Electronic Posters : Interventional Imaging
Click on to view the abstract pdf and click on to view the video presentation.
MR Guided Focused Ultrasound, Thermotherapy & Thermometry
Monday May 9th
Exhibition Hall  14:00 - 16:00 Computer 63

14:00 3715.   An MR-compatible preclinical sonication platform for focused ultrasound therapy and monitoring in animal models 
Adam Christian Waspe1,2, Meaghan O'Reilly1, Jiawen Zhang1, Yaseen Khan1, Anthony Chau1, Rajiv Chopra1,2, and Kullervo Hynynen1,2
1Imaging Research, Sunnybrook Health Sciences Centre, Toronto, ON, Canada, 2Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada

A preclinical sonication platform has been developed for focused-ultrasound therapy and monitoring in animal models. A spherically-focused transducer is submerged within a closed water tank and is mechanically steered by an MR-compatible three-axis robotic positioner. The positioner can rapidly raster the transducer to multiple targets with a 1 Hz repetition frequency, enabling high-throughput animal investigations. An onboard RF power meter and piezoelectric hydrophone enable the monitoring of acoustic emissions during the sonication process, which provides insight into the ultrasound bioeffects occurring in vivo. This platform enables high throughput ultrasound enhanced therapy and monitoring involving large numbers of small animals.

14:30 3716.   A Temperature Dependent Perfusion Rate Model for Simulating Temperature Evolution in Tissue for Magnetic Resonance Imaging guided High Intensity Focused Ultrasound (MR-HIFU) Therapy: Initial Experience in a Pig Model 
Jiming Zhang1, Pei-Herng Hor1, John Fischer2, Ari Partanen3, Tiina Karjalainen3, and Raja Muthupillai2
1Department of Physics and Texas Center for Superconductivity, 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

We propose a theoretical model utilizing a temperature dependent perfusion term for simulating the temperature evolution during and following MR-HIFU therapy in a pig model. The results from the theoretical model match closely with experimental observations. Key insights from our study are the following: (a) Local tissue perfusion responses in MR-HIFU are much dynamic than what has been reported in hyperthermia applications; (b) A temperature dependent perfusion term is necessary for adequately modeling the temperature evolution in MR-HIFU, and (c) Tissue perfusion response to MR-HIFU must be taken into account in clinical HIFU therapy planning and optimization

15:00 3717.   Real-time Monitoring of Temperature and Magnetization Transfer during HIFU Transmission and Long-term Follow-up of Magnetization Transfer Effect : in vivo rabbit investigations 
Hsu-Hsia Peng1, Teng-Yi Huang2, Wei-Min Tseng2, Yu-Hui Ding3, Hsiao-Wen Chung4, Wen-Shiang Chen3, and Wen-Yih Isaac Tseng5
1Dept. of Biomedical Engineering and Environmental Sciences, National Tsing Hua University, Hsinchu, Taiwan, 2Department of Electrical Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan, 3Department of Physical Medicine and Rehabilitation, National Taiwan University Hospital, Taipei, Taiwan,4Department of Electrical Engineering, National Taiwan University, Taipei, Taiwan, 5Center for Optoelectronic Biomedicine, Medical College of National Taiwan University, Taipei, Taiwan

An imaging sequence, which simultaneously monitors temperature change and magnetization transfer (MT) contrast, was applied on in vivo rabbit thigh muscle during HIFU sonicaiton. After sonication, T2WI, FLAIR images, and 3D MT images were acquired for long-term investigations of heated region. On the MTR maps, the surrounded tissue with low MTR delineates clearly the extent of heated region, underlining the advantage of long-term follow-up with usage of MT effect. In conclusion, real-time monitoring of temperature and MT mapping during HIFU sonication is an effective technique to evaluate the long-term follow-up of tissue damage following HIFU treatment.

15:30 3718.   Thermal ablative lesions in sheep’s renal cortex using respiratory gated MRgHIFU: spatial accuracy and complications 
Lorena Petrusca1, Magalie Viallon1, Thomas Goget1, Denis Morel2, Xavier Montet1, Vincent Auboiroux1, Sylvain Terraz1, Christoph D Becker1, and Rares Salomir1
1Radiology Department, University Hospitals of Geneva, Geneva, Switzerland, 2Anesthesiology, University Hospitals of Geneva, Geneva, Switzerland

An in vivo study on sheep’s kidney is described here, demonstrating the capability to produce sharply delineated thermal ablations in the renal cortex. Elementary sonications were performed at prescribed locations in the renal cortex using an optoelectronic respiration sensor to trigger the HIFU beam and the multi-planar MR-thermometry. The results obtained showed circular homogenous regions of thermal ablation and were confirmed by kinetic curves taken after the administration of Gd-based contrast agent bolus and also by post-mortem histological analysis. A careful evaluation of the side-effects by MR-thermometry monitoring in 3 orthogonal planes and semi-chronic follow up is mandatory to assess regional biologic reactions and lesions.

Tuesday May 10th
  13:30 - 15:30 Computer 63

13:30 3719.   Volumetric MRgHIFU Rapid Ablation: In vivo Demonstration of Non-Parametric Automatic Temperature Control 
Lorena Petrusca1, Magalie Viallon1, Thomas Goget1, Denis Morel2, Vincent Auboiroux1, Sylvain Terraz1, Christoph Becker1, and Rares Salomir1
1Radiology Department, University Hospitals of Geneva, Geneva, Switzerland, 2Anesthesiology, University Hospitals of Geneva, Geneva, Switzerland

A new automatic, non-parametric temperature controller, using non-linear negative reaction, was designed and validated, for the delivery of an equivalent thermal dose at every sonicated point during volumetric MRgHIFU. Its convergence was simulated and found to be suitable for fast volumetric sonications. Accurate control of the temperature of all foci situated in the HIFU trajectory was also in-vivo demonstrated in sheep thigh muscle for line-scan and circular-scan trajectories. The thermal history of all foci was found to be systematically similar: an initial rising-temperature, followed by a steady-state regime once the prescribed temperature was reached. Accurate performance was demonstrated without requiring a priori knowledge of tissue thermo-acoustic parameters.

