Automatic Extraction and Sign Determination of Respiratory Signal in Real-time Cardiac Magnetic Resonance imaging

In real-time (RT) cardiac cine imaging, a stack of 2D slices is collected sequentially under free-breathing conditions. A complete heartbeat from each slice is then used for cardiac function quantification. The inter-slice respiratory mismatch can compromise accurate quantification of cardiac function. Methods based on principal components analysis (PCA) have been proposed to extract the respiratory signal from RT cardiac cine, but these methods cannot resolve the inter-slice sign ambiguity of the respiratory signal. In this work, we propose a fully automatic sign correction procedure based on the similarity of neighboring slices and correlation to the center-of-mass curve. The proposed method is evaluated in eleven volunteers, with ten slices per volunteer. The motion in a manually selected region-of-interest (ROI) is used as a reference. The results show that the extracted respiratory signal has a high, positive correlation with the reference in all cases. The qualitative assessment of images also shows that the proposed approach can accurately identify heartbeats, one from each slice, belonging to the same respiratory phase. This approach can improve cardiac function quantification for RT cine without manual intervention.Comment: IEEE ISBI 2020, International Symposium on Biomedical Imagin

1110 Improved real-time cine with the use of a 32-channel cardiac array and Karhunen-Loeve Transform filter

This is the author accepted manuscript. The final version is available from SAGE Publications via the DOI in this record.Leader-member exchange (LMX) theory proposes that leaders develop different quality relationships with those they manage and this is predictive of work performance. While LMX quality has been viewed as univalent (ranging from low to high quality), this paper proposes that it can also be bivalent in nature (i.e., coexisting positive and negative thoughts towards the relationship), which we refer to as LMX ambivalence. A survey measure of LMX ambivalence is developed, and through three validation and two main studies, it is shown to have construct, discriminant, and incremental predictive validity beyond that of LMX quality. Hypotheses concerning LMX ambivalence and task performance are tested in two main studies and show that (1) LMX ambivalence is negatively related to performance regardless of LMX quality, (2) high levels of perceived support from the organization (Study 1) or coworkers (Study 2) nullify the negative association between LMX ambivalence and performance, and (3) high LMX ambivalence leads to more negative affect and in turn lower task performance, but only when coworker support is low (Study 2). These results show the importance of viewing LMX quality not only in terms of its absolute level (low vs. high quality) but also as a bivalent construct where both positive and negative cognitions can coexist. They also demonstrate the value of social support in buffering the negative effects of LMX ambivalence. Furthermore, our findings extend a central tenet of LMX theory by implying that LMX quality varies not only within groups (i.e., LMX differentiation) but also within leader-follower dyads

Rapid phase-modulated water excitation steady-state free precession for fat suppressed cine cardiovascular MR

<p>Abstract</p> <p>Background</p> <p>The purpose of this article is to describe a steady-state free precession (SSFP) sequence for fat-suppressed cine cardiovascular magnetic resonance (CMR). A rapid phase-modulated binomial water-excitation (WE) pulse is utilized to minimize repetition time and acquisition time.</p> <p>Methods</p> <p>Three different water-excitation pulses were combined with cine-SSFP for evaluation. The frequency response of each sequence was simulated and examined in phantom imaging studies. The ratio of fat to water signal amplitude was measured in phantoms to evaluate the fat-suppression capabilities of each method. Six volunteers underwent CMR of the heart at 1.5T to compare retrospectively-gated cine-SSFP with and without water-excitation. The ratio of fat to myocardium signal amplitude was measured for conventional cine-SSFP and phase-modulated WE-SSFP. The proposed WE-SSFP method was tested in one patient referred for CMR to characterize a cardiac mass.</p> <p>Results and discussion</p> <p>The measured frequency response in a phantom corresponded to the numerical Bloch equation simulation demonstrating the widened stop-band around the fat resonant frequency for all water-excitation pulses tested. <it>In vivo </it>measurements demonstrated that a rapid, phase-modulated water-excitation pulse significantly reduced the signal amplitude ratio of fat to myocardium from 6.92 ± 2.9 to 0.8 ± 0.13 (mean ± SD) without inducing any perceptible artifacts in SSFP cine CMR.</p> <p>Conclusion</p> <p>fat-suppression can be achieved in SSFP cine CMR while maintaining steady-state equilibrium using rapid, phase modulated, binomial water-excitation pulses.</p