Neuroendovascular magnetic navigation: clinical experience in ten patients

Introduction The magnetic navigation system consists of an externally generated magnetic field that is used to control and steer a magnetically tipped microguidewire. The goal of this study was to demonstrate that the use of the magnetic navigation system and its magnetic microguidewire is feasible and safe in all types of neuroendovascular procedures. Methods A magnetic navigation system is an interventional workstation that combines a biplanar fluoroscopy system with a computer-controlled magnetic field generator to provide both visualization and control of a magnetically activated endovascular microguidewire. Ten consecutive patients underwent a variety of neuroendovascular procedures using the magnetic guidance system and magnetic microguidewire. All patients presented with a neurovascular disease that was suitable for endovascular treatment. Multiple different devices and embolic agents were used. Results Of the ten patients, three were male and seven female. Their mean age was 53.9 years. The predominant neurovascular condition was the presence of intracranial aneurysm (nine patients). One patient had a left mandibular arteriovenous malformation. All treatments were successfully performed on the magnetic navigation system suite. The magnetic navigation system and the magnetic microguidewire allowed safe and accurate endovascular navigation allowing placement of the microcatheters in the desired location. There were no neurological complications or death in our series. Conclusion The use of the magnetic navigation system and the magnetic microguidewire in the endovascular treatment of patients with neurovascular diseases is feasible and safe.     

微导丝成袢技术在小角度大脑前动脉插管中的应用

目的 :报道采用微导丝成袢技术对一些小角度大脑前动脉 (ACA)插管的经验。方法 :把微导丝头端塑成弯度较大的倒置伞柄状 ,当其抵达颈内动脉 (ICA)的虹吸段时 ,把其顶在ICA的壁上并稍用力向前推微导管 ,使微导丝形成一个U型袢 ,并顺势把该袢送入大脑中动脉 (MCA)的M1 段。随后回拉微导丝使其勾住A1 段开口 ,不断后撤微导丝 ,使其的头端不断进入A1 ,最后送入微导管。结果 :12例患者均采用该技术成功地对ACA进行了超选择性插管 ,闭塞了动脉瘤。技术成功率 10 0 %,无并发症。结论 :当常规方法失败后 ,微导丝成袢技术十分适合于小角度ACA的插管     

Magnetic guide-wire navigation in pulmonary and systemic arterial catheterization: initial experience in pigs

PURPOSE: Cardiovascular catheterization can be challenging whenever a stenosis or an abnormal vascular course interferes with probing the target vessel. This study addresses the feasibility of navigating a guide wire with a magnetic tip by an external magnetic field through pulmonary and systemic arteries in an experimental porcine model. MATERIALS AND METHODS: We investigated six piglets using magnetic guide-wire navigation. Two pulmonary arteriograms were taken from different angles in order to reconstruct the three-dimensional vessel anatomy. A computer interface then calculated three-dimensional coordinates for the vessel in space. Using these coordinates, two external magnets were positioned to create magnetic vectors along the expected vessel course. Magnetically enabled guide wires were then navigated into the vessels using the magnetic field to orient the guide-wire tips. Aortic and renal branches were addressed in a similar fashion. Difficulty in reaching the target vessel was reflected by the number of attempts that were necessary. After 10 failed attempts, the maneuver was recorded to have failed. RESULTS: Thirty-five of 37 (94.6%) arteries with branches at acute angles were reached successfully using magnetic navigation. In two pigs, the left upper lobe artery could not be probed. Peripheral arteries of small diameter were easier to reach than large central arteries, requiring less attempts. CONCLUSIONS: Magnetic guide-wire navigation is feasible in the arteries of the lungs, the head and neck, and the kidneys. It is particularly useful in entering small arterial branches at acute angles and may facilitate interventional therapy in a variety of vascular diseases in children and adults.     

