# Phase incremented echo train acquisition in NMR spectroscopy

J. H. Baltisberger, B. J. Walder, E. G. Keeler, D. C. Kaseman, K. J. Sanders, and P. J. Grandinetti
068 - J. Chem. Phys.: 136 , 211104-1-4 (2012)

# Abstract

We present an improved and general approach for implementing Echo Train Acquisition (ETA) in magnetic resonance spectroscopy, particularly where the conventional approach of Carr-Purcell-Meiboom-Gill (CPMG) acquisition would produce numerous experimental artifacts. Generally, adding ETA to any $N$-dimensional experiment creates an $N+1$ dimensional experiment, with an additional dimension associated with the echo count, $n$, or an evolution time that is an integer multiple of the spacing between echo maxima. Here we present a modified approach, called Phase Incremented Echo Train Acquisition (PIETA), where the phase of the mixing pulse and every other refocusing pulse, $\phi_P$, is incremented as a single variable, creating an additional phase dimension in what becomes an $N+2$ dimensional experiment. A Fourier transform with respect to the PIETA phase, ${\phi_P}$, converts the $\phi_P$ dimension into a $\Delta p$ dimension where desired signals can be easily separated from undesired coherence transfer pathway signals, thereby avoiding cumbersome or intractable phase cycling schemes where the receiver phase must follow a master equation. This simple modification eliminates numerous artifacts present in NMR experiments employing CPMG acquisition and allows single-scan'' measurements of transverse relaxation and $J$-couplings. Additionally, unlike CPMG, we show how PIETA can be appended to experiments with phase modulated signals after the mixing pulse.

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