Thermotherapy & Thermometry

Tuesday 23 April 2013

Yuexi Huang¹, Nir Lipsman², Michael L. Schwartz³, Andres M. Lozano², and Kullervo Hynynen^1
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.

Bio Joo¹, Mi-Suk Park¹, Soo Hyun Lee¹, Hye Jin Choi¹, Young Tag Oh¹, Itay Rachmilevitch², and Ori Atar^2
1Yonsei University Medical School, Seoul, Seoul, Korea, ²Insightec, Israel, Israel, Israel

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

Natalya Rapoport¹, Allison H. Payne², Christopher Dillon¹, and Jill E. Shea^3
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.

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 Pauly^5
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.

Daniel Coman¹, Yuegao Huang¹, John W. Simmons², James A. Goodrich³, Brain McHugh⁴, John A. Elefteriades⁵, Douglas L. Rothman^1,6, and Fahmeed Hyder^1,6
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.

Changjun Tie¹, Chao Zou¹, Mengyue He¹, Wensha Guo¹, Yiu-Cho Chung¹, and Xin Liu^1
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.

Paul Baron¹, Mario Ries¹, Martijn de Greef¹, Roel Deckers¹, Max Köhler², Jukka Tanttu², Chrit T.W. Moonen¹, and Lambertus W. Bartels^1
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.

Narae Choi¹, Joonsung Lee¹, Min-Oh Kim¹, Jaewook Shin¹, and Dong-Hyun Kim^1
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.

Elena Kaye¹, Yoni Herzberg², Gil Navon³, and Kim R. Butts Pauly^1
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.

Zarko Celicanin¹, Vincent Auboiraux², Oliver Bieri¹, Lorena Petrusca², Yutaka Natsuaki³, Francesco Santini¹, Magalie Viallon², Klaus Scheffler^4,5, and Rares Salomir^2
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.