Endovascular Magnetic Catheter for Interventional MRI

描述（由申请人提供）：该项目的总体目标是开发一种新的微创医疗设备：一种用于血管内介入磁共振成像（MRI）环境的远程磁控制的工作原型导管。几种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，目前在x线透视指导下进行血管内诊断和治疗。虽然x线透视具有很高的空间和时间分辨率，但它只能看到血管，而不是最终由这些血管供应的软组织和器官。鉴于x射线透视使用电离辐射，大剂量电离辐射会对患者和医护人员产生有害影响；核磁共振不使用电离辐射。在MRI引导下进行血管内手术是介入MRI领域不断发展的一个关键应用。近年来，快速而高分辨率的磁共振成像技术得到了发展，其帧率可与x射线透视技术相媲美。在MRI下执行程序允许在干预期间使用广泛的MR解剖和生理成像技术：扩散加权成像评估组织梗死，灌注成像评估器官血流，高分辨率解剖成像显示导管周围和下游的组织。有了这样的MRI信息，可以帮助指导介入医生决定何时达到预期的治疗效果，何时发生不希望的手术并发症，而在x线引导下，只能推断灌注和梗死等参数。如果血管介入可以在MRI引导下进行，那么实时生理MR成像可以用来增强术中决策，潜在地允许新患者接受血管内治疗并改善临床结果。除了MRI的成像优势外，MRI扫描仪内部强大的均匀磁场（B0）为远程控制导管尖端导航提供了独特的机会。如果通过对导管尖端的铜线圈施加小电流，在导管尖端产生微小的磁矩，那么导管尖端将移动到与MRI扫描仪的孔对齐（b0场的方向）。如果在导管尖端放置一个这样的线圈，它可以通过遥控在一个平面上偏转，或者由医生的手转动到另一个平面上偏转。如果在导管尖端放置三个这样的线圈，那么即使没有介入医师的手，也可以实现三维的远程控制偏转。这项技术有可能更好地引导小而弯曲的血管，这些血管目前很难插管，因为在股骨通路部位和目标血管之间的许多血管弯曲处存在摩擦。提供给导管线圈的低水平电流也允许导管尖端的主动可视化，否则在MR环境中很难看到。我们之前开发了一种激光车床光刻技术，可以在三个正交轴上合成带有铜线圈的导管。我们使用实时MRI技术来可视化导管尖端，并在临床MRI扫描仪中导航简单的血管幻象。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导管线圈几何形状、施加电流、导管刚度、磁场强度和导管尖端偏转之间关系的方程。在这个新的建议中，我们将以先前的研究为基础，具体目标如下：具体目标1：改进导管轴和尖端设计以提高功能；2. 具体目标2：评估MR成像策略以优化导管可视化并减少伪影；3. 专项目标3：在1.5 T和3.0 T MRI环境下测试导管导航和体外成像；4. 具体目标4：评估1.5 T时动物模型的体内导管导航和成像；5. 具体目标5：评估1.5 T导管的安全性；6. 具体目标6：评估导管系统在主要磁共振引导干预的动物模型中的性能：溶栓（用于急性缺血性卒中治疗）和颗粒栓塞（用于控制组织梗死（用于肿瘤治疗））。在项目结束时，该磁导管系统将成为一种可行的设备，用于提高在MR环境中进行干预的速度和有效性。因此，它将彻底改变疾病的临床治疗，将受益于血管内治疗期间的实时生理组织监测。

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.