Since the late 1990s, high field strength iMRI systems have been used in clinical practice. There are two main types of high field strength iMRI, one is magnet fixed, which has a low utilization rate and has the disadvantages of a complicated and time-consuming moving process, and the other is magnet mobile , which does not require moving the patient and has a better safety profile. We use an iMRI system with a dual-chamber design of moving magnets, and the results show that no intraoperative MRI-related safety incidents have occurred, and routine iMRI scans can be performed in the diagnostic room during the procedure. The application of a large-aperture magnet (70 cm) allows the procedure to be performed in the flat, prone and lateral positions. Chordoma is a slow-growing tumor with an incidence of 0. 2/100,000 to 0. 5/100,000, accounting for 0. 1% to 0. 7% of intracranial tumors, and can develop at any age, but most patients show clinical symptoms at 30 to 50 years of age, with a survival time of 12 to 41 months. The present study suggests that chordoma originates from residual tissue of the notochord. Tumors of the spinal cord at the base of the skull are usually located at or near the midline, commonly in the saddle, paracranial, nasopharynx, slope, foramen magnum, and C1, often surrounded by bone tissue. Due to the slow growth of slope chordoma, early symptoms are insidious and mainly start with symptoms of multiple groups of brain nerve damage. Transoral or pterygoid sinus skull base tumor surgery is the area where iMRI is most used in neurosurgery other than functional areas and deep tumors. Neuroendoscopic techniques and iMRI techniques are two revolutionary techniques in the surgical treatment of chordoma, and we have carried out work on the integration of these two techniques. The current range of neuroendoscopic applications for skull base chordoma cases can include: transsphenoidal approach for resection of tumors growing from the mid-superior slope to the anterior-middle skull base, and transoral approach to accommodate tumors growing from the downward slope [MSOffice2] and the greater occipital foramen area. Because of the deep field and small field of view in the transsphenoidal sinus and transoral surgery, there are blind spots in the intraoperative application of the microscope, so neuroendoscopy is increasingly used in transsphenoidal sinus and transoral resection of chordoma; neuroendoscopy can solve the dead angle of the microscopic surgical field, and extending the 0° or 45° neuroendoscope into the saddle during surgery can clearly show the two sides of the saddle, the dorsal saddle and the subsaddle septum structures, as well as the lateral and inferior walls of the pterygoid sinus. Tumors can also be visualized in the lateral and inferior walls of the pterygoid sinus, and even in the posterior part of the sloping bone that protrudes into the skull. Chordoma can also invade the rocky bone from around the internal carotid artery of the rocky bone segment, and the endoscope can also cross the internal carotid artery to visualize and remove this part of the tumor. The advantages of endoscopic surgery for chordoma surgery outweigh the advantages it represents for pituitary tumor surgery. However, endoscopy still cannot visualize the portion of the tumor that is obscured by the descending dura or skull base bone, or by the cavernous sinus and internal carotid artery of the rocky bone segment. iMRI systems solve this problem precisely by objectively guiding the surgery intraoperatively and evaluating its outcome. However, the integration of neuroendoscopy with iMRI and navigation technology has not yet been much experienced in China. Our group has explored some paths and specifications for the integration of these two technologies through 23 cases of surgery, and has gained some experience. Complete resection was achieved in 17 of the 23 cases of chordoma tumors. The rate of complete tumor resection increased from 34.8% (8/23) to 73.9% (17/23), demonstrating that this technique is indeed very useful for detecting residual tumors during surgery and guiding the next step, and can lead to significantly improved surgical outcomes. It should be noted that chordomas invade the skull base bone more extensively, and larger chordomas are certainly not truly total resections in the current surgical approach, even if they are total on imaging. However, an increased degree of chordoma resection is clearly associated with a longer survival time. However, not all scans with residual tumor require intraoperative re-excision. Our group found just a little blood and fluid in the space that was partially obscured by the dura, which did not need to be forcibly removed. Many of the surrounding mucosa will be edematous and thickened with abnormal signals due to the tumor. In addition, there are cases where the cavernous sinus will be swollen during surgery, and these should not be mistaken for residual tumors. There are also residual tumors that cannot be completely removed even if they are found. The surgeon needs to choose between removing the residual tumor and ensuring surgical safety, which is higher than total removal of the tumor. Intraoperative scanning itself does not increase the risk of surgery, but further surgical resection of the participating tumor will undoubtedly increase the risk of surgery. The combined use of iMRI and neurological navigation system is a true “real-time navigation” in 20 of our patients. When the iMRI scan suggests residual tumor, the navigation system can update the navigation image in real time based on the new iMRI scan data and mark the residual tumor on the navigation image, so that the surgeon can find the residual tumor and remove it more quickly and accurately, which greatly improves the efficiency of surgery. In contrast to endoscopic transnasal resection of pituitary tumors, we have used navigation and iMRI more extensively in endoscopic transnasal transoral resection of chordomas because surgery for chordomas and pituitary tumors differs in many ways: (1) the center of growth of chordomas can be located anywhere on the full slope and in the pterygoid sinus, even slightly off the midline, such as with the center located at the tip of the rock, so navigation positioning is more necessary to guide the extent of exposure; (2 (2) Even though chordomas are close to the surface mucosa or bone, most of them are located behind bone, and some are even located behind thickened bone, so the process of removing the tumor is often accompanied by the process of grinding away the bone, and from the beginning to the end, the guidance of navigation and iMRI to verify the extent of resection and re-mark the residual tumor are very helpful for the smooth operation; (3) Chordomas are close to the bilateral internal carotid arteries, and some even break through the dura and invade the dura. The use of iMRI and navigation, together with endoscopic visualization of local structures, is currently the best way to reduce such injuries; (4) intraoperative residual pituitary tumors are mainly located behind the descending saddle septum [MSOffice3] or in the cavernous sinus or within the cavernous sinus, whereas residuals in chordoma are more widely distributed and can be located between the bone and dura, between the bones of the skull base, and in the dead space of the sphenoid sinus, with significantly higher detection rates of residual tumors than in pituitary tumor surgery; (5) endoscopy combined with navigation and intraoperative imaging is more practical in chordoma surgery, and angled ones can easily bring the operative field to corners where the microscope is far from a direct view. In summary, the application of a mobile magnet dual-chamber high-field iMRI system during endoscopic surgery for transsphenoidal or transoral chordoma improves the safety and effectiveness of the procedure. The combined use of neuroendoscopy and/or neuronavigation systems for different cases has improved the outcome of transsphenoidal or transoral chordoma surgery. Nevertheless, a larger prospective randomized controlled trial is still needed to verify the true clinical value of the system. The patient was a 54-year-old woman diagnosed with a giant slope chordoma. Preoperative T2WI sagittal and coronal images showed a giant chordoma in the middle and lower slope with posterior compression of the basilar artery and anterior brainstem and loss of the basilar artery pool (the arrow shows the internal carotid artery); T2WI sagittal and coronal images obtained from the first intraoperative magnetic resonance (iMRI) scan showed complete resection of the pharyngeal tumor with posterior slope The sagittal and coronal images obtained from the second iMRI scan showed that the tumor behind the slope had been completely resected, and the dura mater (shown by arrow) and the basal pool in front of the brainstem could be clearly distinguished, and there was a residual tumor in the upper left side. The placed bone wax (shown by arrow) and the full length of the basilar artery, basilar pool and retracted dura mater