Relationship between Shape Retention and X-ray Absorption Value of the Tip of Microcatheters in Neuroendovascular Treatment.

Objective We noticed that the X-ray absorption value of the tip of each microcatheter used for aneurysm treatment varied from product to product. We hypothesized that the differences were caused by variations in the metal's density braid, which could be related to the ability of the tip to retain its shape. Methods The X-ray absorption value of each microcatheter tip was measured. Next, heat forming was performed using a shaping mandrel at 6 mm and 90 degrees to determine whether there was a correlation between the X-ray absorption value and the forming angle. Next, the optimal mandrel angle for forming each microcatheter at 90 degrees was investigated. We also examined the shape retention after 20 times wire insertions into each microcatheter. Conclusion It was found that the higher the X-ray absorption value, the harder it was for the microcatheter to be formed. The mandrel angle required to form 90 degrees was determined by the X-ray absorption value. The higher the X-ray absorption value, the higher the shape retention of the tip shape. The heat formation and shape-retention conditions of the microcatheter tip were correlated with the X-ray absorption value of the metal braid. Even for unknown microcatheters, the optimum shaping conditions can be inferred from the X-ray absorption value.

Rigid covalent bond ofα-sulfur investigated via temperature-dependent EXAFS.

This study performs extended x-ray absorption fine structure (EXAFS) measurements for the S-K edge in the temperature range of 10 and 300 K in the transmission mode using a photodiode to detect the transmitted x-rays. It provides the first report of temperature variations in the structural parameters ofα-S. As the temperature increases from 10 to 300 K in the Fourier transform ofkχ(k)the first peak corresponding to the covalent bond of the eight-membered ring becomes slightly low anomalously despite thermal disturbances. However, as in normal materials, the second peak at 300 K decreases to approximately half of that at 10 K, which contains several intra- and inter-ring correlations. All structural parameters of the covalent bond obtained by nonlinear least squares fitting exhibit missing temperature variations. A value of zero for the asymmetric parameter in the EXAFS (C3) implies that the potential of the covalent bond is symmetric, and the constant value of the mean square relative displacement (MSRD) with temperature implies that the potential is extremely high. The Einstein model fitting for the temperature variation in the MSRD yields an Einstein temperature of 942 K and force constant (K) of 405 N m-1. The value ofKis the largest among those of chalcogen elements.

A Novel Approach to Neuroendovascular Treatment Looking Up from the Ascending Aorta Using an Alpha Shape Guiding Catheter.

BACKGROUND: A method of guiding an intermediate catheter from a new alpha-type guiding catheter placed in the ascending aorta to the carotid artery is evaluated in neuroendovascular treatment in challenging anatomic directions of the guiding catheter, such as the bovine aortic arch and type III aortic arch. METHODS: The existing 8-Fr guiding catheter was given a strong bending shape at the tip to make it an alpha type. The total length of the catheter was 85 cm. This guiding catheter was inserted into the ascending aorta to verify whether a 6-Fr intermediate or aspiration catheter could be coaxially guided into the right and left internal carotid arteries. A silicone vascular model was used for evaluation and in actual clinical cases. RESULTS: Creating an alpha shape of the catheter at the aortic arch was very easy. The inner catheter could be easily guided from the brachiocephalic artery to the right common carotid artery by pushing the alpha shape guiding catheter toward the aortic valve. The catheter was easily guided into the left common carotid artery when the α-guide was pulled a little bit backward. The 0.071-inch lumen aspiration catheter reached the bilateral middle cerebral arteries. CONCLUSIONS: The 8-Fr alpha shape guiding catheter quickly guides the inner catheter into the bovine and the type III aortic arch by looking up from the ascending aorta.

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.

Local Balloon-Assisted Navigation of a Microcatheter into an Aneurysm during Intracranial Aneurysmal Coiling: A Dunk Shot Technique.

OBJECTIVES: Various endovascular approaches have been reported for patients with intracranial aneurysms. However, the safety of navigating a microcatheter into the aneurysm remains debatable. In this study, we evaluated a novel method "dunk shot technique," in which a proximal balloon and a local balloon are used for navigation of a microcatheter into an aneurysm under challenging situations. MATERIALS AND METHODS: We have reported two cases of unruptured internal carotid artery-superior hypothalamic artery aneurysm. An 8-F balloon-attached catheter was used as the guiding catheter. A local balloon catheter for neck remodeling and a microcatheter for coil insertion were navigated around the aneurysmal neck region. When it seemed difficult to navigate a microcatheter into an aneurysm, both the guiding balloon and a local balloon catheter were used for assistance. After inflation of the guiding balloon, the local balloon was inflated partially to negotiate the tip of the microcatheter. RESULTS: The uncontrollable tip of the microcatheter could be intentionally moved by the local balloon. CONCLUSIONS: We evaluated the effectiveness of the balloon-assisted technique for the navigation of a microcatheter in cases with challenging anatomy. A little bit of direct effect to the tip of the microcatheter by a local balloon could produce effective outcomes under the proximal flow arrest.

