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

4290 -4313 Thermotherapy & Thermometry A
4314 -4337 Intravascular & Percutaneous MR-Guided Interventions B

Thursday, 25 April 2013 (10:30-11:30) Exhibition Hall
Thermotherapy & Thermometry A

  Computer #  
4290.   1 Simultaneous Thermometry and T2 Mapping, to Detect Tissue Damage During Thermal Therapies
Chang-Sheng Mei1, Cheng-Chieh Cheng1,2, Lawrence P. Panych1, and Bruno Madore1
1Radiology, Harvard Medical School, Brigham and Women’s Hospital, Boston, MA, United States, 2National Taiwan University, Taipei, Taiwan

The most widely-accepted way of detecting tissue damage, with MR-guidance, involves calculating the thermal dose (TD) that was delivered. Such calculations require accurate knowledge of the entire thermal history of every piece of tissue throughout the procedure, which may be difficult to obtain especially when motion is present. We propose an approach capable of performing thermometry and T2 mapping at the same time, with the hope that damage-induced T2 changes will prove a valuable complement to TD calculations toward detecting tissue damage, especially when motion might make thermal maps unreliable.

4291.   2 Simultaneous PRF and T1-Mapping Based MR Thermometry for Monitoring High-Intensity Focused Ultrasound Ablation of Primary Bone Tumors
Adam C. Waspe1, Charles Mougenot2, Samuel Pichardo3, Thomas Looi1, Joao Amaral4, Michael Temple4, Hai-Ling Margaret Cheng5, and James M. Drake1
1Division of Neurosurgery, Hospital for Sick Children, Toronto, Ontario, Canada, 2Philips Healthcare Canada, Markham, Ontario, Canada, 3Thunder Bay Regional Research Institute, Thunder Bay, Ontario, Canada, 4Department of Medical Imaging, Hospital for Sick Children, Toronto, Ontario, Canada, 5Department of Physiology & Experimental Medicine, The Hospital for Sick Children, Toronto, Ontario, Canada

MR-guided focused ultrasound is currently used for palliation of bone metastasis pain. Temperature is monitored using the proton resonance frequency (PRF) shift technique. PRF-thermometry is limited to water-based tissues and temperature is not measured in bone and marrow, limiting its use for primary tumor treatment. We hypothesize that marrow temperature can be quantified by measuring T1 change during heating, and that the temperature distribution across the bone can be modeled from the surrounding temperatures at the bone-muscle interface and marrow. This abstract introduces a MATLAB-based research tool to simultaneously measure temperature in muscle and fat using a hybrid PRF-T1technique.

4292.   3 Improving the Temperature Accuracy of Referenceless MR Thermometry in the Presense of Susceptibility Artifact
Mengyue He1, Chao Zou1, Changjun Tie1, Wensha Guo1, Yiu-Cho Chung1, and Xin Liu1
1Paul C Lauterbur Research Centre for Biomedical Imaging, Shenzhen Key Laboratory for MRI, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong, China

In referenceless MR thermometry, large susceptibility change can affect polynomial model fitting and result in large temperature error. Here, we propose a method to improve the accuracy of referenceless method by excluding the regions with large susceptibility artifact automatically based on the local field map derived from the projection onto dipole fields (PDF) method. Phantom and ex-vivo bovine liver study showed that the method can estimate the baseline image with an error of less than 3oC even when the ROR is corrupted by large susceptibility artifact. The method will be very useful in real time monitoring of temperature changes.

4293.   4 Referenceless Thermometry Using Bloch-Siegert Phase Shift and Auto Regressive Model
Manivannan Jayapalan1
1MR Pulse Sequence Applications and System Tools Engineering, GE Healthcare, Bangalore, Karnataka, India

Thermal monitoring in Magnetic Resonance guided Focused Ultrasound (MRgFUS) treatments is a crucial step where the phase images from MR images are used to get thermal maps. One of the widely used techniques is proton resonance frequency (PRF) shift technique that involves some form of image subtraction using a baseline pre-treatment image. Subject motion and tissue deformation due to coagulation can severely distort these techniques. Self-referenced methods help to overcome this hurdle which requires some area of tissue around the area of treatment, hot zone, for polynomial fitting to estimate the baseline phase. The accuracy of the temperature map from this method mainly depends on how close the estimated phase is with baseline phase. In this work, a new technique is described, where the equivalent-baseline phase values are generated/ estimated by applying the current phase values to a model that is based out of Bloch-Siegert phase Shift obtained in run-time along the same location. The phase estimated using Bloch-Siegert phase shift matches well with the baseline phase and so the temperature variations. This method not only eliminates the need for baseline subtraction but also produces better results as the model is generated in runtime against the known values. In clinical scenario, temperature measurement at any location, at any point of treatment could be obtained without the baseline information by using the Bloch-Siegert phase shift from a known RF pulse and the current phase values. This new technique would be amenable for the MRgFUS treatments, in particular moving organs where subtraction methods fail.

4294.   5 Robust Phase Unwrapping Using a Sorted List, Multi-Clustering Algorithm -permission withheld
Florian Maier1, David T. A. Fuentes1, Jeffrey S. Weinberg2, John D. Hazle1, and R. Jason Stafford1
1Department of Imaging Physics, The University of Texas M. D. Anderson Cancer Center, Houston, TX, United States, 2Department of Neurosurgery, The University of Texas M. D. Anderson Cancer Center, Houston, TX, United States

Referenceless proton resonance frequency shift thermometry algorithms require unwrapped phase maps to estimate temperature changes. Fast, robust, and fully automated unwrapping is mandatory for online monitoring. A novel phase unwrapping algorithm is proposed. Pixels are sorted according to their magnitude values and processed in descending order. Pixel clusters are merged as soon as they are connected. A region of interest for referenceless thermometry was processed in less than 40 ms. The method was successfully tested on data acquired during thermal therapy treatments of patients. In conclusion, the algorithm works robustly in vivo and allows for online temperature monitoring without noticeable delay.

