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 developing the surgical plan for glioma. Diagnostic neuroimaging consists mainly of CT and MRI, both of which 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 The nature of the tumor (astrocytoma, oligodendroglioma and glioblastoma multiforme or other diseases, etc.) ③ Can the surgery be performed safely? Skin flap, bone flap, location of cortical incision, adjacency of cortical functional area to the tumor, location of cortical drainage veins In general CT is highly superior in diagnosing the characteristic calcification of oligodendrogliomas or the acute phase of intra-tumoral hemorrhage, and this examination should be done. Low-grade gliomas appear hypointense on CT images and show a high signal occupying image on MRI T2-weighted image (T2-weighted image, T2WI), and neither enhancement scan is enhanced. 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. Jiang Tao, Department of Neurosurgery, Tiantan Hospital, Beijing, China Table 2-1-1 MRI imaging features of adult gliomas Histologic type T1WI T2WI edema Enhancement features Astrocytoma Low signal, high signal, mild, no enhancement Occurs in cortical white matter junction Oligodendroglioma Low signal, high signal, mild, sometimes enhancement Occurs in cortical white matter junction Interstitial astrocytomas Low signal, wider, higher signal, severe, inhomogeneous enhancement Glioblastoma multiforme Low signal Widespread high signal Severe Uneven, circumscribed, multihomogeneous Occurs in deep white matter Gliomas tend to grow aggressively along the nerve fiber tracts of the white matter MRI coronal images are useful to show whether the tumor is aggressive toward the right and left hemispheres. For example, MRI coronal images are most likely to show that frontal glioblastoma multiforme grows contralaterally and aggressively via the anterior crossed fibers. 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, etc. MRI can not only help in the qualitative diagnosis of the tumor, but also distinguish whether the tumor is infiltrative or expansive, and the sagittal-coronal-axial scanning of MRI can help in the formulation of surgical plan, and it can be used as a means of postoperative follow-up examination. Non-tumor diseases that must be differentiated on imaging include intracerebral hematoma (especially in the subacute to chronic stages), hemorrhagic infarction, venous infarction, multiple sclerosis, some white matter lesions, encephalitis, and brain abscess. 1) The value of neuroimaging to determine the aggressiveness of gliomas CT began to be used in neurosurgery after the mid-1970s. Enhanced CT scans (contrast-enhanced CT scans) of gliomas show increased signal in the area of the lesion, with surrounding areas being 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 areas of increased signal, but at least it is possible to 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 postoperative residual gliomas with an accuracy of more than 77%. Enhanced scans within 72 hours after surgery (preferably within 24 hours) are not affected by postoperative artifacts, so this technique can be used to determine the amount of glioma remaining after surgery when conditions permit, and can be used as a baseline for future patients to determine whether the tumor is a recurrent tumor or radiation brain necrosis. If there is an area of enhancement on postoperative MRI, it suggests that this area 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 is an uneven area of enhancement, but even the enhancement of the MRI does not give a good indication of the area of aggression 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. This part of the tissue is the 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 the 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. Here the question arises as to what image is reflected in the T2-weighted image? Current research suggests that T2-weighted images reflect an edematous zone, 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. (2) The value of neuroimaging in determining postoperative radionecrosis of gliomas Currently, radiation therapy, including stereotactic radiosurgery, is a routine treatment for gliomas, but radiation necrosis of normal brain tissues caused by radiation therapy is also very common in the clinic.Forsyth et al. studied 51 cases of different grades of gliomas that underwent conventional radiotherapy after surgery. Forsyth et al. studied 51 postoperative gliomas of different grades treated with conventional radiotherapy, and found that 59% of the patients had tumor recurrence, 6% had radionecrosis, and 33% had recurrent tumor tissue in the necrotic tissue.Masciopinto performed biopsy on 10 cases of gliomas highly suspected of having recurrence after radiotherapy, and found that 70% had recurrent tumors after surgery, and 30% had 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 areas may also show occupying signs, localized structural destruction of brain tissue, and are clinically slow to develop (may remain unchanged for more than 10 months); areas of enhancement tend to reside in the white matter, far away from the primary lesion, and may show ring-like enhancement foci. Like recurrent gliomas, radionecrotic foci appear as enhancing images on CT and as markedly enhanced signals on MRI T2-weighted images. If the diagnosis of radionecrosis is established in the clinic, the doctor should not take it lightly, and should regularly review and closely observe the imaging changes of radionecrosis lesions. (3) The value of neuroimaging to determine the postoperative residuals of glioma The determination of postoperative residuals of glioma by neuroimaging can evaluate the effect of surgical treatment on the one hand, and can be used as a prognostic indicator after surgical treatment on the other hand. The amount of postoperative tumor residue 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.