Traditional Posters : Interventional Imaging
Click on to view the abstract pdf and click on to view the pdf of the poster viewable in the poster hall.
Interventional MRI: MR-Guided Focused Ultrasound

Thursday May 12th
Exhibition Hall  13:30 - 15:30

1726.   Design and Evaluation of RF coils for Magnetic Resonance Guided High Intensity Focused Ultrasound  
Emilee Shaw Minalga1, Allison Payne1, Robb Merrill1, Dennis L. Parker1, and J. Rock Hadley1
1UCAIR, University of Utah, Salt Lake City, Utah, United States

An 11-channel cylindrical ladder coil was built to increase SNR to improve temperature measurement, cancer verification, and tissue characterization for MR guided high intensity focused ultra-sound over a single chest coil. The HIFU coil was found to improve such aspects of temperature measurement by using SNR plots, g-factor maps, human anatomy images, and temperature maps. For future human studies, this coil can add to patient safety and treatment efficacy.

1727.   Large aperture transducer designed for MR-HIFU treatment of breast tumors 
Charles Mougenot1, Max Köhler2, Matti Tillander2, Chrit Moonen3, Wilbert Bartels4, and Gösta Ehnholm2
1Philips Healthcare, Suresnes, France, 2Philips Healthcare, Vantaa, Finland, 3IMF, CNRS / Univ. Bordeaux 2, Bordeaux, France, 4University Medical Center Utrecht, Utrecht, Netherlands

A novel large aperture transducer design is proposed for MR-HIFU treatment of breast tumors. The phased array is composed of 384 elements placed on a circular structure with a lateral beam direction. This beam path orientation considerably reduces the risk of damaging nearby vital organs. In addition, this transducer shape induces a well delineated sharp focal point with low energy density in the near and far field for safe, accurate and efficient treatment. The performance of the transducer is demonstrated with acoustic field measurements and temperature maps of a phantom sonication.

1728.   Ultrasound-transparent RF coil design for improved MR thermometry of HIFU therapy 
Max Oskar Köhler1, Matti Tillander1, Antti Syrjä1, Risto Nakari1, and Mika Ylihautala1
1Philips Healthcare, Vantaa, Finland

A novel RF coil design for MR-HIFU therapy is presented that enables placing coil elements within the acoustic field without the coil interfering with the HIFU beam. The coil design furthermore allows HIFU beam propagation through the coil elements without causing imaging artifacts in the MR thermometry commonly used for therapy monitoring. This coil design allows a larger acoustic window and improved transducer access while maintaining or improving image quality. The additional coil element(s) also enable acceleration factors for MR thermometry that would otherwise not be possible. Coil performance is evaluated by acoustic field measurements and MR thermometry experiments.

1729.   Magnetic Resonance Imaging of Continuous ultrasound holograms 
Yoni Hertzberg1,2, Omer Naor3, Alex Volovick2, Shy Shoham3, and Gil Navon4
1School of Physics and Astronomy, Tel-Aviv University, Tel-Aviv, Israel, 2Insightec Ltd., Tirat Carmel, Israel, 3Faculty of Biomedical Engineering, Technion, Israel, 4School of Chemistry, Tel-Aviv University, Israel

A method for generation of continuous acoustic holograms is presented and demonstrated. Goal is to generate efficient and uniform acoustic holograms for the magnetic resonance guided focused ultrasound applications. Acoustic fields simulations and magnetic resonance temperature elevation measurements of the first three English letters holograms are presented. The acoustic holograms were generated on relative small areas of 1.5x1.5cm and in sub-millimeter acoustic field resolution to demonstrate the high accuracy and flexibility of this method. By using this technology, the efficiency and safety of focused ultrasound applications, e.g. hyperthermia and ultrasound neural stimulation, could be further improved.

1730.   Adaptive Volumetric MR-guided High-Intensity Focused Ultrasound Ablations 
Silke Hey1, Baudouin D. de Senneville1, Charles Mougenot2, Max Köhler3, Chrit Moonen1, and Mario Ries1
1IMF, CNRS / Univ. Bordeaux 2, Bordeaux, France, 2Philips Healthcare, Suresnes, France, 3Philips Healthcare, Vantaa, Finland

Real time feedback control of the HIFU beam position and the beam power during MR-guided interventions requires continuously updated volumetric information of the thermal dose and temperature over the entire target area. Here, a dynamic volume sweep for volumetric and motion compensated MR-thermometry and dosimetry is presented in combination with a real time adaptation of the ablation trajectory. The feedback control algorithm is based on the target temperature, as it is required for the use of HIFU in local drug delivery applications, or alternatively directly on thermal dose estimates as is preferable for the direct thermal destruction of tumors.

1731.   MR-ARFI and SWI to Detect Calcifications in the Brain in MRgHIFU Treatments 
Rachel Rinat Bitton1, Elena Kaye1,2, and Kim Butts Pauly1
1Radiology, Stanford University, Stanford, CA, United States, 2Electrical Engineering, Stanford University, Stanford, CA, United States

Calcifications have the potential to interfere with an MRgHIFU treatment in the brain. Although they may be identified in pre-treatment CT scans, they are not registered to the MR images or the in vivo HIFU focal spot. In this study we present the use MR-ARFI imaging to detect a calcification in ex-vivo swine brain by creating a displacement weighted map of an ROI larger than the focal spot. This technique is proposed as an adjunct to SWI in order to visualize calcifications prior to an MRgHIFU brain treatment.

1732.   Evaluation of bipolar encoding configurations for spin echo MR-ARFI 
Elena Kaye1, and Kim Butts Pauly2
1Electrical Engineering, Stanford University, Palo Alto, CA, United States, 2Radiology, Stanford University, Palo Alto, CA, United States

In this work we investigate the performance of three displacement encoding configurations that were recently proposed for spin echo based MR-ARFI pulse sequences. Displacement phase images were obtained using three methods in ex vivo brain tissue and tissue mimicking phantom.

1733.   MRgHIFU safety issue: Validation of targeting accuracy using an MR compatible ballistic model 
Magalie Viallon1, Lorena Petrusca1, Sylvain Terraz1, Thomas Goget1, Vincent Auboiroux1, Christoph Becker1, Patrick Gross2, and Rares Salomir1
1Radiology, Hopital Universitaire de Genève, GENEVE, Switzerland, 2Siemens Healthcare, Erlangen, Germany

Fast volumetric ablation (5 to 6 cubic centimeters per minute) has been investigated in vivo demonstrating that a large and uniform ablation zone may be obtained rapidly. However, no experimental demonstration was provided that such volumetric lesion is indeed centered on a specific predefined target in 3D, i.e. no proof of absence of thermal buildup drift during the sonication. The effective spatial control of the induced thermal lesion during fast volumetric ablation should be considered as a major safety issue. Therefore before clinical trials, it is highly desirable to evaluate in animal models, the accuracy of the spatial control of ablation for a given volumetric HIFU sonication paradigm. We describe here a method to create a user-defined ballistic target as absolute reference marker that is MR-compatible and MR-detectable, while also being a well-established histology staining.

