Specific and rapid guanidinium CEST imaging using double saturation power and QUASS analysis in a rodent model of global ischemia

Abstract

PurposeGuanidinium CEST is sensitive to metabolic changes and pH variation in ischemia, and it can offer advantages over conventional pH‐sensitive amide proton transfer (APT) imaging by providing hyperintense contrast in stroke lesions. However, quantifying guanidinium CEST is challenging due to multiple overlapping components and a close frequency offset from water. This study aims to evaluate the applicability of a new rapid and model‐free CEST quantification method using double saturation power, termed DSP‐CEST, for isolating the guanidinium CEST effect from confounding factors in ischemia. To further reduce acquisition time, the DSP‐CEST was combined with a quasi‐steady state (QUASS) CEST technique to process non‐steady‐state CEST signals.MethodsThe specificity and accuracy of the DSP‐CEST method in quantifying the guanidinium CEST effect were assessed by comparing simulated CEST signals with/without the contribution from confounding factors. The feasibility of this method for quantifying guanidinium CEST was evaluated in a rat model of global ischemia induced by cardiac arrest and compared to a conventional multiple‐pool Lorentzian fit method.ResultsThe DSP‐CEST method was successful in removing all confounding components and quantifying the guanidinium CEST signal increase in ischemia. This suggests that the DSP‐CEST has the potential to provide hyperintense contrast in stroke lesions. Additionally, the DSP‐CEST was shown to be a rapid method that does not require the acquisition of the entire or a portion of the CEST Z‐spectrum that is required in conventional model‐based fitting approaches.ConclusionThis study highlights the potential of DSP‐CEST as a valuable tool for rapid and specific detection of viable tissues.