Safety of MRI-guided endovascular guidewire applications

Magnetic radiofrequency (RF) fields applied during magnetic resonance imaging (MRI) may induce heating in devices made from conductive materials. The present paper reports on theoretical and experimental studies on the RF heating resonance phenomenon of an endovascular guidewire. A nitinol-based guidewire was inserted into a vessel phantom and imaged at 1.5 and 0.2 T with continuous temperature monitoring at the guidewire tip. The heating effects due to different experimental settings were examined. A model is developed for the resonant current and the associated electric field produced by the guidewire acting as an antenna. Temperature increases of up to 17 degrees C were measured while imaging the guidewire at an off-center position in the 1.5 T MR system. Power absorption produced by the resonating wire decreased as the repetition time was increased. No temperature rise was measured at 0.2 T. Considering the potential utility of low-field, open MR systems for MRI-guided endovascular interventions, it is important to be aware of the safety of such applications.     

Multiple cerebral aneurysms associated with Takayasu arteritis successfully treated with coil embolization

The cerebrovascular complications of Takayasu arteritis are primarily related to the presence of occlusive lesions. Cerebral aneurysms rarely occur as complications; only 18 cases have been reported thus far. The use of coil embolization to treat cerebral aneurysms occurring as a complication of Takayasu arteritis has not been previously reported. We report a case of Takayasu arteritis with a basilar tip aneurysm and a P1 segment aneurysm of the left posterior cerebral artery that were successfully treated with coil embolization. Because coil embolization for cerebral aneurysms associated with Takayasu arteritis requires the use of limited access routes that have extremely curved and tortuous courses, catheter navigation was difficult. The guide catheter, microcatheter, and guidewire must be selected and navigated with greater care than is usually required for common aneurysm embolization.     

Real-time 3D position reconstruction of guidewire for monoplane X-ray

We present a novel real-time method for the 3D reconstruction of the guidewire using a monoplane X-ray. The method consists of two steps: (1) the backprojection step to reconstruct a 3D surface that contains the guidewire and (2) the optimization step to select a curve on the surface that is the best match under the pre-specified constraints. The proposed method utilizes a priori knowledge in the form of a volume that indicates positions of the blood vessels and thus restricts the reconstruction. The reconstruction precision is limited by the local thickness of the vessels. The method is quantitatively evaluated on five phantom datasets and qualitatively on two patient datasets. For the phantom datasets the average reconstruction error is resolution limited to 1–2 voxels and is biased in the depth direction. The worst-case reconstruction error for any point, including the guidewire tip, is not larger than the local vessel thickness. A visual inspection of results for the patient datasets shows the guidewire is always placed in the proper vessel and is aligned with the 2D image, which is sufficient for the guidewire navigation. The developed implementation achieves the processing speed of 12 fps using Core™i7 CPU 920 at 2.67 GHz.     

Safety and Efficacy of Target Vessel Catheterization with the New Steerable Microcatheter Direxion Compared with a Standard Microcatheter: A Prospective,Preclinical Trial

Purpose

To assess the potential of a steerable microcatheter in a comparative preclinical trial.

Methods

A total of 100 small target vessels of the lower limbs with a maximum diameter of 3 mm were prospectively randomized to catheterize with either the preshaped torqueable Direxion? (J tip shape; Boston Scientific, Natick, MA) or a similarly steam-shaped Renegade? microcatheter (Boston Scientific) in a porcine model. Catheterization was first performed in combination with a microguidewire and afterwards without.

Results

No significant differences were found for the mean vessel diameter in the Direxion (1.53 ± 0.44 mm; n = 50) or Renegade (1.62 ± 0.43 mm; n = 50; p = 0.35) group. Guidewire-assisted catheterization was successful in all target vessels, whereas access was achieved in most cases with the guidewire alone. However, when it became necessary to steer the Direxion actively, this was regarded as key to obtain vessel access in three of four target vessels (75 %). Vessel catheterization without guidewire was significantly more successful with the Direxion (88 %; n = 44) compared with the Renegade (32 %; n = 16; p < 0.0001). In addition, this catheterization technique was also significantly faster with the Direxion compared with guidewire-assisted vessel catheterization with the Renegade (16.1 ± 14.4 sec compared with 27.1 ± 24.7 sec; p = 0.011).

