ISMRM 24th Annual Meeting & Exhibition 07-13 May 2016 Singapore

Scientific Session: MR-Guided Focused Ultrasound

Thursday Thursday, May 12, 2016
Room 300-302
10:30 - 12:30
Moderators: Eugene Ozhinsky, Bruno Quesson

Multi-echo Pseudo-Golden Angle Stack of Stars Thermometry with High Spatial and Temporal Resolution
Bryant Svedin1 and Dennis L. Parker1
1University of Utah, Salt Lake City, UT, United States
A multi-echo pseudo-golden angle stack of stars sequence is investigated for use in MR thermometry. High spatial and temporal resolution is achieved through k-space filtering. PRF temperature, T2*, ρ (signal magnituade at TE = 0), respiration correction and fat/water separation are simultaneously measured. Use of a pseudo-golden angle increment allows for the removal of phase (and therefore PRF temperature) artifacts due to changing k-space sampling between reconstructed time points. k-Space sampling based phase reference greatly improves temperature standard deviation. FUS heating experiments are performed while simulating respiration artifacts.

Efficient Volumetric Thermometry for MR-Guided FUS Brain Treatment Monitoring, Using Multiple-Echo Spirals and Mixed Update Rates
Michael Marx1, Pejman Ghanouni1, and Kim Butts Pauly1
1Radiology, Stanford University, Stanford, CA, United States
Multi-slice thermometry was developed that overcomes several limitations of single-slice 2DFT thermometry in MR-guided focused ultrasound brain treatment. Using multiple-echo spiral imaging provides much greater imaging performance, which was applied to improved focal spot localization and to improved ablation monitoring. High-resolution higher-precision multi-slice focal spot localization can shorten treatment time and improve patient safety. High-speed high-precision focal spot monitoring, combined with full-brain monitoring and 3-dimensional focal spot characterization during ablations can improve treatment guidance and feedback while also improving patient safety. The new sequences were validated both in vivo and in a phantom within a clinical transducer.

Motion Compensation using Principal Component Analysis and Projection onto Dipole Fields for Abdominal Magnetic Resonance Thermometry during High-Intensity Focused Ultrasound
Jeremy Tan1,2,3, Adam C. Waspe1,2, Charles Mougenot4, Kullervo Hynynen1,5, James M. Drake1,2, and Samuel Pichardo3,6
1University of Toronto, Toronto, ON, Canada, 2Hospital for Sick Children, Toronto, ON, Canada, 3Thunder Bay Regional Research Institute, Thunder Bay, ON, Canada, 4Philips Healthcare, Toronto, ON, Canada,5Sunnybrook Research Institute, Toronto, ON, Canada, 6Electrical Engineering, Lakehead University, Thunder Bay, ON, Canada
Accurate thermometry during abdominal high-intensity focused ultrasound is severely compromised by motion and susceptibility artifacts. A hybrid artifact correction method has been developed using principal component analysis as a multi-baseline method and projection onto dipole fields as a near-referenceless approach. The hybrid algorithm was tested using free-breathing porcine and human subjects and achieved an average temperature stability and precision of 0.31 (0.22) C and 1.18 (0.94) C, respectively in the kidney.

Non-invasive cardiac stimulation with MR guided HIFU: a rapid, cardiac triggered, MR-ARFI method for direct visualization of stimulation site and assessment of tissue stiffness.
Pierre Bour1,2, Fabrice Marquet2, Fanny Vaillant2, Valery Ozenne2, Solenn Toupin2,3, Matthieu Lepetit coiffe3, Erik Dumont1, and Bruno Quesson2
1IGT, PESSAC, France, 2IHU-LIRYC, PESSAC, France, 3Siemens Healthcare, Saint-Denis, France
HIFU cardiac stimulation may enable diagnostic and therapeutic applications such as noninvasive electrophysiological exam, emergency care and temporary stimulation. In-vivo proof of concept of HIFU cardiac stimulation has already been done on pig. We propose here a first proof of feasibility to monitor the displacement induced by acoustic radiation force impulse (MR-ARFI) during contactless stimulation ex-vivo, on a beating pig heart model. ARFI displacement maps will be used for precise localization of the depolarization source and a quantification of displacement will be done during refractory (contraction) and non-refractory (resting time) period. 

Simultaneous Acquisition of Acoustic Radiation Force Imaging and Proton Resonance Frequency Shift Thermometry Using Interleaved Acquisition with Temporally Constrained Reconstruction for Increased Temporal Resolution
Joshua de Bever1,2, Henrik Oden 1,2, and Dennis L. Parker1,2
1Department of Radiology, University of Utah, Salt Lake City, UT, United States, 2Utah Center for Advanced Imaging Research, Salt Lake City, UT, United States
Using focused ultrasound and MR acoustic radiation force imaging (MR-ARFI), the mechanical properties of tissues can be interrogated.  Changes to tissue properties, for instance before and after a MR guided focused ultrasound thermal therapy, could help evaluate treatment success. This abstract presents a novel method for measuring acoustic radiation force simultaneously with proton resonance shift thermometry. This would enhance the safety of MR-ARFI, and provide additional temperature information that may indicate when, and at what temperature, a tissue property change occurred. Temporal resolution was enhanced by a factor of 5 by employing a temporally constrained reconstruction algorithm.

