Modern neurosurgery has clear requirements for neuroimaging techniques to diagnose gliomas, taking into account the size and extent of the tumor, and the adjacency of the tumor to important surrounding structures (including important arteries, cortical veins, and cortical functional areas). Neuroimaging plays the most important role in the development of surgical plan for glioma. Diagnostic neuroimaging consists mainly of CT and MRI, both of which can provide a relatively precise anatomical location of the tumor within the skull.MRI is superior to CT, and MRI can show the extent of invasion of the lesion. When we suspect a glioma we should consider the following in the following order: ① Is it a glioma, its location, size, extent, and relationship to surrounding vital structures? ② What is the nature of the tumor (astrocytoma, oligodendroglioma and glioblastoma multiforme or other diseases, etc.)? (iii) Can the surgery be performed safely? The location of the skin flap, bone flap, cortical incision, the adjacency of the functional cortical area to the tumor, and the location of the cortical drainage vein? In general, CT is highly superior in diagnosing the characteristic calcification of oligodendroglioma or the acute stage of intra-tumoral hemorrhage, and this examination should be done. Low-grade gliomas appear hypointense on CT images and high signal occupying images on MRI T2-weighted images, neither of which is enhanced on intensified scans. However, as many as 25-30% of low-grade glioma cases may have contrast enhancement on CT and MRI T2-weighted images. According to traditional diagnostic criteria, contrast-enhanced images are present only in patients with high-grade gliomas because of contrast leakage from high-grade gliomas that disrupt the blood-brain barrier. However, up to 25% of patients with high-grade gliomas can have no contrast-enhanced images. Table 2-1 shows the MRI imaging features of common gliomas. Gliomas tend to grow aggressively along the nerve fiber tracts in the white matter, and MRI coronal images are useful in showing whether the tumor is aggressive toward the right and left hemispheres. For example, MRI coronal images are most likely to show that glioblastoma multiforme in the frontal lobe grows contralaterally and aggressively via the anterior crossed fibers. The sagittal plane is good for showing the anterior-posterior growth direction of the tumor, especially for confirming the positional relationship with the central sulcus or ventricles. MRI can not only help in the qualitative diagnosis of the tumor, but also can better distinguish whether the tumor is infiltrative growth or expansive growth, and MRI sagittal-coronal-axial scanning can help in the development of surgical planning.MRI can also be used as a means of postoperative follow-up examination. The non-tumor diseases that must be differentiated on imaging include intracerebral hematoma (especially subacute to chronic), hemorrhagic infarction, venous infarction, multiple sclerosis, some white matter lesions, encephalitis, and brain abscess. 1, the value of neuroimaging to determine the aggressiveness of glioma After the mid-1970s CT began to be used in the field of neurosurgery. Contrast-enhanced CT scans of gliomas show increased signal in the lesion area, and the surrounding area is hyper- or isointense. Autopsy and serial stereotactic biopsy studies have confirmed that supratentorial glioma areas of high signal are the solid portion of the tumor. The surrounding areas of hyperdense enhancement are areas of peritumoral edema mixed with tumor cells. It is not possible to determine the malignancy of a glioma based on the level of signal in the area of signal enhancement, but at least it can indicate that the stronger the signal, the higher the density of blood vessels in the tumor area. Comparison of autopsy and enhanced CT scans revealed that the tumor area determined from CT images was 2 cm smaller than the actual area of the glioma, and that CT is not a good judge of residual gliomas. Determination of glioma boundaries and postoperative recurrence MRI is superior to CT.MRI can well determine the postoperative residual glioma with an accuracy of more than 77%. Enhanced scanning within 72 hours after surgery (preferably within 24 hours) is not affected by postoperative artifacts, so this technique can be applied to determine the amount of glioma remaining after surgery when conditions permit, and serve as a benchmark for future patients to determine whether the tumor is a recurrence of the tumor after surgery or radiation brain necrosis. If there are areas of enhancement on postoperative MRI, it is suggested that these areas of enhancement may be a high incidence of postoperative recurrence. Grade III and IV astrocytomas grow aggressively in the cerebral hemispheres, and the main body of the tumor has uneven areas of enhancement, but even the