Electronic poster

Thermotherapy

Hall B Monday 14:30-16:00 Computer 65

14:30 4136. Interleaved Slice Excitation for Echo-Shifted Acquisition of Orthogonal Proton Resonance Frequency Temperature Images

Axel Joachim Krafft¹, Jaane Rauschenberg¹, Florian Maier¹, Jürgen Walter Jenne^2,3, Wolfhard Semmler¹, Michael Bock<sup>1

1</sup>Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany; ²Mediri GmbH, Heidelberg, Germany; ³Clinical Cooperation Unit Radiation Oncology, German Cancer Research Center (DKFZ), Heidelberg, Germany

Proton resonance frequency temperature images are acquired with gradient echo techniques. As the temperature induced frequency shift is very small, long echo times have to be used. In such long-TE gradient echo pulse sequences, the available time for application of the encoding gradients between RF excitation and data readout is only partly used. In this work, we present a novel interleaved excitation and readout technique for the acquisition of two orthogonal slices. Compared to conventional gradient echo techniques, this strategy is substantially more time-efficient and allows for temperature monitoring along all three spatial directions around the temperature focus.

15:30 4137. In Vivo Evaluation of MRgHIFU Volumetric Sonication Using Interleaved Electronic-And-Mechanical Displacement of Focus

Lorena Petrusca^1,2, Jacqueline Ngo¹, Vincent Auboiroux^1,2, Francois Cotton, ²³, Jean-Yves Chapelon¹, Rares Salomir<sup>1

1</sup>Inserm U 556, Lyon, France; ²University Lyon 1, Lyon, France; ³CHU Lyon Sud

Phased-array HIFU transducer under MR-guidance can bring important improvements in actual clinical strategy for prostate cancer treatment. The performances of a MR-compatible transrectal HIFU device with 16 circular rings were in vivo investigated on rabbit thigh. Dual-mode displacements of the focus was performed: electronically, along the ultrasound propagation axis and mechanically XZ 2D-translations and rotation around B0. Online fast MR-thermometry in 2 orthogonal planes, MRI assessment 5 days after the treatment and the histological analyze showed that a homogenous lesion was induced in the predefined zone. Dual-mode sonication paradigm offer the possibility to induce the lesion desired shape in a reasonable time period, and minimizing the side-effects.

Tuesday 13:30-15:30 Computer 65

13:30 4138. Experimental Comparison Ex Vivo of Different Sonication Patterns for Volumetric MRgHIFU Ablation

Lorena Petrusca¹, Thomas Goget¹, Magalie Viallon¹, Loredana Baboi¹, Christoph Becker¹, Rares Salomir<sup>1

1</sup>Geneva University Hospital, Geneva, Switzerland

Different sonication patterns (i.e. trajectories of the focus) were performed ex-vivo with a phased-array transducer: lines, unitary circles and concentric circles of different lengths/diameters for comparison purpose. The temperature profile along the ultrasound propagation axis was analyzed. For the same value of the line length and circle diameter and identical applied powers and durations of sonication, a significant drift of the maximum heating location below the treatment plane towards the transducer was noticed for circle or disk trajectories. Line scan sonications up to 24mm size provided symmetric and drift-free thermal build up. The latter pattern should be considered for fast and safe volumetric ablation with MRgHIFU.

14:00 4139. inter-Costal Liver Ablation Under Real-Time MR-Thermometry with Partial Activation of a HIFU Phased Array Transducer

Bruno Quesson¹, Mathilde Merle¹, Max Köhler², Charles Mougenot³, Sebastien Roujol¹, Baudouin Denis de Senneville¹, Chrit T. Moonen<sup>1

1</sup>laboratory for molecular and functional imaging, bordeaux, France; ²Philips healthcare, Vantaa, Finland; ³Philips Healthcare, bordeaux, France

The partial obstruction of the High Intensity Focused Ultrasound beam by the rib cage complicates the treatment of liver tumors. A method for selective deactivation of the transducer elements located in front of the ribs (visualized on 3D anatomical MR images) is proposed. The effectiveness of the method for HIFU liver ablations is demonstrated ex vivo and in vivo in pigs during breathing with real-time, motion compensated, MR thermometry. No loss in heating efficacy was observed at the focal point and an important reduction of the heating in tissues surrounding the bones was obtained with deactivation of the transducer elements.

