Nick Todd¹, Jaya Prakash², Henrik Odeen³, Josh de Bever⁴, Allison Payne¹, Phaneendra Yalavarthy², and Dennis L. Parker^1
1Radiology/UCAIR, University of Utah, Salt Lake CIty, UT, United States, ²Supercomputer Education and Research Centre, Indian Institute of Science, India, ³Physics, University of Utah, Salt Lake CIty, UT, United States, ⁴Computer Science, University of Utah, Salt Lake CIty, UT, United States

Large coverage 3-D temperature maps are desirable for many thermal therapy applications. Constrained reconstruction algorithms that create images from undersampled k-space data have been shown capable of providing such maps with the necessary spatial and temporal resolution. However, a large computation burden and batch reconstruction prevent the images from being available in real-time. This work attempts to overcome these challenges by developing a real-time temporally constrained reconstruction algorithm, with the goal of providing large volume 3-D temperature maps with less than 1 second latency.

Baudouin Denis de Senneville^1,2, Silke Hey^2,3, Chrit Moonen^1,2, and Mario Ries^1,2
1Imaging Division, UMC Utrecht, Utrecht, Netherlands, ²CNRS / University of Bordeaux 2, IMF, Bordeaux, France, ³Philips Healthcare, Best, Netherlands

MR-Thermometry for the guidance of HIFU interventions on moving organs should preferably have a high spatio-temporal resolution and volumetric coverage to allow observing the temperature with a high precision. This study investigates the possibility to perform motion compensated volumetric MR-thermometry with help of a reconstruction using a Super-resolution algorithm. This allows to deal with in-plane motion in image space first and to subsequently reduce the slice thickness towards an isotropic resolution. This I improves the accuracy of MR-thermometry due to the reduced partial volume effect.

Baudouin Denis de Senneville^1,2, Sébastien Roujol^2,3, Silke Hey^2,4, Chrit Moonen^1,2, and Mario Ries^1,2
1Imaging Division, UMC Utrecht, Utrecht, Netherlands, ²CNRS / University of Bordeaux 2, IMF, Bordeaux, France, ³Cardiovascular Division, Beth Israel Deaconess, Medical Center, Harvard Medical School, Boston, United States, ⁴Philips Healthcare, Best, Netherlands

Volumetric real time MR-thermometry on moving organs for therapy guidance is challenging. As a result, recent efforts focused on the possibility to exploit the physical knowledge of the heating process for the artefact free reconstruction of 3D MR-temperature maps from under-sampled MR-data. This study investigates the possibility to reconstruct continuous volumetric temperature data from spatio-temporally under-sampled 3D MR-temperature maps using an Extended Kalman Filter with the bio-heat transfer equation as the model predictor. The proposed method was characterized with in-vivo HIFU experiments on porcine kidney.

Peng Wang¹, Madhav Venkateswaran², Krishna Kurpad³, and Orhan Unal^1
1Medical Physics, University of Wisconsin - Madison, Madison, Wisconsin, United States, ²Electrical and Computer Engineering, University of Wisconsin - Madison, Madison, Wisconsin, United States, ³Radiology, University of Wisconsin - Madison, Madison, Wisconsin, United States

Proton resonance frequency (PRF) shift-based MR thermometry provides a non-invasive temperature mapping method for monitoring the progress of RF ablation therapies. Multi-baseline and referenceless methods have been used to address the complications caused by motion in standard PRF method. In this work, we present a computationally efficient and simplified real-time hybrid (multi-baseline + referenceless) MR thermometry technique for monitoring MR-guided thermal therapies.

Juan Camilo Plata¹, Andrew Holbrook¹, Punit Prakash², Vasant Salgaonkar², Peter Jones², Chris Diederich², Graham Sommer¹, and Kim Butts Pauly^1
1Stanford University, Stanford, CA, United States, ²University of California, San Francisco, San Francisco, CA, United States

Monitoring tissue viability during thermal therapies is critical for assessing treatment progress and safety. Temperature and thermal dose measurements do not provide physiological response information and hence are indirect measurements of tissue viability. Diffusion weighted MRI (DWI) has been used to assess tissue viability following thermal treatment of the prostate. Following treatment, dead tissue presents a 36% reduction in the apparent diffusion coefficient (ADC). We obtained interleaved ADC and temperature measurements in order to determine the onset of the 36% reduction and whether it can be used as an indicator of tissue necrosis.

Eva Rothgang^1,2, Wesley D. Gilson^2,3, Li Pan^2,3, Jörg Roland⁴, Klaus J. Kirchberg², Frank Wacker^3,5, Joachim Hornegger¹, and Christine H. Lorenz^2,3
1Pattern Recognition Lab, Department of Computer Science, Friedrich-Alexander University, Erlangen, Germany, ²Center for Applied Medical Imaging, Siemens Corporate Research, Baltimore, Maryland, United States, ³Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University, Baltimore, Maryland, United States, ⁴Siemens Healthcare, Erlangen, Germany, ⁵Department of Radiology, Hannover Medical School, Hannover, Germany

MR-guided thermal ablations are still primarily performed at tertiary care centers due to the complex workflow. We present a fully integrated system supporting the key workflow steps planning, targeting, and monitoring. Real-time, multi-slice pulse sequences are combined with image-based methods for advanced planning, intelligent automatic slice alignment and enhanced thermal mapping.

Kagayaki Kuroda^1,2, Yuta Takano¹, Makoto Obara³, Paul Baron⁴, Lam Mie Kee⁴, Wilbert L Bartels⁴, Honda Masatoshi³, and Yutaka Imai^5
1School of Information Science and Technology, Tokai University, Hiratsuka, Kanagawa, Japan, ²Department of Research and Development, Foundation for Kobe International Medical Alliance, Kobe, Hyogo, Japan, ³MR Marketing, Philips Electronics Japan Medical Systems, Shinagawa, Tokyo, Japan, ⁴Image Sciences Institute, University Medical Center Utrecht, Utrecht, Netherlands, ⁵Department of Radiology, Tokai University, Japan

Density ratios among the nine fat proton components were measured for optimizing image processing in fat-water thermometry based on methylene T1 and water proton resonance frequency. The results suggested that the relative ratios among the components were mostly temperature independent suggesting that the component ratios can be fixed in the fat signal estimation in temperature imaging.

