MR-Guided Focused Ultrasound

Hall B                        Monday 14:00-16:00                                                                             Computer 64           

14:00         4120.     Multislice Treatment Planning and Control for Real Time MR-Guided Prostate Ablation with Transurethral Multisectored Ultrasound Applicators

Andrew B. Holbrook1,2, Punit Prakash3, Peter Jones3, Catherine Planey2, Juan M. Santos4,5, Chris J. Diederich3, Kim Butts Pauly2, F. Graham Sommer2

1Bioengineering, Stanford University, Stanford, CA, United States; 2Radiology, Stanford University, Stanford, CA, United States; 3Radiation Oncology, UCSF, San Francisco, CA, United States; 4HeartVista, Los Altos, CA, United States; 5Electrical Engineering, Stanford University, Stanford, CA, United States

Targeted prostate ablation with transurethral multisectored ultrasound applicators could be improved with an integrated imaging platform that minimizes procedural setup and treatment time. The purpose of this work was to integrate device localization, prostate-specific planning tools, and multi-slice MR thermometry into a single imaging platform.  Various phantom experiments were performed to validate each of these steps.  Device localization and MR tracking was validated in a phantom, and an ablation was performed in another phantom with multi-slice thermometry and ROI feedback.  The platform successfully measured temperature rises and relayed that data to external power control software that regulated the ablation.

14:30         4121.     Towards Real-Time Tracking of Anatomic Features for HIFU Beam Steering

David A. Hormuth1,2, Brian J. Zappia2, Andrew B. Holbrook3, Kim Butts-Pauly3, Charles L. Dumoulin2

1Biomedical Engineering, Rose Hulman Institute of Technology, Terre Haute, IN, United States; 2Imaging Research Center, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, United States; 3Radiology, Stanford University, Stanford, CA, United States

Software for identifying and following anatomic features during real-time imaging was developed.  This software was tested in real-time images of the liver during free breathing.  It was able to successfully locate and follow the diaphragm and selected blood vessels within the liver during free breathing.  These feature locations were used to generate the coordinates of an arbitrary target within the liver with sufficient speed and robustness to provide real-time offsets to a HIFU beam.  It is anticipated that these algorithms will permit real-time ablation of liver lesions using HIFU during free-breathing and overcome the difficulties associated with breath held approaches.

15:00         4122.     MRI-Based Temperature Analysis of Transcranial MRI-Guided Focused Ultrasound Surgery for Functional Neurosurgery

Nathan McDannold1, Beat Werner2, Daniel Jeanmonod3, Eyal Zadicario4, Rita Schmidt4, Ernst Martin2

1Radiology, Brigham & Women's Hospital/Harvard Medical School, Boston, MA, United States; 2MR-Center, University Children’s Hospital Zurich, Zurich, Switzerland; 3Department of Functional Neurosurgery, University Hospital Zurich, Zurich, Switzerland; 4InSightec, Ltd., Tirat Carmel, Israel

This work used MR temperature imaging (MRTI) to evaluate focal and skull-induced heating in nine patients treated for neuropathic pain in order to characterize the safety profile of a Transcranial MRI-guided Focused Ultrasound system. The ratio between focal and skull-induced heating was 11.3 using a conservative approach, approximately 2.7 times higher than in previous tests of an earlier ver-sion in glioblastoma patients, presumably due to improvements in the system, MRTI, and differences in target location. These results suggest an improved treatment window that can potentially increase the volume of the brain that can be safely targeted by the system.

