Quantitative evaluation of upper limb ataxia in spinocerebellar ataxias.

OBJECTIVE: To quantitatively evaluate upper limb ataxia using a novel pen-like sensor device in patients with spinocerebellar ataxia (SCA) and to assess its validity, reliability, and sensitivity to disease progression. METHODS: We designed a cross-sectional and longitudinal study of patients with SCA and healthy controls. Upper limb ataxia was evaluated using a device that measures the three-dimensional position every 10 msec. Participants were instructed to move a pen-like part of the device iteratively between two buttons. We evaluated the time, length, velocity, and variation coefficient of the stroke, and calculated the distortion index using the mean squared error. The following scales were also evaluated: Scale for the Assessment and Rating of Ataxia (SARA), the International Cooperative Ataxia Rating Scale (ICARS), and the nine-hole pegboard test. Subjects were followed 12 months after the baseline evaluation. RESULTS: A total of 42 patients with SCA and 33 healthy controls were enrolled and evaluated. For all ataxia indices measured using the device there were significant differences between healthy controls and patients with SCA. Among the ataxia indices, the distortion index showed the strongest correlation with the SARA and ICARS upper limb score (Pearson's r = 0.647 and 0.722, respectively). Test-retest reliability was high for most of the ataxia indices. In the longitudinal analysis, the distortion index showed high standardized response mean and adjusted effect size, regardless of disease severity. INTERPRETATION: Our study demonstrated that the distortion index is a reliable functional marker that is sensitive to longitudinal change in patients with SCA.

Experimental Study of Coil Compaction: Impact of Pulsatile Stress.

Objective: Coil compaction after aneurysm embolization is one of the major issues associated with aneurysm recurrence. On the presumption that pulsatile stress to the aneurysm is responsible for coil compaction, we developed an experimental model in vitro to visualize the mechanical stresses exerted by blood pressure and pulse and their relation to coil compaction. Methods: A closed-type non-circulation system was developed by installing a syringe that generated pressure at one end of a tube, along with a spherical aneurysm made of silicone and a pressure sensor in the bifurcated end. We installed a fixed-pressure model under a steady pressure of 300 mmHg while the pressure-fluctuation model simulated the pressure variations using a plunger (in a syringe) by using a motor that applied pulsatile stress in the range of 50 mmHg for a 10-ms cycle. We devised four types of aneurysms with different depths and the same coil length. After coil packing, the aneurysms were observed for 3 days (the observation period in the pressure-fluctuation model corresponded to approximately 300 days in real time). The distance from the datum point to the observable coil loops was determined as the initial position, and the temporal change in the distance from that position was measured. Results: In the fixed-pressure model, the average distance of coil movement was very small (less than ±0.1 mm). In the pressure-fluctuation model, the movement of coils was observed to be significant for the two longest depths (0.11 and 0.14 mm). The maximal dynamic change in coil movement was observed on the second day. The range of movement was observed to decrease thereafter. Conclusion: Our experimental study enabled the observation of coil movement within a short duration. It examined coil compaction by applying pulsed pressure to the coils at high speeds. Consequently, a shift of the coil loops inside the incompletely occluded aneurysms was detected on applying a pulsed pressure.

A Novel Technique of Microcatheter Shaping using Real Image Display for Endovascular Aneurysmal Coil Embolization.

In coil embolization of intracranial aneurysms, guiding the microcatheter to an appropriate site in the aneurysm and stabilizing it there are important. In paraclinoid internal carotid aneurysms, complicated three-dimensional (3-D) shaping of the microcatheter tip is occasionally required. We devised a novel shaping method for microcatheters by using a real image display (RID). The usefulness of this technique was validated. We used a RID consisting of a couple of concave mirrors. A piece of patient-specific vascular model, which was made using a 3-D printer before the operation, was set inside the RID. We obtained a real 3-D image just above the RID. As a microcatheter and its shaping inner mandrel could be entered in the hologram of the vasculature, we could create the actual shape of the microcatheter. The shaped microcatheter could be navigated at the desired position in the aneurysm. Complete obliteration of the aneurysm was achieved without any trouble among 30 consecutive cases. We evaluated the effectiveness of the RID for making and navigating a microcatheter in cases with challenging anatomies. It was useful for favorable microcatheter shaping, as the RID could be entered inside the aneurysm models, unlike when tracing the outer surface of rigid 3-D models.