4295.   6 Non-Invasive Temperature Mapping Using Temperature-Responsive Water Saturation Shift Referencing (T-WASSR) MRI
Guanshu Liu1,2, Qin Qin2, Kannie W.Y. Chan3,4, Jeff W.M. Bulte3,4, Michael T. McMahon1,2, Peter C.M. van Zijl1,2, and Assaf A. Gilad3,4
1F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD, United States, 2Department of Radiology, Johns Hopkins University School of Medicine, Baltimore, MD, United States, 3Department of Radiology, Johns Hopkins University, Baltimore, MD, United States, 4Cellular Imaging Section, Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, MD, United States

Monitoring of temperature changes in deep-seated tissues is a necessity during the course of cancer thermotherapy. Among currently available MR temperature mapping methods, water proton resonance frequency (PRF) imaging is the most widely used technology, but it is often hampered by interference from lipid signals. We developed a new approach for assessing the water PRF through direct water saturation to overcome problems with fat resonance interference. Compared to phase mapping, the currently most popular PRF measurement method, the temperature-responsive water saturation shift referencing (T-WASSR) method was demonstrated with an improved performance in fat-containing tissue.

4296.   7 Assessment of Temperature Induced Changes of T1 and T2 Relaxation Times in the Human Brain
Christoph Birkl1, Christian Langkammer1, Johannes Haybaeck2, Christina Ernst2, Rudolf Stollberger3, Franz Fazekas1, and Stefan Ropele1
1Department of Neurology, Medical University of Graz, Graz, Austria, 2Department of Neuropathology, Institute of Pathology, Medical University of Graz, Graz, Austria, 3Institute of Medical Engineering, Graz University of Technology, Graz, Austria

In this work we investigated the temperature dependency of T1 and T2 relaxation times in the human brain. Our results confirmed the predicted temperature dependency of T1 but showed a strong difference between the brain structures. The temperature dependency of T2 is to small to measure because it is masked out by different effects. This work provides for the first time detailed temperature dependency values of the human brain and can be used to improve MR thermometry or to translate findings from postmortem MR to in-vivo data.

4297.   8 Volumetric Brain Temperature Monitoring with the MASTER Sequence: Multiple Adjacent Slice Thermometry with Excitation Refocusing
Michael Marx1, Juan C. Plata2, and Kim Butts Pauly3
1Electrical Engineering, Stanford University, Stanford, California, United States, 2Bioengineering, Stanford University, Stanford, CA, United States, 3Radiology, Stanford University, Stanford, CA, United States

The MASTER sequence is a new approach to multi-slice thermometry with longer TEs and better measurement accuracy than comparable interleaved SPGR sequences. MR-guided Focused Ultrasound (MRgFUS) has been used to treat brain disorders including essential tremor and neuropathic pain. Current treatments are monitored using a single slice thermometry. MASTER will allow for larger volumes of temperature monitoring during treatment, helping ensure patient safety by warning clinicians if undesired heating occurs in healthy brain tissue.

4298.   9 Automated Treatment of 3D Tumor Volume with Adaptive Model-Predictive Controller in vivo
Joshua de Bever1,2, Nick Todd2, Allison Payne2,3, and Robert Roemer4
1School of Computing, University of Utah, Salt Lake City, Utah, United States, 2Utah Center for Advanced Imaging Research, Salt Lake City, Utah, United States, 3Department of Radiology, University of Utah, Salt Lake City, Utah, United States, 4Department of Mechanical Engineering, University of Utah, Salt Lake City, Utah, United States

Treatment of large, complex, 3D tumor volumes using MR guided high intensity focused ultrasound (MRgHIFU) would be difficult for a human to perform efficiently and safely. The highly configurable adaptive model-predictive controller (AMPC) presented here addresses this challenge by leveraging MR thermometry as a feedback mechanism to automate MRgHIFU treatments. The AMPC dynamically identifies and adapts the heating model during treatment, obviating lengthy pre-treatment model identification, and making the controller’s predictions robust to changes in tissue properties. Tests performed in vivo show the AMPC successfully optimized the MRgHIFU treatment of 3D volumes while protecting healthy tissue.

4299.   10 Novel PRF Thermometry Method Using Spatially Selective 2DRF Excitations and a Parametric Model
Ashvin Kurian George1, Nelly A. Volland1,2, and Nassir F. Marrouche1
1CARMA Center, University of Utah, Salt Lake City, Utah, United States, 2UCAIR, University of Utah, Salt Lake City, Utah, United States

A novel method PRF thermometry method combining spatially selective 2DRF excitation with EPI projection readouts for rapid image acquisition, and estimation of temperature using a parametric model.

4300.   11 Optimization of Dual-Pathway Unbalanced Steady-State Sequences for Robust Temperature Imaging
Lawrence P. Panych1, Renxin Chu1, Chang-Sheng Mei1, Guangyi Wang1,2, W. Scott Hoge1, Matthew Toews1, and Bruno Madore1
1Department of Radiology, Harvard Medical School, Brigham and Women's Hospital, Boston, MA, United States, 2Department of Radiology, Guangdong General Hospital, Guangdong Academy of Medical Sciences, Guangzhou, Guangdong, China

In thermometry, a number of advantages have been claimed in terms of temperature-to-noise ratio (TNR) and image contrast for sampling a spin-echo like signal in addition to the usual gradient-echo signal. The present work looked at the TNR claims more closely, in the context of abdominal imaging. While TNR advantages were observed and/or simulated for almost any combination of TR and flip angle (FA) settings for kidney imaging, due to differences in relaxation times such advantages were found in the liver only for TR < 20 ms and FA > 20 degrees or so.

