Thick–section, single breath–hold magnetic resonance pulmonary angiography

Rationale and objectives. Approaches to performing magnetic resonance angiography (MRA) of the pulmonary vasculature are described using very fast (repetition time [TR] <13 mseconds) radiofrequency (rf)-spoiled, gradient-recalled pulse sequences and the standard quadrature body imaging coil of a commercial 1.5-T MR imaging system. METHODS AND RESULTS. Signal-to-noise (SNR) is improved by signal averaging (Nex ≥ 4) in a two-dimensional, single thick-section approach and by volume acquisition (Nex = 1) in a three-dimensional approach. Blood signal loss is minimized by using short, asymmetric echoes (echo time [TE] ≤ 2.7 mseconds). Respiratory motion is eliminated by keeping the scan time short enough (approximately 15 seconds) for image acquisition within a single breath-hold. Cardiac motion artifacts are reduced with section orientations that avoid intersecting the heart and/or use of small flip angle (α ≤ 25°). CONCLUSIONS. Images of healthy volunteers showed that while single thick sections have superior SNR, the three-dimensional approach appears to produce better visualization of the peripheral vascular segments and offers improved ability to process the images to remove overlapping structures.