air and adjacent lung tissue, normalized to nearby vessel, was used as a surrogate for lung tissue signal. Quantitative measures were compared using the paired Student's t-test (P < 0.05). Finally, clinical feasibility was investigated in a patient with interstitial fibrosis. Results Simulation and phantom studies showed up to 67% improvement in SNR and reduced blurring for short T2* species using all three optimizations. In vivo images showed decreased artifacts and improved lung tissue and airway visualization both qualitatively and quantitatively. Conclusion The use of limited field-of-view excitation, variable readout gradients, and radial oversampling significantly improve the technical quality of 3D radial ultrashort echo time lung images.

Feasibility of free breathing Lung MRI for Radiotherapy using non-Cartesian k-space acquisition schemes

“…Ultrashort echo time (UTE) imaging has be shown to be ideal for imaging lung parenchyma and evaluating lung microstructure at the alveolar level. 10,11 Most 3D UTE sequences combine short non-selective RF pulses with a 3D centre out radial trajectory. Scan time can be reduced by using a more efficient stack-of-spirals trajectory.…”

Targeting and in vivo imaging of non-small–cell lung cancer using nebulized multimodal contrast agents

“…This noninvasive free-breathing protocol is particularly interesting because it can be used in clinical studies with minimal changes. In this respect, the UTE MRI has been shown to be a promising sequence which can be applied in clinical studies of lung morphology, physiology, and pathologies (18,19).…”

“…Briefly, these sequences are based on ultrashort echo time (UTE) and radial sampling of the k-space (10, 13). UTE proton MRI sequences have been demonstrated to be extremely efficient for limiting motion and susceptibility artifacts and for enhancing MRI signal intensity of the lung tissue (14)(15)(16)(17)(18)(19).…”

19F-MRI for monitoring human NK cellsin vivo

“…first accumulate in the lungs which has a low water content (and thus low 1 H signal) and is difficult to image with MR due to susceptibility related signal loss via multiple air-tissue interfaces. Improved imaging protocols that use pulse sequences with shorter echo times, [60][61][62][63] or surface coils that provide high sensitivity in a localized region may improve sensitivity in the lungs to allow imaging of 19 /SzJ (NSG) mice were purchased from The Jackson Laboratory (Bar Harbor, Maine) and used between 8-16 weeks of age. All animals were bred and housed in a pathogen-free facility throughout the study.…”