Conclusions

The Direxion microcatheter demonstrated unique steerability characteristics, which makes it a promising new tool especially for complex coaxial endovascular procedures.     

Microguidewire protection of wide-necked aneurysms incorporating orifices of tortuous acute-angled vessels: a novel approach

Introduction

Protective/remodeling techniques for treating wide-necked intracranial aneurysms are constantly sought. However, their utility may be limited in lesions that incorporate the orifice of acute-angled efferent branch vessels. Furthermore, passage of a protective microcatheter may be challenging if a small branch is extremely tortuous. This study was conducted to explore a novel method of treating wide-necked aneurysms, utilizing microguidewire protection.

Methods

A microcatheter is first passed into parent artery (proximal to aneurysm) to position a microguidewire proximally in the involved branch. A second microcatheter is then inserted into aneurysmal sac. Advancement of the first microcatheter forces the microguidewire to shift, thus covering aneurysmal neck. A framing coil may then be placed within aneurysmal sac, under microguidewire protection. After completing initial coil insertion, easing of tension on the microcatheter allows separation of protective microguidewire and frame coil, confirming stability of the initial coil.

Results

This technique was applied to 11 intracranial saccular aneurysms of M1 segment (n?=?6), middle cerebral artery bifurcation (n?=?4), and anterior communicating artery (n?=?1) with success, combining stent protection in two patients. Coil embolization was thus facilitated, resulting in excellent outcomes for all patients. No morbidity or mortality was directly related to microguidewire protection.

Conclusion

Our small study suggests that microguidewire protection may be a safe alternative, if traditional remodeling or protective options are infeasible due to intrinsic vascular properties. This technique is particularly suited for treatment of wide-necked aneurysms where passage of protective microcatheters into involved branches is not achievable.     

导丝成袢技术在慢性长段股腘动脉闭塞病变开通中的应用

目的 探讨导丝成袢技术治疗慢性长段股腘动脉完全闭塞病变的技术要点和疗效.方法把导丝头端塑成一个U型袢,顺势用该袢开通闭塞血管病变,并逐步跟进导管,使导丝进人流出道真腔内.结果 52例股腘动脉长段(≥10 cm)闭塞患者中48例采用该技术成功地开通闭塞的股腘动脉,技术成功率92.3%;3例开通失败,1例无法开通.结论导丝成袢技术治疗长段股腘动脉闭塞病变可行性强、疗效显著、安全性良好、技术相对简便.     

Heating around intravascular guidewires by resonating RF waves

We examined the unwanted radiofrequency (RF) heating of an endovascular guidewire frequently used in interventional magnetic resonance imaging (MRI). A Terumo guidewire was partly immersed in an oblong saline bath to simulate an endovascular intervention. The temperature rise of the guidewire tip during an FFE sequence [average specific absorption rate (SAR) = 3.9 W/kg] was measured with a Luxtron fluoroscopic fiber. Starting from 26 degrees C, the guidewire tip reached temperatures up to 74 degrees C after 30 seconds of scanning. Touching the guidewire may cause sudden heating at the point of contact, which in one instance caused a skin burn. The excessive heating of a linear conductor like the guidewire can only be explained by resonating RF waves. The capricious dependencies of this resonance phenomenon on environmental factors have severe consequences for predictability and safety guidelines.     