14:00 3720.   Model-Predictive Controller using MR Thermometry for Dynamic Optimization of Heating/Cooling Pulses for HIFU Therapies 
Joshua de Bever1,2, Allison Payne1, Nick Todd1, and Robert Roemer3
1Utah Center for Advanced Imaging Research, University of Utah, Salt Lake City, Utah, United States, 2School of Computing, University of Utah, 3Department of Mechanical Engineering, University of Utah, Salt Lake City, Utah, United States

A novel model-predictive controller that leverages Magnetic Resonance Temperature Imaging to guide High Intensity Focused Ultrasound (HIFU) cancer therapies has been implemented and tested in vivo. The controller reduces treatment time by optimizing individual pulse heating and cooling times while guaranteeing treatment safety. The clinician retains full supervisory control while leveraging a computer's ability to rapidly monitor and adjust many parameters simultaneously.

14:30 3721.   MRI Motion Compensation by Positional Ultrasound Biometrics 
Benjamin Schwartz1, and Nathan McDannold2,3
1Biophysics, Harvard University, Boston, MA, United States, 2Radiology, Harvard Medical School, Boston, MA, United States, 3Radiology, Brigham and Women's Hospital, Boston, MA, United States

In previous work, our group and others have demonstrated the use of ultrasound measurements for MR motion compensation, in a manner analogous to classic MR navigator echoes. Existing implementations can only measure shifts parallel to the collimated ultrasound beam. We demonstrate an alternative approach that can track motion perpendicular to the beam axis. The new system employs a biometric training stage in which MRI and ultrasound data are acquired simultaneously. We have demonstrated both retrospective and prospective motion compensation in phantoms. Future work include tests for breath motion compensation in animal models and human subjects.

15:00 3722.   Model Based Correction of Triggered MR Thermometry for LITT 
Joshua P Yung1,2, Florian Maier3, David Fuentes1, Axel J Krafft3, Andrew Elliott1, Michael Bock3, John D Hazle1,2, Wolfhard Semmler3, and R Jason Stafford1,2
1Department of Imaging Physics, University of Texas M.D. Anderson Cancer Center, Houston, TX, United States, 2The University of Texas Graduate School of Biomedical Sciences, Houston, TX, United States, 3Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany

In MR-guided thermal therapies, MR temperature imaging is obtained by using the PRF shift method, which relates temperature changes to the phase difference. Thus, interscan motion and temperature artifacts become an issue with this method. In this work, periodic motion is applied to an ex vivo phantom during heating. After applying a velocity navigator triggering pulse sequence, which synchronizes the temperature acquisition with the periodic motion, a Pennes bioheat model-based Kalman filter corrected errors and improved the temperature monitoring, which may allow for a more safe and efficient treatment in targets with inherent breathing motion.

Wednesday May 11th
  13:30 - 15:30 Computer 63

13:30 3723.   Measuring temperature rise during spin echo MR-ARFI acquisition 
Elena Kaye1, and Kim Butts Pauly2
1Electrical Engineering, Stanford University, Palo Alto, CA, United States, 2Radiology, Stanford University, Palo Alto, CA, United States

This study demonstrates a method for simultaneous monitoring of temperature rise during spin echo based MR - ARFI acquisitions. An additional readout gradient was inserted after the excitation pulse in order to enable gradient echo acquisition. Temperature rise was measured using the gradient echo phase difference images for a range of FUS acoustic power levels.

14:00 3724.   MR-Acoustic Radiation Force Mapping can Quantitatively Predict Drug Delivery following Ultrasound-Induced Blood Brain Barrier Disruption in Rodents 
Benoit Larrat1, Benjamin Marty1, Mathieu Pernot2, Mickael Tanter2, Franck Lethimonnier1, and Sébastien Mériaux1
1CEA/DSV/I2BM/Neurospin, Paris, France, 2Institut Langevin - ESPCI Paristech, INSERM U979

In this work, blood brain barrier was opened in rats using focusing ultrasound under 7T MRI guidance. Displacements induced by the acoustic radiation force were imaged with a motion sensitized sequence. After injection of a Gd chelate contrast agent, T1 maps were acquired from which quantitative Gd concentration images were derived. The relationship between acoustic intensity and penetration of contrast agent in cerebral tissue was investigated. Our data show that radiation force imaging is an efficient guiding tool to adjust the quantity of delivered drug or contrast agent with ultrasound induced blood brain barrier disruption.

14:30 3725.   Blood-brain barrier disruption in nonhuman primates using a clinical MRI-guided focused ultrasound system: preliminary results 
Nathan McDannold1, Costas D. Arvanitis1, Natalia Vykhodtseva1, and Margaret S. Livingstone2
1Radiology, Brigham & Women's Hospital, Harvard Medical School, Boston, MA, United States, 2Neurobiology, Harvard Medical School, Boston, MA, United States

Preliminary findings from a safety study in non-human primates of targeted blood-brain barrier disruption (BBBD) are presented. BBBD was produced via burst sonications produced by a clinical MR-guided focused ultrasound system combined with a circulating microbubble agent. We found that it was possible to produce localized volumes of BBBD in gray matter without MRI-evident brain tissue damage or effects in the ultrasound beam path. MR contrast enhancement was not detected in white matter targets, perhaps due to its relative paucity of blood vessels. While more work is needed, these preliminary results are encouraging for moving this technology to patients.

15:00 3726.   Pain control in patients with locally advanced pancreatic carcinoma using High Intensity Focused Ultrasound under 3T MR Guidance. Results from a single center preliminary experience. 
Alessandro Napoli1, Beatrice Cavallo Marincola1, Michele Anzidei1, guendalina Menichini1, Gaia Cartocci1, Carlo Catalano1, and Roberto Passariello1
1Radiological Sciences, Policlinico Umberto I, Rome, Italy

MRgFUS represents a promising non-invasive treatment modality for successful palliation and control of pain in patients with pancreatic neoplasms.

Thursday May 12th
  13:30 - 15:30 Computer 63

13:30 3727.   Assessing thermal tissue damage with biexponential Diffusion-Weighted MRI 
Valentina Giannini1,2, Pejman Ghanouni3, Graham Sommer3, Chris Diederich4, Andrew Holbrook3, Vasant Salgaonkar4, Punit Prakash4, Harcharan Gill5, Donna Bouley6, and Kim Butts Pauly3
1Radiology, FPRC, Candiolo, TO, Italy, 2Radiology, Stanford University, Stanford, Ca, United States, 3Radiology, Stanford University, Stanford, CA, United States, 4Radiation Oncology, University of California, San Francisco, San Francisco, Ca, United States, 5Urology, Stanford University, Stanford, CA, United States, 6Comparative Medicine, Stanford University, Stanford, CA, United States

In this study, we want to assess the use of DWI images to estimate prostate tissue damage during HIFU ablation, by measuring diffusion coefficients of canine prostate pre and post ablated, using multiple b-factors ranging up to 3500 s/mm2. EPI DWI images were collected before and after the ablation, with 12 different b values from 0 to 3500 s/mm2, and with a tetrahedral encoding scheme. This study demonstrates changes in the fast and slow diffusion rates and fractions after thermal ablation. In addition, differences in the diffusion rates in heat fixed vs. non-heat fixed ablated tissue are demonstrated.

