Short‐echo spectroscopic imaging combined with lactate editing in a single scan

Abstract

A short-echo spectroscopic imaging sequence extended with a frequency-selective multiple-quantum- coherence technique (Sel-MQC) is presented. The method enables acquisition of a complete water-suppressed proton spectrum with a short echo time and filtering of the J-coupling metabolite, lactate, from co-resonant lipids in one scan. The purpose of the study was to validate this combined pulse sequence in vitro and in vivo. Measurements on phantoms confirmed the feasibility of the method, and, for a practical in vivo application, experiments were carried out on eight tumors from two different tumor models [UT-SCC-8 (n = 4) and SAS (n = 4)]. T(1)- and T(2)-weighted metabolite and lipid ratios were calculated, and the tumors showed different values in the central and outer regions. The ratio of the lipid methylene peak area (1.30 ppm) to choline peak area (3.20 ppm) was significantly (p < 0.01) different in the central tumor area between the two models, and lactate was detected in only three out of four tumors in the SAS tumor line. The present approach of combining short-echo spectroscopic imaging and lactate editing allows the characterization of tumor-specific metabolites such as choline, lipid methylene and methyl resonances as well as lactate in a single scan.

Edited1H magnetic resonance spectroscopy in vivo: Methods and metabolites

“…He et al and Hurd et al performed related selective‐MQC experiments in vivo to detect lactate. Melkus et al combined selective‐MQC with short‐echo spectroscopic imaging to characterize tumor‐specific metabolites, such as choline and lactate.…”

Low and High Field Magnetic Resonance for in Vivo Analysis of Seeds

“…Conventional studies of liquid endosperm conducted using either HPLC or GCMS involve the destruction of the compartmentation present in the seed, while non-invasive 1 H MRI both allows the in vivo structure to be determined, and identifies the steady state distribution of several critical metabolites. High field localized 1 H NMR is a well established platform in pre-clinical diagnosis [44,45], but some adjustments were required to adapt the technique for studying the seed. In particular, small NMR coils were introduced in order to improve the signal to noise ratio, since the coils typically used for rodent tissue (inner diameter of 25–40 mm) proved to be too large to obtain an acceptable level of sensitivity in the pea seed.…”

Theoretical description of modern1H in Vivo magnetic resonance spectroscopic pulse sequences

“…). MQF techniques have been used to estimate the concentrations of numerous J ‐coupled metabolites obscured by overlapping resonances, such as GABA, glutathione, lactate, glutamate, myo‐inositol, and glucose . The largest drawback of MQF filters compared with J ‐editing techniques, in addition to yield losses for most spin systems (i.e., loss of signal conversion from SQCs to MQCs and back to SQCs), is the loss of all information regarding singlets, often used for internal concentration referencing or supplementary data analysis.…”