4301.   12 The Impact of Uncertainty in Nonlinear Temperature Dependent Constitutive Parameters on Predictive Computer Modeling of MRgLITT Procedures
David T. A. Fuentes1, Samuel J. Fahrenholtz2, Anil Shetty3, Roger J. McNichols3, Jeffrey S. Weinberg2, John D. Hazle2, and Jason Stafford2
1The University of Texas M.D. Anderson Cancer Center, Houston, TX, United States, 2MD Anderson, Houston, TX, United States, 3Visualase Inc., Houston, Tx, United States

Significant efforts are ongoing to incorporate predictive prospective computer simulation into MRgLITT procedures. Truly predictive prospective computer modeling requires substantial validation efforts and novel computer modeling techniques that incorporate the uncertainty of the input of computer model parameters. Statistical methods provide novel methodologies for modeling the complex bioheat transfer phenomena. Within the probabilistic setting of uncertainty quantification (UQ), the range of constitutive nonlinearities may be modeled through the uncertainty within the linear UQ problem. This novel modeling techniques facilitates a substantial increase in computational efficiency while maintaining the predictability in the computer modeling by incorporating the advanced bioheat transfer phenomena.

4302.   13 Predictive Magnetic Resonance Temperature Imaging with Machine Learning
Joshua P. Yung1,2, Christopher J. MacLellan1,2, Anil Shetty3, Roger J. McNichols3, John D. Hazle1,2, R. Jason Stafford1,2, and David T. A. Fuentes1,2
1Imaging Physics, The University of Texas M.D. Anderson Cancer Center, Houston, Texas, United States, 2The University of Texas Graduate School of Biomedical Sciences, Houston, Texas, United States, 3Visualase, Inc, Houston, Texas, United States

In previous studies, the Pennes bioheat transfer equation was used to predict temperature heating during thermal therapy. In this work, a non-physical model that takes a priori temperature measurements to predict future heating is used. The method was tested on in vivo data of laser induced interstitial thermal therapy of human brain. The prediction was run using two a priori time steps and three a priori time steps. In conclusion, the proposed method predicted future temperature values with uncertainty values allowing for confidence intervals. The mean and standard deviation values can offer additional information for the procedure.

4303.   14 Arbitrary Region of Interest Definition for Referenceless Magnetic Resonance Temperature Imaging 
Florian Maier1, David T. A. Fuentes1, Joshua P. Yung1,2, Kamran Ahrar3, John D. Hazle1, and R. Jason Stafford1
1Department of Imaging Physics, The 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, 3Department of Interventional Radiology, The University of Texas M. D. Anderson Cancer Center, Houston, TX, United States

Recently, a new physics-based method for referenceless proton resonance frequency shift thermometry was presented, which estimates background phase by solving the Dirichlet problem in a circular region of interest. In this work, we modified this algorithm to enable arbitrary regions of interest. The algorithm was tested with in vivo data of laser induced interstitial thermal therapy of human liver. For common ROIs in a 2D image a processing time of less than 0.1 s was found. In conclusion, the proposed algorithm enables definition of arbitrary ROIs and does not restrict users to circular ROIs.

15 Magnetic Resonance Properties of Gd-Conjugated Microbubbles for Use in MRI-Guided Focused Ultrasound: Distinguishing Intact and Fragmented Microbubbles by Relaxivity
Michael A. Boss1, Jameel A. Feshitan2, and Mark A. Borden2
1National Instiute of Standards and Technology, Boulder, CO, United States, 2Mechanical Engineering, University of Colorado, Boulder, Boulder, CO, United States

Gas-filled microbubbles can be a useful theranostic agent in MRI-guided focused ultrasound (MRIgFUS). We have investigated the relaxation properties of microbubbles to which were conjugated Gd-DOTA, and found that relaxivity is a good indicator of the microbubble's integrity. We also elucidate the possible relaxation mechanisms of these microbubbles in the intact and fragmented states.

4305.   16 Analysis of MR Thermometry Methods Using Tm-DOTMA and Water Proton : Experimental and Numerical Results
Bu S. Park1, Martin J. Lizak2, Leonardo M. Angelone1, and Sunder S. Rajan1
1CDRH/DP, FDA, Silver Spring, MD, United States, 2NIH, Bethesda, MD, United States

We present experimental results of MR thermometry using a novel lanthanide complex, Tm-DOTMA. Results from imaging the water protons and the methyl protons of Tm-DOTMA were compared, using both chemical shift imaging (CSI) and conventional water proton reference frequency (PRF) methods in a Tm-DOTMA gel phantom. In addition, the experimental results were compared with the numerical simulation results. Because Tm-DOTMA has much higher temperature sensitivity (~0.57- 0.7 ppm/°C) compared to water proton (~ 0.01 ppm/°C), the thermometry using Tm-DOTMA can detect small temperature changes with high temporal resolution using CSI method.

4306.   17 Improved Calibration of Tm-Chleates for Use in MR Thermometry
Michael A. Boss1
1National Instiute of Standards and Technology, Boulder, CO, United States

The temperature-dependence of the chemical shift agents Tm-DOTA and Tm-DOTMA was determined from 5-45 °C in vitro. Previous measurements of the chemical shift of proton residues on lanthanide-chelates had indicated a linear dependence on temperature over small temperature ranges. However, it was found that linear calibrations can lead to errors of several degrees when using the -CH°3 of Tm-DOTMA chemical shift as an MR thermometer. Our measurements over a larger temperature range indicate a non-linear dependence, and greatly improve the accuracy of MR thermometry performed with Tm-chelates.

4307.   18 Prediction of Hypothermia During Radical Prostatectomy by Using an Endorectal Cooling Balloon: A Bioheat Simulation Based on 3D Pelvic Structure Segmented on Prostate MRI
Peter T. Fwu1,2, Jeon-Hor Chen3, Yuting Lin1, Wei-Ching Lin4, Po-Jung Tseng1, Eddie Lin1, and Min-Ying Su1,2
1Center for Functional Onco-Imaging, Department of Radiological Sciences, University of California, Irvine, CA, United States, 2Department of Physics and Astronomy, University of California, Irvine, CA, United States, 3Center for Functional Onco-Imaging, Department of Radiological Sciences, University of California Irvine, Irvine, CA, United States,4Department of Radiology, China Medical University Hospital, Taichung, Taiwan

Regional hypothermia through endorectal cooling balloon (ECB) is shown capable of minimizing the long term urinary incontinence and sexual dysfunction. However, there is no tool to optimize ECB setting to reach the desired protective cooling effect. A bioheat simulation equation based on each individual patient’s own 3D anatomy is developed to model the cooling process by using the finite element method. Using this model, we evaluated the impact of geometrical distance from ECB, the balloon temperature, and the presence of blood. In addition, the effect of arterial ligation to decrease the blood perfusion to NBV was also evaluated.