1734.   MRgHIFU safety issue: Multi-layer protection against tissue-to-air interface heating 
Magalie Viallon1, Sylvain Terraz1, Thomas Goget1, Lorena Petrusca1, Denis Morel2, Vincent Auboiroux1, Christoph Becker1, Patrick Gross3, and Rares Salomir1
1Radiology, Hopital Universitaire de Genève, GENEVE, Switzerland, 2Anesthesiology, Hopital Universitaire de Genève, GENEVE, Switzerland, 3Siemens HealthCare, Erlangen, Germany

MRgHIFU is a hybrid technology which aims to offer efficient and safe thermal ablation of targeted tumors or other pathological tissues, while preserving the normal surrounding structures unaltered. Theoretically MRgHIFU has no limitation on lesion size. The main challenge is to avoid near and far field heating. We demonstrate here that reflection at air-tissue interfaces in the far field is a problem and we evaluate an home-made multi-layer protection against tissue-to-air interface heating.

1735.   Online temperature control of focused ultrasound heating using an adaptive PID feedback loop 
Silke Hey1, Mario Ries1, and Chrit Moonen1
1IMF, CNRS / Univ. Bordeaux 2, Bordeaux, France

The combination of real time MR thermometry with a proportional, integral, derivative (PID) feedback control has been suggested as a precise solution for controlling high intensity focused ultrasound devices in applications such as local drug delivery. However, depending on the desired target temperature profile and the measurement noise, overshoots and oscillations can occur, which lead to undesired tissue damage. Here an adaptive PID controller algorithm is presented that continuously adjusts the controller gains as a function of the current temperature error and the measurement noise. Its superior performance in comparison to a conventional PID controller with static controller gains is demonstrated experimentally.

1736.   Full coverage 3D temperature mapping for transcranial MRgHIFU applications 
Nick Todd1, Henrik Odeen1, Allison Payne1, Laurent Marsac2, Dorian Chauvet3, Mathieu Pernot4, Anne-Laure Boch3, Jean-Francois Aubry4, Mickael Tanter4, and Dennis L Parker1
1University of Utah, Salt Lake City, UT, United States, 2SuperSonic Imagine, Aix en Provence, France, 3Département de Neurochirurgie, Hôpital Pitié Salpêtrière, Paris, France, 4Institut Langevin, ESPCI ParisTech, France

New techniques for focusing ultrasound through the skull have made non-invasive heating in the brain possible, paving the way to clinical applications such as tumor ablation and targeted drug delivery via blood-brain barrier opening. However, high bone absorption can lead to undesirable heating outside of the focus and severe consequences if not properly monitored. To realize 3D MR thermometry over the entire volume of interest, we have developed an approach that combines a modified 3-D segmented EPI sequence with data undersampling and a constrained reconstruction method to provide temperature maps with good spatial resolution, large volume coverage, and high temporal resolution.

1737.   Investigating the Use of Short Pulses in MRI-guided Focused Ultrasound Disruption of the Blood Brain Barrier 
Meaghan O'Reilly1, and Kullervo Hynynen1,2
1Imaging Research, Sunnybrook Research Institute, Toronto, Ontario, Canada, 2Medical Biophysics, University of Toronto

Short pulses have been previously used to eliminate standing waves in the skull cavity in MR-guided transcranial ultrasound disruption of the blood-brain barrier (BBB) and improve treatment consistency. Parameters related to the use of these short pulses to disrupt the BBB were examined. Disruption of the BBB was performed in rats using sonations as short as 3μs in length at a 1Hz PRF. Mean contrast-enhanced T1w enhancement levels showed a reduced level of BBB disruption for short sonations at low PRF. However, the use of short bursts could substantially reduce treatment times when treatment of large volumes is required.

1738.   Blood-Brain Barrier Disruption in Pigs by Transcranial Focused Ultrasound: Correlation of Cavitation Signals and MR Imaging for Treatment Monitoring 
Yuexi Huang1, Junho Song1, and Kullervo Hynynen1,2
1Imaging Research, Sunnybrook Research Institute, Toronto, ON, Canada, 2Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada

Magnetic resonance guided focused ultrasound (MRgFUS) has been demonstrated to reversibly disrupt the blood-brain barrier (BBB) for targeted drug delivery on small animal models. For large animals, however, a precise control of the location and pressure of the ultrasound focus is difficult due to the deflection and absorption of the ultrasound beam by the relatively thicker skull. In this study, a low frequency (230kHz) MRgFUS brain system was used to demonstrate the feasibility of localized BBB disruption in pigs without craniotomies. Cavitation signals from sonicated microbubbles were detected by hydrophones as a mean to monitor the treatment in real-time. The levels of cavitation signals at various acoustic powers showed good correlation to the levels of BBB disruption and tissue damage measured by T1-weighted and T2-weighted MR images.

1739.   Changes in attenuation coefficient in MRgFUS treatments of in-vivo rabbit thigh estimated using MRTI-derived specific absorption rate patterns 
Urvi Vyas1, Allison Payne1, Nick Todd1, Dennis L Parker1, Robert B Roemer1, and Douglas A Christensen1
1University of Utah, Salt Lake City, Utah, United States

The accuracy of acoustic properties used in beam simulation techniques impacts the accuracy and efficacy of treatment planning and control in Magnetic Resonance Imaging-guided focused ultrasound surgery (MRIgFUS). In this research we use the traditional rate of heating technique with an optimization routine, MR-temperature imaging and a fast beam propagation technique to non-invasively estimate subject-specific tissue acoustic properties.

1740.   In-vivo MR guided High Intensity Focused Ultrasound ablation of pig liver tissues: Preliminary results of a survival study. 
Frederic Courivaud1, Airazat M. Kazaryan1, Alice Lund2, Per Steinar Halvorsen1, Bjørn Edwin1, and Per Kristian Hol1
1The Intervention Centre, Oslo University Hospital, Oslo, Norway, 2Department of Pathology, Oslo University Hospital, Oslo, Norway

Colorectal cancer has a high incidence and is a common cause of cancer death. Surgical removal of colorectal cancer metastases in the liver improves survival rate of these patients but cannot be applied in many cases. MR guided High Intensity Focused Ultrasound (HIFU) is a promising minimal invasive alternative to surgery. However, substantial work is still needed to validate this approach. We demonstrate in this survival study a method to apply HIFU ablation using several sonication cycles during mechanically controlled breath-hold periods on anaesthetized pigs. Ablation is confirmed by MRI and histopathology one week after HIFU treatment.

1741.   Detection and exploitation of acoustic cavitation for enhancement of MR guided High Intensity Focused Ultrasound heating in ex vivo liver 
Delphine Elbes1, Benjamin Robert2, Max O Köhler3, Mickael Tanter2, Chrit Moonen1, and Bruno Quesson1
1Laboratory for Molecular and Functional Imaging, UMR 5231, CNRS/Université Bordeaux 2, Bordeaux, France, 2Inserm U979 physique des ondes pour la médecine, institut Langevin (CNRS UMR 7587), ESPCI ParisTech, Paris, France, 3Philips healthcare, Vantaa, Finland

This study aims to detect and exploit acoustic cavitation for enhancement of High Intensity Focused Ultrasound (HIFU) heating in ex vivo liver. MR acoustic radiation force imaging (MR-ARFI) allowed visualization of the local tissue displacement in absence/presence of cavitation induced by a short and intense HIFU pulse. The temperature increase measured by MR-thermometry was higher in presence of cavitation. The spatial distribution of the acoustic pressure (MR-ARFI) in presence of cavitation was coherent with the observed modifications on MR-thermometry. Enhancement of tissue heating with acoustic cavitation may improve the efficiency of MR guided HIFU ablation in the liver.

