ISMRM 21st Annual Meeting & Exhibition 20-26 April 2013 Salt Lake City, Utah, USA

1802 -1821 Thermotherapy & Thermometry
1822 -1832 MR-Guided Focused Ultrasound
1833 -1838 Intravascular MR-Guided Interventions
1839 -1843 MR-Guided Interventions From Head to Toe
1844 -1849 Software & Hardware for MR-Guided Interventions

Wednesday, 24 April 2013 (16:00-18:00) Exhibition Hall
Thermotherapy & Thermometry

MR Sub-Sampling Strategies for Transcranial MRgFUS Applications
Henrik Odéen1,2, Nick Todd2, Mahamadou Diakite1,2, Allison Payne2, and Dennis L. Parker2
1Physics and Astronomy, University of Utah, Salt Lake City, Utah, United States, 2Radiology, University of Utah, Salt Lake City, Utah, United States

Three different k-space subsampling schemes were implemented in a 3D segmented EPI sequence for temperature measurements using the PRF shift method. The three schemes were evaluated by HIFU heating through a skull imbedded in an agar gel phantom. It is shown that sampling schemes with sequential sampling in the phase encode direction perform well, whereas sampling schemes with centric sampling underestimate temperatures, due to temperature induced frequency shifts resulting in a blurring effect of the focal spot.

1803.   Towards Real-Time SAR Measurement with MR Thermometry
Changqing Ye1, An Jing2, Yan Zhuo1, Rong Xue1, and Jing Chen1
1State Key Laboratory of Brain and Cognitive Science, Beijing MRI Center for Brain Research, Institute of Biophysics, Chinese Academy of Sciences, Beijing, Beijing, China,2Siemens Mindit Magnetic Resonance Ltd., Shenzhen, Guangzhou, China

For ultra-high field imaging, many sequences are limited by the increased RF energy deposition, conventionally quantified by Specific Absorption Rate (SAR) which is an indirect estimation method, causing lack of subject¡¯s safety guarantee or unnecessary scan limitations. In this work, we present a PRF-based MR thermometry method to supervise temperature increased by the RF energy deposition directly with real-time temperature measurement with a very high precision (<0.1¡æ) within a very short time (2 s). This method might be used to monitor temperature change in subjects directly, which would be especially useful for ultra-high field imaging.

1804.   Accelerated Real-Time MR Thermometry Using a New Compressed Sensing Framework of Nonlinear Filter and K-T FOCUSS
Feiyu Chen1, Xiaoying Cai1, Xinwei Shi1, Shuo Chen2, Enhao Gong3, Kui Ying2, and Shi Wang2
1Department of Biomedical Engineering, Tsinghua University, Beijing, China, 2Department of Engineering Physics, Tsinghua University, Beijing, China, 3Electrical Engineering, Stanford University, Stanford, CA, United States

Phase information is significant in temperature mapping using proton resonance frequency shift (PRFS) method. Acceleration methods can be applied to reconstruction in order to shorten the imaging duration and accomplish real-time temperature mapping. A method to improve the accuracy of phase reconstruction in dynamic scans is proposed in our research. Compressed Sensing with nonlinear filters such as median filter and k-t FOCUSS are combined in our method. Phantom experiments have demonstrated that the proposed method is a promising tool for real-time temperature monitoring using PRFS method.

1805.   Direct Reconstruction of Proton Resonance Frequency-Shift Temperature Maps from K-Space Data for Highly Accelerated Thermometry
Pooja Gaur1 and William A. Grissom2
1Chemical and Physical Biology, Vanderbilt University, Nashville, Tennessee, United States, 2Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, United States

Real-time volumetric MR thermometry is desirable for several applications of MR-guided focused ultrasound. We propose a constrained temperature reconstruction method that estimates temperature changes directly from k-space data. Because we fit an image model comprising fully-sampled baseline images to the accelerated k-space data, temperature maps containing aliasing artefacts are removed from the solution space, and high acceleration factors can be achieved without temporal regularization that sacrifices temporal resolution. The method is demonstrated in 2D simulations and experiments. The method will readily extend to 3D, where it will enable accurate real-time volumetric thermometry at a high frame rate.

1806.   Accelerated Phase Reconstruction Using Sharable Information from Reference Scan and Its Application for Real-Time MR Thermometry
Feiyu Chen1, Enhao Gong2, Shuo Chen3, Xinwei Shi1, Feng Huang4, Shi Wang3, and Kui Ying3
1Department of Biomedical Engineering, Tsinghua University, Beijing, China, 2Electrical Engineering, Stanford University, Stanford, CA, United States, 3Department of Engineering Physics, Tsinghua University, Beijing, China, 4Philips Healthcare, Gainesville, FL, United States

MR thermometry based on proton resonance frequency shift (PRFS) is a promising method for noninvasive temperature measurement. In this method, phase differential information is highly needed during the acquisition and reconstruction process. Previous research has demonstrated that the correlation between different scans could be used for reconstruction from under-sampled data. Based on this demonstration, a method for accelerated temperature mapping using sharable information from reference scans is proposed in our research. Phantom experiments have demonstrated the accuracy and feasibility of our new framework in comparison with previous parallel imaging methods and parallel¨CCS methods.

1807.   Extended Kalman Filtering for Continuous Volumetric MR-Temperature Imaging
Baudouin Denis de Senneville1,2, Chrit T.W. Moonen2, and Mario Ries2
1IMB, UMR 5251 CNRS/University Bordeaux 1/INRIA, Talence, Gironde, France, 2Imaging Division, UMC Utrecht, Utrecht, Netherlands

For the continuous monitoring of High Intensity Focused Ultrasound interventions using real-time Magnetic Resonance thermometry, a volumetric observation of the temperature in the near- and far-field would be preferable. Here, a continuous volumetric MR-temperature monitoring is obtained as follows: 1) The targeted area is continuously scanned by a multi-slice sequence; 2) Measured data and a priori knowledge of 3D data derived from a forecast based on a physical model are combined using a Kalman filter. A quantitative analysis of the accuracy of the method is presented when applied to different temperature increases and when applied with different spatial resolutions.

