Chao Zou¹, Huan Shen^1,2, Yiu-Cho Chung¹, Mengyue He¹, Yingjiang Liu³, Bin Fu³, Yi Zhang³, and Xin Liu^1
1Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong, China, ²School of Information Engineering, Wuhan University of Technology, Wuhan, Hubei, China, ³National Engineering Research Center of Ultrasound Medicine, Chongqing, China

Referenceless thermometry has been proposed to address the accuracy problem caused by motion artifact and magnetic field drifting. The prerequisite 2D phase unwrapping precedure is computationally inefficient. We proposed a new method based on phase differentiation estimation to avoid phase unwrapping. Phantom and ex-vivo studies show that the proposed method is less sensitive to polynomial order, more computationally efficient, and its accuracy is comparable to the standard referenceless method.

Feng Huang¹, Max Köhler², Jukka Tanttu², Wei Lin¹, and George Randy Duensing^1
1Invivo Corporation, Gainesville, FL, United States, ²Philips Healthcare, Vantaa, Finland

Image ratio constrained reconstruction (IRCR) is a generalized version of HYPR (HighlY constrained PRojection) for highly accelerated dynamic imaging. In this work, IRCR is extended to combine with parallel imaging. The multi-channel IRCR is applied to real time temperature mapping for MR guided HIFU (High Intensity Focused Ultrasound). Preliminary results for thermometry data obtained during HIFU sonications in a phantom show that net reduction factor 4.8 (R = 4.8) can be achieved with a 3-channel coil. The maximum temperature error was found to be within 1 °C (RMSE < 0.26°C) at R = 4.8.

Patrick Leonard^1,2, Rajiv Chopra^1,2, and Adrian Nachman^3,4
1Medical Biophysics, University of Toronto, Toronto, Ontario, Canada, ²Sunnybrook Research Institute, Toronto, Ontario, Canada, ³Department of Electrical Engineering, Universisty of Toronto, ⁴Department of Mathematics, Universisty of Toronto

In the current implementation of MRI-controlled transurethral ultrasound therapy the 3D spatial heating pattern is approximated by a series of 2D slices acquired every 5 – 7 seconds. Knowledge of the true 3D temperature distribution could allow for more sophisticated temperature control algorithms and improve the monitoring of nearby tissues for safety. In this work we examine the use of compressed sensing as a means of accelerating the data acquisition time, where preserving the quantitative accuracy of the temperature measurements is critical. Our results show that our treatment remains safe and effective at up to 32-fold acceleration rates.

Joshua P. Yung^1,2, David Fuentes¹, John D. Hazle^1,2, Jeffrey S. Weinberg³, and R. Jason Stafford^1,2
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 Neurosurgery, The University of Texas M.D. Anderson Cancer Center, Houston, TX, United States

Synopsis. Minimally-invasive MR-guided thermal therapies have been combined with model-based filters to improve precision and robustness of MR thermometry. When using a model, such as the bioheat transfer equation, to provide temperature estimate predictions, the propagation of the covariance matrix becomes computationally intensive. In this work, a characterization study was performed to investigate the effect of localization and model error covariance in order to provide a reduction in computational complexity while in the presence of simulated artifacts. Dice similarity coefficient and RMS error was used to evaluate the temperature model-based Kalman filter temperature estimates with MRTI and post-treatment imaging.

Raphaël Paquin^1,2, Alexandre Vignaud³, Laurent Marsac^4,5, Youliana Younan⁴, Stéphane Lehéricy^1,6, Mickaël Tanter⁴, and Jean-François Aubry^4
1CENIR - Centre de NeuroImagerie de Recherche, ICM - Institut du Cerveau et de la Moelle épinière, Paris, France, ²CRICM, Université Pierre et Marie Curie (Paris 6)/INSERM UMR_S975/CNRS UMR 7225, Paris, France, ³Siemens Healthcare, F-93527 St Denis 2, France, ⁴Institut Langevin, ESPCI ParisTech, CNRS UMR 7587, INSERM U979, Paris, France, ⁵SuperSonic Imagine, Aix en Provence, France, ⁶Groupe Hospitalier Pitié-Salpêtrière, Paris, France

Magnetic resonance acoustic radiation force imaging (MR ARFI) provides a quantitative measurement of tissue displacement induced by the acoustic radiation force. Adaptive focusing of transcranial HIFU beams requires a large number of MR ARFI images and thus calls for fast imaging techniques. This work proposes to combine a two-dimensional spin-warp MR ARFI pulse sequence with the keyhole technique. Our approach offers a compromise between spatial resolution, SNR, acquisition speed, minimal heat deposition, accurate localization of the focal spot, and could be valuable for adaptive focusing procedures.

Joshua de Bever¹, Nick Todd², Allison Payne², Mahamadou Diakite², John Hollerbach¹, and Dennis Parker^2
1School of Computing, University of Utah, Salt Lake City, Utah, United States, ²Utah Center for Advanced Imaging Research, University of Utah, Salt Lake City, Utah, United States

A 3-D pulse sequence for providing large coverage volumetric Acoustic Radiation Force Impulse (ARFI) imaging is presented. This sequence allows for safe and easy localization of an ultrasound focal spot in three dimensions and would be especially beneficial for verifying targeting accuracy before an MR guided HIFU treatment.

