Quantification of Gd-DTPA concentration in neuroimaging using T₁3D MP-RAGE sequence at 3.0 T.

PURPOSE: To propose a simple and accurate quantitative method based on the linear relationship between magnetic resonance (MR) signal enhancement (ΔSI=SI(postcontrast)-SI(precontrast)) and gadolinium-diethylenetriaminepentaacetic acid (Gd-DTPA) concentration (C) by using T₁-weighted three-dimensional magnetization-prepared rapid acquisition gradient-echo (T₁3D MP-RAGE) sequence for the in vivo measurement of Gd-DTPA concentration in real-time neuroimaging at 3.0 T.
METHODS: Phantom experiment was carried out to study the linear fitting of signal intensity change vs. Gd-DTPA concentration (ΔSI-C) curve. A goodness-of-fit test was performed to compare the accuracy between the proposed method and the conventional method based on longitudinal relaxation rate (R₁=1/T₁) measurement. The influences on the goodness of fit (R²) and the signal-to-noise ratio (SNR) by sequence parameters were explored. Six human subjects with different brain tumors, who underwent a Gd-DTPA-enhanced MRI, were enrolled for in vivo application of the novel method.
RESULTS: A good linear relationship between ΔSI and Gd-DTPA concentration existed over the concentration range of 0-1 mM (R²=0.985). The linearity of the ΔSI-C curve was as good as that of the 1/T₁-C curve (R²=0.988). Concentrations calculated by both methods had a strong correlation (R²=0.920). An improved linearity of the ΔSI-C curve and an increased SNR can be achieved using sequences with a shorter inversion time (TI) and a higher flip angle. The concentration range of Gd-DTPA in human brain tumors was within the quantitative scope of 0-1 mM.
CONCLUSIONS: The proposed quantitative method based on ΔSI measurement is accurate and applicable for real-time neuroimaging at 3.0 T.