14:00 3728.   Comparing different drug carriers for dynamic absolute MR thermometry 
Roel Deckers1, Sara M Sprinkhuizen1, Marina Talelli2, Bart Crielaard2, Hans Ippel3, Rolf Boelens3, Twan Lammers2,4, Chris J Bakker1, Gert Storm2, and Lambertus W Bartels1
1Image Sciences Institute, University Medical Center Utrecht, Utrecht, Utrecht, Netherlands, 2Department of Pharmaceutics, Utrecht Institute for Pharmaceutical Sciences, 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 control of hyperthermia in local drug delivery applications. We compared different drug carriers that provide a temperature insensitive proton resonance frequency (PRF) that can serve as reference for the temperature sensitive PRF of water. The frequency difference between both PRFs is a measure of the absolute temperature and can be measured with NMR spectroscopy or multi-Gradient Echo (mGE) sequence. The influence of the drug carrier composition and the pH on the NMR signal are measured and the accuracy and sensitivity of the mGE method are investigated.

14:30 3729.   A Novel Imaging Approach Employing a plus-or-minus sign90°-preparation for Fast PRF-based MR Thermometry 
Axel Joachim Krafft1, Florian Maier1, Jaane Rauschenberg1, Joshua P Yung2, Jürgen Walter Jenne3,4, Wolfhard Semmler1, and Michael Bock1
1Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany, 2Imaging Physics, University of Texas M.D. Anderson Cancer Center, Houston, Texas, United States, 3Mediri GmbH, Heidelberg, Germany, 4Clinical Clinical Cooperation Unit Radiation Oncology, German Cancer Research Center (DKFZ), Heidelberg, Germany

MR temperature mapping is an indispensable tool for thermal therapies. The most widely used thermometry technique employs temperature induced shifts of the proton resonance frequency (PRF). Spoiled gradient echo (GRE) techniques in combination with long echo times are commonly used to detect the small PRF shifts by the subtraction of phase images. In this work, we present a novel imaging strategy for PRF-based thermometry employing a plus-or-minus sign90°-magnetization preparation to convert temperature related phase changes into a modulation of the longitudinal magnetization. The obtained signal modulation can be detected with fast GRE sequence, and thus, a short TA can be achieved.

15:00 3730.   Kalman Filtered MR Temperature Imaging 
David Fuentes1, Joshua Yung1, Andrew Elliott1, John D Hazle1, and Roger Jason Stafford1
1Imaging Physics, MD Anderson Cancer Center, Houston, TX, United States

The presented work critically evaluates the ability of a Kalman Filtered MR thermal image acquisition scheme to accurately monitor a LITT procedure in the presence of corrupt or missing data. Details of the finite element-based stochastic form of the Pennes bioheat transfer model needed to achieve real-time performance within the Kalman framework are discussed. The ability to provide a robust temperature estimate in presence of data corruption was quantitatively evaluated in terms of an L2 (RMS) norm of the error. Results indicate the developed algorithm may provide a useful model-based estimate of the temperature state during a LITT procedure.

Electronic Posters : Interventional Imaging
Click on to view the abstract pdf and click on to view the video presentation.
Interventional MRI: Cardiovascular Applications

Monday May 9th
Exhibition Hall  14:00 - 16:00 Computer 64

14:00 3731.   Assessment of the Transmural Extent of Acute Atrial Lesions using Electrogram Amplitude vs. LGE-MRI 
Sathya Vijayakumar1,2, Eugene G Kholmovski1,2, Ravi Ranjan2,3, Gene Payne1,2, Joshua Blauer2,4, Kamal Vij5, Nelly A Volland1,2, Gaston Vergara2,3, Kimberly Johnson2,3, Gregory Gardner4,6, Steven Shea7, Sunil Patil7, Julien Barbot7, Christopher J McGann2,3, Peter Piferi5, Christine Lorenz7, Rob MacLeod2,4, and Nassir F Marrouche2,3
1UCAIR, Department of Radiology, University of Utah, Salt Lake City, Utah, United States, 2CARMA Center, University of Utah, Salt Lake City, Utah, United States,3Department of Cardiology, University of Utah, Salt Lake City, Utah, United States, 4SCI Institute, University of Utah, Salt Lake City, Utah, United States, 5SurgiVision Inc., Irvine, CA, United States, 6Dept. of BioEngineering, University of Utah, Salt Lake City, Utah, 7Center for Applied Medical Imaging, Siemens Corporate Research, Princeton, NJ, United States

In this work we have shown that under identical conditions of RF ablation of atrial wall, two types of injuries could be created. The first type was a very prominent transmural lesion, while the second type was superficial injury to the endocardial surface of the atrium. Although similar reduction in electrogram amplitude was observed for both types of lesions, the LGE-MR images were very different. LGE-MRI has the potential to accurately assess acute atrial lesions.

14:30 3732.   Characterization of acute atrial lesions by late gadolinium enhancement MRI 
Eugene G. Kholmovski1,2, Sathya Vijayakumar1,2, Christopher J McGann2,3, Joshua Blauer2,4, Ravi Ranjan2,3, Gaston Vergara2,3, Gene Payne1,2, Nelly Volland1,2, Rob MacLeod2,4, and Nassir F Marrouche2,3
1UCAIR, Department of Radiology, University of Utah, Salt Lake City, Utah, United States, 2CARMA Center, University of Utah, Salt Lake City, Utah, United States,3Department of Cardiology, University of Utah, Salt Lake City, Utah, United States, 4SCI Institute, University of Utah, Salt Lake City, Utah, United States

Serial LGE-MRI detects two distinct enhancement patterns in ablated regions of atrial wall. Lesion core identified by no-reflow in early LGE and enhancement in very late LGE has very slow contrast dynamics, whereas the regions around the lesion core (edema) have relatively fast contrast dynamics. This obvious difference in contrast dynamics can be exploited to discriminate permanent injury from transient ones. High correlation between lesion measurements made ex-vivo and the original no-reflow or very delayed enhancement shows that LGE-MRI acquired at the right time after contrast injection can be a reliable predictor of permanent scar.