Jiming Zhang¹, Pei-Herng Hor¹, and Raja Muthupillai^2
1Department of Physics and Texas Center for Superconductivity, University of Houston, Houston, TX, United States, ²Diagnostic and Interventional Radiology, St. Luke's Episcopal Hospital, Houston, TX, United States

We describe a full field-of-view rapid gradient echo based technique suitable for magnetic resonance acoustic radiation force imaging with a 7 s temporal resolution, and the validation of the method in a gel phantom. The propagation of the displacement wave emanating from the ultrasound focus within the phantom material was clearly captured by the method described. The potential to measure the displacement wave speed in phantom experiments may pave way toward estimating phantom mechanical properties.

Magalie Viallon¹, Lorena Petrusca², Vincent Auboiroux², Denis Morel³, Arnaud Mueller⁴, Maria I. Vargas¹, Thomas Goget², Sylvain Terraz¹, Christoph D. Becker¹, and Rares Salomir^5
1Radiology Department, Geneva University Hospital, Geneva, Switzerland, ²Radiology Department, University of Geneva, ³Anesthesiology Department, University of Geneva, ⁴Radiology Department, HCL, CHU Lyon Sud, Lyon, France, ⁵Radiology Department, INSERM Rhone-Alpes, University of Geneva

One of the main challenge for the HIFU therapy in liver is to prevent the known high risk of collateral heating and thermal damage in the ribs and ribs-surrounding tissue. Ribs’ heating during liver MRgHIFU was a major obstacle for the translation of this technology into a clinical tool, whereas the size of the population potentially concerned by such a treatment is very large. This study investigates a new alternative to solve the problem of ribs heating, using dedicated MR-guided positioning of specific reflective strips for acoustic masking of the ribs.

William Apoutou N'DJIN^1,2, Mathieu BURTNYK^1,3, Nir LIPSMAN⁴, Michael BRONSKILL^1,2, Michael SCHWARTZ⁴, Walter KUCHARCZYK³, and Rajiv CHOPRA^1,2
1Imaging Research, Sunnybrook Research Institute, Toronto, ON, Canada, ²Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada, ³Department of Medical Imaging, University Health Network and the University of Toronto, Toronto, ON, Canada, ⁴Division of Neurosurgery, University of Toronto, Toronto, ON, Canada

The feasibility of MRI-guided interstitial ultrasound therapy in brain was studied in-vivo in a porcine model. After the insertion of the therapeutic applicator into the brain, ultrasound heating was performed under MR-thermometry control in 5 animals. The procedure was well tolerated. This minimally-invasive approach allowed large and fast brain tissue ablations (~ 7 cm3 in less than 10 min ) with high spatial control of the heating (accuracy ~2 mm). Future investigations will focus on the targeting of specific brain structures/tumors and on the control in 3D of the heat deposition, with several applications for tissue ablation or drug delivery.

William Apoutou N'DJIN^1,2, Charles MOUGENOT³, Ilya KOBELEVSKIY¹, Elizabeth RAMSAY¹, Michael BRONSKILL^1,2, and Rajiv CHOPRA^1,2
1Imaging Research, Sunnybrook Research Institute, Toronto, ON, Canada, ²Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada, ³Philips Healthcare, Toronto, ON, Canada

The feasibility of transurethral dual-frequency ultrasound focal therapy under MR-thermometry guidance has been investigated experimentally in gel phantom. The therapeutic applicator was inserted into an anatomical gel phantom including clinically approved human prostate geometry and prostate tumor mimics. Full prostate gland therapy and focal therapy strategies have been tested successfully, and allowed accurate and fast treatments (~ half an hour) of all tumor mimics spread in a large prostate (52 cm2). Focal therapy was faster and less aggressive, which can be promising for future clinical studies on MR-guided transurethral ultrasound treatment of localized prostate cancer.

Yuting Lin¹, Jeon-Hor Chen^1,2, Wei-Chin Lin², Peter T Fwu¹, Tzu-Ching Shih^2,3, Orhan Nalcioglu¹, and Min-Ying L Su^1
1Tu and Yuen Center for Functional Onco-Imaging, Department of Radiological Science, University of California, IRVINE, California, United States,²Department of Radiology, China Medical University Hospital, Taichung, Taiwan, ³Biomedical Imaging and Radiological Science, China Medical University, Taichung, Taiwan

Hypothermic cooling via an endorectal balloon (ECB) has been shown to significantly reduce long term urinary incontinence and sexual dysfunction in men after robotic radical prostatectomy. Currently, there is no treatment planning tool for ECB design to optimize the balloon temperature and application time to ensure effective nerve-sparing cooling. In this study, we established a simulation model to map the temperature distribution based on the MR images of each individual patient. This proof of principle study demonstrated that this simulation tool can potentially be used for MR-image guided treatment planning to achieve optimized ECB cooling for nerve sparing.

Dara L Kraitchman^1,2, Di Qian^1,3, Paul A Bottomley¹, and Clifford R Weiss^1
1Russell H. Morgan Department of Radiology, Johns Hopkins University, Baltimore, MD, United States, ²Department of Molecular and Comparative Pathobiology, Johns Hopkins University, Baltimore, MD, United States, ³Department of Electrical and Computer Engineering, Johns Hopkins University, Baltimore, MD, United States

MR-compatible cryoablation therapy was originally developed on low field systems to treat cancer. Ancedoctal evidence suggests that heating of the cryoprobes may occur. Using a realistic whole body phantom that approximates human body conductivity, we determined the specific absorption rate (SAR) of a clinical approved cryoablation system using fiber optic probes on a 1.5 T MR system. A standard cardiac multislice cine SSFP sequence achieved peak SAR levels of 5.4. Using a real-time SSFP sequence, transient heating changes exceeding 15°C were noted. These results should be taken into account during MR-guided cryoablation procedures.

