Endovascular Magnetic Catheter for Interventional MRI

描述（由申请人提供）：本项目的总体目标是开发一种新型微创医疗器械：一种在血管内介入磁共振成像（MRI）环境中使用的远程磁控工作原型导管。 几个主要的公共卫生威胁，包括缺血性中风，脑动脉瘤，实体瘤，动脉粥样硬化和心律失常，目前诊断和治疗血管内的X射线荧光镜引导下。虽然X射线透视具有高空间和时间分辨率，但它仅可视化血管，而不是最终由这些血管供应的软组织和器官。X射线透视使用电离辐射，大剂量的电离辐射可能对患者和医疗保健提供者产生有害影响; MRI不使用电离辐射。 在MRI引导下进行血管内手术是不断发展的介入MRI领域的关键应用。 近年来已经开发了快速而高分辨率的MR成像技术，允许与X射线荧光透视法实现的帧率相当的帧率。在MRI下进行手术允许在介入期间使用广泛的MR解剖和生理成像技术：弥散加权成像以评估组织梗死，灌注成像以评估器官血流，高分辨率解剖成像以可视化插入导管的血管周围和下游的组织。具有这样的MRI信息可以帮助指导介入医生关于何时已经实现期望的治疗结果或者何时已经发生不期望的手术并发症的决定，而在X射线引导下，诸如灌注和梗塞的参数只能被推断。如果可以在MRI引导下进行血管介入，则可以使用真实的时间生理MR成像来增强术中决策，从而可能允许新患者接受血管内治疗并改善临床结局。 除了MRI的成像优势外，MRI扫描仪内部的强均匀磁场（B 0）为通过远程控制进行导管头端导航提供了独特的机会。如果通过向导管头端上的铜线圈施加小电流在导管头端上产生微小磁矩，则导管头端将移动以与MRI扫描仪的孔对齐（B 0场的方向）。如果一个这样的线圈被放置在导管尖端处，则其可以通过远程控制在一个平面中偏转，或者通过医师的手转动以在另一个平面中偏转。如果三个这样的线圈被放置在导管尖端上，则即使没有介入医生的手，也可以在三维中实现远程控制的偏转。该技术可能允许更好地导航目前难以插入导管的小而曲折的血管，因为股动脉穿刺部位和靶血管之间的许多血管弯曲处存在摩擦力。提供给导管线圈的低水平电流还允许导管头端的主动可视化，否则在MR环境中可能难以看到导管头端。 我们之前开发了一种激光车床光刻技术，用于合成在多达三个正交轴上带有铜线圈的导管。我们使用实时MRI技术来可视化导管头端，并在临床MRI扫描仪中导航简单的血管体模。我们在体外和体内测量了导管及其周围的加热。我们还推导并验证了方程，以表征导管线圈几何结构、施加电流、导管刚度、磁场强度和所得导管头端偏转之间的关系。在这个新的建议中，我们将建立在早期的研究与以下具体目标：1。具体目标1：优化导管管身和头端设计，以改善功能; 2.具体目标2：评价MR成像策略，以优化导管可视化并最大限度地减少伪影; 3.具体目标3：在1.5 T和3.0 T MRI环境中进行导管导航和体外成像试验; 4.具体目标4：在1.5 T下评价动物模型中的体内导管导航和成像; 5.具体目标5：在1.5 T下评估导管安全性; 6.具体目标6：在关键MR引导介入的动物模型中评估导管系统的性能：溶栓（用于急性缺血性卒中治疗）和颗粒栓塞用于受控组织梗死（用于肿瘤治疗）。 在拟定项目期结束时，磁性导管系统将成为一种可行的器械，可用于提高在MR环境中进行介入的速度和有效性。因此，它将彻底改变将受益于血管内治疗期间的真实的实时生理组织监测的疾病的临床治疗。

DESCRIPTION (provided by applicant): The overall goal of this project is to develop a new minimally invasive medical device: a working prototype catheter that is remotely magnetically controlled for use in the endovascular interventional magnetic resonance imaging (MRI) environment. Several major public health threats, including ischemic stroke, brain aneurysm, solid tumors, atherosclerosis, and cardiac arrhythmias are currently diagnosed and treated endovascularly under x-ray fluoroscopic guidance. Although x-ray fluoroscopy has high spatial and temporal resolution, it only visualizes blood vessels as opposed to the soft tissues and organs ultimately supplied by those blood vessels. Whereas x-ray fluoroscopy uses ionizing radiation, which in large doses can have deleterious effects both on patients and health care providers; MRI does not use ionizing radiation. Performing endovascular procedures under MRI guidance is a key application of the growing field of interventional MRI. Fast yet high resolution MR imaging techniques have been developed in recent years, allowing frame rates comparable to those achieved with x-ray fluoroscopy. Performing procedures under MRI allows use of the wide array of MR anatomic and physiologic imaging techniques during an intervention: diffusion weighted imaging to evaluate for tissue infarction, perfusion imaging to assess for organ blood flow, high resolution anatomic imaging to visualize tissues surrounding and downstream from a catheterized blood vessel. Having such MRI information can help guide the interventional physician's decisions as to when a desired therapeutic result has been achieved or when an undesired procedural complication has occurred, whereas under x-ray guidance, parameters such as