Application of a BIlinear Rotation Decoupling (BIRD) filter in combination with J‐difference editing for indirect ¹³C measurements in the human liver

Abstract

Purpose Recently, we introduced a quantum coherence based method (ge‐HSQC) for indirect 13C‐MRS in the liver to track 13C‐labeled lipids into the hepatic lipid pool in vivo. This approach is more robust in case of respiratory motion, however, inherently leads to a signal loss of 50% when compared with a conventional J‐difference editing technique (JDE). Here, we intend to improve the robustness of a regular JDE (STEAM‐ACED) with the use of a BIlinear Rotation Decoupling (BIRD) filter to achieve 100% higher signal gain when compared with ge‐HSQC. Methods To determine the efficiency of the BIRD filter 1H‐[13C] lipid spectra were acquired on 3T from a peanut oil phantom, with three different MR sequences: ge‐HSQC, STEAM‐ACED, and the BIRD filter together with STEAM‐ACED (BIRD‐STEAM‐ACED). Finally, our proposed method is tested in vivo in five healthy volunteers with varying liver fat content. In these subjects we quantified the 1H‐[13C]‐signal from the hepatic lipid pool and determined 13C enrichment, which is expected to be 1.1% according to the natural abundance of 13C. Results The application of the proposed BIRD filter reduces the subtraction artifact of 1H‐[12C] lipid signal efficiently in JDE experiments, which leads to a signal gain of 100% of 1H‐[13C]‐lipid signals when compared with the ge‐HSQC. Phase distortions in vivo were minimal with the use of BIRD compared with STEAM‐ACED, which enabled us to robustly quantify the 13C‐enrichment in all five subjects. Conclusion The BIRD‐STEAM‐ACED sequence is an efficient and promising tool for 13C‐tracking experiments in the human liver in vivo.

In-cell NMR: Why and how?

“…The field would be impossible to cover entirely and is well beyond our scope. The common INEPT has been the most widely used by the in-cell NMR community, but recent applications of BIRD or TANGO on live material show that these can also yield interesting information [1066,1649].…”

MR‐Nucleomics: The study of pathological cellular processes with multinuclear magnetic resonance spectroscopy and imaging in vivo

“…172 In a more recent experiment, the double-quantum coherence proton signal (arising from the dipole-dipole interaction between the lipid proton and the water proton) was used to specifically detect the brown adipose tissue in human subjects, making use of the difference in lipid droplet size between brown adipose tissue and white adipose tissue. 173 A spectral editing technique based on the J-coupling between proton and 13 C was proposed to evaluate the 13 C-metabolites by observing 1 H signals, overcoming the low natural abundance of 13 C. [174][175][176][177] In general, spectral editing techniques could potentially be helpful in providing complementary information on the tissue/lesion microenvironment by exploiting nucleus-nucleus coupling and on enhancing observable signal in MN studies through polarization transfer. However, the potential of clinical translation still requires further investigation regarding the trade-off between operational complexity and clinical values.…”

Non-Invasive Analysis of Human Liver Metabolism by Magnetic Resonance Spectroscopy

“…Thus, the signal dispersion is limited to that of 1 H, which effectively precludes shotgun observation of arrays of 13 C-enriched metabolites but may, nevertheless be effective for observation of near-isochronous 13 C-enriched signals such as the methylene carbons of triglyceride fatty acids [73]. Veeraiah et al applied a similar approach to demonstrate that the background 13 C-methylene signals of hepatic fatty acids in healthy subjects could be quantified in vivo with high sensitivity and minimal interference from 1 H- 12 C signals [74].…”