微导丝成襻技术在外周动脉小角度插管中的应用

目的探讨微导丝成襻技术在动脉小角度插管中的应用价值。方法将微导丝成U襻,同时回拉导管及导丝,当微导丝头进入目标血管,继续同时缓慢回拉微导丝及微导管,使微导丝进入足够长度,随后将微导管缓慢送入目标血管。结果应用该项技术21例,成功18例,并顺利完成了插管,成功率达到86%,无并发症。结论常规方法超选小角度动脉插管失败后,使用微导丝成襻技术是十分有效的方法。     

Shapability, memory, and luminal changes in microcatheters after steam shaping: a comparison of 11 different microcatheters

PURPOSE: The purpose of this study was to compare the characteristics of shaped microcatheters, including shapability, durability, and luminal changes. MATERIALS AND METHODS: Eleven brands of steam-shaped microcatheters and one brand of preshaped microcatheter were evaluated. There were 2 nonreinforced and 10 reinforced devices supported by coils. For evaluation of shapability, the tip angle of 6 samples of each brand were measured after steam-shaping for 20 seconds with a shaping mandrel bent at a 90 degrees or 150 degrees angle. The ability to maintain the shaped angle after guidewire insertion stress (durability) was compared by calculation of the change in the tip angle by using 3 samples of each brand. Luminal change after steam shaping was evaluated by calculation of narrowing rate of the smallest diameter and observation of the surface morphology of the mold of each catheter lumen by using a silicone polymer by means of a fluorescent projection method. RESULTS: The nonreinforced microcatheters and the fiber-braided microcatheter showed higher shapability than the others. The degree of distal microcatheter straightening with the microguidewire insertion was less pronounced in the preshaped microcatheter and the fiber-braided microcatheter. Spontaneous recovery to the initial tip angle 5 minutes after the guidewire procedure was observed in 10 brands to various degrees (87%-98%). Irregular luminal surface morphology at the angled portion was found in 6 reinforced brands. One nonreinforced catheter and the fiber-braided catheter showed high narrowing rates >6%. CONCLUSION: There are differences in shapabilty, durability, and luminal changes of steam shaping in 12 brands of microcatheters. These characteristics could be important factors in catheter choice for endovascular procedures.     

A polymer-based MR-compatible guidewire: a study to explore new prospects for interventional peripheral magnetic resonance angiography (ipMRA)

PURPOSE: To introduce a newly developed polymer-based and magnetic resonance (MR)-compatible guidewire and to explore its capabilities with respect to interventional peripheral magnetic resonance angiography (ipMRA) in a flow phantom. MATERIALS AND METHODS: The guidewire is based on a polyetheretherketone (PEEK) polymer core, and small iron particles are embedded in its coating. A passive device tracking technique was designed utilizing a susceptibility artifact induced by the wire in images acquired with a balanced steady-state free precession (b-SSFP) sequence using small flip angles. The position of the guidewire tip was determined from image intensity maxima and overlayed onto a roadmap in near real-time. Guidewire tracking and balloon angioplasty of an artificial stenosis were attempted in two configurations of a flow phantom. RESULTS: Successful passive guidewire tracking was performed for all phantom configurations. Robustness and accuracy of the tracking technique were sufficient for phantom studies. A balloon catheter was placed into the stenosis using the guidewire under complete MR guidance, and subsequent balloon angioplasty yielded improved flow conditions. CONCLUSION: The new guidewire is well-suited for clinical application due to an absence of the risk of core fracture and its atraumatic flexible tip. It opens novel prospects for the realization of ipMRA in humans that need to be explored in further studies.     

经皮腔内外周动脉旋磨血管成形术

报告2例下肢动脉狭窄硬化性病变用经皮腔内旋磨切除血管成形的结果，旋磨是将旋磨器沿微导丝送至血管狭窄处，以190000r/min的高速转移，利用转孔器前的金钢砂将硬化病灶研碎而使血管形成光滑的内腔，恢复肢体组织的血供，我们使用了3mm旋磨器对6段狭窄成功地进行旋磨血管成形，近期疗效明确，此方法尤其对已钙化的狭窄病灶及球囊所不能达到的小动脉病灶具有明显的优势。     

Recanalization by mechanical embolus disruption during intra-arterial thrombolysis in the carotid territory

