Integration of functional brain information into stereotactic irradiation treatment planning using magnetoencephalography and magnetic resonance axonography

Abstract

Purpose To minimize the risk of neurologic deficit after stereotactic irradiation, functional brain information was integrated into treatment planning. Methods and materials Twenty-one magnetoencephalography and six magnetic resonance axonographic images were made in 20 patients to evaluate the sensorimotor cortex ( n = 15 patients, including the corticospinal tract in 6), visual cortex ( n = 4), and Wernicke's area ( n = 2). One radiation oncologist was asked to formulate a treatment plan first without the functional images and then to modify the plan after seeing them. The pre- and postmodification values were compared for the volume of the functional area receiving ≥15 Gy and the volume of the planning target volume receiving ≥80% of the prescribed dose. Results Of the 21 plans, 15 (71%) were modified after seeing the functional images. After modification, the volume receiving ≥15 Gy was significantly reduced compared with the values before modification in those 15 sets of plans ( p = 0.03). No statistically significant difference was found in the volume of the planning target volume receiving ≥80% of the prescribed dose ( p = 0.99). During follow-up, radiation-induced necrosis at the corticospinal tract caused a minor motor deficit in 1 patient for whom magnetic resonance axonography was not available in the treatment planning. No radiation-induced functional deficit was observed in the other patients. Conclusion Integration of magnetoencephalography and magnetic resonance axonography in treatment planning has the potential to reduce the risk of radiation-induced functional dysfunction without deterioration of the dose distribution in the target volume.