Andriy Shmatukha¹, Xiuling Qi², Sudip Ghate², Jennifer Barry², Graham Wright², and Eugene Crystal^2
1Cardiac and Interventional Applied Science Laboratory, General Electric Healthcare, Toronto, Ontario, Canada, ²Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada

Intra-operative MRI visualization of RF ablation lesions has the potential to make cardiac electrophysiology (EP) procedures more safe and efficient. Previous studies investigated MRI visualization aspects of quasi-simultaneous lesions created few minutes apart. However, in many clinical EP procedures lesions can be separated in time by dozens of minutes, which could potentially result in different lesion appearances on MR images acquired after multiple lesion applications. This works proves experimentally that RF ablation lesions separated by up to 45 minutes can be successfully visualized by the main MRI techniques and appear similar on the resulting images.

Eugene G. Kholmovski^1,2, Sathya Vijayakumar^1,2, Ravi Ranjan^2,3, Josh Blauer^2,4, Nelly Volland^1,2, Gene Payne^1,2, Michael Guttman⁵, Pete Piferi⁵, Chris J. McGann^2,3, and Nassir F. Marrouche^2,3
1UCAIR, Department of Radiology, University of Utah, Salt Lake City, Utah, United States, ²CARMA Center, University of Utah, Salt Lake City, Utah, United States, ³Department of Cardiology, University of Utah, Salt Lake City, Utah, United States, ⁴Department of Bioengineering, University of Utah, Salt Lake City, Utah, United States, ⁵MRI Interventions Inc., Irvine, California, United States

Late gadolinium enhancement (LGE) MRI can be used to assess extent of the left atrial wall injury and validate tissue destruction during RF ablation procedure for treatment of atrial fibrillation. However, conventional contrast agents have fast clearance times making them less useful in the settings when LGE-MRI should be performed multiple times during interventional procedure. Blood pool contrast agents have noticeably longer clearance times. However, these agents have not been tested as contrast agents for LGE-MRI of acute atrial lesions. In this study, we examine applicability of blood pool contrast agent to visualize acute atrial lesions.

Ashvin K George¹, Eugene G Kholmovski¹, and Nassir F Marrouche^1
1CARMA Center, University of Utah, Salt Lake City, Utah, United States

We introduce a novel method to monitor the contact made between the catheter tip and the target tissue during real-time MRI guided radiofrequency ablation. It is necessary to ensure that sufficient tip-tissue contact is made, in order to (a) effectively deliver RF energy and (b) evaluate the quality of the ablation from the post-ablation electrogram. Our method uses a pencil beam navigator positioned through the tip of the catheter (that is tracked in real-time) and perpendicular to the heart wall (whose approximate location is known from a pre-acquired 3D angiography image). We present in vivo results.

Gene H Payne^1,2, Kamal Vij³, Nelly A Volland^1,2, Ravi Ranjan^2,4, Rob MacLeod^2,5, and Nassir Marrouche^2,4
1UCAIR, University of Utah, Salt Lake City, UT, United States, ²CARMA Center, University of Utah, Salt Lake City, UT, United States, ³MRI Interventions, Inc., Irvine, CA, United States, ⁴Department of Cardiology, University of Utah, Salt Lake City, UT, United States, ⁵Scientific Computing and Imaging Institute, University of Utah, Salt Lake City, UT, United States

During RF ablation procedures for the treatment of atrial fibrillation, endocardial electrogram signals are detected, recorded, and displayed for the clinician. A steerable ablation catheter is used to detect these EGM signals. With the ultimate goal of performing this atrial fibrillation treatment inside an MR scanner, it will be necessary to obtain reliable, low-noise signals inside the MR scanner. Presented are some details of the experimental setup that were required to obtain good electrogram signals on a porcine subject inside a 3T MR scanner.

Sathya Vijayakumar^1,2, Eugene G Kholmovski^1,2, Ravi Ranjan^2,3, Joshua Blauer^2,4, Kamal Vij⁵, Chris J McGann^2,3, and Nassir F Marrouche^2,3
1UCAIR, Dept. of Radiology, University of Utah, Salt Lake City, Utah, United States, ²CARMA Center, University of Utah, Salt Lake City, Utah, United States,³Dept. of Cardiology, University of Utah, Salt Lake City, Utah, United States, ⁴Scientific Computing Institute, University of Utah, Salt Lake City, Utah, United States, ⁵MRI Interventions Inc., Irvine, California, United States

Late Gadolinium Enhancement (LGE) MRI is frequently used to assess acute injury from RF ablation in the left atrium. In this work, we strive to determine the accuracy of the LGE MRI technique used to determine the gaps between acute lesions to optimize and improve the real-time MRI guided targeted RF ablation of lesion gaps.

