Adam Christian Waspe^1,2, Meaghan O'Reilly¹, Jiawen Zhang¹, Yaseen Khan¹, Anthony Chau¹, Rajiv Chopra^1,2, and Kullervo Hynynen^1,2
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.

Jiming Zhang¹, Pei-Herng Hor¹, John Fischer², Ari Partanen³, Tiina Karjalainen³, and Raja Muthupillai^2
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

Hsu-Hsia Peng¹, Teng-Yi Huang², Wei-Min Tseng², Yu-Hui Ding³, Hsiao-Wen Chung⁴, Wen-Shiang Chen³, and Wen-Yih Isaac Tseng^5
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.

Lorena Petrusca¹, Magalie Viallon¹, Thomas Goget¹, Denis Morel², Xavier Montet¹, Vincent Auboiroux¹, Sylvain Terraz¹, Christoph D Becker¹, and Rares Salomir^1
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.

Lorena Petrusca¹, Magalie Viallon¹, Thomas Goget¹, Denis Morel², Vincent Auboiroux¹, Sylvain Terraz¹, Christoph Becker¹, and Rares Salomir^1
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.

Joshua de Bever^1,2, Allison Payne¹, Nick Todd¹, and Robert Roemer^3
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.

Benjamin Schwartz¹, and Nathan McDannold^2,3
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.

Joshua P Yung^1,2, Florian Maier³, David Fuentes¹, Axel J Krafft³, Andrew Elliott¹, Michael Bock³, John D Hazle^1,2, Wolfhard Semmler³, and R Jason Stafford^1,2
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.

Elena Kaye¹, and Kim Butts Pauly^2
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.

Benoit Larrat¹, Benjamin Marty¹, Mathieu Pernot², Mickael Tanter², Franck Lethimonnier¹, and Sébastien Mériaux^1
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.

Nathan McDannold¹, Costas D. Arvanitis¹, Natalia Vykhodtseva¹, and Margaret S. Livingstone^2
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.

Alessandro Napoli¹, Beatrice Cavallo Marincola¹, Michele Anzidei¹, guendalina Menichini¹, Gaia Cartocci¹, Carlo Catalano¹, and Roberto Passariello^1
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.

Valentina Giannini^1,2, Pejman Ghanouni³, Graham Sommer³, Chris Diederich⁴, Andrew Holbrook³, Vasant Salgaonkar⁴, Punit Prakash⁴, Harcharan Gill⁵, Donna Bouley⁶, and Kim Butts Pauly^3
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.

Roel Deckers¹, Sara M Sprinkhuizen¹, Marina Talelli², Bart Crielaard², Hans Ippel³, Rolf Boelens³, Twan Lammers^2,4, Chris J Bakker¹, Gert Storm², and Lambertus W Bartels^1
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.

Axel Joachim Krafft¹, Florian Maier¹, Jaane Rauschenberg¹, Joshua P Yung², Jürgen Walter Jenne^3,4, Wolfhard Semmler¹, and Michael Bock^1
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 90°-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.

David Fuentes¹, Joshua Yung¹, Andrew Elliott¹, John D Hazle¹, and Roger Jason Stafford^1
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.

Ashvin Kurian George¹, J Andrew Derbyshire¹, Michael S Hansen¹, Christina E Saikus¹, Ozgur Kocaturk¹, Robert J Lederman¹, and Anthony Z Faranesh^1
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.

Cheng Ouyang^1,2, Tobia Wech^1,3, Kamal Vij⁴, and Li Pan^1,5
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.

Florian Maier¹, Axel J. Krafft¹, R. Jason Stafford², Joshua P. Yung^2,3, Rüdiger Dillmann⁴, Wolfhard Semmler¹, and Michael Bock^1
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.

Alastair Martin¹, Kamal Vij², Paul Larson¹, and Philip Starr^1
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.

Christina E Saikus¹, Ozgur Kocaturk¹, Merdim Sonmez¹, Jamie A Bell¹, Anthony Z Faranesh¹, J Andrew Derbyshire¹, Robert J Lederman¹, and Michael S Hansen^1
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.

Mihai T Mazilu¹, Anthony Zahi Faranesh¹, John Andrew Derbyshire¹, Robert J Lederman¹, and Michael Schacht Hansen^1
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.

Matthew Joseph Riffe¹, Stephen R Yutzy², Colin Blumenthal^3,4, Daniel P Hsu⁴, Dean A Nakamoto⁴, Jeffrey L Sunshine⁴, Chris A Flask^1,4, Vikas Gulani⁴, Jeffrey L Duerk^1,4, and Mark A Griswold^4
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.

Harald Busse¹, Tim Riedel¹, Nikita Garnov¹, Gregor Thörmer¹, Thomas Kahn¹, and Michael Moche^1
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.

Sascha Krueger¹, Oliver Lips¹, Bernd David¹, and Steffen Weiss^1
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.

Christina E Saikus¹, Jamie A Bell¹, Kanishka Ratnayaka^1,2, Venkatish K Raman¹, Merdim Sonmez¹, Anthony Z Faranesh¹, Ozgur Kocaturk¹, and Robert J Lederman^1
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.

Haydar Celik^1,2, Davut Ibrahim Mahcicek², and Ergin Atalar^1,2
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.

Sjoerd Crijns¹, Bas Raaymakers¹, and Jan Lagendijk^1
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.

Clifford Raabe Weiss¹, Aaaron J Flammang², Wesley Gilson², Dara L Kraitchman¹, Sally E Mitchell¹, Frank K Wacker³, and Jonathan S Lewin^1
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.

Christian Jürgen Seebauer¹, Jens Rump², Hermann Josef Bail³, Felix Güttler², Bernd Hamm², and Ulf Teichgräber^2
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.

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 Hata^1
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.

Peter Roland Seevinck¹, Hendrik de Leeuw¹, Marinus A Moerland², and Chris J.G. Bakker^1
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.