1808.   Real-Time Volumetric MR Thermometry Aided by Motion Tracking Using Tip Tracking Coils
Peng Wang1 and Orhan Unal1
1Medical Physics, University of Wisconsin - Madison, Madison, Wisconsin, United States

MRI-guided RF ablation is a promising method for the treatment of atrial fibrillation. Proton resonance frequency (PRF) shift MR thermometry, which has been the method of choice, is sensitive to motion. In this work, a new method utilizing information from catheter-embedded tip tracking coils and Linear Phase Model (LPM) is proposed to synthesize reference phase images for motion correction. This method utilizes 2D multi-slice acquisition to facilitate volumetric temperature monitoring of the target region. The proposed method offers advantages in the case of irregular through-plane motion and reduced computation.

1809.   Co-Registration of MRI Via a Learning Based Fiducial-Driven Registration (LeFiR) Scheme: Evaluating Laser Irradiation Changes for Glioblastomas and Epilepsy
Tao Wan1, B.Nicolas Bloch2, Shabbar Danish3, and Anant Madabhushi1
1Case Western Reserve University, Cleveland, OH, United States, 2Boston University School of Medicine, Boston, MA, United States, 3University of Medicine and Dentistry, New Jersey, New Brunswick, NJ, United States

The purpose of this work is to co-register pre- and post-ablation MRI images for laser-induced interstitial thermal therapy (LITT) of neurological disorders, in order to build an improved model for therapy planning and evaluating imaging related treatment changes in terms of MRI markers for LITT. Despite being a promising treatment option for multiple brain diseases, the effect of LITT on the focal site is currently unknown. The objective of this work is to develop a learning based fiducial driven registration method (LeFiR) for accurately registering pre- and post-LITT brain images. The localized nature of deformation induced by LITT can be well captured and precisely aligned to pre-LITT image via a supervised learning scheme. The identified optimal landmark set is utilized to drive a thin-plate spline (TPS) image registration. The LeFiR method was performed to register pre- and post-LITT brain MR images for treating glioblastoma multiforme (GBM) and epilepsy with LITT. By using LeFiR, more accurate and robust registration results can be achieved according to two registration experiments performed on brain MRI for GBM and epilepsy. The local deformation induced by the LITT procedure can be better captured and recovered by the identified landmark fiducials than simply uniformly picking landmarks. Given that only spatial information is used to determine landmark locations, the LeFiR method has the potential to be adopted in various clinical applications for the purpose of registering different image modalities.

1810.   MR-Guided Thermotherapy of Abdominal Organs Using a Robust PCA-Based Motion Descriptor
Baudouin Denis de Senneville1,2, Mario Ries2, and Chrit T.W. Moonen2
1IMB, UMR 5251 CNRS/University Bordeaux 1/INRIA, Talence, Gironde, France, 2Imaging Division, UMC Utrecht, Utrecht, Netherlands

Thermotherapies can now be guided in real-time using magnetic resonance imaging. This technique is gaining importance in interventional therapies for abdominal organs. An accurate on-line estimation and characterization of organ displacement is mandatory to prevent misregistration and correct for motion related thermometry artifacts. Here we describe the use of a Principal Component Analysis to detect spatio-temporal coherences in the physiological organ motion and to characterize in real-time the complex organ deformation. During hyperthermia, incoherent motion patterns could be discarded, which enabled improvements in the compensation of motion related errors in thermal maps, as well as in the motion estimation robustness.

in vivo Evaluation of Hybrid PRF/T1 Approach for Temperature Monitoring During Breast MRgHIFU Treatments
Nick Todd1, Mahamadou Diakite2, Allison Payne2, and Dennis L. Parker1
1Radiology, University of Utah, Salt Lake City, Utah, United States, 2Physics, University of Utah, Salt Lake City, Utah, United States

The goal is to simultaneously measure temperature changes in aqueous and adipose tissues to properly monitor MR-guided HIFU treatments of localized breast cancer. To achieve this, we have developed a 2D multi-echo hybrid PRF/T1 sequence which measures PRF changes in water-based tissues and T1 values in fat-based tissues. The precision of the technique was evaluated by imaging four female volunteers in our developed breast-specific MRgHIFU system.

1812.   A Hybrid PRF/T1/T2* Sequence for Assessing Tissue Damage
Nick Todd1, Mahamadou Diakite2, Allison Payne2, and Dennis L. Parker1
1Radiology, University of Utah, Salt Lake City, Utah, United States, 2Physics, University of Utah, Salt Lake City, Utah, United States

We present a sequence for simultaneous measurement of PRF, T1, and T2*. The additional information provided by T1 and T2* may be helpful for assessing tissue damage during MR-guided thermal therapies. These properties are analyzed as a function of thermal dose during ex vivo HIFU heating of turkey muscle.

1813.   Spectrum-Based and Least-Square PRF Hybrid Method for MR Temperature Mapping
Shuo Chen1, Xinwei Shi2, Feiyu Chen2, Karen Ying3, and Shi Wang3
1Engineering Physics, Tsinghua University, Beijing, China, 2Biomedical Engineering, Tsinghua, Beijing, China, 3Engineering Physics, Tsinghua, Beijing, China

A new Spectrum Based/Least-Square PRFS hybrid method for MR temperature mapping is proposed, which can measure temperature in water-only and water-fat mixed tissues simultaneously. In water-only region, the accuracy of temperature measurement is improved by modifying traditional PRFS method with least square fitting. In addition, fat frequency calculated in water-fat mixed voxels is utilized to eliminate B0 field drift effect in PRFS method. The proposed method was validated in phantom experiment.

1814.   Absolute MR Thermometry for Near-Field Monitoring During MR-HIFU Heating
Mie Kee Lam1, Martijn de Greef1, and Lambertus W. Bartels2
1Image Sciences Institute, University Medical Center Utrecht, Utrecht, Netherlands, 2University Medical Center Utrecht, Utrecht, Netherlands

In the application of MR-guided High Intensity Focused Ultrasound (MR-HIFU) to organs in the abdomen, the near-field area is at risk of undesired heat accumulation. Therefore, there is a need for a temperature mapping technique that can visualize the cumulative near field heating effects of subsequent sonications. In this work we show the potential of using multi-gradient echo (mGE)-based absolute MR thermometry at the subcutaneous fat-muscle interface for the assessment of the thermal build-up in the near-field area.

