Density matrix calculations of AB spectra from multipulse sequences: Quantum mechanics meets In vivo spectroscopy

Abstract Localized in vivo spectroscopic studies are generally performed with successive, spatially orthogonal, slice‐selective radio‐frequency (rf) pulses so that the received signal is confined to a particular volume of interest. Although these techniques spatially restrict the signal, successive rf pulses applied prior to signal acquisition give rise to complex spectral modulations for coupled spin systems. Interpulse timing delays, rf flip angles, and phases all affect these modulations, which must be fully understood and appreciated if sequences are to be optimized for specific in vivo spectroscopic studies. The density matrix formalism is particularly suited for this task. Our purpose is to demonstrate how the density matrix formalism is used to study spectral modulations induced by selected multipulse sequences for an AB system.