William A Grissom1,2, Steven Allen3. 1. Vanderbilt University Institute of Imaging Science, Nashville, Tennessee. 2. Department of Biomedical Engineering, Vanderbilt University, Nashville, Tennessee. 3. Department of Biomedical Engineering, University of Virginia, Charlottesville, Virginia.
Abstract
PURPOSE: To reduce temperature errors due to water motion in transcranial MR-guided focused ultrasound (tcMRgFUS) ablation. THEORY AND METHODS: In tcMRgFUS, water is circulated in the transducer bowl around the patient's head for acoustic coupling and heat removal. The water moves during sonications that are monitored by MR thermometry, which causes it to alias into the brain and create temperature errors. To reduce these errors, a two-dimensional excitation pulse was implemented in a gradient-recalled echo thermometry sequence. The pulse suppresses water signal by selectively exciting the brain only, which reduces the imaging FOV. Improvements in temperature precision compared to the conventional full-FOV scan were evaluated in healthy subject scans outside the tcMRgFUS system, gel phantom scans in the system with heating, and in 2×-accelerated head phantom scans in the system without heating. RESULTS: In vivo temperature precision (standard deviation of temperature errors) outside the tcMRgFUS system was improved 43% on average, due to the longer TR and TE of the reduced-FOV sequence. In the phantom heating experiments, the hot spot was less distorted in the reduced-FOV scans, and background temperature precision was improved 59% on average. In the accelerated head phantom temperature reconstructions, temperature precision was improved 89% using the reduced-FOV sequence. CONCLUSIONS: Reduced-FOV temperature imaging alleviates temperature errors due to water bath motion in tcMRgFUS, and enables accelerated temperature mapping with greater precision.
PURPOSE: To reduce temperature errors due to water motion in transcranial MR-guided focused ultrasound (tcMRgFUS) ablation. THEORY AND METHODS: In tcMRgFUS, water is circulated in the transducer bowl around the patient's head for acoustic coupling and heat removal. The water moves during sonications that are monitored by MR thermometry, which causes it to alias into the brain and create temperature errors. To reduce these errors, a two-dimensional excitation pulse was implemented in a gradient-recalled echo thermometry sequence. The pulse suppresses water signal by selectively exciting the brain only, which reduces the imaging FOV. Improvements in temperature precision compared to the conventional full-FOV scan were evaluated in healthy subject scans outside the tcMRgFUS system, gel phantom scans in the system with heating, and in 2×-accelerated head phantom scans in the system without heating. RESULTS: In vivo temperature precision (standard deviation of temperature errors) outside the tcMRgFUS system was improved 43% on average, due to the longer TR and TE of the reduced-FOV sequence. In the phantom heating experiments, the hot spot was less distorted in the reduced-FOV scans, and background temperature precision was improved 59% on average. In the accelerated head phantom temperature reconstructions, temperature precision was improved 89% using the reduced-FOV sequence. CONCLUSIONS: Reduced-FOV temperature imaging alleviates temperature errors due to water bath motion in tcMRgFUS, and enables accelerated temperature mapping with greater precision.
Authors: Anke Henning; Michael Schär; Rolf F Schulte; Bertram Wilm; Klaas P Pruessmann; Peter Boesiger Journal: Magn Reson Med Date: 2008-01 Impact factor: 4.668
Authors: Emine Ulku Saritas; Charles H Cunningham; Jin Hyung Lee; Eric T Han; Dwight G Nishimura Journal: Magn Reson Med Date: 2008-08 Impact factor: 4.668
Authors: Pejman Ghanouni; Kim Butts Pauly; W Jeff Elias; Jaimie Henderson; Jason Sheehan; Stephen Monteith; Max Wintermark Journal: AJR Am J Roentgenol Date: 2015-07 Impact factor: 3.959
Authors: Steven P Allen; Francesco Prada; Zhiyuan Xu; Jeremy Gatesman; Xue Feng; Helen Sporkin; Yekaterina Gilbo; Sydney DeCleene; Kim Butts Pauly; Craig H Meyer Journal: Magn Reson Med Date: 2020-11-11 Impact factor: 3.737