SSFP Cardiovascular MR Imaging on 3.0T Using Unified-Coil Local Shimming

摘要 心血管疾病是全球主要的死亡原因。心血管磁共振（CMR） 常规用于心血管疾病的临床管理，并且是 评估心脏功能和心肌组织特性。今天，大多数临床CMR研究仍然是 在1.5T扫描仪上进行，因为它们在执行CMR协议时的可用性和鲁棒性。在 一般而言，3.0T提供了比1.5T更高的SNR、空间分辨率和更短的扫描时间。但 增加的B0场强也对CMR提出了技术挑战。一个主要的挑战是易感性或 由于B0场不均匀性恶化导致的非共振伪影。 在过去的二十年里，稳态自由进动（SSFP）彻底改变了1.5T上的CMR，因为它 与基于梯度回波的采集相比，可显著提高SNR和对比噪声比（CNR）。但其 尽管不断改进B0均匀性和匀场，但在3.0T上的常规使用不一致 能力的因此，仍然常规地使用基于梯度回波的采集，诸如用于电影成像， 心脏舒张测量和冠状动脉MRA，否定了3.0T用于CMR的主要优势。由于距离 标准的全身匀场线圈从目标器官，他们只提供匀场能力， 二阶球谐函数（SH），并且不能匀场高阶局部场变化 例如存在于心肺界面附近的那些。这仍然是一个尚未解决的挑战。 在这个项目中，我们将应用一种新的统一匀场射频线圈技术，以克服主要的限制， 3.0T CMR。我们将开发一个统一的匀场射频线圈，并验证其安全性和高阶匀场能力 (Aim 1）。我们将开发一种基于我们的低秩呼吸运动分辨B0场标测技术， 多任务框架和实时匀场电路，以实现自由呼吸CMR的动态匀场（目标2）。 然后，我们将在3.0T（目标3）上在人类受试者中验证该技术。成功完成该项目 将在3.0T上实现强大的SSFP CMR，这是一个重大的技术挑战，它允许可靠的高分辨率， SNR CMR，包括但不限于电影和冠状动脉MRA。这种新型心脏匀场系统具有 可能对加速3.0T CMR的临床采用产生重大影响。

Abstract Cardiovascular disease is the leading cause of death globally. Cardiovascular magnetic resonance (CMR) is routinely used in the clinical management of cardiovascular disease and is the standard method for the assessment of cardiac function and myocardial tissue properties. Today, most clinical CMR studies are still conducted on 1.5T scanners because of their availability and robustness in executing CMR protocols. In general, 3.0T provides higher SNR, spatial resolution, and reduced scan time than 1.5T. However, the increased B0 field strength also poses technical challenges for CMR. A major challenge is the susceptibility or off-resonance artifacts due to worsened B0 field inhomogeneity. In the last two decades, steady-state free precession (SSFP) has revolutionized CMR on 1.5T because it boosts SNR and contrast to noise ratio (CNR) markedly over gradient-echo based acquisitions. However, its routine use on 3.0T has been inconsistent despite continuously improving B0 homogeneity and shimming capabilities. Therefore, gradient-echo based acquisitions are still routinely used, such as for cine imaging, cardiac relaxometry, and coronary MRA, negating the major advantages of 3.0T for CMR. Due to the distance of standard whole-body shimming coils from the target organ, they only provide shimming capabilities up to the second-order spherical harmonic (SH), and are incapable of shimming higher-order localized field variations such as those present near the heart-lung interface. This remains an unmet challenge. In this project, we will apply a novel unified shim-RF coil technique to overcome the primary limitation in 3.0T CMR. We will develop a unified shim-RF coil and validate its safety and high-order shimming capability (Aim 1). We will develop a respiratory motion-resolved B0 field mapping technique based on our low-rank Multitasking framework and real-time shim circuits to allow dynamic shimming for free breathing CMR (Aim 2). We will then validate the technology in human subjects on 3.0T (Aim 3). Successful completion of this project will enable robust SSFP CMR on 3.0T, a major technical challenge, which allows reliable high-resolution, high- SNR CMR, including but not limited to cine and coronary MRA. This novel cardiac shimming system has the potential to have a major impact in accelerating the clinical adoption of 3.0T CMR.