Nelly A. Volland^1,2, Eugene G. Kholmovski^1,2, J. Rock Hadley¹, and Dennis L. Parker^1,2
1UCAIR/Radiology, University of Utah, Salt Lake City, Utah, United States, ²CARMA, University of Utah, Salt Lake City, Utah, United States

Introduction: Feasibility of developing and using local coil to perform MR thermometry in a beating heart with high sensitivity was investigated. Methods: Loop coil was designed and tested in vivo during open chest study where MR-compatible RF ablation catheter was placed inside right ventricle cavity. Results: High-resolution phase images were acquired in 76.3 ms using segmented EPI pulse sequence. Heating was observed within seconds of RF energy delivery as temperature maps were generated with both reference and referenceless calculation methods. Conclusions: Local coil was successfully used to perform MR thermometry in vivo and justify development of intra-cardiac catheter-mounted local coils.

Sukhoon Oh¹, Giuseppe Carluccio², and Christopher M Collins^1
1Center for NMR Research, Radiology, The Pennsylvania State University, Hershey, PA, United States, ²Electrical and Computer Engineering, University of Illinois at Chicago, Chicago, IL, United States

In this study, we investigate how the thermal conduction from a transmit surface coil components affects temperature increase in a subject by comparing temperature simulations and experiments at two different coil-sample distances.

Vincent Auboiroux¹, Lorena Petrusca¹, Magalie Viallon², Denis Morel³, Arnaud Muller⁴, Thomas Goget¹, Joerg Roland⁵, Sylvain Terraz², Christoph D Becker², and Rares Salomir^1,2
1Faculty of Medicine, University of Geneva, Geneva, Switzerland, ²Radiology Department, Geneva University Hospital, Geneva, Switzerland,³Anesthesiology Department, Geneva University Hospital, Geneva, Switzerland, ⁴MRI Center, Centre Hospitalier Lyon Sud, Lyon, France, ⁵Siemens Healthcare, Erlangen, Germany

An in-bore digital camera was used for the monitoring in real time of fiducial markers attached to the skin as direct estimators of the respiratory phase, in the context of interventional MRI for moving organs. The detection of the quiet-phase of exhalation based on in-bore optical acquisition allowed robust triggering of MR acquisitions (MR-ARFI and MR-thermometry) and HIFU sonications and yielded accurate ARFI and thermal maps, without measurable motion-induced artifacts. The feasibility of this “no touch” approach for the follow-up of the position in the respiratory cycle was demonstrated in vivo in sheep kidney and liver (trans-costal).

Christopher MacLellan^1,2, David Fuentes¹, Andrew Elliott¹, Jon Schwartz³, John Hazle^1,2, and R. Jason Stafford^1,2
1Imaging Physics, UT MD Anderson Cancer Center, Houston, Texas, United States, ²The University of Texas Graduate School of Biomedical Sciences at Houston, Houston, Texas, United States, ³Nanospectra Biosciences, Houston, Texas, United States

Nanoparticles must be well characterized and implemented into bioheat transfer models for full utilization in MR-guided laser interstitial thermal therapy (MRgLITT). We report on an inverse problem approach that recovers optical properties using the results of bioheat transfer simulations and MR temperature imaging. Optimized properties were found to be within 5% of the literature values for gold nanoshells and nanorods using this method. This provides a minimally invasive approach that can determine optical properties of nanoparticle mixtures without independent simulations of particle properties.

Ryan J. Larsen¹, Curtis L. Johnson², Kevin Jackson¹, Bradley P. Sutton³, and John Wang^1
1Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, IL, United States, ²Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, United States, ³Department of Bioengineering, University of Illinois at Urbana-Champaign, Urbana, IL, United States

Water proton resonance frequency shift thermometry over timescales of 20-60 min can be confounded by field drift. The field drift can be measured using chemical shift imaging (CSI), but this technique provides low temporal and spatial resolution. We demonstrate an approach that combines a series of gradient echo (GRE) scans with intermittent CSI scans. The GRE scans provide high spatial and temporal resolution and the CSI scans are used to characterize field drift, thereby allowing measurements to be performed over extended timescales.

Samuel John Fahrenholtz^1,2, David Fuentes¹, John D. Hazle^1,2, and Roger Jason Stafford^1,2
1Imaging Physics, The University of Texas M.D. Anderson Cancer Center, Houston, Texas, United States, ²The University of Texas Graduate School of Biomedical Science, Houston, Texas, United States

Thermodynamics modeling in the brain could improve the speed and efficacy of ablative thermal therapies in the brain. The addition of generalized polynomial chaos to thermodynamics modeling provides uncertainty quantification, e.g. a mean and standard deviation for a predicted treatment temperature. This provides confidence intervals to the prediction that can be compared to MR thermal imaging from water proton frequency shift. This abstract retrospectively compares MR thermal imaging from a canine brain ablation with a finite element approach to the Pennes bioheat equation; uncertainty quantification is provided by generalized polynomial chaos.

Hulong Lei¹, Chao Zou¹, Di Pan¹, Norman Beauchamp², Xiaoming Yang², Tom Matula³, and Bensheng Qiu^1,2
1Paul C. Lauterbur Research Center for Biomedical Imaging, Institute of Biomedical and Health Engineering, Chinese Academy of Sciences, Shenzhen, Guangdong, China, ²Department of Radiology, University of Washington School of Medicine, Seattle, United States, ³Applied Physics Laboratory, Center for Industrial and Medical Ultrasound, University of Washington, Seattle, United States

In this study, an ¡°closed¡± cell labeling system was designed to reduce contamination and be efficient for clinical applications, using focused ultrasound, and one experiment was conducted to validated the feasibility of the ¡°magnetosonoporation¡± (MSP) cell labeling apparatus. The results indicated that MSP is an instant, safe and efficient magnetic cell labeling technique for non-invasive MRI stem cell tracking in vivo and the design of MSP apparatus was beneficial to reduce cell contamination potential and convenient for future clinical applications.

