Purpose:
To compare T1 values of blood and myocardium at 1.5T and 3T before and after administration of Gd-DTPA-BMA in normal volunteers, and to evaluate the distribution of contrast media between myocardium and blood during steady state.
Materials and Methods:
Ten normal subjects were imaged with either 0.1 mmol/kg (N = 5) or 0.2 mmol/kg (N = 5) of Gd-DTPA-BMA contrast agent at 1.5T and 3T.T1 measurements of blood and myocardium were performed prior to contrast injection and every five minutes for 35 minutes following contrast injection at both field strengths. Measurements of biodistribution were calculated from the ratio of ΔR1 (ΔR1myo/ΔR1blood).
Results:
Precontrast blood T1 values (mean ± SD, N = 10) did not significantly differ between 1.5T and 3T (1.58 ± .13 sec, and 1.66 ± .06 sec, respectively; P > 0.05), but myocardium T1 values were significantly different (1.07 ± .03 sec and 1.22 ± .07 sec, respectively; P < 0.05). The field-dependent difference in myocardium T 1 postinjection (T1@3T - T1@1.5T) decreased by approximately 72% relative to precontrast T1 values, while the field-dependent difference of blood T1 decreased only 30% postcontrast. Measurements of ΔR1myo/ΔR1blood were constant for 35 minutes postcontrast, but changed between 1.5T and 3T (0.46 ± .06 vs. 0.54 ± .06, P < 0.10).
Conclusion:
T1 is significantly longer for myocardium (but not blood) at 3T compared to 1.5T. The differences in T1 due to field strength are reduced following contrast administration, which may be attributed to changes in ΔR 1myo/ΔR1blood with field strength.