MR Guided Interventions: Devices, Sequences, & Applications
Monday 20 April 2009
Room 313BC 11:00-13:00


Sherif G. Nour and Cengizhan Ozturk

11:00  60.

Three Dimensional Acute Radiofrequency Ablation Lesion Visualisation and Correlation with Electro-Anatomical Mapping System Ablation Points.


Benjamin R. Knowles1, Dennis Caulfield1, Aldo Rivaldi2, Michael Cooklin2, Jaswinder S. Gill2, Julian Bostock2, Reza Razavi1, Tobias Schaeffter1, Kawal S. Rhode1
Division of Imaging Sciences, King's College London, London, UK; 2Department of Cardiology, Guy's and St Thomas' NHS Foundation Trust, London, UK

    Radiofrequency ablation has become an increasingly common treatment for cardiac arrhythmias such as atrial flutter and atrial fibrillation. Delayed enhancement MRI has been previously been used to visualise the ablation lesions in the left atrium, however, determination of the ablation patterns is difficult from visualisation of the 2D slices. We present an automated method for the 3D visualisation of ablation lesions that allows for an intuitive assessment of lesion patterns. In this investigation, we demonstrate how our novel technique can be used to verify lesion locations as determined from electro-anatomical mapping systems.
11:12 61.   Four-Dimensional Transcatheter Intraarterial Perfusion MRI Monitoring of Chemoembolization for Hepatocellular Carcinoma

Dingxin Wang1, Ron Gaba2, Robert Lewandowski2, Robert Ryu2, Kent Sato2, Mary Mulcahy3,4, Riad Salem2,4, Reed Omary1,4, Andrew Larson1,4
Departments of Radiology and Biomedical Engineering, Northwestern University, Chicago, IL, USA; 2Department of Radiology, Northwestern University, Chicago, IL, USA; 3Department of Medicine, Northwestern University, Chicago, IL, USA; 4Robert H. Lurie Comprehensive Cancer Center, Northwestern University, Chicago, IL, USA


Transcatheter Intra-arterial Perfusion TRIP-MRI, using catheter-directed intraarterial (IA) contrast delivery, offers an objective method to intra-procedurally quantify tumor perfusion changes during TACE. The TRIP-MRI technique has previously been performed with 2D acquisitions in a combined clinical magnetic resonance/DSA unit (termed MR-IR unit) to monitor TACE. In this study, using a clinical MR-IR unit, we tested the hypothesis that 4D TRIP-MRI can be used to measure intra-procedural perfusion changes in liver tumors during TACE.

11:24 62.  Initial Clinical Experience with a Robotic Assistance System for Liver Biopsies in a Diagnostic 1.5T MR Scanner
    Michael Moche1, Dirk Zajonz1, Thomas Kahn1, Harald Busse1
Dept. of Diagnostic and Interventional Radiology, Leipzig University Hospital, Leipzig, Germany

We report on our initial experience from 12 liver biopsies guided by a commercial stereotactic robotic system with six degrees of freedom in a closed-bore MRI scanner. Because the liver is subject to respiratory motion, (i) a preinterventional breathhold training with the patient was considered essential, and (ii) immediately after needle placement, the guiding sleeve had to be disconnected from the system to avoid liver injury. The device appears to provide a substantial benefit for biopsies with double oblique access paths. Most of the interventions could be performed without contrast media and the learning curve suggests a mean intervention time of less than one hour.

11:36 63. MRI-Compatible Haptics: Strain Sensing for Real-Time Estimation of Three Dimensional Needle Deflection in MRI Environments
    Yong-Lae Park1, Santhi Elayaperumal1, Seok Chang Ryu1, Bruce Daniel2, Richard J. Black3, Behzad Moslehi3, Mark R. Cutkosky1
1Mechanical Engineering, Stanford University, Stanford, CA, USA; 2Radiology, Stanford University, Stanford, CA, USA; 3Intelligent Fiber Optic Systems Corporation, Santa Clara, CA, USA

There is a need for methods to accurately manipulate instruments within closed MRI systems. During such procedures, it is useful to track deviations from the planned trajectory to minimize positioning error. This research focuses on using MRI-compatible sensors to measure strain on a standard biopsy needle. The sensors used are based on fiber Bragg grating (FBG) technology. FBG sensors produce wavelength shifts under various loads. Our results show that the FBG sensors do not produce image artifacts, and the sensor signals are not affected by the magnetic field.

11:48  64. Passive Navigation Concept for MR-Assisted Orthopedic Interventions - Evaluation in Retrograde Drilling of Osteochondrosis Dissecans (OD) of the Talus
    Christian Jürgen Seebauer1, Ulf Teichgräber2, Florian Wichlas1, Tobias Jung1, Jens Rump2, René Schilling2, Thula Walther2, Hermann Josef Bail1
Center for Musculoskeletal Surgery, Charité Universitätsmedizin Berlin, Berlin, Germany; 2Department of Radiology, Charité Universitätsmedizin Berlin, Berlin, Germany

Drilling under conventional X-ray guidance often leads to damage of the bone and cartilage, due to poor visualization and the complex anatomy of the ankle. We propose a passive, simple and inexpensive navigation concept, based on the cross-sectional nature of MRI for retrograde drilling of osteochondral lesions of the talus under MRI-guidance. For navigation, we used a custom-made MR-compatible drilling device. The passive navigation concept was fast and safe in practice. Saw cut specimens showed that the artificial lesion was hit in all cases. We conclude that our method is a viable alternative to conventional navigation concepts.