1815.   Using a Simple Thermal Model to Correct Errors in PRFS MR Thermometry Due to Heat-Induced Tissue Susceptibility Changes
Paul Baron1, Roel Deckers1, Martijn de Greef1, Job G. Bouwman1, Chris J.G. Bakker1, and Lambertus W. Bartels1
1University Medical Center Utrecht, Utrecht, Utrecht, Netherlands

During MR-guided high intensity focused ultrasound (MR-HIFU) ablation of fat-containing tissues like the human breast or liver, heat induced susceptibility changes may give rise to local field disturbances, leading to errors in PRFS thermometry of the water-based tissues. A correction method is presented that combines the initial uncorrected measured temperature change with a thermal model to estimate the field disturbance and thus correct for these errors. The feasibility is shown in a porcine adipose tissue and ethylene glycol gel phantom. The maximum temperature error decreased from 3°C before correction to less than 1°C after the correction.

1816.   A New Model for Visualization of Contrast Agent Release from Thermosensitive Liposomes Induced by Laser Based Hyperthermia
Linus Willerding1, Simone Limmer1, Martin Hossann1,2, Anja Zengerle1, Maximilian F. Reiser3, Rolf D. Issels1,2, Lars H. Lindner1,2, and Michael Peller3
1Department of Internal Medicine III, University Hospital of Munich, Ludwig-Maximilians University, Munich, Germany, 2CCG Tumor Therapy through Hyperthermia, Helmholtz Zentrum München, German Research Center for Environmental Health, Munich, Germany, 3Department of Clinical Radiology, University Hospital of Munich, Ludwig-Maximilians University, Munich, Germany

Efficacy of systemically applied anti-cancer drugs is limited by insufficient selectivity and thus dose is limited by side effects. To improve the effectiveness of chemotherapy, thermosensitive liposomes (TSL) in combination with hyperthermia are used to target and trigger the release of chemotherapeutics. With MRI contrast agent loaded TSL (CA-TSL) were used for visualisation. Here we present a newly developed setup for MR-monitoring of laser-based hyperthermia in a rat model with CA-TSL for optimized visualisation of content release.

1817.   Reference-Based Realtime Temperature and Damage Estimate Maps for Monitoring Laser Ablation of Hepatic Tumors Under MRI
Anil Shetty1, Hiroumi Kitajima2,3, Tracy E. Powell2,3, Michael A. Bowen2,3, and Sherif G. Nour2,3
1Visualase Inc, Houston, Texas, United States, 2Department of Radiology and Imaging Sciences, Emory University Hospital, Atlanta, Georgia, United States, 3Interventional MRI Program, Emory University Hospital, Atlanta, Georgia, United States

This report demonstrated the feasibility of percutaneous laser ablation for hepatic tumors with real-time MRI monitoring within a dedicated “interventional MRI” suite. The online feedback of the ablation, along with combination of multiple fibers and pullbacks, allowed creation of large ablation volumes. The real-time monitoring, along with automatic shutoff mechanism with triggering of safety limits, protected adjacent critical structures. Advantages of using MR guided laser ablation include ability to ablate lesions which are in locations that are difficult to access and ability to ablate lesions which are only conspicuous on certain MR weighted sequences.

1818.   MR-Guided Temperature Mapping in Prostate Cancer Patients: Stability and Feasibility
Joyce GR Bomers1, Eva Rothgang2,3, Christiaan G. Overduin1, Jörg Roland3, Jelle O. Barentsz1, and Jurgen J. Füttterer1,4
1Radiology, Radboud University Nijmegen Medical Centre, Nijmegen, Gelderland, Netherlands, 2Center for Applied Medical Imaging, Siemens Corporation, Corporate Research, Baltimore, Maryland, United States, 3Siemens Healthcare, MR, Erlangen, Bayern, Germany, 4MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente, Enschede, Overijssel, Netherlands

The clinical feasibility and time efficiency of an integrated workflow for MR-guided transrectal laser treatment and real-time treatment monitoring were tested. Furthermore, temperature stability at 3T in prostate cancer patients using a fast gradient echo (GRE) echo planar imaging (EPI) sequence was evaluated.

1819.   Impact of 3D Temperature Probe Localization Variability on MR Thermometry Validation for RF Hyperthermia
Matthew Tarasek1, Lorne Hofstetter1, Ruben Pellicer2, Jurriaan Bakker2, Wouter Numan2, Gyula Kotek2, Eric Fiveland3, Gavin Houston4, Gerard van Rhoon2, Maarten Paulides2, and Desmond Yeo1
1MRI, GE Global Research, Niskayuna, NY, United States, 2Erasmus Medical Center, Rotterdam, Netherlands, 3MRI, GE Global Research Center, Niskayuna, NY, United States,4GE Healthcare, Rotterdam, Netherlands

Validation of MR thermometry (MRT) for RF hyperthermia in a head and neck clinical setup requires accurate co-registration of the inserted temperature probes to MRT data. Here, we explore the use of MR imaging techniques and 3D spline fitting for probe localization. In addition, we investigate how uncertainty in the localization affects the registration of probe and MRT readings. Findings show that a maximum operator-dependent temperature probe placement variability of 2mm along the catheter length accounts for at most a ±0.5 degree temperature uncertainty in the MRT maps.

1820.   Human Brain Cooling During Breath-Holding
Sébastien Murat1, Jan Weis1, Francisco Ortiz-Nieto1, and Håkan Ahlström1
1Department of Radiology, Uppsala University Hospital, Uppsala, Sweden

Controversy exists as to whether humans are capable of brain-cooling under any circumstances. Based on previous animal experiments, evidence of brain cooling was sought during controlled breath-holding. MR phase-difference method was used for measurement of human brain temperature changes during breath-hold. Brain temperature promptly decreased by ca 1 °C in 1 min. Indications are that humans can invoke extreme brain cooling to lower metabolic rate. The study opens-up new in-roads for potentially treating a wide range of critical illnesses (e.g., stroke, cardiac arrest, brain injury) avoiding the limitations of therapeutic hypothermia.