BACKGROUND AND PURPOSE: Mechanical disruption of a clot with a microcatheter and a guidewire has not been detailed in conjunction with intra-arterial thrombolysis in patients with acute ischemic stroke. The purpose of this study was to evaluate the efficacy of mechanical disruption of an embolus in the carotid artery distribution. METHODS: We analyzed clinical and radiologic findings and functional outcomes 3 months after thrombolysis with mechanical disruption. Outcomes were classified as good for modified Rankin scale (mRS) scores of 0-2, moderate for mRS scores of 3, and poor for death and mRS scores of 4 or 5. RESULTS: Twenty-three consecutive patients with severe hemispheric symptoms were treated with several methods of mechanical embolus disruption during the intra-arterial administration of urokinase. Twelve patients had occlusions of the proximal middle cerebral artery (MCA), and 11 had occlusions of the distal internal carotid artery (ICA). Recanalization was observed in all patients with MCA occlusions and in 10 (91%) with ICA occlusions. Outcomes were good in nine patients (75%) with MCA occlusions and in four (36.4%) with ICA occlusions. Early management of vessel perforation, caused by a microguidewire tip in two patients, resulted in early hemostasis. Neither patient had a major deficit attributable to the complication. CONCLUSION: A high incidence of recanalization and clinical improvement can be observed in patients with occlusions of not only the proximal MCA but also the distal ICA. This method might be an effective additional option to intra-arterial thrombolysis for acute distal ICA and proximal MCA occlusions.     

Vascular guide wire navigation with a magnetic guidance system: experimental results in a phantom

PURPOSE: To investigate the efficacy of a second-generation prototype magnetic guidance system in complex vessel phantoms versus conventional navigation in simulated interventional radiology procedures and to analyze procedure and fluoroscopy times. MATERIALS AND METHODS: The magnetic guidance system consists of two focused-field permanent magnets on each side of the body that create a 0.1-T navigation field and is integrated with a modified C-arm single-planar digital angiography system. Forty-nine navigations in a glass phantom and 80 navigations in a three-dimensional liver phantom were performed with a magnetically tipped floppy 0.014-inch guide wire and a conventional 0.014-inch microcatheter system. Rates of success and fluoroscopy and procedure times were quantified for both techniques. For the liver phantom experiment, the Mann-Whitney U test was used. For the glass phantom experiment, the Wilcoxon matched pair test was used with the Hodges-Lehmann estimator. RESULTS: In the glass phantom experiments, 42 of 49 turns were successfully performed with both methods. Procedure time to reach a target did not differ significantly between methods, while fluoroscopy time was significantly different when compared with that of the magnetic guidance system (P <.01). Navigation in the liver phantom was successful in 80 of 80 turns with the magnetic guidance system and in 76 of 80 turns with conventional navigation. With the support of the magnetic guidance system, procedure time and fluoroscopy time were significantly different from those with conventional navigation (P <.001). CONCLUSION: The magnetic guidance system allows the precise navigation of a magnetic guide wire in complex vessel phantoms with significantly shorter fluoroscopy and procedure times.     

复合手术室智能移动三维导航技术在近肾型腹主动脉瘤腔内治疗中的应用效果评价

目的：探讨复合手术室术中智能移动三维导航技术在近肾型腹主动脉瘤腔内治疗中的应用价值。 方法：选取2016年2月-2018年6月在江苏省苏北人民医院复合手术室治疗的7例近肾型腹主动脉瘤患者,术中行数字减影血管造影三维成像（3D-DSA）后将3D重建图像和2D透视图像进行图像融合,标记肾动脉及其他重要血管分支。并对不同阶段不同体位的术中三维导航融合图像进行自动修正配准,根据手术需要,改善融合图像的血管、骨骼背景密度,提高叠加图像上血管可视化程度,精确指导支架释放,实现血管内治疗的准确导航。 结果：7例患者在3D图像导航下行血管腔内腹主动脉瘤修复术,导丝导管均成功导入靶血管内,单根靶血管导入时间3~22 min,造影剂用量150~180 ml。7例行血管腔内腹主动脉瘤修复术均手术成功,术后即刻造影提示分支血管显影通畅,无内漏。 结论：复合手术室三维导航技术可精准标记肾动脉及其他分支血管开口,方便术中靶血管定位超选,对近肾型腹主动脉瘤腔内治疗具有重要的指导作用。     

