Diffusion-weighted imaging does not seem to be a predictor of consistency in pituitary adenomas.

Purpose: To prospectively evaluate the usefulness of T1-weighted imaging (T1WI) and diffusion-weighted imaging (DWI) sequences in predicting the consistency of macroadenomas. In addition, to determine their values ​​as prognostic factors of surgical outcomes.

Methods: Patients with pituitary macroadenoma and surgical indication were included. All patients underwent pre-surgical magnetic resonance imaging (MRI) that included the sequences T1WI before and after contrast administration and DWI with the apparent diffusion coefficient (ADC) map. Post-surgical MRI was performed at least 3 months after surgery. The consistency of the macroadenomas was evaluated at surgery, and they were grouped into soft and intermediate/hard adenomas. Mean ADC values, signal on T1WI and the ratio of tumor ADC values ​​to pons (ADC_R) were compared with tumor consistency and grade of surgical resection.

Results: A total of 80 patients were included. A softened consistency was found at surgery in 53 patients and hardened in 27 patients. The median ADC in the soft consistency group was 0.532 × 10^-3 mm²/sec (0.306 - 1.096 × 10^-3 mm²/sec), and in the intermediate/hard consistency group was 0.509 × 10^-3 mm²/sec (0.308 - 0.818 × 10^-3 mm²/sec). There was no significant difference between the median values ​​of ADC, ADC_R and signal on T1W between the soft and hard tumor groups, or between patients with and without tumor residue.

Conclusion: Our results did not show usefulness of the DWI and T1WI for assessing the consistency of pituitary macroadenomas, nor as a predictor of the degree of surgical resection.