1742.   MRI-controlled focused ultrasound hyperthermia in bone for thermally mediated drug delivery 
Robert Staruch1,2, Melissa Togtema1, Rajiv Chopra1,2, and Kullervo Hynynen1,2
1Centre for Research in Image-Guided Therapeutics, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada, 2Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada

MRI-controlled focused ultrasound was used to generate mild hyperthermia at a soft tissue-bone interface in 5 rabbit thighs, for the purpose of achieving localized drug delivery with thermosensitive liposomes. FSPGR images perpendicular to the ultrasound beam were used for temperature control in muscle adjacent to bone. Median temperatures in a 10mm target were maintained at 43°C for 20min. Muscle adjacent to heated bone had 18-fold higher drug concentrations as muscle adjacent to unheated bone. The results demonstrate the feasibility of MRI-controlled focused ultrasound hyperthermia at soft tissue-bone interfaces, and its potential for localized drug delivery with thermosensitive liposomes.

1743.   Pain Palliation of Bone Metastasis: Initial Clinical Experience Using High Intensity Focused Ultrasound Therapy with Magnetic Resonance Guidance 
Alessandro Napoli1, Michele Anzidei2, Giulia Brachetti2, Luisa Molisso2, Carlo Catalano2, and Roberto Passariello2
1Radiological Sciences, Policlinico Umberto I, Rome, Rome, Italy, 2Radiological Sciences, Policlinico Umberto I, Rome, Italy

MRgFUS is a new technique that allows non invasive palliation of bone metastases pain with a real-time control of the achieved temperature and consequently necrosis induced.

1744.   Quality assurance of volumetric feedback MR-guided HIFU ablation technique in human uterine fibroids 
Heikki Juhani Nieminen1, Charles Mougenot2, Bilgin Keserci3, Jouko Soini1, Sham Sokka4, Max Oskar Köhler1, and Teuvo Vaara1
1Philips Healthcare, Vantaa, Finland, 2Philips Healthcare, Bordeaux, France, 3Philips Healthcare, Seoul, Korea, Republic of, 4Philips Healthcare, Andover, MA, United States

The most common clinical application of Magnetic Resonance guided High Intensity Focused Ultrasound (MR- HIFU) is the thermal ablation of uterine fibroids. The spatial targeting and thermal dose volume accuracies of the volumetric feedback procedure are here studied based on data acquired in a clinical study with 33 patients and a total of 38 symptomatic fibroids. Based on an analysis of the ablated volumes produced by the 471 sonications performed with the Philips Sonalleve MR-HIFU system, the accuracy appears to be better than the imaging resolution, 2.5×2.5×7.0mm, which is acceptable compared to typical fibroid sizes of 3-15cm in diameter.

Traditional Posters : Interventional Imaging
Click on to view the abstract pdf and click on to view the pdf of the poster viewable in the poster hall.
Interventional MRI: Instrument Visualization, Guidance & Interfaces

Monday May 9th
Exhibition Hall  14:00 - 16:00

1745.   Latex-Based Dual Contrast Hybrid Catheter for Passive MR-Guided Angiographic Interventions 
Robert R. Edelman1,2, Wei Li3, Anthony Farrell3, Eugene Dunkle3, and Ioannis Koktzoglou3,4
1Radiology, NorthShore University HealthSystem, Evanston, IL, United States, 2Radiology, Northwestern University, Chicago, IL, United States, 3NorthShore University HealthSystem,4Radiology, University of Chicago, Chicago, IL, United States

A hybrid catheter design for passive MR-guided interventions which enables dual contrast mechanisms has been implemented based on a standard angiographic catheter. It uses deposits of an iron oxide-containing compound to enable thick slice dynamic imaging with a T2*-weighted acquisition having a frame rate of 2Hz. An outer coating of gadolinium-doped latex enables static imaging with high spatial resolution using a T1-weighted dual echo 3D radial acquisition. Although latex has not previously been used for passive catheter tracking, it was found to produce high catheter conspicuity on T1-weighted dual echo UTE images, which was further enhanced by image subtraction.

1746.   Hyperpolarised gas filled MRI catheter with MR pressure measurement sensitivity 
Jim M Wild1, Salma Ajraoui1, X Xu1, Martin H Deppe1, Andrew J Swift1, Smitha Rajaram1, David J Kiely2, and Juan Parra-Robles1
1University of Sheffield, Sheffield, Yorkshire, United Kingdom, 2Sheffield Pulmonary Vascular Disease Clinic, United Kingdom

In this work the feasibility of using a hyperpolarised gas filled catheter for catheter tracking was explored with pulse sequences for synchronous dynamic 3He/1H MRI. The pressure dependence of the 3He apparent diffusion coefficient (ADC) in the catheter balloon was also demonstrated in phantom experiments with the ultimate aim of MR based pressure measurement without the use of a transducer.

1747.   Accurate Localization of Active Devices during Interventional MR Imaging 
Julien Barbot1, Tobias Wech2, Steven Shea2, Li Pan2, Klaus Kirchberg1, Kamal Vij3, Christine H. Lorenz2, and Sunil Patil2
1Center for Applied Medical Imaging, Siemens Corporate Research, Princeton, NJ, United States, 2Center for Applied Medical Imaging, Siemens Corporate Research, Baltimore, MD, United States, 3SurgiVision, Inc., Irvine, CA, United States

For vascular interventions, precise localization of the catheter is paramount for a successful procedure. For MR, this has been accomplished by tracking microcoils with three, 1D projection images. In past publications, position was determined by finding the maximum value in each projection. In this work, we calculate a simulated projection signal for a given solenoid coil and then correlate this model with incoming projections to improve position detection. The method was tested in a phantom against the maximum detection method and the newly proposed method was significantly more accurate than maximum detection, with results less than 1 mm from ground truth.

1748.   Active MR tracking using micro coils for both transmit and receive 
Barret Daniels1,2, Yu Li1, Randy Giaquinto1, Wolfgang Loew1, Ronald Pratt1, and Charles Dumoulin1
1Imaging Research Center, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, United States, 2Bioengineering, University of Cincinnati, Cincinnati, Ohio, United States

Conventional active MR tracking utilizes the body coil to excite all spins within the volume of interest and micro-coils built into devices for signal reception. This approach often results in a signal with a complicated phase sensitivity profile making tracking difficult. In this work, we overcome this challenge by using the micro-coil for both transmitting and receiving. Transmitting with micro coils excites only those spins near the micro coil and imparts the same phase sensitivity profile for spin excitation and reception. This results in a more robust peak with higher SNR and improved tracking accuracy.