Remote Surgery Using a Neuroendovascular Intervention Support Robot Equipped with a Sensing Function: Experimental Verification.

PURPOSE: Expectations for remote surgery in endovascular treatments are increasing. We conducted the world's first remote catheter surgery experiment using an endovascular treatment-supported robot. We considered the results, examined the issues, and suggested countermeasures for practical use. METHODS: The slave robot in the angiography room is an original machine that enables sensing feedback by using an originally developed insertion force-measuring device, which detects the pressure stress on the vessel wall and alerts the operator using an audible scale. The master side was set in a separate room. They were connected via HTTP communication using local area network system. The surgeon operated by looking at a personal computer monitor that shared an angiography monitor. The slave robot catheterized and inserted a coil for an aneurysm in the silicon blood vessel model in the angiography room. RESULTS: Our robot responded to the surgeon's operations promptly and to the joystick's swift movements quite accurately. The surgeon could control the stress to the model vessels using various actions, because the operator could hear the sound from the insertion force. However, the robot required a time gradient to reach a stable advanced speed at the time of the initial movement, and experienced a slight time lag. CONCLUSION: Our remote operation appeared to be sufficiently feasible to perform the surgery safely. This system seems extremely promising for preventing viral infection and radiation exposure to medical staff. It will also enable medical professionals to operate in remote areas and create a ubiquitous medical environment.

Development and clinical evaluation of a contactless operating interface for three-dimensional image-guided navigation for endovascular neurosurgery.

PURPOSE: In endovascular neurosurgery, the operator often acquires three-dimensional (3D) images of the cerebral vessels. Although workstation reoperation is required in some situations during treatment, it leads to time loss because a sterile condition cannot be maintained and treatment must be temporarily interrupted. Therefore, a workstation reoperating system is required while maintaining the desired sterility. METHODS: A contactless operating interface using Kinect to control 3D images was developed via gesture recognition for endovascular neurosurgery and was applied to a 3D volume rendering technique (VRT) image reconstructed at the workstation. The left-hand movement determines the assigned functions, whereas the right-hand movement is used like a computer mouse to pan and zoom in/out. In addition to the interface, voice commands were used and assigned to digital operations, such as image view changes and mode signal changes. RESULTS: This system was used for the actual endovascular treatment of cerebral aneurysms and cerebral arteriovenous malformations. The operator and gesture were recognized without any problems. Using voice operation, it was possible to expeditiously set the VRT image back to the reference angle. Furthermore, it was possible to finely adjust gesture operations, including mouse operation, and treatment was completed while maintaining sterile conditions. CONCLUSION: A contactless operating interface was developed by combining the existing workstation system with Kinect and voice recognition software, allowing surgeons to perform a series of operations, which are normally performed in a console room, while maintaining sterile conditions.

A Method to Evaluate Vessel Deviation during Withdrawal of a Stent Retriever Using a Silicon Vascular Model.

Objective: Catastrophic complications may develop because of vessel deviation during device delivery into intracranial vessels for neurointerventions. We report a novel method using a silicon model capable of evaluating vessel deviation as a numerical value. Methods: In all, 10 tiny markers, each with a pitch of approximately 5 mm, were attached to the vessel model along the long axis. We used a high-resolution camera to record movies of the deviation of the vessel model while employing different stent retrievers. The movies were reviewed to determine the maximum deviation of each marker on the vessel model. Results: As expected, stent retrievers of the same type exhibited more vessel shifts when they had a larger diameter and longer length. On the other hand, stents with a segmental structure demonstrated less vessel deviation than those with a tubular structure, regardless of the large lumen and long length. Conclusion: If the degree of vessel stress can be represented by a numerical value, areas where the careful use of different devices for neurointerventions is required may be able to be identified. Moreover, this method may be useful for training.

Novel Concept and Device for Holding the Rotational Hemostasis Valve During Neuroendovascular Procedures.