Unruptured Paraclinoid Carotid Aneurysms Occur More Frequently in Younger Ages.

PURPOSE: We investigated the age distribution of cerebral saccular aneurysms in various locations to clarify the differences by location and discuss the mechanism of formation. MATERIALS AND METHODS: We retrospectively assessed clinical material obtained from 1,252 unruptured aneurysms treated with endovascular embolization between 2004 and 2019. Age, sex, laterality, and size were investigated by the location of aneurysms, classified as cavernous internal carotid artery (ICA), paraclinoid ICA, supraclinoid ICA, anterior communicating artery, anterior cerebral artery, middle cerebral artery, basilar artery complex, and posterior inferior cerebellar artery. Paraclinoid aneurysms were subclassified into 3 patterns according to their projecting direction: S-type, with superior protrusion; M-type, with medial protrusion; and P-type, with posteroinferior protrusion. RESULTS: There was no significant difference by location for sex, laterality, and size. The mean age of patients with paraclinoid aneurysms (56.5 years old) was significantly lower than that of other aneurysm patients (64.3 years old). Notably, 40% of the patients with M-type aneurysms were <50 years old. This percentage was significantly higher than that of aneurysms at other locations (P<0.05). CONCLUSION: We found a young female predominance for patients with paraclinoid carotid aneurysms. This study may suggest that congenital factors contribute to paraclinoid aneurysm formation as well acquired factors, such as hemodynamic stress, atherosclerotic wall damage, and local inflammation.

Pull the Trigger Sign: A Novel Method to Identify the Clot Position during Acute Endovascular Thrombectomy.

Objective: Accurately determining the clot position is highly important for immediate recanalization when endovascular mechanical thrombectomy is performed using a stent retriever and aspiration catheter. We describe a new method that facilitates the precise identification of the clot position called pull the trigger sign (PTS). Case Presentation: Selective angiography was performed through a 0.027-inch microcatheter that penetrated the clot into the distal lumen. Although the contrast media highlighted the occluded artery, it often stagnated in the distal artery. It was washed away at a certain point when a stent clot retriever was deployed over the potential clot site. We hypothesized that this point represented the exact position of the clot's proximal end and used in vitro analyses to assess this hypothesis. Briefly, a circulation-enabled silicone vascular model in which colored water was used to simulate stagnation beyond a fake clot was developed and utilized to investigate PTS six times. The rate of identifying PTS in the vascular model was 100%. As hypothesized, stagnant fluid was washed away when the deployed stent reached the clot's proximal position. The clinical efficacy of PTS was also confirmed. Conclusion: PTS was useful in revealing the precise position of clot's proximal end, which enabled safer contact aspiration when using an aspiration catheter. Thus, PTS led to a higher success rate and faster recanalization in the first attempt than conventional methods.

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.

Cholesterol Embolization Syndrome After Carotid Artery Stenting Associated with Delayed Cerebral Hyperperfusion Intracerebral Hemorrhage.

BACKGROUND: The cholesterol embolization syndrome (CES) results from the distal embolization of cholesterol crystals from atheromatous plaques in large vessels such as the aorta and results in multiorgan damage. CASE DESCRIPTION: We present the case of a patient with definite CES with skin manifestations (e.g., blue toes) and renal and neurological dysfunction, including parenchymal hematoma with cytotoxic and vasogenic edema after he had undergone left carotid artery stenting for symptomatic critical left carotid artery stenosis. CONCLUSIONS: Our patient with CES had cutaneous involvement affecting the lower limbs and renal and neurological involvement. High clinical suspicion and early treatment can reduce the mortality and morbidity after endovascular procedures. The neurological symptoms had most likely resulted from delayed cerebral hyperperfusion syndrome resulting in intracerebral hemorrhage.

Initial Clinical Experience of Using a Newly Designed Preshaped Microguidewire in Acute Endovascular Thrombectomy.

Mechanical thrombectomy has been widely used for the treatment of acute ischemic stroke. During this procedure, operators must navigate the microcatheter with a microguidewire (MGW) into vessels that cannot be visualized on fluoroscopy as rapidly as possible. In this study, we developed a modified pigtail-shaped MGW (MPMGW) for security and controllability. Moreover, the efficacy of the MPMGW for the treatment of acute ischemic stroke was assessed. The MPMGW was designed using 0.014 MGW. Because we created four MPMGWs during a clinical evaluation before the launch in the market, these wires were used in four consecutive patients with acute ischemic stroke in the single institution. The occluded arteries were the basilar artery (n = 1), middle cerebral arteries (M1 and M2, n = 2), and internal carotid artery (n = 1). All four procedures were conducted without any complications. The procedures included navigating the MGW and passing it through the clot. Complete recanalization was achieved in all cases. The average time between femoral artery puncture and recanalization was 15 min. The use of the preshaped MPMGW in acute thrombectomy was effective in terms of both security of procedure and reduction in recanalization time.

