Concluding remarks
As discussed above, the differentiation between GBM recurrence and radiation necrosis remains a crucial challenge (Fig. 1), given that the need for additional surgery in a previously operated brain region increases surgical risk in addition to raising treatment costs. An important current tool is multiparametric MRI using a combination of perfusion and diffusion parameters. Although previous studies [85-91] had found that apparent diffusion coefficient, volume transfer constant, and relative cerebral blood volume are very useful, and the latter is the strongest parameter for differentiating radiation necrosis from GBM tumors [92]. Nael et al. [93] achieved a diagnostic accuracy of 92.8% by combining the use of volume transfer constant and relative cerebral blood volume.
In daily neuro-oncological practice, multiparametric MRI is the most used tool to achieve an accurate differential diagnosis between GBM, inflamed sites, and other brain diseases. Despite its advantages, the use of PET Scan remains limited in many regions of the world due to economical and logistic shortcomes. Overall, the integrated use of different MR and PET approaches, including multiparametric MRI, in addition to perfusion and diffusion parameters [94] may enable increasingly accurate diagnosis based on brain imaging.