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

心律失常影响美国数百万人。 许多人被规定 药物治疗，但更严重的情况是用心肌（心肌）组织的射频消融治疗， 漂浮导管消融目标通常使用电解剖（EA）标测来选择， 其中感测导管被放置在心脏腔室中的许多位置处 心电图，并确定折返性电路可能发生的地方。利用这些信息， 然后使用X射线荧光透视和EA标测图将消融导管导航到这些目标。 然而，由于心肌在X射线中几乎是不可见的，因此靶向不准确是常见的。是 也不可能确切地说出哪些区域（病变）已经消融，以及消融到什么部位。 #21453;，或者是否存在差距。因此，消融治疗后心律失常的复发 很常见，需要反复治疗。这些缺点可以通过磁 磁共振成像（MRI）。使用MRI，心肌很容易可见，很容易区分， 血液，并且足够的细节可用于识别解剖标志，其中， 提高瞄准精度。 用于可视化消融病变的典型MR成像方法采用T1 C缩短 钆基造影剂（GBCA），以识别受损或死亡组织。在健康心肌中， 造影剂洗入，然后在几分钟内洗出。在坏死心肌中， 过程受损，因此造影剂保留在组织中，并在T1 C加权中增强 MR图像，称为晚期钆增强（LGE）。然而，对造影剂的需求 在当前的方法中，由于多种原因是不利的。在图像中有复杂性 解释和剂量限制，限制了监测治疗的实用性。用于可视化 急性消融病变，我们已经开发出一种有效的MR成像技术， 不需要使用造影剂。这种方法，我们希望开发，优化和测试， 这一建议，显示增强坏死（死亡）区域的病变，水肿被视为一个 增强图像周围有暗带。我们的初步结果表明，可靠的和容易看到的病变， 厚的和薄的心肌壁。这可能是巨大的好处之前（筛选，规划）， 在消融手术期间（瞄准、评估）或之后（评估）。 在获得我们的初步结果，我们选择了成像参数， 消融病灶、正常心肌和腔血之间的对比明显。我们希望改进 并验证该技术，优化成像参数和方案，研究结果， 研究如何将其用于临床应用。 利用所提出的技术获得的病变图像可用于指导消融手术 无论是在X线/超声（典型）还是MRI（研究中）引导下进行。在 无论哪种情况，该技术都可以通过回答以下问题来评估治疗： 所有心肌靶区是否已消融至坏死点， 导致持续传导阻滞？像这样的图像将有助于确定程序是否 完成，或者是否需要进一步消融以完成覆盖。 未来的研究可以遵循 患者评估对复发的影响。

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.