The demonstration of extension of high-grade glioma beyond magnetic resonance imaging defined edema by the use of (11) C-methionine positron emission tomography.

The use of magnetic resonance imaging (MRI) is the current standard for the delineation of target volumes for high-grade gliomas (HGG). While the peritumoral edema as per T2-weighted (T2W) imaging is utilized as basis to delineate the initial borders of the clinical target volume (CTV), those areas enhancing on T1-weighted (T1W) images with gadolinium contrast (T1-Gd) are considered for treatment with further boost. However, recent data has emerged concerning the use of positron emission tomography (PET) with 11 C-methionine, which seemingly provides additional information beyond MRI. We present the case of a gentleman with an inoperable HGG which was imaged with 11 C-methionine-PET ( 11 C-MET-PET)/CT as well as MRI as part of the radiotherapy treatment planning (RTP) process. The differences noted between the MRI and the PET defined volumes are presented. This being a patient who was not operated, the potentially confounding issue of surgery-induced PET-avidity is absent.