4308.   19 Utility of Intra-Procedural Gadoxetate Disodium Administration During MRI-Guided Laser Ablation of Hepatic Metastases: Experience with 47 Treated Lesions
Sherif G. Nour1,2, David A. Kooby3,4, Shishir K. Maithel3,4, Charles A. Staley3,4, Hiroumi D. Kitajims1,2, William C. Small1,4, and William E. Torres1,4
1Radiology and Imaging Sciences, Emory University, Atlanta, GA, United States, 2Interventional MRI Program, Emory University, Atlanta, GA, United States, 3Surgical Oncology, Emory University, Atlanta, GA, United States, 4School of Medicine, Emory University, Atlanta, GA, United States

Adequate quantification of liver metastases and reliable targeting of subtle lesions for percutaneous ablation are current challenges leading to hepatic resections/open ablations that maybe avoidable particularly in poor surgical candidates. This investigation reports the utilization of intra-procedural gadoxetate disodium with controlled breath suspension under anesthesia for a)detecting subtle metastases not seen on pre-procedure scans in a manner analogous to using intra-operative ultrasound for metastatic mapping prior to metastatectomy; b)facilitating precise percutaneous targeting of subtle previously unapproachable lesions; c)allowing proper tailoring of ablations and inclusion of adequate safety margins around infiltrative lesions and d) enhancing ablation safety near central bile ducts.

4309.   20 Combined Use of MR-HIFU and Intra-Arterial Embolization to Reduce Heat Sink: Quantification in a Porcine Liver Model
Joost W. Wijlemans1, Mario Ries2, Martijn de Greef2, Gerald Schubert3, Max Köhler3, Mika Ylihautala3, Lambertus W. Bartels2, Chrit T.W. Moonen2, and Maurice A.A.J. van den Bosch1
1Department of Radiology, University Medical Center Utrecht, Utrecht, Netherlands, 2Image Sciences Institute, University Medical Center Utrecht, Utrecht, Netherlands, 3Philips Medical Systems MR, Vantaa, Finland

The heat sink effect, a major challenge in MR-HIFU ablation of liver tumors, can be reduced by performing intra-arterial embolization prior to MR-HIFU ablation. In this study, we investigated the synergistic effect of embolization and MR-HIFU. Six treatment cells were sonicated in a porcine liver model using PRFS thermometry. Subsequently, the liver was embolized and the treatment cells were re-sonicated. Mean temperature increase after embolization was 1.7 times higher than in perfused liver tissue. These results indicate that combination treatment with intra-arterial embolization and MR-HIFU could be an attractive treatment option for liver cancer patients in the palliative phase.

4310.   21 MR Guided High Intensity Focused Ultrasound Bone Ablation Assessed with MR, PET, and MDCT Imaging
Matthew Bucknor1, Viola Rieke1, Youngho Seo1, Randall Hawkins1, Mark Wilson1, Sharmila Majumdar1, Thomas M. Link1, and Maythem Saeed1
1Radiology & Biomedical Imaging, University of California, San Francisco, San Francisco, CA, United States

MR-guided high intensity focused ultrasound (MRgHIFU) is a powerful technique for thermally ablating focal lesions. The purpose of this study was to clearly delineate post-treatment changes in bone following HIFU on MR, PET and MDCT imaging in a swine model. Two discrete ovoid lesions were created at each proximal diaphysis and distal metadiaphysis of the right femur. Follow-up imaging studies at five days demonstrated focal ovoid hypoenhancement and decreased radiotracer uptake (dynamic 18NaF-PET) which correlated precisely to the prescribed targets. CT failed to demonstrate the lesions. This study supports the usage of MRgHIFU in treating focal lesions in bone.

4311.   22 Evaluation of a Clinically Feasible Treatment Protocol for MR-HIFU Liver Tumor Ablation in a Porcine Liver Model
Joost W. Wijlemans1, Mario Ries2, Martijn de Greef2, Gerald Schubert3, Max Köhler3, Mika Ylihautala3, Lambertus W. Bartels2, Maurice A.A.J. van den Bosch1, and Chrit T.W. Moonen2
1Department of Radiology, University Medical Center Utrecht, Utrecht, Netherlands, 2Image Sciences Institute, University Medical Center Utrecht, Utrecht, Netherlands, 3Philips Medical Systems MR, Vantaa, Finland

MR-HIFU ablation of highly perfused liver tissue requires high powers with sufficient cool down times. Therefore, ablation of larger volumes will be time consuming and challenging in the clinical setting. In this study, we evaluated a clinically feasible treatment protocol using a porcine liver model. A clinical MR-HIFU system was used to sonicate seven 4mm treatment cells in the liver, which yielded a non-perfused volume of ~2.2ml. Post mortem examination revealed no near field damage. Ablation time was 95 minutes, total treatment time 135 minutes. These results demonstrate that it is clinically feasible to ablate substantial volumes of liver tissue.

