Keiko Irie

In vitro patient-tailored anatomical model of cerebral artery for evaluating medical robots and systems for intravascular neurosurgery

In this paper, we propose an in vitro patient-tailored biological model of human cerebral artery, an innovative platform for simulating intravascular neurosurgery to evaluate medical robots and devices. This anatomically accurate model reproduces 3-dimensional configuration of individual arteries with an artery-like thin membranous structure made of silicone elastomer. Its modeling resolution is 13 /spl mu/m. Presented modeling methodology also allows constructing any hollow structure, which is suitable for robot evaluations, making use of CAD. Presented model also reproduces the physical properties of arterial tissue with errors less than 5% (that include elastic modulus, poissons ratio and frictional coefficient). Thus the cerebral arterial model reproduces not only the behavior of arteries caused by surgical operations, but also the dynamic behavior of surgical robots and devices (e.g. elastic deformation and slip/stick motion). Furthermore, we also propose a novel method that allows developers to evaluate 3-dimensional stress condition on arterial wall, which is caused by surgical operations, by making use of the photoelastic effect. As there are almost no realistic hardware platform enough to fairly evaluate medical robots and devices, it should provide an advanced testing environment for developing robots and other various medical equipments, especially for intravascular neurosurgery.

Morphological Changes in Human Cerebral Arteries after Percutaneous Transluminal Angioplasty for Vasospasm Caused by Subarachnoid Hemorrhage

Light and electron microscopy were used to study morphological changes in cerebral arteries after percutaneous transluminal angioplasty (PTA) for vasospasm in two patients with aneurysmal subarachnoid hemorrhage. One patient died of gastric bleeding 5 days after PTA. Postmortem examination of the inflated middle cerebral arteries revealed heterogeneously extended walls and dilated lumina. Throughout the vessel walls, the extracellular matrix, which was composed of nonmuscle components such as increased collagen, was stretched in conjunction with the medial muscle component. Also, torn and thinned areas of the wall and intramural hemorrhages were caused by overinflation. The second patient died of massive cerebral infarction caused by diffuse vasospasm 5 days after PTA. Prominent stretching of the walls at the atheromatous plaque margin in the dilated vessel was found in addition to the morphological changes observed in the first patient. These observations suggest that characteristic pathological alterations might be present in the vessel wall at the site of angioplasty. The major mechanism of the long-lasting effects of PTA seems to be the stretching and disruption of both the degenerative muscle and the proliferative nonmuscle components, mainly in the media of the vasospastic vessels.

The use of mild hypothermia for patients with severe vasospasm: a preliminary report

The purpose of this study was to determine the effect of mild hypothermia on cerebral ischaemia due to severe vasospasm, which was refractory to medical and intravascular treatments and to assess the brain protection of this treatment in patients who underwent delayed aneurysm clipping after presenting with ischaemic neurological deficits. Mild hypothermia (32-34 degrees C of brain temperature) was employed in two groups: (1) Patients (Hunt and Kosnik grades I to II) who showed progressive neurological deficits due to vasospasm and did not respond to conventional therapy (Group 1) and (2) Patients who received delayed aneurysm clipping after presenting with ischaemic neurological deficits due to vasospasm (Group 2). Seven of 8 patients in both Groups showed a favorable outcome with mild hypothermia (good recovery in 5 and moderate disability in two patients). Mild hypothermia is considered to be effective on critical cerebral ischaemia due to vasospasm even after failure to response the conventional therapies and to provide brain protection in delayed aneurysm clipping.

The study of flow diversion effects on aneurysm using multiple enterprise stents and two flow diverters.

Background: Computer-based simulation is necessary to clarify the hemodynamics in brain aneurysm. Specifically for endovascular treatments, the effects of indwelling intravascular devices on blood stream need to be considered. The most recent technology used for cerebral aneurysm treatment is related to the use of flow diverters to reduce the amount of flow entering the aneurysm. To verify the differences of flow reduction, we analyzed multiple Enterprise stents and two kinds of flow diverters. Materials and Methods: In this research, we virtually modeled three kinds of commercial intracranial stents (Enterprise, Silk, and Pipeline) and mounted to fit into the vessel wall, and deployed across the neck of an IC-ophthalmic artery aneurysm. Also, we compared the differences among multiple Enterprise stents and two flow diverters in a standalone mode. Results: From the numerical results, the values of wall shear stress and pressure are reduced in proportion to the size of mesh, especially in the inflow area. However, the reduced velocity within the aneurysm sac by the multiple stents is not as significant as the flow diverters. Conclusions: This is the first study analyzing the flow alterations among multiple Enterprise stents and flow diverters. The placement of small meshed stents dramatically reduced the aneurysmal fluid movement. However, compared to the flow diverters, we did not observe the reduction of flow velocity within the aneurysm by the multiple stents.