14:30 4140. Multi-Parametric Monitoring of Thermal Ablations Using Rapid Chemical Shift Imaging

Brian Allen Taylor^1,2, Andrew M. Elliott¹, Ken-Pin Hwang, ^1,3, John D. Hazle¹, Roger Jason Stafford<sup>1

1</sup>Imaging Physics, The University of Texas MD Anderson Cancer Center, Houston, TX, United States; ²The University of Texas Graduate School of Biomedical Sciences, Houston, TX, United States; ³Applied Science Laboratory, GE Healthcare, Waukesha, WI, United States

A rapid chemical shift imaging technique is presented that provides T2* values and T1-W amplitudes of multiple chemical species in addition to accurate and precise temperature estimates. Temperature response of each parameter is correlated with Arrhenius rate analysis to determine if measurements can aid in verifying treatment goals.

15:00 4141. Real-Time Bioheat Transfer Models for Computer Driven MR Guided LITT

David Fuentes¹, Yusheng Feng², Andrew Elliott¹, Anil Shetty¹, Roger McNichols³, J Tinsley Oden⁴, R Jason Stafford<sup>1

1</sup>Imaging Physics, The University of Texas MD Anderson Cancer Center, Houston, TX, United States; ²The University of Texas at San Antonio; ³BioTex Inc; ⁴ICES, The University of Texas at Austin

Treatment times of computationally assisted MR guided LITT are determined by the convergence behavior of PDE constrained optimization problems. This work investigates the feasibility of applying real-time bioheat transfer constrained model calibration to patient specific data and rigorously validates model calibrations against MR temperature imaging data. The calibration techniques attempt to adaptively recover the patient specific bio-thermal heterogeneities within the tissue and result in a formidable real time PDE constrained optimization problem. The calibrations are critical to the predictive power of the simulation during therapy which may be further exploited for treatment optimization to maximize the efficiency of the therapy control loop.

Wednesday 13:30-15:30 Computer 65

13:30 4142. MR-Guided Trans-Perineal Cryoablation of Locally Recurrent Prostate Adenocarcinoma Following Radical Prostatectomy

David Arthur Woodrum¹, Lance Mynderse², Akira Kawashima¹, Krzysztof Gorny¹, Thomas Atwell¹, Fred Mcphail², Bradley Bolster³, Wesley Gilson³, Kimberly Amrami¹, Haraldur Bjarnason¹, Matthew Callstrom<sup>1

1</sup>Radiology, Mayo Clinic, Rochester, MN, United States; ²Urology, Mayo Clinic, Rochester, MN, United States; ³Siemens Medical Solutions, Inc.

Prostate cancer recurrence after definitive therapy can be as high as 25% after 15 years. Detection of these recurrences can be achieved using serial PSA coupled with dynamic contrast enhanced (DCE) MRI. Our hypothesis is MR-guided cryoablation can be used in the setting of prostate bed PAC recurrence to perform a precise image-guided focal ablation. Two patients with prior RRP and dynamic contrast enhancement(DCE) MRI abnormalities in the prostate bed were treated using MR-guided cryoablation. Both patients with recurrent prostate cancer in the prostate bed were successfully treated with MR-guided cryoablation. Immediate post-ablation DCE MRI demonstrated no definite residual tumor.

14:00 4143. Truly Simultaneous Clinical US/MRI: Dual Mode Visualization of Bubble Creation During RFA Inducing Susceptibility Variations Corrupting PRFS Thermometry

Magalie Viallon¹, Joerg Roland², Sylvain Terraz¹, Christoph D Becker¹, Rares salomir<sup>1

1</sup>Radiologie, Hopital Universitaire de Genève, Geneva, Switzerland; ²MREA, Siemens Medical Solutions, Erlangen, Germany

Recent work reported spatially related errors in temperature maps and TD during power application, while using 2D GRE-EPI PRFS imaging with orthogonal interleaved slices (1). We demonstrate that RFA induced cavitation’s effects are the primary source of errors in PRFS imaging using truly simultaneous ultrasonography and MRI.

14:30 4144. TMAP @ IFE - A Framework for Guiding and Monitoring Thermal Ablations

Eva Rothgang^1,2, Wesley David Gilson², Joerg Roland³, Joachim Hornegger¹, Christine H. Lorenz<sup>2

1</sup>Pattern Recognition Lab, Department of Computer Science, University of Erlangen-Nuremberg, Erlangen, Germany; ²Center for Applied Medical Imaging, Siemens Corporation, Corporate Research, Baltimore, MD, United States; ³Siemens Healthcare, Erlangen, Germany

Thermal ablations are increasingly used for minimally invasive local treatment of solid malignancies, supplementing systemic treatment strategies such as chemotherapy and immunotherapy. We present an intuitive application for monitoring thermal treatment independent of heating source, in real-time, with multiplanar MRI. Systematic quality control of thermal maps is carried out on-line to ensure reliability of the displayed thermal data. The application is fully integrated into the Interactive Front End (IFE) which allows real-time MRI-guided placement of the heating device. Thus, the presented application supports the thermal ablation workflow from placing the ablation device to online monitoring the progress of ablation.