4312.   23 The Oxygenation in Different Funaki Types of Uterine Fibroids and Their Change After MR-HIFU Treatment: Evaluation with T2*
Ying Zhu1, Juan Wei2, Bilgin Keserci3, Xuedong Yang1, Rong Rong1, Jing Liu1, and Xiaoying Wang1
1Radiology, Peking University First Hospital, Beijing, China, 2Philips Research Asia, Shanghai, China, 3Philips Healthcare South Korea, Seoul, Korea

Our study showed the tendency that the T2* values of type3 fibroids were obviously higher than type1 and type2. That implied the higher oxygenation of type3 fibroids, maybe associated with the mechanism that poor effect of the MR-HIFU in type3 fibroids. The oxygenation may increase in the residual non-necrotic area of the fibroids in the short-term after MR-HIFU

4313.   24 High-Resolution MRI of Temporal Evolution of Thermal Ablation Lesions
Benu Sethi1, Andriy Shmatukha1, Mohammed Shurrab2, Jennifer Barry3, and Eugene Crystal2
1Sunnybrook Research Institute, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada, 2Arrhythmia Services, Schulich Heart Centre, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada, 3Sunnybrook Research Institute, Sunnybrook Research Institute, Toronto, Ontario, Canada

3D High-Resolution MRI is used for analyzing the internal compositions of thermal ablation lesions and their evolution after the ablation. The usefulness of different MRI techniques and their correlation to histology at different post-ablation periods is discussed. T1w MRI is shown to discriminate between coagulation necrosis and hemorrhage in acute lesions. T2w MRI is demonstrated to depict the contraction band necrosis rim as accurately as delayed enhancement at a certain period after ablation, when the ablation lesion borders become well defined, leading to satisfactory ablation lesions border delineation without Gd injection.


Thursday, 25 April 2013 (11:30-12:30) Exhibition Hall
Intravascular & Percutaneous MR-Guided Interventions B

  Computer #  
4314.   1 Transendocardial Therapeutic-Delivery Using Real-Time MRI Guidance
Shashank Sathyanarayana Hegde1, Steven M. Shea1,2, Li Pan1,2, Parag Karmarkar3, Julien Barbot4, Klaus J. Kirchberg4, Fijoy Vadakkumpadan5, Jeremy Maurer1, Judy Cook1, Natalia Trayanova5, Meiyappan Solaiyappan1, Peter V. Johnston6, and Dara L. Kraitchman1
1Radiology, Johns Hopkins University, Baltimore, Maryland, United States, 2Center for Applied Medical Imaging, Siemens Corporation, Corporate Technology, Baltimore, Maryland, United States, 3MRI Interventions, Inc., Memphis, Tennesse, United States, 4Center for Applied Medical Imaging, Siemens Corporation, Corporate Technology, Princeton, New Jersey, United States, 5Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland, United States, 6Cardiology, Johns Hopkins University, Baltimore, Maryland, United States

Catheter-based transendocardial injection offers a minimally invasive method to deliver therapeutics to the heart. MRI-guided delivery of therapeutics at 3T offers the potential for precise targeting of these therapies with superior tissue contrast over conventional X-ray fluoroscopic guidance. We demonstrate here transendocardial injection of a prototype therapeutic into the myocardium of a normal swine using real-time MR guidance and a custom active injection catheter.

2 Real-Time Monitoring for Systematic Investigation of Catheter Design and Infusion Protocol Effect on CED Performance
Benjamin Grabow1, Raghu Raghavan2, Martin Brady2, Ken Kubota3, Chris Ross4, Samuel A. Hurley5, Ethan K. Brodsky1, James Raschke3, Andrew L. Alexander6, and Walter F. Block5
1Medical Physics, University of Wisconsin - Madison, Madison, WI, United States, 2Therataxis LLC, Baltimore, MD, United States, 3Kinetics Foundation, Los Altos, CA, United States, 4Engineering Resources Group, Inc, Hialeah, FL, United States, 5Medical Physics, University of Wisconsin-Madison, Madison, WI, United States, 6Medical Physics, University of Wisconsin, Madison, WI, United States

Rapid 2D monitoring and real-time MR guidance of device insertion is used to enable systematic investigation of catheter design and infusion protocol effects on convection-enhanced delivery infusion performance.

4316.   3 Conspicuous MRI Guidewire with an Embedded Temperature Probe to Enhance RF Safety
Merdim Sonmez1,2, Dominique N. Franson1, Christina E. Saikus1, Majdi Halabi1, Anthony Z. Faranesh1, Robert J. Lederman1, and Ozgur Kocaturk1,2
1National Institutes of Health, Bethesda, MD, United States, 2Bogazici University, Istanbul, Turkey

A 0.035” MRI active guidewire with distinct tip signal, uniform shaft signal and an embedded fiberoptic temperature probe to monitor RF induced heating in real time was designed.

4317.   4 An Accurate Electromagnetic Field Model for Optimization and Selection of Intravascular Multimode Coil Geometry
Madhav Venkateswaran1, Samuel A. Hurley2, Alexey Samsanov3, Peng Wang3, Orhan Unal3, and Krishna N. Kurpad4
1Electrical and Computer Engineering, University of Wisconsin, Madison, WI, United States, 2Medical Physics, University of Wisconsin-Madison, Madison, WI, United States,3Medical Physics, University of Wisconsin, Madison, WI, United States, 4Radiology, University of Wisconsin, Madison, WI, United States

This abstract proposes a robust simulation methodology to model interventional RF coils under actual MR scanning conditions. The Finite Element Method (FEM) simulation technique has been experimentally verified for one multi-mode interventional coil (capable of performing tracking, imaging and wireless marker functions) geometry and subsequently used to do a performance analysis of the B1 field profiles produced by three other multi-mode coil geometries. The method takes into account the induced current effects typically observed in interventional coils under MR guidance and can be extended to study the field distortion due to any implantable device.

4318.   5 Intra-Arterial MRA Based Roadmapping for Magnetically-Assisted Remote Control Catheter Tracking
Alastair Martin1, Prasheel Lillaney1, Maythem Saeed1, Fabio Settlecase2, Leland Evans3, Mark Wilson1, and Steven W. Hetts3
1Radiology and Biomedical Imaging, UCSF, San Francisco, CA, United States, 2Dept of Medical Imaging, Sunnybrook Health Sciences Centre, Toronto, ON, Canada, 3Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, CA, United States

An imaging technique is presented for guiding magnetically-assisted remote control (MARC) catheters with MR methods. The technique is based on establishing an initial roadmap angiogram via intra-arterial delivery of Gd-based contrast. This mask is subsequently subtracted from later dynamic acquisitions, revealing local arterial anatomy after washout of the contrast injection. By utilizing thick 2D slices and keyhole methods high temporal resolution can be achieved in combination with low contrast requirements and low SAR. This methodology is demonstrated in a swine model where the artifacts produced by MARC catheter activation are negated, improving visualization of arterial anatomy during navigation.

