Total Relaxivities of Material Content in Various Cysts and Ameloblastoma: Implications for Discriminating Different Fluids

Nuclear magnetic resonance T ₁ and T ₂ relaxivities (r ₁ and r ₂) exhibit efficiency of a material to alter the relaxation rates (1/T ₁ and 1/T ₂), and they are being used for diagnostic purposes. The determination of total relaxivities (r _1t and r _2t) of cystic fluid content and ameloblastoma may therefore be useful for discriminative purposes. In order to determine what makes total relaxivities of hemorrhagic cysts, four sets of tubes containing pooled cyst were doped with increasing concentrations of iron, copper, albumin, and γ-globulins. These sets were replaced in a phantom together with six individual cysts and one ameloblastoma. The relaxation times were measured by magnetic resonance imaging operating at 1.5 T. The relaxivities of individual ions and proteins were determined from the slope of the relation between relaxation rates and concentration, while total relaxivities were determined by using the increases in relaxation rates and material content of cystic fluid (MC). Iron, copper, albumin, and γ-globulins were found to be the sources of r _1t and r _2t. Each of r _1t, r _2t, r _1tMC, r _2tMC, and r _2t/r _1t are distinctive parameters for each cystic category and ameloblastoma. Except for MC, the parameters measured for ameloblastoma are significantly smaller than those of cysts. The similarity of the present results to those used in clinical applications suggests that each of r _1t, r _2t, r _1tMC, r _2tMC, and r _2t/r _1t has an ability to discriminate various fluids and masses. The present work also suggests that r _1tMC, r _2tMC, and r _2t/r _1t can be determined in vivo.