Improved Accuracy and Precision of Tracer Kinetic Parameters by Joint Fitting to Variable Flip Angle and Dynamic Contrast Enhanced MRI Data

Purpose: To improve the accuracy and precision of tracer kinetic model parameter estimates for use in dynamic contrast enhanced (DCE) MRI studies of solid tumors. Theory: Quantitative DCE-MRI requires an estimate of precontrast T-1, which is obtained prior to fitting a tracer kinetic model. As T-1 mapping and tracer kinetic signal models are both a function of precontrast T-1 it was hypothesized that its joint estimation would improve the accuracy and precision of both precontrast T-1 and tracer kinetic model parameters. Methods: Accuracy and/or precision of two-compartment exchange model (2CXM) parameters were evaluated for standard and joint fitting methods in well-controlled synthetic data and for 36 bladder cancer patients. Methods were compared under a number of experimental conditions. Results: In synthetic data, joint estimation led to statistically significant improvements in the accuracy of estimated parameters in 30 of 42 conditions (improvements between 1.8% and 49%). Reduced accuracy was observed in 7 of the remaining 12 conditions. Significant improvements in precision were observed in 35 of 42 conditions (between 4.7% and 50%). In clinical data, significant improvements in precision were observed in 18 of 21 conditions (between 4.6% and 38%). Conclusion: Accuracy and precision of DCE-MRI parameter estimates are improved when signal models are fit jointly rather than sequentially. (C) 2015 Wiley Periodicals, Inc.