15:00 3733.   MR-Guided Endocardial Local Activation Time Map During Programmed Stimulation 
Samuel O Oduneye1, Labonny Biswas2, Stefan Pintilie2, Venkat Ramanan2, Jennifer Barry2, Tawfiq Zeidan Shwiri3, Ehud Kadmon3, Eugene Crystal3, and Graham A Wright1
1Medical Biophysics, University Of Toronto, Toronto, Ontario, Canada, 2Imaging Research, Sunnybrook Research Institute, Toronto, Ontario, Canada, 3Arrhythmia Services, Sunnybrook Health Science Centre, Toronto, Ontario, Canada

We have previously presented an MR-compatible EP system designed for real-time MR imaging able to directly locate and characterize electrical properties of potential arrhythmogenic regions in the left ventricle (LV). Here we present our initial experience of ventricular endocardial local activation time (LAT) mapping during programmed stimulation performed in several porcine models.

15:30 3734.   Atrial Thickness Mapping for EP Ablation using Black-Blood Restricted Field of View MRI 
Peter Koken1, Ronald Holthuizen2, Sascha Krueger1, Harald Sepp Heese1, Steffen Weiss1, Jouke Smink2, Reza Razavi3, and Tobias Schaeffter3
1Philips Research Laboratories, Hamburg, Germany, 2Philips Healthcare, Best, Netherlands, 3Division of Imaging Sciences, King's College, London, United Kingdom

The treatment of cardiac arrhythmias by RF ablation has grown recently. Knowledge of atrial wall thickness can provide information for more accurate RF ablation power settings, which may result in better transmural lesions. In this work, we propose the use of a set of small, localized scans with high resolution along the direction perpendicular to the atrial wall to provide accurate thickness information at separate locations on the atrial wall. A segmented 3D surface of the left atrium is used to plan the perpendicular beams. An interpolation algorithm is used to calculate a thickness map for the whole left atrium.

Tuesday May 10th
  13:30 - 15:30 Computer 64

13:30 3735.   Visualization platform for real-time, MRI-guided cardiac interventions 
Stefan Pintilie1, Labonny Biswas1, Samuel Oduneye1, Kevan Anderson1, Graham A. Wright1,2, and Perry E. Radau1
1Imaging Research, Sunnybrook Hospital, Toronto, Ontario, Canada, 2Medical Biophysics, University of Toronto, Toronto, ON, Canada

Guidance of electrophysiological (EP) procedures by MRI is attractive compared with x-ray fluoroscopy because MRI has good tissue contrast and can be used to visualize arrhythmogenic regions of heterogeneous scar and healthy tissue (“gray zone”). The Vurtigo software presented here is designed to enhance guidance of radio-frequency (RF) ablation therapies with visualization of a prior volume roadmaps, tracked catheters and EP recordings. The open source, cross-platform, free software is extensible with plug-ins and is computationally efficient with GPU accelerated graphics and threading.

14:00 3736.   Real-Time MR-Guided Transarterial Aortic Valve Implantation (TAVI): In vivo Evaluation in Swine 
Harald H. Quick1,2, Philipp Kahlert3, Holger Eggebrecht3, Gernot M. Kaiser4, Nina Parohl2, Juliane Albert2, Lena Schäfer2, Ian McDougall5, Brad Decker5, Raimund Erbel3, and Mark E. Ladd2
1Institute of Medical Physics, University of Erlangen-Nürnberg, Erlangen, Germany, 2Department of Diagnostic Radiology, University Hospital Essen, Essen, Germany,3Department of Cardiology, University Hospital Essen, Essen, Germany, 4Department of Transplantation Surgery, University Hospital Essen, Essen, Germany, 5Evasc Medical Systems, Vancouver, BC, Canada

Transcatheter, transarterial aortic valve implantation (TAVI) is rapidly emerging as a promising new treatment option for patients with severe symptomatic aortic valve stenosis. In this study, the MR imaging characteristics of a commercially available TAVI prosthesis were systematically investigated in vitro and its delivery catheter was subsequently modified towards MR-compatibility. Featuring the modified MR compatible delivery catheter, real-time MR guided TAVI has been successfully performed in vivo in 6/8 swine. MR imaging provided excellent pre-interventional anatomic and functional evaluation of the native aortic valve, precise real-time instrument guidance, and finally detailed post-interventional evaluation of therapeutic success.

14:30 3737.   XFM-Guided Approach to Intrapericardial Delivery of Cardiac Therapeutics 
Nicole Azene1,2, Yingli Fu1, Tina Ehtiati3, Aaron Flammang3, Dorota Anna Kedziorek1, Jens Guehring4, Wesley D. Gilson3, Judy Cook1, Clifford R Weiss1, Kathleen L Gabrielson2, Peter V Johnston5, and Dara L Kraitchman1
1Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States, 2Molecular & Comparative Pathobiology, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States, 3Siemens Corporate Research, Baltimore, Maryland, United States, 4Siemens Corporate Research, Erlangen, Germany, 5Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States

Traditionally, cardiac cellular therapeutics have been delivered directly to the myocardium or coronary vasculature. An intrapericardial (IP) approach would potentially provide a method for long-term retention of stem cells. In the current study, the feasibility of a fused X-ray-magnetic resonance imaging (XFM) method was explored for delivery of an X-ray visible barium-alginate microcapsule (BaCaps) in swine. XFM-guidance was shown to enhance safety, e.g., provide enhanced soft tissue detail and vessel anatomy, and improve biocompatibility of BaCap delivery. Thus XFM IP delivery of cardiac therapeutics shows promise for the use of BaCaps for allogenic stem cell delivery.

15:00 3738.   Virtual Dye Angiography: using endogenous contrast to visualize blood flow in MRI-guided interventional procedures 
Ashvin Kurian George1, Anthony Z Faranesh1, Kanishka Ratnayaka1, J Andrew Derbyshire1, Robert J Lederman1, and Michael S Hansen1
1National Institutes of Health, Bethesda, Maryland, United States

We introduce a method for non-invasive selective “angiography” during MRI-guided interventional procedures. The method uses 2D selective excitations and saturations to label a volume of blood upstream of the region of interest. The saturation module is seamlessly integrated into a standard real-time SSFP sequences and can be enabled and controlled interactively. Blood flow is visualized either by imaging the region containing the saturation volume directly or, similar to digital subtraction angiography, by computing the difference with an ECG-synchronized image of the same region without saturation. We present initial results in animals.

