Collision of pituitary neuroendocrine tumor and anterior clinoid meningioma treated with a two-stage minimally invasive surgical strategy: illustrative case.

BACKGROUND: The locations of pituitary neuroendocrine tumor (PitNET) and anterior clinoid meningioma (ACM) appear to be very close but essentially different, as the former is inside the sella turcica while the latter is in the intradural space. A collision tumor thus requires a specific treatment strategy but has been rarely reported. OBSERVATIONS: A 77-year-old woman presented with progressive visual impairment due to significant compression of the optic apparatus by a collision of PitNET and ACM. With a minimally invasive two-stage therapeutic strategy, the ACM was first resected using an endoscopic mini-pterional approach, then the PitNET was removed with an endoscopic transnasal approach 8 weeks later, leading to significant improvement in visual function. The authors' literature search identified only 2 documented cases of a similar collision. LESSONS: This case underscores the complexity of the decision-making process in the management of collision tumors and suggests the potential benefit of staged minimally invasive surgical interventions in preserving visual function. Further accumulation of cases is warranted for refining the treatment strategy. https://thejns.org/doi/10.3171/CASE24240.

[Preoperative 3D Microvascular Decompression Simulation].

Preoperative surgical simulation via three-dimensional fusion computer graphics models have been widely accepted as a legitimate means of securing the diagnosis and treatment effectiveness of neurovascular compression. The authors discussed three factors of surgical simulation as being 1. Knowing the anatomical relationship, 2. Knowing the desirable end result of surgical intervention, and 3. Knowing how to design surgical interventions to achieve such desirable end results. Satisfying each factor requires distinct functionality from the software used in the surgical simulation. As per the imaging study used to construct the multimodal computer graphic models, CT scan and MR are usually sufficient, although renal function-permitting contrast enhancement can be a feasible option for depicting minute vessels in particular. There are three major steps in building three-dimensional fusion computer graphics models:1. Image interpretation, 2. co-registration, and 3. Segmentation. Each step comprises an essential part that must be handled with care. The segmentation step is where rigorous technological advancement takes place, although classical techniques, such as the seeded region growing method or the multi-threshold method, are still practically important. Regarding surgical simulation after three-dimensional model construction, technical challenges concerning large deformations should be recognized to ensure non-nonsense surgical simulation.

Clinical trial links oncolytic immunoactivation to survival in glioblastoma.

Immunotherapy failures can result from the highly suppressive tumour microenvironment that characterizes aggressive forms of cancer such as recurrent glioblastoma (rGBM)1,2. Here we report the results of a first-in-human phase I trial in 41 patients with rGBM who were injected with CAN-3110-an oncolytic herpes virus (oHSV)3. In contrast to other clinical oHSVs, CAN-3110 retains the viral neurovirulence ICP34.5 gene transcribed by a nestin promoter; nestin is overexpressed in GBM and other invasive tumours, but not in the adult brain or healthy differentiated tissue4. These modifications confer CAN-3110 with preferential tumour replication. No dose-limiting toxicities were encountered. Positive HSV1 serology was significantly associated with both improved survival and clearance of CAN-3110 from injected tumours. Survival after treatment, particularly in individuals seropositive for HSV1, was significantly associated with (1) changes in tumour/PBMC T cell counts and clonal diversity, (2) peripheral expansion/contraction of specific T cell clonotypes; and (3) tumour transcriptomic signatures of immune activation. These results provide human validation that intralesional oHSV treatment enhances anticancer immune responses even in immunosuppressive tumour microenvironments, particularly in individuals with cognate serology to the injected virus. This provides a biological rationale for use of this oncolytic modality in cancers that are otherwise unresponsive to immunotherapy (ClinicalTrials.gov: NCT03152318 ).

Possible Association between Recurrent Chronic Subdural Hematoma and Dural Arteriovenous Fistula: A Case Report with Three-dimensional Fusion Images.

Several studies have reported the coexistence of chronic subdural hematoma (CSDH) and dural arteriovenous fistula (DAVF); however, the association between these two entities remains unknown. A case of coexisting CSDH and DAVF that was successfully treated with burr hole surgery and middle meningeal artery (MMA) embolization is reported herein. We visualized the positional relationship between CSDH and DAVF by fusion three-dimensional computer graphics images reconstructed from multimodal imaging studies, which revealed that the shunt point of the DAVF was far from the burr hole and was in contact with the CSDH membrane at the center of the CSDH. Additionally, the chronological development of CSDH in the presence of DAVF and the complete disappearance of both DAVF and CSDH after MMA embolization were also demonstrated. This study suggests a possible association between recurrent CSDH and DAVF.

