Sodium triple quantum MR signal extraction using a single‐pulse sequence with single quantum time efficiency.

Purpose: Sodium triple quantum (TQ) signal has been shown to be a valuable biomarker for cell viability. Despite its clinical potential, application of Sodium TQ signal is hindered by complex pulse sequences with long scan times. This study proposes a method to approximate the TQ signal using a single excitation pulse without phase cycling. Methods: The proposed method is based on a single excitation pulse and a comparison of the free induction decay (FID) with the integral of the FID combined with a shifting reconstruction window. The TQ signal is calculated from this FID only. As a proof of concept, the method was also combined with a multi‐echo UTE imaging sequence on a 9.4 T preclinical MRI scanner for the possibility of fast TQ MRI. Results: The extracted Sodium TQ signals of single‐pulse and spin echo FIDs were in close agreement with theory and TQ measurement by traditional three‐pulse sequence (TQ time proportional phase increment [TQTPPI)]. For 2%, 4%, and 6% agar samples, the absolute deviations of the maximum TQ signals between SE and theoretical (time proportional phase increment TQTPPI) TQ signals were less than 1.2% (2.4%), and relative deviations were less than 4.6% (6.8%). The impact of multi‐compartment systems and noise on the accuracy of the TQ signal was small for simulated data. The systematic error was <3.4% for a single quantum (SQ) SNR of 5 and at maximum <2.5% for a multi‐compartment system. The method also showed the potential of fast in vivo SQ and TQ imaging. Conclusion: Simultaneous SQ and TQ MRI using only a single‐pulse sequence and SQ time efficiency has been demonstrated. This may leverage the full potential of the Sodium TQ signal in clinical applications. [ABSTRACT FROM AUTHOR]