1749.   Parallel transmit with toroidal transceiver for enhanced visualization and RF safety 
Maryam Etezadi-Amoli1, Pascal Stang1, John M Pauly1, Adam B Kerr1, and Greig C Scott1
1Stanford University, Stanford, CA, United States

We built a transmit-receive toroid that allows positive-contrast visualization of conductive structures, such as guidewires and EP ablation devices, with at most minimal modification to these devices. By actively driving the conductive structure with very low power levels, the conductor body and tip can be clearly visualized with extremely high SNR. RF safety can be ensured by using parallel transmit with an array of surface coils and treating the transceive toroid and conductive wire as an additional, actively controllable element of the transmit array.

1750.   Suppression of RF Heating due to Intravascular Devices using Non-resonant In-line Coaxial Choke Baluns 
Krishna N Kurpad1, Madhav Venkateswaran2, and Orhan Unal1,3
1Radiology, University of Wisconsin, Madison, WI, United States, 2Electrical and Computer Engineering, University of Wisconsin, Madison, WI, United States, 3Medical Physics, University of Wisconsin, Madison, WI, United States

This abstract addresses the problem of RF heating in interventional devices. There is some degree of skepticism of the effectiveness of coaxial chokes as it is hypothesized that self-resonant chokes will only shift the problem of RF heating to the choke itself. In this work, which is an extension of earlier work on coaxial choke baluns, we demonstrate the effectiveness of the non-resonant coaxial choke in suppressing RF heating not only at the microcoil but also in the vicinity of the choke.

1751.   A Miniaturized Optical Link for an Active Intravascular MR-Device 
Stephan Fandrey1, Steffen Weiss2, and Jörg Müller1
1Hamburg University of Technology, Hamburg, Germany, 2Imaging Systems and Intervention, Philips Research Europe, Hamburg, Germany

A miniaturized all-optical active MR-probe for catheter guidance and intravascular imaging in MR-guided interventions is demonstrated. The probe transmits the MR-signal received by a foil-based micro-coil via an optical fiber to the MR-receiver and is equipped with an optical power supply, making the system inherently RF-safe. Miniaturization of the probe firstly allowed the integration into a 6F catheter tube. Projection-based tip tracking and high resolution MR imaging were successfully performed in phantom with a significantly improved SNR compared to a previously presented system, which now is comparable to the SNR of direct electrical signal transmission.

1752.   Optoelectronic CMOS Power Supply Unit for Interventional MRI Devices 
Baykal Sarioglu1, Ozan Aktan1, Umut Cindemir1, Gunhan Dundar1, Cengizhan Ozturk1, Senol Mutlu1, and Arda Deniz Yalcinkaya1
1Bogazici University, Istanbul, Turkey

An optoelectronic power supply suitable for electronic circuits of interventional devices is presented.

1753.   Measurement Accuracy of Different Active Tracking Sequences for Interventional MRI 
Tobias Wech1,2, Steven M Shea1, Li Pan1, Julien Barbot1, Kamal Vij3, Christine H Lorenz1, and Sunil Patil1
1Center for Applied Medical Imaging, Siemens Corporate Research, Baltimore, Maryland, United States, 2Institute of Radiology, University of Wuerzburg, Wuerzburg, Bavaria, Germany,3SurgiVision Inc, Irvine, California, United States

For interventional MRI, precise localization of the catheter is crucial. In this work, a study was performed to compare the accuracy of three different tracking sequences (Single-Echo, Dual-Echo, Hadamard Multiplexed). A dedicated phantom was constructed out of LEGO Duplo bricks (Bilund, Denmark) that offered several defined positions for the experiments. Hadamard Multiplexed showed the most stable and accurate results, especially in the presence of off-resonance conditions, although Single Echo may also offer sufficient accuracy for time-critical applications.

1754.   Accuracy Evaluation of Phase-Only Cross Correlation (POCC) Guidance Sequence for Real-Time 3T MR-Interventions 
Patrik Zamecnik1, Axel Joachim Krafft2, Florian Maier2, Jens Groebner2, Heinz-Peter Schlemmer1, and Michael Bock2
1Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany, 2Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany

Recently, an automatic tracking technique using a phase-only cross correlation algorithm (POCC) has been presented, which uses a passive MR marker for real time needle guidance during prostate biopsies or to guide a laser fiber in an experimental thermoablation (LITT) of the liver. In this study the geometric accuracy of the needle guidance using POCC sequence at 3T was tested in a phantom experiment. The accuracy of the procedure proved to be very high. Safe and precise instrument guidance was demonstrated with the automatic tracking sequence during insertion of puncture needle into the target at 3 Tesla conditions.

1755.   eXTernal Control (XTC): a flexible, real-time, low-latency, bi-directional scanner interface 
Jouke Smink1, Marko Häkkinen2, Ronald Holthuizen1, Sascha Krueger3, Mario Ries4, Yasmina Berber4, Chrit Moonen4, Max Köhler2, and Erkki Vahala2
1Philips Healthcare, Best, Netherlands, 2Philips Healthcare, Helsinki, Finland, 3Philips Research, Hamburg, Germany, 4IMF, Bordeaux, France

Typical interventional applications integrate data from several sources and perform real-time image-processing prior to applying feedback to the procedure. We have developed a new interface to the scanner, denominated XTC, which allows an external computer or a co-hosted application to control every scan protocol. The interface uses a minimalistic CORBA interface and provides fast access to output data (raw data, images, physiology sensors, navigator data and device positions) and allows update of scan parameters like geometry during scanning. Applications have been developed in MR-guided HIFU and EP. An open source development environment has been made available for Windows and Linux.

1756.   Impact of reduced k-Space acquisition on the Visibility of Moving Puncure Needles - A Phantom Study 
Jens Christian Rump1, Martin Jonczyk1, Christian Jürgen Seebauer1, Felix Güttler1, Ulf Teichgräber1, and Bernd Hamm1
1Radiology, Charité-University Medicine, Berlin, Germany

The purpose of our study was to evaluate the feasibility of keyhole imaging of superposed needle movements in a phantom model using an imaging sequence with realistic interventional parameters for muscular-skeletal interventions. Therefore, MR-images with different keyhole update rates of the outer k-space from 15 to 100% of a moving needle were acquired. For a reproducable needle motion, the needle was driven by a custom made puncture simulator. The visibility was measured by the CNR, artifact width and the sharpness of the artifact edges. No significant changes of the visibility of the needle was found reducing the k-space. Even low update rates of the k-space allow a sufficient visualization of a puncture needle in muscularskeletal interventions.

1757.   Direct On Patient Image Display with a Laser PicoP Projector For Medical Device Placement 
Andrew B. Holbrook1,2, Mark Freeman3, Yoav Medan4, and Kim Butts Pauly1
1Radiology, Stanford University, Stanford, CA, United States, 2Bioengineering, Stanford University, Stanford, CA, United States, 3Microvision, Redmond, WA, United States, 4InSightec, Tirat Carmel, Israel

Positioning of medical devices on or in the patient before an MR-guided procedure is hampered by the need to pull the patient out of the imaging system for initial placement. The purpose of this work was to demonstrate the feasibility of displaying images directly on patients from above the scanner using a laser PicoP projector. A proof of concept was performed both in vivo and a phantom on the table immediately outside a 3T magnet to demonstrate the technology. Images of each were displayed on the outer surface, allowing for easy visualization of internal anatomy on the external structure.

