A theoretical analysis of chemical exchange saturation transfer echo planar imaging (CEST‐EPI) steady state solution and the CEST sensitivity efficiency‐based optimization approach. (16th June 2016)

• Record Type: Journal Article
• Authors: Jiang, Weiping; Zhou, Iris Yuwen; Wen, Lingyi; Zhou, Xin; Sun, Phillip Zhe
• Is Part Of: Contrast media & molecular imaging. Volume 11:Number 5(2016:Sep./Oct.)
• Page Start: 415
• Page End: 423
• Publication Date: 2016-06-16
• Subjects: chemical exchange saturation transfer (CEST) -- contrast‐to‐noise ratio (CNR) -- quantitative CEST (qCEST) -- signal‐to‐noise ratio (SNR) -- specific absorption rate (SAR); Diagnostic imaging -- Periodicals; Magnetic resonance imaging -- Periodicals; Contrast media (Diagnostic imaging) -- Periodicals; Contrast Media -- Periodicals; Diagnostic Imaging -- Periodicals; Substances de contraste -- Périodiques; Diagnostics moléculaires -- Périodiques; Imagerie médicale; Substance de contraste; Périodique électronique (Descripteur de forme); Ressource Internet (Descripteur de forme); 616.0754
• DOI: 10.1002/cmmi.1699
• Languages: English
• ISSNs: 1555-4309

Abstract

Abstract : Chemical exchange saturation transfer (CEST) MRI is sensitive to dilute labile protons and microenvironmental properties, augmenting routine relaxation‐based MRI. Recent developments of quantitative CEST (qCEST) analysis such as omega plots and RF‐power based ratiometric calculation have extended our ability to elucidate the underlying CEST system beyond the simplistic apparent CEST measurement. CEST MRI strongly varies with experimental factors, including the RF irradiation level and duration as well as repetition time and flip angle. In addition, the CEST MRI effect is typically small, and experimental optimization strategies have to be carefully evaluated in order to enhance the CEST imaging sensitivity. Although routine CEST MRI has been optimized largely based on maximizing the magnitude of the CEST effect, the CEST signal‐to‐noise (SNR) efficiency provides a more suitable optimization index, particularly when the scan time is constrained. Herein, we derive an analytical solution of the CEST effect that takes into account key experimental parameters including repetition time, imaging flip angle and RF irradiation level, and solve its SNR efficiency. The solution expedites CEST imaging sensitivity calculation, substantially faster than the Bloch–McConnell equation‐based numerical simulation approach. In addition, the analytical solution‐based SNR formula enables the exhaustive optimization of CEST MRI, which simultaneously predicts multiple optimal parameters such as repetition time, flip angle and RF saturation level based on the chemical shift and exchange rate. The sensitivity efficiency‐based optimization approach could simplify and guide imaging of CEST agents, including glycogen, glucose, creatine, gamma‐aminobutyric acid and glutamate. Copyright © 2016 John Wiley & Sons, Ltd. Abstract : A steady state non‐thermal equilibrium CEST MRI solution was derived to take into account key experimental parameters including TR, FA and B1. The solution expedites CEST imaging sensitivity efficiency calculation, enabling simultaneous prediction of multiple optimal parameters based on the chemical shift and exchange rate. The sensitivity efficiency‐based exhaustive optimization approach could simplify and effectively guide CEST MRI experiment.