Pulsed saturation transfer contrast

TLDR

In vivo 1H NMR image contrast normally relies on macroscopic T1 and T2 relaxation, but recent studies have shown cross‑relaxation can provide contrast, and the long spin‑lattice relaxation of the target spin pool suggests pulse methods could be used for saturation. The study demonstrates that short‑T2 spin pools can be selectively saturated using short, intense RF pulses. The authors achieve selective saturation of short‑T2 pools with short, intense RF pulses, measure cross‑relaxation time constants via saturation recovery, and avoid the high SAR and auxiliary amplifiers previously required for broad‑lineshape pools. The method produces in vivo magnetization‑transfer‑weighted images on commercial whole‑body scanners without additional hardware.

Abstract

Abstract In vivo 1 H conventional NMR image contrast generation usually relies on the macroscopic T 1 and T 2 relaxation parameters of the tissues of interest. Recently cross‐relaxation related image contrast has been reported by Wolff and Balaban in animal models. Due primarily to the broad lineshape of the intended saturation spin pool and the use of off‐resonance irradiation, high specific absorption rate and an auxiliary RF amplifier have been necessary to produce these images. The relatively long spin‐lattice relaxation property of this spin pool, however, suggests the use of pulse methods to achieve saturation. In this paper, we show that short‐T 2 spin pools can be selectively saturated with short intense RF pulses. Cross‐relaxation time constants can be measured using the technique of saturation recovery. In vivo magnetization‐transfer‐weighted images can be produced using pulses on commercial whole‐body imagers without additional hardware.