Takehiko Konno

Development of Three-Dimensional Hollow Elastic Model for Cerebral Aneurysm Clipping Simulation Enabling Rapid and Low Cost Prototyping

OBJECTIVE We developed a method for fabricating a three-dimensional hollow and elastic aneurysm model useful for surgical simulation and surgical training. In this article, we explain the hollow elastic model prototyping method and report on the effects of applying it to presurgical simulation and surgical training. METHODS A three-dimensional printer using acrylonitrile-butadiene-styrene as a modeling material was used to produce a vessel model. The prototype was then coated with liquid silicone. After the silicone had hardened, the acrylonitrile-butadiene-styrene was melted with xylene and removed, leaving an outer layer as a hollow elastic model. RESULTS Simulations using the hollow elastic model were performed in 12 patients. In all patients, the clipping proceeded as scheduled. The surgeons postoperative assessment was favorable in all cases. This method enables easy fabrication at low cost. CONCLUSION Simulation using the hollow elastic model is thought to be useful for understanding of three-dimensional aneurysm structure.

The Trans-Visible Navigator: A See-Through Neuronavigation System Using Augmented Reality.

INTRODUCTION The neuronavigator has become indispensable for brain surgery and works in the manner of point-to-point navigation. Because the positional information is indicated on a personal computer (PC) monitor, surgeons are required to rotate the dimension of the magnetic resonance imaging/computed tomography scans to match the surgical field. In addition, they must frequently alternate their gaze between the surgical field and the PC monitor. OBJECTIVE To overcome these difficulties, we developed an augmented reality-based navigation system with whole-operation-room tracking. METHODS A tablet PC is used for visualization. The patients head is captured by the back-face camera of the tablet. Three-dimensional images of intracranial structures are extracted from magnetic resonance imaging/computed tomography and are superimposed on the video image of the head. When viewed from various directions around the head, intracranial structures are displayed with corresponding angles as viewed from the camera direction, thus giving the surgeon the sensation of seeing through the head. Whole-operation-room tracking is realized using a VICON tracking system with 6 cameras. RESULTS A phantom study showed a spatial resolution of about 1 mm. The present system was evaluated in 6 patients who underwent tumor resection surgery, and we showed that the system is useful for planning skin incisions as well as craniotomy and the localization of superficial tumors. CONCLUSIONS The main advantage of the present system is that it achieves volumetric navigation in contrast to conventional point-to-point navigation. It extends augmented reality images directly onto real surgical images, thus helping the surgeon to integrate these 2 dimensions intuitively.

Training in Brain Retraction Using a Self-Made Three-Dimensional Model

A hollow brain model was created using soft urethane. A tube passing through the hollow was attached for use as a water inlet and manometer. Water sufficient in quantity to realize the intended initial pressure was infused through the tube. The brain model was retracted with a brain spatula and the surgical corridor was opened. By measuring local force with a sensor set on the brain spatula, the model could be used for training in brain retraction. At the same time, the water column of the manometer was measured and the relationship with the force of the brain spatula was investigated. A positive correlation between the water column and local force was confirmed. This indicated that it was possible to use this model without a force sensor for the same training using water column measurements.

Training in Cerebral Aneurysm Clipping Using Self-Made 3-Dimensional Models

INTRODUCTION Recently, there have been increasingly fewer opportunities for junior surgeons to receive on-the-job training. Therefore, we created custom-built three-dimensional (3D) surgical simulators for training in connection with cerebral aneurysm clipping. METHODS Three patient-specific models were composed of a trimmed skull, retractable brain, and a hollow elastic aneurysm with its parent artery. The brain models were created using 3D printers via a casting technique. The artery models were made by 3D printing and a lost-wax technique. Four residents and 2 junior neurosurgeons attended the training courses. The trainees retracted the brain, observed the parent arteries and aneurysmal neck, selected the clip(s), and clipped the neck of an aneurysm. The duration of simulation was recorded. A senior neurosurgeon then assessed the trainees technical skill and explained how to improve his/her performance for the procedure using a video of the actual surgery. Subsequently, the trainee attempted the clipping simulation again, using the same model. After the course, the senior neurosurgeon assessed each trainees technical skill. The trainee critiqued the usefulness of the model and the effectiveness of the training course. RESULTS Trainees succeeded in performing the simulation in line with an actual surgery. Their skills tended to improve upon completion of the training. CONCLUSION These simulation models are easy to create, and we believe that they are very useful for training junior neurosurgeons in the surgical techniques needed for cerebral aneurysm clipping.

Evaluation of cerebral ischemia using near-infrared spectroscopy with oxygen inhalation

Abstract. Conventional methods presently used to evaluate cerebral hemodynamics are invasive, require physical restraint, and employ equipment that is not easily transportable. Therefore, it is difficult to take repeated measurements at the patient’s bedside. An alternative method to evaluate cerebral hemodynamics was developed using near-infrared spectroscopy (NIRS) with oxygen inhalation. The bilateral fronto-temporal areas of 30 normal volunteers and 33 patients with cerebral ischemia were evaluated with the NIRS system. The subjects inhaled oxygen through a mask for 2 min at a flow rate of 8  L/min. Principal component analysis (PCA) was applied to the data, and a topogram was drawn using the calculated weights. NIRS findings were compared with those of single-photon-emission computed tomography (SPECT). In normal volunteers, no laterality of the PCA weights was observed in 25 of 30 cases (83%). In patients with cerebral ischemia, PCA weights in ischemic regions were lower than in normal regions. In 28 of 33 patients (85%) with cerebral ischemia, NIRS findings agreed with those of SPECT. The results suggest that transmission of the changes in systemic SpO2 were attenuated in ischemic regions. The method discussed here should be clinically useful because it can be used to measure cerebral ischemia easily, repeatedly, and noninvasively.

