In vitro assessment of MR relaxation properties of pituitary adenomas

Proton magnetic relaxation times (T1 and T2) and bound water content were measured in vitro in pituitary adenomas from 15 patients using 90 MHz radiofrequency excitation. These data were compared with those measured in normal pituitary glands obtained from four cats and seven fresh human cadavers. The T1 and T2 measured at 24 degrees C in the tumors (mean +/- SD: 1,170 +/- 80 and 123 +/- 35 ms, respectively) were significantly higher than those of cadaver pituitary (830 +/- 200 and 76 +/- 12 ms) and cat pituitary gland (790 +/- 120 and 69 +/- 10 ms). Although the absolute values were lower, similar differences were present in T1 measured at 4 degrees C. Two-dimensional T2 versus T1 plot was particularly helpful in distinguishing tumor from the normal gland. When tumors were grouped according to density on CT, histology or previous treatment (e.g., irradiation or bromocriptine), there were no significant differences in T1 values between the groups. Bound water content was not found to correlate with T1 or T2 values. We concluded that pituitary adenomas can be distinguished from normal pituitary glands by their different relaxation properties when measured at high frequency in vitro MR.