Usefulness of dynamic MRI enhancement measures for the diagnosis of ACTH-producing pituitary adenomas.

PURPOSE: The distinction between corticotropin (ACTH)-producing pituitary adenomas and occult ectopic ACTH neoplasms is a challenge and frequently complicated by the detection of nonfunctioning pituitary adenomas on dynamic magnetic resonance imaging (DMRI). Herein, we explored quantitative differences in DMRI measures from ACTH-producing pituitary adenomas.

MATERIALS AND METHODS: Fifty-five patients with pathology confirmed ACTH-producing and 44 with nonfunctioning pituitary adenomas were analysed in this retrospective pilot study. The intensities of adenomas and of adjacent pituitary tissue were measured by drawing a region of interest. Time-intensity curves were then constructed, and quantitative analysis included: enhancement time, enhancement peak and prepeak slope (PPS). Multivariable logistic analysis and receiver operating characteristic curves (ROC) were used to evaluate the parameters.

RESULTS: Quantitative analysis showed that tumour PPS in ACTH-producing adenomas was markedly lower than that in nonfunctioning adenomas (P = 0·0042) and that the PPS of the adjacent pituitary gland was not different (P = 0·2441). The PPS was >3·0 in 59·1% of nonfunctioning adenomas and ≤3·0 in 69·1% of ACTH-producing adenomas (P = 0·0049). Logistic analysis revealed lower tumour PPS levels (P = 0·0123, OR 1·24, 95% CI: 1·05-1·52) were associated with ACTH-producing adenomas. The optimal PPS cut-off determined by ROC analysis was 2·89, with a sensitivity of 69% and specificity of 70%. No significant difference was found between the two groups in enhancement time or enhancement peak.

CONCLUSION: Enhancement parameters in DMRI can help distinguishing ACTH producing from nonfunctioning pituitary adenomas, which could be useful in the differential diagnosis between ACTH-producing pituitary adenomas and ectopic ACTH syndrome complicated with nonfunctioning pituitary adenoma.