Assessment of a simplified spin and gradient echo (sSAGE) approach for human brain tumor perfusion imaging

The goal of this study was to validate a simplified spin- and gradient-echo (sSAGE) approach to obtain T₁-corrected dynamic susceptibility contrast magnetic resonance imaging (DSC-MRI) data in a clinical brain tumor population. A five-echo SAGE sequence was used to acquire DSC-MRI data (n=8 patients, 3 primary glioma, and 5 brain metastases). The ΔR₂^⁎ and ΔR₂ time series obtained from a nonlinear fit of all echoes (SAGE) were compared to ΔR₂^⁎ and ΔR₂ time series obtained analytically (sSAGE) using three echoes (two GEs and one SE). Through the use of multiple echoes, both methods removed T₁ leakage effects from the ΔR₂^⁎ and ΔR₂ time series, and the sSAGE ΔR₂^⁎ and ΔR₂ time series were highly correlated with those from SAGE, with average correlations of 0.9. The resulting hemodynamic parameters included GE and SE cerebral blood volume (CBV), cerebral blood flow (CBF), mean vessel diameter (mVD), volume transfer constant (K^trans), and volume fraction of the extravascular extracellular space (v_e). For each metric, there was good correlation (>0.86) between sSAGE and SAGE, with no significant differences. The sSAGE method provides T₁-corrected GE and SE DSC-MRI parameters in an efficient and clinically feasible manner.