Repeatability of a reference region model for analysis of murine DCE-MRI data at 7T

Purpose: To test the repeatability of a reference region (RR) model for the analysis of dynamic contrast-enhanced MRI (DCE-MRI) in a mouse model of cancer at high field. Materials and Methods: Seven mice were injected with 10 ⁶ 4T1 mammary carcinoma cells and imaged eight to 10 days later on a Varian 7.0T scanner. Two DCE-MRI studies were performed for each mouse (separated by 2.5 hours). The RR model was used to analyze the data, and returned estimates on the perfusion-permeability index (K^trans) for the RR and the tissue of interest (TOI), as well as the extravascular extracellular volume fraction (v_e) for the TOI. Results: When the first injection was compared with the second injection, all parameters tested were highly correlated (r² = 0.90, 0.62, 0.82 for the RR K ^trans, TOI K^trans, and TOI v_e, respectively, with P < 0.001 for all). To observe a statistically significant change (at the 5% level) in a treatment study with seven animals in each group, log ₁₀ changes of 0.084 and 0.077 in the tumor K^trans and v_e. respectively, are required. Conclusion: If a reliable arterial input function (AIF) is unavailable, the RR model is a reasonable alternative to measuring MRI contrast-agent (CA) kinetics in mouse models of cancer at high field.