Novel Technique for Detection of Actual Position of Clot During Endovascular Clot Retrieval: Assessment of Microcatheter Withdrawing Angiography.

BACKGROUND: When endovascular clot retrievals are performed using a stent retriever and/or an aspiration catheter, identifying the accurate position of a clot is extremely important for a successful immediate recanalization. Herein, we report a new technique called microcatheter withdrawing angiography, which facilitates the identification of the precise position of a clot. The negative shadow appearance of the clot on angiography was referred to as the actual crab claw sign. METHODS: When a 0.027-inch microcatheter penetrated the clot after inserting a 0.014-inch microwire, selective angiography was conducted using the microcatheter. Simultaneously, the microcatheter was slowly withdrawn with continuous contrast media injection, while the microwire was kept in the distal vessel. The precise position of the clot was found, which was referred to as the actual crab claw sign. Next, we conducted in vitro and in vivo analyses. RESULTS: The actual crab claw sign could be identified in the vascular model and in actual clinical settings. Therefore the sweet spot of the stent retriever could be set over the clot, and an accurate contact aspiration could be performed using an aspirator. CONCLUSIONS: Microcatheter withdrawing angiography can help identify the actual crab claw sign. This technique has a higher success rate and faster recanalization than conventional strategy, particularly in challenging cases of unsuccessful recanalization during the first attempt.

Efficacy of Endovascular Proximal Occlusion before Direct Reposition Surgery of Blunt Cervical Fracture with Unilateral Vertebral Injury.

Cerebral infarction related to traumatic vertebral artery (VA) injuries is not common. However, if VA injuries cause ischemic and/or hemorrhage stroke, these subsequent problems can result in severe residual impairment and mortality. Herein, we present five patients with cervical vertebra fractures due to blunt cervical trauma who underwent preoperative endovascular therapy. Between June 2010 and April 2018 in our hospital, five patients with traumatic occlusion of a unilateral VA underwent coil embolization to prevent post-surgical stroke due to reperfusion in the VA. Because of cervical instability or subluxation, all of the patients received endovascular therapy before surgery for their cervical fracture. None of the patients presented with stroke after presurgical embolization and direct surgery. When stagnated blood, including thrombi, in the occluded VA is released during cervical surgery, brain embolism may occur. Therefore, early cerebrovascular vessel assessment and presurgical endovascular treatment must be considered to prevent stroke after direct surgery.

A Novel Technique for Microcatheter Additional Shaping During Intracranial Aneurysmal Coil Embolization: Microcatheter Shaping Cast.

BACKGROUND: When a shaping mandrel is inserted into the tip of a preshaped microcatheter, the existing curve becomes uncertain because the tip is straightened by the inner mandrel. Therefore, we developed a way to perform microcatheter shaping by means of an external cast, which we named "microcatheter shaping cast." TECHNIQUES: A shaping mandrel attached to a microcatheter was used and coiled 4-5 times around a metallic introducer, which was attached using a microguidewire. Then, a stent-like handmade cast was prepared. After the microcatheter tip was inserted into the cast, it was manually bent according to the aneurysmal shape and size. The tip and cast were heated with a hot air gun. We evaluated the relationship between degrees of bending and heating time to achieve appropriate right-angled shaping memory. CONCLUSIONS: The presented microcatheter shaping method should be more useful than conventional internal shaping, especially in cases that require an additional microcatheter shaping or reshaping during aneurysmal coil embolization.

Precautions for using a Filter Protection Device with a Flow Reversal Method during Carotid Artery Stenting: A Case Report on In-Filter Thrombus.

The combination of a flow reversal with two balloons and a filter protection device is one of the safest methods that can be used during carotid artery stenting (CAS). Although major adverse events did not occur under restrict protection, we experienced a case of in-filter thrombus during the procedure. A 68-year-old male presented with temporary right hemiparesis. The radiological examinations revealed 95% stenosis on the origin of the left internal carotid artery (ICA). The patient underwent left CAS of wherein a proximal common carotid artery balloon, an external carotid artery balloon, and a distal ICA filter, with continuous flow reversal to the femoral vein, were used. Although the reversal circulation was established, a massive newly developing thrombus was found in the proximal side of the filter. After an additional systemic heparinization, the thrombus disappeared. The procedure was performed without any complications. Physicians should be aware of the risk of developing intraprocedural thrombosis in a filter protection device. Because the filter protection device is designed for the antegrade flow, it may promote the development of thrombus against the retrograde flow. Thus, the filter protection device should be retrieved first under the flow reversal circumstance to avoid the distal migration of a clot around the filter device.

