Precision-Guided Sampling Schedules for Efficient T1ρ Mapping

PurposeTo describe, assess, and implement a simple precision estimation framework for optimization of spin-lock time (TSL) sampling schedules for quantitative T1 mapping using a mono-exponential signal model. Materials and MethodsA method is described for estimating T1 precision, and a cost function based on the precision estimates is evaluated to determine efficient TSL sampling schedules. The validity of the framework was tested by imaging a phantom with various sampling schedules and comparing theoretical and experimental precision values. The method utility was demonstrated with in vivo T1 mapping of brain tissue using a similar procedure as the phantom experiment. To assist investigators, optimal sampling schedules are tabulated for various tissue types and an online calculator is implemented. ResultsTheoretical and experimental precision values followed similar trends for both the phantom and in vivo experiments. The mean absolute percentage error (MAPE) of theoretical estimates of T1 map signal-to-noise ratio (SNR) was typically 5% in the phantom experiment and 33% in the in vivo demonstration. In both experiments, optimal TSL schedules yielded greater T1 map SNR efficiency than typical schedules. ConclusionThe framework can be used to improve the imaging efficiency of T1 mapping protocols and to guide selection of imaging parameters. J. Magn. Reson. Imaging 2015;41:242-250. (c) 2014 Wiley Periodicals, Inc.