4319.   6 Passive Tracking Device with a Controllable Susceptibility Effect: Demonstration with Catheter in vivo.
William Dominguez-Viqueira1, Hirad Karimi1,2, Jennifer Barry1, and Charles H. Cunningham1,2
1Imaging Research, Sunnybrook Research Institute, Toronto, Ontario, Canada, 2Medical Biophysics, University of Toronto, Toronto, Ontario, Canada

Due to the rich anatomic information available, MRI is an attractive tool for guiding endovascular interventions. In this work, a susceptibility-based tracking device which can be mechanically turned ON and OFF is implemented in a catheter tip and demonstrated in vivo. The difference between the aligned and miss-aligned configurations was large in the acquired MR images, showing the feasibility of tracking the device. Even though the device was demonstrated in a catheter, it can also be designed for different tools or devices for interventional MR procedures. In future work, faster imaging sequences will be implemented for real-time tracking.

4320.   7 MRI-Based Computations of Flow Following Endovascular Interventions
Vitaliy L. Rayz1, Gabriel Acevedo-Bolton1, Alastair J. Martin1, Van Halbach2, and David A. Saloner1
1Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, California, United States, 2Neurointerventional Radiology, University of California San Francisco, San Francisco, California, United States

Flow alterations resulting from vascular and endovascular interventions can be assessed with CFD models based on MRA and 4D PC-MRI data. In this study, preoperative and postoperative flow fields were simulated in 3 giant ICA aneurysms considered for treatment with flow-diverter stent in order to induce thrombotic occlusion of the lesions. Computations of the flow prior to and post the procedure were compared with in vivo and in vitro 4D PC-MRI measurements. The results indicate that computational models based on MRI/MRA data can be used to evaluate the efficacy of flow-diverting stents on a patient-specific basis.

4321.   8 Non-Linear Bayesian Suppression of Magnetohydrodynamic Effect for Accurate Electrocardiogram Analysis During MRI.
Julien Oster1, Matthieu Geist2, Zion Tse3, Ehud J. Schmidt3, Olivier Pietquin2, and Gari D. Clifford1
1Department of Engineering Science, University of Oxford, Oxford, United Kingdom, 2MaLIS group, Supelec, Metz, France, 3Department of Radiology, Brigham & Women’s Hospital, Harvard Medical School, Boston, MA, United States

The Electrocardiogram (ECG) is analyzed during MRI, but is restricted to R wave detection because of the Magnetohydrodynamic (MHD) effect, induced by the blood flow inside the B0 field. Emerging applications, such as MRI-guided cardiac surgery or intra-cardiac electrophysiology, requires a deeper ECG analysis. An extension of an ECG model-based Bayesian filtering framework is proposed, which accounts for the dynamics of both the MHD effect and the ECG and estimates their contributions. Quality assessment and comparison with Independent Component Analysis have been performed on three datasets of real acquisitions. Promising results demonstrate the potential for accurate ECG analysis during MRI.

4322.   9 A Dual Plane Co-RASOR Technique for Accurate and Rapid Tracking and Position Verification of an Ir-192 Source for Single Fraction HDR Brachytherapy
Hendrik de Leeuw1, Marinus A. Moerland2, Marco van Vulpen2, Peter R. Seevinck1, and Chris J.G. Bakker1
1Beeld, University Medical Center, Utrecht, Utrecht, Netherlands, 2Radiotherapy, University Medical Center, Utrecht, Utrecht, Netherlands

Treatment of prostate cancer by single fraction High-Dose-Rate (HDR) brachytherapy potentially provides an improvement in prostate cancer treatment, but safe dose delivery is mandatory. Accurate localization of a HDR source requires adequate temporal and spatial resolution, which are not easily achieved by conventional MRI. In this in vitro study, we present a dual plane version of the 3D co-RASOR technique. Two orthogonal 2D center-out encoded slices allow 3D tracking of an HDR brachytherapy source in inhomogeneous tissue. The method was shown to provide a spatial accuracy comparable to CT, with an appropriate temporal resolution, 3.2 seconds, for the intended application.

4323.   10 Dynamic 3D Localization in Real Time Using Spatial Phase-Contrast MRI  -permission withheld
Klaus-Dietmar Merboldt1, Dirk Voit1, Martin Uecker1,2, and Jens Frahm3
1Biomed. NMR Forschung, Goettingen, Germany, 2Electrical Engineering and Computer Sciences, University of California, Berkeley, California, United States, 3Biomedizinische NMR Forschungs GmbH am Max-Planck-Institut für biophysikalische Chemie, Goettingen, Germany

Spatial information may be encoded as a differential phase - similar to the principles underlying velocity-encoded phase-contrast MRI - when a gradient is applied along a perpendicular dimension of a slab and if this dimension contains a MRI-visible object at only one spatial location. The situation applies to 3D mapping of planar (2D) structures with only two projection images and different spatial phase-encoding gradients. A combination with highly undersampled radial FLASH and image reconstruction by regularized nonlinear inversion allows for serial 3D mapping in real time and, e.g. a moving hand at 40 ms temporal resolution (25 fps). If the object is restricted to a linear (1D) structure its position can be localized even faster by the acquisition of only three phase-encoded projections as demonstrated for a rapidly rotating NMR-tube at a frame rate of 200fps .

