EVALUATION OF VARIABLE-ANGLE UNIFORM SIGNAL EXCITATION, TILTED OPTIMIZED NONSATURATING EXCITATION, AND FLAT RADIOFREQUENCY PULSES IN FREE-BREATHING NON-CONTRAST-ENHANCED PULMONARY MR-ANGIOGRAPHY

PURPOSE: To improve the visualization of distal pulmonary vessels at m agnetic resonance (MR) angiography so effects of pathologic lung condi tions leg, emboli) on circulation may be more easily observed. MATERIA LS AND METHODS: Radiofrequency pulses with flip angles that were unifo rm (flat), linearly increasing (tilted optimized nonsaturating excitat ion [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 precessi on was performed with free breathing. Statistical analysis of signal-t o-noise ratios (S/Ns) was performed. RESULTS: At examinations in both lungs, a higher S/N was achieved with VUSE pulses than with TONE pulse s, and with both VUSE pulses and TONE pulses than with flat pulses. Re lative dispersion was best with VUSE pulses in all lobes of both lungs . Results were statistically significant (P < .01) in 19 of 27 compari sons in the right lung. CONCLUSION: Higher S/N and better signal unifo rmity were achieved with VUSE pulses than with TONE or flat pulses at pulmonary MR angiography.