Innovative Technology for MRI Guided Procedures

MRI 引导程序的创新技术

• 批准号: 9357245
• 负责人: Michael Hansen
• 金额: $ 82.93万
• 依托单位: NATIONAL HEART, LUNG, AND BLOOD INSTITUTE
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/9357245
• 关键词: Cardiac Surgery procedures; Cardiology; Catheters; Characteristics; Collaborations; Computer software; Data Set; Deposition; Development; Devices; Diagnostic; Diagnostic radiologic examination; Dose; Feedback; Foundations; Goals; Heart; Heating; Image; Imaging Techniques; Imaging technology; Ionizing radiation; Laboratories; Lead; Magnetic Resonance Imaging; Malignant Neoplasms; Metals; Myocardium; Patients; Procedures; Radiation; Research Infrastructure; Resolution; Risk; Roentgen Rays; Running; Safety; Signal Transduction; Speed; Structure; System; Techniques; Therapeutic; Time; Tissues; United States National Institutes of Health; Work; absorption; contrast imaging; design; image guided; imaging modality; imaging system; innovative technologies; instrument; instrumentation; interest; magnetic field; minimally invasive; myocardial biopsy; novel; novel strategies; radio frequency; radiofrequency; reconstruction; response; soft tissue; structural heart disease; tool

Background Image guided, minimally invasive procedures are an important diagnostic and therapeutic tool in cardiology. Many procedures that required open heart surgery in the past can now be performed percutaneously. The preferred imaging modality is current practice is X-ray flouroscopy. This technique has high spatial resolution and a high frame rate very suitable for real-time image guidance. However, X-ray flouroscopy has come significant drawbacks. The soft tissues (e.g. the cardiac muscle) are not well visualized on X-ray images, which hampers guidance of procedures such as myocardial biopsy. It also exposes the patient the significant doses of ionizing radiation. Many patients with structural heart disease have several procedures in their lives and the cumulative radiation dose, with ensuing risk of developing cancer, can be substantial. As a consequent of the shortcomings of X-ray guided procedures, there is great interest in using MRI as image guidance. MRI provides superior soft tissue contrast and does not expose the patient to radiation risk, but there are other challenges associated with the use of MRI for interventional image guidance. In the Laboratory of Imaging Technology we are focused on the two main challenges; imaging speed and imaging safety, which are, to some extend related. MRI is an inherently slow technique compared to X-ray flouroscopy. It can take seconds to acquire a single image, which is obviously too slow. To compensate for this we acquire undersampled datasets and apply novel reconstruction techniques in real-time to achieve good frame rates. The imaging sequences we use have been modified to allow interactive control of many sequence parameters that control image orientation, frame rate, and contrast. An important aspect of interventional procedures is that long metal devices (wires and catheters) are introduced into the patient to reach a particular target (e.g., in the heart). These long conducting structures can heat up significantly due to the radiofrequency energy deposited by the MRI acquisition. This device heating can cause tissue damage and is an important safety issue associated with current interventional MRI procedures. We aim mitigate this device heating problem (thus enabling the field of interventional MRI) by developing imaging sequences and instruments that deposit less radiofrequency radiation in the patient. Goals/Objectives The specific goals of this project are: 1. Develop low Specific Absorption Rate (SAR) sequences that can be used for real-time imaging. 2. Develop techniques that can visualize passive devices. 3. Develop device heating feedback systems that can regulate SAR in response to device heating. 4. Design new MRI systems that are less prone to device heating. Progess in fiscal year 2016 The key to lowering the device heating is to deposit less radiofrequency energy in the patient while imaging. Our first approach to this was to develop sequences and infrastructure that allow us to run with much lower radiofrequency duty cycle. Our techniques include spiral imaging with long readouts, which can lower the heating significantly. To make the image quality adequate it is necessary to perform corrections for gradient imperfections. We now have such technqiues working in real-time. We have also taken inital steps to develop an MRI system that uses less radio frequency energy. The key to this is lowering the magnetic field. The energy deposited in the patient is proportional to the field strength squared and we propose lowering the field to about 1/3 of the current field strengths, i.e., to use a 0.5T magnet instead of the current 1.5T magnet. In the previous year we have made significant progress on the theoretical foundations of such a system. In particular we have explored what sequences could be used to preserve much of the signal while lowering the field strength. This theoretical work will lead to design specifications for a new system in the coming year. The laboratory has also contributed to the dissemination of new imaging techniques developed at the NIH. In collaboration with Siemens, we have contributed to the development of a works in progress (WIP) package for interventional MRI. This new package includes features developed at the NIH that allow interactive control of imaging contrast and imaging speed. The WIP package works with out Gadgetron (https://gadgetron.github.io) software package.

