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

Abstract

AbstractPurposeSodium 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.MethodsThe 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.ResultsThe 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.ConclusionSimultaneous 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.