Development of estimation method for T1 and T2 values using the relaxivity of contrast agent and coagulant for a magnetic resonance imaging phantom.

The T₁ and T₂ values of magnetic resonance imaging phantoms used by researchers should be equivalent to those of the target tissue. However, this is difficult to achieve because of variations in the phantoms depending on the type and concentration of contrast agents and coagulants. The aim of this study was to elucidate the utility of a determination equation derived using the relaxivity of the contrast agent and coagulant. We prepared phantoms using 0.05-10 mmol L^-1 contrast agent (Gadovist^®; Bayer Yakuhin, Ltd., Osaka, Japan) and 0.1-5.0 wt% agar (agar, powder [010-15815]; Fujifilm Wako Pure Chemical Corporation, Osaka, Japan) and measured their T₁ and T₂ values. Determination equations for T₁ and T₂ values were derived using the relaxivity calculated from the T₁ and T₂ values of the contrast agent and coagulant. Subsequently, the determined values were compared with the measured values. The error rate of the determined T₁ and T₂ values were 7.66 ± 6.60% and 5.66 ± 4.05%, respectively, with correlation coefficients of 0.996 and 0.999. These results indicate that this method enables easy and highly accurate estimation of T₁ and T₂ values in MRI phantoms.