title: Evaluation of variable-angle uniform signal excitation, tilted optimized nonsaturating excitation, and flat radio-frequency pulses in free-breathing non-contrast-enhanced pulmonary MR angiography.
abstract: OBJECTIVE
  To improve the visualization of distal pulmonary vessels at magnetic resonance (MR) angiography so effects of pathologic lung conditions (eg, emboli) on circulation may be more easily observed.
  
  
  METHODS
  Radio-frequency pulses with flip angles that were uniform (flat), linearly increasing (tilted optimized nonsaturating excitation [TONE]), or nonlinearly increasing (variable-angle uniform signal excitation [VUSE]) were used at pulmonary MR angiography in 15 healthy volunteers. Three-dimensional fast imaging with steady-state precession was performed with free breathing. Statistical analysis of signal-to-noise ratios (S/Ns) was performed.
  
  
  RESULTS
  At examinations in both lungs, a higher S/N was achieved with VUSE pulses than with TONE pulses, and with both VUSE pulses and TONE pulses than with flat pulses. Relative dispersion was best with VUSE pulses in all lobes of both lungs. Results were statistically significant (P < .01) in 19 of 27 comparisons in the right lung.
  
  
  CONCLUSIONS
  Higher S/N and better signal uniformity were achieved with VUSE pulses than with TONE or flat pulses at pulmonary MR angiography.
authors.affiliation: Department of Biomedical Engineering, Vanderbilt University Medical Center, Nashville, TN 37232-2675, USA.
authors.forename: J L
authors.initials: JL
authors.lastname: Friedli
authors.forename: C B
authors.initials: CB
authors.lastname: Paschal
mesh_terms: D006801:Humans; D007091:Image Processing, Computer-Assisted; D018810:Magnetic Resonance Angiography; D011651:Pulmonary Artery / Q000033:anatomy & histology*; D011667:Pulmonary Veins / Q000033:anatomy & histology*