15:30         4123.     Focal Spot Visualization in MRgFUS of the Breast: MR-ARFI Vs. T1-Weighted FSE

Elena Kaye1,2, Rachel Rinat Bitton1, Kim Butts Pauly1

1Radiology, Stanford University, Palo Alto, CA, United States; 2Electrical Engineering, Stanford University, Palo Alto, CA, United States

The goal of this study was to compare MR-ARFI and T1-w FSE approaches to focal spot visualization during breast MRgFUS. An ex vivo human breast tissue sample was imaged on a 3T MRI scanner equipped with an InSightec HIFU system. MR-ARFI displacement were compared with the magnitude difference images obtained by subtraction of FSE images with ultrasound on and off. The results of the study showed that both T1-w imaging and MR-ARFI allow visualization of the FUS focal spot., however, the MR-ARFI approach deposits 10 times less ultrasound energy and gives 3 times greater SNR than an FSE-based approach.

                                   Tuesday 13:30-15:30                                                                            Computer 64           

13:30         4124.     Integrated MRI and HIFU Control System: Towards Real Time Treatment of the Liver

Andrew B. Holbrook1,2, Chuck L. Dumoulin3, Juan M. Santos4,5, Yoav Medan6, Kim Butts Pauly2

1Bioengineering, Stanford University, Stanford, CA, United States; 2Radiology, Stanford University, Stanford, CA, United States; 3Imaging Research Center, University of Cincinnati College of Medicine, Cincinnati, OH, United States; 4HeartVista, Los Altos, CA, United States; 5Electrical Engineering, Stanford University, Stanford, CA, United States; 6InSightec Ltd, Tirat Carmel, Israel

We have developed an integrated MRI and high intensity focused ultrasound (HIFU) real time system.  The system allows for both flexible control and monitoring of both systems, from device localization utilizing MR tracking to treatment planning and therapy monitoring utilizing MR thermometry pulse sequences.  Additionally, the software allows for prescription of complex sonication spots, including treatment paths and regions.  The system was tested both in a phantom and in vivo to assess its effectiveness in guiding HIFU therapy.  Prescribed treatment plans were achieved in both experiments.

14:00         4125.     In Vivo Characterization of Tissue Thermal Properties of the Kidney by HIFU Local Hyperthermia Under MR-Thermometry with Modulation of the Arterial Flow

François Cornelis1,2, Nicolas Grenier1,2, Chrit Moonen1, Bruno Quesson1

1UMR 5231, Laboratory for molecular and functional imaging, CNRS/ Université Bordeaux 2, Bordeaux, France; 2Radiology Department, CHU de Bordeaux, Bordeaux, France

The purpose was to evaluate in vivo quantitatively the tissue thermal properties (perfusion, absorption, thermal diffusivity). A total of 42 localized HIFU heating were performed in the kidney of 6 pigs monitored by MR thermometry. Arterial flow was modulated by an angioplasty balloon in the aorta. The resulting temperature data were analyzed with the Bio Heat Transfer model and an excellent correspondence was observed. Absorption and thermal diffusivity were found independent from the flow, whereas perfusion was directly linked to arterial flow. This method could improve the quality of the planning of the non invasive therapy with MR guided HIFU.

14:30         4126.     Mechanical Focal Spot Scanning with a Robotic Assistance System for MRgFUS Therapy

Axel Joachim Krafft1, Jürgen Walter Jenne2,3, Florian Maier1, Peter E. Huber3, Wolfhard Semmler1, Michael Bock1

1Medical 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

Magnetic Resonance imaging guided Focus Ultrasound Surgery (MRgFUS) is a highly precise method for non-invasive tissue ablation. Existing MRgFUS systems are mostly integrated into the patient table of the MR scanner. The objective of this ongoing project is to establish an MRgFUS therapy unit combining a commercial robotic assistance system with a fixed focus transducer as add-on. The combined system’s targeting precision was evaluated during focal spot scanning procedures. The system proved to allow for accurate and highly flexible focus positioning, and thus, might enable novel FUS treatment access.

