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. Magn Reson Med 70:1241–1250, 2013.

The National Heart, Lung, and Blood Institute Severe Asthma Research Program (SARP) has characterized over the past 10 years 1,644 patients with asthma, including 583 individuals with severe asthma. SARP collaboration has led to a rapid recruitment of subjects and efficient sharing of samples among participating sites to conduct independent mechanistic investigations of severe asthma. Enrolled SARP subjects underwent detailed clinical, physiologic, genomic, and radiological evaluations. In addition, SARP investigators developed safe procedures for bronchoscopy in participants with asthma, including those with severe disease. SARP studies revealed that severe asthma is a heterogeneous disease with varying molecular, biochemical, and cellular inflammatory features and unique structure–function abnormalities. Priorities for future studies include recruitment of a larger number of subjects with severe asthma, including children, to allow further characterization of anatomic, physiologic, biochemical, and genetic factors related to severe disease in a longitudinal assessment to identify factors that modulate the natural history of severe asthma and provide mechanistic rationale for management strategies.

During the past several years there has been extensive development and application of hyperpolarized helium‐3 (HP ³He) magnetic resonance imaging (MRI) in clinical respiratory indications such as asthma, chronic obstructive pulmonary disease, cystic fibrosis, radiation‐induced lung injury, and transplantation. This review focuses on the state‐of‐the‐art of HP ³He MRI and its application to clinical pulmonary research. This is not an overview of the physics of the method, as this topic has been covered previously. We focus here on the potential of this imaging method and its challenges in demonstrating new types of information that has the potential to influence clinical research and decision making in pulmonary medicine. Particular attention is given to functional imaging approaches related to ventilation and diffusion‐weighted imaging with applications in chronic obstructive pulmonary disease, cystic fibrosis, asthma, and radiation‐induced lung injury. The strengths and challenges of the application of ³He MRI in these indications are discussed along with a comparison to established and emerging imaging techniques. J. Magn. Reson. Imaging 2010;32:1398–1408.

Standard, MR spin‐warp sampling strategies acquire data on a rectangular k‐space grid. That method samples data from the “corners” of k‐space, i.e., data that lie in a region of k‐space outside of an ellipse just inscribed in the rectangular boundary. Illustrative calculations demonstrate that the data in the corners of k‐space contribute to the useful resolution only if an interpolation method such as a zero‐filled reconstruction is used. The consequences of this finding on data acquisition and data windowing strategies are discussed. A further implication of this result is that the spatial resolution of images reconstructed with zero‐filling (but without radial windowing) is expected to display angular dependence, even when the phase‐ and frequency‐encoded resolutions are identical. This hypothesis is experimentally verified with a slit geometry phantom. It is also observed that images reconstructed without zero‐filling do not display the angular dependence of spatial resolution predicted solely by the maximal k‐space extent of the raw data. The implications of these results for 3D contrast‐enhanced angiographic acquisitions with elliptical centric view ordering are explored with simulations. J. Magn. Reson. Imaging 2001;14:270–280.