Mahamadou Diakite¹, Henrik Odeen¹, Nick Todd², and Dennis L. Parker^2
1University of Utah, Physics and Astronomy, Salt Lake City, Utah, United States, ²Radiology, Utah Center of Advanced Imaging Research (UCAIR), Salt Lake City, Utah, United States

Accurate temperature mapping in tumor and surrounding tissue throughout a thermal therapy procedure is essential to ensure the safety and efficacy of the treatment. Methods based on the temperature dependency of the water proton resonance frequency (PRF) shift have shown the best ability to quantify temperature rises in aqueous tissues. Unfortunately, the PRF shift with temperature does not apply to lipid protons, since there is no hydrogen bonding among the methylene protons that supply the bulk of the fat signal. However, the temperature sensitivity of the spin-lattice relaxation time, T1, has been measured for a number of fatty tissues, and was found to obey a linear relationship with the temperature [1]. In the present work, we show a sequence implementation for 3D fat and water temperature imaging based on a Two Point Dixon (2PD) fat and water separation and the Variable Flip Angle (VFA) T1 mapping techniques [2].

Mahamadou Diakite¹, Allison Payne², Nick Todd², and Dennis L. Parker^2
1Physics and Astronomy, University of Utah, Salt lake, Utah, United States, ²Radiology, Utah Center of Advanced Imaging Research (UCAIR), Salt Lake City, Utah, United States

One of the main reasons focused ultrasound surgery has not been used widely in the clinical setting has been the difficulty to assess the extent of biological tissue damage due to hyperthermia. Denaturation of macromolecules within the tissues is believed to be the major factor contributing to the damage of tissues upon hyperthermia. Water in biological tissues is mostly bound to macromolecules such as: protein, fibers, membranes, and ions. As a result, the values of the relaxation time (T1) of the tissue water, which are related to the translational and rotational rates of water, represent the intrinsic probes for investigating the structural changes in the tissues at high temperature. It has been also shown that methods based on the temperature dependency of the water proton resonance frequency (PRF) shift has the best ability to quantify temperature rises in soft tissues [1]. Therefore, the goal of the present study is to investigate whether the hybrid technique (PRF-T1), can be used to quantify the threshold of tissue damage.

Daniel Gensler¹, Florian Fidler¹, Philipp Ehses¹, Marcus Warmuth², Theresa Reiter², Markus Düring^3,4, Oliver Ritter², Mark E Ladd⁵, Harald H Quick⁶, Peter M Jakob^1,3, Wolfgang R Bauer², and Peter Nordbeck^2
1Research Center Magnetic-Resonance-Bavaria, Würzburg, Germany, ²Department of Internal Medicine I - Cardiology, University Hospital Würzburg, Würzburg, Germany,³Experimental Physics 5, University Würzburg, Würzburg, Germany, ⁴Noras MRI Products GmbH, Höchberg, Germany, ⁵Erwin L. Hahn Institute for Magnetic Resonance Imaging, University Duisburg-Essen, Essen, Germany, ⁶Institute for Medical Physics, University Erlangen-Nürnberg, Erlangen, Germany

Determining the MR compatibility of medical implants is becoming increasingly relevant. In most cases, the RF-heating of implants is measured by fluoroptic probes, but these can only measure the temperature at a single point. Another method to determine heating effects is MR-thermometry using the PRFS which gives good results in homogeneous phantoms. However, in several cases the inhomogeneity of organic tissue and susceptibility changes near an implant prohibits PRFS-thermometry. The intention of this work was to develop a fast T1-based thermometry method which allows controlled MR-related heating of a medical implant while simultaneously quantifying the spatial and temporal temperature distribution.

Koji Sakai¹, Kei Yamada², Kentaro Akazawa², and Naozo Sugimoto^3
1Kyoto University, Kyoto, Kyoto, Japan, ²Kyoto Prefectural University of Medicine, ³Kyoto University

Among MR methods, the most clinically applicable assessing-the-brain-temperature method could be the post processing of the DWI. Although only applicable to the non-restricted water, it is thought to be potentially useful in assessing the thermal pathophysiology of the brain. The purpose of this study was to develop new calculation method, which does not require user depending threshold. The mean ventricular temperature of 23 healthy subjects (aged 26-75 years) were calculated by four methods: two thresholding methods and two histogram curve-fitting methods. The histogram curve-fitting methods seemed to yield more appropriate temperatures, using tympanic temperature as a reference.

Henrik Odéen^1,2, Mahamadou Diakite^1,2, Nick Todd², and Dennis L Parker^2
1Department of Physics, University of Utah, Salt Lake City, Utah, United States, ²UCAIR, Department of Radiology, University of Utah, Salt Lake City, Utah, United States

A 3D Segmented EPI pulse sequence where the polarity of the read out train changes from measurement to measurement is used in conjunction with 2 point Dixon fat/water-separation and Temporally Constrained Reconstruction to achieve N/2 ghost-free fat-only and water-only images. The phase of the fat-only images is used to create a spatially varying least square second order fit to create corrected 3D temperature maps of the water in a water/oil phantom using the PRF method. The RMS error in a cooling experiment decreased from 4.0°C to 2.5°C over 265 seconds of cooling from 70°C to 45°C.

Lorne Hofstetter¹, Hadas Ziso², Yoav Levy², Yuval Zur³, Giora Sat³, W Thomas Dixon¹, Yoav Medan², Cynthia Davis¹, Thomas K Foo¹, and Desmond Yeo^1
1GE Global Research, Niskayuna, New York, United States, ²InSightec, Tirat Carmel, Israel, ³GE Healthcare, Tirat Carmel, Israel

In this work, we test a newly developed fat-referenced thermometry technique during a canine prostate ablation procedure. The fat-referenced method was compared with the conventional and drift-corrected proton resonance frequency shift (PRFS) thermometry techniques. Over the 83 minute thermal monitor period, the fat-referenced method corrected for time-varying B0 field disturbances in the prostate region.