15:00         4127.     Navigator Based FUS Transducer Tracking Without the Micro-RF Coil Setup

Naveen Bajaj1

1GE Healthcare, Bangalore, Karnataka, India

Focused ultrasound transducer tracking is of great significance in various new Magnetic Resonance guided Focused Ultrasound (MRgFUS) applications like in pain palliation of bone metastases and prostate tumor treatment. In this work, a navigator based novel method is described to demonstrate the feasibility of transducer tracking without the micro RF-coil setup. The algorithm is verified experimentally and provides highly accurate estimates, thereby making it suitable for the new applications. A novel tracking pulse sequence is also developed for the same, which is interleaved within the main thermal imaging pulse sequence.

                                   Wednesday 13:30-15:30                                                                       Computer 64           

13:30         4128.     Effect of Water Resonance Thermal Shift on Methylene T1 Estimation with Multiple Flip Angle Multipoint Dixon Technique for Fat Temperature Imaging

Mie Kee Lam1,2, Taku Iwabuchi1, Kensuke Saito1, Kagayaki Kuroda3,4

1School of Engineering, Tokai University, Hiratsuka, Kanagawa, Japan; 2Image Sciences Institute, University Medical Center Utrecht, Utrecht, Netherlands; 3Graduate School of Engineering, Tokai University, Hiratsuka, Kanagawa, Japan; 4Medical Device Development Center, Foundation for Biomedical Research and Innovation, Kobe, Hyogo, Japan

Numerical simulations were performed to investigate the effect of thermal shift of water proton resonance on the accuracy of methylene T1 estimation for fat temperature quantification with multiple flip angle, multipoint Dixon acquisitions and a least square estimation scheme. The performance of separating methylene and methyl, and estimating T1's of those species were successful as far as the frequency separations between those species and water was exact. The results with incomplete setting of the frequency separations showed that the error in methylene T1 would be controlled and an accuracy of ±4°C can be achieved by adjusting the separation within an error of ±0.05 ppm.

14:00         4129.     MR Guidance, Monitoring and Control of Brain Focused Ultrasound Therapy: In Vivo Demonstration in Rats at 7T

Benoit Larrat1, Mathieu Pernot1, Elvis Dervishi2, Danielle Seilhean2, Yannick Marie2, Anne-Laure Boch2, Jean-François Aubry1, Mathias Fink1, Mickael Tanter1

1ESPCI Paristech - Institut Langevin, CNRS UMR 7587, Paris, France; 2Hôpital de la Pitié Salpêtrière

A complete therapeutic workflow is developed to induce necrosis in the rat brain using a focused ultrasonic transducer under the guidance and monitoring of a 7T MR system. Three sequences are combined to monitor the procedure at different steps. Before the treatment, acoustic radiation force imaging shows the ability to accurately locate the focal spot in vivo. Furthermore, the MR signal is shown to provide a reliable quantification of the maximum acoustic pressure in situ. Then, the heating step is followed up via MR-thermometry. Finally, evaluated as a tool to assess necrosis. 15 rats with and without injected tumors are treated. Induced lesions are confirmed at histology.

14:30         4130.     Polyethylene Glycol (PEG) Labeled Liposomal Drug Delivery Systems as a Source for Dynamic Absolute MR Thermometry

Roel Deckers1, Sara M. Sprinkhuizen1, Bart J. Crielaard2, J H. Ippel3, R Boelens3, Twan Lammers2,4, C. J. Bakker1, L W. Bartels1

1Image Sciences Institute, University Medical Center Utrecht, Utrecht, Netherlands; 2Department of Pharmaceutics, Utrecht University, Utrecht, Netherlands; 3Department of NMR Spectroscopy, Bijvoet Center for Biomolecular Research, Utrecht University, Utrecht, Netherlands; 4Department of Experimental Molecular Imaging, RWTH Aachen, Aachen, Germany

Dynamic absolute MR thermometry may be of great interest for the precise and accurate spatio-temporal control of hyperthermia in local drug delivery applications using MR guided HIFU. In this study we evaluate the use an mFFE sequence in combination with polyethylene glycol (PEG) labeled liposomes for dynamic absolute MR thermometry. PEG provides a temperature insensitive proton resonance frequency (PRF) that can serve as reference for the temperature sensitive PRF of water. The frequency difference between the PRFs of PEG and water, and thus the absolute temperature, can be deduced from the signal evolution in time over 32 echoes acquired with the mFFE sequence.

