In vitro study of relationship between signal intensity and gadolinium-DTPA concentration at high magnetic field strength.

Although gadolinium-diethylene triamine pentaacetic acid (Gd-DTPA) has been used as a contrast material in MRI, it is known that the contrast enhancement effect is not uniform for high concentrations of Gd-DTPA. In order to evaluate the proper pulse sequences for dynamic MRI in aqueous solutions of Gd-DTPA, blood samples and melanoma cells, the signal intensity for several concentrations of Gd-DTPA were measured under inversion recovery (T1-weighted) at high magnetic field strength (7.0 Tesla). For aqueous solutions of Gd-DTPA, signal intensity correlated linearly with the concentration of Gd-DTPA between 0 mmol/L and 4 mmol/L. Using blood and melanoma cells, signal intensity correlated non-linearly with the concentration of Gd-DTPA between 0 mmol/L and 1.5 mmol/L. For concentrations of more than 4 mmol/L in aqueous solutions of Gd-DTPA, 1 mmol/L in blood and 1.5 mmol/L in melanoma, signal intensity decreased with increased Gd-DTPA concentration.