Objective: While detection of pituitary tumours with magnetic resonance imaging (MRI) may reduce diagnostic costs and improve surgical outcomes for patients with Cushing's disease, the optimal T1-weighted spin-echo (SE) MRI protocol remains unknown. We hypothesized that specific MR scanning parameters influence detection of corticotropinomas.
Design and patients: Between December 1997 and November 2004, 21 of 84 consecutive patients with Cushing's disease had a falsely negative initial pituitary MRI study and a lesion identified subsequently at the National Institutes of Health Clinical Center. This study retrospectively reviewed and compared technical parameters used for the two pituitary T1-weighted SE MRIs in 18 patients with available scans.
Measurements: Repetition time (TR)/echo times (TE), field of view (FOV), matrix size, magnetic field strength, slice thickness, use of gadolinium contrast and the time interval between studies were recorded.
Results: The MRI interscan interval was 5.4 +/- 1.1 months. All scans used gadolinium, matrix sizes were similar and nearly all had 3-mm thick slices. Parameters that differed between the NIH- and externally performed scans were: TR (400 ms vs. 492 +/- 19 ms, P = 0.0002); TE (10.3 +/- 0.5 vs. 17.2 +/- 1.2 ms, P = 0.0003); FOV (12 x 12 cm vs.17 +/- 0.6 x 18 +/- 0.7 cm, P < 0.0001). Immunohistochemistry of tumours resected at transsphenoidal surgery confirmed all to be corticotropinomas.
Conclusions: Not all 'T1-weighted SE' scans are equally accurate. MRI technique, particularly FOV and TR/TE value, influences results. We recommend that endocrinologists consider pituitary MRI parameters when interpreting the results.