1758.   Catheter Tracking with Phase Information 
Kevan James Thompson Anderson1, Greig Scott2, and Graham A. Wright1,3
1Medical Biophysics, University of Toronto, Toronto, Ontario, Canada, 2Electrical Engineering, Stanford University, United States, 3Imaging Research, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada

A new active technique is described that utilizes phase information in the MR signal to determine the position and orientation of a catheter-based microcoil. Phase images acquired around a small receive coil are rich in information and can be collected over a large spherical volume with a diameter several times that of the receive coil. The high degree of redundancy yields the potential for an accurate and robust method of catheter tracking. A tracking algorithm is presented that performs catheter tip localization using phase images acquired in two orthogonal planes. Associated experimentation demonstrating feasibility is also presented.

1759.   MR Endoscope with Software-Controlled Tuning, Device Tracking and Video 
Jerome L Ackerman1,2, Erez Nevo3, Evan J. Zucker1,4, Alec J. Poitzsch1,5, Katherine Vandenberg1,6, Andrew Zhigalin7, and Barry Fetics3
1Martinos Center/Department of Radiology, Massachusetts General Hospital, Charlestown, MA, United States, 2Harvard Medical School, Boston, MA, United States, 3Robin Medical, Inc., Baltimore, MD, United States, 4Tufts Medical Center, Boston, MA, 5Massachusetts Institute of Technology, Cambridge, MA, United States, 6Florida International University, Miami, FL, United States, 7Johns Hopkins School of Medicine, Baltimore, MD, United States

An MR endoscope with deployable RF coil, integrated preamplifier, varactor remote tuning circuitry, software-controlled tuning, video system and position/orientation tracking sensor was developed. Tuning was controlled by adjusting varactor diode bias voltages via a computer program. The tuned condition was found and continuously maintained by a modified simplex algorithm. Device performance, assessed with phantoms and animal carcasses, was found to achieve 130 μm resolution in a brief scan or 47x the SNR of the body RF coil. Optimization parameters which impose limits on simplex dimensions play major roles in the agility of the algorithm in tracking changing tuning conditions.

Traditional Posters : Interventional Imaging
Click on to view the abstract pdf and click on to view the pdf of the poster viewable in the poster hall.
Interventional MRI: Thermotherapy & Thermometry

Tuesday May 10th
Exhibition Hall  13:30 - 15:30

1760.   Feasibility of RF Ablation at the Larmor Frequency for RF Field Visualization 
Kim Shultz1, Pascal Stang1, John Pauly1, and Greig Scott1
1Electrical Engineering, Stanford University, Stanford, CA, United States

The process of RF ablation treatment is often imaged with MRI using temperature mapping. MRI has the additional cabability of imaging the RF fields from the ablation currents if the ablation is performed at the Larmor frequency. We demonstrate the feasibility of performing ablation at 64 MHz with temperature and impedance monitoring and show the change in RF field maps from the ablation procedure.

1761.   MR-Mediated Radio Frequency Ablation 
Jerome L Ackerman1,2, YiK Kiong Hue1,2, Erez Nevo3, Alexander R. Guimaraes1,2, Martin Polak1,4, Kyum S. Lee1, and Daniel E. Ackerman1
1Martinos Center/Department of Radiology, Massachusetts General Hospital, Charlestown, MA, United States, 2Harvard Medical School, Boston, MA, United States, 3Robin Medical, Inc., Baltimore, MD, United States, 4Children's Hospital, Boston, MA, United States

MR-Mediated Radiofrequency Ablation (MR-RFA) is a novel method for producing thermal lesions in tissue for the purpose of destroying tumors. In this method the scanner not only provides image guidance for placing the RF applicator, it also supplies the RF energy for heating. In gel phantoms MR-mediated RFA yielded temperatures of up to 100 °C and heating rates up to 4 °C/s, somewhat more modest temperatures and heating rates in tissue specimens, and temperatures over 70 °C in live pigs undergoing MR-mediated RFA of the liver. In vivo, thermal lesions 1 cm in diameter were achieved within the liver.

1762.   Enhanced Intra-Operative Control During Cryoablation by Using the PRF Method: In Vivo Imaging and Histopathologic Correlation 
Eva Rothgang1,2, Wesley D. Gilson2, Steffi Valdeig3, Li Pan2, Jörg Roland4, Aaron Flammang2, Christine H. Lorenz2, Frank Wacker3, and Bernd Frericks5
1Pattern Recognition Lab, University Erlangen-Nuremberg, Erlangen, Germany, 2Center for Applied Medical Imaging, Siemens Corporate Research, Baltimore, MD, United States, 3Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University, Baltimore, MD, United States, 4Siemens Healthcare, Erlangen, Germany, 5Department of Radiology and Nuclear Medicine, Universitätsmedizin Berlin–Charité Campus Benjamin Franklin, Berlin, Germany

For enhanced intra-operative control during cryoablation, we propose to online monitor the procedure using the proton resonance frequency method (PRF). By monitoring temperatures in close proximity to the region being ablated, procedure safety and efficacy can be increased. The purpose of this study was to demonstrate the value of online PRF temperature monitoring to 1) estimate the pattern of ice ball growth between multiple cryoprobes; and 2) prevent injury to adjacent structures. In this study, PRF imaging during in vivo cryoablation of porcine kidney was compared to post-ablation imaging and histopathology.

1763.   Real-time hybrid MR thermometry of human ventricular myocardium with and without blood suppression 
Viola Rieke1, Andrew B Holbrook1, William Grissom2, Juan M Santos3, Michael V McConnell4, and Kim Butts Pauly1
1Department of Radiology, Stanford University, Stanford, CA, United States, 2Imaging Technologies Laboratory, GE Global Research, Munich, Germany, 3Heart Vista, Inc., Los Altos, CA, United States, 4Division of Cardiovascular Medicine, Stanford University, Stanford, CA, United States

In recent years there has been increased interest to perform cardiac interventions such as EP ablation under MR-guidance. Directly monitoring the temperature rise during these procedures could potentially be helpful to verify successful ablation and predict treatment outcome. In this study, we investigate the feasibility of monitoring temperature changes in the left ventricular myocardium in real-time using spiral imaging at 3T with varying imaging parameters with and without blood suppression. Temperature images based on the proton resonance frequency (PRF) shift are reconstructed using a hybrid method that combines multi-baseline subtraction and referenceless thermometry.

