The peritumoral region was defined as the area in the white matter immediately adjacent to the enhancing (hyperintense on T2-weighted images, but not enhancing on postcontrast T1-weighted images) portion of the tumo.To ascertain whether there were differences in the morphologic parameters of enhancing tumors, we analysed their shape, margins, and enhancement patterns on postcontrast T1-weighted images.  Furthermore, the aim was to detect peritumoral neoplastic cell infiltration by visual assessment of T2-weighted and diffusion-weighted images, including DWI, ADC maps. Relative cerebral blood volumes in these regions were calculated from perfusion-weighted MR data. Spectra from the enhancing tumor, the peritumoral region, and normal brain were obtained from the two-dimensional spectroscopic MR acquisition.                                                                          The differences in the peritumoral area associated with each tumour type can be explained by its different pathophysiologies, which include abnormalities in the tumour endothelium, secretion of the tumour vascular growth factor, and tumour angiogenesis, amongst others.

In high-grade gliomas, the areas of peritumoral tumours show, in addition to morphologically altered capillaries and interstitial water, infiltrating tumour cells along preexisting dilated vascular channels and those formed de novo. In contrast, metastatic edema is purely vasogenic, consisting of fluid devoid of tumor cells, a phenomenon not observed in high-grade glioma edema.

It is noteworthy that the distinct behavior exhibited by high-grade glioma and metastases also leads to an increase in Cho at the peritumoral and tumor levels (prima necrosis).Cho serves as a reliable marker of enhanced membrane synthesis and, consequently, cell multiplication. The Cho/Cr index and the Cho/NAA index serve as biomarkers for the degree of malignancy.It is crucial to acknowledge that N-acetyl aspartate (NAA) is a neuronal marker, and creatinine (Cr) is a molecule that plays a pivotal role in the maintenance of energy-dependent systems in brain cells.A low NAA/Cr coefficient serves as a reliable indicator of malignancy, and this decrease is also quantifiable with significant differences between gliomas of different grades. The final differentiation between high-grade gliomas and metastases is based on a Cho/NAA coefficient greater or less than 1.1, which is the cutoff value, Server et al. in 2010.

As well as changes to the levels of metabolites, the flow of blood measured by rCBV around the tumour also shows important differences between high-grade gliomas and metastases. We have carried out a qualitative study of perfusion; however, other authors such as Law et al. have quantified the increase in perfusion up to 1.39 higher than normal white matter in contrast to perfusion in metastasis which was 0.39 (less than normal white matter).