![]() Diffusion-weighted imaging (DWI) is sensitive to water diffusion intracellularly and extracellularly ( 11). Ablated tissue appears hypointense in T1 images due to vascular coagulation but provides no further information about the cellular environment. While changes related to treatment can be discerned, current MR sequences, such as T1-weighted imaging, do little to distinguish detailed microstructural changes in the lesioned areas ( 10). While MRgFUS has been previously used to treat uterine fibroids, bone metastases, prostate cancer, and liver tumors ( 2), recent work has focused on the treatment of essential tremor and tremor associated with Parkinson's disease ( 3– 6), neuropathic pain ( 7), obsessive–compulsive disorder ( 8), and epilepsy ( 9), suggesting that MRgFUS is a promising tool for the treatment of brain disorders. The guidance of MR imaging allows therapeutic targets to be accurately identified and treated ( 2). Magnetic resonance-guided focused ultrasound (MRgFUS) is a novel thermal ablation method that non-invasively destructs tissues by thermal coagulation ( 1). This study demonstrates that DWI has the potential to advance MRgFUS by providing convenient in vivo microstructural lesion and fiber tractography assessment after treatment. Tractography from the lesion core and the fornix revealed fiber disruptions following treatment.Ĭonclusions: Diffusion maps and fiber tractography are an effective method for assessing lesion volumes and microstructural changes in vivo following MRgFUS treatment. Histological analysis confirmed an area of coagulative necrosis in the targeted region with sharp demarcation zone with surrounding brain. Diffusion metrics in the treatment region were significantly decreased following MRgFUS treatment, with the peak change seen at the lesion core and decreasing radially. Results: The volume of treated tissue measured via MDWI did not differ significantly from histological measurements, and both were significantly larger than the treatment cell volume. Fornix-related fiber tracts were generated before and after treatment for qualitative assessment. DWI metric maps of fractional anisotropy (FA), apparent diffusion coefficient (ADC), axial diffusivity (AD), radial diffusivity (RD), and mean diffusivity (MD) were generated for quantitative assessment. Histological data were collected for volume comparison and assessment of treatment effect. Mean diffusion-weighted imaging (MDWI) images were generated to measure lesion volumes via signal intensity thresholds. T1 and diffusion-weighted images were collected before and after treatment. Methods: MRgFUS was used to treat the anterior body of the fornix in four piglets. We investigate in vivo acute changes in water diffusion and white matter tracts in the brain of a piglet model after MRgFUS treatment using diffusion-weighted imaging (DWI) with histological verification of treatment-related changes. Conventional MR imaging can provide structural information about the effect of MRgFUS, where differences in ablated tissue can be seen, but it lacks information about the status of the cellular environment or neural microstructure. Objectives: The application of magnetic resonance-guided focused ultrasound (MRgFUS) for the treatment of neurological conditions has been of increasing interest. 7Division of Neurosurgery, Toronto Western Hospital, University Health Network, Toronto, ON, Canada.6Division of Neurosurgery, Hospital for Sick Children, Toronto, ON, Canada.5Department of Paediatric Laboratory Medicine, Division of Neuropathology, Hospital for Sick Children, Toronto, ON, Canada.4Department of Medical Imaging, University of Toronto, Toronto, ON, Canada.3Centre for Image Guided Innovation and Therapeutic Intervention, Hospital for Sick Children, Toronto, ON, Canada.2Division of Brain, Imaging and Behaviour – Systems Neuroscience, Krembil Research Institute, University Health Network, Toronto, ON, Canada.1Institute of Medical Science, University of Toronto, Toronto, ON, Canada. ![]() Waspe 3,4 Thomas Looi 3 Karolina Piorkowska 3 Cynthia Hawkins 5 James M.
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