Comparison of MRI techniques for detecting microadenomas in Cushing's disease

Abstract

OBJECTIVE Many centers use conventional and dynamic contrast-enhanced MRI (DMRI) sequences in patients with Cushing's disease. The authors assessed the utility of the 3D volumetric interpolated breath-hold examination, a spoiled-gradient echo 3D T1 sequence (SGE) characterized by superior soft tissue contrast and improved resolution, compared with DMRI and conventional MRI (CMRI) for detecting microadenomas in patients with Cushing's disease. METHODS This study was a blinded assessment of pituitary MRI in patients with proven Cushing's disease. Fifty-seven patients who had undergone surgery for Cushing's disease (10 male, 47 female; age range 13-69 years), whose surgical findings were considered to represent a microadenoma, and who had been examined with all 3 imaging techniques were included. Thus, selection emphasized patients with prior negative or equivocal MRI on referral. The MRI annotations were anonymized and 4 separate imaging sets were independently read by 3 blinded, experienced clinicians: a neuroradiologist and 2 pituitary surgeons. RESULTS Forty-eight surgical specimens contained an adenoma (46 ACTH-staining adenomas, 1 prolactinoma, and 1 nonfunctioning microadenoma). DMRI detected 5 adenomas that were not evident on CMRI, SGE detected 8 adenomas not evident on CMRI, including 3 that were not evident on DMRI. One adenoma was detected on DMRI that was not detected on SGE. McNemar's test for efficacy between the different MRI sets for tumor detection showed that the addition of SGE to CMRI increased the number of tumors detected from 18 to 26 (p = 0.02) based on agreement of at least 2 of 3 readers. CONCLUSIONS SGE shows higher sensitivity than DMRI for detecting and localizing pituitary microadenomas, although rarely an adenoma is detected exclusively by DMRI. SGE should be part of the standard MRI protocol for patients with Cushing's disease.

Keywords: ACTH = adrenocorticotropic hormone; CMRI = conventional MRI; Cushing's disease; DMRI = dynamic contrast-enhanced MRI; FSH = follicle-stimulating hormone; IPSS = inferior petrosal sinus sampling; MRI; SE = spin echo; SGE = spoiled-gradient echo 3D T1 sequence; SPGR = spoiled gradient–recalled acquisition; VIBE = volumetric interpolated breath-hold examination; pituitary microadenoma; pituitary surgery.