Simultaneous Measurement of CEST and $$$T_1$$$ using Model-based Multi-Pool-Lorentzian Look-Locker Reconstruction

Motivation: Conventional quantitative CEST experiments require the additional determination of $$$T_1$$$. CEST sequences include $$$T_1$$$ relaxation periods that can be exploited to estimate $$$T_1$$$ simultaneously to the CEST parameters. Goal(s): The development of a technique for efficient simultaneous quantification of CEST contrast and $$$T_1$$$. Approach: Integration of a FLASH acquisition train after conventional CEST saturations. Simultaneous CEST contrast and $$$T_1$$$ fitting is achieved by extending the Lorentzian model of the CEST spectrum with a Look-Locker model for the FLASH readout. Results: The proof-of-concept was implemented, and first results are demonstrated in a two pools phantom and a four pool in vivo study. Impact: The presented technique enables calculating $$$T_1$$$ corrected quantitative CEST results from one measurement. This simplifies the application of the apparent exchange-dependent relaxation ($$$MTR_{AREX}$$$), the quasi-steady-state$$$\;$$$contrast and other CEST metrics, which require a $$$T_1$$$ map, making them more accessible.