Improved artery delineation in dual‐stack coronary magnetic resonance angiography using parallel imaging at 3 T

Abstract

Purpose: To improve vessel sharpness and T2 preparation (T2Prep) in dual-stack three-dimensional coronary magnetic resonance angiography (MRA) by shortening the time delays between the magnetization preparation pulses and the imaging stacks using sensitivity encoding (SENSE) at 3 T. Materials and Methods:By combining dual-stack threedimensional coronary MRA with the parallel imaging technique SENSE at 3 T, the acquisition duration of each threedimensional imaging stack was shortened by a factor of 2. The proposed technique was implemented and tested in experiments with a moving phantom and in measurements on six healthy volunteers. Results:The time delay between the navigator, T2Prep, and second imaging stack was reduced by 37%, relative to conventional dual-stack angiography without parallel imaging. This enabled the achievement of comparable highvessel sharpness values for the left and the right coronary arteries relative to values known from conventional singlestack three-dimensional coronary MRA at 3 T. Conclusion:Parallel imaging allows for improved vessel visualization in dual-stack coronary MRA, given shorter temporal delays between navigator, T2Prep, and the actual image acquisitions, and thus considerably facilitates simultaneous acquisition of high-resolution angiograms of the left and right coronary systems. CORONARY MAGNETIC RESONANCE angiography (MRA) performed during free breathing and with respiratory navigator gating for real-time motion compensation has shown to be a promising technique for the visualization of potential coronary artery disease (1). The limited scan efficiency by the short data acquisition window of relative intrinsic cardiac rest during middiastole (2) and a respiratory gating efficiency of about 50% can be considered drawbacks of this approach. A single three-dimensional acquisition thus takes about 10 minutes. With two three-dimensional scans to cover both the left and the right coronary arterial systems, the total examination time, including planning and additional localizer scans, can easily exceed 45 minutes.An improvement in scan efficiency and a reduction of scan time can be achieved by the simultaneous acquisition of multiple independent three-dimensional image stacks, covering the main vessels of both coronary systems, as proposed by Manke et al (3). Since the two independent stacks are measured consecutively during mid-diastole, the overall data acquisition time within one cardiac cycle is prolonged by a factor of 2, relative to a conventional single-stack approach (4). Thus, conventional dual-stack angiography is more sensitive to artifacts by cardiac and respiratory motion. In addition, only one respiratory navigator is measured prior to the acquisition of the first three-dimensional stack, and the determined diaphragmatic displacement is used to subsequently calculate positional corrections for both successively sampled imaging stacks. This potentially violates previous findings stating that a short time delay between the navigator acquisition and the actual scanni...

Coronary MR angiography at 3T during diastole and systole

“…This concept has been demonstrated by Huber et al (22) where coronary image quality was preserved despite the two‐fold reduction of scan time achieved by using SENSE at 3T. Utilizing SENSE at 3T has also been shown to be a valuable combination to shorten acquisition widows allowing for simultaneous acquisition of the right and left coronary arteries using two different 3D slabs during diastole without compromising image quality (23).…”

Improved SNR efficiency in gradient echo coronary MRA with high temporal resolution using parallel imaging

“…At 3 T, Huber et al (26) demonstrated that 2‐fold SENSE‐accelerated coronary MRA image quality approaches that of more conventional nonaccelerated coronary MRA, while scanning time can be reduced considerably. Another powerful approach includes shortening of the ACQ window using SENSE and thus allowing for simultaneous ACQ of the right and left coronary arterial system (27), thereby increasing volumetric coverage at no extra cost in scanning time.…”