背景 图像引导的微创手术是心脏病学中重要的诊断和治疗工具。许多过去需要心脏直视手术的程序现在可以在心脏直视手术中进行。当前实践中首选的成像方式是X射线荧光镜检查。该技术具有高空间分辨率和高帧率，非常适合于实时图像制导。然而，X射线荧光镜检查有明显的缺点。软组织（例如心肌）在X射线图像上不能很好地可视化，这妨碍了对诸如心肌活检的程序的引导。它还使患者暴露于大量的电离辐射。许多患有结构性心脏病的患者在他们的生活中经历了几次手术，累积的辐射剂量以及随之而来的癌症风险可能很大。由于X射线引导过程的缺点，人们对使用MRI作为图像引导非常感兴趣。 MRI可提供上级软组织对比度，不会使患者暴露于辐射风险，但使用MRI进行介入图像引导还存在其他挑战。在成像技术实验室，我们专注于两个主要挑战：成像速度和成像安全性，这在某种程度上是相关的。与X射线荧光镜检查相比，MRI是一种固有的缓慢技术。获取单个图像可能需要几秒钟，这显然太慢了。为了弥补这一点，我们采集欠采样数据集，并实时应用新的重建技术，以实现良好的帧速率。我们使用的成像序列已被修改，以允许交互式控制许多序列参数，控制图像方向，帧速率和对比度。介入过程的一个重要方面是将长金属装置（线和导管）引入患者体内以到达特定目标（例如，在心中）。由于MRI采集所沉积的射频能量，这些长传导结构可能会显著升温。该器械发热可能导致组织损伤，并且是与当前介入性MRI手术相关的重要安全性问题。我们的目标是通过开发在患者体内存款较少射频辐射的成像序列和仪器来缓解该器械发热问题（从而实现介入MRI领域）。 目标/目的 该项目的具体目标是： 1.开发可用于实时成像的低比吸收率（SAR）序列。 2.开发可以可视化无源设备的技术。 3.开发器械产热反馈系统，可调节SAR以响应器械产热。 4.设计不易于器械发热的新MRI系统。 2016财年进展 降低器械发热的关键是在成像时在患者体内存款更少的射频能量。我们的第一个方法是开发序列和基础设施，使我们能够以低得多的射频占空比运行。我们的技术包括具有长读数的螺旋成像，这可以显着降低发热。为了使图像质量足够，有必要对梯度缺陷进行校正。我们现在有这样的技术在实时工作。 我们还采取了初步措施，开发一种使用更少射频能量的MRI系统。关键是降低磁场。沉积在患者体内的能量与场强的平方成比例，我们建议将场强降低到当前场强的约1/3，即，使用0.5T磁体代替当前的1.5T磁体。去年，我们在这一制度的理论基础方面取得了重大进展。特别是，我们已经探索了可以使用什么序列来保留大部分信号，同时降低场强。这项理论工作将导致明年新系统的设计规格。 该实验室还促进了NIH开发的新成像技术的传播。我们与西门子公司合作，为开发用于介入性MRI的正在进行的工作（Work-in-progress）包做出了贡献。这个新的软件包包括NIH开发的功能，允许交互式控制成像对比度和成像速度。该软件包与Gadgetron（https：//www.example.com）软件包配合使用。gadgetron.github.io