Yingli Fu¹, Nicole Azene², Tina Ehtiati³, Aaron Flammang³, Wesley Gilson³, Judy Cook⁴, Kathleen Gabrielson², Clifford Weiss⁴, Jeff W Bulte⁴, Peter V Johnston⁵, and Dara L Kraitchman^1
1Department of Radiology and Radiological Sciences, Johns Hopkins University, Baltimore, MD, United States, ²Molecular & Comparative Pathobiology, Johns Hopkins University, Baltimore, MD, United States, ³Siemens Corporate Research, Baltimore, MD, United States, ⁴Radiology, Johns Hopkins University, Baltimore, MD, United States, ⁵Department of Medicine, Johns Hopkins University, Baltimore, MD, United States

X-ray fused with magnetic resonance imaging (XFM) takes advantage of both imaging modalities allowing cardiac function assessments and direct visualization of the vasculature. XFM guided microencapsulated stem cell delivery into the pericardium space was safe and would improve the retention of cellular therapeutics in the heart.

Martin Alexander Rube¹, Efstratios Kokkalis^1,2, Erwin Immel¹, Mariana Gueorguieva¹, Roos Eisma³, and Andreas Melzer^1
1Institute for Medical Science and Technology, University of Dundee, Dundee, United Kingdom, ²Institute of Cardiovascular Research, Ninewells Hospital and Medical School, NHS Tayside, Dundee, United Kingdom, ³Centre for Anatomy and Human Identification, University of Dundee, Dundee, United Kingdom

A novel interventional training and testing environment is being developed to facilitate training of new MR guided vascular interventions as well as testing of novel devices as guidewires, catheters or implants. The environment provides appropriate models in anatomically and clinical relevant conditions with established pulsatile flow. To demonstrate the principle, a catheterization of the femoral artery has been performed with resonant markers for catheter and passive markers for guidewire localization.

Ugur Yilmaz^1,2, Li Pan³, and Ergin Atalar^1,2
1Electrical and Electronics Engineering, Bilkent University, Ankara, Turkey, ²UMRAM, Bilkent University, Ankara, Turkey, ³Siemens Corporate Research, Center for Applied Medical Imaging, Baltimore, MD, United States

Inductively coupled catheter coils are advantageous for interventional procedures, since they require no connection to MR scanners, which reduces the difficulties such as device-handling and RF safety problems faced with active catheters. In our study, we developed and implemented one way of interactive real-time inductively coupled catheter coil tracking, using two transmit channels; from an external computer on which our interactive real-time software is installed. The software enables user to change the RF attributes of transmit channels in real-time so that the B1 polarization can be altered accordingly which affects the visualization of inductively coupled catheter.

Steven W Hetts¹, Maythem Saeed¹, Alastair J Martin^1,2, Lee Evans³, Anthony F Bernhardt³, Vincent Malba³, Fabio Settecase¹, Loi Do¹, Sammir Sullivan¹, and Mark W Wilson^1
1Radiology, UCSF, San Francisco, CA, United States, ²Radiology, UCSF, ³Microelectronics, Lawrence Livermore National Lab, Livermore, CA, United States

Endovascular navigation under MRI guidance can be facilitated by a catheter with electrical current carrying microcoils on the tip. Not only do the microcoils create a visible artifact to allow catheter tracking, but also they create a small magnetic moment that attempts to align with the strong B0 magnetic field of the MR scanner, thus permitting remote controlled catheter tip deflection. We determined through histologic analysis the upper boundary of electrical currents safely usable at 1.5T in a coil-tipped microcatheter in vivo in swine carotid arteries.

Mehmet Arcan Erturk^1,2, AbdEl-Monem M. El-Sharkawy², and Paul A. Bottomley^1,2
1Electrical & Computer Engineering Department, Johns Hopkins University, Baltimore, Maryland, United States, ²Department of Radiology, Johns Hopkins University, Baltimore, Maryland, United States

Recent work with interventional loopless antennae suggest a near-quadratic gain in signal-to-noise ratio (SNR) with field strength, and potentially safe operation at higher fields (B₀>1.5T). This work reports the theoretical and experimental SNR, and initial safety testing of the first intravascular loopless antenna at 7T. An absolute SNR gain of 5.71.5-fold was realized at 7T vs. 3T: more than 20-fold higher than at 1.5T. The probe heated <2.0°C during 15min RF exposure at an applied 4W/kg SAR. The SNR gain offers the potential for intra-vascular MRI microscopy at <<100m resolution, larger fields-of-view (FOV) and/or high-speed MRI endoscopy.

William Dominguez-Viqueira¹, Hirad Karimi², and Charles H Cunningham^1,2
1Imaging, Sunnybrook Research Institute, Toronto, Ontario, Canada, ²Dept. of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada

Susceptibility artifact–based tracking using paramagnetic markers is been used for guiding endovascular interventions in MRI, but with limited enthusiasm partly because of the image degradation that results from such devices. Recently, a susceptibility-based tracking device which can be mechanically turned ON and OFF was proposed. In this work, the device was re-computed for a three-layer design with widely available materials, scaled down to 3mm (9F) diameter and attached to a catheter to show feasibility with real-time images. The difference between the aligned and miss-aligned configurations was large in the MRI images, showing the feasibility of tracking the device.