1821.   Automatic 3D Probe Localization and Iceball Segmentation for MRI-Guided Kidney Cryoablation
Xinyang Liu1, Kemal Tuncali1, William M. Wells, III1, and Gary P. Zientara1
1Radiology, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, United States

MRI-guided cryoablation provides direct visualization of the target tumor and iceball. Visual assessment of therapy progress during the freezing cycle can be challenging, though. Nonetheless, real-time quantitative assessment of ablation is needed to ensure safety and effectiveness. We developed software that includes methods for: (1) automatic cryoprobe localization, able to detect multiple inserted probes (in 3D) from pre-freeze MRI; and, (2) automatic iceball segmentation, guided by the labeled probes, that can extract 3D iceball configuration from periodic MRI scanning during the freezing cycle. Both methods showed good accuracy when applied to five cases of 3T MRI-guided cryoablation of kidney tumors.


Wednesday, 24 April 2013 (16:00-18:00) Exhibition Hall
MR-Guided Focused Ultrasound

1822.   Effect of Additional Anatomical Features of the Head from High Resolution 3D UTE Images on Focal Intensity and Location for Transcranial MR-Guided Focused Ultrasound Surgery
Urvi Vyas1, Ethan M. Johnson2, Michael Marx2, John M. Pauly2, and Kim R. Butts Pauly1
1Radiology, Stanford University, Stanford, California, United States, 2Electrical Engineering, Stanford University, Stanford, California, United States

For transcranial MR-guided focused ultrasound surgery in the brain, CT based imaging is used currently for correcting for distortions in the location and shape of the beam’s focus due to heterogeneities of the cranium. In this work we use high resolution UTE images and 3D ultrasound beam simulations to demonstrate the effect of additional anatomical features of the head (skin, subcutaneous fat, galea aponeurotica, marrow) on the location and intensity of the focal zone. A 2 mm on-axis shift and a 20% decrease in the focal intensity is estimated using information from the UTE images.

1823.   A Method to Improve Transcostal MR-HIFU Sonication in Presence of Electronic Beam Steering
Delphine Elbes1,2, Sébastien Roujol2,3, Mathilde Merle1,2, and Bruno Quesson1,2
1IHU LIRYC/ CRCTB, INSERM U1045, University Bordeaux Segalen, Pessac, France, 2Laboratoire d’imagerie fonctionnelle et moléculaire, UMR 5231 CNRS/ University Bordeaux Segalen, Bordeaux, France, France, 3Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, United States

This study presents a new strategy to perform HIFU through the rib cage using beam steering under real time MR thermometry, to track the respiratory movement or to performed multipoint ablation while avoiding heating of ribs. This method, used to minimize the energy deposition around the bones, was based on electronic deactivation of transducer elements located in front of the rib so called “binarized apodization law”. This work sought to demonstrate the necessity of an update of the binarized apodization law when using HIFU beam steering in order to increase the safety of the treatment and improve the focusing.

1824.   Comparison of Two Techniques for Estimation of Thermal Diffusivity with MRgHIFU
Christopher Reed Dillon1, Allison Payne2, and Robert Roemer3
1Bioengineering, University of Utah, Salt Lake City, UT, United States, 2Utah Center for Advanced Imaging Research, University of Utah, Salt Lake City, UT, United States,3Mechanical Engineering, University of Utah, Salt Lake City, UT, United States

Each method has potential to improve patient treatment planning of MRgHIFU treatments.

1825.   Real-Time Monitoring of Inertial Cavitation Effect on Diluted Microbubbles by MRI
Shih-Chieh Lin1, Chun-Wei Chen1, Chen-Hua Wu1, Chung-Hsin Wang1, Shih-Tsung Kang1, Chih-Kuang Yeh1, Wen-Shiang Chen2,3, and Hsu-Hsia Peng1
1Department of Biomedical Engineering and Environmental Sciences, National Tsing Hua University, Hsinchu, Taiwan, Taiwan, 2Department of Physical Medicine and Rehabilitation, National Taiwan University Hospital, Taipei, Taiwan, Taiwan, 3Division of Medical Engineering Research, National Health Research Institutes, Miaoli, Taiwan, Taiwan

Transmitting focus ultrasound (FUS) with usage of microbubbles (MBs) has been used to increase blood-brain barrier permeability. In this study, the HASTE sequence was performed to real-time monitor the inertial cavitation effect of MBs. At the onset of inertial cavitation, strong turbulence was produced in solutions. Therefore, with performing HASTE sequence, it was difficult to refocus signals and thus signal drops were revealed. Under the conditions of diluted MBs and acquisitions with different slice thicknesses, substantial signal drops were still observable at the very beginning of FUS transmission, suggesting the feasibility of applying this scheme for in vivo experiments.

1826.   Automatic Tumor Delineation by Multiparametric MR Analysis Based on Endogenous Contrast
Stefanie J.C.G. Hectors1, Igor Jacobs1, Gustav J. Strijkers1, and Klaas Nicolay1
1Biomedical NMR, Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, Netherlands

HIFU tumor treatment planning is generally performed with contrast-enhanced T1-weighted imaging. In view of possible toxicity issues of the Gd-chelate during HIFU, often a wait time is applied before start of the treatment. It was assessed whether accurate tumor delineation is also possible by multiparametric MR analysis solely based on endogenous contrast. k-means clustering was applied to T1, T2 and ADC maps of tumor-bearing mice with all feature vectors and variable numbers of clusters k. Maximum sensitivity (0.87) and specificity (0.90) were found for feature vector {T2,ADC} with k=6, indicating feasibility of tumor delineation based on endogenous MR parameters.

