CT has limited value in assessment of tumor recurrence versus radiation necrosis given the overlap of imaging characteristics whether IV contrast is used or not [35]. FDG-PET/CT Brain FDG-PET is well established in the literature for the assessment of residual or recurrent tumors following therapy [36]. FDG-PET can also be used to follow low-grade tumors for evidence of degeneration or transformation into a higher-grade malignancy [36]. FDG-PET can differentiate radiation necrosis versus tumor recurrence with sensitivity of 65% to 81% and specificity of 40% to 94% [36]. More recently, FDG-PET co-registered with MRI may have a higher sensitivity in distinguishing radiation necrosis from tumor recurrence at 86% [37]. MEG There is no relevant literature regarding the use of MEG in the evaluation of known seizure disorder with history of tumor unless it is in the setting of presurgical planning. MRI Functional (fMRI) Head There is no relevant literature regarding the use of fMRI in the evaluation of known seizure disorder with history of tumor unless in the setting of presurgical planning. MRI Head MRI of the brain with and without IV contrast is a first-line imaging study in the assessment of residual or recurrent tumors following therapy and is routinely used to monitor malignancy [35,38]. In the setting of stability or resolution, MRI can be used for surveillance; however, in the case of new MRI findings, there can be overlap of imaging characteristics of malignancy versus radiation necrosis [35,36]. Nevertheless, certain characteristics are associated more with recurrent tumor, such as lower apparent diffusion coefficient values compared with radiation necrosis [35]. In addition, the phenomenon of pseudoprogression, a transient period of apparent radiographic deterioration when early delayed radiation effects (<3 months following radiation) can be seen, which can also complicate interpretation of the MRI.
Seizures and Epilepsy. CT has limited value in assessment of tumor recurrence versus radiation necrosis given the overlap of imaging characteristics whether IV contrast is used or not [35]. FDG-PET/CT Brain FDG-PET is well established in the literature for the assessment of residual or recurrent tumors following therapy [36]. FDG-PET can also be used to follow low-grade tumors for evidence of degeneration or transformation into a higher-grade malignancy [36]. FDG-PET can differentiate radiation necrosis versus tumor recurrence with sensitivity of 65% to 81% and specificity of 40% to 94% [36]. More recently, FDG-PET co-registered with MRI may have a higher sensitivity in distinguishing radiation necrosis from tumor recurrence at 86% [37]. MEG There is no relevant literature regarding the use of MEG in the evaluation of known seizure disorder with history of tumor unless it is in the setting of presurgical planning. MRI Functional (fMRI) Head There is no relevant literature regarding the use of fMRI in the evaluation of known seizure disorder with history of tumor unless in the setting of presurgical planning. MRI Head MRI of the brain with and without IV contrast is a first-line imaging study in the assessment of residual or recurrent tumors following therapy and is routinely used to monitor malignancy [35,38]. In the setting of stability or resolution, MRI can be used for surveillance; however, in the case of new MRI findings, there can be overlap of imaging characteristics of malignancy versus radiation necrosis [35,36]. Nevertheless, certain characteristics are associated more with recurrent tumor, such as lower apparent diffusion coefficient values compared with radiation necrosis [35]. In addition, the phenomenon of pseudoprogression, a transient period of apparent radiographic deterioration when early delayed radiation effects (<3 months following radiation) can be seen, which can also complicate interpretation of the MRI.