Niek R.F. Huttinga¹, Osman Akdag¹, Martin Fast¹, Joost Verhoeff¹, Alessandro Sbrizzi¹, and Stefano Mandija^1
1Department of Radiotherapy, Computational Imaging Group for MR therapy & Diagnostics, University Medical Center Utrecht, Utrecht, Netherlands

Accurate tracking of lesions within or near the heart presents a unique challenge due to cardiorespiratory motion during stereotactic radiotherapy. Mitigating this motion is essential to limit the risk of radiation-induced complications. Here, the feasibility of real-time prospective myocardial landmark-tracking with Gaussian Processes from few k-space readouts is demonstrated on the 1.5T Elekta Unity MR-linac. Retrospective and prospective phantom and in-vivo experiments were conducted in 2D, and preliminary in-silico experiments were done to demonstrate the feasibility in 3D. Results indicate high accuracy, and thereby great potential for real-time 3D myocardial target tracking for cardiac radio-ablation. 

Gastao da Cruz¹, René M. Botnar¹, and Claudia Prieto^1
1King's College London, London, United Kingdom

Conventional cardiac CINE imaging acquires segmented data over multiple heartbeats to satisfy sampling requirements. Recently, cardiac CINE reconstructions from a single heartbeat have   been achieved using motion corrected reconstructions. This approach allows single heartbeat CINE and therefore can image the unique dynamics that occur in each heartbeat. Experiments in healthy subjects demonstrate that single heartbeat CINE is feasible and can detect heartbeat to heartbeat variation; the dynamics of individual heartbeats differ and cannot be detected with conventional CINE performed over multiple heartbeats. Single heartbeat CINE shows promise to characterize arrhythmias and other heart conditions where heartrate variability occurs. 

Tobias Wech¹, Julius Frederik Heidenreich¹, Thorsten Alexander Bley¹, and Bettina Baeßler^1
1Department of Diagnostic and Interventional Radiology, University Hospital Würzburg, Würzburg, Germany

The network we propose in this work (xSDNet) jointly reconstructs and segments cardiac functional MR images which were sampled below the Nyquist rate. The model is based on disentangled representation learning and factorizes images into spatial factors and a modality vector. The achieved image quality and the fidelity of the delivered segmentation masks promise a considerable acceleration of both acquisition and data processing.

Irvin Teh¹, David Shelley², Ana-Maria Poenar¹, Erica Dall'Armellina¹, Sven Plein¹, Jürgen E. Schneider¹, and Filip Szczepankiewicz^3
1Leeds Institute of Cardiovascular and Metabolic Medicine, University of Leeds, Leeds, United Kingdom, ²Leeds Teaching Hospitals Trust, Leeds, United Kingdom, ³Clinical Sciences, Lund University, Lund, Sweden

Tensor-valued encoding holds great promise in enhancing specificity in myocardial characterisation relative to diffusion tensor imaging (DTI). However, its application in the heart is challenging due to motion and limited SNR. In this work, we employed optimized diffusion encoding waveforms with up to 2^nd order motion compensation and compensation for concomitant gradient effects to demonstrate the first in vivo application of q-space trajectory imaging (QTI) in the human heart. Baseline myocardial measurements of microscopic fractional anisotropy, as well as isotropic and anisotropic mean kurtosis are reported for the first time in the heart.

Sharon Portnoy¹, Joshua F.P. van Amerom², Amanda Hope³, Datta Singh Goolaub³, Liqun Sun², Mike Seed^2,4, and Christopher K. Macgowan^1,5
1Translational Medicine, Hospital for Sick Children, Toronto, ON, Canada, ²Cardiology, Hospital for Sick Children, Toronto, ON, Canada, ³Hospital for Sick Children, Toronto, ON, Canada, ⁴Diagnostic Imaging, Hospital for Sick Children, Toronto, ON, Canada, ⁵Medical Biophysics, University of Toronto, Toronto, ON, Canada

This work explores the feasibility of 4D fetal whole-heart image reconstruction from high resolution 2D multiplanar radial bSSFP acquisitions. High quality 4D reconstructions (1 mm isotropic spatial resolution, ~20 ms temporal resolution) are demonstrated in 3 congenital heart disease cases with distinct cardiac abnormalities. These dynamic, highly detailed visualizations of the fetal heart facilitate prenatal CHD diagnosis and planning for delivery and surgical intervention.

Changyu Sun¹, Yu Wang¹, and Frederick H. Epstein^1,2
1Biomedical Engineering, University of Virginia, Charlottesville, VA, United States, ²Radiology, University of Virginia, Charlottesville, VA, United States

Multiband (MB) excitation of spiral cine DENSE MRI has the potential to provide three-slice coverage in single breathhold with 2D displacement encoding. To acquire three slices in one breathhold of 14 heartbeats, we develop MB3+ phase modulation, and use golden-angle rotation, outer volume suppression and variable flip angle. We extend our recent Cartesian slice-L+S method to develop a non-Cartesian slice-low-rank reconstruction model. DENSE data with MB=3 were acquired in 4 volunteers. The MB3+ DENSE method shows fewer artifacts than CAIPIRINHA and Hadamard encoding phase modulations. The slice-low-rank method with MB+ significantly improves slice separation providing fewer artifacts and signal decay.