Revisitation of imaging features of skull base chondrosarcoma in comparison to chordoma.

PURPOSE: Pre-surgical diagnosis of skull base chondrosarcoma (SBC) is often challenging due to the resemblance to chordoma. The goal of this study was to develop an optimal method for predicting SBC diagnosis. METHODS: This retrospective study included patients with histologically diagnosed SBC and skull base chordoma. Their clinical and radiologic features were compared, and the predictive factors of SBC were examined. RESULTS: Forty-one patients with SBC and 41 with chordoma were included. Most SBCs exhibited hypointensity (25, 64.1%) or isointensity (12, 30.8%) on T1-weighted images, and hyperintensity (34, 87.1%) or mixed intensity (5, 12.8%) on T2-weighted images. MRI contrast enhancement was usually avid or fair (89.7%) with "arabesque"-like pattern (41.0%). The lateral/paramidline location was more common in SBC than in chordoma (85.4% vs. 9.8%; P < 0.01), while midline SBCs (14.6%) were also possible. Multivariate analysis demonstrated that higher apparent diffusion coefficient (ADC) value (unit odds ratio 1.01; 95% confidence interval 1.00-1.02; P < 0.01) was associated with an SBC diagnosis. An ADC value of ≥ 1750 × 10-6 mm2/s demonstrated a strong association with an SBC diagnosis (odds ratio 5.89 × 102; 95% confidence interval 51.0-6.80 × 103; P < 0.01) and yielded a sensitivity of 93.9%, specificity of 97.4%, positive predictive value of 96.9%, and negative predictive value of 95.0%. CONCLUSION: The ADC-based method is helpful in distinguishing SBC from chordoma and readily applicable in clinical practice. The prediction accuracy increases when other characteristics of SBC, such as non-midline location and arabesque-like enhancement, are considered together.

Threshold field painting saves the time for segmentation of minute arteries.

PURPOSE: It is often time-consuming to segment fine structures, such as the cerebral arteries from magnetic resonance imaging (MRI). Moreover, extracting anatomically abnormal structures is generally difficult. The segmentation workflow called threshold field painting was tested for its feasibility in morbid minute artery segmentation with special emphasis on time efficiency. METHODS: Seven patients with meningioma with ten-sided feeding arteries (n = 10) originating from middle meningeal arteries (MMA) were investigated by three experts of the conventional method for segmentation. The MRI time-of-flight sequence was utilized for the segmentation of each procedure. The tasks were accomplished using both the conventional method and the proposed method in random order. The task completion time and usability score were analyzed using the Wilcoxon signed-rank test. RESULTS: Except for one examinee (P = 0.06), the completion time significantly decreased (both P < 0.01) with the use of the proposed method. The average task completion time among the three examinees for the conventional method was 2.8 times longer than that for the proposed method. The usability score was generally in favor of the proposed method. CONCLUSION: The normally nonexistent minute arteries, such as the MMA feeders, were deemed more efficiently segmented with the proposed method than with the conventional method. While automatic segmentation might be the ultimate solution, our semiautomatic method incorporating expert knowledge is expected to work as the practical solution.

Quantitative imaging of apoptosis following oncolytic virotherapy by magnetic resonance fingerprinting aided by deep learning.

Non-invasive imaging methods for detecting intratumoural viral spread and host responses to oncolytic virotherapy are either slow, lack specificity or require the use of radioactive or metal-based contrast agents. Here we show that in mice with glioblastoma multiforme, the early apoptotic responses to oncolytic virotherapy (characterized by decreased cytosolic pH and reduced protein synthesis) can be rapidly detected via chemical-exchange-saturation-transfer magnetic resonance fingerprinting (CEST-MRF) aided by deep learning. By leveraging a deep neural network trained with simulated magnetic resonance fingerprints, CEST-MRF can generate quantitative maps of intratumoural pH and of protein and lipid concentrations by selectively labelling the exchangeable amide protons of endogenous proteins and the exchangeable macromolecule protons of lipids, without requiring exogenous contrast agents. We also show that in a healthy volunteer, CEST-MRF yielded molecular parameters that are in good agreement with values from the literature. Deep-learning-aided CEST-MRF may also be amenable to the characterization of host responses to other cancer therapies and to the detection of cardiac and neurological pathologies.