1827.   Cytoreductive Surgical Treatment of Pleural Mesothelioma: A Comparison Study Betweem Radiofrequency Ablation and MRgFUS Treatments in a Swine Model of Mesothelioma
Marcia Costa1, Carolina Fernandes1, Arik Hananel2, Matt Eames2, John Angle3, John P. Mugler, III3, Talissa A. Altes3, and Jaime F. Mata3
1Institute of Biophysics and Biomedical Engineering, FCUL, Lisbon, Portugal, 2Focused Ultrasound Surgery Foundation, Charlottesville, Virginia, United States, 3Radiology and Medical Imaging, University of Virginia, Charlottesville, Virginia, United States

The main aim of this study was to determine and to compare the feasibility of pleural mesothelioma debulking with Magnetic Resonance guided Focused Ultrasound Surgery (MRgFUS) and Radiofrequency Ablation (RFA), in a swine model of mesothelioma. We were able to create a successful mesothelioma tumor model in pigs and study its characteristics in-vivo using Magnetic Resonance Imaging (MRI) and post-mortem during necropsy. Furthermore, it was possible to prove the feasibility of both techniques, as well as to investigate the best parameters to apply them in large animal. Therefore, it was as innovative study in mesothelioma tumor model development and treatment.

Treatment of Staphylococcus Aureus Induced Abscesses Via Magnetic Resonance Guided Focused Ultrasound
David Bates1,2, Birgit Rieck1, Laura Curiel1,3, and Samuel Pichardo1,3
1Thunder Bay Regional Research Institute, Thunder Bay, Ontario, Canada, 2Biology, Lakehead University, Thunder Bay, Ontario, Canada, 3Department of Electrical and Computer Engineering, Lakehead University, Thunder Bay, Ontario, Canada

MR-guided focused ultrasound was investigated as a mode of treatment for subcutaneous murine Staphylococcus aureus abscesses. High and moderate temperature ultrasonication of the abscess centre were investigated, with high temperature (65˚C) demonstrating a significantly reduced (p<.05) bacterial concentration with respect to control four days post-treatment. Neither level of treatment was shown to increase inflammation over the baseline elevated abscess activity, suggesting innate immune system sparing.

1829.   Initial Experience with Volumetric MRI-Guided High-Intensity Focused Ultrasound Ablation in Breast Cancer Patients
Laura Merckel1, Roel Deckers2, Thijs van Dalen3, Max Köhler4, Gerald Schubert4, Joost van Gorp5, Paul Vaessen6, Willem Mali1, Chrit T.W. Moonen2, Lambertus W. Bartels2, and Maurice A.A.J. van den Bosch1
1Radiology, Univeristy Medical Center Utrecht, Utrecht, Netherlands, 2Images Sciences Institute, Univeristy Medical Center Utrecht, Utrecht, Netherlands, 3Surgery, Diakonessenhuis, Utrecht, Netherlands, 4Philips Heathcare, Vantaa, Finland, 5Pathology, Diakonessenhuis, Utrecht, Netherlands, 6Anesthesia, University Medical Center Utrecht, Utrecht, Netherlands

Our initial experiences with a dedicated MR-HIFU breast platform using a lateral and volumetric ablation technique are presented. In total, 10 breast cancer patients will be included. The study is performed according to a treat-and-resect protocol. In the first patient, it was difficult to perform a sonication due to problems with patient positioning and movement. In the second patient, three sonications were performed, causing tissue necrosis in the tumor observed during histopathological analysis. The PRFS-based optimized MR thermometry sequence had a temporal standard deviation of 1.86°C after applying the multibaseline method to correct for temperature errors induced by respiration.

1830.   Feasibility of MR Thermometry in Pancreas
Roel Deckers1, Baudouin Denis de Senneville1,2, Mario Ries1, Hanne D. Heerkens3, Cornelis A.T. van den Berg3, Marco van Vulpen3, and Chrit T.W. Moonen1
1Image Sciences Institute, University Medical Center Utrecht, Utrecht, Utrecht, Netherlands, 2CNRS/Université Bordeaux 1/INRIA, Institut de Mathématiques de Bordeaux UMR 5251, Talence, Gironde, France, 3Radiotherapy, University Medical Center Utrecht, Utrecht, Utrecht, Netherlands

MRI guided High Intensity Focused Ultrasound (HIFU) might become a new tool for the non-invasive image-guided treatment of pancreatic cancer. For ablation as well as hyperthermia treatments accurate MR temperature measurements are essential. In this study the accuracy of PRFS based thermometry in the pancreas was investigated in volunteers. Temperature standard deviation of 2-3 degrees was obtained in the pancreas during breath hold and during free breathing (after correction for motion related errors using a multi-baseline approach). We conclude that temperature mapping for guiding a HIFU ablation procedure is feasible in the pancreas.

1831.   MR-Based Targeting of Histotripsy Therapy at 7T
Steven P. Allen1, Timothy L. Hall1, Charles A. Cain1, and Luis Hernandez-Garcia1
1Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, United States

Here we investigate the feasibility of using HIFU induced cavitational bubble clouds as a targeting and steering mechanism for MR-guided cavitation-based ultrasound therapy. GRE imaging sequences are sensitive to the presence of the transient bubble cloud. Further, the transient cloud's associated B0 field perturbation behaves much like that of a stationary bubble.

1832.   Feasibility of MR Guided HIFU on a 7T Animal MR Scanner, to Evaluate Pathologic Effects of High Intensity Focused Ultrasound in Mice
Martijn Hoogenboom1, Martijn den Brok2, Erik Dumont3, Gosse Adema2, Arend Heerschap1, and Jurgen J. Futterer1,4
1Department of Radiology, Radboud University Nijmegen Medical Centre, Nijmegen, Gelderland, Netherlands, 2Department of Tumor Immunology, Radboud University Nijmegen Medical Centre, Nijmegen, Gelderland, Netherlands, 3Image Guided Therapy, Pessac, France, 4MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente, Enschede, Overijssel, Netherlands

High intensity focused ultrasound (HIFU) is the only known non-invasive ablation technique available to deliver high energies in a millimeter-sized focus spot. The local effects of HIFU in tissue can be separated into thermal and mechanical effects and depends on different HIFU strategies. These different effects results in various ways of tumor destruction and can be created by different HIFU settings. Therefore, this study has been set up to examine the feasibility of MR guided HIFU in a 7T animal MR system, to investigate different settings and to evaluate the corresponding tumor outcomes.