Efficacy and Safety of a Modified Pigtail-Shaped Microguidewire during Endovascular Thrombectomy.

A 75-year-old man presented with right-sided hemiplegia and was diagnosed with a left middle cerebral artery occlusion. He underwent endovascular thrombectomy, and a bulge was found. A modified pigtail-shaped microguidewire (MPMGW) proved useful for diagnosis because it allowed differentiation between the occluded artery and a saccular aneurysm as the etiology. When a clot was partially retrieved, a previously unidentified vessel dilatation appeared. The dilatation origin was unclear and could have resulted from either the occluded artery or an unruptured saccular aneurysm. We tried to navigate the MPMGW into the bulging area. The patient showed unusual body movement attributed to pain and the dilatation was diagnosed as an aneurysm. Subsequent 3-dimensional angiography revealed a recanalized artery and the aneurysm. With no subarachnoid hemorrhage or extravasation of the contrast medium. The hemiplegia dramatically improved. An MPMGW may be useful in acute thrombectomy where the target vessel cannot be visualized during the procedure.

A novel approach involving a microcatheter tip during aneurysmal coil embolization: The Γ (gamma) tip method.

Complete and secure occlusion of the entire aneurysmal neck remains a problem despite major advances in the treatment of intracranial aneurysms using endovascular coil embolization. Here, we present our initial clinical experience using a novel strategy for endovascular coil embolization involving a microcatheter tip, known as the "Γ (gamma) tip method," and compare the in vitro results of this technique with those of conventional straight microcatheters. The microcatheters were bent at a right angle starting 1-2 mm from the length of the tip using a catheter-shaping mandrel and a hot air gun. The tiny right-angled tip is the "Γ tip." In aneurysm models, we assessed the efficacy of shaping during coil deployment. The Γ-tipped microcatheters demonstrated better movement and oscillation during insertion of the coil into the aneurysm compared with the straight-tipped catheters. Moreover, the Γ-tipped microcatheter provided less coil protrusion into the parent artery and less microcatheter kickback compared with the straight tip. With the Γ-tipped microcatheter, even if the first coil loop migrated into the parent artery, its subsequent dynamic movement routed it back into the aneurysm. The Γ tip method enabled smooth movement of the microcatheter into the aneurysm, demonstrating the safety and security of coil insertion using the Γ tip compared with the conventional straight tip.

Efficacy of three-dimensional rotational fluoroscopic unit guidance for lumbar cerebrospinal fluid drainage among patients with unsuccessful initial attempt at bedside.

Lumbar cerebrospinal fluid drainage has been widely performed in patients at the bedside; however, technical failure can occasionally occur as a result of blind maneuvering. Herein, we present the use of rotational fluoroscopic unit-guided lumbar drainage for patients with an unsuccessful initial attempt at bedside. In four of the 24 patients with aneurysmal subarachnoid hemorrhage, initial lumbar drainage could not be performed at bedside. Thus, a three-dimensional rotational technology guided by a high-quality fluoroscopic unit was used. After a cone-beam computed tomography scan was performed, an accurate puncture point and a target thecal sac were identified using the software. The fluoroscopic unit helped us to identify the puncture point and trajectory with a laser pointer on the patient. A needle was inserted along the tract until the cerebrospinal fluid was collected. The lumbar drainage tube was successfully inserted with a single puncture in all four patients. Rotational fluoroscopic technology helps to identify a suitable puncture point, trajectory and target site for lumbar spinal drainage. Our technique is considerably useful in an era wherein minimally invasive procedures are preferred.

Traumatic Carotid-Cavernous Fistula Associated with Persistent Primitive Trigeminal Artery Successfully Treated Using In-Stent Coil Embolization.

BACKGROUND: Persistent primitive trigeminal artery (PPTA) is the most common type of fetal carotid-basilar persisting communication in adulthood; however, carotid-cavernous fistulas (CCFs) associated with PPTA are rare. CASE DESCRIPTION: An 84-year-old woman presented with traumatic CCF associated with PPTA manifesting as vascular bruit. Transarterial embolization was performed. Although a detachable coil was deployed at the fistula point, it was easy to migrate into the cavernous sinus because of the high-flow shunt. Therefore, a stent was deployed in the PPTA, and the inner lumen of the stent with a focus on the fistula point was occluded by using coils. Subsequently, the CCF completely disappeared. CONCLUSIONS: In-stent coil embolization was effective and reasonable for the high-flow CCF associated with the PPTA. This method reduced the number of coils required and operating time. However, careful preservation of perforators is needed.

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.