Shih-Chieh Lin¹, Teng-Yi Huang², Wen-Shiang Chen³, Jyun-Ming Tsai², Meng-Ju Wang³, Wen-Yih Isaac Tseng⁴, and Hsu-Hsia Peng^1
1Department of Biomedical Engineering and Environmental Sciences, National Tsing Hua Univisity, Hsinchu, Taiwan, ²Department of Electrical Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan, ³Department of Physical Medicine and Rehabilitation, National Taiwan University Hospital, Taipei, Taiwan, ⁴Center for Optoelectronic Biomedicine, Medical College of National Taiwan University, Taipei, Taiwan

Evaluation of longitudinal tissue property alterations following HIFU ablation is important in the monitoring of therapeutic effects. Our previous studies, presented a designed pulse sequence which can evaluate temperature and MT effect simultaneously during HIFU transmission, have been performed on ex-vivo porcine muscle studies and in-vivo rabbit thigh muscle studies. In this study, we aim to compare the complimentary information of ablated regions provided by MT effect and routine images. The FLAIR images, T1-weighted contrast-enhanced images, and MT-weighted images are acquired in long-term follow-up experimental design. Different indication of above three kinds of image contrast is demonstrated in this study.

Elizabeth Ramsay¹, Charles Mougenot², Max Kohler², Michael Bronskill³, Laurence Klotz⁴, Masoom Haider⁵, and Rajiv Chopra^1,3
1Imaging Research, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada, ²Philips Healthcare, ³Department of Medical Biophysics, University of Toronto,⁴Department of Urology, Sunnybrook Health Sciences Centre, ⁵Medical Imaging, Sunnybrook Health Sciences Centre

A segmented gradient echo EPI sequence as applied to PRF shift thermometry was evaluated in healthy human volunteers at 3T in order to determine its feasibility for MRI-controlled transurethral prostate therapy. TE values of 7-25ms, EPI factors of 5-17 and voxel sizes from 1.14mm to 2.0mm were tested. For all scan parameters and for all volunteers, the temperature standard deviation within the prostate was less than 1^oC, while the spatial distortion was less than 1mm.

Wen-Yen Chai^1,2, Po-Chun Chu², Yu-Chun Lin¹, Jiun-Jie Wang³, Yau-Yau Wai¹, Tzu-Chen Yen⁴, and Hao-Li Liu^2
1Department of Diagnostic Radiology, Chang Gung Memorial Hospital Linkou, Taoyuan, Taiwan, ²Department of Electrical Engineering, Chang-Gung University, Taoyuan, Taiwan, ³Department of Medical Image and Radiological Sciences, Chang-Gung University, ⁴Chang Gung Memorial Hospital Linkou, Taoyuan, Taiwan

Microbubble-enhanced burst-mode focused ultrasound (FUS) can disrupt the blood-brain barrier (BBB), and only sustained for a limited duration (usually a few hours). Two DSC-MRI were acquired at 10/150 mins after sonication to generate two permeability maps Ktrans/ Ve. The mean values of Ktrans/ Ve. at 150 mins. were obviously decrease 60% /64% when compared with 10 mins. This implies the local permeability change induced from FUS-induced BBB-disruption were highly dynamic.

Andreia Silva^1,2, Angelika Hoffmann¹, Alexander Klibanov¹, Max Wintermark¹, Sara Reis¹, John Mugler III¹, and Jaime Mata^1
1Radiology & Medical Imaging, University of Virginia, Charlottesville, Virginia, United States, ²IBEB -FCUL, Universidade de Lisboa, Lisboa, Portugal

The use of contrast agents and therapeutic agents in the brain is limited by the blood-brain barrier (BBB), which restricts their entry into the brain. Focal or regional opening of the BBB in a non-invasive and controlled way may provide the administration of specifically targeted therapeutic agents to a localized area. The purpose of this work was to characterize the opening of the BBB temporally, during the 60 minutes immediately post-sonication with microbubbles; this is important to determine the optimal time window to administer intra-venous brain therapeutic agents.

Po-Chun Chu¹, Wen-Yen Chai^1,2, Jiun-Jie Wang³, Tzu-Chen Yen⁴, and Hao-Li Liu^1
1Department of Electrical Engineering, Chang-Gung University, Taoyuan, Taiwan, Taiwan, ²Department of Diagnostic Radiology, Chang-Gung University and Memorial Hospital, Linkou, Taiwan, Taiwan, ³Department of Medical Image and Radiological Sciences, Chang-Gung University, Taoyuan, Taiwan, Taiwan, ⁴Molecular Imaging Center, Chang-Gung University and Memorial Hospital, Linkou, Taiwan, Taiwan

We use magnetic-resonance relaxivity technology to perform quantitative PK/PD analysis of small molecule in BBB animal model. Area-under-curve (AUC) map were then transferred from a series of time-dependent R1 maps to perform PD characteristic of Gd-DTPA in order to reflect Evans blue permeate dynamics. The analyzed accumulated R1 relaxivity provide high correlation with the Evans blue, implies that the R1-based pharmacodynamic analysis provide reasonable mapping to the permeability of the Evans blue into the BBB-disrupted region. This study provides an improved quantitative MR protocol for analyze the therapeutic molecule leakage when using focused ultrasound to induce BBB disruption for future brain drug delivery.

Enzo Terreno¹, Pierangela Giustetto¹, Silvia Rizzitelli¹, Cinzia Boffa¹, Daniela Delli Castelli¹, and Silvio Aime^1
1Department of Chemistry and Molecular & Preclinical Imaging Centers, University of Turin, Turin, TO, Italy

This contribution deals with the use of different acoustic radiations able to trigger a non-thermal drug release from liposomes and to cause a permeabilization of the cell membranes in the lesion that facilitates the drug diffusion in the tumor mass and enables the drug to be internalized by most of the cell phenotypes of the tumor. MRI was used to provide the necessary non-invasive guide for assessing the drug distribution (as well as the tumor growth) through the use of liposomes encapsulating the clinically approved paramagnetic complex Gadoteridol.

