Short breath‐hold, volumetric coronary MR angiography employing steady‐state free precession in conjunction with parallel imaging

Abstract

An ECG-gated, 3D steady-state free precession (SSFP) technique in conjunction with sensitivity encoding (SENSE)-based parallel imaging was implemented for short breath-hold, volumetric coronary MR angiograpy (CMRA). Two parallel imaging acquisition strategies (employing 1 R-R and 2 R-R intervals, respectively) were developed to achieve 1) very short breathhold times (12 s for a heart rate of 60 bpm), and 2) small acquisition windows to minimize sensitivity to physiologic motion. Both strategies were examined in CMRA applications over a range of heart rates. A four-point scale blinded reading (with 4 indicating the most desirable features) revealed substantial image quality improvements for the accelerated data as compared to the nonaccelerated approach. The 1 R-R interval scheme yielded an image score of 3.39 ؎ 0.60, and was found to be particularly suitable for low heart rates (P ‫؍‬ 0.0008). The 2 R-R interval strategy yielded an image score of 3.35 ؎ 0.64, and was more appropriate for higher heart rates (P ‫؍‬ 0.03). The results demonstrate that 3D SSFP combined with parallel imaging is a versatile method for short breath-hold CMRA while maintaining high spatial resolution. This strategy permits imaging of the major coronary artery distributions in two to three breath-holds using targeted slabs, and offers the potential for Coronary magnetic resonance angiography (CMRA) has been proven to be of clinical value for assessing congenital coronary artery anomalies (1,2), and its potential for noninvasivelydetectingcoronaryarterydiseasehasbeendemonstrated (3,4). However, routine clinical CMRA remains technically challenging due to small vessel size, adjacent fat, and myocardium and vessel tortuosity (5). Furthermore, respiratory and cardiac motion can degrade image quality, particularly when motion suppression techniques are unavailable, unsuccessful, or not utilized.Various approaches have been proposed to minimize artifacts from respiratory and cardiac motion. Cardiac motion has been effectively dealt with by electrocardiograph (ECG) gating and by restricting the data acquisition period to the mid-diastolic phase, during which heart motion is minimal. Respiratory motion has been addressed with the use of two main strategies: 1) free breathing using navigator-echo-based respiratory gating (6 -15), and 2) breathhold techniques (16 -20). Navigated techniques are often combined with 3D acquisition methods, resulting in average scan times of 8 -13 min (4,12,14). However, long scan times are associated with diaphragmatic drift, a phenomenon that can inadvertently diminish navigator efficiency (8). With reduced navigator efficiency, further degradation in image quality may result as scan times can lengthen toward a 30-min acquisition (4). Although one can improve the diminished navigator efficiency by increasing the acceptance window or readjusting the navigator volume, average scan times of up to 49 Ϯ 19 min have been reported for imaging both the right and left coronary arteries (4). Consequently, navigator techniques...

Comparison of left ventricular function assessment using phonocardiogram- and electrocardiogram-triggered 2D SSFP CINE MR imaging at 1.5 T and 3.0 T

“…LV function assessment requires speed and synchronization of data acquisition with the cardiac cycle to avoid artefacts due to cardiac motion and flow constraints that dictate the viable window for data acquisition [3][4][5][6][7][8][9]. In current clinical MR, cardiac motion is commonly dealt with using finger pulse oximetry [10] or electrocardiography (ECG) triggering/gating techniques [10][11][12] to synchronize data acquisition with the cardiac cycle.…”

Highly accelerated cardiovascular MR imaging using many channel technology: concepts and clinical applications

“…The time savings of accelerated CMRA have been translated into enhanced spatial resolution, which resulted in improved delineation of proximal and, most especially, distal segments of the coronary arteries [70].…”

Toward single breath‐hold whole‐heart coverage coronary MRA using highly accelerated parallel imaging with a 32‐channel MR system

“…For each slice partition the data acquisition consisted of two non-equal temporal segments that were placed at the same cardiac phase of two consecutive cardiac cycles. By acquiring the low-spatial-frequency data in a more compact acquisition window than the high-spatial-frequency k-space lines for each slice partition, cardiac motion-related blurring was reduced compared to the standard symmetric approach (28).…”

“…For each slice partition, data acquisition for all k y phase-encoding steps was completed in a single R-R interval before the k z index was incremented (28).…”

“…Data acquisition was completed in a single heartbeat for a given slice phase-encoding step before the k z index was incremented. This transition from 2 R-R to 1 R-R k y -segmentation for each slice partition enabled us to acquire larger volumes by doubling the number of slices without increasing the breath-hold time as compared to the 2 R-R interval strategy (28).…”