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An internal reference model–based PRF temperature mapping method with Cramer‐Rao lower bound noise performance analysis
Author(s) -
Li Cheng,
Pan Xinyi,
Ying Kui,
Zhang Qiang,
An Jing,
Weng Dehe,
Qin Wen,
Li Kuncheng
Publication year - 2009
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.22121
Subject(s) - cramér–rao bound , noise (video) , signal (programming language) , signal to noise ratio (imaging) , imaging phantom , upper and lower bounds , algorithm , mathematics , nuclear magnetic resonance , physics , estimation theory , computer science , statistics , mathematical analysis , artificial intelligence , optics , image (mathematics) , programming language
Abstract The conventional phase difference method for MR thermometry suffers from disturbances caused by the presence of lipid protons, motion‐induced error, and field drift. A signal model is presented with multi‐echo gradient echo (GRE) sequence using a fat signal as an internal reference to overcome these problems. The internal reference signal model is fit to the water and fat signals by the extended Prony algorithm and the Levenberg‐Marquardt algorithm to estimate the chemical shifts between water and fat which contain temperature information. A noise analysis of the signal model was conducted using the Cramer‐Rao lower bound to evaluate the noise performance of various algorithms, the effects of imaging parameters, and the influence of the water:fat signal ratio in a sample on the temperature estimate. Comparison of the calculated temperature map and thermocouple temperature measurements shows that the maximum temperature estimation error is 0.614°C, with a standard deviation of 0.06°C, confirming the feasibility of this model‐based temperature mapping method. The influence of sample water:fat signal ratio on the accuracy of the temperature estimate is evaluated in a water‐fat mixed phantom experiment with an optimal ratio of approximately 0.66:1. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.