Time-resolved whole-heart cardiac imaging using highly parallel magnetic resonance

我们研究项目的广泛目标是开发新技术来提高磁共振成像（MRI）的质量。我们的项目特别关注这与心脏和周围区域成像（心脏成像）的关系。MRI是一种安全的诊断工具，提供软组织器官的良好图像，通常用于静态结构（如大脑）的成像。然而，由于MRI对运动非常敏感，它尚未广泛用于心脏成像。心脏跳动的运动降低了图像质量，产生模糊和重影。当你在拍照的时候，有人移动也会产生类似的效果，尽管图像受到影响的数学原理是不同的。运动有两个独立的来源：心脏收缩（心脏跳动）和呼吸运动（呼吸）。有可能补偿与心脏收缩相关的运动，但呼吸不太可预测，因此更难补偿。因此，大多数心脏MRI研究都是在病人屏住呼吸的情况下进行的。当然，患者可以这样做的时间是有限的，因此图像的质量可能会受到影响。典型的心脏MRI检查需要多次屏气，并且必须非常仔细地计划以确保获得必要的图像。这种规划和随后的图像分析需要训练有素的工作人员，而大多数场址都没有这些人员。这是心脏MRI广泛应用的主要障碍之一。在本提案中，我们的目标是开发新的，更快，更简单的方法来获取心脏磁共振图像。我们的目标是通过用3D技术取代现有的2D方法来做到这一点。这种方法的优点是，整个心脏可以在一次采集期间成像，几乎不需要计划。为了实现这一目标，有必要克服一些与呼吸运动相关的问题，这样患者就可以在不屏住呼吸的情况下获得图像。在采集过程中，将测量由于呼吸引起的心脏运动，然后在形成图像时将这些运动测量结果考虑在内。我们将利用新的MRI扫描仪现在可以同时获取多个数据块（使用多个接收设备）这一事实（高度并行成像）。这可以加速采集，并提供有关运动的补充信息。这项新技术将在几个方面补充和促进我们的研究。例如，我们将收到更多关于运动对图像的影响的信息，从而使我们能够更好地纠正图像。在某些情况下，MR检查的总扫描时间有限。这包括在病人体内注射造影剂（染料）。为了最好地利用这种类型的扫描的可用时间，我们希望避免获取冗余信息。为了实现这一点，有必要依赖于心脏运动的先验信息，这可能会降低重建图像的质量。在这个提议中，我们希望研究如何减少对先验信息的依赖，这将涉及复杂的数学来确定先验信息和并行成像原理之间的最佳平衡。总之，本提案的目的是开发新的MR成像策略，允许在自由呼吸和时间限制下对心脏进行3D成像。开发的成像序列将在志愿者和患者身上进行测试。

The broad aim of our research project is to develop new techniques to improve the quality of Magnetic Resonance Imaging (MRI). Our project specifically looks at this in relation to imaging the heart and surrounding area (cardiac imaging). MRI is a safe diagnostic tool providing good images of soft tissue organs and is used routinely for the imaging of static structures such as the brain. However it is not yet widely used for cardiac imaging because MRI is very sensitive to motion. The movement of the beating heart reduces image quality producing blurring and ghosting. A similar effect occurs when someone moves while you are taking their photo, though the mathematics of how the image is affected is different. There are two independent sources of motion: the cardiac contraction (heart beating) and respiratory motion (breathing). It is possible to compensate for the motion associated with cardiac contraction, but respiration is less predictable and consequently harder to compensate. Most cardiac MRI studies are therefore done while the patient holds their breath. Naturally there are limits to how long patients can do this for and therefore the quality of the images can be compromised. A typical cardiac MRI exam requires multiple breath holds and it has to be planned very carefully to ensure that the necessary images are acquired. This planning and the subsequent image analysis require highly trained staff and these are not available at most sites. This is one of the main obstacles for the widespread use of cardiac MRI. In this proposal we aim to develop new, faster and easier ways of acquiring cardiac MR images. We aim to do this by replacing existing 2D methods with 3D techniques. The advantage of this approach is that the whole heart can be imaged during a single acquisition and very little planning is required. To achieve this it is necessary to overcome some of the problems associated with respiratory motion so that the images can be acquired without the patient having to hold their breath. During the acquisition process the motion of the heart due to respiration will be measured and these motion measurements will then be taken into account when forming the images. We will take advantage of the fact that new MRI scanners can now acquire multiple chunks of data (using multiple receive devices) at the same time ( highly parallel imaging ). This enables acceleration of the acquisition and it can provide complementary information about motion. This new technology will complement and facilitate our research in several ways. For example, we will be receiving more information about the effects of the motion on the image thus allowing us to better correct the images. In certain situations, there is a limited amount of overall scan time available for the MR examination. This includes acquisitions where a contrast agent (dye) is injected into the patient. In order to make the best use of the time available for this type of scan we want to avoid acquisition of redundant information. To accomplish this it is necessary to rely on prior information about the movement of the heart and this can potentially degrade the reconstructed images. In this proposal we wish to investigate how we can rely less on prior information, this will involve complicated mathematics to determine the optimal balance between prior information and parallel imaging principles.In summary, the purpose of this proposal is to develop new MR imaging strategies that allow 3D imaging of the heart during free-breathing and under time-constraints. The developed imaging sequences will be tested on both volunteers and patients.