1764.   Limited FOV MR thermometry using a local cardiac RF coil in atrial fibrillation treatment 
Nelly A. Volland1,2, Eugene G. Kholmovski1,2, J. R. Hadley1, and Dennis L. Parker1
1Radiology / Utah Center for Advanced Imaging Research, University of Utah, Salt Lake City, UT, United States, 2Comprehensive Arrhythmia Research & Management Center, University of Utah, Salt Lake City, UT, United States

Introduction: Limited FOV MR temperature image acquisition in less than 200 ms with high sensitivity was investigated using a local RF cardiac coil. Methods: Loop coil was designed, coated, and tested to assess the feasibility of measurements. Results: SNR gain attainable with local coil in static phantom compared to surface coils was 26 times. Stable MR phase images were acquired within 230 ms on limited FOV imaging volume without aliasing in moving phantom 4 times faster than surface coils could allow. Conclusions: Local cardiac coil was successfully used to perform MR thermometry in static and moving phantoms.

1765.   Feasibility of fast MR-thermometry during cardiac RF ablation 
Baudouin Denis de Senneville1, Sébastien Roujol1, Pierre Jaïs2, Chrit TW Moonen1, Gwenaël Herigault3, and Bruno Quesson1
1Laboratory for Molecular and Functional Imaging: From Physiology to Therapy, CNRS/University of Bordeaux 2, Bordeaux, Gironde, France, 2Hôpital Cardiologique du Haut-Lévèque, Bordeaux, France, 3Philips Healthcare, France

On-line MR-temperature monitoring during radio-frequency ablation of cardiac arrhythmias may improve the efficacy and safety of the treatment. Magnetic Resonance Imaging can provide rapid and quantitative thermometric measurements in addition to a detailed anatomical information. For this purpose, cardiac triggering and dynamic navigator-based slice tracking were combined with image registration and modeling of susceptibility changes with respiration, in order to investigate the precision of PRF thermometry during a RF ablation in-vivo on a sheep heart.

1766.   Modified Turbo Spin Echo sequence for PRF based thermometry 
Mahamadou Diakite1, Rock Hadley2, and Dennis L. Parker2
1Physics, University of Utah, Salt Lake City, Utah, United States, 2Radiology, University of Utah, Salt Lake City, Utah, United States

The goal of the present work is to show the feasibility of proton resonance frequency (PRF) shift based thermometry using a modified Turbo Spin Echo (modified TSE) sequence.. In this work, we present a modified TSE sequence to generate phase maps, in which the proton resonance frequency shift is detected.Although, the proposed modified TSE sequence is in an early development stage, we have shown that this sequence can be used to monitor temperature and could be used to quantify heating effects in suspect TSE studies.

1767.   Modified EPI sequence for improved MR thermometry 
Bruno Madore1, Renxin Chu1, Chang-Sheng Mei1, Jing Yuan2, Tzu-Cheng Chao1, and Lawrence P. Panych1
1Department of Radiology, Harvard Medical School, Brigham and Women's Hospital, Boston, MA, United States, 2Department of Imaging and Interventional Radiology, the Chinese University of Hong Kong

An MR thermometry method is proposed that offers advantages in terms of temperature-to-noise-ratio (TNR), tissue contrast and temperature accuracy. An interleaved-EPI sequence was modified so that both a gradient-echo and a spin-echo-like magnetization pathway would be sampled every TR. Three main advantages come from sampling both types of signal: 1) Independent temperature measurements can be combined for improved TNR, 2) images of different contrast can be compared to help identify blood vessels and/or regions of thermal damage, and 3) system imperfections, such as sub-optimal shimming, can be detected and corrected for, potentially enabling improvements in temperature accuracy.

1768.   Improved hybrid PRF-T1 pulse sequence for accurate T1 mapping in high field (3T) 
Mahamadou Diakite1, Nick Todd2, and Dennis L. Parker2
1Physics, University of Utah, Salt Lake City, Utah, United States, 2Radiology, University of Utah, Salt Lake City, Utah, United States

Accurate temperature mapping in tumor and surrounding tissue throughout the thermal therapy is essential to ensure the safety and efficacy of thermal treatment. Methods based on the temperature dependency of the water proton resonance frequency (PRF) shift have shown the best ability to quantify temperature rises in soft tissues. Unfortunately, the PRF shift with temperature does not apply to lipid protons, since there is no hydrogen bonding among the methylene protons that supply the bulk of fat signal. However, the temperature sensitivity of the spin-lattice relaxation time, T1, has been measured for a number of fatty tissues and found to obey a linear relationship over a small temperature range [1]. We previously proposed the hybrid PRF-T1 method to combine these two techniques to simultaneously monitor temperature in fat and soft tissues. In this work, we show a sequence implementation and improve the accuracy of T1 measurements for better temperature mapping.

1769.   1H MRS temperature calibrations in tissue-equivalent gel phantoms show dependence on macromolecular concentration 
Nigel Paul Davies1, Maryam Kalantari Saghafi2, Xiaoyan Pan3, Theodoros N Arvanitis4, and Andrew C Peet3
1Medical Physics, University Hospitals Birmingham NHS Foundation Trust, Birmingham, United Kingdom, 2School of Physics & Astronomy, University of Birmingham, Birmingham, United Kingdom,3Cancer Sciences, University of Birmingham, Birmingham, United Kingdom, 4Department of Electrical, Electronic, and Computer Engineering, University of Birmingham, Birmingham, United Kingdom

In-vivo 1H MRS can be used as a probe of temperature through its observed linear relationship with water chemical shift. However, such measurements are potentially subject to contributions from fast exchange effects that are dependent on factors such as macromolecular content and microstructure. Few if any studies have addressed the impact of these effects on MRS temperature calibrations. In this study, tissue-like phantoms have been constructed and used to test the effects of macromolecular concentration and dynamics on temperature measurements using 1H MRS, showing a significant linear relationship between the temperature calibrations and the agarose concentration.

Lorne Hofstetter1, Desmond Yeo1, W Thomas Dixon1, Cynthia Davis1, and Thomas K Foo1
1GE Global Research, Niskayuna, NY, United States

Accurate and stable MR thermometry is critical for interventional procedures such as RF hyperthermia and MR guided focused ultrasound therapy. In this work we present a 3-echo fat-referenced thermometry technique that reduces measurement error caused by time-varying changes in the underlying B0 field. This technique was validated in a cream cooling experiment (Capital Greek DeltaT = 8.4°C) where deviations between MR and fiber-optic temperature probe measurements were less than 0.28°C.

1771.   Hybrid Multibaseline and Referenceless PRF-Shift Thermometry Using Both Water and Fat Images 
William A Grissom1, Lorne W Hofstetter2, Viola Rieke3, Yoav Medan4, Kim Butts Pauly3, and Cynthia E Davis2
1GE Global Research, Munich, Germany, 2GE Global Research, Niskayuna, New York, United States, 3Radiology, Stanford University, Stanford, CA, United States, 4Insightec, Ltd, Tirat Carmel, Israel

Proton resonance frequency-shift thermometry is a promising technique to monitor thermal therapies in organs such as the breast and prostate, but is complicated by the presence of fat, organ motion, and the small size of these organs relative to typical hot spot sizes. While thermometry can be performed by suppressing fat, it can also be exploited as a reference to improve the separation of phase shifts caused by time-varying main field changes from temperature-induced phase shifts. We introduce an extension to the hybrid multibaseline subtraction and referenceless thermometry method that exploits the fat image as a reference to yield accurate temperature estimates that are robust to main field changes, large hot spot sizes, and motion in organs such as the prostate and breast that are surrounded by or contain fat.

