After the introduction of neurosurgical navigation system in the 1990s, it has brought great convenience to the precise positioning of intracranial tumors and become a powerful tool for microinvasive neurosurgery, which can accurately display the three-dimensional spatial location of intracranial lesions and their adjacent important nerve and vascular structures to ensure the most precise positioning and minimal damage of surgery. The disadvantage is that gravity, cerebrospinal fluid loss, brain tissue swelling, and lesion removal can lead to brain tissue displacement, causing errors and affecting navigation accuracy. In the 1950s, some scholars tried to apply ultrasound in brain tumor surgery to explore the problems of surgical access design, localization, and determination of the presence of tumor remnants after surgical resection. Compared to intraoperative CT or MRI, intraoperative ultrasound is simple to apply, economical and convenient, does not occupy space, and is cost-effective, thus becoming the most prominent tool for navigating brain shift correction during surgery. Ultrasonography depends mainly on the different acoustic properties between brain tumors and normal brain tissue, relying on the difference in tumor mass, density and stiffness relative to the echoes of the surrounding brain tissue. Ultrasound shows that normal brain tissue is generally a homogeneous hypoechoic area, while liquid components such as cerebrospinal fluid and tumor cystic changes are non-echoic areas (liquid dark areas), and tumors with high malignancy, cerebral falx, canopy, skull base, and choroid plexus are generally high and medium density echogenic areas, so ultrasound is easy to detect cystic tumors or cystic lesions containing tumor nodules and multiple compartments, and tumors with high malignancy; for tumors with high malignancy due to skull base Ultrasound can also detect tumors that are not detected by CT due to bony artifacts and tumors that invade the venous sinuses; ultrasound can also accurately detect the ventricles and blood vessels adjacent to the tumor, especially when recurrent gliomas encapsulate blood vessels and vascular ectopia. Intraoperative ultrasound has unique value in repositioning and determining tumor boundaries after displacement. Glioma boundaries on preoperative CT and MR T1-weighted images are often smaller than the actual boundaries, while glioma boundaries on MR T2-weighted images are larger than the actual boundaries due to the presence of edema and gliosis. In cases where brain tissue is displaced and tumor borders are confused with peritumoral edema and thus difficult to distinguish, it is difficult to determine tumor borders using navigation alone. Therefore, using the fact that tumors have different histological characteristics from normal brain tissue or even from edematous brain areas, the ultrasound echoes have different intensities, not only to show tumor tissue beyond the tumor borders shown on MR T1-weighted images, but also to It can not only show the tumor tissue beyond the tumor boundary shown by MR T1-weighted image, but also help to distinguish the tumor, edema zone and normal brain tissue shown by MR T2-weighted image, which can better indicate the actual boundary of the tumor. In cases with preoperative CT and MRI showing diffuse cerebral edema without obvious masses, intraoperative ultrasound scans can also reveal small tumors located in the center of large edematous areas. Meanwhile, autopsy studies also confirmed the reliability of ultrasound for determining tumor boundaries from the pathological anatomical perspective. In some cases, the low-grade glioma and the peritumoral edema zone appear as uniform, slightly hyperechoic areas on ultrasound, which are difficult to distinguish. The vast majority of peritumoral edema shows a hyperechoic area, while the remaining part shows a mixture of hyperechoic and hypoechoic. The peritumoral hyperechoic edema band affects the definition of the tumor boundary, and it is thought that it may be tumor necrosis with vascular damage accompanied by necrotic tissue exudation, and the exudate resembles large molecules such as plasma with high protein content and shows a hyperechoic area, thus making it difficult to distinguish from the surrounding edema band. To solve this problem, three types of images, MRT1-weighted imaging navigation, MRT2-weighted imaging navigation, and intraoperative ultrasound, were used to determine the tumor border, and biopsies were performed within the range of 2-7 mm and confirmed pathologically. in low-grade glioma ultrasound to explore the boundary. Intraoperative ultrasound for boundary determination and MRT1 imaging for boundary determination also had statistically significant differences: the match rates were 35%, 59%, and 74%, respectively, especially when preoperative MRT1 and T2-weighted images both showed that the area beyond the boundary of this tumor was normal brain tissue, ultrasound could still find that the area was still a hyperechoic area, and biopsy was performed in this area and found to be tumor tissue, which not only confirmed that intraoperative This not only confirmed the superiority of intraoperative ultrasound in determining the boundary of low-grade glioma and improved the rate of total resection, but also proposed a new idea that biopsy pathology can be certified in the few cases where even ultrasound and navigation cannot determine the tumor boundary. 3. The advantages of intraoperative ultrasound and navigation fusion BrainLab holistic ultrasound navigation system is equipped with a special ultrasound probe, small size, high frequency and good tissue resolution, which overcomes the shortcomings of the previous ultrasound equipment and navigation system, which are two independent systems and the obtained image information cannot be organically fused. By fusing and comparing the real-time intraoperative ultrasound images and the MRI images in the same plane corresponding to this ultrasound scan plane, the direction and degree of displacement of the lesion during resection can be derived. The specific value of lesion displacement is measured, and the outline of the lesion in the preoperative plan can be shifted by manual adjustment to make it coincide with the ultrasound image again, so as to perform displacement correction and microscopic total resection of the lesion, which makes up for the shortcomings of low spatial resolution, poor contrast resolution and high empirical requirements of ultrasound images; at the same time, ultrasound provides real-time images, which solves the shortcomings of the navigation image after displacement based on preoperative MRI The lack of distance error. Intraoperative ultrasound can reliably and precisely locate the boundaries of tumors with high malignancy and solid glial content after neuronavigation shift, but for a few low-grade astrocytic tumors, ultrasound can significantly improve the detection rate of tumor boundaries in cases where there is little echogenic difference between the edema zone and tumor infiltration, and ultrasound-guided biopsy of tissues where even ultrasound is difficult to identify whether they are tumors or edema zones is expected to increase the How to further solve this problem will be the focus of the next step of intraoperative ultrasound navigation.