The necessity of contrast-enhanced imaging in MRI follow-up of pituitary macroadenomas

Objective: This study aimed to evaluate and compare the diagnostic accuracy and intra-/inter-observer agreement of contrast-enhanced versus non-contrast MRI sequences in the follow-up of pituitary macroadenomas, and to reassess the necessity of gadolinium-based contrast agents based on key imaging parameters. Materials and Methods: In this retrospective study, a total of 139 patients who underwent pituitary MRI and were diagnosed with pituitary macroadenoma at Akdeniz University Hospital between January 1, 2012, and September 1, 2024, were evaluated. The dataset included 417 pituitary MRIs: diagnostic and two follow-up MRIs from 64 non-operated patients, and preoperative plus two late postoperative MRIs from 75 operated patients. Evaluations were performed independently by two observers—one more experienced—using coronal T2-weighted and contrast-enhanced coronal T1-weighted sequences in separate sessions. In non-operated patients, lesion presence, maximum craniocaudal and horizontal dimensions, the shortest intercarotid distance at the horizontal cavernous segment of the internal carotid arteries, Knosp classification, Zurich Pituitary Score, and optic pathway compression were assessed. In operated patients, the presence and localization of residual lesions were analyzed. Intra- and inter-observer agreement was assessed using Intraclass Correlation Coefficient (ICC), Cohen's Kappa, Wilcoxon signed-rank test, and Bland-Altman analysis. Results: In non-operated patients, all lesions were clearly identified on non-contrast T2-weighted sequences. Craniocaudal and horizontal measurements demonstrated high intra- and inter-observer agreement across both sequences. Categorical agreement of the Knosp classification was higher than that of the Zurich Pituitary Score. Because the Zurich Score is calculated using the ratio of horizontal tumor diameter to intercarotid distance, minor differences in distance measurements could cause significant changes in the ratio. Inter-observer agreement in optic pathway compression evaluation was higher on non-contrast sequences. In postoperative follow-up MRIs of operated patients, contrast-enhanced imaging significantly improved inter-observer agreement in evaluating residual lesions, especially in the presence of observers with differing levels of experience. Residual lesion assessment using non-contrast images showed limited but acceptable accuracy when performed by the experienced observer. Discussion&Conclusion: Follow-up MRI examinations of non-operated pituitary macroadenoma cases can be performed without contrast. In operated cases, contrast-enhanced imaging is recommended for late postoperative follow-up in the absence of contraindications; however, when contrast administration is not possible, image interpretation should be performed by experienced radiologists.