BACKGROUND: Hemostasis valves are commonly used in neurointerventions. We propose a novel concept for fixing hemostasis valves to the operating table during procedures. Moreover, we report our preliminary in vitro experience using these new devices created using a 3-dimensional printer. METHODS: The hemostasis valve holder (HVH) comprises 2 components: an inner fixer and an outer socket. It was designed to be suitable for use with all rotational hemostasis valves commercially available. HVH contains magnets at the bottom that facilitate its attachment to a thin steel board beneath a sterilized drape on the working table. We evaluated the HVH's efficacy via in vitro experiments involving stent placement by a single operator. RESULTS: HVH allowed easy attachment to and detachment from the rotational hemostasis valve. Moreover, the use of multiple HVHs facilitated operators to concentrate on the procedure because they continuously prevented the unexpected movement of devices at several points. Use of HVHs enables stent placement to be performed even by a single operator. We observed that forming a loop of the stent delivery catheter between 2 HVHs enhanced the device control. CONCLUSIONS: HVHs should be more useful than conventional methods, particularly in cases requiring fine complementary control of both a microcatheter and microguidewire.

Novel Operation Support Robot with Sensory-Motor Feedback System for Neuroendovascular Intervention.

BACKGROUND: Robotic technology is rapidly developing in the medical field, particularly contributing to support operative intervention using the da Vinci system during endoscopic surgery. Neuroendovascular intervention robot surgery is preferred when aiming to reduce radiation exposure among surgeons. METHODS: We developed a prototype of a support robot with 2 independent slaves manipulating both the microcatheter and microguidewire connected with the remote master driver with 2 joysticks. This design simulates usual catheterization with both hands. The slave manipulator has a sufficient output force >1 N to reproduce the exact master intervention without slip and delay. This machine has a unique function that indicates the reaction force of the resistance on wire stuck using the sensor system. We investigated the master-slave response, reliability of the force gauge, and degree of slippage of the slave motion on the table and checked the controllability, safety, and reproducibility of microcatheterization and insertion maneuver into the experimental aneurysm in the in vivo silicone vessel model. RESULTS: We realized the well master-slave response with a stable driving speed of the microguidewire at approximately 1 mm/s and with linear correlation between the output voltage and driving force. Also, we confirmed the well safety function to avoid the overloading to the vascular wall with the slippage of the slave roller on loading >1 N pushing force. Successful microcatheterization and insertion into the aneurysm model was performed in the wet vascular model corresponding to the 3-dimensional handling without excessive stress to the vascular or aneurysmal wall. CONCLUSIONS: Neuroendovascular intervention requires delicate power adjustment with fine finger control. Our support robot for neuroendovascular interventions demonstrated the accurate reproducibility of the operator's maneuver and safe operation in the vascular model using the sensor system. This system will realize the neurointervention without human operators in the AngioSuite and may facilitate telesurgery with remote control in the near future.

Experimental Direct Measurement of Clot-Capturing Ability of Stent Retrievers.

BACKGROUND: Stent retrievers (SRs) can be used to perform mechanical thrombectomy for the treatment of acute major arterial occlusion. Recanalization is faster, and outcomes are better with treatment involving these devices than with internal treatment. Although several SRs are available, their clot-capturing abilities are unclear. Therefore in the present study, we numerically evaluated the clot-capturing abilities of SRs in an experimental vascular model. METHODS: A sham clot (urethane foam) was fixed with sutures at the middle of a vascular model (polyvinyl chloride tube). One end of the tube was connected to a measuring instrument. From the other end, an SR was inserted and deployed over the sham clot. The delivery wire of the stent was then withdrawn at a constant velocity using an automatic withdrawal machine. The maximum frictional force before the stent left the clot was measured. Five stents (Trevo ProVue [2 sizes], Revive, and Solitaire [2 sizes]) and three stent-deployment techniques (standard, push-and-fluff, and wire-push techniques) were evaluated. RESULTS: The clot-capturing ability (maximum withdrawing force [N: newton]) was greater for large-diameter stents than for small-diameter stents (mean 0.39 ± 0.11 vs. 0.56 ± 0.18). For Trevo and Revive, the clot-capturing ability was highest with the push and fluff technique (mean 0.43 ± 0.05). For Solitaire, the ability was the highest with the simple wire-push technique (mean 0.705 ± 0.16). CONCLUSIONS: We successfully numerically evaluated the clot-capturing abilities of SRs. The clot-capturing ability differed among SRs and among stent-deployment techniques.