Simulated accuracy assessment of small footprint body-mounted probe alignment device for MRI-guided cryotherapy of abdominal lesions.

PURPOSE: Magnetic resonance imaging (MRI)-guided percutaneous cryotherapy of abdominal lesions, an established procedure, uses MRI to guide and monitor the cryoablation of lesions. Methods to precisely guide cryotherapy probes with a minimum amount of trial-and-error are yet to be established. To aid physicians in attaining precise probe alignment without trial-and-error, a body-mounted motorized cryotherapy-probe alignment device (BMCPAD) with motion compensation was clinically tested in this study. The study also compared the contribution of body motion and organ motion compensation to the guidance accuracy of a body-mounted probe alignment device. METHODS: The accuracy of guidance using the BMCPAD was prospectively measured during MRI-guided percutaneous cryotherapies before insertion of the probes. Clinical parameters including patient age, types of anesthesia, depths of the target, and organ sites of target were collected. By using MR images of the target organs and fiducial markers embedded in the BMCPAD, we retrospectively simulated the guidance accuracy with body motion compensation, organ motion compensation, and no compensation. The collected data were analyzed to test the impact of motion compensation on the guidance accuracy. RESULTS: Thirty-seven physical guidance of probes were prospectively recorded for sixteen completed cases. The accuracy of physical guidance using the BMCPAD was 13.4 ± 11.1 mm. The simulated accuracy of guidance with body motion compensation, organ motion compensation, and no compensation was 2.4 ± 2.9 mm, 2.2 ± 1.6 mm, and 3.5 ± 2.9 mm, respectively. Data analysis revealed that the body motion compensation and organ motion compensation individually impacted the improvement in the accuracy of simulated guidance. Moreover, the difference in the accuracy of guidance either by body motion compensation or organ motion compensation was not statistically significant. The major clinical parameters impacting the accuracy of guidance were the body and organ motions. Patient age, types of anesthesia, depths of the target, and organ sites of target did not influence the accuracy of guidance using BMCPAD. The magnitude of body surface movement and organ movement exhibited mutual statistical correlation. CONCLUSIONS: The BMCPAD demonstrated guidance accuracy comparable to that of previously reported devices for CT-guided procedures. The analysis using simulated motion compensation revealed that body motion compensation and organ motion compensation individually impact the improvement in the accuracy of device-guided cryotherapy probe alignment. Considering the correlation between body and organ movements, we also determined that body motion compensation using the ring fiducial markers in the BMCPAD can be solely used to address both body and organ motions in MRI-guided cryotherapy.

Continuum Robot With Follow-the-Leader Motion for Endoscopic Third Ventriculostomy and Tumor Biopsy.

BACKGROUND: In a combined endoscopic third ventriculostomy (ETV) and endoscopic tumor biopsy (ETB) procedure, an optimal tool trajectory is mandatory to minimize trauma to surrounding cerebral tissue. OBJECTIVE: This paper presents wire-driven multi-section robot with push-pull wire. The robot is tested to attain follow-the-leader (FTL) motion to place surgical instruments through narrow passages while minimizing the trauma to tissues. METHODS: A wire-driven continuum robot with six sub-sections was developed and its kinematic model was proposed to achieve FTL motion. An accuracy test to assess the robot's ability to attain FTL motion along a set of elementary curved trajectory was performed. We also used hydrocephalus ventricular model created from human subject data to generate five ETV/ETB trajectories and conducted a study assessing the accuracy of the FTL motion along these clinically desirable trajectories. RESULTS: In the test with elementary curved paths, the maximal deviation of the robot was increased from 0.47 mm at 30 ° turn to 1.78 mm at 180 ° in a simple C-shaped curve. S-shaped FTL motion had lesser deviation ranging from 0.16 to 0.18 mm. In the phantom study, the greatest tip deviation was 1.45 mm, and the greatest path deviation was 1.23 mm. CONCLUSION: We present the application of a continuum robot with FTL motion to perform a combined ETV/ETB procedure. The validation study using human subject data indicated that the accuracy of FTL motion is relatively high. The study indicated that FTL motion may be useful tool for combined ETV and ETB.