1772.   Measurement of the T1 and T2 temperature dependence of human breast adipose tissue 
Paul Baron1, Roel Deckers1, Sara M Sprinkhuizen1, Laura G. Merckel2, Ronald L.A.W. Bleys3, Chris J.G Bakker1, and L W Bartels1
1Image Sciences Institute, University Medical Center Utrecht, Utrecht, Netherlands, 2Department of Radiology, University Medical Center Utrecht, Utrecht, Netherlands, 3Department of Anatomy, University Medical Center Utrecht, Utrecht, Netherlands

The aim was to assess the T1 and T2 temperature dependence of human adipose breast tissue and compare these with sunflower oil and pig fat. The temperature of tissue samples were increased by heating a water bath from 26.5°C to 72°C and then allowed to cool. During heating and cooling, the temperature was measured with a fiber optic probe and T1 and T2 were mapped. Reversible T1 changes but irreversible T2 changes were found for breast and pig fat. The T1-temperature dependence was similar for all three samples. T2 had a larger temperature dependence for pig than for breast fat.

1773.   Automatic B0 Drift Correction for MR Thermometry 
Eva Rothgang1,2, Jörg Roland3, Wesley D. Gilson2, Joachim Hornegger1, and Christine H. Lorenz2
1Pattern Recognition Lab, University Erlangen-Nuremberg, Erlangen, Germany, 2Center for Applied Medical Imaging, Siemens Corporate Research, Baltimore, MD, United States, 3Siemens Healthcare, Erlangen, Germany

PRF-derived temperature measurements are sensitive to patient motion and B0 drifts. The mean phase drift is often calculated from an area which is not heated and thus remains at reference temperature. However, this region can be difficult to place and its location and size highly influence the effectiveness of correction. On the contrary, we introduce a method which automatically corrects for B0 drift by determining the mean phase drift from all voxels which show a standard deviation smaller than a threshold the phase.

1774.   Correction of errors in PRFS Thermometry due to heat induced susceptibility changes of fat 
Paul Baron1, Roel Deckers1, Sara M Sprinkhuizen1, Chris J.G Bakker1, and L W Bartels1
1Image Sciences Institute, University Medical Center Utrecht, Utrecht, Netherlands

The aim was to correct susceptibility errors in Proton Resonance Frequency Shift (PRFS)-based thermometry caused by the heating of fat. The feasibility was shown in an oil/water phantom, cooled from 60 to 35°C . The susceptibility change in oil was calculated using T1-thermometry. The resulting field disturbance was calculated using the Fourier transform technique. The corrected PRFS change was calculated by subtracting the field disturbance from the measured PRFS change. The temperature was monitored with fiber optic probes. For two locations measured for the whole temperature range the mean absolute PRFS temperature error decreased by about one third when corrected.

1775.   Movement artifacts in monitoring the brain temperature during induction of mild hypothermia 
Jan Weis1, Lucian Covaciu2, Sten Rubertsson2, Mats Allers3, Anders Lunderquist3, Francisco Ortiz-Nieto1, and Håkan Ahlström1
1Department of Radiology, Uppsala University Hospital, Uppsala, Sweden, 2Department of Surgical Sciences, Anesthesiology and Intensive Care, Uppsala University Hospital, Uppsala, Sweden,3Department of Clinical Sciences, Division of Thoracic Surgry, University Hospital, Lund, Sweden

Brain temperature reductions (1-3 °C) were induced by intranasal cooling. Purpose of this study was to compare MRSI with high spatial and reduced spectral resolution and phase-difference technique that were used in monitoring the brain temperature changes during cooling. Both methods were sensitive to the slight involuntary movement (rotation) of the head. Random (reversible) and systematic (irreversible) movement artifacts were observed. Measurements in the transversal slices were more robust to the movement artifacts than those in sagittal planes.

Traditional Posters : Interventional Imaging
Click on to view the abstract pdf and click on to view the pdf of the poster viewable in the poster hall.
Interventional MRI: Preclinical Drug Delivery & Clinical Applications

Wednesday May 11th
Exhibition Hall  13:30 - 15:30

1776.   High-Resolution MRI of SPIO-labeled Yttrium Microsphere Biodistribution in the Rodent Liver at 7T 
Weiguo Li1, Zhuoli Zhang1, Daniel Procissi1, Andrew Gordon1, Jodi Nicolai1, Reed Omary1, and Andrew Larson1
1Department of Radiology, Northwestern University, Chicago, Illinois, United States

Radioembolization with Yttrium-90 (90Y) microspheres is a relatively new form of intra-arterial therapy for Hepatocellular carcinoma. However, visualization and quantification of 90Y microsphere biodistribution using conventional radiologic modalities is challenging. Whereas labeling 90Y microspheres with SPIOs offers the potential to use MRI to visualize in vivo biodistribution, optimization of the amount of SPIO included within these microspheres may be critical. In this study, we have demonstrated the potential to optimize SPIO content for future studies intended to quantify microsphere concentrations in vivo; we found that spheres with relatively low SPIO contents will be ideal candidates for future study.

1777.   Electro-nanotherapy Enhanced Delivery of Superparamagnetic Iron Oxide Nanoparticles in Liver Tumors: A Novel Means of Locoregional Drug Delivery 
Samdeep Mouli1, Noam Belkind1, Weiguo Li1, Jason Sandberg1, David Magill1, Rachel Klein1, Daniel Procissi1, Jodi Nicolai1, Yang Guo1, Andrew Larson1, and Reed Omary1
1Radiology, Northwestern University, Chicago, Illinois, United States

We describe a novel locoregional technique, termed electro-nanotherapy, to increase the intra-tumoral uptake of dual imaging and therapeutic nanoparticles through tissue electroporation. Our results demonstrate the procedure results in a 6 fold increase in liver tumor nanoparticle uptake over conventional systemic delivery. Furthermore, using high resolution MRI T2 and T2* maps, we are able to assess the real-time biodistribution of these nanoparticles non invasively.

1778.   A model for magnetic delivery of cells with an MRI scanner and its validation via confocal endoscopy 
Johannes Riegler1,2, Baptiste Allain3,4, Richard J Cook4, Quentin A Pankhurst5, and Mark F Lythgoe1
1Centre for Advanced Biomedical Imaging, University College London, London, United Kingdom, 2Centre for Mathematics and Physics in the Life Sciences and Experimental Biology (CoMPLEX), University College London, London, United Kingdom, 3Centre for Medical Image Computing (CMIC), University College London, London, United Kingdom, 4KCL Dental Institute, Biomaterials, Biomimetics and Biophotonics Group, Guy’s Hospital Campus, London, United Kingdom, 5Davy-Faraday Research Laboratory, The Royal Institution of Great Britain, London, United Kingdom

One of the major challenges for cell transplantation therapies is the spatial localization and tracking of cells over time. MRI has been used for cell tracking while magnetic delivery strategies using permanent magnets have been tested in animal models. MR gradient coils could potentially be used to steer magnetically labeled cells through the vascular system to their target. We show that steering of cells in a flow phantom is feasible. Following this, we derived a simple mathematical model which predicts that cell aggregation is an important factor explaining our results. Additionally we confirmed cell aggregation via confocal endoscopy.

