Preclinical Evaluation of an MR-EP Suite Including an MR-EP Navigator and Dedicated MR-EP Catheters
Sascha Krueger¹, Ronald Holthuizen², Jouke Smink², Steffen Weiss¹, Oliver Lips¹, Bernd David¹, Daniel Wirtz¹, Steen Fjord Pedersen³, Dennis Caulfield⁴, Julian Bostock⁴, Gang Gao⁴, Phani Chinchapatnam⁴, Tobias Schaeffter⁴, Reza Razavi^4
1Philips Research Europe, Hamburg, Germany; ²Philips Healthcare, Best, Netherlands; ³MR Research Centre, Skejby Hospital, Aarhus, Denmark; ⁴Division of Imaging Sciences, King's College, London, United Kingdom

Cardiac arrhythmias, e.g. atrial fibrillation and ventricular tachycardia, are increasingly treated by electrophysiological (EP) interventions. Applying MR for guiding these interventions offers advantages like 3D visualization of the cardiac soft tissue in relation to the catheter, visualization of the treatment effect and absence of ionizing radiation. Making the step towards clinical MR-guided EP interventions requires a focus on RF safety of the devices, localization accuracy of the catheters, guidance of the procedure, intra-cardiac signal quality and procedure workflow. Here, an MR-EP suite based on an MR-EP Navigator application with a real-time interface to the MR system and therapy equipment is demonstrated along with specialized MR-EP catheters. These catheters are based on RF-safe concepts for both, MR- and EP functionality. RF-safety, localization accuracy and EP signal quality of these devices, and the operation of the MR-EP suite and the workflow of the MR-EP Navigator are demonstrated in a series of pre-clinical MR-guided EP experiments.

Visualizing RF Ablation Lesions Real-Time at 3Tesla
Sathya Vijayakumar^1,2, Eugene G. Kholmovski¹, Gene Payne¹, Joshua Blauer³, Christopher Gloschat³, Jayne H. Davis⁴, Rob MacLeod^3,4, Kimberly Lilbok⁵, Gaston Vergara⁵, Mike Guttman⁶, Kamal Vij⁶, Chris J. McGann^2,7, Dennis L. Parker¹, Nassir F. Marrouche^5
1UCAIR, Department of Radiology, University of Utah, Salt Lake City, UT, United States; ²CARMA Center, University of Utah, Salt Lake City, UT, United States; ³Dept. of Biomedical Engineering, University of Utah, Salt Lake City, UT, United States; ⁴CVRTI, University of Utah, Salt Lake City, UT, United States; ⁵Dept. of Cardiology, University of Utah, Salt Lake City, UT, United States; ⁶Surgivision Inc,, Irvine, CA, United States; ⁷Drpt. of Cardiology, University of Utah, Salt Lake City, UT, United States

In this work, we present the real-time imaging of lesions as they form on a porcine model.

MRI-Compatible 12-Lead ECGs with MHD Separation: Application to Cardiac MRI Gating, Physiological Monitoring and Non-Invasive Cardiac-Output Estimation
Zion Tsz Ho Tse¹, Charles L. Dumoulin², Gari Clifford³, Michael Jerosch-Herold¹, Daniel Kacher¹, Raymond Kwong⁴, William Gregory Stevenson⁴, Ehud Jeruham Schmidt^1
1Radiology, Brigham and Women's Hospital, Boston, MA, United States; ²University of Cincinnati College of Medicine, Cincinnati, OH, United States; ³Health Sciences and Technology, Massachusetts Institute of Technology, Boston, MA, United States; ⁴Cardiology, Brigham and Women's Hospital, Boston, MA, United States

An adaptive filtering procedure, based on a set of ECG measurements performed outside and inside the MRI, is presented in order to separate between the real ECG and Magneto-HydroDynamic (MHD) signals in 12-lead ECGs acquired within a 1.5T MRI. The cleaned ECG improves cardiac gating and preserves S-T segment fidelity for physiological monitoring. The integrated MHD magneto-hydrodynamic signals provide non-invasive beat-to-beat cardiac output estimations. The proposed method was validated in five normal healthy subjects, including an athlete exercising inside the magnet, and a patient with frequent Premature Ventricle Contractions.

RF-Safe, Multi-Polar, Diagnostic MR-EP Catheter Employing Resistive Leads and a Transformer-Based Transmission Line
Daniel Wirtz¹, Bernd David¹, Steffen Weiss¹, Sascha Krueger¹, Oliver Lips^1
1Imaging Systems & Intervention, Philips Research Europe - Hamburg, Hamburg, Germany

RF heating of a diagnostic multi-polar EP mapping-catheter equipped with resistive leads for ECG signal transmission was investigated by electromagnetic simulations and subsequent measurements. The influence of wire resistance and number of wires in the catheter has been adressed. The simulations were validated by fiberoptic temperature measurements on a prototype catheter employing resistive leads.
Furthermore, the effect of a transformer-based transmission line connected to a tracking coil on RF heating at the catheter tip, the ring electrodes and near the tracking coil was analyzed. Favourable distributions of the transformers along the safe transmission line resulting in minimum SAR were derived.