Transposition of the Culprit Artery Passing Between the Facial Nerve and Auditory Nerve in Microvascular Decompression Surgery for Hemifacial Spasm.

BACKGROUND: Decompression of the culprit artery causing hemifacial spasm (HFS), which passes between the facial nerve (cranial nerve [CN] VII) and the auditory nerve (CN VIII), can be difficult, especially if the artery compresses CN VII right after passing between the 2 nerves. Perforators or small arteries branching from near the compression site to adjacent structures can hinder the decompression process because such vessels can anchor the passing condition. The effect of such perforators or small arteries on the decompression process in such cases was investigated. METHODS: The culprit artery passed between any part of CN VII and VIII in 59 of 396 consecutive patients with HFS who underwent microvascular decompression. The culprit artery compressed CN VII right after passing between the 2 nerves in 22 of the 59 cases. Direction of the perforators or small arteries from near the compression site and direction of decompression of the culprit artery were analyzed in these 22 cases. RESULTS: Perforators or small arteries were observed in 20 cases, predominantly in the medial direction. The culprit artery was mobilized toward the petrous bone direction in most cases. No clear relationship was found between the 2 factors. CONCLUSIONS: Variation of curvature or tortuosity of the culprit artery and length of perforators or small branches may also have affected the decompression process and the directions. Adequate dissection near the compression site to obtain maximum mobilization of the culprit artery is necessary to achieve successful decompression in such cases.

Acute Glaucoma Attack Following Microvascular Decompression Surgery for Trigeminal Neuralgia.

Microvascular decompression (MVD) is widely accepted as an effective surgical method to treat trigeminal neuralgia (TN), but the risks of morbidity and mortality must be considered. We experienced a case of acute angle-closure glaucoma attack following MVD for TN in an elderly patient, considered to be caused by lateral positioning during and after the surgery. A 79-year-old female underwent MVD for right TN in the left lateral decubitus position, and TN disappeared after the surgery. Postoperatively, the patient tended to maintain the left lateral decubitus position to prevent wound contact with the pillow, even after ambulation. Two days after the surgery, she complained of persistent left ocular pain with visual disturbance. The left pupil was dilated with only light perception, and the intraocular pressure (IOP) was 44 mmHg. Acute angle-closure glaucoma attack was diagnosed. After drip infusion of mannitol, emergent laser iridotomy was performed. The corrected visual acuity recovered with normalization of IOP (14 mmHg). The subsequent clinical course was uneventful and she was discharged from our hospital. The left lateral positioning during and after the surgery was considered to have contributed to increase IOP of the eye on the dependent side, which resulted in acute angle-closure glaucoma attack. The potential pathology is difficult to assess preoperatively, but patient management should always consider the increased possibility of this condition with age.

Microsurgery Simulator of Cerebral Aneurysm Clipping with Interactive Cerebral Deformation Featuring a Virtual Arachnoid.

BACKGROUND: A virtual reality simulator for aneurysmal clipping surgery is an attractive research target for neurosurgeons. Brain deformation is one of the most important functionalities necessary for an accurate clipping simulator and is vastly affected by the status of the supporting tissue, such as the arachnoid membrane. However, no virtual reality simulator implementing the supporting tissue of the brain has yet been developed. OBJECTIVE: To develop a virtual reality clipping simulator possessing interactive brain deforming capability closely dependent on arachnoid dissection and apply it to clinical cases. METHODS: Three-dimensional computer graphics models of cerebral tissue and surrounding structures were extracted from medical images. We developed a new method for modifiable cerebral tissue complex deformation by incorporating a nonmedical image-derived virtual arachnoid/trabecula in a process called multitissue integrated interactive deformation (MTIID). MTIID made it possible for cerebral tissue complexes to selectively deform at the site of dissection. Simulations for 8 cases of actual clipping surgery were performed before surgery and evaluated for their usefulness in surgical approach planning. RESULTS: Preoperatively, each operative field was precisely reproduced and visualized with the virtual brain retraction defined by users. The clear visualization of the optimal approach to treating the aneurysm via an appropriate arachnoid incision was possible with MTIID. CONCLUSION: A virtual clipping simulator mainly focusing on supporting tissues and less on physical properties seemed to be useful in the surgical simulation of cerebral aneurysm clipping. To our knowledge, this article is the first to report brain deformation based on supporting tissues.