Experimental Evaluation of Stent Clot Retrieval Using the Confront Clot Scrambling Method with an Equitable Automatic Withdrawal Machine.

BACKGROUND: Stent clot retrievers can be used to perform mechanical thrombectomies to treat cases of acute major arterial occlusion. This approach is associated with faster recanalization and better outcomes than internal treatments. The function of the stent retrievers is based on a technique known as confront clot scrambling method (CCSM), which usually involves the insertion of two stent retrievers (one from each side) and the simultaneous withdrawal of the retrievers with an equal force. It was determined that a stent used to remove the sham clot possessed a stronger ability for clot retrieval. However, this method involves inherent manipulation bias, and the results may vary due to operator-specific factors. Thus, this approach can be difficult to teach, especially to beginners. MATERIALS AND METHODS: We evaluated the accuracy of using an equitable automatic withdrawal machine for the CCSM on a model of a sham clot in the middle of a polyvinyl chloride tube. RESULTS: This tool is expected to facilitate thorough and repeated training that is needed to learn the fine maneuvers against invisible vessels associated with actual endovascular clot retrieval, particularly for beginners.

Evaluation of the characteristics of various types of coils for the embolization of intracranial aneurysms with an optical pressure sensor system.

INTRODUCTION: In coil embolization for an intracranial aneurysm, it is important to appropriately choose the coil most suitable for coping with various unforeseen situations. Additionally, because dense coil packing of the aneurysm sac is the most important factor to avoid a recurrence, properly selecting the coil is essential. In this article, the authors measured the coil insertion pressure of various types of coils with a newly developed sensor system, and coil characteristics were investigated. METHODS: The sensor consists of a hemostatic valve connected to the proximal end of a microcatheter. The sensor principle is based on an optical system. Using this, an experimental silicone aneurysm embolization was performed automatically at constant speed. The pattern of the insertion pressure and the maximum insertion pressure (MIP) were analyzed for the various types of coils. The sensor continuously monitored the mechanical force during the insertions. RESULTS: The sensor adequately recorded the coil insertion pressure during embolization in each coil. MIP was generally ranked in order of the coil type. The soft type coils required relatively less insertion pressure than standard/helical and 3D type. As for the patterns of coil insertion pressure, each coil presented a saw-like pressure pattern, though we observed some slight differences. 3D type coils showed peak pressure at the moment of "painting". Coil loop diameters barely affected MIP. However, as to the patterns of pressure, larger size coils more often presented the peak. CONCLUSIONS: Coil characteristics were well evaluated. The results obtained here reflected some actual clinical experience. Furthermore, collecting the in vivo study is mandatory, which may provide clinically useful data.

A novel pressure sensor with an optical system for coil embolization of intracranial aneurysms. Laboratory investigation.

OBJECT: In endovascular coil embolization for an intracranial aneurysm, the excessive pressure created during coil insertion into an aneurysm can cause a catastrophic rupture or dislodge a microcatheter tip from the aneurysm dome, resulting in insufficient embolization. Such undue mechanical pressure can only be subjectively detected by the subtle tactile feedback the surgeon experiences. Therefore, the authors of this study developed a new sensor device to measure the coil insertion pressure via an optical system. METHODS: This novel sensor system consists of a hemostatic valve connected to the proximal end of a microcatheter (Y-connector). The sensor principle is based on an optical system composed of a light-emitting diode (LED) and a line sensor. The latter measures how much the coil-delivery wire slightly bends in response to the insertion pressure by detecting the wire shadow. This information is translated into a given force level. Experimental aneurysm embolization was performed using this optical sensor. A silicone aneurysm model and an in vivo model (porcine aneurysm model) were used in this study. Several surgeons manually performed the coil insertions. The sensor continuously monitored the mechanical force during the insertions. RESULTS: The sensor adequately recorded the coil insertion pressure during embolization. The presence of the sensor did not hinder the embolization procedure in any way. During embolization in the silicone aneurysm model, a sinusoid pattern of pressure occurred, reflecting actual clinical experience. Similar results were obtained in the in vivo study. CONCLUSIONS: This new sensor device adequately measures coil insertion pressure. This system provides potentially safer and more reliable aneurysm embolizations.