12:00 65.  Real-Time Intravascular MRI Endoscopy at 3T

Shashank Sathyanarayana1, Michael Schär2,3, Meiyappan Solaiyappan2, Paul Arthur Bottomley1,2
Electrical and Computer Engineering, Johns Hopkins University, Baltimore, MD, USA; 2Radiology, Johns Hopkins University, Baltimore, MD, USA; 3Philips Healthcare, Cleveland, OH, USA


RF transmission and reception by modified miniature internal probes can intrinsically localize MRI signals to a sensitive “plane” locked to the probe-head, analogous to an endoscope. Here, intra-vascular “MRI endoscopy” is implemented in real-time at 3T in diseased human vessels in-vitro, and in a rabbit model of atherosclerosis in-vivo. Imaging at up to 4 frames-per-second can identify suspect lesions, with high-resolution (≥80µm) follow-up. Cine images from the rabbit aorta are rendered in 3D to visualize the advancing probe from its own perspective. MRI endoscopy offers the potential for fast high-resolution intravascular imaging of vascular pathology and morphology.

12:12 66. An Active Two Channel Guidewire for Interventional Cardiovascular MRI
    Ozgur Kocaturk1, Christina E. Saikus2, Anthony Z. Faranesh2, Michael A. Guttman2, Kanishka Ratnayaka2, Robert J. Lederman2
Translational Medicine Branch, Division of Intramural Research, National Heart Lung Blood Institute, National Institutes of Health , Bethesda, MD, USA; 2Translational Medicine Branch, Division of Intramural Research, National Heart Lung Blood Institute, National Institutes of Health, Bethesda, MD, USA

The success and safety of interventional magnetic resonance imaging (iMRI) procedures require conspicuous intravascular instruments that can be distinguished from surrounding tissues. We have developed an active two channel guidewire that incorporates individual channels to provide superior distal tip and whole shaft visibility simultaneously under real time iMRI. The guidewire visibility and handling were evaluated during in vitro phantom imaging and in vivo real-time MRI-guided vascular access experiments in swine. Also mechanical properties (torquability, tip flexibility, pushability) of the guidewire prototype were compared in several bench-top evaluations with representative 0.035” commercially-available guidewires.

12:24 67.   Active Catheter Tracking in Air Cavities Using a Semisolid Signal Source
    Stefan Alt1, Reiner Umathum1, Wolfhard Semmler1, Michael Bock1
Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany

An active tracking catheter using a semisolid rubber as signal source was constructed to be used for MRI-guided interventions in air-filled cavities of the body. Exploiting the short relaxation time of the material and providing suppression of interfering signals, a special tracking sequence and algorithm is shown. Results from phantom and animal experiments with a tracking catheter prototype are presented.

12:36 68.

A View-Sharing Compressed Sensing Technique for 3D Catheter Visualization from Bi-Planar Views

    Carsten Oliver Schirra1, Steffen Weiss2, Sascha Krueger2, Reza Razavi1, Sebastian Kozerke1,3, Tobias Schaeffter1
Division of Imaging Sciences, King's College London, London, UK; 2Philips Research Europe, Hamburg, Germany; 3Institute for Biomedical Engineering, Univeristy and ETH Zurich, Zurich, Switzerland

Fast visualization of catheters is indispensable for MR-guided interventions. We propose a new method based on bi-planar imaging using two perpendicular 2D projection views. The two projection views are acquired rapidly by using a randomized view-sharing 1D phase encoding scheme allowing for accelerated recovery of the catheter shape using Compressed Sensing as well as measurement of organ motion. Furthermore, a new catheter design is proposed that allows for better shape recovery and robust tip tracking. The method was assessed on a simulation and its feasibility tested in an in-vivo.

12:48 69.  Outer Volume Suppression for Three Different Steady State Sequences Used in Percutaneous Interventions
    Jaane Rauschenberg1, Patrik Zamecnik2, Wolfhard Semmler1, Michael Bock1
Medical Physics in Radiology, German Cancer Research Center, Heidelberg, Germany; 2Division of Radiology, German Cancer Research Center, Heidelberg, Germany

Outer volume suppression (OVS) is performed in steady state sequences to restrict the field of view and thus, to accelerate the image acquisition. Without destroying the steady state, OVS is integrated in three different pulse sequences (FLASH, PSIF, trueFISP) which provide T1, T2-like and T2/T1 image contrast. With a 12.5% FOV restriction an update rate of 5 images/s could be achieved.