15:00         4131.     Volumetric Ablation of Tissue Using Magnetic Resonance Imaging Guided High Intensity Focused Ultrasound (MRgFUS) with Feedback Control and Multi-Slice Thermal Monitoring: Initial Experience in a Pig Model

Jiming Zhang1, Ann Marie Marciel2, Tiina Karjalainen3, Ari Partanen4, Charles Mougenot, Amol Pednekar3, Gil Costas5, Jesse Rios5, Fredd Clubb5, John Fischer2, Robert Zurawin6, Pei Hor1, Raja Muthupillai2

1Dept of Physics, University of Houston, Houston, TX, United States; 2Diagnostic and Interventional Radiology, St. Luke's Episcopal Hospital, Houston, TX, United States; 3Clinical Science, Philips Medical Systems, Cleveland, OH, United States; 4Clinical Science, Philips Healthcare, Cleveland, OH, United States; 5Texas Heart Institute; 6Baylor College of Medicine

Preliminary results from a pig model suggest that it is feasible to create volumetric thermal lesions within in-vivo tissue using dynamic movement of the focal point of a High-Intensity Focused Ultasound beam with real-time multi-slice monitoring, and feedback control.  The measured thermal dose diameters and lengths correspond closely with planned dose diameters for treatment cell sizes ranging from 4-16 mm in diameter.

                                   Thursday 13:30-15:30                                                                          Computer 64           

13:30         4132.     SNR Trade-Offs in MR-ARFI of Focused Ultrasound in the Brain

Elena Kaye1,2, Kim Butts Pauly1

1Radiology, Stanford University, Palo Alto, CA, United States; 2Electrical Engineering, Stanford University, Palo Alto, CA, United States

MRgFUS is of interest in the treatment of various brain pathologies, such as tumors and neuropathic pain. One way to visualize the focal spot prior to the treatment relies on MR acoustic radiation force imaging. A recent implementation of MR-ARFI used a diffusion-weighted 2DFT sequence with a low b-value. The goal of this work was to find the optimum b-value for the displacement sensitizing gradient in MR-ARFI, relevant to in vivo human imaging. The optimal b-value of 33 s/mm2 was found to minimize the ghosting artifacts in vivo human brain images, and maximize displacement in the focal spot of ex vivo porcine brain, while keeping ultrasound energy minimal.

14:00         4133.     Therapeutic MRI-Guided High Intensity Focused Ultrasound Ablation of Uterine Fibroids with Volumetric Heating Technique: Early Clinical Experience in South Korea

Bilgin Keserci1,2, Young-sun Kim3, Max Oskar Köhler4, Hyunchul Rhim3, Hyo Keun Lim3

1Philips Healthcare, Seoul, Korea, Republic of; 2Samsung Medical Center,Department of Radiology, Sungkyunkwan University School of Medicine, Seoul, Korea, Republic of; 3Samsung Medical Center, Department of Radiology, Sungkyunkwan University School of Medicine, Seoul, Korea, Republic of; 4Philips Healthcare, Finland

As an alternative sonication method in magnetic resonance guided high intensity focused ultrasound treatment, volumetric sonication method with feedback control under volumetric MRI thermometry for the ablation of uterine fibroids was presented. This method efficiently utilizes the inherent heat diffusion by electronically switching the focal point between a number of predetermined locations situated at outwards-moving concentric circles with diameters of upto 16 mm. A significant improvemet in symptom severity score at 1month follow-up over baseline was observed. Volumetric treatment allows for complete and uniform cell coverage, and the delivery of optimal thermal dose significantly minimizing the risk of overtreatment.

