Magnetic resonance elastography detects tumoral consistency in pituitary macroadenomas

Most pituitary macroadenomas (PMA) are soft and suckable allowing transsphenoidal resection. A small percentage of PMA are firm, which significantly alters the time, technical difficulty, and effectiveness of transsphenoidal surgery. No current imaging technology can reliably assess PMA viscoelastic consistency in preparation for surgery. Magnetic resonance elastography (MRE) is an MRI-based technique that measures the propagation of mechanically induced shear waves through tissue to calculate stiffness. We prospectively evaluated MRE in 10 patients undergoing transsphenoidal resection of PMA to determine feasibility and potential usefulness.

10 patients with PMA > 2.0 cm in maximum diameter were prospectively imaged with MRE prior to transsphenoidal surgery. Mean patient age was 59.5 ± 16.2 (22-78) years. Five were female and five male. MRE was performed with a modified single-shot spin-echo echo-planar-imaging pulse sequence on a 3T MRI. MRE values were independently calculated. The surgeon, blinded to the MRE results, graded tumor consistency at surgery as soft, intermediate, or firm. Chi-squared test compared surgical grading and MRE stiffness values.

MRE was accomplished in all patients with excellent resolution. By surgical categorization, six tumors were soft and four intermediate. The mean MRE value for soft tumors was 1.38 ± 0.36 (1.08-1.87) kPa, while for intermediate tumors it was 1.94 ± 0.26 (1.72-2.32) kPa (p = 0.020).

Determination of PMA stiffness is feasible with MRE. There was a statistically significant difference in MRE values between soft and intermediate PMAs. Further study in a larger series is ongoing to determine whether MRE will prove useful in preoperative planning for PMA.