title: MR microimaging of the lung using volume projection encoding.
abstract: Radial acquisition (RA) techniques have been extended to produce isotropic, three-dimensional images of lung in live laboratory animals at spatial resolution down to 0.013 mm3 with a signal-to-noise ratio of 30:1. The pulse sequence and reconstruction algorithm have been adapted to allow acquisition of image matrices of up to 256(3) in less than 15 min. Scan-synchronous ventilation has been incorporated to limit breathing motion artifacts. The imaging sequence permits randomizing and/or discarding selected views to minimize the consequences of breathing motion. The signal in lung parenchyma was measured as a function of flip angle (alpha) for different repetition times and found to follow the predictions for which there is an optimum excitation (Ernst) angle. A single T1 relaxation value of 780 +/- 54 ms fits all data from six guinea pigs at 2.0 T. This T1 value parameterizes the signal and allows for a priori optimization, such as calculation of the Ernst angle appropriate for lung imaging.
authors.affiliation: Center for In Vivo Microscopy, Department of Radiology, Duke University Medical Center, Durham, North Carolina 27710-3302, USA.
authors.forename: M D
authors.initials: MD
authors.lastname: Shattuck
authors.forename: S L
authors.initials: SL
authors.lastname: Gewalt
authors.forename: G H
authors.initials: GH
authors.lastname: Glover
authors.forename: L W
authors.initials: LW
authors.lastname: Hedlund
authors.forename: G A
authors.initials: GA
authors.lastname: Johnson
mesh_terms: D000818:Animals; D006168:Guinea Pigs; D008168:Lung / Q000033:anatomy & histology*; D008279:Magnetic Resonance Imaging / Q000379:methods*