14:30         4134.     Optimal Ultrasonic Focusing Through Strongly Aberrating Media Using Radiation Force Magnetic Resonance Guidance

Benoit Larrat1, Mathieu Pernot2, Laurent Marsac3, Benjamin Robert3, Gabriel Montaldo1, Jean-François Aubry1, Mathias Fink1, Mickael Tanter2

1ESPCI Paristech - Institut Langevin, CNRS UMR 7587, Paris, France; 2ESPCI Paristech - Institut Langevin, INSERM, Paris, France; 3SuperSonic Imagine, Aix en Provence, France

The non invasive correction of phase aberrations of ultrasonic waves is mandatory in the framework of human transcranial brain High Intensity Focused Ultrasound (HIFU) therapy at relatively high frequency (> 500 kHz). This study proposes an adaptive focusing technique based on the measurement of the acoustic intensity at the focus via MRI. The main objective is here to demonstrate the ability of acoustic radiation force MR imaging to learn experimentally how to correct strong medium aberrations with a few ultrasonic transmissions. Sharp focal spots and optimal acoustic energies are restored through several aberrating layers.

15:00         4135.     Continuous Liver Tracking During Free Breathing MRI Guided Focused Ultrasound

Yuval Zur1

1GE Healthcare Haifa, Tirat Carmel, Israel

MRI guided focused Ultrasound (FUS) tissue ablation of the liver during free breathing requires continuous tracking of all the points to be treated (target points) throughout the treatment so that the FUS transducer can deliver energy to the right position. We present a tracking method using the liver blood vessels. The tracking is done with a restricted FOV single shot EPI suitable for temperature measurement. At first the landmarks are assigned to the blood vessels. These landmarks are then tracked during heating. The location of the target point is found by 2D interpolation of the landmarks coordinates.


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 Jenne2,3, Wolfhard Semmler1, Michael Bock1

1Medical 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 Petrusca1,2, Jacqueline Ngo1, Vincent Auboiroux1,2, Francois Cotton, 23, Jean-Yves Chapelon1, Rares Salomir1

1Inserm 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 Salomir1

1Geneva 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. Moonen1

1laboratory 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 Taylor1,2, Andrew M. Elliott1, Ken-Pin Hwang, 1,3, John D. Hazle1, Roger Jason Stafford1

1Imaging 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 Stafford1

1Imaging 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 - not available

David Arthur Woodrum1, Lance Mynderse2, Akira Kawashima1, Krzysztof Gorny1, Thomas Atwell1, Fred Mcphail2, Bradley Bolster3, Wesley Gilson3, Kimberly Amrami1, Haraldur Bjarnason1, Matthew Callstrom1

1Radiology, 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 salomir1

1Radiologie, 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 Rothgang1,2, Wesley David Gilson2, Joerg Roland3, Joachim Hornegger1, Christine H. Lorenz2

1Pattern 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 Kerse1,2, Bulent Oktem3, Fatih Omer Ilday4, Ergin Atalar2,5

1Department 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 Seror1,3, Thomas Stein4, Yasmina Berber1, Mario Ries1, Chrit T. Moonen1, Bruno Quesson1

1Laboratoire 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. MacFall2

1Department 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 Jayapalan1

1MR 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 Mei1,2, Jing Yuan3, Lawrence P. Panych4, Bruno Madore4, Nathan J. McDannold4

1Department 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. Martin1

1Radiology 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 Crystal2

1Applied 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 - not available

Erol Yeniaras1, Nikhil Navkar1, Zhigang Deng1, Mushabbar A. Syed2, Nikolaos V. Tsekos1

1Computer 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. Wright1

1Medical 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 Ratnayaka1,2, Israel M. Barbash1, Anthony Z. Faranesh1, Michael C. Slack, 1,2, Robert J. Lederman1, Ozgur Kocaturk1

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

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 Ratnayaka1,2, Robert J. Lederman1

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

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 Unal1

1Medical 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 Kozerke1,2, Tobias Schaeffter1

1Division 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.

