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Feasibility of MR-guided High Intens...

Looi, Thomas.

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Feasibility of MR-guided High Intensity Focused Ultrasound for Thrombolysis of Brain Intraventricular Hemorrhagic Thrombus.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Feasibility of MR-guided High Intensity Focused Ultrasound for Thrombolysis of Brain Intraventricular Hemorrhagic Thrombus./
Author:	Looi, Thomas.
Published:	Ann Arbor : ProQuest Dissertations & Theses, : 2018,
Description:	142 p.
Notes:	Source: Dissertations Abstracts International, Volume: 80-02, Section: B.
Contained By:	Dissertations Abstracts International80-02B.
Subject:	Biomedical engineering. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=10792200
ISBN:	9780438188457

Feasibility of MR-guided High Intensity Focused Ultrasound for Thrombolysis of Brain Intraventricular Hemorrhagic Thrombus.
Looi, Thomas.

Feasibility of MR-guided High Intensity Focused Ultrasound for Thrombolysis of Brain Intraventricular Hemorrhagic Thrombus. - Ann Arbor : ProQuest Dissertations & Theses, 2018 - 142 p.

Source: Dissertations Abstracts International, Volume: 80-02, Section: B.

Thesis (Ph.D.)--University of Toronto (Canada), 2018.

This item must not be sold to any third party vendors.

Due to pre-mature birth, 10-25% of infants born with low birth weight (<1kg) are susceptible to intraventricular hemorrhage (IVH), where 15% will develop post hemorrhagic hydrocephalus and require cerebrospinal fluid (CSF diversion). No therapy to date to remove or dissolve the blood clot such as with Tissue Plasminogen Activator (TPA) has proven effective largely due to complications. MR-guided focused ultrasound (MRgFUS) is a potential non-invasive therapy as thinner neonatal skulls reduce ultrasonic aberration, which requires simpler transducers and obviates the need for fixation. The hypothesis of this thesis is: MRgFUS can be used to perform thrombolysis in a porcine IVH model where it will decrease the IVH thrombus by at least 50% without injury to the surrounding brain or blood vessels. The spatial pressure distribution of the MRgFUS (Sonalleve, Philips) platform through a neonatal skull was characterized. The ultrasonic focus had a diameter of 1.7 mm and a depth of 9.2 mm and the transmission through the neonatal skull had minimal impact to focus shape and location. A porcine IVH model was created. A semi-autonomous segmentation algorithm calculated an average clot size of 3987 mm3. The chronic porcine model developed progressive hydrocephalus over 21 days with ventricles increased >50% in size. Two thrombolytic histotripsy techniques were tested: short pulse (cavitation cloud) and long pulse (nonlinear effects). In vitro clot testing showed that both techniques were able to dissolve clots. The short pulse had an "all or none" effect not seen with the long pulses. For in vivo treatments, both techniques were successful in dissolving clots with a volume reduction between 9.2% and 36.7%. Based on the ultrasonic pressure requirement for thrombolysis, the long pulse protocol was more suited to the Sonalleve clinical system and is a potential technique to perform MR-guided focused thrombolysis of IVH clots.

ISBN: 9780438188457Subjects--Topical Terms:

535387
Biomedical engineering.

Feasibility of MR-guided High Intensity Focused Ultrasound for Thrombolysis of Brain Intraventricular Hemorrhagic Thrombus.
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500 $a Publisher info.: Dissertation/Thesis.
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502 $a Thesis (Ph.D.)--University of Toronto (Canada), 2018.
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520 $a Due to pre-mature birth, 10-25% of infants born with low birth weight (<1kg) are susceptible to intraventricular hemorrhage (IVH), where 15% will develop post hemorrhagic hydrocephalus and require cerebrospinal fluid (CSF diversion). No therapy to date to remove or dissolve the blood clot such as with Tissue Plasminogen Activator (TPA) has proven effective largely due to complications. MR-guided focused ultrasound (MRgFUS) is a potential non-invasive therapy as thinner neonatal skulls reduce ultrasonic aberration, which requires simpler transducers and obviates the need for fixation. The hypothesis of this thesis is: MRgFUS can be used to perform thrombolysis in a porcine IVH model where it will decrease the IVH thrombus by at least 50% without injury to the surrounding brain or blood vessels. The spatial pressure distribution of the MRgFUS (Sonalleve, Philips) platform through a neonatal skull was characterized. The ultrasonic focus had a diameter of 1.7 mm and a depth of 9.2 mm and the transmission through the neonatal skull had minimal impact to focus shape and location. A porcine IVH model was created. A semi-autonomous segmentation algorithm calculated an average clot size of 3987 mm3. The chronic porcine model developed progressive hydrocephalus over 21 days with ventricles increased >50% in size. Two thrombolytic histotripsy techniques were tested: short pulse (cavitation cloud) and long pulse (nonlinear effects). In vitro clot testing showed that both techniques were able to dissolve clots. The short pulse had an "all or none" effect not seen with the long pulses. For in vivo treatments, both techniques were successful in dissolving clots with a volume reduction between 9.2% and 36.7%. Based on the ultrasonic pressure requirement for thrombolysis, the long pulse protocol was more suited to the Sonalleve clinical system and is a potential technique to perform MR-guided focused thrombolysis of IVH clots.
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