Roadmaps Incorporating Respiratory and Cardiac Motion for X-Ray Fused with MRI
Anthony Zahi Faranesh¹, Peter Kellman¹, Robert J. Lederman^1
1Division of Intramural Research, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, MD, United States

X-ray fused with MRI provides 3D roadmaps for x-ray cardiovascular interventional procedures.  This work incorporates respiratory and cardiac motion into the roadmaps to enhance image guidance.  Cardiac and respiratory motion is measured from real-time MRI images and then fit to an affine model.  Separate models are used for individual anatomic structures, to accommodate complex regional motion.  The 3D roadmaps are then deformed based on cardiac and respiratory phase to better reflect physiological motion during the procedure.

Feasibility of MR-Thermometry with Blood Suppression on the Human Heart at 3T
Silke Hey¹, Alexandru Cernicanu², Baudouin Denis de Senneville¹, Sebastien Roujol¹, Mario Ries¹, Chrit T. W. Moonen¹, Bruno Quesson^1
1Laboratory for Molecular and Functional Imaging, Bordeaux, France; ²Philips Healthcare, France

Ventricular tachycardia and atrial fibrillation can be treated by catheter radio-frequency ablation where PRFS-based MR thermometry is a candidate to provide intra-procedural feedback.  However, MR thermometry of the heart is challenging. As blood suppression is preferable to avoid artifacts in the myocardium, we explore three different options, namely double inversion recovery (DIR), motion-sensitized driven equilibrium (MSDE), and inflow saturation (IS). The effectiveness of the blood suppression and its effect on the temperature stability in the septum is evaluated in eight healthy volunteers for 50s of free-breathing using VCG cardiac triggering and navigator respiratory compensation.

Direct MRI-Guided Needle Access to the Heart and Blood Vessels
Christina E. Saikus¹, Kanishka Ratnayaka^1,2, Israel M. Barbash¹, Ozgur Kocaturk¹, Anthony Z. Faranesh¹, Robert J. Lederman^1
1Translational Medicine Branch, Division of Intramural Research, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, MD, United States; ²Cardiology Division, Children's National Medical Center, Washington DC, United States

Inherent soft-tissue contrast and multi-planar imaging of MRI without ionizing radiation makes it appealing for guidance of traditional and complex cardiovascular access.  In this work, we have utilized real-time MRI to guide peripheral vascular access in addition to more precise targeting of direct cardiac access to the right ventricle in swine.  MR imaging with compatible devices provides valuable anatomical information to the operator and enables trajectory planning and procedure monitoring to ensure a safe and efficient entry to the heart and vasculature.

Catheter Tracking Using Transmit Array System
Haydar Celik^1,2, Ibrahim Davut Mahcicek², Ergin Atalar^2,3
1Electrical and Electronics Engineering, Bilkent University , Ankara, Turkey; ²National Magnetic Resonance Research Center (UMRAM), Ankara, Turkey; ³Electrical and Electronics Engineering, Bilkent University, Ankara, Turkey

Although, soft tissue contrast of MRI is effectively high, visualization of the internal devices, such as guidewires and catheters, is not straight forward. In order to achieve better identification of these devices, various tracking techniques have been developed. Passive tracking methods are easy to implement, but they are not sufficiently reliable. The main problem of active tracking techniques is uneasy device handlings. They need to be connected to imager with cables. In addition, these cables create safety problems. There are also hybrid methods, using inductively coupled RF (ICRF) and receive coupled RF (RCRF) coils. In our study, we propose a new method using ICRF coils and transmit array system. Presented method enables simultaneous acquisition of anatomy and catheter images.

Excite by Light: A Novel MR-Safe Method of Catheter Tip Tracking
Reiner Umathum¹, Axel Joachim Krafft¹, Michael Bock^1
1German Cancer Research Center, Heidelberg, Germany

A novel method for MR-safe catheter tip tracking was investigated. RF-modulated light is converted into a current at the tip of an interventional catheter driving a small resonant circuit tuned to the 1H resonance frequency and exciting a small liquid reservoir locally. The generated MR signal is read out with conventional MR imaging coils so that the catheter tip can be effectively visualized against a dark signal background.

Prospective Motion Correction Using an MR-Tracking Tetrahedron for Intra-Cavitary MRI
Lei Qin¹, Ehud J. Schmidt¹, W. Scott Hoge¹, Juan Santos², Clare Tempany-Afdhal¹, Kim Butts-Pauly³, Charles L. Dumoulin^4
1Radiology, Harvard Medical School, Boston, MA, United States; ²Electrical Engineering, Stanford University, Stanford, CA, United States; ³Radiology, Stanford University, Stanford, CA, United States; ⁴Radiology, Cincinnati Children's Hospital, Cincinnati, OH, United States

Intra-cavitary imaging coils have been developed to achieve higher spatial resolution. However, they suffer more severely from motion artifacts since both the anatomy and the coil are moving while image acquisition occurs. We propose integrating a Tetrahedron-shaped active MR-tracking coil into an intra-cavitary imaging coil for motion detection, and to perform prospective motion (rotation and translation) corrections in real-time, so that the entire image can be acquired in a “static” frame of reference. Experiments show significant image quality improvements for both in-plane and through-plane motion correction.