                                   Wednesday 13:30-15:30                                                                       Computer 66           

13:30         4158.     Development of a 0.014-Inch Anti-Solenoid Loop Coil: Toward Intracoronary 3.0T MRI and Interventions

Huidong Gu1, Feng Zhang1, Yanfeng Meng1, Bensheng Qiu1, Xiaoming Yang1

1Image-Guided Bio-Molecular Intervention Researchers, Department of Radiology, Institute for Stem Cell and Regenerative Medicine; University of Washington School of Medicine, Seattle, WA, United States

Atherosclerotic coronary artery disease is the main cause of heart attack. Unlike plaques in  carotid arteries, the atherosclerotic plaques in coronary arteries are difficult to be detected using conventional MRI techniques with surface coils. To solve this problem, a 0.014-inch intracoronary MR imaging-guidewire (a loopless RF coil) was invented, which enabled to generate intracoronary MRI at 1.5T and interventions under MRI guidance. In this study, we  developed a 0.014-inch anti-solenoid loop coil, an alternative to the loopless coil which might be used for generating intracoronary high-resolution 3.0T MRI and interventions.

14:00         4159.     Real-Time Navigation of a Catheter with Ferromagnetic Tip in Interventional MRI

Ke Zhang1, Axel Krafft1, Reiner Umathum1, Florian Maier1, Wolfhard Semmler1, Michael Bock1

1Medical Physics in Radiology, German Cancer Research Center, Heidelberg, Germany

Manoeuvring the interventional devices over complicated vessel branches into the target area is difficult. In this study we present a catheter with a deflectable, ferromagnetic tip and a real-time sequence for tip navigation, localization and imaging. The direction of the magnetic forces for navigation of the catheter’s tip is controlled via an iterative input device. The pulse sequence combines the acquisition of imaging and interleaved projection data for automatic alignment of imaging slice according to the tip position. The results from pig experiments proved that our application can help endovascular intervention to be easier, faster and safer.

14:30         4160.     Simultaneous Visualization of Passive Marker and Anatomical Image with Rephasing Gradient Integrated Double Echo

Ke Zhang1, Ann-Kathrin Homagk1, Wolfhard Semmler1, Michael Bock1

1Medical Physics in Radiology, German Cancer Research Center, Heidelberg, Germany

Identification of passive markers can be challenging in in vivo applications due to motion and flow artifacts. In this study we implemented a dual echo pulse sequence which acquires simultaneously a conventional MR image together with a dephased image to highlight the marker materials. After overlaying of two images the maker can be easily detected in the anatomical images.

15:00         4161.     Optimizing the Visibility of a Carbon Fiber Cannula in Spin Echo Sequences Using Currents Induced by Gradient Switching in an Attached Copper Loop: A Feasibility Study

Hanne Wojtczyk1, Hansjoerg Graf1, Petros Martirosian1, Anika Klabes1, Stefan Kegel1, Verena Ballweg1, Christoph Thomas2, Fritz Schick1

1Section on Experimental Radiology, University Hospital Tuebingen, Tuebingen, Baden-Wuerttemberg, Germany; 2Department of Diagnostic and Interventional Radiology, University Hospital Tuebingen, Tuebingen, Baden-Wuerttemberg, Germany

Some instruments for interventional MRI procedures, e.g. a carbon fiber cannula, do not produce pronounced signal voids or artifacts. The feasibility of optimizing their visibility by surrounding the object with a loop of thin copper wire was evaluated theoretically and practically: currents induced in the copper loop by gradient switching shall be utilized to create individually controlled gradient echo like artifacts in spin echo sequences. A carbon fiber tube and straws of different lengths were surrounded by loops of copper wire of different diameter and imaged at 1.5 T. The approach works in principle but may be not very practical, however possibly expandable.