4324.   11 MR-Guidance Method for Needle Procedures Using a Dedicated Interventional MRI Suite and Device-Independent Active Tracking Markers -permission withheld
Peter Koken1, Daniel Wirtz1, Ronald Holthuizen2, Steffen Weiss1, and Sascha Krueger1
1Philips Research Laboratories, Hamburg, Germany, 2Philips Healthcare, Best, Netherlands

In this work, we propose small active but device independent MR markers in combination with a dedicated prototype platform for MR interventions. This setup could allow for fast procedures using already commercially available needle devices. Basic feasibility of the new combination was shown in a phantom experiment.

4325.   12 Optical Flow Analysis on Undersampled Radial Acquisitions for Real-Time Tracking of the Pancreas in MR Guided Radiotherapy
Bjorn Stemkens1,2, Rob H. N. Tijssen2, Cornelis A.T. van den Berg2, Jan J.W. Lagendijk2, Chrit T.W. Moonen3, Mario Ries3, and Baudouin Denis de Senneville3,4
1Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, Netherlands, 2Department of Radiotherapy, UMC Utrecht, Utrecht, Netherlands, 3Image Science Institute, UMC Utrecht, Utrecht, Netherlands, 4IMB, UMR 5251 CNRS/University Bordeaux 1/INRIA, Bordeaux, France

MR-guided radiotherapy opens up the way to track organs during radiation. Tracking using optical flow has been successfully applied on EPI images for HIFU treatments. Geometrical distortions make EPI sequences unsuitable for radiotherapy purposes. Therefore, the feasibility of optical flow on undersampled radial acquisitions is investigated. Simulations and 2D in vivo scans are used to find the tradeoff between artifacts, temporal resolution and field-of-view. In addition multi-slice in vivo data is acquired to gain insight in the 4D motion of the pancreas for real-time position verification during radiation.

4326.   13 Hand Gesture Control for Interventional MRI
Florian Maier1, Renjie He1, Alexander Brunner2, Kamran Ahrar3, John D. Hazle1, and R. Jason Stafford1
1Department of Imaging Physics, The University of Texas M. D. Anderson Cancer Center, Houston, TX, United States, 2Department of Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany, 3Department of Interventional Radiology, The University of Texas M. D. Anderson Cancer Center, Houston, TX, United States

During MRI-guided interventions, e.g. percutaneous needle biopsies, interventionalists often need to change slice positions and sequence parameters to hit the planned target position accurately and safely. In this work, we propose a new MR-based hand gesture recognition method to allow for convenient parameter changes by the interventionalist during the procedure. A pulse sequence extension was developed that acquires an additional thick slice at a fixed position. The hand shapes are classified based on their first 16 Fourier descriptors. The results show that the method allows for robust parameter modification in real time.

4327.   14 Real-Time Image Guided Targeting of MRI Compatible Robotic Assisted Breast Biopsy & Therapeutic System
Steven Roys1, Bo Yang2, Mathew Philip3, Jaydev Desai2, and Rao Gaullapalli1
1Diagnostic Radiology and Nuclear Medicine, University of Maryland School of Medicine, Baltimore, MD, United States, 2Mechanical Engineering, University of Maryland, College Park, College Park, MD, United States, 3Robin Medical, Inc., Baltimore, MD, United States

MR guided robotic assisted biopsy and therapeutic systems can be very useful as they can take advantage of the excellent soft tissue contrast especially to reach deep seated tumors that are difficult to target accurately. In this study we have evaluated a master-slave robotic system designed for breast biopsy and interventions that incorporates a position sensing device. The accuracy of the targeting under continuous imaging and the time taken to target deep seated tissues using a needle were measured. Accuracy of targeting was within 2mm and the targeting procedure time was ~20minutes.

4328.   15 Remote Detection of Implanted Neurostimulator in MRI Scanner
Pallab K. Bhattacharyya1, Erik B. Beall1, Michael D. Phillips1, and Mark J. Lowe1
1Cleveland Clinic, Cleveland, OH, United States

Deep brain stimulation (DBS) using implants is an effective symptomatic treatment of conditions like Parkinson’s disease, major depression and tremor. Functional MRI (fMRI) scans have the potential to decode the underlying mechanisms of the efficacy of DBS, and are usually performed with externalized neurostimulators. In order to perform fMRI scans with implanted neurostimulators, it is essential to monitor the ON/OFF state of the device. Using an AM receiver circuit to pick up an external RF signal from the stimulator when it is active, we have developed a prototype of a device to monitor the state of implanted neurostimulators at 3T.

4329.   16 Development of a Wireless Intra-Operative MR Geometry Planning System
Martyn Paley1, Minty Ledger2, Martin O. Leach2, Ray Hughes3, and Ali Akgun3
1Academic Radiology, University of Sheffield, Sheffield, Yorkshire, United Kingdom, 2Division of Radiotherapy and Imaging, Institute of Cancer Research, Sutton, Surrey, United Kingdom, 3Imaging, Specialty Magnetics Ltd., Northolt, Middlesex, United Kingdom

A wireless interface device has been interfaced to graphical geonetry planning software to allow non-contact remote interaction with the scan software for interventional MR. The device has been tested on a 0.17T orthopedic/neonatal and a 0.5T intra-operative MRI system.

4330.   17 Low-Profile Remote Targeting Alignment Tool for Use in MR-Guided Rigid Device Insertion
Benjamin Grabow1, Chris Ross2, Ethan K. Brodsky1, Ken Kubota3, and Walter F. Block4
1Medical Physics, University of Wisconsin - Madison, Madison, WI, United States, 2Engineering Resources Group, Inc, Hialeah, FL, United States, 3Kinetics Foundation, Los Altos, CA, United States, 4Medical Physics, University of Wisconsin-Madison, Madison, WI, United States

We developed a remote trajectory alignment tool for use with a commonly available neurosurgical brain port to enable accessible trajectory alignment with real-time image guidance in preparation for rigid-device insertion into the brain.