Evaluation of magnetic navigation in an in vitro model of uterine artery embolization

PURPOSE: To compare steering of a novel magnetic guide wire with a standard 0.014-inch guide wire within a vascular phantom. MATERIALS AND METHODS: The magnetic guiding system (MGS) was composed of two permanent magnets on each long side of the fluoroscopy table generating a 0.1-T magnetic field, and a C-arm angiography system. The magnetic field was created according to vectors drawn onto two radiographic projections. Consequently, the tip of the intravascular guide wire containing a permanent magnet was deflected parallel to the magnetic field. Ninety-six catheterizations were performed in water-filled polyvinyl chloride tubes imitating the arterial tree of a female pelvis. This vascular phantom resembled a total of 12 uterine arteries with three different calibers (inner diameters: 1.1 mm, 1.7 mm, and 4.2 mm). Fluoroscopy and procedure times were measured to compare magnetic-assisted and conventional catheterization. RESULTS: Catheterization to every predefined target was successful for all attempts with both guiding techniques. The fluoroscopy time during magnetic navigation was significantly shorter in vessels of all three sizes compared with conventional navigation (means of 19.6 sec, 5.9 sec, and 4.8 sec vs. 48.8 sec, 49.8 sec, and 32.7 sec for small, medium, and large vessels, respectively; P < .05). Procedure times with use of the magnetic guide wire (149.6 sec, 52.1 sec, and 39.9 sec) were not significantly different than those with conventional navigation (60.4 sec, 68.6 sec, and 47.7 sec). CONCLUSIONS: The MGS enables exact endovascular navigation with shorter fluoroscopy time in an in vitro model. The MGS may offer opportunities to reduce x-ray exposure to patients and staff.     

Invited. Visualization of MR-compatible catheters by electrically induced local field inhomogeneities: Evaluation in vivo

The purpose of this study was to assess the feasibility of a newly developed field inhomogeneity catheter for interventional MRI in vivo. Different prototypes of a field inhomogeneity catheter (pigtail and multipurpose configuration, balloon catheters) were investigated in pigs. The catheters were introduced in Seldinger technique via the femoral vessels over a guidewire on an interventional MR system (Philips Gyroscan NT combined with a C-arm fluoroscopy unit [Philips BV 212]). Catheters were placed in veins and arteries. The catheter position was controlled by a fast gradient-echo sequence (turbo field echo [TFE]). Catheters were introduced over a guidewire without complications in all cases. Using the field inhomogeneity concept, catheters were easily visualized in the inferior vena cava and the aorta by the fast gradient-echo technique on MR in all cases. Although aortic branches were successful cannulated, the catheters were not well displayed by the TFE technique due to the complex and tortuous anatomy. All animals survived the experiments without complications. MR-guided visualization of a field inhomogeneity catheter is a simple concept that can be realized on each MR scanner and may allow intravascular MR-guided interventions in future.     

Active MR visualization of a vascular guidewire in vivo

The purpose of this study was development of an actively visualized .035-inch vascular guidewire for use in MR-guided interventions. The guidewire was actively visualized by inclusion of a 6-cm-long radiofrequency coil in its tip. A high contrast outline of the distal tip of the guidewire was obtained by acquiring an image with the radiofrequency coil as the receiving antenna. The position of the guidewire relative to the surrounding anatomy was determined by overlaying the guidewire image on a previously acquired road map. The guidewire was evaluated in vivo in the abdominal vessels of a rabbit and swine at 1.5 T. The built-in radiofrequency coil delivered a high contrast signal over its full length, enabling visualization of the position and curvature of the tip of the guidewire. The ability to see the curvature of the guidewire over several centimeters significantly eased manipulation into targeted vessels and represents an important advance toward MR-guided vascular interventions.