enhanced MRI does not give a good indication of the aggressive areas of the glioma. We know that the MRI image of glioma actually contains two parts: (1) the parenchymal part of the tumor, i.e., the main part of the tumor; and (2) the invasive edge of the tumor. The parenchymal part of the tumor is the damaged part of the blood-brain barrier, which is shown as an enhanced image on MRI, and this part of the tissue is tumor tissue without normal nerve tissue, which is generally functionless and can be resected. Tumor invasion edge part is the part of the tumor invading to the surrounding normal nerve tissue, this part of the tissue can be shown as abnormal on T2 image, in the surgical treatment do not have to blindly expand the scope of surgical resection to remove the parenchymal part of the tumor, and in special cases can be done lobectomy. Earnest on a group of untreated gliomas including grade III or IV gliomas through stereotactic biopsy and enhanced CT, MRI image comparison study, found that MRI is better than CT, but in the MRI T2-weighted image on the performance of normal brain tissue part of the biopsy can still be found in tumor cells. On the contrary Johnson concluded that the invasive boundaries of gliomas in the white matter region of the brain can be better determined by MRI T2-weighted images. This raises the question of what image does a T2-weighted image reflect? Current research suggests that T2-weighted images reflect a band of edema, demyelinated nerve fibers, and other degraded tissues rather than true cellular tissues or atypically proliferating tumor cells. However, at present, there is no other means to judge the boundary of tumor tissue better, so clinically, T2-weighted image is still used as a more reliable index to reflect the boundary of tumor tissue. Neuroimaging to determine the value of postoperative radionecrosis of glioma Currently, radiation therapy, including stereotactic radiosurgery, is a conventional treatment for glioma, but radionecrosis caused by radiation therapy to normal brain tissue is also very common in clinical practice.Forsyth et al. studied 51 cases of glioma of different grades that underwent conventional postoperative radiotherapy, and found that 59% of the patients underwent regular postoperative examinations, and 59% of the patients underwent regular postoperative examinations. Through postoperative examinations, 59% of the patients were found to have tumor recurrence, 6% of the patients had radionecrosis, and 33% of the necrotic tissues had recurrent tumor tissues. Masciopinto’s biopsy of 10 gliomas highly suspected to be recurrent after radiation therapy revealed 70% postoperative tumor recurrence and 30% radionecrosis. In summary, existing conventional imaging cannot well differentiate between radiation brain necrosis and tumor recurrence. CT and MRI images of necrotic areas are very similar to those of postoperative glioma recurrence and are difficult to distinguish. The necrotic area may also show occupying signs, localized structural destruction of brain tissue, and develop slowly clinically (may remain unchanged for more than 10 months); the enhancing area is mostly located in the white matter, far away from the primary lesion, and may show ring-like enhancing foci. Like recurrent gliomas, radionecrotic foci show enhancement on CT and a markedly enhanced signal on MRI T2-weighted images. If the diagnosis of radionecrosis is confirmed in the clinic, the doctor should not take it lightly, and should review regularly and closely observe the imaging changes of radionecrosis lesions. The value of neuroimaging to determine the postoperative residuals of glioma The postoperative residuals of glioma can be evaluated by neuroimaging on the one hand, and on the other hand, it can be used as the prognostic index after surgical treatment. The amount of postoperative residual tumor can directly affect the survival period. At present, we do not have a good method to determine the amount of tumor residuals after surgery, and clinically, we usually review the enhanced CT and MRI within 72 hours after surgery to determine the amount of tumor residuals after surgery. However, the value of neuroimaging in determining the residual amount of glioma after surgery is still controversial, because the enhanced portion of the tumor does not necessarily represent the residual amount of the tumor, and the echogenicity of the vascular injury during the surgery can also be shown as an enhanced image on the image. Postoperative enhancement of vascular injury peaks at 7 days after surgery and disappears after 4 weeks. It is believed that early postoperative review of CT and MRI can accurately determine the amount of tumor residue after surgery, and the review of CT should be done within 4 days after surgery, and the review of MRI should be done within 2 days after surgery, preferably within 24 hours after surgery.