PET-guided gamma knife radiosurgery in brain tumors: a brief review

This mini-review aims to survey the role of positron emission tomography (PET) imaging as an imaging modality for therapy planning before gamma knife radiosurgery (GKRS) in patients experiencing brain tumors. A comprehensive literature search of published papers in the PubMed/MEDLINE database regarding pre-GKRS PET imaging was carried out. We have included all human studies in this field. Although the routine imaging for GKRS guiding is magnetic resonance imaging (MRI), functional imaging modalities including PET have a complementary role for lesion targeting. The mostly used radiotracers for PET-guided GKRS are 2-[18F]fluoro-2-deoxy-D-glucose (2-[18F]FDG) and L-[methyl-11C]methionine ([11C]MET). Herein, we summarize the result of the studies which used 2-[18F]FDG or [11C]MET PET as a complementary imaging method for GKRS guiding. Finally, the results of these limited available studies are in favor of the crucial complementary role of PET imaging in addition to MRI, in terms of lesion targeting and consequently, therapy outcome. Although not enough studies were available on the role of PET imaging for guiding GKRS, it would seem that the integration of PET data into GKRS treatment planning may represent an important step toward further developments in radiosurgery, especially GKRS. Yet, there is no definite indication for pre-GKRS PET imaging; however, most of the studies used PET imaging when there were lesions with an ill-defined border in MRI. It seems that [11C]MET PET might provide more accurate imaging data than 2-[18F]FDG for lesion targeting; however, studies with head to head comparison of these two modalities are needed.