Simone Rumac¹, Christopher W. Roy¹, Jérôme Yerly¹, Mariana B. L. Falcao¹, Aurélien Bustin^1,2,3, Mario Bacher^1,4, Peter Speier⁴, Matthias Stuber^1,5, and Ruud B. van Heeswijk^1
1Department of Radiology, Lausanne University Hospital (CHUV) and University of Lausanne (UNIL), Lausanne, Switzerland, ²IHU LIRYC, Electrophysiology and Heart Modeling Institute, INSERM U1045, Centre de recherche Cardio-Thoracique de Bordeaux, Université de Bordeaux, Bordeaux, France, ³Cardiovascular Imaging, Hôpital Cardiologique du Haut-Lévêque, CHU de Bordeaux, Bordeaux, France, ⁴Siemens Healthcare GmbH, Erlangen, Germany, ⁵CIBM Center for BioMedical Imaging, Lausanne, Switzerland, Lausanne, Switzerland

The most commonly employed T₂ mapping techniques are 2D and make use of ECG-triggering. This may be a limitation in patients with variable heart rate and complex three-dimensional conditions. To address these limitations, we here propose an isotropic free-running 3D T₂ mapping technique that avoids ECG triggering by using Pilot Tone navigation. In three healthy volunteers, our technique produced accurate isotropic T₂ maps when compared to 2D T₂ prepared bSSFP (T₂=41.1±4.8ms vs. 44.9±3.3ms, respectively, p=0.1), and cardiac motion was successfully resolved.

Junyu Wang¹, Ruixi Zhou^1,2, Xitong Wang¹, Marina Awad¹, and Michael Salerno^1,3,4,5
1Biomedical Engineering, University of Virginia, Charlottesville, VA, United States, ²School of Artificial Intelligence, Beijing University of Posts and Telecommunications, Beijing, China, ³Medicine, University of Virginia, Charlottesville, VA, United States, ⁴Radiology, University of Virginia, Charlottesville, VA, United States, ⁵Medicine, Stanford University, Stanford, CA, United States

Cardiac magnetic resonance (CMR) real-time cine, which does not require breath-holding or ECG gating, is clinically useful particularly for patients with impaired breath-hold capacity and/or arrhythmias. Spiral acquisitions, which provide high acquisition efficiency and insensitivity to motion artifacts, can require a long reconstruction time particularly for compressed-sensing or other iterative reconstruction techniques.  As such they cannot provide immediate feedback to the imager. Here, we sought to develop high-resolution real-time cine imaging at 1.5 T using fast spiral acquisitions and deep learning-based rapid imaging reconstruction for both bSSFP and GRE imaging, to make high-quality and online reconstruction for cine imaging feasible.

Tianle Cao^1,2, Nan Wang³, Alan C. Kwan⁴, Hsu-Lei Lee¹, Xianglun Mao¹, Yibin Xie¹, Pei Han^1,2, Hui Han¹, Anthony G. Christodoulou^1,2, and Debiao Li^1,2
1Cedars Sinai Medical Center, Los Angeles, CA, United States, ²University of California, Los Angeles, Los Angeles, CA, United States, ³Radiology Department, Stanford University, Stanford, CA, United States, ⁴Department of Imaging and Cardiology, Cedars Sinai Medical Center, Los Angeles, CA, United States

Myocardium tissue characterization with multi-parametric mapping has gained increased clinical interest. Conventional methods require multiple breath-holding, ECG-triggered scans, which may result in potential image misregistration and patient fatigue. In this work, a free-breathing, non-ECG-triggered approach for simultaneous myocardial T1/T2/T2*/FF (fat-fraction) mapping is presented. Quantitative measurements from the proposed technique agreed with those from single-parameter references.

Sophie M. Peereboom¹ and Sebastian Kozerke^1
1Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland

Spectroscopic imaging could provide insights into regional cardiac triglyceride variations, but scan times are relatively long. In this work metabolite-cycled echo-planar spectroscopic imaging with motion-adapted gating and weighted acquisition is proposed to assess triglyceride-to-water ratios in different regions of the human heart. Results are compared to metabolite-cycled EPSI with conventional acquisition and to single voxel measurements in the interventricular septum. It is shown that scan time can be reduced by more than half to less than 10 minutes as compared to conventional acquisition, while keeping the quality of triglyceride fitting constant.

Jianing Pang¹, Pedro Itriago Leon², Xiaoming Bi³, Gary McNeal¹, Christoph Forman⁴, Christianne Leidecker¹, Maria M Pereyra⁵, and Prakash M Masand^5
1Siemens Medical Solutions USA Inc., Chicago, IL, United States, ²Siemens Medical Solutions USA Inc., Houston, TX, United States, ³Siemens Medical Solutions USA Inc., Los Angeles, CA, United States, ⁴Siemens Healthcare, Erlangen, Germany, ⁵Texas Children's Hospital, Houston, TX, United States

Cardiac cine MRI plays an important role in evaluating cardiac function. The conventional technique, 2D segmented acquisition with retrospective electrocardiogram gating, requires breath-holding and therefore is challenging for many types of patients such as young children. In this work, we report our initial experience of a recently developed free-breathing cardiac cine MRI technique on pediatric patients undergoing routine CMR. Our results showed that the proposed technique, based on compressed sensing real-time imaging and respiratory motion correction, produced comparable quantitative LV measurements and image quality to the reference breath-hold technique in a wide range of patient sizes and ages.

Alexander Fyrdahl¹, Nicole Seiberlich¹, and Jesse Hamilton^1
1Radiology, University of Michigan, Ann Arbor, MI, United States

The ability to reconstruct research images online may facilitate clinical translation and dissemination of new methods. Online implementations of cardiac MRF have been described previously, although they required long reconstruction times due to the need to perform online Bloch equation simulations. In this work, an efficient online 2D cardiac MRF reconstruction pipeline is introduced, capable of displaying myocardial tissue property maps in less than a minute.