Wednesday, 24 April 2013 (16:00-18:00) Exhibition Hall
Intravascular MR-Guided Interventions

1833.   3T Intravascular MRI, IVUS and OCT: A Study in Contrast
Shashank Sathyanarayana Hegde1, Clifford R. Weiss2, M. Arcan Erturk3, and Paul A. Bottomley1,3
1Radiology, Johns Hopkins University, Baltimore, Maryland, United States, 2Radiology, Johns Hopkins University, Baltimore, MD, United States, 3Electrical and Computer Engineering, Johns Hopkins University, Baltimore, Maryland, United States

Atherosclerosis is a leading cause of morbidity and mortality. Typically, it is diagnosed by X-ray catheterization, which reveals luminal narrowing but is unsuitable for assessing plaque vulnerability to rupture or vessel wall thickening. Intravascular (IV) Ultrasound, IV optical coherence tomography and 3T IV MRI are non-ionizing alternatives to angiography. We compare, head-to-head, the performance (the signal- and contrast-to-noise ratios, spatial resolution, effective field-of-view, speed, and artifacts) of these modalities in diseased human vessel specimens and in a stented vessel in vitro. We show that 3T IV MRI can offer imaging capability with potentially significant advantages vs. existing methods.

1834.   Passive Magnetic Resonance Catheter Tracking with Spatial Wavelet and Temporal Constraints
M. Ethan MacDonald1,2, R. Marc Lebel2,3, and Richard Frayne1,2
1Biomedical Engineering, University of Calgary, Calgary, AB, Canada, 2Radiology and Clinical Neurosciences, University of Calgary, Seaman Family MR Research Centre, Foothills Medical Centre, Calgary, AB, Canada, 3Applied Science Laboratory, GE Healthcare, Calgary, AB, Canada

In this work we demonstrate L1 constrained reconstruction of a variable density under sampled series, a similar method has been demonstrated for dynamic susceptibility contrast bolus chase imaging. Using the positive contrast of gadolinium in an endovascular catheter we show 3D catheter tracking with high temporal (4.7 Hz) and spatial resolution (64x64x16 acquisition matrix). An acceleration rate of 12.2x is achieved with the constrained reconstruction while maintaining good catheter conspicuity. Maximum intensity projections and 3D iso surfaces are used for rendering catheter images.

1835.   Simultaneous Stereoscopic 3D-Visualization of Vascular Structures and a Passive Catheter in Real Time
Alexander Brunner1, Florian Maier2, Wolfhard Semmler1, and Michael Bock3
1Dpt. of Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany, 2Dpt. of Imaging Physics, The University of Texas M. D. Anderson Cancer Center, Houston, TX, United States, 3Dpt. of Radiology - Medical Physics, University Hospital Freiburg, Freiburg, Germany

Conventional 2D-X-ray fluoroscopy or DSA only provide projection images of the vessels during intravascular catheter interventions, and expose both patient and inter-ventionalist to ionizing radiation. To enable MR-guided intravascular procedures, in this work an acquisition and display concept for stereoscopic images is presented that acquires fast projections images at different stereo angles. These images are displayed on a modified 3D monitor to visualize vascular structures and a passive catheter in 3D in real-time.

1836.   Self-Resonant Swiss Roll Structures as Semi-Active Device Visualization Method for Interventional MRI
Mandy Kaiser1, Markus Detert2, Urte Kägebein1, Hans-Peter Schulze3, Bertram Schmidt2, and Georg Rose1
1Department of Healthcare Telematics and Medical Engineering, Otto-von-Guericke University, Magdeburg, Sachsen-Anhalt, Germany, 2Department of Microsystems Technology, Otto-von-Guericke University, Magdeburg, Sachsen-Anhalt, Germany, 3Department of Theoretical Electrical Engineering, Otto-von-Guericke University, Magdeburg, Sachsen-Anhalt, Germany

During MR-guided minimal-invasive interventions the precise positioning of the instruments has a high impact on the treatment outcome. In order to get a visual verification of the instruments position, several highlighting methods such as resonant markers have been developed. This paper investigates the usability of self-resonant swiss roll structures as semi-active visualization method. Several resonant markers were fabricated and analyzed regarding electrical parameters and visibility within the MR image. The achieved quality factors range from 40 to 91. Severely high contrast-to-noise ratios were measured with all markers. Further investigations should concentrate on a miniaturization of the fabricated markers.

1837.   Magnetic Resonance Elastography for Measuring the Compliance of Occlusive Vascular Disease
Brian S. Kates1, Kevan J. T. Anderson1, and Graham A. Wright1
1Imaging Research, Sunnybrook Research Institute, Toronto, Ontario, Canada

Percutaneous arterial revascularization of chronic total occlusions (CTOs) is hindered by the presence of a hard proximal fibrous cap and lack of image guidance. A technique is presented for measuring the stiffness of occlusive lesions that may facilitate revascularization by helping the process of guidewire selection and placement. In this study, static magnetic resonance elastography is explored as a method of determining the stiffness of CTOs. The technique is demonstrated in a CTO phantom made of agar and gelatin, and displacement images are obtained using a stimulated echo MR imaging pulse sequence and a pneumatic compression system.

1838.   LARFET (Low Amplitude RF at Echo Time) for Catheter Tracking
Murat Tümer1, Baykal Sarioglu2, Senol Mutlu2, Arda Yalcinkaya2, and Cengizhan Ozturk1
1Institute of Biomedical Enginering, Bogaziçi University, Istanbul, Turkey, 2Electrical and Electronics Enginering, Bogaziçi University, Istanbul, Turkey

In this work we propose utilization of a very low amplitude, rectangular and off-center RF pulse applied during echo detection, LARFET (Low Amplitude RF at Echo Time), that can be used as the reference for frequency downconversion at the catheter tip. With frequency downconversion the signal losses during transmission are lowered and the frequency analysis to extract the location information is simplified.