Wednesday May 11th
  13:30 - 15:30 Computer 64

13:30 3739.   Online Automated Generation of an Aortic Model for MR Guided Interventions 
Nils Karlsson1, Klaus J Kirchberg2, Li Pan1, Aaron J Flammang1, Christine H Lorenz1, and Wesley Gilson1
1Center for Applied Medical Imaging, Siemens Corporation, Corporate Research, Baltimore, MD, United States, 2Center for Applied Medical Imaging, Siemens Corporation, Corporate Research, Princeton, NJ, United States

In the context of virtual endoscopy we present and validate a method for automatically creating a 4D model of the human aorta from arbitrary real-time MR slices. An aorta model of a healthy volunteer was created and validated against a set of high-resolution cine images of the same subject.

14:00 3740.   3D Aortic Motion Estimation for Image-Guided Intervention 
Rachel E Clough1, Christian Buerger1, Christoph Kolbitsch1, Markus Henningsson1, Peter Taylor1, Claudia Prieto1, and Tobias Schaeffter1
1Division of Imaging Sciences and Biomedical Engineering, King's College London, Westminster Bridge Road, London, United Kingdom

Endovascular repair is now the method of choice for treatment of thoracic aortic disease. The complexity of the procedure is related to the anatomy of the aortic arch and accurate catheter navigation, cannulation and precise device placement in each of the individual branches. XMR provides enhanced image guidance but requires high fidelity roadmaps incorporating physiological cardiac and respiratory motion. In this work we quantify the 3D motion of the aorta caused by both cardiac and respiratory displacement and evaluate the accuracy of affine and non-rigid motion correction approaches for MR-guided intervention.

14:30 3741.   Intra-Cardiac MRI Catheter for EP Ablation Monitoring: Preliminary Studies 
Ehud J Schmidt1, Lei Qin1, Juan Santos2, Gregory F Michaud3, Raymond K Kwong3, Kim Butts-Pauly4, William G Stevenson3, and Charles L Dumoulin5
1Radiology, Brigham and Womens Hospital, Boston, MA, United States, 2CardioVista Inc., Palo Alto, CA, United States, 3Cardiology, Brigham and Womens Hospital, Boston, MA, United States, 4Radiology, Stanford University, Palo Alto, CA, United States, 5Radiology, Cincinatti Childrens Hospital, Cincinatti, OH, United States

A novel 2nd generation intra-cardiac MRI (ICMRI) catheter was developed. This catheter incorporates a 4-microcoil mr-tracking array and a loop coil. All components are placed on a plastic mesh which is maintained folded and can be expanded using a push-pull mechanism to full size, where the tracking array becomes tetrahedral in shape, allowing for accurate detection of position/orientation and the loop coil is extended to 2-cm diameter. The catheter has a 3-mm lumen, so it can be used mounted an electro-physiology radio-frequency ablation catheter. The SNR of the catheter and its use in a swine heart are demonstrated.

15:00 3742.   System for real-time cardiac MRI gating, 12-lead ECG monitoring, and non-invasive stroke volume estimation 
Zion Tsz Ho Tse1, Charles L Dumoulin2, Gari Clifford3, Michael Jerosch-Herold1, Daniel Kacher1, Raymond Kwong4, William Gregory Stevenson4, and Ehud Jeruham Schmidt1
1Radiology, Brigham and Women's Hospital, Boston, MA, United States, 2University of Cincinnati College of Medicine, Cincinnati, OH, United States, 3Department of Engineering Science, University of Oxford, Oxford, United Kingdom, 4Cardiology, Brigham and Women's Hospital, Boston, MA, United States

A real-time MRI-compatible 12-lead ECG monitoring system was developed, based on a modified digital ECG system connected to a strong processing platform, which performed a novel 3-D QRS-complex detection algorithm in <5ms, as well as adaptive filtering to remove Magneto-Hydro-Dynamic (MHD) voltages. The system was tested in 1.5T and 3T MRIs on 7 subjects (5 volunteers and 2 arrhythmia patients). Results showed high-fidelity MHD-free ECGs, with restoration of the true S-T segment signal for ischemia monitoring, and reliable QRS complex detection for scanner triggering. Non-invasive beat-to-beat stroke volume estimations were derived from time-integration of systolic MHD voltages.

Thursday May 12th
  13:30 - 15:30 Computer 64

13:30 3743.   Dephased Double Echo Imaging with Outer Volume Suppression for Accelerated White Marker Imaging in MR-guided Interventions 
Axel Joachim Krafft1, Alexander Brunner1, Jaane Rauschenberg1, Joachim Pfeffer2, Klaus Düring2, Wolfhard Semmler1, and Michael Bock1
1Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany, 2MaRVis Technologies GmbH, Aachen, Germany

The localization of passive markers in MR-guided interventions, espcially in intravascular applications, can be hampered due to image atrifacts arising from motion and blood flow. Recently, a double echo (DE) sequence was proposed acquiring a conventional spoiled GRE image and an additional dephased image depicting passive marker materials with a positive contrast. As two echoes have to be collected within one TR-interval, reduction of the total acquisition time is challenging. In this study, we combined the DE imaging technique with outer volume suppression to enable accelerated white marker imaging by means of a highly restricted FOV in phase-encoding direction.

14:00 3744.   PRESSURE GRADIENT PREDICTION IN AORTIC COARCTATION USING A COMPUTATIONAL-FLUID-DYNAMIC (CFD) MODEL: Validation against invasive pressure catheterization at rest and pharmacological stress 
Israel Valverde1, Cristina Staicu2, Alberto Marzo2, Heynric Grotenhuis3, Kawal Rhode1, Yubing Shi2, Aphrodite Tzifa1, Reza Razavi1, Patricia Lawford2, Rod Hose2, and Philipp Beerbaum1
1Imaging Sciences, King's College London, London, United Kingdom, 2Department of Cardiovascular Science, Medical Physics Group, University of Sheffield, Sheffield, United Kingdom, 3Leiden University Medical Centre, Leiden, Netherlands

Current clinical evaluation of aortic coarctation commonly involves the use of invasive catheterization to determine the pressure gradient at rest and during pharmacological stress.The goal of the present study is to investigate the feasibility of using patient-specific computational-fluid-dynamic simulations to predict the pressure drop.The patient-specific vascular anatomy and flow data required as boundary were extracted from magnetic resonance studies(CMR).Our preliminary results are encouraging,predicting accurately the pressure drop at rest and giving an indication of the severity during stress.This is the first step towards a patient-specific CMR assessment to predict hemodynamic conditions in the aorta,avoiding invasive catheterization and ionizing radiation.

