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Tissue specific considerations in implementing high intensity focussed ultrasound under magnetic resonance imaging guidance

High-intensity focused ultrasound can ablate a target permanently, leaving tissues through which it passes thermally unaffected. When delivered under magnetic resonance (MR) imaging guidance, the change in tissue relaxivity on heating is used to monitor the temperatures achieved. Different tissue ty...

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Autores principales: deSouza, Nandita M., Gedroyc, Wladyslaw, Rivens, Ian, ter Haar, Gail
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Frontiers Media S.A. 2022
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9663991/
https://www.ncbi.nlm.nih.gov/pubmed/36387108
http://dx.doi.org/10.3389/fonc.2022.1037959
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author deSouza, Nandita M.
Gedroyc, Wladyslaw
Rivens, Ian
ter Haar, Gail
author_facet deSouza, Nandita M.
Gedroyc, Wladyslaw
Rivens, Ian
ter Haar, Gail
author_sort deSouza, Nandita M.
collection PubMed
description High-intensity focused ultrasound can ablate a target permanently, leaving tissues through which it passes thermally unaffected. When delivered under magnetic resonance (MR) imaging guidance, the change in tissue relaxivity on heating is used to monitor the temperatures achieved. Different tissue types in the pre-focal beam path result in energy loss defined by their individual attenuation coefficients. Furthermore, at interfaces with different acoustic impedances the beam will be both reflected and refracted, changing the position of the focus. For complex interfaces this effect is exacerbated. Moreover, blood vessels proximal to the focal region can dissipate heat, altering the expected region of damage. In the target volume, the temperature distribution depends on the thermal conductivity (or diffusivity) of the tissue and its heat capacity. These are different for vascular tissues, water and fat containing tissues and bone. Therefore, documenting the characteristics of the pre-focal and target tissues is critical for effective delivery of HIFU. MR imaging provides excellent anatomic detail and characterization of soft tissue components. It is an ideal modality for real-time planning and monitoring of HIFU ablation, and provides non-invasive temperature maps. Clinical applications involve soft-tissue (abdomino-pelvic applications) or bone (brain applications) pre-focally and at the target (soft-tissue tumors and bone metastases respectively). This article addresses the technical difficulties of delivering HIFU effectively when vascular tissues, densely cellular tissues, fat or bone are traversed pre-focally, and the clinical applications that target these tissues. The strengths and limitations of MR techniques used for monitoring ablation in these tissues are also discussed.
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spelling pubmed-96639912022-11-15 Tissue specific considerations in implementing high intensity focussed ultrasound under magnetic resonance imaging guidance deSouza, Nandita M. Gedroyc, Wladyslaw Rivens, Ian ter Haar, Gail Front Oncol Oncology High-intensity focused ultrasound can ablate a target permanently, leaving tissues through which it passes thermally unaffected. When delivered under magnetic resonance (MR) imaging guidance, the change in tissue relaxivity on heating is used to monitor the temperatures achieved. Different tissue types in the pre-focal beam path result in energy loss defined by their individual attenuation coefficients. Furthermore, at interfaces with different acoustic impedances the beam will be both reflected and refracted, changing the position of the focus. For complex interfaces this effect is exacerbated. Moreover, blood vessels proximal to the focal region can dissipate heat, altering the expected region of damage. In the target volume, the temperature distribution depends on the thermal conductivity (or diffusivity) of the tissue and its heat capacity. These are different for vascular tissues, water and fat containing tissues and bone. Therefore, documenting the characteristics of the pre-focal and target tissues is critical for effective delivery of HIFU. MR imaging provides excellent anatomic detail and characterization of soft tissue components. It is an ideal modality for real-time planning and monitoring of HIFU ablation, and provides non-invasive temperature maps. Clinical applications involve soft-tissue (abdomino-pelvic applications) or bone (brain applications) pre-focally and at the target (soft-tissue tumors and bone metastases respectively). This article addresses the technical difficulties of delivering HIFU effectively when vascular tissues, densely cellular tissues, fat or bone are traversed pre-focally, and the clinical applications that target these tissues. The strengths and limitations of MR techniques used for monitoring ablation in these tissues are also discussed. Frontiers Media S.A. 2022-11-01 /pmc/articles/PMC9663991/ /pubmed/36387108 http://dx.doi.org/10.3389/fonc.2022.1037959 Text en Copyright © 2022 deSouza, Gedroyc, Rivens and ter Haar https://creativecommons.org/licenses/by/4.0/This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
spellingShingle Oncology
deSouza, Nandita M.
Gedroyc, Wladyslaw
Rivens, Ian
ter Haar, Gail
Tissue specific considerations in implementing high intensity focussed ultrasound under magnetic resonance imaging guidance
title Tissue specific considerations in implementing high intensity focussed ultrasound under magnetic resonance imaging guidance
title_full Tissue specific considerations in implementing high intensity focussed ultrasound under magnetic resonance imaging guidance
title_fullStr Tissue specific considerations in implementing high intensity focussed ultrasound under magnetic resonance imaging guidance
title_full_unstemmed Tissue specific considerations in implementing high intensity focussed ultrasound under magnetic resonance imaging guidance
title_short Tissue specific considerations in implementing high intensity focussed ultrasound under magnetic resonance imaging guidance
title_sort tissue specific considerations in implementing high intensity focussed ultrasound under magnetic resonance imaging guidance
topic Oncology
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9663991/
https://www.ncbi.nlm.nih.gov/pubmed/36387108
http://dx.doi.org/10.3389/fonc.2022.1037959
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