                                   Thursday 13:30-15:30                                                                          Computer 66           

13:30         4162.     Intracoronary 3.0T MRI: An Ex Vivo Feasibility Study in Swine Hearts

Huidong Gu1, Feng Zhang1, Yanfeng Meng1, Bensheng Qiu1, Xiaoming Yang1

1Image-Guided Bio-Molecular Intervention Researchers, Department of Radiology, Institute for Stem Cell and Regenerative Medicine; University of Washington School of Medicine, Seattle, WA, United States

MRI is becoming a useful imaging tool for the diagnosis and treatment atherosclerotic arteries. To date, there are no reports on intracoronary MRI, which requires the placement of a small sized (usually 0.014-inch in diameter) endovascular MR coil into the coronary arteries. This study demonstrates the first attempt on the development of intracoronary 3.0T MRI technology. The combo imaging system with simultaneous use of the 0.014-inch Nitinol loopless antenna and two surface coils can function in a clinical 3.0T MR scanner. These results have established the groundwork towards in vivo intracoronary 3.0T MRI and intracoronary interventions under 3.0T MRI guidance.

14:00         4163.     Technique for Wireless Position Tracking of Intravascular Catheters: Performance Evaluation in a Vessel Phantom - not available

Harald Busse1, Gregor Thörmer1, Nikita Garnov1, Jürgen Haase2, Thomas Kahn1, Michael Moche1

1Diagnostic and Interventional Radiology, Leipzig University Hospital, Leipzig, Germany; 2Physics and Earth Sciences, Leipzig University, Leipzig, Germany

A new wireless technique for the tracking of intravascular catheters is presented. The semi-active approach uses a robust morphological image analysis tool to automatically detect the local signals from two small RF coils mounted on a commercial 6F catheter. A fast SSFP sequence at very low flip angles (≈0.3°) provided sufficient marker contrast to reliably localize the catheter in a vessel phantom (≈97% of 1036 trials) within ≈350 ms. Tracking may be realized by continuously superimposing the marker coordinates on a roadmap (≈3 updates/second) or by adjusting the slice geometry of a fast MR scan to the actual catheter orientation.

14:30         4164.     Transmit Power Optimization for Tracking, Wireless Marker and Imaging Applications of a Multi-Mode Endovascular Coil.

Krishna N. Kurpad1, Orhan Unal1,2

1Radiology, University of Wisconsin, Madison, WI, United States; 2Medical Physics, University of Wisconsin, Madison, WI, United States

The multi-mode intravascular coil consists of a single active device that is connected to the external system via a single coaxial cable and performs three functions: 1) active tip tracking, 2) imaging and 3) inductively coupled wireless marker. The coil behaves as a pseudo transmit coil due to coupling with an external transmit coil. The variable conductor density design of the multi-mode coil results in variable B1 field magnification in its vicinity. This provides an opportunity to adjust transmit power for optimal operation of the multi-mode coil in all three of its functional modes.

15:00         4165.     Phase-Field Dithering for Active Catheter Tracking

Charles L. Dumoulin1, Richard P. Mallozzi2, Robert D. Darrow3, Ehud J. Schmidt4

1Imaging Research Center, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, United States; 2ONI Medical Systems, Inc., Wilmington, MA, United States; 3General Electric Global Research, Niskayuna, NY, United States; 4Radiology, Brigham and Womens Hospital, Boston, MA, United States

An orthogonal gradient pulse is added to an MR tracking pulse sequence to change the phases of the detected MR signals.  Since the phase of the signals is unknown in the absence of the orthogonal dephaser, the dephasing gradient can either increase or decrease the strength of the acquired signal.  Consequently, the direction of the orthogonal gradient pulse is rotated through a cycle and the data in each cycle is processed to extract the most desired feature (e.g. maximum pixel detection).  This approach increases the robustness of MR tracking in low SNR conditions.