14:30 3745.   Accurate catheter tip tracking for MR-Guided EP procedures using realtime active detuning 
Venkat Ramanan1, Samuel O Oduneye2, Labonny Biswas1, Stefan Pintilie1, and Graham A Wright1,2
1Sunnybrook Research Institute, Toronto, Ontario, Canada, 2Medical Biophysics, Sunnybrook Research Institute, Toronto, Ontario, Canada

MR-guided electrophysiological procedures require precise localization of tips of catheters. However the microcoils in the catheter tips couple with the surface coil(s) leading to larger sensitivity volumes for the microcoil. This results in poor tracking of the catheter tip both in accuracy and temporal stability. We propose a method for decoupling catheter and surface coil(s), operator controlled realtime active detuning, which allows us to track accurately at high frame rates while also facilitating realtime imaging using surface coils. Our technique was tested in phantoms and pigs and was found to work well. It is currently incorporated in our MR-guided EP pig experiments.

15:00 3746.   Prospective motion correction for intra-cardiac 3D delayed enhancement MRI using an MR-Tracking Tetrahedron 
Lei Qin1, Ehud J Schmidt1, Juan Santos2, W Scott Hoge1, Clare Tempany-Afdhal1, Kim Butts-Pauly3, William G Stevenson4, and Charles L Dumoulin5
1Radiology, Harvard Medical School, Boston, MA, United States, 2Heart Vista, Inc, Palo Alto, CA, 3Radiology, Stanford University, 4Cardiology, Harvard Medical School,5Radiology, Cincinnati Childrens' Hospital

Intra-cardiac imaging coils provided a higher signal-to-noise ratio than surface coils, therefore reducing the scan times. However, intra-cardiac coils suffer more severely from motion artifacts since both the anatomy and the coils are moving during image acquisition. We developed a tetrahedral-shaped active MR-tracking array and integrated it with a modified 3D-MDE sequence to perform prospective motion corrections, so that the entire image could be acquired in a “static” frame of reference. Experiments on ex-vivo swine hearts demonstrated significant image quality improvements during both in-plane and through-plane motion, with sufficient resolution to detect gaps in left-atrial ablation lesions.

Electronic Posters : Interventional Imaging
Click on to view the abstract pdf and click on to view the video presentation.
Interventional MRI: Instrument Visualization, Guidance & Interfaces

Monday May 9th
Exhibition Hall  14:00 - 16:00 Computer 65

14:00 3747.   Highly efficient 3D tracking and visualization of loopless active MRI devices using slice-direction-dephased, undersampled projection imaging 
Ashvin Kurian George1, J Andrew Derbyshire1, Michael S Hansen1, Christina E Saikus1, Ozgur Kocaturk1, Robert J Lederman1, and Anthony Z Faranesh1
1National Institutes of Health, Bethesda, Maryland, United States

We introduce a method to track the 3D curve of a moving active interventional device with a loopless-coil design. The goal is to collect small amounts of tracking data in between the data collection required for the reconstruction of multiple slices in the real-time display. The tracking data consists of two highly undersampled projection images of the device. We are able to achieve a greater data reduction than all previous methods by using slice-direction-dephased projection images of the device and optimal in-plane rotation.

14:30 3748.   Online Real-Time Visualization of an Active Catheter Using Compressed Sensing in Interventional MRI 
Cheng Ouyang1,2, Tobia Wech1,3, Kamal Vij4, and Li Pan1,5
1Center for Applied Medical Imaging, Siemens Corporate Research, Baltimore, MD, United States, 2Bioengineering, University of Illinois at Urbana-Champaign, Urbana, IL, United States, 3Institute of Radiology, University of Wuerzburg, Wuerzburg, Bavaria, Germany, 4SurgiVision, Inc., Irvine, CA, United States, 5Department of Radiology and Radiological Science, Johns Hopkins University, Baltimore, MD, United States

In interventional MRI, it is crucial to visualize catheter devices in real time. Compressed sensing (CS) has been recently proposed as a promising approach to accelerate MR imaging and data acquisition of sparse objects. However, current literature reports on this topic are limited to date to offline simulation studies, and true real-time visualization is hindered due to the bottleneck of time-consuming non-linear iterative CS image reconstruction. To our knowledge, no online implementation of CS on both image acquisition and reconstruction has yet been reported on a standard clinical MR scanner. In this work, we present a feasibility study on the use of CS for online real-time catheter visualization. The results from our study illustrate that a framework of online real-time CS acquisition and reconstruction can be successfully established, resulting in frame rates sufficient for real-time visualization of a moving catheter with typical velocity.

15:00 3749.   3D Passive Marker Tracking for MR-Guided Interventions 
Florian Maier1, Axel J. Krafft1, R. Jason Stafford2, Joshua P. Yung2,3, Rüdiger Dillmann4, Wolfhard Semmler1, and Michael Bock1
1Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany, 2Department of Imaging Physics, The University of Texas M. D. Anderson Cancer Center, Houston, Texas, United States, 3The University of Texas Graduate School of Biomedical Sciences, Houston, Texas, United States, 4Institute of Anthropomatics, Karlsruhe Institute of Technology, Karlsruhe, Germany

In percutaneous MR-guided interventions passive markers are used to delineate the position or the trajectory of rigid instruments, e.g. needles. In this work, a modified passive tracking pulse sequence for full 3D tracking is proposed. Based on the estimated 3D position of the marker, an imaging slice is automatically adjusted in real time. Measurements indicate that the pulse sequence allows accurate 3D tracking of rigid instruments. Thus, the choice of an optimal needle trajectory in percutaneous interventions is highly facilitated and under manual control of the operator.