Mario Ries^1,2, Baudouin Denis de Senneville^1,2, Yvan Regard², and Chrit Moonen^1,2
1Imaging Division, UMC Utrecht, Utrecht, Netherlands, ²CNRS / University of Bordeaux 2, IMF, Bordeaux, France

MR-guided high intensity focused ultrasound (HIFU) ablations on continuously moving organs, such as the liver and the kidney requires MRI to full-fill two roles simultaneously: 1) MRI has to provide anatomical information with high spatio-temporal resolution and low image latency to provide target tracking information. 2) Motion corrected MR-thermometry provides the basis for retro-active power control and allows monitoring the progression of the ablation process. This feasibility study investigates the possibility to use ultrasound (US) echography as an additional imaging modality for continuous target tracking, while performing simultaneously real-time MR-thermometry to guide the HIFU ablation process.

Bruno Madore¹, Matthew Toews¹, Chang-Sheng Mei¹, Renxin Chu¹, W. Scott Hoge¹, and Lawrence P. Panych^1
1Department of Radiology, Harvard Medical School, Brigham and Women's Hospital, Boston, MA, United States

MR-guidance for thermal ablation therapy in moving organs such as the liver is a challenging application, as it requires tracking the region targeted for ablation while simultaneously measuring temperature in and around it. A pulse sequence was implemented that presents advantages over regular gradient-echo and echo-planar sequences, both in its ability to enable motion tracking and to detect temperature changes. A software system was developed combining fast landmark-based image tracking and temperature calculation, and users were asked to visually judge the performance of the software as applied to in vivo data.

Etsuko Kumamoto^1,2, Syuhei Iwaoka², Yoshie Takao³, Daisuke Kokuryo⁴, Toshiya Kaihara², and Kagayaki Kuroda^5,6
1Information Technology and Science Center, Kobe University, Kobe, Hyogo, Japan, ²Graduate School of System Informatics, Kobe University, Kobe, Hyogo, Japan, ³Graduate School of Engineering, Kobe University, Kobe, Hyogo, Japan, ⁴Molecular Imaging Center, National Institute of Radiological Sciences, Chiba, Japan, ⁵Graduate School of Engineering, Tokai University, Hiratsuka, Japan, ⁶Foundation for Kobe International Medical Alliance, Kobe, Hyogo, Japan

In this study, we proposed two three-dimensional target tracking techniques for MRgFUS of liver. One method was based on a triangular pyramid constructed with a part of branching vessel and a target. The other method projected vertexes of the triangular pyramid onto each axis for single-dimensional tracking. We acquired series of multi-slice balanced SSFP images in sagittal plane of a healthy volunteer�fs liver under slow pace respirations and reconstructed isotropic voxel images for ease to extract a branching vessel for interest. The experimental results demonstrate feasibility of three-dimensional tracking based on portal vain tree structure.

Ron Instrella¹, Kim Butts Pauly², Will Grissom³, and Viola Rieke^4
1Electrical Engineering, Stanford University, Stanford, CA, United States, ²Radiology, Stanford University, United States, ³Biomedical Engineering, Vanderbilt University, United States, ⁴Radiology and Biomedical Imaging, University of California San Francisco, United States

Advancements in MR-guided temperature imaging have accelerated the use of focused ultrasound in clinical brain treatments; however, the currently used proton resonance frequency (PRF) baseline subtraction method is susceptible to motion. The hybrid algorithm uses both multibaseline and referenceless thermometry to produce improved temperature measurements in moving organs. In this study, we show that a pre-procedural baseline library of 13 images is sufficient for reducing motion artifacts using hybrid temperature reconstruction in the brain, in an attempt to achieve more reliable temperature measurements and minimize scan time.

Andrew B. Holbrook¹, Pauline W. Worters¹, Brian A. Hargreaves¹, and Kim Butts Pauly^1
1Radiology, Stanford University, Stanford, CA, United States

MR acoustic radiation force imaging (MR-ARFI) has been shown to be a means of visualizing high intensity focused ultrasound (HIFU) focal locations without the need for applying extensive energy with a thermal test spot. To reduce geometry distortion and improve the registration of ARFI localization compared to collected scout images, we demonstrate a modified rFOV single shot FSE (ssFSE) MR-ARFI pulse sequence. In ssFSE, the phase from the displacement manifests itself as rings of destructive cancellations in the magnitude of the MRI image and is thus easily visualized. We present initial results in phantom experiments.

Hsiung-Hao Li¹, Chung-Hsin Wang¹, Chih-Kuang Yeh¹, and Hsu-Hsia Peng^1
1Biomedical Engineering and Environmental Sciences, National Tsing Hua University, Hsinchu, Taiwan

To increase the permeability of the blood¡Vbrain barrier (BBB), using focused ultrasound (FUS) in the presence of microbubbles (MBs) is a well-known strategy for local, non-invasive, transient, and reversible BBB disruption. Gas-filled MBs itself can potentially be used as a unique MR contrast agent because of their magnetic susceptibility effect and localized manipulation via FUS cavitation. The pulse sequence of Half Fourier Acquisition Single Shot Turbo Spin Echo (HASTE) was used to real-time monitoring of signal changes of MBs during performing FUS.Different signal changes with varied conditions of MBs concentration and FUS power were demonstrated.

Nick Todd¹, Josh de Bever², Mahamadou Diakite³, Allison Payne¹, and Dennis L. Parker^1
1Radiology/UCAIR, University of Utah, Salt Lake CIty, UT, United States, ²Computer Science, University of Utah, Salt Lake CIty, UT, United States, ³Physics, University of Utah, Salt Lake CIty, UT, United States

The temperature dependence of R2* has been well validated. However, recent experiments indicate that R2* values in pork muscle are affected by an additional non-thermal processes during HIFU heating. In this abstract, we present the evidence for this "mechanical" effect and attempt to separate the changes in R2* during HIFU heating into the "mechanical" effects and the thermal effects.

Steven P Allen¹, William W Roberts², Timothy L Hall¹, Charles A Cain¹, and Luis Hernandez-Garcia^1
1Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, United States, ²Department of Urology, University of Michigan, Ann Arbor, Michigan, United States

Ultrasound based cavitation can non-invasively fractionate tissue (histotripsy) down to sub-organelle granularity. It is unknown how bio-effects may alter in vivo histotripsy lesions. Here, we use T1 and T2 weighted MRI of harvested prostates to characterize the in vivo histotripsy lesion into three zones: a liquefied focal zone, a margin of partially disrupted tissue, and a hemorrhage zone of negligible damage.

