T1 in high-grade glioma and the influence of different measurement strategies on parameter estimations in DCE-MRI.

BACKGROUND: To investigate the evolution of T1 in tumor and the necessity of baseline T1 (T1 (0)) mapping for the accurate estimation of kinetic parameters during standard therapy using dynamic contrast enhanced (DCE) MRI in patients with high-grade glioma (HGG).

METHODS: Longitudinal DCE-MRI was performed in 23 patients (196 scans) with confirmed HGG. Kinetic parameters were derived from the extended Tofts model and analyzed both using fixed and pixel-wise T1 (0) values estimated from a Look-Locker sequence. Median tumor T1 value from all scans was used for fixed T1 (0) analysis. Dependence of accurate T1 (0) mapping for the estimation of the kinetic parameters was further investigated through computer simulations and histogram analysis.

RESULTS: T1 in tumor increased significantly during and after treatment (P < 0.001). There was a linear correlation between the error in 1/T1 (0) and the resulting error in estimated parameters in both simulations and clinical data (r(2) >0.98 for all parameters). A strong correlation between the estimated longitudinal change in all kinetic parameters obtained using pixel-wise and fixed T1 (0) was observed (r(2) > 0.84 for all parameters). Histogram analysis revealed a linear change (r(2) > 0.62) in K(trans) normalized histogram peak height ratio as function of percentage deviation from the nominal T1 (0) value. No effect of T1 (0) histogram distribution on K(trans) was observed (P = 0.52).

CONCLUSION: Temporal changes in the median kinetic parameters in tumor were equally well described using pixel-wise and fixed T1 (0) despite an increase in T1 (0) over time, suggesting that T1 mapping is not generally required in DCE-MRI based monitoring of glioma patients.