Wednesday, 24 April 2013 (16:00-18:00) Exhibition Hall
MR-Guided Interventions From Head to Toe

1839.   Fast Preoperative Planning Method for MR-Guided Laser Ablation in Brain
Erol Yeniaras1, David T. A. Fuentes2, Samuel J. Fahrenholtz1, Jeffrey S. Weinberg3, Florian Maier1, Anil Shetty4, John D. Hazle1, and R. Jason Stafford1
1Imaging Physics, MD Anderson Cancer Center, Houston, TX, United States, 2Imaging Physics, The University of Texas M.D. Anderson Cancer Center, Houston, TX, United States,3Neurosurgery, MD Anderson Cancer Center, Houston, TX, United States, 4Visualase, Inc, Houston, TX, United States

In this work we introduce a new computational methodology and for minimally-invasive MR-guided laser-induced thermal therapy for brain tumors. We also evaluate the viability of the steady-state method on real human data retrospectively.

1840.   Enlarged Perivascular Spaces: How Prevalence Might Influence Gene Therapy Trial Design
Miles Olsen1, Barbara Bendlin2, Sterling Johnson2, Jason Huston3, Benjamin Grabow1, Ethan K. Brodsky1, and Walter F. Block4
1Medical Physics, University of Wisconsin - Madison, Madison, Wisconsin, United States, 2Neuroscience, University of Wisconsin - Madison, Madison, Wisconsin, United States,3Neuroradiology, University of Wisconsin - Madison, Madison, Wisconsin, United States, 4Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin, United States

Enlarged perivascular spaces (EPVS) in the brain are suspected to act as unwanted escape routes for injected drugs during convection enhanced delivery (CED) procedures. We examined 155 subjects in an existing database to determine the prevalence of EPVS in the putamen, a part of the basal ganglia, with the aim to offer guidance on the design of Parkinson's disease gene therapy trials. The subjects in the study (average age 59.8 plus-or-minus sign 5.97 years) were at about the age of Parkinson's disease onset. The prevalence of atypical EPVS in the putamen (12%) merits consideration.

1841.   Integrating Clinical Neurosurgery Workstations Into a Real-Time System for Conducting MR-Guided Procedures
Ethan K. Brodsky1,2, Karl A. Sillay3, and Walter F. Block2,4
1Medical Physics, University of Wisconsin - Madison, Madison, WI, United States, 2Biomedical Engineering, University of Wisconsin, Madison, WI, United States, 3Neurosurgery, University of Wisconsin, Madison, WI, United States, 4Medical Physics, University of Wisconsin-Madison, Madison, WI, United States

We have previously developed and presented a system for conducting MR-guided and monitored intracerebral infusions. The system has proven successful, but has been received critically by practicing clinical neurological surgeons, who deem it to be more cumbersome than the stereotactic surgical planning workstations they are accustomed to. While flexible tools amenable to performing a variety of surgical procedures are very useful in the initial stage of experimenting with real-time MR-guided interventions, simple and polished systems are much suitable when translating these techniques to clinical use. We describe here new work to integrate our real-time targeting tools to work with the Medtronic StealthStation surgical planning workstation.

1842.   Robust Feature Based Pre-Registration of 3D MR Image to 3D B-Mode Ultrasound Image of the Liver
Chi Jun Weon1, Woo Hyun Nam1, Jung-Bae Kim2, Youngkyoo Hwang2, Won-Chul Bang2, and Jong Beom Ra1
1Electrical engineering, Korea Advanced Institute of Science and Technology, Daejeon, Korea, 2Samsung Advanced Institute of Technology, Yongin-si, Gyeonggi-do, Korea

The registration of MR images with real-time US images is beneficial in various clinical applications. In most of registration algorithm, a pre-registration scheme to obtain good initial transformation parameters is important. However, conventional methods usually require a time-consuming and inconvenient manual process for pre-alignment. Furthermore, if anatomical features are not clearly visible in an abnormal liver, it is difficult to perform the manual pre-registration procedure. In this paper, we propose an automatic and robust pre-registration algorithm of the liver. For reliable and robust registration, the algorithm uses patient-independent feature geometries such as IVC and liver surface rather than vessel bifurcations.

1843.   Proof of Concept for Transrectal MRI-Guided Prostate Biopsies Using an Optically Referenced Targeting Device
Harald Busse1, Gregor Thörmer1, Josephin Otto1, Nikita Garnov1, Tim Riedel1, Arno Schmitgen2, Axel Winkel3, Thomas Kahn1, and Michael Moche1
1Diagnostic and Interventional Radiology Department, Leipzig University Hospital, Leipzig, Saxony, Germany, 2Localite Biomedical Visualization Systems, Sankt Augustin, Germany,3Invivo Germany, Schwerin, Germany

Prostate carcinoma (PCa) is one of the most common male cancers in the western world. While digital rectal examination, prostate-specific antigen (PSA) testing and transrectal ultrasound-guided biopsies are still the primary tools for prostate diagnostics, multiparametric MRI has an emerging role in both imaging diagnostics and procedural guidance. The purpose of this work is to present a virtual real-time navigation option for transrectal MRI-guided prostate biopsies, to estimate the targeting accuracy, and to report on the preliminary clinical experience.


Wednesday, 24 April 2013 (16:00-18:00) Exhibition Hall
Software & Hardware for MR-Guided Interventions

1844.   A Simple Method to Image Time-Varying Magnetic Fields Inside the Body Using MRI.
Luis Hernandez-Garcia1, Krishan Prem Kumar2, and Jeremy Gam3
1FMRI laboratory, University of Michigan, Ann Arbor, Michigan, United States, 2FMRI laboratory, university of michigan, Ann Arbor, Michigan, United States, 3FMRI Laboratory, university of michigan, Ann Arbor, Michigan, United States

We present a simple method to map time-varying magnetic fields inside tissue using MRI. The method allows for imaging the spatial distribution of a broad spectrum of frequencies and only requires that the device in question be MR compatible and can be synchronized with the MR scanner, which can be usually be achieved via TTL lines. The main constraints of the method are that (1) it requires knowledge of the temporal characteristics of the magnetic field under scrutiny, and tight control of its timing; (2) it can only be used for low field amplitudes (in the order of a few Gauss) so that the phase gain can be kept within 0 and 2PI, which means that in most cases we must image a scaled down version of the desired field; (3) the frequency content of the waveform must be below the Larmor frequency of the tissue’s spins.

