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

Thermotherapy & Thermometry
Tuesday 23 April 2013
Room 255 EF  10:00 - 12:00 Moderators: L. Wilbert Bartels, Nicholas Todd

10:00 0224.   MR-Guided Focused Ultrasound for the Treatment of Essential Tremor: Initial Experience on MR-Based Targeting and Temperature Monitoring
Yuexi Huang1, Nir Lipsman2, Michael L. Schwartz3, Andres M. Lozano2, and Kullervo Hynynen1
1Sunnybrook Research Institute, Toronto, ON, Canada, 2Division of Neurosurgery, Toronto Western Hospital, Toronto, ON, Canada, 3Division of Neurosurgery, Sunnybrook Health Sciences Centre, Toronto, ON, Canada

Four essential tremor patients have been treated by a MR-guided focused ultrasound brain system (ExAblate 4000) in a phase 1 clinical trial. Treatment target was the ventralis intermediate nucleus (VIM) of the thalamus. Targeting was based on distance measurement from reference structures on a T2 image crossing through the anterior and posterior commissures. Minor adjustments (1mm) were made if patient had sensory response at low power levels. It is crucial to perform temperature mapping on all three orthogonal planes with repeated sonications to detect any irregular shape of the actual focal heating volume. Retrospectively, fractional anisotropy images generated image contrast within the thalamus next to the VIM target, which may be useful for patient specific targeting.

10:12 0225.   Pain Palliation in Patients with Bone Metastasis Using MR-Guided Focused Ultrasound with Conformal Bone System: A Preliminary Report
Bio Joo1, Mi-Suk Park1, Soo Hyun Lee1, Hye Jin Choi1, Young Tag Oh1, Itay Rachmilevitch2, and Ori Atar2
1Yonsei University Medical School, Seoul, Seoul, Korea, 2Insightec, Israel, Israel, Israel

MRgFUS with CBS is effective for pain palliation in patients with bone metastasis.

10:24 0226.   MRI-Guided Focused Ultrasound-Mediated Drug Delivery to Pancreatic Cancer: Safety and Efficacy
Natalya Rapoport1, Allison H. Payne2, Christopher Dillon1, and Jill E. Shea3
1Bioengineering, University of Utah, Salt Lake City, Utah, United States, 2Radiology Research, University of Utah, Salt Lake City, Utah, United States, 3Surgery, University of Utah, Salt Lake City, Utah, United States

In a preclinical animal model, tumor irradiation with focal ultrasound under the MRI guidance (MRgFUS) was applied for efficient drug delivery to pancreatic cancer using systemically injected perfluorocarbon nanodroplet-encapsulated drug (paclitaxel). MR thermometry was used to control ultrasound treatment. Focal ultrasound irradiation of the tumor triggered droplet-to-bubble transition in perfluorocarbon nanodroplets, which resulted in the local drug release into tumor tissue. Substantial regression and sometimes complete resolution of pancreatic tumors was observed. However sometimes ultrasound treatment-related complications were manifested. Pre-treatment MR images allowed revealing their cause. Efficacy and safety of the suggested treatment modality will be discussed.

10:36 0227.   
Apparent Diffusion Coefficient Decrease During Thermal Ablation of the Prostate as an Early Indicator for Loss of Tissue Viability.
Juan C. Plata1, Andrew B. Holbrook1, Michael Marx1, Vasant Salgaonkar2, Peter Jones2, Chris J. Diederich2, Aurea Pascal-Tenorio3, Donna Bouley3, Graham Sommer4, and Kim R. Butts Pauly5
1Radiology, Stanford, Stanford, CA, United States, 2Radiaiton Oncology, University of California San Francisco, San Francisco, CA, United States, 3Comparative Medicine, Stanford, Stanford, CA, United States, 4Clinical Radiology, Stanford, Stanford, CA, United States, 5Radiology, Stanford University, Stanford, CA, United States

Diffusion weighted MRI (DWI) has demonstrated a 36% reduction in apparent diffusion coefficient (ADC) following HIU induced tissue damage of the prostate. We have previously used interleaved temperature and ADC measurements to extract tissue viability information from ADC measurements that are also dependent on temperature. Our purpose is to demonstrate that the decrease/plateau of ADC during sonication of the prostate was indicative of a transition from viable to non-viable tissue. We monitored treatments on healthy tissue as well as previously damaged tissue to assess whether our proposed marker of tissue viability is reliable and agrees with histology.

10:48 0228.   Selective Brain Cooling in Sheep by Intra-Ventricular Catheters: A 7T BIRDS Study
Daniel Coman1, Yuegao Huang1, John W. Simmons2, James A. Goodrich3, Brain McHugh4, John A. Elefteriades5, Douglas L. Rothman1,6, and Fahmeed Hyder1,6
1Diagnostic Radiology, Yale University, New Haven, CT, United States, 2CoolSpine LLC, Woodbury, CT, United States, 3Comparative Medicine, Yale University, New Haven, CT, United States, 4Neurosurgery, Yale University, New Haven, CT, United States, 5Cardiothoracic Surgery, Yale University, New Haven, CT, United States, 6Biomedical Engineering, Yale University, New Haven, CT, United States

Selective brain cooling to induce hypothermia is a potentially important clinical tool for neuroprotection against cerebral ischemia and mitigates brain injury caused by brain trauma, cardiac arrest or stroke. Towards this goal we developed a ventricular cooling device for selectively inducing brain hypothermia. However, translation to humans requires understanding of local cooling efficiency, which can be obtained by temperature mapping. Biosensor Imaging of Redundant Deviation in Shifts (BIRDS) was used to obtain the time dependence of absolute temperature distribution during cooling. Selective cooling of each hemisphere was achieved within 10 minutes and fast recovery to physiological temperature was also observed.