Detection of cerebral ischemia using the power spectrum of the pulse wave measured by near-infrared spectroscopy

Abstract. The diagnosis and medical treatment of cerebral ischemia are becoming more important due to the increase in the prevalence of cerebrovascular disease. However, conventional methods of evaluating cerebral perfusion have several drawbacks: they are invasive, require physical restraint, and the equipment is not portable, which makes repeated measurements at the bedside difficult. An alternative method is developed using near-infrared spectroscopy (NIRS). NIRS signals are measured at 44 positions (22 on each side) on the fronto-temporal areas in 20 patients with cerebral ischemia. In order to extract the pulse-wave component, the raw total hemoglobin data recorded from each position are band-pass filtered (0.8 to 2.0 Hz) and subjected to a fast Fourier transform to obtain the power spectrum of the pulse wave. The ischemic region is determined by single-photon emission computed tomography. The pulse-wave power in the ischemic region is compared with that in the symmetrical region on the contralateral side. In 17 cases (85%), the pulse-wave power on the ischemic side is significantly lower than that on the contralateral side, which indicates that the transmission of the pulse wave is attenuated in the region with reduced blood flow. Pulse-wave power might be useful as a noninvasive marker of cerebral ischemia.

Early Diagnosis of Cerebral Ischemia in Cerebral Vasospasm by Oxygen-Pulse Near-Infrared Optical Topography

PURPOSE Early diagnosis of vasospasm is a key factor in the choice of treatment after subarachnoid hemorrhage (SAH). However, a noninvasive method of diagnosing delayed ischemic neurological deficit (DIND) has not been established. We therefore propose a new method of diagnosing cerebral ischemia using near-infrared optical topography (OT) with oxygen inhalation. MATERIALS AND METHODS We used a 44-channel OT system that covers the bilateral front otemporoparietal areas to assess 29 patients who underwent surgery within 72 h of the onset of SAH. The patients inhaled room air followed by oxygen for 2 min, and then peripheral oxygen saturation (SpO₂) was continuously monitored at the index fingertip. The patients were assessed by N-isopropyl-p-[¹²³I]iodoamphetamine (IMP)-SPECT and OT on the same day. Ischemic findings were confirmed using principal component analysis with reference to the systemic SpO₂value. RESULTS Seven of 29 patients developed DIND. Evidence of ischemia was identified by OT in all seven of these patients before the onset of DIND. The OT and SPECT findings agreed in 27 (93 %) of the 29 patients. DISCUSSION AND CONCLUSIONS Our method might detect cerebral ischemia before the onset of DIND and thus be clinically useful for assessing cerebral ischemia with vasospasm.

43. Assessment of cerebral ischemia using near infrared optical topography with inhalation of oxygen

while the potentials in the long head of left biceps femoris were normal. Four months later, he developed left drop foot; NCS revealed low amplitudes in left peroneal CMAP by peroneal nerve stimulation and left sural nerve sensory action potential (SNAP). The left gluteus medius was not weak but showed denervation potentials in EMG. Presently, he showed marked muscle atrophy, sensory loss and occasional neuralgia in the left L5 and S1 segments. CMAPs and SNAPs were all absent in the left leg in NCS. Cerebrospinal fluid (CSF) analysis showed 7.0 cells/ll and elevated protein level. MRI revealed swelling in left L4–S2 nerve roots. A biopsy specimen of the left sural nerve demonstrated marked loss of myelinated and unmyelinated fibers. A left S1 nerve root biopsy specimen demonstrated T-lymphocyte infiltration within the roots and ganglia and root sheath thickening. CSF lymphocyte analysis later revealed IgH rearrangement and atypism, suggesting a diagnosis of neurolymphomatosis.

31. Early diagnosis of cerebral vasospasm by oxygen-pulse near infrared optical topography

and nerve conduction velocities in 73 consecutive patients with ALS, 12 with spinal muscular atrophy (SMA), 12 with spinal-bulbar muscular atrophy (SBMA), and 36 with axonal neuropathy due to vasculitis (VN). Multiple axonal excitability measurements were performed for the median nerve in the ALS patients. The DML was prominently prolonged (=5.4 ms: over 125% of the upper limit of normal) in 8 ALS patients (11%), 1 SMA/SBMA patient (4.2%) and no VN patients (0%). In threshold electrotonus, the results of the ALS patients with markedly prolonged DML showed a tendency that the axonal resting membrane potential shifts in the depolarizing direction. Our findings suggest that, in ALS, there is a subgroup with prolonged DML unexplained by merely loss of the fastest axons, which is rare in other motor neuron diseases and neuropathies. The robust resting membrane depolarization in motor axon may result in inactivation of sodium channels, and thereby distal nerve conduction slowing in the terminal stage of ALS.