1845.   Multimodality Phantom Targeting Fluoroscopically Occult Lesions in the Fluoro Suite Using 3D MRI/CT Overlay Guidance
Ye Tao1, Tina Ehtiati2, Jesse Klostranec3, Guan Wang1, AbdEl-Monem M. El-Sharkawy4, Monica S. Pearl1, William A. Edelstein1, and Martin G. Radvany1
1Johns Hopkins School of Medicine, Baltimore, MD, United States, 2SiemensCorporate Research, Princeton, NJ, United States, 3University of Toronto School of Medicine, Toronto, Ontario, Canada, 4Johns Hopkins University, Baltimore, MD, United States

Various medical conditions require biopsy confirmation or minimally invasive image-guided interventions. MRI provides excellent visualization of anatomy and disease without ionizing radiation, but MRI interventional access is difficult and MRI compatible clinical equipment limited. CT has few equipment restrictions, but radiation exposure can be significant. Fusion/overlay of MRI and fluoroscopy suite cone-beam CT (CBCT) potentially combine the diagnostic quality of 3D MRI/CT imaging with the ease and speed of fluoroscopy and decreased radiation. We have developed a multimodality phantom containing simulated lesions occult to fluoroscopy, and have used MRI/CBCT image fusion guidance for successful simulated lesion biopsies.

1846.   Usefulness of the WiiTM Remote Controller for Image Manipulation of MR-Endoscope System
Akihiro Takahashi1, Etsuko Kumamoto2, Yuichiro Matsuoka3, and Kagayaki Kuroda3,4
1Graduate School of System Informatics, Kobe University, Kobe, Hyogo, Japan, 2Information Science and Technology Center, Kobe University, Kobe, Hyogo, Japan, 3Foundation for Kobe International Medical Alliance, Kobe, Hyogo, Japan, 4School of Information Science and Technology, Tokai University, Hiratsuka, Kanagawa, Japan

A user interface using a wireless accelerometer-based controller (WiiTM, Nintendo, Kyoto, Japan) system was developed for navigation of the MR-endoscope system. The software enables the MR volume data to rotate by rolling the controller. The angles of roll and pitch of the controller acquired by acceleration sensors were sent to the image processing work station via Bluetooth. After evaluating the noise in the Bluetooth communications with phantom examinations, the usefulness of the controlling device was validated with the porcine gastric wall MR images. The resultant image process control indicates an acceleration censor can make the image manipulation more smooth and intuitive in an interventional MR suite.

1847.   A Comparison of MR-Tracking Methods in the Presence of Severe Metallic Artifacts and Physiological Motion
Wei Wang1,2, Zion Tse3, Ravi T. Seethamraju4, Charles L. Dumoulin5, Tina Kapur1, Akila N. Viswanathan2, Robert A. Cormack2, and Ehud J. Schmidt1
1Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, United States, 2Radiation Oncology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, United States, 3Engineering, University of Georgia, Athens, GA, United States, 4MR R&D, Siemens Healthcare, Boston, MA, United States, 5Radiology, Cincinnati Children's Hospital, Cincinnati, OH, United States

The presence of metal in MR-guided interventional procedures affects MR-tracking quality by causing static magnetic field and radiofrequency field inhomogeneities. A custom-built carbon fiber catheter for radiation bracytherapy applications was tested using different MR-tracking methods (zero-phase reference and Hadamard multiplexing schemes without or with phase-filed dithering (PFD) strategy). The test environment included surrounding metallic needles and simulated physiological motions from a motional platform. Results showed an MR-tracking capability at 40 fps and 0.6 multiplication sign 0.6 multiplication sign 0.6 mm3 and demonstrated that the Hadamard scheme produced a more accurate and robust result than zero-phase-reference, and the use of PFD dramatically enhanced both tracking schemes.

1848.   Remote Tuning and Matching Adjustment of Intra-Cavitary RF Coil for Integrated MR-Endoscope System
Yuichiro Matsuoka1,2, Yoshinori Morita2, Hiromu Kutsumi2, Takeshi Azuma2, and Kagayaki Kuroda1,3
1Department of Research and Development, Foundation for kobe international medical alliance, Kobe, Hyogo, Japan, 2Department of Internal Medicine, Kobe University Graduate School of Medicine, Kobe, Hyogo, Japan, 3School of Information Science and Technology, Tokai University, Hiratsuka, Kanagawa, Japan

The remote tuning and matching function for intra-cavitary RF coil placed inside the stomach was developed to obtain high quality images of the gastric wall by the integrated MR-endoscope system. The remote tuning and matching circuit consisted of non-magnetic variable capacitors and inductors, and it was placed outside the bore to manually adjust the resonant characteristic of the coil. The SNR of phantom image was improved up to 131 % by using this function. The basic performance of the remote tuning and matching was demonstrated and would be useful for providing high quality images to help diagnosis of GI disease.

1849.   Synergy Between K-Space Inverse-Hanning Filtering and CoRASOR Reconstruction for Positive Contrast Visualization of Interventional Devices
Peter R. Seevinck1, Hendrik de Leeuw1, and Chris J.G. Bakker1
1Imaging department, Image Sciences Institute, Utrecht, Utrecht, Netherlands

The aim of this work is to investigate the possible synergy between k-space inverse-Hanning filtering and coRASOR for background suppressed positive contrast device visualisation. For visualisation of brachytherapy seeds in ex vivo tissue, Inverse-Hanning filtering of k-space was demonstrated to be effective in suppressing background signal, clearly increasing CNR, however, at the cost of blurring in image space.