1779.   Towards Translation of MRI-Detectable Hydrogels for Cell Therapy and Tissue Regeneration 
Bradley D Hann1, and Kevin M Bennett1
1School of Biological and Health Systems Engineering, Arizona State University, Tempe, Arizona, United States

A technique to noninvasively detect the macromolecular structure in hydrogels could be used to monitor cell viability and migration in vivo, and thus the efficacy of hydrogel-based cell therapies. Here we develop a technique to track structural changes in a biocompatible hyaluronic acid hydrogel doped with functionalized iron oxide nanoparticles. Changes in particle aggregation state can modulate T2. We measured T2 changes over time in vitro consistent with cellular rearrangement of the matrix and demonstrated that this technique can be used to detect cell proliferation in the hydrogel. We further report that these hydrogels can be visualized in vivo.

1780.   Pre-Procedural MRI and 3D Finite Element Modeling for Prediction of Irreversible Electroporation Ablation Zones in a Rat Liver Tumor Model 
Yue Zhang1,2, Haitham M Al-Angari3, Yang Guo2, Jodi Nicolai2, Rachel A Klein2, Alan V Sahakian3, Reed A Omary2,4, and Andrew C. Larson2,4
1Bioengineering, University of Illinois at Chicago, Chicago, IL, United States, 2Radiology, Northwestern University, Chicago, IL, United States, 3Electrical Engineering and Computer Science, Northwestern University, Evanston, IL, United States, 4Robert H. Lurie Comprehensive Cancer Center, Northwestern University, Chicago, IL, United States

Irreversible electroporation (IRE) has recently been applied as a novel tissue ablation modality; IRE involves application of short-lived electrical fields across the cell membrane to permanently increase membrane permeability leading to cell death. 2D finite element methods (FEM) are used to model anticipated electrical field distributions but these typically assume homogeneous tissue conductivity; heterogeneity could lead to poor approximations of subsequent ablation volume. In this work, we developed a 3D FEM approach using pre-procedural MRI measurements to produce a patients-specific 3D surrogate-conductivity map for simulation of IRE ablation zones in a rat model of hepatocellular carcinoma. Our results showed FEM-simulated ablation zones were well correlated to histology-confirmed ablation zones. Thus pre-procedural MRI and 3D FEM can be used to accurately predict IRE ablation zones.

1781.   Using statistical fiber anatomy in combination with electromagnetic field simulation in deep brain stimulation for improved characterization of specific target areas in tremor and Parkinson’s disease patients 
Burkhard Mädler1, Kaveh Mehdiani1, and Volker A. Coenen1
1Dep. of Neurosurgery, Div. of Stereotaxy and MR-based OR-Techniques, University Bonn, Bonn, Germany

DBS is a technique that delivers continuous electric stimulation through permanently into the brain implanted electrodes. Depending on diagnosis and symptoms, different anatomical targets have been chosen for stimulation in movement disorders, depression or obsessive compulsive disorders. Discussion to date focused mostly on the sole definition of DBS-targets with little debate about their important remote connectivity. We believe that it is this connectivity that might explain clinical improvement and side effects in distinct DBS procedures. Our study indicates that better target areas by means of specific WM-tracts might exist for various DBS-procedures.

1782.   Improved visualization of brain anatomy and function, for surgery, through real-time non-rigid registration 
Arne Hans1, Adam Wittek2, Grand Joldes2, Karol Miller2, Neil I Weisenfeld1, Mark Alexiuk3, John Saunders3, Einat Liebenthal4, Garnette R Sutherland5, and Simon K Warfield1
1Radiology, Children's Hospital Boston and Harvard Medical School, Boston, MA, United States, 2University of Western Australia, Perth, Australia, 3IMRIS, Winnipeg, Canada, 4National Research Council Canada, Canada, 5University of Calgary

We propose to significantly increase the intraoperative utility of data acquired preoperatively by compensating, in real time, for brain shift during surgery. This is demonstrated on craniotomy case data that has been processed using our non-rigid registration pipeline. We have achieved intraoperative visualization of preoperative fMRI and DTI aligned to intraoperative MRI, and we have validated the alignment quality by comparing automatically generated edges. Our study shows that preoperative data can be warped to the current configuration of the patient's brain in real time and with subvoxel accuracy. Such visualization may dramatically improve surgical decision making.

1783.   MR-guided percutaneous lumbar mechanical disc decompression 
Christian Jürgen Seebauer1, Jens Rump2, Hermann Josef Bail3, Felix Güttler2, Bernd Hamm2, Carsten Perka4, Christian Gross4, and Ulf Teichgräber2
1Center for Musculoskeletal Surgery, Charité-Universitätsmedizin Berlin, Berlin, Berlin, Germany, 2Department of Radiology, Charité-Universitätsmedizin Berlin, Berlin, Berlin, Germany,3Department of Trauma and Orthopedic Surgery, Clinic Nuremberg, Nuremberg, Germany, 4Center for Musculoskeletal Surgery, Charité-Universitätsmedizin Berlin

In recent years, a number of minimally invasive nuclear decompression techniques for lumbar disc prolapse have been introduced. Partial removal of the nucleus has been shown to decompress herniated discs, relieving pressure on nerve roots and, in some cases, offering relief from disc pain. Most spine procedures have traditionally been performed using fluoroscopic or CT guidance. With the increasing role of MRI in diagnosis of musculoskeletal conditions, clinicians have been eager to explore the possibility of using MR guidance for musculoskeletal procedures. The aim of this study was to evaluate feasibility and practice of MR-guided percutaneous lumbar mechanical disc decompression in an experimental setting in 3 human cadavers.

1784.   Development of a MR-compatible cardiotocograph for the non-invasive assessment of the birth process via MRI. 
Andreas Heinrich1, Jens Rump1, Felix Güttler1, Christian Seebauer2, Bernd Hamm1, and Ulf Teichgräber1
1Department of Radiology, Charité-Universitätsmedizin Berlin, Berlin, Berlin, Germany, 2Center for Musculoskeletal Surgery, Charité-Universitätsmedizin Berlin, Berlin, Berlin, Germany

For a non-invasive assessment of the birth process under MR control, an MR-compatible cardiotocograph (CTG) was developed and tested for a safe monitoring of physiological parameters (heart rate, uterine contraction). Voltages generated by the MRI led to disturbances of heart rate data, whereas uterine contraction data were minor influenced. The effects of spoiled and balanced gradient-echo sequences on CTG was examined. Disturbances caused by MRI mainly depends on repetition time (TR). In order to overcome this, a MR-noise-filter (TR-dependend frequency comb filter and a low pass filter) was developed and analyzed. As a result, the fetal heart rate as well as the uterine contraction could be assessed clearly during MR image acquisition.