A Half-Volume Coil for Efficient Proton Decoupling in Humans at 4 Tesla

Abstract

A quadrature transmit/receive coil for proton-decoupled An ideal coil configuration for in vivo proton-decoupled NMR spectroscopy requires a highly sensitive 13 C coil as 13 C or 31 P spectroscopy half-volume applications, which retains optimal performance on the 1 H frequency, was built. well as an efficient proton-decoupling coil. Ideally, those coils have very similar areas of sensitivity, yet show no Specifically, no RF field profile distortions due to coil interactions were observed. This and the quadrature 1 H coil de-significant electromagnetic interaction or degenerated field patterns. Both aims are especially difficult to achieve sign resulted in a fourfold improvement in the power requirements over conventional, linear-polarized designs. A single for 13 C applications, since the quarter wavelength of 13 C is very close to the 1 H wavelength. In addition, since the lowpass filter of 00.1 dB insertion loss was sufficient for broadband proton decoupling experiments on a 4 T whole-power absorption increases with B 2 0 , the proton-coil effibody system. Images and spectra show excellent sensitivity ciency may determine the feasibility of decoupling within at both frequencies. Broadband decoupling depicting narrow the FDA guidelines ( 2 -7 ) . metabolite resonances from glutamate, taurine, and creatine Several surface-coil configurations have been used for in the human leg and human brain was possible within FDA broadband-decoupled 13 C MRS in humans (4,(8)(9)(10)(11)(12)(13). Many guidelines for power absorption.applications successfully used two concentric circular surProton decoupling is a necessary requirement to achieve face coils (8-10). A serious drawback of such a configuraoptimal sensitivity for 13 C MR spectroscopy (MRS) and tion is the inherent 1 H flux blockage of the inner 13 C coil, may provide substantial improvements for 31 P MRS. NOE since the 13 C coil is almost short-circuited at the 1 H frequency generation can enhance sensitivity up to threefold for 13 C (9). Consequently the proton-coil performance is rather poor MRS. To a lesser extend, the same holds true for 31 P MRS, adjacent to the 13 C coil, resulting in excessive power requirements for proton decoupling. Despite these drawbacks, conin that 1 H decoupling can increase spectral resolution, especially in the PME and PDE resonances at low magnetic centric coil design was not prohibitive for some clinical applications using small coils at 4.7 T (14) as well as at fields (1), and improved signal-to-noise ratio (SNR) can be obtained by NOE generation. These heteronuclear tech-1.5-2.1 T (15, 16). However, for the volumes needed for human applications at 4 T, we found that the performance niques use relatively long and intense RF irradiation at the 1 H frequency, which can make it difficult to achieve decou-of the proton coil in a double concentric arrangement was not sufficient for decoupling within FDA guidelines. pling in humans within FDA guidelines for power absorption. Both NOE generation and proton decoupling perform Alternatively,...

Clinical experience with 13C MRS in vivo

“…After several fruitless designs, we have adopted that of Adriany and Gruetter;20,21 Bluml and Harris (unpublished) successfully constructed several 'clones' for use in other centers. The half-head field of view ( Fig.…”

Technical and experimental features of Magnetic Resonance Spectroscopy of brain glycogen metabolism

“…single 13 C loop) in combination with 1 H-quadrature coils (i.e. two physicallydecoupled overlapped 1 H loops) have been widely used both in animal [18,29,57,58,78,80,81] and human studies [21,76,77,82]. Relative to the linear coil design, an overlapped quadrature coil enhances sensitivity by a factor of √2 [79,83], and 13 C-quadrature coils have been designed in combination with either a 1 H-volume coil [84] or a 1 H-quadrature coil [85].…”

“…To achieve high 13 C sensitivity with low 1 H power deposition, the linear-13 C coil in combination with the quadrature-1 H coil design has been widely used for rodent [80,86,96] and human studies [21,82,95,97]. As a result, a 3D localization method of 13 C glycogen adapted to that coil design was developed.…”

Localized in vivo hyperpolarization transfer sequences

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In vivo localized and fully adiabatic homonuclear and heteronuclear polarization transfer experiments were designed and performed in the rat brain at 9.4 T after infusion of hyperpolarized sodium [1,[2][3][4][5][6][7][8][9][10][11][12][13] C 2 ] and sodium [1-13 C] acetate. The method presented herein leads to highly enhanced in vivo detection of short-T 1 13 C as well as attached protons.

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“…However, the time delay between the DNP process and the in vitro or in vivo MR measurements as well as the finite uptake and metabolic rates of the biologically relevant organisms restrict the application of the technique to nuclear spins with long-T 1 . Consequently, in vitro and in vivo DNP-enhanced metabolic studies have been so far limited to the detection of nonprotonated low-g-nuclei such as 13 C-labeled carbonyls or 15 N-labeled quaternary amines. However, to fully determine, understand, or model the biochemical transformations taking place in complex biological systems through isotopomer analysis, it would be useful to probe several molecular sites.…”