Interventional MRI: Thermotherapy
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Thursday 10 May 2012
Room 212-213  10:30 - 12:30 Moderators: Rares V. Salomir, L. Wilbert Bartels

10:30 0554.   Percutaneous Selective Laser Hippocampectomy for Treatment of Mesial Temporal Lobe Epilepsy within an Interventional MRI Suite
Robert E. Gross1,2, Amit Saindane2,3, Hiroumi D. Kitajima2,3, Bobbie Burrow2,4, Ashok Gowda5, and Sherif G. Nour2,3
1Neurosurgery, Emory University School of Medicine, Atlanta, GA, United States, 2Emory Interventional MRI Program, Emory University Hospital, Atlanta, GA, United States, 3Radiology and Imaging Sciences, Emory University School of Medicine, Atlanta, GA, United States, 4Radiology and Imaging Sciences, Emory University Hospital, Atlanta, GA, United States, 5Visualase, Inc., Houston, TX, United States

Patients with refractory mesial temporal lobe epilepsy are candidates for surgical mesial temporal lobe resection. There is a growing trend toward more selective resections of the amygdala/hippocampus to improve cognitive outcomes. However, "selective” amygdalo-hippocampectomy may still be complicated by collateral damage en-route to mesial temporal lobe structures. This report introduces a minimally invasive alternative via percutaneous selective laser hippocampectomy where laser fiber insertion in the hippocampus is confirmed/adjusted under MRI and followed by temperature-controlled targeted energy deposition under real-time MRI monitoring within a dedicated “interventional MRI” suite. Technical aspects, feasibility, safety, and MRI appearance of resultant ablation zones are described.

10:42 0555.   
In vivo study of the dynamics of Blood Brain Barrier opening and closure after ultrasonic disruption. A quantitative analysis
Benjamin Marty1, Benoit Larrat2, Mathieu Pernot2, Philippe Robert3, Marc Port3, Caroline Robic3, Denis Le Bihan1, Franck Lethimonnier1, Mickael Tanter2, and Sébastien Mériaux1
1CEA/DSV/I2BM/NeuroSpin, Gif sur Yvette, France, 2Institut Langevin/ESPCI ParisTech/INSERM U979, Paris, France, 3Research Division, Guerbet, Aulnay sous Bois, France

Lately, many studies have shown the ability to disrupt locally and transiently the Blood Brain Barrier with low power ultrasound sonication of intravascular microbubbles. Here, we used contrast agents of different diameters to estimate the maximum molecule size able to penetrate cerebral tissues and T1 mapping to quantitatively study and model the closure mechanism of BBB after opening. From experimental data and BBB closure modeling, we obtained a calibration curve predicting half closure time as a function of contrast agent size. Those findings are valuable information to control precisely the amount of drug delivered across the BBB after systemic injection.

10:54 0556.   Initial in vivo evaluation of a breast-specific MRgHIFU system
Allison Payne1, Robb Merrill1, Emilee Minalga1, Nick Todd1, Joshua de Bever2, Erik Dumont3, Leigh Neumayer4, Douglas Christensen5,6, Robert Roemer7, and Dennis Parker1
1UCAIR, Department of Radiology, University of Utah, Salt Lake City, UT, United States, 2Department of Computer Science, University of Utah, Salt Lake City, UT, United States, 3Image Guided Therapy, Bordeax, France, 4Department of Surgery, University of Utah, Salt Lake City, UT, United States,5Department of Electrical and Computer Engineering, University of Utah, Salt Lake City, UT, United States, 6Department of Bioengineering, University of Utah, Salt Lake City, UT, United States, 7Department of Mechanical Engineering, University of Utah, Salt Lake City, UT, United States

In vivo results show the potential of a new breast-specific magnetic resonance guided high intensity focused ultrasound system to treat and manage breast cancer. The system comprised of a laterally-shooting phased array transducer with an integrated 11-channel RF-coil system was evaluated in an in vivo rabbit model. The presented results show the volumetric thermal dose accumulated in the ablated tissue with accompanying post-treatment T2w images and gross histology results.

11:06 0557.   
Shear Wave Tracking in Cadaveric Breast Using MR-ARFI
R R Bitton1, E Kaye2, and K Butts Pauly1
1Radiology, Stanford University, Stanford, CA, United States, 2Electrical Engineering, Stanford University, Stanford, CA, United States

This study presents an MR-ARFI method that uses two ultrasonic excitations to track the extent of a shear wave, and calculate tissue velocities along radial trajectories in cadaveric breast tissue. The technique was validated using a uniform ARFI phantom and then applied to a cadaveric breast specimen with an ablated subregion. The time-of-flight method was used to calculate the breast tissue velocity along radial trajectories of the displacement map. Breast tissue shear wave velocity ranged from (0.4 – 6.3) m/s. This technique may be a useful tool in mapping the stiffness of regions within heterogeneous tissue, particularly in MRgHIFU applications.

11:18 0558.   Clinical demonstration of transient cavitation induced errors on PRFS MR thermometry during RF ablation in liver, using simultaneous US/MR imaging
Lorena Petrusca1, Sylvain Terraz1, Magalie Viallon1, Vincent Auboiroux1, Li Pan2, Shelby Brunke3, Christoph Becker1, and Rares Salomir1
1Radiology Department, Geneva University Hospital, Geneva, Switzerland, 2Center for Applied Medical Imaging, Siemens Corporate Research, Baltimore, United States, 3US Division, Siemens Medical Solutions, Issaquah, Washington, United States

A clinical RF ablation study of HCC nodule in liver using simultaneous US and MR dual-monitoring is presented here. The interactive targeting mode enables effective and sufficiently rapid electrode placement in clinical practice. RFA induces dynamic changes in magnetic buck susceptibility, major distortion of PRFS thermometry including butterfly-like and false negative temperature of the MRT maps in the RF electrode vicinity being observed. These errors were correlated with the induced bubbles of thermal cavitation visualized in US imaging.

