Purpose: To describe, assess, and implement a simple precision estimation framework for optimization of spinlock time (TSL) sampling schedules for quantitative T1r mapping using a mono-exponential signal model.
Materials and Methods: A method is described for estimating T1r 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 T1r 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.
Results: Theoretical 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 T1r 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 T1r map SNR efficiency than typical schedules.
Conclusion: The framework can be used to improve the imaging efficiency of T1ρ mapping protocols and to guide selection of imaging parameters.
- Quantitative mapping
- Spin lock