Djordje Brujic¹, Francesca Galassi¹, Marc Rea¹, and Michael Ristic^2
1Imperial College, London, UK, United Kingdom, ²Imperial College, London, United Kingdom

We propose an algorithm for localising N fiducial markers within the imaging volume of the MR scanner to accurately track devices in real-time. Our algorithm computes the 3D position of fiducial markers from a set of 1D projections in space using a novel approach which improves previous methods. The algorithm was verified through extensive simulations, implemented and tested using wireless fiducial markers and a modified FLASH sequence. We achieved a computational time of 5 ms with 3 fiducial markers, a refresh rate of 10 times/s and a maximum error of 2.4 mm. Our algorithm is in line with the requirements of interventional procedures.

Abubakr El-Tahir^1,2, Frederic Courivaud¹, Rafael Palomar¹, and Ole Jakob Elle^1,2
1The Intervention Centre, Oslo University Hospital, Oslo, Oslo, Norway, ²Department of Informatics, University of Oslo, Oslo, Oslo, Norway

A smart robust algorithm for automatic catheter tracking in MR is proposed. The output of the catheter tracking is intended to be used in developing an automatic MR image acquisition and visualization scheme to be presented to the interventionist during catheterization procedures. In this method the catheter tip is marked with an MR traceable marker (in this case a miniature resonant circuit). Then automatic tip tracking is performed in a series of MR frames using probability map generated for each frame based on the similarity to a pre-learned template marker.

Vitaliy L. Rayz¹, Gabriel Acevedo-Bolton¹, Joseph R. Leach², Petter Dyverfeldt¹, Van Halbach¹, and David Saloner^1
1Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, CA, United States, ²University of California San Francisco, United States

MRI data were used for numerical modeling after deployment of a flow-diverting stent in a giant cerebral aneurysm. A patient-specific silicone model of the aneurysm was constructed from MRA and the stent was deployed in this phantom. Computations of the flow prior to and post the procedure were carried out and validated with 4D PC-MRI measurements. The transport of contrast through the model was numerically simulated and compared to DSA cine images acquired during the procedure. The results indicate that computational models based on MRI data can be used to evaluate the efficacy of flow-diverting stents on a patient-specific basis.

Alexander Brunner¹, Axel Joachim Krafft^1,2, Florian Maier¹, Wolfhard Semmler¹, and Michael Bock^1,3
1Dept. of Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany, ²Radiological Sciences, St. Jude Children’s Research Hospital, Memphis, Tennessee, United States, ³Department of Radiology - Medical Physics, University Hospital Freiburg, Freiburg, Germany

Julien Barbot¹, Steven Shea², Klaus Kirchberg¹, Kamal Vij³, and Sunil Patil^2
1Center for Applied Medical Imaging, Siemens corporation, Corporate Research, Princeton, NJ, United States, ²Center for Applied Medical Imaging, Siemens corporation, Corporate Research, Baltimore, MD, United States, ³MRI Interventions, Irvine, CA, United States

In order to accurately determine and estimate the micro-coil position mounted on an interventional device, a novel multi-scale tracking method is proposed by considering the projection signal of interest as a singularity smoothed by a diffusion process. The parameter estimation is then done by performing edge detection at different scales and characterizes them to find suitable patterns for a given projection signal. The resulting patterns from different scales are combined to obtain the likelihood estimation at every position. The benefits over previously proposed methods are increased robustness, low sensitivity to noise and the ability to estimate the likelihood information at every position over the field of view.

Di Xu¹, Liheng Guo¹, Aaron J. Flammang², Wesley D. Gilson², Elliot R. McVeigh¹, Jonathan S. Lewin³, Clifford R. Weiss³, and Daniel A. Herzka^1
1Department of Biomedical Engineering, Johns Hopkins School of Medicine, Baltimore, MD, United States, ²Center for Applied Medical Imaging, Siemens Corporate Research, Baltimore, MD, United States, ³Department of Radiology and Radiologic Science, Johns Hopkins School of Medicine, Baltimore, MD, United States

Low-flow vascular malformations (VMs) can be treated with image-guided sclerotherapy. In MR, T2-weighted fat-saturated imaging is used for visualizing VMs during the intervention. A contrast-prepared balanced steady-state free precession (cpSSFP) sequence is proposed to overcome the limitations of conventional T2-weighted fat-sat sequences. cpSSFP shows higher CNR efficiency and superior delineation of small fast moving structures compared to the current standard HASTE. Two additional benefits leading to better visualization of lesions and needles with cpSSFP are tunability of both T2-weighting and fat-saturation. Motion insensitivity of such a technique also makes it a logical choice for free-breathing real-time guidance.

Amit Sawant¹, and Sarang Joshi^2
1Radiation Oncology, UT Southwestern Medical Center, Dallas, TX, United States, ²Biomedical Engineering, University of Utah, Salt Lake City, Utah, United States

This work investigates real-time MRI for image-guided radiation therapy of moving and deforming lung tumors. We hypothesize that, for the task of lung radiotherapy guidance, MRI acquisition speed can be increased significantly at the cost of loss in image SNR. We present results for scans acquired from two lung cancer patients on a 1.5T scanner under free-breathing conditions and without externally administered contrast using a balanced SSFP sequence. Image acquisition times of ~6.5 frames/s were achieved for 2D time series and ~0.8 volumes/s for a 3D time series. In each case, the tumor and structures of interest were clearly delineated.

