Endovascular Magnetic Catheter for Interventional MRI

描述(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：一种可远程磁控的工作原型导管，用于血管内介入性磁共振成像(MRI)环境。目前，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，都是在X射线透视引导下进行血管内诊断和治疗的。虽然x射线透视具有很高的空间和时间分辨率，但它只显示血管，而不是最终由这些血管供应的软组织和器官。而x射线透视使用的是电离辐射，大剂量的电离辐射可能会对患者和医疗保健提供者产生有害影响；磁共振成像不使用电离辐射。在MRI引导下进行血管内手术是日益增长的介入MRI领域的一个关键应用。近年来，快速而高分辨率的磁共振成像技术得到了发展，使帧速率可以与X射线荧光透视相媲美。在MRI下进行手术，可以在介入过程中使用广泛的MR解剖和生理成像技术：扩散加权成像评估组织梗塞，灌注成像评估器官血流，高分辨率解剖成像可视化插管血管周围和下游的组织。拥有这样的MRI信息可以帮助指导介入医生关于何时达到期望的治疗结果或何时发生不希望看到的程序并发症的决定，而在X射线引导下，只能推断血流灌注和脑梗塞等参数。如果血管介入可以在MRI指导下进行，那么可以使用实时生理学MR成像来增强术中决策，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扫描仪内部的强均匀磁场(B0)为遥控导航导管尖端提供了独特的机会。如果通过向导管末端的铜线圈施加小电流而在导管末端产生微小的磁矩，那么导管末端将移动以与MRI扫描仪的内径(B0field的方向)对齐。如果一个这样的线圈被放置在导管尖端，它可以通过遥控器在一个平面上偏转，或者由医生的手转动以在另一个平面上偏转。如果在导管末端放置三个这样的线圈，那么即使不需要干预者的手，也可以实现远程控制的三维偏转。这项技术可能会更好地导航目前难以插管的小而曲折的血管，因为在股骨入口处和目标血管之间的许多血管弯曲处积累了摩擦。提供给导管线圈的低水平电流还允许主动显示导管尖端，否则在磁共振环境中很难看到。我们之前开发了一种激光车床光刻技术，用于合成最多三个垂直轴上带有铜线圈的导管。我们使用实时核磁共振技术在临床核磁共振扫描仪中可视化导管尖端并导航简单的血管模型。我们在体外和体内测量了导管及其周围的热量。我们还推导并验证了描述导管线圈几何形状、施加电流、导管硬度、磁场强度和由此产生的导管尖端偏转之间的关系的方程。在这个新的提案中，我们将以先前的研究为基础，以下列具体目标为基础：1.具体目标1：改进导管的轴和尖端设计以提高功能性；2.具体目标2：评估磁共振成像策略，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1.5T和3.0 T的MRI环境中测试导管导航和体外成像；4.具体目标4：在1.5T的动物模型中评估导管导航和成像；5.具体目标5：评估1.5T下的导管安全性；6.具体目标6：在MR引导的关键干预措施的动物模型中评估导管系统的性能：溶栓(用于急性缺血性中风治疗)和颗粒栓塞术(用于控制组织梗塞)(用于肿瘤治疗)。在拟议项目期结束时，磁导管系统将成为提高磁共振环境中实施干预的速度和效果的可行装置。因此，它将为疾病的临床治疗带来革命性的变化，这些疾病将受益于血管内治疗期间的实时生理组织监测。 公共卫生相关性：在美国，中风、癌症和心血管疾病是导致死亡和残疾的主要原因，磁共振成像在这些疾病的诊断和评估中发挥着重要作用。该项目将开发的技术利用核磁共振扫描仪的磁性环境来操纵导管和治疗设备，从而将核磁共振转变为一种治疗方式和一种诊断方式。这最终可能导致针对几个主要致病和死亡原因制定更安全、更有效的治疗战略。

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. PUBLIC HEALTH RELEVANCE: Stroke, cancer, and cardiovascular disease are the major causes of death and disability in the United States and MRI plays an important role in the diagnosis and evaluation of these disorders. The technology to be developed in this project exploits the magnetic environment of the MRI scanner to manipulate catheters and therapeutic devices, thereby transforming MRI into a therapeutic modality as well as a diagnostic one. This could ultimately lead to safer and more efficacious treatment strategies for several major causes of morbidity and mortality.