Shigeo Sora

Simulation of and training for cerebral aneurysm clipping with 3-dimensional models.

OBJECTIVEWith improvements in endovascular techniques, fewer aneurysms are treated by surgical clipping, and those aneurysms targeted for open surgery are often complex and difficult to treat. We devised a hollow, 3-dimensional (3D) model of individual cerebral aneurysms for preoperative simulation and surgical training. The methods and initial experience with this model system are presented. METHODSThe 3D hollow aneurysm models of 3 retrospective and 8 prospective cases were made with a prototyping technique according to data from 3D computed tomographic angiograms of each patient. Commercially available titanium clips used in our routine surgery were applied, and the internal lumen was observed with an endoscope to confirm the patency of parent vessels. The actual surgery was performed later. RESULTSIn the 8 prospective cases, the clips were applied during surgery in the same direction and configuration as in the preoperative simulation. Fine adjustments were necessary in each case, and 2 patients needed additional clips to occlude the atherosclerotic aneurysmal wall. With these 3D models, it was easy for neurosurgical trainees to grasp the vascular configuration and the concept of neck occlusion. Practicing surgery with these models also improved their handling of the instruments used during aneurysm surgery, such as clips and appliers. CONCLUSIONUsing the hollow 3D models to simulate clipping preoperatively, we could treat the aneurysms confidently during live surgery. These models allow easy and concrete recognition of the 3D configuration of aneurysms and parent vessels.

Master–slave robotic platform and its feasibility study for micro‐neurosurgery

Microsurgery is a widely performed process in neurosurgery. However, it is difficult for surgeons because manipulating small and long instruments under a microscope often restricts dexterity. Hand tremors are also an issue, as the accuracy required for microsurgery is very high.

Incidence of von Hippel-Lindau disease in hemangioblastoma patients: the University of Tokyo Hospital experience from 1954-1998.

Summary.Summary.Background: Incidence of von Hippel-Lindau disease among hemangioblastomas is important clinical information affecting the management of hemangioblastomas. Studies from Western countries reported 36–40% for the incidence, but no report has been made on the Japanese population.Method: To investigate the incidence in Japan, we retrospectively analyzed all hemangioblastoma patients treated at The University of Tokyo Hospital from 1954 to 1998. By reviewing medical records and imaging studies, von Hippel-Lindau disease was diagnosed clinically following the currently suggested diagnostic criteria.Findings: There were 82 hemangioblastoma patients recorded during the period, and 14 cases (17%) were compatible with von Hippel-Lindau disease. However, when the incidence was calculated for each of the three 15-year periods, which are 1954–1968 (first), 1969–1984 (second), and 1985–1998 (third), the number increased dramatically in the later periods: 2 of 33 (6%) during the first, 4 of 26 (15%) during the second, and 8 of 22 (36%) during the third period. Such increase occurred after the introduction of whole body CT to our institution in 1981, suggesting that improvement of imaging techniques contributed to the sensitivity of diagnosis. In addition, one recent patient with multiple hemangioblastomas was found to harbor germline mutation of the VHL, thereby being diagnosed as von Hippel-Lindau disease on the basis of molecular genetics.Interpretation: The 40% incidence of von Hippel-Lindau disease in hemangioblastomas suggests that extensive screening for von Hippel-Lindau disease associated neoplasms, and probably molecular genetic examination, is indicated for all patients with hemangioblastomas, which should aim for earlier diagnosis and better management of this devastating hereditary disease.

Micro-Neurosurgical System in the Deep Surgical Field

In neurosurgery, surgeons have to perform precise manipulations with poor visibility due to the presence of blood or cerebrospinal fluid and it is particularly difficult to operate in the deep surgical field. The authors have developed a microsurgical system for neurosurgery in the deep surgical field that addresses these difficulties. The authors succeeded in suturing the carotid artery of a rat under a glass tube 120 [mm] in depth and 50 [mm] in diameter. In this paper, the authors propose the concept of robotic-assisted micro-neurosurgery. The design and the system are presented. Furthermore, the performance of the system and in-vivo experiments on rats are also reported.

Robust Visual Tracking of Robotic Forceps Under a Microscope Using Kinematic Data Fusion

Forceps tracking is an important element of high-level surgical assistance such as visual servoing and motion analysis. This paper describes a robust, efficient tracking algorithm capable of estimating the forceps tip position in an image space by fusing visual tracking data with kinematic information. In visual tracking, the full-state parameters of forceps are estimated using the projective contour models of a 3-D CAD model of the forceps. The likelihood of the contour model is measured using the distance transformation to enable fast calculation, and the particle filter estimates the full state of the forceps. For more robust tracking, the result data obtained from visual tracking are combined with kinematic data that are obtained by forward kinematics and hand-eye transformation. The fusion of visual and kinematic tracking data is performed using an adaptive Kalman filter, and the fused tracking enables the reinitialization of visual tracking parameters when a failure occurs. Experimental results indicate that the proposed method is accurate and robust to image noise, and forceps tracking was successfully carried out even when the forceps was out of view.