Acceleration of 3D UTE Imaging to Quantify Temperature-Dependent T1 Changes in Cortical Bone
Misung Han1, Wenwen Jiang2, Roland Krug1, Peder Larson1,2, and Viola Rieke1
1Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, CA, United States, 2Joint Graduate Program in Bioengineering, University of California, San Francisco/Berkeley, San Francisco, CA, United States
High-intensity focused ultrasound (HIFU) is a promising, noninvasive technique to ablate bone tumors and palliate painful bone metastases. During HIFU treatment, temperature mapping is desirable for proper heat deposition to targeted bone regions. Even though conventional PRF-based thermometry cannot be applied for cortical bone due to its short T2 relaxation time, it was demonstrated using 3D UTE imaging can be used to measure T1 changes due to heating. In this work, we accelerated 3D UTE imaging by combining parallel imaging and compressed sensing and compared calculated T1 changes due to heating with those from fully sampled data.

Preclinical Study of MRgFUS Ablation of the Lumbar Medial Branch Nerve: Functional Outcomes and Histology
Elena Kaye1, Sebastien Monette2, Majid Maybody3, Stephen B Solomon3, and Amitabh Gulati4
1Medical Physics, Memorial Sloan Kettering Cancer Center, New York, NY, United States, 2Comparative Pathology, Sloan Kettering Institute, New York, NY, United States, 3Radiology, Memorial Sloan Kettering Cancer Center, New York, NY, United States, 4Anesthesiology, Memorial Sloan Kettering Cancer Center, New York, NY, United States
The main goals of this preclinical study were to determine whether direct MRgFUS ablation of the lumbar MB nerve leads to functional changes and to study the extent of the thermal damage to the targeted and adjacent tissues, including neurologic structures. We found that direct FUS ablation of the lumbar MBN achieves thermal necrosis of the targeted nerve with minimal thermal damage of the adjacent bone and muscle tissue. The extent of the cellular changes in bone is limited to a few millimeters with no changes in the spinal cord, confirming the protective effects of spine bone rapidly attenuating the ultrasound. No functional changes were observed.

Diffusion MRI Tractography for Improved MRI-guided Focused Ultrasound Thalamotomy Targeting for Essential Tremor
Qiyuan Tian1,2, Max Wintermark2, Kim Butts Pauly2, Diane Huss3, W. Jeffrey Elias4, and Jennifer A. McNab2
1Electrical Engineering, Stanford University, Stanford, CA, United States, 2Radiology, Stanford University, Stanford, CA, United States, 3Physical Therapy, University of Virginia, Charlottesville, VA, United States,4Neurosurgery, University of Virginia, Charlottesville, VA, United States
We retrospectively studied 13 essential tremor patients treated with MRI-guided focused ultrasound. The purpose was to demonstrate the value of using diffusion MRI tractography to help localize the ventral intermediate (Vim) nucleus of the thalamus (the treatment target). Tractography between the thalamus and hand-knob region of the motor cortex was consistent from subject-to-subject and followed the expected anatomy. The thalamic voxels with high tractography streamline counts qualitatively matched the location of Vim as depicted on the Schaltenbrand-Wahren Atlas. A trend was found towards better treatment outcome scores with higher pre-treatment probabilistic tractography streamline counts within the visualized MRgFUS treatment-induced lesion.

MR-HIFU mild hyperthermia for sensitization of radiation and chemotherapy for recurrent rectal cancer: First phase I clinical trial results.
William Chu1, Robert Staruch2, Samuel Pichardo3,4, Yuexi Huang5, Charles Mougenot6, Matti Tillander7, Max O. Khler7, Mika Ylihautala7, Merrylee McGuffin1, Gregory Czarnota1, and Kullervo Hynynen5
1Radiation Oncology, Sunnybrook Health Science Centre, Toronto, ON, Canada, 2Philips Research, Cambridge, MA, United States, 3Thunder Bay Regional Research Institute, Thunder Bay, ON, Canada, 4Electrical Engineering, Lakehead University, Thunder Bay, ON, Canada, 5Physical Sciences, Sunnybrook Research Institute, Toronto, ON, Canada, 6Philips Healthcare, Toronto, ON, Canada, 7Philips Healthcare, Vantaa, Finland
We present the first results of a Phase I trial that includes delivery of mild hyperthermia using magnetic resonance-guided high intensity focused ultrasound (MR-HIFU) combined with radiation and chemotherapy in the treatment of locally recurrentrectal cancer.  MR-HIFU mild hyperthermia was delivered in three sessions (day 1, 8 and 15) during a 17-day treatment protocol (total dose 30.6 Gy combined with fluropyrimidine-based chemotherapy). MR-HIFU mild hyperthermia was successfully delivered and the procedure was well tolerated by the patient. No adverse effects have been reported 3 months after the treatment.

MRI-guided laser thermal ablation for T1a renal cell carcinoma (RCC): A 4-year experience with longitudinal follow-up of patients
Juan C. Camacho1,2, Nima Kokabi1, Tracy E. Powell2, and Sherif G. Nour1,2
1Radiology and Imaging Sciences, Emory University School of Medicine, Atlanta, GA, United States, 2Interventional MRI Program, Emory University Hospital, Atlanta, GA, United States
The objective of this study is to present outcomes of MRI-guided laser ablation for early stage renal cell carcinomas and to describe associated prognostic factors in a consecutive cohort of patients with relative long-term longitudinal follow-up. A prospective cohort of patients presenting with pathology-confirmed RCC underwent MRI-guided biopsy and subsequent laser ablation. Twenty-four consecutive patients presenting with 35 RCC were recruited. Follow-up MRI imaging was obtained in all cases with a median follow-up period of 20 months. Of the different analyzed prognostic factors, R.E.N.A.L nephrometry score was the only one predicting the incidence of complications.

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