Silke M. Lechner-Greite¹, Beat Werner², Lorne W. Hofstetter³, Timo Schirmer¹, Dixon W Thomas³, Yoav Medan⁴, and Desmond Yeo^3
1Diagnostics and Biomedical Technologies, GE Global Research Europe, Garching n. Munich, Germany, ²MR-Center, University Children’s Hospital Zurich, Zurich, Switzerland,³MRI Laboratory, GE Global Research Niskayuna, Albany, NY, United States, ⁴Insightec, Tirat Carmel, Israel

We report on echo planar imaging for fast image tracking and MR thermometry in the presence of a transcranial focused ultrasound setup, where the EPI images suffer from strong spatial distortions due to eddy currents induced in the ground plane of the transducer setup. Alternative ground plane segmentation patterns are evaluated to reduce the eddy current artifacts. Performance is predicted by finite element simulation and verified by EPI scans of a spherical phantom wrapped with thin copper strips of different segmentation patterns to mimic different transducer ground plane configurations.

Alan McMillan¹, Steven Roys¹, and Rao Gullapalli^1
1Magnetic Resonance Research Center, Department of Diagnostic Radiology and Nuclear Medicine, University of Maryland School of Medicine, Baltimore, MD, United States

The ability of a conventional high-field MR scanner to function as a dynamic, flexible real-time interventional imaging tool is appealing as closed-bore systems become more open and accessible. Currently available fast imaging techniques can acquire images with a rapid frame rate, but real-time modification of the image plane requires an active or passive navigational sensor. We have developed a system to enable real-time interactive MRI on closed-bore scanner using a passive magnetic field sensor (PMFS).

Benjamin P. Grabow¹, Walter F. Block¹, Andy L. Alexander¹, Samuel A. Hurley¹, Chris D. Ross², Karl A. Sillay¹, Juan M. Santos³, William R. Overall³, Perry E. Radau⁴, Graham A. Wright⁴, and Ethan K. Brodsky^1
1University of Wisconsin, Madison, WI, United States, ²Engineering Resources Group, Inc., Pembroke Pines, FL, United States, ³HeartVista Inc., Palo Alto, CA, United States,⁴Sunnybrook Health Sciences Centre, Toronto, ON, Canada

Real-time MRI has the potential to enable many intraoperative surgical processes, but there is a great need within the MR community for extensible software platforms that can allow rapid development of tools for MR guided procedures. One such platform is based upon the RTHawk system for real-time acquisition and reconstruction and the Vurtigo system for interactive visualization. We use this platform to develop a system for performing targeted intracerebral infusions under MRI guidance. Initial testing of our system in phantoms and ex vivo brains has shown targeting accuracy on the order of 1-2 mm.

Harald Busse¹, Nikita Garnov¹, Gregor Thörmer¹, Thomas Kahn¹, and Michael Moche^1
1Diagnostic and Interventional Radiology Department, Leipzig University Hospital, Leipzig, Germany

Many radiological and surgical interventions are guided by preoperative or intraoperative MRI data that need to be registered to the patient, a task typically accomplished by marker-based methods. This work presents a fully automatic technique for simultaneous 3D localization of a larger (>3) number of MR-visible markers, which was generally found to be fast, accurate and very reliable. Using the example of a clinical navigation solution for closed-bore MRI scanners, the use of five instead of three markers for patient registration may significantly improve targeting accuracy. These findings are likely to apply to other MR markers and settings as well.

Robert Sheng Xu¹, and Graham Wright^1
1Medical Biophysics, University of Toronto, Toronto, Ontario, Canada

Minimally invasive cardiac surgeries often require the manipulation of an interventional catheter under imaging guidance. The latter provides a visual roadmap for targeting of a diseased region, and simultaneously tracks the anatomic position of the interventional device. MRI is a suitable modality for performing this visual guidance, as it provides excellent soft tissue contrast for depicting the cardiac structures. However, tradeoffs exist between fast acquisition times and overall image quality. In this research, a multi-scale approach is proposed to register fast real-time images and previously acquired high quality MR volumes to help improve the accuracy of MR guided procedures.

Harald Busse¹, Nikita Garnov¹, Gregor Thörmer¹, Thomas Kahn¹, and Michael Moche^1
1Diagnostic and Interventional Radiology Department, Leipzig University Hospital, Leipzig, Germany

MR fluoroscopy allows the radiologist to guide and control percutaneous interventions in the magnet of wide-bore and open scanners. This work presents an automatic scan-plane prescription that relies on a flexible optical instrument tracking. It involves a real-time pulse sequence with a proper interface for numerical scan control and a special marker-based registration scheme. The technique overcomes typical line-of-sight problems of other approaches and can be flexibly added to virtually any scanner environment. Successful implementation and experimental target approaches with subsecond image updates are demonstrated for the worst-case scenario of a long and narrow cylindrical scanner.

Felix Victor Guettler¹, Kim Winterwerber², Andreas Heinrich¹, Bernd Hamm¹, and Ulf Teichgraeber^1
1Department of Radiology, Charité - University Hospital Berlin, Berlin, Berlin, Germany, ²MGB, Berlin, Germany

The purpose of the study was to develop a bone drill for real-time interventions under MRI- and CT-guidance. The device does not influence the imaging, is able to bore through dense structures, and enables the placement of Kirschner wires. A special designed, pneumatically controlled drive system of ferrite-free components was developed. During a phantom experiment, compact bone was successfully drilled. Moreover, the drill is sterilizable. The manufacture of an MR-compatible bone drill, comparable to the power of a standard MR non-compatible system, is in principle possible. Such an engine could open new options in CT- and MRI-navigated surgery.