15:00 4145. Imitation of Radiofrequency Ablation Scars with Laser System for MR Guided Ablation of Atrial Fibrillation

Can Kerse^1,2, Bulent Oktem³, Fatih Omer Ilday⁴, Ergin Atalar, <sup>2,5

1</sup>Department of Electrical and Electronics Engineering , Bilkent University, Ankara, Turkey; ²UMRAM (National Research Center for Magnetic Resonance), Ankara, Turkey; ³Material Science and Nanotechnology Graduate Program, Bilkent University, Ankara, Turkey; ⁴Physics Department, Bilkent University, Ankara, Turkey; ⁵Department of Electrical and Electronics Engineering, Bilkent University, Ankara, Turkey

Fiber delivery of laser energy has no MR compatibility issues and is used with MR guidance in the field. But, it is not widely used as the cure of Atrial Fibrillation, since there is risk of perforating the myocardial wall. Several diffusing tip designs to emit light in cylindrical symmetry exist, but, due to their orientation with respect to the cardiac chamber, common RF delivery methods cannot be applied directly. In our study, we propose a novel multiple fiber laser energy delivery with catheter approach and a system that imitates the scars created with RF probes under MR guidance.

Thursday 13:30-15:30 Computer 65

13:30 4146. Feasibility of Multipolar Radiofrequency Ablation in the Pig Liver Under Simultaneous Real-Time MR Thermometry

Matthieu Lepetit-Coiffe¹, Alexandru Cernicanu², Olivier Seror, ^1,3, Thomas Stein⁴, Yasmina Berber¹, Mario Ries¹, Chrit T. Moonen¹, Bruno Quesson<sup>1

1</sup>Laboratoire IMF CNRS UMR 5231 / Universite Bordeaux 2, Bordeaux, France; ²Philips Healthcare, Suresnes, France; ³Service de Radiologie, Hopital Jean Verdier, Bondy, France; ⁴Celon/Olympus, Teltow, Germany

The feasibility of real-time MR thermometry for monitoring multipolar RF ablation was demonstrated both ex vivo and in vivo on a pig liver. The quality of the real-time thermal dose maps appeared satisfactory in the presence of respiratory motion and cyclic switching between the different pairs of RF electrodes. The large (about 250 cm3) resulting thermal coagulation volume was spatially homogeneous as predicted by the real-time lethal thermal dose maps and confirmed by the post procedural MR imaging and histology.

14:00 4147. Breath Hold Phase Correction for Water-Fat Separated MR Thermometry Using B0 Field Changes

Cory Robert Wyatt¹, Brian J. Soher², James R. MacFall<sup>2

1</sup>Department of Biomedical Engineering, Duke University, Durham, NC, United States; ²Department of Radiology, Duke University Medical Center, Durham, NC, United States

Proton resonance frequency shift (PRFS) thermometry of the breast is often confounded not only by the presence of fat in the tissue but also by respiration-induced B0 changes even in the absence of detectable breast motion. In this work, field fitting techniques used previously are used to extrapolate fat referenced B0 changes measured using fat-water separation methods to B0 changes in a water-only simulated tumor in a fat-water breast phantom. Results show that the B0 map extrapolation method reduces PRFS temperature errors between breath holds from a maximum of 5.55°C to less than 0.53°C.