11:00 0229.   Comprehensive Comparison of Six Referenceless PRF Shift MR Thermometry Methods
Changjun Tie1, Chao Zou1, Mengyue He1, Wensha Guo1, Yiu-Cho Chung1, and Xin Liu1
1Paul C.Lauterbur Research Center for Biomedical Imaging,Shenzhen Key Laboratory for MRI, Shenzhen Institutes of Advanced Technology,Chinese Academy of Sciences, Shenzhen, Guangdong, China

Accuracy of PRF shift based MR thermometry is prone to motion and temporal field change and several referenceless thermometry methods have been proposed to address these issues. However, the accuracies of these methods and their relevance to real time temperature monitoring have not been evaluated. We compared the performance of the six referenceless methods proposed in terms of temperature accuracy and computational requirements. We found that the phase finite difference method and the near harmonic method outperform others in temperature accuracy, and methods that do not require phase unwrapping are generally more computationally efficient.

11:12 0230.   in vivo Validation of T2-Based MR Thermometry in Adipose Tissue Layers for HIFU Near-Field Monitoring
Paul Baron1, Mario Ries1, Martijn de Greef1, Roel Deckers1, Max Köhler2, Jukka Tanttu2, Chrit T.W. Moonen1, and Lambertus W. Bartels1
1Image Sciences Institute, University Medical Center Utrecht, Utrecht, Utrecht, Netherlands, 2Philips Healthcare, Vantaa, Vantaa, Finland

The feasibility of using T2 mapping for monitoring the near field temperature in subcutaneous adipose tissue was investigated during a HIFU liver ablation in an in vivo porcine model. Calibrations showed that T2 changed linearly and reversible with temperature. When compared to the fiber optic probe the accuracy was better than 0.9°C. During the in vivo porcine liver sonication and the subsequent cool-down period T2-thermometry allowed observing the temperature change due to near-field heating in the adipose tissue with a thermometric precision of 1.1°C.

11:24 0231.   
Non-Invasive in vivo Loss Tangent Imaging: Thermal Sensitivity Estimation at the Larmor Frequency
Narae Choi1, Joonsung Lee1, Min-Oh Kim1, Jaewook Shin1, and Dong-Hyun Kim1
1Electrical and Electronic Engineering, Yonsei University, Seodaemun-gu, Seoul, Korea

Medical thermotherapy uses thermal sensitivity difference between tumor and normal tissue. Some factors to determine the thermal sensitivity are the electrical tissue properties. The loss tangent is a parameter of a dielectric material. The loss tangent is a measure of the electromagnetic wave energy transformed to heat energy. It is generally assumed that the thermal sensitivity used in hyperthermia treatment has a positive tendency to the loss tangent hence its knowledge can be beneficial. We propose a nondestructive loss tangent imaging method using MREPT approach, which is a non-invasive estimation method of probing electrical properties.

11:36 0232.   
Towards Improving Predictive Capabilities of MR-ARFI for Transcranial Focused Ultrasound Therapy
Elena Kaye1, Yoni Herzberg2, Gil Navon3, and Kim R. Butts Pauly1
1Radiology, Stanford University, Palo Alto, California, United States, 2School of Physics and Astronomy, Tel Aviv University, Tel Aviv, Israel, 3School of Chemistry, Tel Aviv University, Tel Aviv, Israel

MR-guided acoustic radiation force imaging (MR-ARFI) has been recently proposed to drive adaptive phase-aberration correction for transcranial ultrasound therapy. MR-ARFI detects displacement of tissue caused by acoustic radiation force in the direction of encoding. In a hemispherical transducer, component of the force emitted by the elements along the main axis varies based on geometric position of the element, therefore encoding in this direction is less sensitive to the ultrasound emission and phase aberrations of the peripheral elements. Firstly, we study the effect of numerically applied human skull phase aberrations on the focal spot using MR thermometry that is independent of the direction of acoustic force, and MR-ARFI with encoding along the normal of the hemisphere. Secondly, we demonstrate how the displacement from the individual groups of side elements can be visualized using displacement encoding in oblique direction perpendicular to the face of the elements group.

11:48 0233.   
Hybrid US-MR Guided HIFU Treatment Method with 3D Motion Compensation -permission withheld
Zarko Celicanin1, Vincent Auboiraux2, Oliver Bieri1, Lorena Petrusca2, Yutaka Natsuaki3, Francesco Santini1, Magalie Viallon2, Klaus Scheffler4,5, and Rares Salomir2
1Radiological Physics, University of Basel Hospital, Basel, Switzerland, 2Radiology Department, University Hospitals of Geneva, Geneva, Switzerland, 3Siemens Medical Solutions, Inc., Los Angeles, CA, United States, 4MRC Department, MPI for Biological Cybernetics, Tübingen, Germany, 5Dept. Neuroimaging and MR-Physics, University of Tübingen, Tübingen, Germany

Combining US and MRI into a hybrid system to guide HIFU treatment is a novel approach in the treatment of abdominal organs. Here, it is demonstrated the feasibility of a novel hybrid US-MR guided HIFU with 3D motion compensation and slice tracking of MR thermometry. MR-based navigator was used to compensate the out-of-plane motion, while US imaging system provided 2D organ motion information, which were combined into complete 3D target tracking and fed to HIFU. To the best of the authors knowledge, this is the first truly hybrid US-MR guided HIFU method which achieves full 3D motion compensation.