Non-contrast MRI of RF Ablation Lesions in the Treatment of Cardiac Arrhythmia

在美国，心律失常影响着数百万人。很多都是处方 药物治疗，但更严重的情况是射频消融心肌(心肌)组织，由 导尿术。消融目标通常使用电解剖(EA)映射来选择， 将传感导管放置在心腔内的多个位置以分析 并确定可能出现折返回路的位置。使用此信息，一个 然后，使用x射线透视和电针图将消融导管导航到这些靶点。 然而，由于心肌在x光中几乎是看不见的，靶向错误是频繁的。它是 也不可能确切地说出哪些区域已经消融(病变)，以及消融到什么地方 范围，或者是否仍然存在任何差距。因此，消融治疗后心律失常的复发 相当常见，需要反复治疗。这些缺点可以用磁力解决。 磁共振成像(MRI)。在核磁共振成像中，心肌很容易被看到，很容易与 血液和足够的细节可以识别解剖标志，al，可以 提高目标精确度。 用于显示消融病变的典型MR成像方法使用T1C缩短 基于Gd的造影剂(GBCA)，用于识别受损或死亡的组织。在健康的心肌中， 造影剂会在几分钟内洗入，然后洗出。在坏死性心肌中，洗出的 过程受到影响，因此造影剂仍留在组织中，并在T1C加权时增强 MR图像，称为晚期Gd增强(LGE)。然而，需要一种造影剂 在目前的方法中是一个缺点，原因有很多。图像中有复杂的东西 解释和剂量限制，限制了监测治疗的效用。用于可视化 我们开发了一种有效的磁共振成像技术，它可以 不需要使用造影剂。我们希望开发、优化和测试这种方法 此图显示病变的坏死(死亡)区域有强化，水肿被视为一种 强化周围的暗带。我们的初步结果显示可靠和容易看到的病变在 厚壁和薄壁的心肌壁。这可能会在(筛选、规划)之前带来巨大的好处， 在消融过程中(瞄准、评估)或之后(评估)。 在获得初步结果的过程中，我们选择了容易产生的成像参数 消融病变与正常心肌、空洞血对比明显。我们希望改进 并验证技术，优化成像参数和方案，研究结果，以及 研究如何将其用于临床应用。 用所提出的技术获得的病变图像可用于指导消融过程 无论是在X光/超声(典型)或核磁共振(正在研究)的指导下进行。在……里面 无论哪种情况，这项技术都可以通过回答以下问题来评估治疗： 心肌的所有靶区是否都被消融到坏死点，这是已知的 导致永久性传导阻滞？这样的图像将有助于确定该程序是否 已经完成，或者需要进一步消融才能完成覆盖。未来的研究可以跟进 以评估患者对复发的影响。

Cardiac arrhythmias affect millions of people in the United States. Many are prescribed medication, but more severe cases are treated with RF ablation of myocardial (heart muscle) tissue, administered by catheterization. Ablation targets are typically chosen using electro-anatomical (EA) mapping, where a sensing catheter is placed at many locations in the heart chamber to analyze the electrograms and determine where reentrant circuits may be occurring. Using this information, an ablation catheter is then navigated to those targets, using x-ray fluoroscopy and the EA map. However, since myocardium is all but invisible in x-ray, targeting inaccuracies are frequent. It is also impossible to tell with any certainty which areas have been ablated (the lesions), and to what extent, or if any gaps still exist. As a result, recurrence of arrhythmias after ablation therapy is quite common, requiring repeated treatment. These shortcomings can be addressed with magnetic resonance imaging (MRI). With MRI, myocardium is readily visible, easily distinguishable from blood, and sufficient detail is available to recognize anatomical landmarks, al, of which can improve targeting accuracy. Typical MR imaging methods for visualizing ablation lesions employ a T1Cshortening gadolinium-based contrast agent (GBCA) to identify damaged or dead tissue. In healthy myocardium, contrast agent washes in then washes out over a few minutes. In necrotic myocardium, the wash out process is compromised, so the contrast agent remains in the tissue and is enhanced in T1Cweighted MR images, referred to as late gadolinium enhancement (LGE). However, the need for a contrast agent in current methods is a disadvantage for multiple reasons. There are complexities in image interpretation and dosage limitations, limiting utility in monitoring treatment. For visualizing ablation lesions acutely, we have developed an efficient MR imaging technique which does not require the use of contrast agent. This method, which we hope to develop, optimize and test in this proposal, shows enhancement in the necrotic (dead) region of the lesion, with edema seen as a dark band around the enhancement. Our preliminary results show reliable and readily seen lesions in both thick and thin myocardial walls. This could be of great benefit before (screening, planning), during (targeting, assessing) or after (evaluating) an ablation procedure. In obtaining our preliminary results, we have chosen imaging parameters which produce readily visible contrast between ablation lesions, normal myocardium and cavitary blood. We wish to improve and validate the technique, optimizing imaging parameters and protocols, study the results, and investigate how this may be used in clinical application. Lesion images obtained with the proposed technique may be used to guide an ablation procedure whether performed under guidance of x-ray/ultrasound (typical) or MRI (under investigation). In either case, this technique can be used to evaluate the treatment, by answering the question: Have all target regions of myocardium been ablated to the point of necrosis, which is known to cause lasting conduction block? Images such as these will help to determine whether the procedure is finished, or if further ablations are required to complete coverage. Future study can follow patients to evaluate the impact on recurrence.