Supratentorial acute subdural haematoma during microvascular decompression surgery: report of three cases.

Supratentoiral haemorrhage during posterior fossa surgery is very rare. Authors report three cases of acute subdural haematoma occurred during microvascular decompression (MVD). Bleeding was observed in the suboccipital surgical area during operation but the origin of the bleeding was not confirmed intraoperatively in all cases. Decompression procedure was completed and immediate postoperative computed tomography revealed supratentorial subdural haematoma. This complication was observed during MVD in healthy young patients with hemifacial spasm in our cases. Flexion of the head with reduction of cerebrospinal fluid may have induced rotational movement of the cerebrum resulting in rupture of bridging veins, but no definitive mechanism that fulfils the clinical characteristics was clearly determined.

Neurosurgical Virtual Reality Simulation for Brain Tumor Using High-definition Computer Graphics: A Review of the Literature.

Simulation and planning of surgery using a virtual reality model is becoming common with advances in computer technology. In this study, we conducted a literature search to find trends in virtual simulation of surgery for brain tumors. A MEDLINE search for "neurosurgery AND (simulation OR virtual reality)" retrieved a total of 1,298 articles published in the past 10 years. After eliminating studies designed solely for education and training purposes, 28 articles about the clinical application remained. The finding that the vast majority of the articles were about education and training rather than clinical applications suggests that several issues need be addressed for clinical application of surgical simulation. In addition, 10 of the 28 articles were from Japanese groups. In general, the 28 articles demonstrated clinical benefits of virtual surgical simulation. Simulation was particularly useful in better understanding complicated spatial relations of anatomical landmarks and in examining surgical approaches. In some studies, Virtual reality models were used on either surgical navigation system or augmented reality technology, which projects virtual reality images onto the operating field. Reported problems were difficulties in standardized, objective evaluation of surgical simulation systems; inability to respond to tissue deformation caused by surgical maneuvers; absence of the system functionality to reflect features of tissue (e.g., hardness and adhesion); and many problems with image processing. The amount of description about image processing tended to be insufficient, indicating that the level of evidence, risk of bias, precision, and reproducibility need to be addressed for further advances and ultimately for full clinical application.

Intelligent control of neurosurgical robot MM-3 using dynamic motion scaling.

OBJECTIVE Advanced and intelligent robotic control is necessary for neurosurgical robots, which require great accuracy and precision. In this article, the authors propose methods for dynamically and automatically controlling the motion-scaling ratio of a master-slave neurosurgical robotic system to reduce the task completion time. METHODS Three dynamic motion-scaling modes were proposed and compared with the conventional fixed motion-scaling mode. These 3 modes were defined as follows: 1) the distance between a target point and the tip of the slave manipulator, 2) the distance between the tips of the slave manipulators, and 3) the velocity of the master manipulator. Five test subjects, 2 of whom were neurosurgeons, sutured 0.3-mm artificial blood vessels using the MM-3 neurosurgical robot in each mode. RESULTS The task time, total path length, and helpfulness score were evaluated. Although no statistically significant differences were observed, the mode using the distance between the tips of the slave manipulators improves the suturing performance. CONCLUSIONS Dynamic motion scaling has great potential for the intelligent and accurate control of neurosurgical robots.

Usefulness of high-resolution 3D multifusion medical imaging for preoperative planning in patients with posterior fossa hemangioblastoma: technical note.

Successful resection of hemangioblastoma depends on preoperative assessment of the precise locations of feeding arteries and draining veins. Simultaneous 3D visualization of feeding arteries, draining veins, and surrounding structures is needed. The present study evaluated the usefulness of high-resolution 3D multifusion medical imaging (hr-3DMMI) for preoperative planning of hemangioblastoma. The hr-3DMMI combined MRI, MR angiography, thin-slice CT, and 3D rotated angiography. Surface rendering was mainly used for the creation of hr-3DMMI using multiple thresholds to create 3D models, and processing took approximately 3-5 hours. This hr-3DMMI technique was used in 5 patients for preoperative planning and the imaging findings were compared with the operative findings. Hr-3DMMI could simulate the whole 3D tumor as a unique sphere and show the precise penetration points of both feeding arteries and draining veins with the same spatial relationships as the original tumor. All feeding arteries and draining veins were found intraoperatively at the same position as estimated preoperatively, and were occluded as planned preoperatively. This hr-3DMMI technique could demonstrate the precise locations of feeding arteries and draining veins preoperatively and estimate the appropriate route for resection of the tumor. Hr-3DMMI is expected to be a very useful support tool for surgery of hemangioblastoma.

