Abstract:BackgroundAdvanced cardiovascular magnetic resonance (CMR) acquisitions often require long scan durations that necessitate respiratory navigator gating. The tradeoff of navigator gating is reduced scan efficiency, particularly when the patient’s breathing patterns are inconsistent, as is commonly seen in children. We hypothesized that engaging pediatric participants with a navigator-controlled videogame to help control breathing patterns would improve navigator efficiency and maintain image quality.MethodsWe d… Show more
“…The fidelity of the Heart‐NAV signal could be improved by using an anterior phased array coil element that is closer to the heart to receive the signal and thereby suppress the surrounding static signal . Furthermore, the scan time of 3D cine acquisition can be shortened by using compressed sensing image reconstruction and respiratory biofeedback . Lastly, note that for respiratory gating, cine SSFP data is accepted on a per cardiac cycle basis—if all of the Heart‐NAV signals in a cycle are in the acceptance window, then the cine data from the whole cycle is accepted.…”
“…The fidelity of the Heart‐NAV signal could be improved by using an anterior phased array coil element that is closer to the heart to receive the signal and thereby suppress the surrounding static signal . Furthermore, the scan time of 3D cine acquisition can be shortened by using compressed sensing image reconstruction and respiratory biofeedback . Lastly, note that for respiratory gating, cine SSFP data is accepted on a per cardiac cycle basis—if all of the Heart‐NAV signals in a cycle are in the acceptance window, then the cine data from the whole cycle is accepted.…”
“…Moreover, the acquisitions at the middle acceptance window location were repeated to define inter-test variability when ensuring a consistent position with a respiratory navigator. For all scans, the image of the respiratory navigator was projected to the subjects in real-time during DENSE acquisition, which helped to ensure consistent efficiency [ 21 ] across scans despite varying acceptance locations. Fig.…”
BackgroundLeft ventricular (LV) torsion is an important indicator of cardiac function that is limited by high inter-test variability (50% of the mean value). We hypothesized that this high inter-test variability is partly due to inconsistent breath-hold positions during serial image acquisitions, which could be significantly improved by using a respiratory navigator for cardiovascular magnetic resonance (CMR) based quantification of LV torsion.MethodsWe assessed respiratory-related variability in measured LV torsion with two distinct experimental protocols. First, 17 volunteers were recruited for CMR with cine displacement encoding with stimulated echoes (DENSE) in which a respiratory navigator was used to measure and then enforce variability in end-expiratory position between all LV basal and apical acquisitions. From these data, we quantified the inter-test variability of torsion in the absence and presence of enforced end-expiratory position variability, which established an upper bound for the expected torsion variability. For the second experiment (in 20 new, healthy volunteers), 10 pairs of cine DENSE basal and apical images were each acquired from consecutive breath-holds and consecutive navigator-gated scans (with a single acceptance position). Inter-test variability of torsion was compared between the breath-hold and navigator-gated scans to quantify the variability due to natural breath-hold variation. To demonstrate the importance of these variability reductions, we quantified the reduction in sample size required to detect a clinically meaningful change in LV torsion with the use of a respiratory navigator.ResultsThe mean torsion was 3.4 ± 0.2°/cm. From the first experiment, enforced variability in end-expiratory position translated to considerable variability in measured torsion (0.56 ± 0.34°/cm), whereas inter-test variability with consistent end-expiratory position was 57% lower (0.24 ± 0.16°/cm, p < 0.001). From the second experiment, natural respiratory variability from consecutive breath-holds translated to a variability in torsion of 0.24 ± 0.10°/cm, which was significantly higher than the variability from navigator-gated scans (0.18 ± 0.06°/cm, p = 0.02). By using a respiratory navigator with DENSE, theoretical sample sizes were reduced from 66 to 16 and 26 to 15 as calculated from the two experiments.ConclusionsA substantial portion (22-57%) of the inter-test variability of LV torsion can be reduced by using a respiratory navigator to ensure a consistent breath-hold position between image acquisitions.
“…In one study, almost half of the patients preferred self-determination in breath holding [119]. In held-breath acquisitions, the effectiveness increases when patients, both children and adults, receive visual feedback on their breathing pattern [120]. Additional ways to achieve patient control are to let the patients decide their position on the examination tabletop and how to enter the tunnel.…”
Section: Mri From the Patient Perspectivementioning
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