Dynamic contrast-enhanced magnetic resonance angiography of the thoracic vessels: An intraindividual comparison of different k-space acquisition strategies

Objectives: The combination of parallel acquisition (generalized autocalibrating partially parallel acquisitions) and time-resolved three-dimensional (3D) view-sharing techniques is a promising tool for dynamic contrast-enhanced 3D-magnetic resonance angiography (MRA). We evaluated the influence of different k-space acquisition strategies on image quality for a recently developed time-resolved echo-shared angiographic technique during a contrast-enhanced 3D-MRA of the thoracic vessels. Materials and Methods: In 20 patients (16 men, 4 women; range, 28-75 years), 2 dynamic MRA protocols with different k-space acquisition strategies were performed on a 1.5-T whole-body scanner (MAGNETOM Avanto, Siemens AG, Erlangen, Germany) during injection of 5 mL (flow-rate, 3 mL/s) gadobutrol. For protocol 1, the central-region which was updated with every cycle included 20% of the entire k-space (protocol 2: 10%), the peripheral-region was undersampled by a factor of 10 (protocol 2: 5%). Image quality and details were compared visually. Signal-to-noise ratio and sharpness of vessel borders were estimated. Results: Morphologic and functional assessment of the pulmonary arteries and the aorta was significantly improved for protocol 1. The sharpness of vessel borders (3.3 mm vs. 4.1 mm; P = 0.001), image quality, and the visibility of image details were significantly improved for protocol 1 compared with protocol 2. Conclusion: The size of the central region that is updated for every frame seems to be more crucial for image quality of echo-shared angiographic techniques than the sampling density in the periphery of the k-space.