14:30 4148. Real-Time Non Subtraction Thermometry Using Artificial Neural Networks

Manivannan Jayapalan<sup>1

1</sup>MR SW & Applications Engg, GE Healthcare, Bangalore, Karnataka, India

Thermal monitoring in focused ultrasound applications is crucial step where MR is most widely used as it provides better thermal monitoring capability than others. Regular PRF shift technique involves, some form of image subtraction using a baseline pre-treatment images. Subject motion and tissue deformation due to coagulation can severely distort these techniques. Self-referenced methods require a large area of tissue around the ablation for polynomial fitting and can’t be used when tissue cooling is applied to sensitive structures. Here a new method of thermal monitoring using Radial Basis Function Neural Network (RBFNN) trained by orthogonal least square algorithm is proposed. This method eliminates the need for baseline subtraction and also tolerates subject motion to a great extent. A feed forward, radial basis neural network is used with 2 input, 1 output and a hidden layer where the number of units in that layer is obtained using orthogonal least square algorithm learning method. Gaussian function is used as kernel whose centers are obtained through network learning. 2-D surface co-ordinates of phase image in a selected ROI is used as inputs while its corresponding phase value are used as output to train the network. Then the network is tested, where, the phase values obtained from the network and the actual values are compared. It was observed that the network output matches very well with the actual values which clearly proves that the neural networks approximates the phase distribution function very well.

15:00 4149. 3D Reduced-FOV MR Thermometry with Fat Suppression Using a Hybrid Method Combining a 2DRF Pulse, Parallel Imaging, and UNFOLD

Chang-Sheng Mei^1,2, Jing Yuan³, Lawrence P. Panych⁴, Bruno Madore⁴, Nathan J. McDannold<sup>4

1</sup>Department of Physics, Boston College, Chesnut Hill, MA, United States; ²Department of Radiology, Brigham and Women's Hospital,, Harvard Medical School, Boston, MA, United States; ³Department of Diagnostic Radiology and Organ Imaging, Chinese University of Hong Kong, Shatin, Hong Kong; ⁴Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, United States

3D MR thermometry using PRF shift has issues due to the requirement of relatively long TE and the presence of fat. A hybrid method combining 2DRF pulse, parallel imaging, and UNFOLD in a 3D sequence is proposed here, which offers advantages in terms of spatial coverage and measurement accuracy, as compared to typically-used 2D sequences.

Cardiovascular Interventional & Devices

Hall B Monday 14:00-16:00 Computer 66

14:00 4150. Mr Guided Transmyocardial Delivery of Hepatocyte Growth Factor Gene Into Infarct Scar with Established Remodelled Left Ventricle

Maythem Saeed¹, David Saloner¹, Phillip Ursell², Loi Do¹, Mark Wilson¹, Alastair J. Martin<sup>1

1</sup>Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, Ca, United States; ²Pathology, University of California San Francisco, San Francisco, Ca, United States

It is unknown whether MR-guided transendocardial delivery of hepatocyte growth factor gene (HGF) is effective in ameliorating LV remodelling. XMR suite (x-ray cath-lab and a 1.5T MR scanner) for real-time imaging, transendocardial delivery and assessing the gene effects in swine with remodelled LV. Six MR sequences were used for evaluation of the efficacy of therapy. MR-guided transendocardial delivery of HGF a) ameliorated global function and 3D strain, b) activated perfusion, neovascularization and myogenesis in scar and c) reduced infarct. The combination of this therapy and XMR technique may be useful in patients with ischemic myocardium and cell loss (apoptosis).

14:30 4151. Visualization of Ablation Lesions by Dynamic Contrast Enhanced MRI

Andriy Shmatukha¹, Bharathi Sundaram², Xiuling Qi², Samuel Oduneye², Jeff A. Stainsby¹, Graham A. Wright², Eugene Crystal<sup>2

1</sup>Applied Science Laboratory, GE Healthcare, Toronto, Ontario, Canada; ²Sunnybrook Health Sciences Centre, Canada

An approach for rapid and reliable visualization of radiofrequency (RF) ablation lesions using dynamic contrast enhanced MRI is presented. Novel processing algorithms are presented that demonstrate the ability to identify distinct regions within RF lesions and can do so more rapidly than traditional dynamic contrast enhanced processing methods.

15:00 4152. An Approach for MRI Based Pre-Operative Planning of Cardiac Interventions Via Trans-Apical Access

Erol Yeniaras¹, Nikhil Navkar¹, Zhigang Deng¹, Mushabbar A. Syed², Nikolaos V. Tsekos<sup>1

1</sup>Computer Science, University fo Houston, Houston, TX, United States; ²Division of Cardiovascular Medicine, University of Kentucky, United States

The aim of this work is to implement an approach for pre-operative planning of cardiac interventions via a trans-apical access using CINE cardiac images. Multislice sets of short and long axis planes were analyzed to identify access corridors in 3D, from the apex to the base of the heart, which ensure that a tool may transverse the ventricle without contact to the epicardial wall for all heart phases. Studies illustrate that apical areas can be delineated through which a tool may be inserted to access the mitral valve along a straight path and the aortic valve through a curved one.

