Sherif G Nour^1,2, Tracy E Powell^2,3, and Peter J Rossi^4,5
1Radiology & Imaging Sciences, Emory University, Atlanta, GA, United States, ²Interventional MRI Program, Emory University, GA, United States,³Radiology & Imaging Sciences, Emory University, GA, United States, ⁴Radiation Oncology, Emory University, GA, United States, ⁵School of Medicine, Emory University, GA, United States

We report the technical aspects and outcome results of a minimally-invasive focal treatment using laser ablation under MRI guidance and monitoring to treat localized low-intermediate risk prostate cancer while preserving the rest of the gland. 14 treatment-naïve foci of localized prostate cancer were treated with MRI-guided and monitored focal laser ablation. The technique is feasible and well tolerated as an outpatient procedure. This small series indicates a promising efficacy for up to 24-month recurrence-free follow-up durations. Prospective assessment of safety and efficacy awaits further evaluation on a larger cohort of subjects.

Yi Zhang¹, Dong-Hoon Lee¹, Kai Zhang¹, Antonella Mangraviti², Chen Yang¹, Hye-Young Heo¹, Betty Tyler², Ari Partanen³, Keyvan Farahani^1,4, Paul Bottomley¹, Peter van Zijl^1,5, and Jinyuan Zhou^1,5
1Division of MR Research, Department of Radiolgoy, Johns Hopkins University, Baltimore, Maryland, United States, ²Department of Neurosurgery, Johns Hopkins University, Baltimore, Maryland, United States, ³Clinical Science MR Therapy, Philips Healthcare, Andover, Massachusetts, United States,⁴National Cancer Institue, Bethesda, Maryland, United States, ⁵F. M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland, United States

MRI-guided HIFU is a promising non-invasive therapy for treating tumors. Amide proton transfer-weighted (APTw) imaging is an emerging MRI technique that is sensitive to changes in tissue protein and peptide levels and molecular exchange properties. Here, APTw imaging is used to assess the effects of HIFU treatment effects in a longitudinal rat brain tumor model up to 6 days post-treatment. APTw measurements are compared with conventional MRI indices–relaxation times, diffusion, perfusion and the magnetization transfer ratio. The results suggest that APTw–MRI may detect treatment changes earlier than other MRI metrics.

Yuexi Huang¹, Ryan Alkins¹, Michael L. Schwartz², and Kullervo Hynynen^1,3
1Sunnybrook Research Institute, Toronto, ON, Canada, ²Division of Neurosurgery, Sunnybrook Health Sciences Centre, Toronto, ON, Canada,³Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada

Magnetic resonance-guided focused ultrasound has been demonstrated to reversibly disrupt the blood-brain barrier for targeted drug delivery. Many small and large animal models have been developed to investigate the effectiveness and characteristics of BBB disruptions. However, in translation for a clinical trial, the treatment protocol needs to be optimized according to properties of human skulls and capabilities of the current clinical prototype device. In addition, a cavitation-based safety mechanism needs to be tested in vivo for minimizing risks of hemorrhage. In this study, a BBB disruption protocol was developed in a trans-human skull pig model with human applications in mind. The trans-human skull pig model demonstrated the feasibility and safety of the ExAblate system for BBB disruptions in preparation for human applications.

Bryant T. Svedin^1,2, Allison Payne^1,3, and Dennis L Parker^1,4
1Utah Center for Advanced Imaging Research, Salt Lake City, Utah, United States, ²Physics, University of Utah, Salt Lake City, Utah, United States,³Mechanical Engineering, University of Utah, Salt Lake City, Utah, United States, ⁴Radiology, University of Utah, Salt Lake City, Utah, United States

Respiration induced resonance offsets cause artifacts when imaging the breast. These artifacts lead to erroneous PRF temperature measurements. A phase correction method is applied to k-Space data to correct the respiration induced artifacts and improves accuracy of PRF temperature measurements while allowing free breathing of the patient, and without the need to have a multibaseline library. Two FID within-sequence phase correction navigators are collected and used to estimate the slope of the phase offset (radians/ms) during each TR. The phase of the k-Space lines acquired each TR is adjusted by the slope during that TR times TE.

Jason Su¹, Thomas Tourdias², Manojkumar Saranathan³, Casey Halpern⁴, Kim Butts-Pauly³, Jaimie Henderson⁴, Pejman Ghanouni³, and Brian K. Rutt^3
1Electrical Engineering, Stanford University, Stanford, California, United States, ²Neuroradiology, Bordeaux University Hospital, Bordeaux, France,³Neuroradiology, Stanford University, Stanford, California, United States, ⁴Neurosurgery, Stanford University, Stanford, California, United States

The treatment of 7 essential tremor patients with MR guided focused ultrasound (MRgFUS) ablation of the ventral intermediate nucleus (Vim) in the thalamus was visualized with the white matter nulled MP-RAGE contrast (WMnMPRAGE). Manual segmentation of thalamic nuclei was performed on 7T scans, then registered to post-treatment 3T images. Overlays were produced showing the ablation zone and its position within the nucleus of interest. The ablation zone was revealed to be consistently between the center and inferior edge of Vim, within 1-2mm of the inferior edge. The consistent location demonstrated the functional validity of our thalamic imaging and segmentation methodology.