Yuichiro Matsuoka¹, Etsuko Kumamoto^2,3, Akihiro Takahashi³, Yoshinori Morita⁴, Hiromu Kutsumi⁴, Takeshi Azuma⁴, and Kagayaki Kuroda^1,5
1Foundation for Kobe International Medical Alliance, Kobe, Hyogo, Japan, ²Information Science and Technology Center, Kobe University, Kobe, Hyogo, Japan, ³Graduate School of System Informatics, Kobe University, Kobe, Hyogo, Japan, ⁴Kobe University School of Medicine, Kobe, Hyogo, Japan, ⁵School of Information Science and Technology, Tokai University, Hiratsuka, Kanagawa, Japan

An MR-endoscope system has been suggested to make an endoscopy precise by performing an MR imaging with an intraluminal RF coil and showing MR images and a scope view. It is not easy to decide proper imaging position quickly by intraluminal RF coil because of invisible coil location inside body. The way to find the proper imaging location by using a tracking system with the scope was established. The location was properly detected in about 40 seconds by calculating a centroid coordinate on the coil plane without general localization procedure. This function would be helpful in a clinical usage.

Eva Rothgang^1,2, and Wesley D. Gilson^2
1Pattern Recognition Lab, Department of Computer Science, Friedrich-Alexander University, Erlangen, Germany, ²Center for Applied Medical Imaging, Siemens Corporate Research, Baltimore, Maryland, United States

An increasing number of minimally-invasive percutaneous needle interventions is performed under MR guidance including biopsies, targeted drug delivery and thermal ablations. All of these procedures require the identification of a skin entry site for needle placement. Even though this sounds straightforward, it is often a time consuming process as the entry site is usually identified in an iterative fashion under real-time imaging using a fingertip or water-filled syringe. The method presented allows to rapidly, accurately, and reproducibly localize the skin entry site without the need for any additional imaging or hardware.

Sjoerd Crijns¹, Alexis Kotte¹, Jan Lagendijk¹, and Bas Raaymakers^1
1Imaging division, department of radiotherapy, UMC Utrecht, Utrecht, Utrecht, Netherlands

In MRI-guided interventions such as MR-guided HIFU and MR-guided radiotherapy, image feed-back is applied to adapt the treatment to the current state of the anatomy. To do this effectively in treatment of abdominal organs, the target location must be tracked during motion induced by patient breathing. To this end, we propose to track a single point in an image series using a Minimum Output Sum of Squares (MOSSE) filter and validate its performance. We validate the performance of this method and find that it can track targets with sub-millimetre precission while processing time per frame remains less than one millisecond.

Marc Rea¹, Donald McRobbie¹, Francesca Galassi², Djordje Brujic², Mihailo Ristic², and Ian Young^2
1Radiological Sciences Unit, Imperial College Healthcare NHS Trust, London, United Kingdom, ²Mechanical Engineering, Imperial College London, London, United Kingdom

A real-time imaging scheme employing fiducial phase encoding has been demonstrated to provide a means of uniquely identifying markers even in close proximity. Using this method, the required number of projections for 3D tracking was reduced to three.

J.S. van Gorp¹, S.P.M. Crijns², J.G. Bouwman¹, B.W. Raaymakers², C.J.G. Bakker¹, and P.R. Seevinck^1
1Image Sciences Institute, UMC Utrecht, Utrecht, Utrecht, Netherlands, ²Radiotherapy, UMC Utrecht, Utrecht, Netherlands

In this work, a 2D-phase encoded spectroscopic imaging sequence is exploited for its geometric fidelity, its insensitivity for signal dephasing due to local susceptibility differences and its ability to provide spectroscopic information to be used for water-fat decomposition and field map generation.

Miles Olsen¹, Benjamin Grabow¹, Ethan Brodsky¹, Karl Sillay¹, Andy Alexander¹, Labonny Biswas², Roey Flor², Perry Radau², Graham Wright², and Walter Block^1
1University of Wisconsin - Madison, Madison, Wisconsin, United States, ²Imaging Research, Sunnybrook Research Institute, Toronto, Ontario, Canada

Improving the understanding of convection-enhanced delivery (CED) of drugs requires easy to use software for targeting, monitoring, and evaluating the treatment zone. We concentrate here on imaging and visualizing distal cerebral vasculature that could present unwanted escape routes during possible CED treatment for Parkinson’s disease in the putamens. An imaging protocol is presented that surpasses conventional Time of Flight in visualizing the perforating arteries in the putamen, vessels too small to be of interest in clinical imaging today. An extensible open-source software platform is modified to show both vascular and T1-weighted image volumes for later catheter alignment in CED procedures.

Samuel A. Hurley¹, Do P. Tromp², Marina E. Emborg^1,3, Sachiko Ohshima-Hosoyama³, Martin Brady⁴, Raghu Raghavan⁴, Ken Kubota⁵, and Andrew L. Alexander^1,6
1Medical Physics, University of Wisconsin, Madison, WI, United States, ²Waisman Laboratory for Brain Imaging and Behavior, University of Wisconsin, Madison, WI, United States, ³Wisconsin National Primate Research Center, University of Wisconsin, Madison, WI, United States, ⁴Therataxis, Baltimore, MD, United States, ⁵Kinetics Foundation, Los Altos, CA, United States, ⁶Psychiatry, University of Wisconsin, Madison, WI, United States

Convection enhanced delivery (CED) is a method for targeted drug delivery to the brain with a uniform concentration and limited spatial extent. We present a quantitative T1 mapping approach to track infusion progress and concentration without the need for T1-shortening contrast agents, which contain heavy metals and may put patients at higher risk for Parkinson's disease progression.

Wenbo Liu¹, Hua Guo², Xiaofei Du¹, Hui Ding¹, Wenjing Zhou³, Guangming Zhang³, and Guangzhi Wang^1
1Department of Biomedical Engineering, Tsinghua University, Beijing, China, ²Center for Biomedical Imaging Research & Department of Biomedical Engineering, Tsinghua University, Beijing, China, ³Tsinghua University YuQuan Hospital, Beijing, China

MR Imaging has been widely used in neurosurgery for guiding surgeons perform more accurate and less invasive surgery. Stereo-electroencephalography (SEEG) is considered as gold standard for epileptogenic zone (EZ) location with the depth electrode insertion procedure after craniotomy. Recently, with the development of surgical navigation, minimally invasive depth electrode insertion without craniotomy has been developed with many obvious advantages. The biggest challenge of the surgery is to avoid intracranial hemorrhage during the insertion. Accurate and fine imaging and reconstruction for cortical vessel can help surgeons perform the surgical planning to avoid the hemorrhage. This study sought to develop the appropriate technique for cortical vessel imaging and visualization to avoid intracranial hemorrhage during the depth electrode insertion.