Hendrik de Leeuw¹, Marinus A Moerland², Chris J.G. Bakker¹, and Peter R Seevinck^1
1Image Sciences Institute, Utrecht, Utrecht, Netherlands, ²Radiotherapy, University Medical Center Utrecht, Netherlands

High-dose-rate brachytherapy with Iridium-192 can dramatically improve the efficiency of cancer treatment. To ensure accurate treatment, in particular for single fraction therapy, HDR requires independent treatment verification. CT imaging allows excellent HDR-source localization, but poor organ visualization and tumour delineation. Although MRI provides excellent soft tissue contrast, its geometric accuracy is usually questioned. Therefore, often CT and MRI are combined. Accurate MRI-guidance would be extremely useful for single-fraction HDR brachy-monotherapy. Herein the feasibility of near real-time Iridium source position verification using the co-RASOR imaging technique is demonstrated. The positions on co-RASOR and CT images are shown to correspond within 1mm.

Andrew B. Holbrook¹, Ronald Watkins¹, and Kim Butts Pauly^1
1Radiology, Stanford University, Stanford, CA, United States

Consumer electronics technology has advanced to create devices that are less sensitive to the harsh conditions of a magnet room. We integrated mobile architecture into our interventional procedures to facilitate imaging setup and in-room MRI scanning. A single SSID, dual antenna WiFi network was set up inside both the magnet room and control room to allow for device connectivity regardless of location. Applications for MRI control, physiology monitoring, and HIFU transducer placement were created and demonstrated on a tablet and a mobile phone. These applications allow easier monitoring and control by providing interfaces directly to the magnet-room user.

Jan Fritz¹, Paweena U-Thainual^2,3, Tamas Ungi⁴, Aaron J Flammang⁵, Gabor Fichtinger⁴, Iulian I Iordachita², and John A Carrino^1
1Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University, Baltimore, MD, United States, ²Department of Mechanical Engineering and Laboratory for Computational Sensing and Robotics, The Johns Hopkins University, Baltimore, MD, United States, ³Department of Mechanical and Materials Engineering, Queen's University, Kingston, ON, Canada, ⁴School of Computing, Queen’s University, Kingston, ON, Canada,⁵Center for Applied Medical Imaging, Siemens Corporate Research, Princeton, NJ, United States

Augmented reality navigated interventional magnetic resonance (MR) imaging can help to overcome a fundamental limitation of MR arthrography, namely the spatial separation of the two interdependent procedures of intra-articular injection of a Gadolinium-based contrast agent and diagnostic MR imaging of the respective joint. Our study shows that the novel augmented reality Image-Overlay System provides accurate and reproducible MR imaging guidance for successful shoulder and hip arthrography in human cadavers, supporting further evaluation with clinical trials.

Andrew B. Holbrook¹, and Kim Butts Pauly^1
1Radiology, Stanford University, Stanford, CA, United States

For diagnostic imaging, a single operator usually sets up, prescribes, and monitors the MRI scan, with software designed accordingly. For interventional procedures, software is still typically designed for a single operator, despite a team often being present, and despite long periods of MR inactivity due to required treatment planning after the initial scans. In this work we present collaborative MRI, where we demonstrate how to parallelize user actions to hasten patient workflow. Our initial work involved designing a software hub-and-spoke model, such that multiple devices with unique interfaces connected into the hub to interact with data and control scans.

Gregory Scott Fischer¹, Weijian Shang¹, and Hao Su^1
1Worcester Polytechnic Institute, Worcester, MA, United States

Intraoperative high-field MR imaging provides visualization of critical structures, but the ability to use that information to guide a surgical intervention is limited due to physical constraints of operating inside the scanner bore. For prostate cancer, the gold standard for diagnosis is biopsy and a common approach to treatment of localized cancer is brachytherapy seed placement – both typically performed using an alignment template. We have developed a robotic assistant that aligns the biopsy and brachytherapy needle based on interactive imaging, improving upon standard technique with greater placement precision and interactively updated MR imaging. To maintain control while significantly improving ergonomics, the physician stands beside the patient viewing real-time MR images aligned with the scan plane and inserts the needle using an MR-compatible master device that the robot mimics.

Hasnine Haque^1,2, Shigehiro Morikawa³, Shigeyuki Naka², Hiroyuki Murayama², Tohru Tani², and Tetsuji Tsukamoto^1
1Research & Development, GEHC, Hino, Tokyo, Japan, ²Department of Surgery, Shiga University of Medical Science, Ohtsu, Shiga, Japan, ³Biomedical MR Science Center, Shiga University of Medical Science, Ohtsu, Shiga, Japan

An endoscope has been used to perform procedures with a laparoscope or thoracoscope in conventional operating rooms. One of the problems linked to endoscopic surgery is its narrow field of view and an inability to view the clinical target beneath the surface. Therefore, we propose an integrated environment where surgery can be performed with MR-compatible flexible endoscope in a closed bore MR scanner, and have developed a visualization system to navigate the endoscope by continuously-acquired near real-time MR images. In this paper, preliminary results of animal experiment will be presented.