Joseph Russell Corea¹, Patrick Ye², Anita Flynn¹, Kim Butts-Pauly², Ana Claudia Arias¹, and Michael Lustig^1
1University of California Berkeley, Berkeley, California, United States, ²Radiology, Stanford, Stanford, California, United States

Taking advantage of recent advances in printed electronics, we created a flexible receive coil that is nearly transparent to High Intensity Focused Ultrasound (HIFU) energy. We fabricated the coil from solution using screen-printing, a high volume manufacturing technique. We discuss the performance of the coil and compare the printed components to traditional components with various imaging and acoustic power attenuation testing. We also demonstrate major steps toward clinical usability with the first phantom images - showing promise for use in MR guided HIFU therapy.

Lorena Petrusca¹, Gibran Manasseh², Zarko Celicanin³, Romain Breguet⁴, Oliver Bieri³, Vincent Auboiroux⁵, Christoph D Becker⁴, Sylvain Terraz⁴, and Rares V. Salomir^6
1University of Geneva, Geneva, Geneva, Switzerland, ²Radiology, University Hospitals of Geneva, Geneva, Switzerland, ³University Hospital Basel, Basel, Switzerland, ⁴University Hospitals of Geneva, Geneva, Switzerland, ⁵LETI CEA, Grenoble, France, France, ⁶Radiology, University Hospitals of Geneva, Geneva, Geneva, Switzerland

Treatments using high-intensity focused ultrasound (HIFU) in the abdominal region remain challenging due to respiratory organ motion. Various methods have been attempted in the past to achieve motion-compensated HIFU therapy, using ultrasound (US) imaging, magnetic resonance imaging (MRI), or both simultaneously. Here, a truly hybrid US-MRI guided HIFU (US-MRgHIFU) method was used to plan and control the treatment in vivo. 3D prospective motion correction was implemented at a frame rate of 15Hz on pig liver and kidney. An absolute target was used to demonstrate the spatial accuracy of the method, which was found to be in the sub-millimeter range.

Valéry Ozenne¹, Solenn Toupin^1,2, Baudouin Denis de Senneville³, Pierre Bour¹, Fanny Vaillant¹, Matthieu Lepetit-Coiffé², Pierre Jaïs¹, and Bruno Quesson^1
1L'Institut de Rythmologie et Modélisation Cardiaque, Bordeaux, France, ²SIEMENS Healthcare, Saint Denis, France, ³IMB, UMR 5251 CNRS/University of Bordeaux, Bordeaux, France

Performing magnetic resonance thermometry during cardiac radiofrequency ablation (RFA) requires dealing with motion and susceptibility artifacts due to cardiac and respiratory motion. In this study, the suitability of three in-line thermometry processing methods was evaluated in vivo on the heart of ten healthy volunteers under free breathing conditions. We demonstrated that the temporal temperature standard deviation was minimized with Principal Component Analysis (PCA) based method: 2.2°C instead of 2.7°C with state-of-the-art multi-baseline method. This approach offers robust motion estimation in regions prone to local signal variations on magnitude images during RFA performed on ex-vivo working pig heart.

Megan E Poorman^1,2, Chris J Diederich³, Graham Sommer⁴, Kim Butts Pauly⁴, and William A Grissom^1,2
1Biomedical Engineering, Vanderbilt University, Nashville, TN, United States, ²Institute of Imaging Science, Vanderbilt University, Nashville, TN, United States, ³Radiation Oncology, University of California, San Francisco, CA, United States, ⁴Radiology, Stanford University, Stanford, CA, United States

A model-based technique is proposed for water/fat-separated multi-echo PRF-shift MR thermometry that leverages recent advancements in water/fat separation to achieve high-quality signal separations while maintaining real-time-compatible compute times. The method is validated in simulations and compared to 3-point Dixon-based temperature maps in canine prostate temperature maps during a transurethral focused ultrasound ablation.

Nadège Corbin¹, Jonathan Vappou¹, Elodie Breton¹, Quentin Boehler¹, Laurent Barbé¹, Pierre Renaud¹, and Michel de Mathelin^1
1ICube, Université de Strasbourg, CNRS, IHU Strasbourg, Strasbourg, France