11:30 0559.   
Tissue Impedance Implications of Performing RF Ablation at 64 MHz
Kim Shultz1, Pascal Stang1, John Pauly1, and Greig Scott1
1Electrical Engineering, Stanford University, Stanford, CA, United States

If RF ablation is performed at 64 MHz instead of 500 kHz, the RF magnetic field generated by the ablation current can be imaged with B1 mapping techniques. Changing the frequency of the ablation changes the impedance response of the tissue to heating, with potential implications for the ablation process. We compared the impedance response of RF ablation at both frequencies, using MRI to obtain temperature and B1 maps of the 64 MHz ablation. The 64 MHz ablation undergoes a more limited impedance roll-off at high temperatures, potentially allowing higher temperatures while still effectively ablating.

11:42 0560.   
Real-Time Method for MR Thermometry and Treatment of Mobile Organs by MRgHIFU
Zarko Celicanin1, Vincent Auboiroux2, Oliver Bieri1, Francesco Santini1, Magalie Viallon2, Klaus Scheffler3,4, and Rares Salomir2
1Division of Radiological Physics, Department of Radiology and Nuclear Medicine, University of Basel Hospital, Basel, Switzerland, 2Radiology Department, University Hospitals of Geneva, Geneva, Switzerland, 3MRC Department, MPI for Biological Cybernetics, Tübingen, Germany, 4Dept. Neuroimaging and MR-Physics, University of Tübingen, Tübingen, Germany

High-intensity focused ultrasound (HIFU) is a promising new technique for noninvasive thermal therapy. Motion is a severe problem that prevents application of MRgHIFU system to the thermal treatment of abdominal region. We try to combine intra- and interscan motion compensation for stabilization of thermometry imaging, and simultaneous real-time MRgHIFU focal point steering. Our approach is different to the previously published method in the way respiratory motion is compensated and real-time HIFU focal point steering achieved. The navigator echo is used for both intra- and interscan motion compensation of thermometry imaging and real-time HIFU focal point adjustment.

11:54 0561.   A clinically applicable approach for higher spatiotemporal resolution thermometry mapping
Feng Huang1, Max Köhler2, Jukka Tanttu2, Roel Deckers3, Wei Lin1, and George Randy Duensing1
1Invivo Corporation, Gainesville, FL, United States, 2Philips Healthcare, Vantaa, Finland, 3University Medical Center Utrecht, Image Sciences Institute, Utrecht, Netherlands

In recent years magnetic resonance thermometry has been coupled with various means of heating or cooling tissue for therapy. Measuring the effect of the tissue heating or cooling allows the guiding of the therapy and also the ability to assess the effect of a therapeutic treatment on a subject. To achieve sufficient temporal and spatial resolution in proton resonance frequency based thermometry, fast phase imaging is required preferably with a high spatial resolution while maintaining a sufficient SNR for reconstruction of reliable temperature measurements. In this work, a variable density acquisition scheme and spatially adaptive convolution in k/k-t space reconstruction scheme are proposed for this purpose. Preliminary results show that the temperature error of the proposed method is -0.3±0.8 °C at net reduction factor 4.

12:06 0562.   MRI-Guided Cryoablation of Small Renal Tumors
R Jason Stafford1, Sanaz Javadi2, Elizabeth P Ninan2, Yvette Teniente2, Li Pan3, Surena Matin4, and Kamran Ahrar2
1Imaging Physics, The University of Texas MD Anderson Cancer Center, Houston, TX, United States, 2Interventional Radiology, The University of Texas MD Anderson Cancer Center, 3Center for Applied Medical Imaging, Siemens Corporate Research, Baltimore, MD, 4Urology, The University of Texas MD Anderson Cancer Center

Initial experience in clinical implementation of MRI guided cryotherapy on a 1.5T compact and wide bore system is presented. MRI is used for planning, targeting, monitoring and verification of delivery with long term patient follow-up in more than 15 patients. Initial results are summarized for treated patients as well as a description of the procedures and techniques used. We find that MRI guidance appears to provide similar outcomes as those observed in CT, but without additional radiation and a better ability to visualize the iceball in complex tissue environments during therapy delivery.

12:18 0563.   
MR-guided focal cryoablation of prostate cancer recurrence following external beam radiation therapy: safety and feasilbility
Joyce G.R. Bomers1, Derya Yakar1, Kristian Overduin1, Frank de Lange1, J.P. Michiel Sedelaar2, Henk Vergunst3, Jelle O. Barentsz1, and Jurgen J. Fütterer1
1Radiology, Radboud University Nijmegen Medical Centre, Nijmegen, Netherlands, 2Urology, Radboud University Nijmegen Medical Centre, Nijmegen, Netherlands, 3Urology, Canisius Wilhelmina Ziekenhuis, Nijmegen, Netherlands

Six patients with recurrent PCa were successfully treated with transperineal MR-guided focal cryoablation in a closed-bore 1.5 tesla MR scanner. In all patients a hyper intense ice ball rim was clearly visible on T1-weighted images and iceball growth and thus critical temperature zone were carefully monitored. No major complications were recorded. After 3 months PSA level decreased and follow-up MRI showed no cancer. Initial results are promising and more patients have to be included.