15:30 3750.   MR Active Insertion Mandrel for Improved Delineation of Deep Brain Structures during MR Guided Electrode Insertion 
Alastair Martin1, Kamal Vij2, Paul Larson1, and Philip Starr1
1University of California - San Francisco, San Francisco, CA, United States, 2SurgiVision, Inc

Implantation of deep brain stimulator electrodes requires the insertion of a rigid mandrel prior to electrode placement. MR guided electrode implantations have been performed but have utilized a passive ceramic mandrel. Here we explore the potential SNR benefits that could be realized with an MR active mandrel. Three different mandrel RF coil designs, including dipole antenna, opposed solenoid, and flat loop, were constructed and imaged at 1.5T. The dipole antenna produced substantially inferior results to both the opposed solenoid and loop design, with the latter performing better overall and providing signal enhancement in a region up to four mandrel diameters.

Tuesday May 10th
  13:30 - 15:30 Computer 65

13:30 3751.   Device Monitoring and Dynamic Scanner Feedback Control for Active Device Safety in Interventional MRI 
Christina E Saikus1, Ozgur Kocaturk1, Merdim Sonmez1, Jamie A Bell1, Anthony Z Faranesh1, J Andrew Derbyshire1, Robert J Lederman1, and Michael S Hansen1
1National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, United States

We have developed and demonstrated a system to monitor active device performance and provide additional safeguards with dynamic scanner feedback control during MRI-guided interventions. A real-time sequence was modified to enable device signal monitoring, dynamic changes in flip angle and RF pulse width, and a low-power default mode. A custom LabVIEW interacted with the scanner to analyze the signal data and additional device temperature monitoring and then provide a system status and adjust scan parameters accordingly. This system can provide an additional safety mechanism for active device use and response when immediately stop scanning may be detrimental in a procedure.

14:00 3752.   Low-Cost MRI Compatible Interface Device for Interactive Scan Plane Control 
Mihai T Mazilu1, Anthony Zahi Faranesh1, John Andrew Derbyshire1, Robert J Lederman1, and Michael Schacht Hansen1
1National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, United States

A low-cost interface device for control of scan plane orientation is presented. Designed for use in interventional MRI, the device enables the physician to control the location and orientation of scan planes from within the MRI scanner room without the help of an outside scanner operator. It is built from off-the-shelf components and is completely configurable to suit an individual physician’s preferences or a specific application. The total material cost of the device is less than $300 and it is sufficiently generic to be used with most modern MRI systems.

14:30 3753.   Real-time Scan Plane Selection with a Novel Hand-held Device for Needle Guidance 
Matthew Joseph Riffe1, Stephen R Yutzy2, Colin Blumenthal3,4, Daniel P Hsu4, Dean A Nakamoto4, Jeffrey L Sunshine4, Chris A Flask1,4, Vikas Gulani4, Jeffrey L Duerk1,4, and Mark A Griswold4
1Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio, United States, 2Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania, United States,3Electrical and Computer Engineering, Ohio State University, Columbus, Ohio, United States, 4Radiology, University Hospitals of Cleveland, Cleveland, Ohio, United States

Here we propose a device that provides a physician with real time control of scan planes for interventional MRI applications. The device position and orientation is obtained by acquiring the position of three internal active tracking markers. Signal from the device is transmitted wirelessly, making it easy to manipulate inside the magnet bore. The device's spatial information is used to prescribe the scan plane for a real time sequence and is repeated before each repetition. Phantom studies show the tracking device system to be accurate, and the use of the system is presented with a human volunteer.

15:00 3754.   Diagnostic accuracy and workflow of 240 experimental MR biopsies with a clinical navigation solution outside the bore 
Harald Busse1, Tim Riedel1, Nikita Garnov1, Gregor Thörmer1, Thomas Kahn1, and Michael Moche1
1Diagnostic and Interventional Radiology Department, Leipzig University Hospital, Leipzig, Germany

Recently, an add-on solution for real-time navigation of percutaneous procedures outside the bore has been presented and clinically deployed. The purpose of this work was to thoroughly evaluate the diagnostic accuracy and workflow of 240 experimental biopsies by different operators. The mean success rate (93%) and median biopsy time (3:58 min, including MR table movements and control scan) observed for attending radiologists suggest that an "in-and-out" approach does not necessarily compromise diagnostic accuracy or clinical workflow. While the clinical performance can only be assessed on patients, this work provides valuable results for a large number of biopsies and different operators.

Wednesday May 11th
  13:30 - 15:30 Computer 65

13:30 3755.   A Novel Broad-band, High Power and RF-safe Cable for MR-guided Catheter Ablation 
Sascha Krueger1, Oliver Lips1, Bernd David1, and Steffen Weiss1
1Philips Research Laboratories, Hamburg, Hamburg, Germany

MR-guided electrophysiology (MR-EP) ablation procedures for treatment of arrhythmias have the potential benefit of visualizing the tissue response and improving catheter guidance. Effective measures to ensure RF safety of diagnostic MR-EP catheters have been proposed, including the use of active tracking via transformer-based cables and recording of intra-cardiac ECG via highly resistive (HR) wires. Providing trans-catheter ablation power transmission and tissue impedance measurement functionality RF-safely remains a major challenge. This work shows the initial evaluation of a broad-band, high-power transmission line for RF safe ablation and tissue impedance measurements based on a novel concept. The proposed ablation line is designed for integration with state-of-the-art tip-irrigated catheters and utilizes the irrigation liquid for cooling of a thin PCB-based cable consisting of many resonant trap circuits floating in the irrigation tube. It is shown that tip heating is eliminated and that the capacitors and inductors of trap circuits are effectively cooled by the irrigation liquid, so that local temperature elevations can be avoided completely over the entire length of the catheter.

14:00 3756.   Novel Approach to Real-time MR-Guided TIPS using an Actively Visualized Excimer Laser Catheter and Delivery System 
Christina E Saikus1, Jamie A Bell1, Kanishka Ratnayaka1,2, Venkatish K Raman1, Merdim Sonmez1, Anthony Z Faranesh1, Ozgur Kocaturk1, and Robert J Lederman1
1National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, United States, 2Children's National Medical Center, Washington DC, United States

In this work, we developed and tested the feasibility of a method to perform transjugular intrahepatic portosystemic shunt (TIPS) procedures under real-time MRI guidance using an actively visualized excimer laser catheter and delivery system. Passage from the hepatic to portal veins was achieved with the laser catheter traversing readily with direction and back support provided by the delivery system. An embedded loop coil in the laser provided clear tip positioning and visualization of curvature and alignment was seen from a loopless antenna comprised of the concentric tube delivery system design.