Do P.M. Tromp¹, Marina E. Emborg¹, Samuel A. Hurley¹, Nagesh Adluru¹, Martin L. Brady², Raghu Raghavan², Ken Kubota³, and Andrew L. Alexander^1
1University of Wisconsin, Madison, WI, United States, ²Therataxis, Baltimore, MD, United States, ³Kinetics Foundation, Los Altos, CA, United States

New treatments of brain diseases like Parkinson’s disease and brain tumors are focusing on direct and local delivery of therapeutics in the brain. Convection-enhanced delivery (CED) has been proposed to increase the distribution and dose of therapeutic agents in a target area beyond simple diffusion. In this project we developed an image analysis framework to retrospectively generate a normalized statistical atlas of infusion studies, which will facilitate the investigation of how different infusion factors influence the treatment outcome.

J.S. van Gorp¹, J.G. Bouwman¹, C.J.G. Bakker¹, and P.R. Seevinck^1
1Image Sciences Institute, UMC Utrecht, Utrecht, Utrecht, Netherlands

In this work, a purely-phase encoded FID spectroscopic imaging sequence is adapted to provide 2D geometrically undistorted images in a reasonable scan time and compared to conventional methods.

Peter Nordbeck^1,2, Meinrad Beer³, Marcus Wamuth¹, Daniel Gensler², Theresa Reiter¹, Herbert Köstler³, Thomas Pabst³, Peter M Jakob², Mark E Ladd⁴, Harald H Quick⁵, Wolfgang R Bauer¹, and Oliver Ritter^1
1Internal Medicine I - Cardiology, University Hospital Wuerzburg, Wuerzburg, Germany, ²Experimental Physics V, University of Wuerzburg, Wuerzburg, Germany, ³Radiology, University Hospital Wuerzburg, Wuerzburg, Germany, ⁴Diagnostic and Interventional Radiology, University Duisburg-Essen, Essen, Germany, ⁵Medical Physics, University Erlangen-Nuernberg, Erlangen, Germany

Interventional electrophysiology (EP) for diagnosis and treatment of cardiac arrhythmia is currently performed under fluoroscopic guidance, which offers poor tissue contrast and limited feedback on therapy efficacy or complications. MR guided EP has the potential to solve many of these problems, but is technically challenging and accompanied by specific additional patient risks due to the technical equipment needed in the scanner room. Our group developed an EP setup for diagnosis and therapy of arrhythmia under real time MR guidance. The results from the first clinical applications in two patients with arrhythmia resistant to conventional therapy are presented.

Maythem Saeed¹, Loi Do¹, Steven W Hetts¹, and Mark Wilson^1
1Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, Ca, United States

The purpose of this transitional study was to determine threshold microemboli volume that causes visible microinfarct on MRI and MDCT. Cardiac injury biomarkers and histochemical staining were used to confirm the presence of myocardial injury. Pigs (n=18) received either 16mm3 or 32mm3 volumes of 40-120μm diameter microemboli. Three days after intervention contrast enhanced MDCT and MRI were performed. A threshold method was used to measure microinfarct on MRI/MDCT. Creatine-kinase MB, troponin I and triphenyltetrazolium chloride stain were used to confirmed myocardial injury. MRI and MDCT may be useful in evaluating the effectiveness of new therapies and future distal filtration devices.

Krishna N Kurpad¹, Peng Wang², Madhav Venkateswaran³, Amish N Raval⁴, and Orhan Unal^2
1Radiology, University of Wisconsin, Madison, WI, United States, ²Medical Physics, University of Wisconsin, Madison, United States, ³Electrical and Computer Engineering, University of Wisconsin, Madison, United States, ⁴Medicine, University of Wisconsin, Madison, United States

The multi-mode coil, constructed on an endovascular catheter, enables three functionalities, essential for a wholly MR guided intravascular procedure, in a single device that is connected to the MR scanner through a single coaxial cable. These are 1) accurate tracking of the catheter's distal tip 2) detection of the catheter orientation and 3) high sensitivity, limited field of view imaging. In this in vivo swine study, we add a unipolar ablation tip to the distal end of the catheter and demonstrate MR guidance of the multi-mode coil into the left ventricle of the swine heart, where tissue ablation is performed.

Martin Alexander Rube¹, Patricia Seifert², Bernhard Uihlein², Dhanapriya Kakchingtabam³, Pascal André³, and Andreas Melzer^1
1Institute for Medical Science and Technology, University of Dundee, Dundee, United Kingdom, ²EPflex Feinwerktechnik GmbH, Dettingen, Germany, ³School of Physics and Astronomy (SUPA), University of St Andrews, St. Andrews, United Kingdom

A safe and reliable method for localising interventional devices is being developed to facilitate MR guided vascular intervention, which has valuable attributes (e.g. reduced radiation dose, functional information, high soft tissue contrast, and generally no need for contrast agents). The proposed device localisation aproach is based on biocompatible iron-platinum alloy (FePt) nanoparticles in a polymeric matrix and has been applied to a novel MR safe guidewire.

Kai Dierkesmann^1
1Technical University of Munich, Munich, Germany

MR-guidance of catheter based interventions offer great advantages compared to x-ray imaging. However, sophisticated interventions such as transcatheter implantations of aortic valves (TAVI) or stent-grafts cannot benefit from those advantages because MR-safe and -compatible catheter guidewires with sufficient stiffness are not available yet. The development of a completely metal free guidewire made of carbon fiber reinforced plastics approximating steel-like stiffness is a promising approach to fill this gap. Investigation of prototypes with a stiff core, a flexible atraumatic tip and friction minimizing biocompatible coating showed great improvement in safety and artefact reduction compared to a conventional steel guidewire.