Rao P Gullapalli¹, Michael Kolz², Mingyen Ho³, George Makris¹, Alan B McMillan¹, Marc Simard², and Jaydev P Desai^3
1Magnetic Resonance Research Center, Department of Diagnostic Radiology & Nuclear Medicine, University of Maryland School of Medicine, Baltimore, MD, United States, ²Department of Neurosurgery, University of Maryland School of Medicine, Baltimore, MD, United States, ³Department of Mechanical Engineering, University of Maryland College Park, College Park, MD, United States

The development of a multi-digited minimally invasive intracranial robot (MINIR) that can be deployed through a narrow ‘corridor’ to approach and resect a tumor, and capable of operating outside the ‘line-of-sight’ under continuous MR imaging guidance is described. The robot was tested on phantoms and on pig brains for its maneuverability, and to study the effect of the robot on the signal to noise, and geometric distortion during imaging both with and without activation. The multiple digits of the robot were clearly visible under MR and the images exhibited minimal signal to noise degradation and image distortion.

Cheolpyo Hong¹, Teaho Kim², Donghoon Lee¹, Manwoo Lee³, and Bongsoo Han^1
1Department of Radiological Science, Yonsei Univ., Wonju, Gangwon-do, Korea, ²Radiation Physics Laboratory, The University of Sydney, Sydney, Australia,³Genpia Co., Wonju, Gangwon-do, Korea

The primary advantage of magnetic resonance imaging (MRI) in radiotherapy is its excellent soft tissue contrast. The accuracy of the tumor volume delineation can be improved using MRI in combination with CT during treatment planning. Recently, open-type MR systems have become attractive for image-guided radiotherapy due to their easy patient access configuration. However, geometric image distortion by imaging gradient nonlinearity hinders the practical applications of MRI in radiotherapy. In this study, we propose an image stitching algorithm to merge non-distorted images obtained at the isocenter of the magnet and demonstrate an extended field of view using the proposed geometric distortion correction technique.

Jan Fritz^1,2, Roberto B Sequeiros³, Serban Mateiescu⁴, John A Carrino¹, Risto Ojala³, Dietrich Grönemeyer⁴, and Philippe L Pereira^2,5
1Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University, Baltimore, MD, United States, ²Diagnostic and Interventional Radiology, Eberhard-Karls University Tübingen, Tübingen, Germany, ³Department of Radiology, Oulu University Hospital, Oulu, Finland,⁴Department of Radiology and Microtherapy, University of Witten/Herdecke, Bochum, Germany, ⁵Deptartment of Radiology, SLK-Kliniken Heilbronn, Germany

Musculoskeletal pediatric interventions are frequently performed under X-ray fluoroscopy and computed tomography guidance, but the procedure-related exposure to ionizing radiation raises health concerns. Because of the absence of ionizing radiation, interventional magnetic resonance (MR) imaging superbly complies with the ALARA practice mandate, however very little data exist about the efficacy and safety of pediatric MR-guided musculoskeletal procedures. Our data show that a wide variety of pediatric MR imaging-guided percutaneous musculoskeletal diagnostic and therapeutic procedures can be efficaciously performed and are safe for use in clinical practice mandating more vigilant implementation of the ALARA practice mandate in selected pediatric musculoskeletal interventions.

Jan Fritz¹, Yubo Lü¹, Kenneth C Wang¹, Paweena U-Thainual^2,3, Aaron J Flammang⁴, Avneesh Chhabra¹, and John A Carrino^1
1Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University, Baltimore, MD, United States, ²Department of Mechanical Engineering and Laboratory for Computational Sensing and Robotics, The Johns Hopkins University, Baltimore, MD, United States, ³Department of Mechanical and Materials Engineering, Queen's University, Kingston, ON, Canada, ⁴Center for Applied Medical Imaging, Siemens Corporate Research, Princeton, NJ, United States

In pelvic pain syndromes, selective nerve infiltration with a local anesthetic is used to test the hypothesis that a particular nerve is the source of pain. Diagnostic blocks require highest accuracy because they are typically used as a tool to help to make advanced management decisions such as surgery. MR neurography-guided injection procedures can increase accuracy especially in deeply situated and complex targets by the direct MR visualization of the nerve and the injectant.

Jan Fritz¹, Roberto B Sequeiros², Yubo Lü¹, Paweena U-Thainual^3,4, Aaron J Flammang⁵, Avneesh Chhabra¹, Philippe L Pereira⁶, and John A Carrino^1
1Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University, Baltimore, MD, United States, ²Department of Radiology, Oulu University Hospital, Oulu, Finland, ³Department of Mechanical Engineering and Laboratory for Computational Sensing and Robotics, Johns Hopkins University, Baltimore, MD, United States, ⁴Department of Mechanical and Materials Engineering, Queen's University, Kingston, ON, Canada,⁵Center for Applied Medical Imaging, Siemens Corporate Research, Princeton, NJ, United States, ⁶Deptartment of Radiology, SLK-Kliniken Heilbronn, Heilbronn, Germany

Different concepts of combined clinical and interventional MR imaging expanded the spectrum of musculoskeletal interventional MR imaging into clinically useful procedures in children and adults. In this exhibit, we review the pertinent principles, indications, advantages, and drawbacks of interventional MR imaging relevant to musculoskeletal procedures. Minimally invasive, MR-guided techniques of percutaneous procedures are taught through illustrative case examples, including diagnostic osseous biopsy, therapeutic osseous interventions such as drill-assisted resection, soft tissue biopsy, preoperative percutaneous tumor marking, and injection procedures including selective nerve injections, epidural injections, facet joint injections, sacroiliac joint injections, discography, sympathetic blocks, and temporomandibular joint injections.