SECRETORY AND NONSECRETORY PITUITARY-ADENOMAS ARE DISTINGUISHABLE BY 1 T1 MAGNETIC-RELAXATION RATES AT VERY-LOW MAGNETIC-FIELDS IN-VITRO/

RATIONALE AND OBJECTIVES. The authors investigated whether hormonally active and inactive pituitary adenomas can be discriminated in vitro b y magnetic resonance (MR) imaging-related data. METHODS. 1/T1 nuclear magnetic relaxation dispersion profiles were measured for 39 fresh sur gical specimens of secreting and nonsecreting adenomas, classified usi ng clinical criteria or preoperative serum hormone levels. Nonsecretin g adenomas were subdivided into hormone-producing and nonhormone-produ cing by immunostains, At five fields (0.00024 to 1.2 tesla [TI), mean 1/T1 was analyzed for statistically significant differences among thes e three tumor categories. RESULTS. Mean 1/T1 was significantly higher (P < 0.02) for hormone-secreting than for nonsecreting adenomas at fie lds below 0.24 T; no significant difference existed at typical MR imag ing fields (0.5 to 1.5 T). Mean 1/T1 for hormone-producing and nonhorm one-producing, nonsecreting adenomas were not significantly different at any field. CONCLUSIONS. Because 1/T1 at low fields is related to 1/ T2 at imaging fields, it may be possible to detect hormone secretion o f pituitary adenomas noninvasively by MR imaging.