Open AccessEffect of RF pulse sequence on temperature elevation for a given time‐average SAR
Author(s) -
Wang Zhangwei,
Collins Christopher M.
Publication year - 2010
Publication title -
concepts in magnetic resonance part b: magnetic resonance engineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.286
H-Index - 32
eISSN - 1552-504X
pISSN - 1552-5031
DOI - 10.1002/cmr.b.20172
Subject(s) - specific absorption rate , pulse (music) , sequence (biology) , pulse sequence , transient (computer programming) , physics , energy (signal processing) , computational physics , volume (thermodynamics) , nuclear magnetic resonance , materials science , optics , mathematics , chemistry , computer science , telecommunications , biochemistry , quantum mechanics , detector , antenna (radio) , operating system
In calculations of temperature increase during MRI, it is typically assumed adequate to consider the specific energy absorption rate (SAR) levels averaged over an entire repetition time (TR) rather than explicitly consider the heating (as it occurs in reality) during the RF pulses only. Here, we investigate this assumption with numerical calculations of SAR and temperature increase for a human head in a volume coil at 64 and 300 MHz during three very different pulse sequences, each having a TR of 200 ms and a time‐average whole‐head SAR of 3.0 W/kg, as well as with semianalytical calculations considering a gradient‐echo sequence in a segment of tissue with SAR of 10 W/kg delivered in a 1‐ms pulse with TR of up to 5,000 ms. Although it is possible to calculate a temporal effect of specific pulse sequence on temperature, the difference between pulse sequences is so small and so transient that it should typically be adequate to consider only the time‐average SAR in each TR. © 2010 Wiley Periodicals, Inc. Concepts Magn Reson Part B (Magn Reson Engineering) 37B: 215–219, 2010.