Low-field (0.55 T) high-performance cardiovascular magnetic resonance (CMR) is an attractive platform for CMR-guided intervention as device heating is reduced around 7.5-fold compared to 1.5 T. This work determines the feasibility of visualizing cardiac radiofrequency (RF) ablation lesions at low field CMR and explores a novel alternative method for targeted tissue destruction: acetic acid chemoablation. N = 10 swine underwent X-ray fluoroscopy-guided RF ablation (6–7 lesions) and acetic acid chemoablation (2–3 lesions) of the left ventricle. Animals were imaged at 0.55 T with native contrast 3D-navigator gated T1-weighted T1w) CMR for lesion visualization, gated single-shot imaging to determine potential for real-time visualization of lesion formation, and T1 mapping to measure change in T1 in response to ablation. Seven animals were euthanized on ablation day and hearts imaged ex vivo. The remaining animals were imaged again in vivo at 21 days post ablation to observe lesion evolution. Chemoablation lesions could be visualized and displayed much higher contrast than necrotic RF ablation lesions with T1w imaging. On the day of ablation, in vivo myocardial T1 dropped by 19 ± 7% in RF ablation lesion cores, and by 40 ± 7% in chemoablation lesion cores (p < 4e−5). In high resolution ex vivo imaging, with reduced partial volume effects, lesion core T1 dropped by 18 ± 3% and 42 ± 6% for RF and chemoablation, respectively. Mean, median, and peak lesion signal-to-noise ratio (SNR) were all at least 75% higher with chemoablation. Lesion core to myocardium contrast-to-noise (CNR) was 3.8 × higher for chemoablation. Correlation between in vivo and ex vivo CMR and histology indicated that the periphery of RF ablation lesions do not exhibit changes in T1 while the entire extent of chemoablation exhibits T1 changes. Correlation of T1w enhancing lesion volumes indicated in vivo estimates of lesion volume are accurate for chemoablation but underestimate extent of necrosis for RF ablation. The visualization of coagulation necrosis from cardiac ablation is feasible using low-field high-performance CMR. Chemoablation produced a more pronounced change in lesion T1 than RF ablation, increasing SNR and CNR and thereby making it easier to visualize in both 3D navigator-gated and real-time CMR and more suitable for low-field imaging.

中文翻译：

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0.55 T 心肌射频消融和醋酸化学消融病变的原生对比可视化和组织表征

低场 (0.55 T) 高性能心血管磁共振 (CMR) 是 CMR 引导干预的一个有吸引力的平台，因为与 1.5 T 相比，设备加热减少了约 7.5 倍。这项工作确定了可视化心脏射频 (RF) 的可行性) 低场 CMR 下的消融病变，并探索了一种新的靶向组织破坏替代方法：醋酸化学消融。N = 10 猪接受了 X 射线透视引导的左心室射频消融（6-7 个病变）和醋酸化学消融（2-3 个病变）。动物在 0.55 T 下成像，自然对比度 3D 导航器门控 T1 加权 T1w) CMR 用于病变可视化，门控单次成像以确定实时可视化病变形成的潜力，以及 T1 映射以测量响应中 T1 的变化消融。七只动物在消融日被安乐死，心脏离体成像。其余动物在消融后 21 天再次在体内成像以观察病变演变。与 T1w 成像的坏死射频消融病变相比，化学消融病变可以可视化并显示出更高的对比度。在消融当天，体内心肌 T1 在射频消融病变核心中下降了 19 ± 7%，在化学消融病变核心中下降了 40 ± 7% (p < 4e-5)。在高分辨率离体成像中，随着局部体积效应的减少，RF 和化学消融的病变核心 T1 分别下降了 18 ± 3% 和 42 ± 6%。平均、中值和峰值病灶信噪比 (SNR) 均至少比化学消融高 75%。对于化学消融，病变核心与心肌的对比噪声比 (CNR) 高 3.8 倍。体内和离体 CMR 和组织学之间的相关性表明，射频消融病变的外围没有表现出 T1 的变化，而化学消融的整个范围表现出 T1 的变化。T1w 增强病灶体积的相关性表明病灶体积的体内估计对于化学消融是准确的，但低估了射频消融的坏死程度。使用低场高性能 CMR 可视化心脏消融导致的凝固坏死是可行的。与射频消融相比，化学消融在病变 T1 中产生了更明显的变化，增加了 SN​​R 和 CNR，从而更容易在 3D 导航门控和实时 CMR 中进行可视化，更适合低场成像。