4331.   18 Dynamic Tracking During Interactive MRI: Implementation of an Open-Source Middleware
Felix Guettler1, Andreas Heinrich1, Peter Krauss1, Jonathan Guntermann1, and Ulf Teichgraeber1
1Department of Radiology, University Hospital Jena, Jena, Thuringia, Germany

In real-time MRI-guided interventions the FOV of interactive sequences needs to be permanently adapted according to the instruments movement. Dynamic tracking allows the automatic adaption of the FOV to the instruments location. To accomplish manufacturer independent use of dynamic tracking, a middleware was developed allowing the use of various MRIs and tracking systems. In a phantom experiment the efficiency regarding to time and success rate could be improved by using a dynamic control with a tracking system. The efficiency of interventions can be considerably improved through the middleware regarding time and hit ratio. Errors due to misunderstandings between radiologist and radiology assistant are strongly reduced.

4332.   19 High Accuracy Position Estimation of Interventional Devices Using a Controllable Passive Tracking Device
Hirad Karimi1, William Dominguez-Viqueira2, and Charles H. Cunningham1,2
1Medical Biophysics, University of Toronto, Toronto, Ontario, Canada, 2Imaging Research, Sunnybrook Research Institute, Toronto, Ontario, Canada

Tracking of interventional devices under MRI guidance remains an active area of research. However, unless active tracking methods are used, its ability to track the interventional device is always hampered by the lack of contrast between the device-related effects on magnitude images particularly when projection images are used to find the device within a large volume. In this abstract, a new tracking technique, based on a recently proposed device, has been tested that uses the generated phase profile between ON and OFF states of the device in the acquired image in order to track the device with sub-pixel accuracy.

4333.   20 Combined Pre- And Intra-Operative fMRI for Neurosurgical Guidance: Data Alignment and Bayesian Analysis.
Joerg Magerkurth1, Laura Mancini1, William Penny2, Guillaume Flandin2, John Ashburner2, Caroline Micallef1, Enrico De Vita1, Tarek A. Yousry1, John Thornton1, and Nikolaus Weiskopf2
1Department for Brain Repair and Rehabilitation, UCL Institute of Neurology, London, United Kingdom, 2Wellcome Trust Centre for Neuroimaging, University College London, London, United Kingdom

Intra-operative fMRI combined with pre-surgical fMRI planning could provide crucial information to guide neurosurgery. The intra-operative (1.5T) MR scanner at our institution presents lower signal-to-noise and contrast-to-noise ratios and significantly larger distortions than the 3T MR scanner used pre-operatively. We present a pre-processing and Bayesian analysis method for pre- and intra-operative fMRI. While classical inference identifies only activated area, the Bayesian approach labels three areas: activated, non-activated, and areas where the data do not allow for a robust classification. The method was tested on 10 healthy volunteers in a passive movement paradigm, which could also be used under anesthesia.

4334.   21 Modeling the Electric Field Distribution Within the Brain for the Treatment of Glioblastomas
Pedro C. Miranda1, Abeye Mekonnen1, Ricardo Salvador1, and Peter J. Basser2
1IBEB, Faculty of Science, University of Lisbon, Lisbon, Portugal, 2STBB, Eunice Kennedy Shriver NICHD, NIH, Bethesda, MD, United States

Electric fields are being investigated as an adjunct or an alternative to chemotherapy in the treatment of glioblastoma multiforme (GBM). We used a realistic head model constructed from MRI data to calculate the electric field distribution in the brain during the application of tumor treating fields (TTF). The calculations indicate that the electric field magnitude predicted in the brain is sufficient to arrest cell proliferation based upon in vitro experiments. However, the electric field is not uniform as it is affected by tissue heterogeneity. Patient specific models could be used in treatment planning, and for understanding outcomes of TTF therapy.

4335.   22 Thermal Ablation Using Resistive Heating by MRI Steerable Catheter
Ricky Tong1, Kanti Pallav Kolli1, Maythem Saeed1, Viola Rieke1, Leland Evans2, Steven W. Hetts2, and Mark Wilson1
1Radiology and Biomedical Imaging, UCSF, San Francisco, CA, United States, 2Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, CA, United States

Steerable endovascular catheters can be used as ablation catheters via resistive heating. Real time MR thermometry studies immediately after ablation demonstrated visible changes in temperature profile of adjacent tissue at a distance up to 1 cm from the catheter.

4336.   23 MR Guided RF Hyperthermia for Head and Neck Tumors: Simulation Guided Design of an MR Compatible RF Heating Array
Jurriaan Bakker1, Maarten Paulides1, Lorne Hofstetter2, Wouter Numan1, Gyula Kotek1, Ruben Pellicer1, Rene Verhaart1, Paolo Togni1, Gavin Houston3, Eric Fiveland4, Matthew Tarasek2, Gerard van Rhoon1, and Desmond Yeo2
1Erasmus Medical Center, Rotterdam, Netherlands, 2General Electric Global Research, Niskayuna, New York, United States, 3GE Healthcare, 's Hertogenbosch, Netherlands, 4GE Global Research Center, Niskayuna, New York, United States

Hyperthermia (40-44°C for 1h) has shown to be effective for stimulating radiotherapy for the head and neck region, but for deep application a novel applicator was build. MR thermometry has the potential to replace the current invasive fiber-optic temperature measurements and improve treatment results by better feedback. To study MR thermometry, we used simulations to design an MR compatible array applicator. The results show that this array can generate focused heat in cylindrical fat/muscle phantoms while facilitating MR thermometry.

4337.   24 Pulsatile Flow Phantom for MR-Guided Focused Ultrasound (MRgFUS) Vascular Thrombolysis and Occlusion
Thomas Hudson1, Thomas Looi1, Adam C. Waspe1, and James M. Drake1
1Neurosurgery, Hospital for Sick Children, Toronto, Ontario, Canada

Current treatment for paediatric stroke based on tPA and surgical intervention has complications. MR-guided focused ultrasound is a promising technology that can lyse clots. To optimize the acoustic parameters, a MRI compatible pulsatile flow phantom has been developed to mimic the vascular flow of a human heart. This model can be used for MR-guided focused ultrasound lysis of clot and creation of vascular occlusions.