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Title: Quantitative prediction of radio frequency induced local heating derived from measured magnetic field maps in magnetic resonance imaging: A phantom validation at 7 T

Electrical Properties Tomography (EPT) technique utilizes measurable radio frequency (RF) coil induced magnetic fields (B1 fields) in a Magnetic Resonance Imaging (MRI) system to quantitatively reconstruct the local electrical properties (EP) of biological tissues. Information derived from the same data set, e.g., complex numbers of B1 distribution towards electric field calculation, can be used to estimate, on a subject-specific basis, local Specific Absorption Rate (SAR). SAR plays a significant role in RF pulse design for high-field MRI applications, where maximum local tissue heating remains one of the most constraining limits. The purpose of the present work is to investigate the feasibility of such B1-based local SAR estimation, expanding on previously proposed EPT approaches. To this end, B1 calibration was obtained in a gelatin phantom at 7 T with a multi-channel transmit coil, under a particular multi-channel B1-shim setting (B1-shim I). Using this unique set of B1 calibration, local SAR distribution was subsequently predicted for B1-shim I, as well as for another B1-shim setting (B1-shim II), considering a specific set of parameter for a heating MRI protocol consisting of RF pulses plaid at 1% duty cycle. Local SAR results, which could not be directly measured with MRI, were subsequently converted into temperaturemore » change which in turn were validated against temperature changes measured by MRI Thermometry based on the proton chemical shift.« less
Authors:
;  [1] ; ;  [2] ;  [1] ;  [3]
  1. Department of Biomedical Engineering, University of Minnesota, Minneapolis, Minnesota 55455 (United States)
  2. Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, Minnesota 55455 (United States)
  3. (United States)
Publication Date:
OSTI Identifier:
22395568
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 105; Journal Issue: 24; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ABSORPTION; ANIMAL TISSUES; CALIBRATION; CHEMICAL SHIFT; ELECTRIC FIELDS; ELECTRICAL PROPERTIES; GELATIN; HEATING; MAGNETIC FIELDS; NMR IMAGING; PHANTOMS; PROTONS; RADIOWAVE RADIATION; TOMOGRAPHY; VALIDATION