perfusion and infarction can only be inferred. If vascular interventions can be performed under MRI guidance, then real time physiologic MR imaging can be used to augment intraprocedural decision making, potentially allowing new patients to receive endovascular therapy and improving clinical outcomes. In addition to the imaging advantages of MRI, the strong homogeneous magnetic (B0) field inside the MRI scanner provides a unique opportunity for catheter tip navigation by remote control. If a tiny magnetic moment is created on the tip of the catheter by application of a small electrical current to copper coils on the catheter tip, then the tip of the catheter will move to align with the bore of the MRI scanner (the direction of the B0field). If one such coil is placed at the catheter tip, it can be deflected in one plane by remote control or turned by the practitioner's hand to deflect in another plane. If three such coils are placed on the catheter tip, then remote controlled deflection can be achieved in three dimensions even without the hand of the interventionalist. This technology potentially will allow better navigation of small, tortuous blood vessels that are currently difficult to catheterize due to build-up of friction at the many vascular bends between the femoral access site and the target blood vessel. Low levels of current supplied to the catheter coils also permits active visualization of the catheter tip, which otherwise can be difficult to see in the MR environment. We previously developed a laser lathe lithography technique to synthesize catheters tipped with copper coils in up to three orthogonal axes. We used real-time MRI techniques to visualize the catheter tip and navigate simple vascular phantoms in a clinical MRI scanner. We measured heating within the catheter and its surroundings both in vitro and in vivo. We also derived and validated equations to characterize the relationship between catheter coil geometry, applied current, catheter stiffness, magnetic field strength, and resulting catheter tip deflections. In this new proposal, we will build upon earlier research with the following specific aims: 1. Specific Aim 1: Refine catheter shaft and tip design to improve functionality; 2. Specific Aim 2: Evaluate MR imaging strategies to optimize catheter visualization and minimize artifacts; 3. Specific Aim 3: Test catheter navigation and imaging in vitro in the 1.5 T and 3.0 T MRI environments; 4. Specific Aim 4: Evaluate in vivo catheter navigation and imaging in animal models at 1.5 T; 5. Specific Aim 5: Assess catheter safety at 1.5 T; 6. Specific Aim 6: Assess the performance of the catheter system in animal models of key MR-guided interventions: thrombolysis (as for acute ischemic stroke treatment) and particulate embolization for controlled tissue infarction (as for tumor treatment). At the end of the proposed project period, the magnetic catheter system will be a viable device for improving the speed and efficacy of interventions performed in the MR environment. It thus will stand to revolutionize the clinical treatment of diseases that would benefit from real time physiologic tissue monitoring during endovascular therapy.