Eva Rothgang^1,2, Clifford R. Weiss³, Frank Wacker⁴, Joachim Hornegger¹, Christine H. Lorenz^2,3, and Wesley D. Gilson^2,3
1Pattern Recognition Lab, Department of Computer Science, Friedrich-Alexander University, Erlangen, Germany, ²Center for Applied Medical Imaging, Siemens Corporate Research, Baltimore, Maryland, United States, ³Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University, Baltimore, Maryland, United States, ⁴Department of Radiology, Hannover Medical School, Hannover, Germany

An increasing number of minimally-invasive percutaneous needle interventions is performed under MR guidance including biopsies, targeted drug delivery and thermal ablations. However, these procedures are still mainly performed at tertiary care centers and the complexity of the current workflow is a primary barrier for more widespread adoption. This study presents software-based methods to improve time efficiency and targeting accuracy of freehand percutaneous MR-guided punctures by simplifying trajectory planning, entry point localization, and slice alignment without introducing additional equipment.

Hendrik de Leeuw¹, Peter R Seevinck¹, and Chris J.G. Bakker^1
1Image Sciences Institute, Utrecht, Utrecht, Netherlands

Accurate localization of field perturbing objects e.g. needles, catheters and brachytherapy seeds, is difficult with MRI since induced signal voids are non-specific and distorted. Center-out Radial Sampling with Off-Resonance reception (co-RASOR) has been shown to locate perturbers accurately with high positive contrast, by selecting the optimum from many off-resonance acquisitions. Herein the efficiency and flexibility is significantly increased by making multiple off-resonance reconstructions from one on-resonance acquisition and automatically extracting the optimal frequency offset. The equivalence in accuracy of co-RASOR and CT is demonstrated by a phantom experiment, its flexibility with an arbitrarily oriented biopsy needle in inhomogeneous porcine tissue.

Han Wang¹, Feng Zhang¹, Yanfeng Meng¹, Tong Zhang¹, Patrick Willis¹, Stephanie Soriano¹, Erik Ray¹, Karim Valji¹, Guixiang Zhang², and Xiaoming Yang^1
1Radiology, University of Washington, Seattle, WA, United States, ²Radiology, Shanghai First People's Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, Shanghai, China

We investigated a new technique of MRI-guided intraTIPS local agent delivery to inhibit TIPS stenosis. Six domestic pigs underwent TIPS procedure. Before placement of the stent, a custom-made microporous delivery balloon catheter was placed into the shunt, and then Motexafin gadolinium (MGd) mixed with trypan blue dye was locally delivered under dynamic MRI monitoring. The MGd/blue penetration was displayed, and the increasing of the local MR signal intensity was observed. MRI manifestations correlated well with subsequent histological examination. This technique is feasible in an animal mode, and may open new avenues to improve the long-term patency of TIPS.

Michael Moche¹, Susann Heinig¹, Gregor Thörmer¹, Nikita Garnov¹, Jochen Fuchs¹, Tim Riedel¹, Thomas Kahn¹, and Harald Busse^1
1Diagnostic and Interventional Radiology Department, Leipzig University Hospital, Leipzig, Germany

MRI is the method of choice for the definition of suspect liver lesions that are barely or not seen with ultrasound or CT imaging. A definite diagnosis is often made by histological analysis of biopsy samples. In a cylindrical 60-cm bore MRI, the remaining space is practically too small to guide and place the biopsy instrument inside the magnet. This work uses a previously described navigation solution with virtual real-time needle guidance outside the bore and optimized intermediate control scanning. A diagnostic accuracy of 89% and estimated procedure times below 40 min appear to be tolerable for clinical routine.

Alexander Yowei Sheu¹, Zhuoli Zhang¹, Weiguo Li¹, Reed A Omary^1,2, and Andrew C Larson^1,2
1Radiology, Northwestern University - Feinberg School of Medicine, Chicago, IL, United States, ²Biomedical Engineering, Northwestern University - McCormick School of Engineering and Applied Science, Evanston, IL, United States

This study aims to demonstrate transcatheter intra-arterial (IA) infusion for targeted delivery to HCC and to validate the potential of iron oxide labeling methods to visualize IA natural killer lymphocyte (NK) delivery with MRI. NKs were labeled with iron oxide nanoparticles. Liver tumors were grown in rats. Catheter was placed in proper hepatic artery; 7.0T MRI performed T2*W scans pre- and post- NK infusion. NK viability was unchanged after labeling. Labeling efficacy was >95%. Infusions significantly reduced tumor T2*. Histologic NK measurements were significantly higher in tumor than normal liver. Selective intra-hepatic delivery of labeled NKs was visualized with MRI.

Feng Zhang¹, Yanfeng Meng¹, Stephanie Soriano¹, Patrick Willis¹, David Glickerman¹, and Xiaoming Yang^1
1Radiology, University of Washington, Seattle, Washington, United States

This study was to develop a new technique of intrabiliary MRI-guided local agent delivery. We validated the feasibility of using MR to monitor, in vivo, intrabiliary delivery of MGd into the pig common bile duct walls of 6 pigs, which was confirmed by subsequent MRI-histology correlation. This new technique may open new revenues for MR-guided intrabiliary local delivery of therapeutics, such as genes and drugs, to treat malignant pancreatobiliary diseases.

Mariana Gueorguieva¹, Desmond Teck Beng Yeo², Roos Eisma³, and Andreas Melzer^1
1Institute for Medical Sciences and Technology, University of Dundee, Dundee, Scotland, United Kingdom, ²MR lab, Diagnostic & Biomedical Technologies, GE Global Research, Niskayuna, NY, United States, ³Centre for Anatomy and Human Identification, College of Life Sciences, University of Dundee, Dundee, Scotland, United Kingdom

The motivation for the present work is the observed loss of signal and contrast when Thiel-embalmed human cadavers are imaged using clinical MR sequences. Here, we present the results from B1+ magnitude mapping of embalmed cadavers. EM simulations of the B1+ distribution in a visible male model were performed using a range of tissue electrical conductivity values. Our results show that RF penetration issues begin to develop for values of electrical conductivity as low as 2.6 S/m. We conclude that diminished RF penetration due to the high conductivity of the embalming fluids is the primary mechanism that affects MR imaging.