14:30 3757.   Tracking Rotational Orientation of Catheter Using Transmit Array System 
Haydar Celik1,2, Davut Ibrahim Mahcicek2, and Ergin Atalar1,2
1Electrical and Electronics Engineering, Bilkent University, Ankara, Turkey, 2National Research Center for Magnetic Resonance (UMRAM), Ankara, Turkey

A new method for the detection of rotational orientation of an inductively coupled RF (ICRF) coil using a transmit array system is proposed. In this method, a conventional body birdcage coil is used, but the quadrature hybrid is eliminated in order to use the two excitation channels separately. The transmit array system provided two identical RF pulses with different phase and amplitude at each TR in order to obtain linearly polarized excitations instead of a conventional rotational forward polarized excitation. ICRF coils are constructed on catheters for detecting rotational orientation and tracking purposes. The modifications on anatomy and the ICRF coil images are different due to this RF excitation scheme such that the ICRF coil can be separated from the anatomy image in real-time. After separating the ICRF coil from the anatomy, this novel method enables to calculate an absolute orientation of the ICRF coil constructed on a catheter in real-time. catheter-tracking, asymmetric catheter applications, such as MR guided endoluminal focused ultrasound, RF ablation, side looking optical imaging, and asymmetric needle puncturing, become feasible with this method.

15:00 3758.   Pure phase encoding acquisition for calibration of high geometric fidelity intervention applications 
Sjoerd Crijns1, Bas Raaymakers1, and Jan Lagendijk1
1Radiotherapy, UMC Utrecht, Utrecht, Netherlands

In MR-guided interventions in general and MR-guided radiotherapy in particular benefit from accurate definition of a connection between the treatment and imaging coordinate systems. This connection can be made using pure phase encoded imaging; the inherently long acquisition times of this method can be reduced by random under-sampling and subsequent iterative reconstruction. It is shown here that using this approach accelerated acquisition is possible of images with high geometric fidelity.

Thursday May 12th
  13:30 - 15:30 Computer 65

13:30 3759.   MR Guided Percutaneous Embolization of Low-Flow Vascular Malformations: Initial Experience Using a Hybrid MR/X-Ray Fluoroscopy System 
Clifford Raabe Weiss1, Aaaron J Flammang2, Wesley Gilson2, Dara L Kraitchman1, Sally E Mitchell1, Frank K Wacker3, and Jonathan S Lewin1
1Radiology and Radiologic Science, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States, 2Center for Applied Medical Imaging, Siemens Corporate Research, Baltimore, Maryland, United States, 3Department of Diagnostic and Interventional Radiology, Hannover Medical School, Hannover, Germany

Low-flow Vascular Malformations (VM’s) can present with a myriad of symptoms and signs, including pain, cosmetic disfigurement, functional impairment and bleeding. Current interventional radiologic techniques for treating low-flow VM’s consists of using Ultrasound and X-ray angiography to access and treat these lesions percutaneously. Due to poor ultrasound penetration and repeated exposure to ionizing radiation, these modalities have significant limitations, which can be solved using real time MR guidance for these procedures. In this abstract we present our initial experience (including workflow, therapeutic agents and outcomes) treating patients with low-flow VM’s using a hybrid, closed-bore 1.5T MRI/X-Ray “Miyabi” suite.

14:00 3760.   Construction of a MR Compatible Arthroscopic System and Its Clinical Application 
Christian Jürgen Seebauer1, Jens Rump2, Hermann Josef Bail3, Felix Güttler2, Bernd Hamm2, 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

Arthroscopy and MRI have already become an irreplaceable method in diagnosis and therapy of various joint disorders. Recently published researches have shown the possibility and advantage of MRI in imaging and navigation of drill placement in the treatment of Osteochondritis dissecans of the ankle joint and knee joint. Usually, these procedures are arthroscopic-assisted and drill placement is navigated by an image-intensifier. But because of MRI-incompatibility of available arthroscopic systems, the combined use of MRI and arthroscopy was incredible yet. The aim of this study was to develop and validate a MRI-compatible arthroscopic system. The combination of surface information provided by the endoscope and the in-depth information from MRI could be very useful in increasing the safety, reliability and availability of MRI-guided therapy.

14:30 3761.   Preliminary Accuracy Evaluation of 3T MRI-guided Transperineal Prostate Biopsy with Grid Template 
Junichi Tokuda1, Kemal Tuncali1, Iulian Iordachita2, Sang-Eun Song1, Andriy Fedorov1, Sota Oguro1, Andras Lasso3, Fiona M Fennessy1, Yi Tang1, Clare M Tempany1, and Nobuhiko Hata1
1Department of Radiology, Brigham and Women's Hospital, Boston, MA, United States, 2The Johns Hopkins University, Baltimore, MD, United States, 3School of Computing, Queen's University, Kingston, ON, Canada

This paper reports our initial feasibility study of MRI-guided core needle biopsy of the prostate in a 70cm bore 3-Tesla MRI scanner. Biopsy targets were defined on an intra-procedural T2 image as well as pre-operative MR images registered to the intra-procedural T2 image prior to the needle placement. The needle was guided by a specially-designed needle guidance grid template, which was registered to the image coordinate system by a z-shaped calibration frame. Our clinical study on 5 patients demonstrated that the procedure was feasible with needle placement accuracy of 4.9 mm.

15:00 3762.   Fast and reliable localization of brachytherapy seeds using undersampled co-RASOR 
Peter Roland Seevinck1, Hendrik de Leeuw1, Marinus A Moerland2, and Chris J.G. Bakker1
1Physics of MRI, Image Sciences Institute, University Medical Center Utrecht, Utrecht, Netherlands, 2Department of Radiation Oncology, University Medical Center Utrecht, Utrecht, Netherlands

Prostate brachytherapy by Iodine-125 seeds is a common treatment modality for localized prostate cancer. An important aspect in such a treatment is intra-operative and post-implant dose evaluation. The ideal imaging method should not involve X-ray radiation, should provide both excellent soft tissue contrast as well as a good localization of the implanted seeds, preferably in an acquisition time as short as possible, to prevent the influence of movement and to enable near real-time monitoring and dosimetry of interventional brachytherapy procedures. In this work, the use of highly undersampled center-out RAdial Sampling with Off-Resonance reception (co-RASOR) is investigated for these purposes.