Fibrin glue injection into the hematoma cavity for refractory chronic subdural hematoma: A case report.

BACKGROUND: Repeat burr hole irrigation and drainage has been effective in most cases of recurrent chronic subdural hematoma (CSDH), however, refractory cases require further procedures or other interventions. CASE DESCRIPTION: An 85-year-old male presented with left CSDH, which recurred five times. The hematoma was irrigated and drained through a left frontal burr hole during the first to third surgery and through a left parietal burr hole during the fourth and fifth surgery. The hematoma had no septation and was well-evacuated during each surgery. Antiplatelet therapy for preventing ischemic heart disease was stopped after the second surgery, the hematoma cavity was irrigated with artificial cerebrospinal fluid at the third surgery, and the direction of the drainage tube was changed to reduce the postoperative subdural air collection at the fourth surgery. However, none of these interventions was effective. He was successfully treated by fibrin glue injection into the hematoma cavity after the fifth surgery. CONCLUSION: This procedure may be effective for refractory CSDH in elderly patients.

Safety of microvascular decompression for elderly patients with trigeminal neuralgia.

OBJECTIVE: The present study compared the safety and efficacy of microvascular decompression (MVD) in groups of elderly patients and non-elderly patients with medically refractory trigeminal neuralgia (TN) and collected detailed perioperative data. METHODS: Retrospective analysis of clinical data was performed in 99 patients who underwent MVD from May 2012 to June 2015. The outcome data from 27 MVD operations for 27 patients aged 70-80 years (mean 74.6 years) were compared with 72 MVD operations with 72 patients aged 25-69 years (mean 55.7 years). Preoperative comorbidities were recorded and postoperative worsening comorbidities and non-neurological complications were evaluated at discharge. Efficacy of the surgery and neurological complications were evaluated in July 2015. RESULTS: No decrease in activity of daily living was found in any patient. Complete pain relief without medication was achieved in 77.8% and partial pain relief in 14.8% in the elderly group, and 83.3% and 9.7%, respectively, in the non-elderly group (p=0.750). Permanent neurological complication was not observed in the elderly group, whereas Vth nerve and VIIIth nerve complications were observed in the non-elderly group. Rates of preoperative multiple comorbidities and of cardiovascular comorbidity were significantly higher in the elderly group (p<0.01). Worsening comorbidity and new pathology at discharge were mainly hypertension in both groups, but glaucoma attack and asthma attack were observed in the elderly group. All pathologies were successfully managed. CONCLUSIONS: MVD for elderly patients with TN can be achieved safely with careful perioperative management. Information of comorbidity should be shared with all staff involved in the treatment, who should work as a team to avoid worsening comorbidity. The possibility of unpredictable events in the elderly patients should always be considered.

Development of a new compact intraoperative magnetic resonance imaging system: concept and initial experience.

BACKGROUND: Magnetic resonance imaging (MRI) during surgery has been shown to improve surgical outcomes, but the current intraoperative MRI systems are too large to install in standard operating suites. Although 1 compact system is available, its imaging quality is not ideal. OBJECTIVE: We developed a new compact intraoperative MRI system and evaluated its use for safety and efficacy. METHODS: This new system has a magnetic gantry: a permanent magnet of 0.23 T and an interpolar distance of 32 cm. The gantry system weighs 2.8 tons and the 5-G line is within the circle of 2.6 m. We created a new field-of-view head coil and a canopy-style radiofrequency shield for this system. A clinical trial was initiated, and the system has been used in 44 patients. RESULTS: This system is significantly smaller than previous intraoperative MRI systems. High-quality T2 images could discriminate tumor from normal brain tissue and identify anatomic landmarks for accurate surgery. The average imaging time was 45.5 minutes, and no clinical complications or MRI system failures occurred. Floating organisms or particles were minimal (1/200 L maximum). CONCLUSION: This intraoperative, compact, low-magnetic-field MRI system can be installed in standard operating suites to provide relatively high-quality images without sacrificing safety. We believe that such a system facilitates the introduction of the intraoperative MRI.