Protective effect of mild hypothermia on symptomatic vasospasm: a preliminary report.

Mild hypothermia (32-34 degrees C of brain temperature) was used for brain protection in patients with progressive ischemic neurological deficits associated with severe cerebral vasospasm and who did not respond to medical treatment or intravascular angioplasty. Results showed that 2 of 3 patients in Hunt & Kosnik grade I to III and 2 patients who underwent delayed operation on day 5 and 9 each and had ischemic neurological deficits made good recovery with this treatment. Favourable outcome was obtained in 4 of 9 patients in grade IV and V. Mild hypothermia is thought to provide brain protection in critical ischemia due to severe cerebral vasospasm and can lengthen therapeutic time to employ angioplasty and intraarterial Papaverin infusion.

An in vitro patient-tailored model of human cerebral artery for simulating endovascular intervention

An in vitro patient-tailored reproduction model of cerebral artery, a hardware platform for simulating endovascular intervention for making diagnoses and surgical trainings is presented. 3-D configuration of vessel lumen is reproduced as vessel model with 13 microm modeling resolution, using CT and MRI information. Physical characteristics of cerebral artery, such as elastic modulus and friction coefficient, are also reproduced. We also propose a novel method to visualize stress condition on vessel wall using photoelastic effect. Consequently, it should be helpful for clinical applications, academic researches and other various purposes.

Patient-specific neurovascular simulator for evaluating the performance of medical robots and instrumens

An in vitro patient-specific vascular model, for simulating endovascular intervention is presented. Proposed vascular model reproduces the 3-dimensional vessel lumen structure using CT/MRI information with 13 mum resolution, and it also reproduce the physical characteristics of arterial tissue (elastic modulus and friction coefficient). Furthermore, in this paper, we propose a novel method to evaluate the stress on vasculature which is applied by surgical operations. This method allows quantitatively evaluating 3-dimensional stress conditions in real-time during surgical simulation. Finally, we constructed a comprehensive surgical simulation system, which reproduces whole human aorta structure (with more than Imm inside diameter), reproduce patient-specific pulsatile blood streaming, allowed to evaluate the stress applied to the aorta structure by surgical operations with almost same manner and environment as the practical endovascular intervention. Consequently proposed model, evaluation method and resultant system provides a very valuable platform for evaluating the performance of surgical robots and instruments developed by developers and researchers, and surgical procedures

Treatment of a spontaneous intracranial dissecting aneurysm with stent-assisted coil embolization

Arterial dissection is now recognized as an important cause of stroke. Most reported dissections involve the extracranial portion of the internal carotid artery (ICA) and vertebral arteries. Spontaneous dissecting aneurysms of the intracranial ICA are uncommon. Endovascular treatment for cerebral aneurysms has become widespread; however, the dissecting aneurysm is still difficult to treat if the parent artery has to be preserved. More recently, stenting has been advocated for use with endosaccular coiling, with the coils held in place by the stent. We herein report a spontaneous intracranial ICA dissecting aneurysm in a 51-year-old woman who was treated using a new technique of combined stent and coils.

Management of Complex, Surgically Intractable Intracranial Aneurysms: The Option for Intentional Reconstruction of Aneurysm Neck Followed by Endovascular Coiling

Background: A limited series of patients with aneurysm were reviewed retrospectively to analyze strategies for integrating microsurgical and endovascular techniques in the management of complex, surgically intractable aneurysms. Methods: Four patients were managed in Fujita Health University with a multimodality approach: intentional reconstruction of the aneurysm neck followed by endovascular coiling. Results: A total of 5 aneurysms were treated, of which 3 were large or giant in size, and 3 were fusiform or multilobulated. Complete angiographic obliteration was confirmed in 4 aneurysms (80%). All patients had a good outcome (Glasgow Outcome Scale score 5; mean follow-up, 64 months). Conclusion: As for complex, surgically intractable aneurysms, the intentional reconstruction of the aneurysm neck followed by endovascular coiling should be considered more often.

Intraoperative radiotherapy for gliomas

SummaryIntraoperative radiotherapy (IORT) was performed in 20 of 36 patients with glioma; 11 glioblastomas, 7 malignant astrocytomas, 2 benign astrocytomas. Twenty or 25 Gy of irradiation was delivered in a single fraction intraoperatively, followed by external beam irradiation. The electron beam energy was selected so that the 80% isodose line fell at 2 or 3 cm below the residual tumor surface. Median survival time of IORT group was 14 months and that of the control group was 10 months. Difference of survival curve was significant. There were 6 incidences of complication caused by IORT; 1 radionecrosis, 1 convulsion, 1 abscess, and 3 severe brain edemas. IORT is suited for the treatment of malignant gliomas.