Master manipulator with higher operability designed for micro neuro surgical system

The master and slave surgical assistant systems have been studied actively. However, regarding the master system, the manipulator should be designed for each surgical field because the target workspace and precision are different. Furthermore, operability is important for safety reasons. Therefore, the authors analyzed the motion of surgeon first and then developed a master manipulator suitable for the operation of micro neuro surgery. Some experiments were conducted to evaluate the control method and show the effectiveness of the proposed manipulator control method.

Assessing Microneurosurgical Skill with Medico-Engineering Technology

OBJECTIVES Most methods currently used to assess surgical skill are rather subjective or not adequate for microneurosurgery. Objective and quantitative microneurosurgical skill assessment systems that are capable of accurate measurements are necessary for the further development of microneurosurgery. METHODS Infrared optical motion tracking markers, an inertial measurement unit, and strain gauges were mounted on tweezers to measure many parameters related to instrument manipulation. We then recorded the activity of 23 neurosurgeons. The task completion time, tool path, and needle-gripping force were evaluated for three stitches made in an anastomosis of 0.7-mm artificial blood vessels. Videos of the activity were evaluated by three blinded expert surgeons. RESULTS Surgeons who had recently done many bypass procedures demonstrated better skills. These skilled surgeons performed the anastomosis with in a shorter time, with a shorter tool path, and with a lesser force when extracting the needle. CONCLUSIONS These results show the potential contribution of the system to microsurgical skill assessment. Quantitative and detailed analysis of surgical tasks helps surgeons better understand the key features of the required skills.

Prognosis of Tinnitus After Acoustic Neuroma Surgery—Surgical Management of Postoperative Tinnitus

OBJECTIVE Tinnitus is a bothersome symptom for patients with acoustic neuroma. We studied the possibility of surgical control of postoperative tinnitus associated with acoustic neuroma. METHODS Postoperative changes and prognosis of tinnitus were studied in 367 patients treated surgically via a lateral suboccipital retrosigmoid approach. RESULTS Postoperative prognosis of tinnitus was as follows: resolved in 20%, improved in 22%, unchanged in 35%, changed in 10%, and worsened in 14% of 290 patients who had preoperative tinnitus, and no tinnitus in 78% and appeared in 22% of 77 patients without preoperative tinnitus. Prognosis of postoperative tinnitus was influenced by age, tumor size, preoperative hearing acuity, types of preoperative hearing disturbance, and conditions of the cochlear nerve after tumor resection. Worse prognosis of postoperative tinnitus in the preoperative tinnitus group was found in younger patients, smaller tumor size, better preoperative hearing function, and normal or retrocochlear type of hearing disturbance. Regarding the conditions of the cochlear nerve after tumor resection, prognosis of tinnitus was significantly worse in the group of anatomically preserved cochlear nerve without useful hearing than in the group of cut cochlear nerve. CONCLUSIONS Deciding whether to cut the cochlear nerve during acoustic neuroma surgery by referring to a flowchart, we proposed in cases where hearing preservation is not intended or judged less possible contributes to controlling postoperative tinnitus. However, regardless of whether the cochlear nerve was cut intraoperatively, tinnitus remained unchanged in 37% of patients, suggesting that their tinnitus originates in the brainstem or post-brainstem pathways before surgery, and it is considered difficult to control postoperative tinnitus in these cases.

Microsurgical skill assessment: Toward skill-based surgical robotic control

A surgical skill assessment system was developed to quantify microsurgical skills. Infrared optical makers, an inertial measurement unit, and strain gauges were mounted on tweezers to record surgical tasks. In preliminary experiments, the tool tip trajectory, acceleration, and applied force were measured and microsurgery videos were evaluated by three expert surgeons. The preliminary results indicated the feasibility of the system by showing the significant difference between unskilled and skilled surgeons.

Is an Acoustic Neuroma an Epiarachnoid or Subarachnoid Tumor

BACKGROUND:There are arguments about whether acoustic neuromas are epiarachnoid or subarachnoid tumors. OBJECTIVE:To retrospectively examine 118 consecutively operated-on patients with acoustic neuromas to clarify this point. METHODS:Epiarachnoid tumors are defined by the absence of an arachnoid membrane on the tumor surface after moving the arachnoid fold (double layers of the arachnoid membrane) toward the brainstem. In contrast, subarachnoid tumors are characterized by the arachnoid membrane remaining on the tumor surface after moving the arachnoid fold. Based on this hypothesis, we used intraoperative views and light and electron microscopy to confirm the existence of an arachnoid membrane after the arachnoid fold had been moved. RESULTS:The tumors were clearly judged to be subarachnoid tumors in 86 of 118 patients (73%), an epiarachnoid tumor in 2 patients (2%), whereas a clear judgment was difficult to make in the remaining 30 patients (25%). CONCLUSION:The majority of acoustic neuromas are subarachnoid tumors, with epiarachnoid tumors being considerably less common.