Utility of Magnetic Resonance Imaging (Imaging) in Target Volume Definition for Radiosurgery of Acoustic Neuromas

Aim: Acoustic neuromas, also known as vestibular schwannomas are benign and slow-growing tumors arising from neural crest-derived Schwann cells. Treatment of acoustic neuromas targets to achieve local control while preserving hearing without comprimising cranial nerve functionality. In this context, radiosurgery in the form of Stereotactic Radiosurgery (SRS) or fractionated stereotactic radiotherapy (FSRT) offer viable therapeutic options for effective management. Multimodality imaging has gained utmost priority for improved target defnition for radiosurgery. In this study, we assessed the utility of Magnetic Resonance Imaging (MRI) for target volume definition for acoustic neuroma radiosurgery. Methods and materials: Twenty patients treated with radiosurgery for acoustic neuroma at our institution were included. Radiosurgery target definition was performed by using CT simulation images only or by using fused T1 gadolinium-enhanced MR images acquired within 1 week before treatment day. A comparative evaluation was made including volumetric analysis of target volumes. Results: Target volume definition based on CT-only imaging and CT-MR fusion based imaging were comparatively evaluated for 20 patients receiving SRS for acoustic neuroma at our institution. Mean target volumes were 5.7 cc (range: 2.1-13.9 cc) and 6.2 cc (range: 2.3-14.1 cc) with CT-only imaging and CT-MR fusion based imaging, respectively. Conclusion: MRI may be used as a viable imaging modality for acoustic neuromas and may improve target definition for radiosurgery despite the need for further supporting evidence.