Evaluating the use of a continuous approximation for model-based quantification of pulsed chemical exchange saturation transfer (CEST)
Journal
Journal of Magnetic Resonance
Journal Volume
222
Pages
88-95
Date Issued
2012
Author(s)
Abstract
Many potential clinical applications of chemical exchange saturation transfer (CEST) have been studied in recent years. However, due to various limitations such as specific absorption rate guidelines and scanner hardware constraints, most of the proposed applications have yet to be translated into routine diagnostic tools. Currently, pulsed CEST which uses multiple short pulses to perform the saturation is the only viable irradiation scheme for clinical translation. However, performing quantitative model-based analysis on pulsed CEST is time consuming because it is necessary to account for the time dependent amplitude of the saturation pulses. As a result, pulsed CEST is generally treated as continuous CEST by finding its equivalent average field or power. Nevertheless, theoretical analysis and simulations reveal that the resulting magnetization is different when the different irradiation schemes are applied. In this study, the quantification of important model parameters such as the amine proton exchange rate from a pulsed CEST experiment using quantitative model-based analyses were examined. Two model-based approaches were considered - discretized and continuous approximation to the time dependent RF irradiation pulses. The results showed that the discretized method was able to fit the experimental data substantially better than its continuous counterpart, but the smaller fitted error of the former did not translate to significantly better fit for the important model parameters. For quantification of the endogenous CEST effect, such as in amide proton transfer imaging, a model-based approach using the average power equivalent saturation can thus be used in place of the discretized approximation. ? 2012 Elsevier Inc. All rights reserved.
Subjects
Amide proton transfers
Analysis and simulation
Average field
Average power
Bloch-McConnell equations
Chemical exchange saturation transfer
Clinical application
Clinical translation
Diagnostic tools
Experimental data
Hardware constraints
Irradiation pulse
Magnetization transfer
Model based approach
Model parameters
Model-based analysis
Proton exchange
Short pulse
Specific absorption rate
Time dependent
Amides
Irradiation
Proton transfer
Saturation magnetization
amine
proton
water
algorithm
article
chemistry
computer simulation
electromagnetic field
image processing
image quality
methodology
nuclear magnetic resonance imaging
statistical analysis
statistical model
Algorithms
Amines
Computer Simulation
Data Interpretation, Statistical
Electromagnetic Fields
Image Processing, Computer-Assisted
Magnetic Resonance Imaging
Models, Statistical
Phantoms, Imaging
Protons
Water
Type
journal article