15:30 4153. MR-Guided Electrophysiology System for Activation and Pace Mapping in Left Ventricle

Samuel O. Oduneye¹, Andriy Shmatukha², Vladimir Verpakhovski³, Charles L. Dumoulin⁴, Ehud Schmidt⁵, Eugene Crystal⁶, Graham A. Wright<sup>1

1</sup>Medical Biophysics, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, Canada; ²GE Healthcare, Toronto, Ontario, Canada; ³Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada; ⁴GE Global Research Center, Niskayuna, NY, United States; ⁵Brigham and Women's Hospital & Massachusetts General Hospital, Boston, MA, United States; ⁶Arrhythmia Services, Sunnybrook Health Sciences Centre, Toronto, Canada

In recent studies, electrophysiology information has been compared with pre-acquired MR images to determine the relation between the two measurements; however, that approach is sensitive to registration errors and changes in anatomical conditions. Here, we present an MR-compatible EP system for real-time MR imaging able to directly locate and characterize electrical properties of potential arrhythmogenic regions in the left ventricle (LV) by measuring local conduction velocities at different pacing frequencies.

Tuesday 13:30-15:30 Computer 66

13:30 4154. An Active Delivery Cable for VSD Closure Under MRI-Guidance

Jamie A. Bell¹, Christina E. Saikus¹, Kanishka Ratnayaka^1,2, Israel M. Barbash¹, Anthony Z. Faranesh¹, Michael C. Slack, ^1,2, Robert J. Lederman¹, Ozgur Kocaturk<sup>1

1</sup>Translational 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

We have created an active MRI-compatible delivery cable incorporating a loopless antenna that enables greater visualization of the occlusion device during percutaneous delivery and deployment of the device under MRI. During in vivo use, deployment and positioning of the occlusion device in the ventricular septum was apparent with the increased signal provided by the active delivery system. The device appearance provided by this active delivery cable combined with the superior soft-tissue visualization of MRI makes the treatment of a wide range of structural heart disease under MRI guidance feasible and promising.

14:00 4155. Deflectable Catheter for Interventional Cardiovascular MRI

Ozgur Kocaturk¹, Jamie A. Bell¹, Christina E. Saikus¹, Vincent Wu¹, Merdim Sonmez¹, Kanishka Ratnayaka^1,2, Robert J. Lederman<sup>1

1</sup>Translational 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

The mechanical characteristics of most commercially available catheter devices are provided by metallic components such as metal braiding or pulling wires in deflectable devices which make them unsuitable for the MR environment. We have developed a deflectable catheter that utilizes Kevlar fiber instead to produce the same shaft support and torquability with a braided tubing and tension mechanism for tip deflection. This device could enable a wide range of MRI-guided cardiovascular interventions in difficult to reach anatomies.

14:30 4156. Simultaneous Imaging and Catheter Tracking: More Robust Performance with Joint Use of All Data

Steve Kecskemeti¹, Ethan Brodsky¹, Walter Block¹, Orhan Unal<sup>1

1</sup>Medical Physics, University of Wisconsin, Madison, WI, United States

Current methods of catheter tracking [1] interrupt the imaging sequence at some predefined update rate to acquire several projections to determine the position of the catheter. We have a taken a different approach and have developed a robust method to extract the tracking data directly from the imaging data using an interleaved 3D radial (VIPR) k-space acquisition. The method presented in this abstract uses the information from all the projections within a VIPR interleaf to determine the catheter location. This results in a more robust prediction of the catheter location and reduces the perception of jitter in the catheter position.

15:00 4157. Model-Based Catheter Shape Reconstruction for Interventional MRI

Carsten Oliver Schirra¹, Philip G. Batchelor¹, Reza Razavi¹, Sebastian Kozerke^1,2, Tobias Schaeffter<sup>1

1</sup>Division of Imaging Sciences, King’s College London, London, Greater London, United Kingdom; ²Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland

Conventional MR imaging methods result in prohibitively long measurement times hampering 3D catheter imaging in real-time. Despite progress in applying spare signal sampling theorems to catheter imaging, undersampling factors remain limited. In the present work a model-based reconstruction technique is proposed which determines the parameters describing the catheter shape directly in undersampled k-space data exploiting the limited degrees of freedom necessary. A parameterized model of a catheter is fitted by minimizing the l₂-norm. It is demonstrated that the catheter shape can be reconstructed from highly undersampled data indicating the potential of the method for 3D real-time imaging of catheter devices.