Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, United States of America.
PLoS One. 2013 Dec 12;8(12):e82689. doi: 10.1371/journal.pone.0082689. eCollection 2013.
Intra-procedural imaging is important for guiding cardiac arrhythmia ablation. It is difficult to obtain intra-procedural correlation of thermal lesion formation with action potential (AP) changes in the transmural plane during ablation. This study tested parametric ultrasound imaging for transmural imaging of lesion and AP changes in high intensity focused ultrasound (HIFU) ablation using coronary perfused canine ventricular wedge preparations (n = 13). The preparations were paced from epi/endocardial surfaces and subjected to HIFU application (3.5 MHz, 11 Hz pulse-repetition-frequency, 70% duty cycle, duration 4 s, 3500 W/cm(2)), during which simultaneous optical mapping (1 kframes/s) using di-4-ANEPPS and ultrasound imaging (30 MHz) of the same transmural surface of the wedge were performed. Spatiotemporally correlated AP measurements and ultrasound imaging allowed quantification of the reduction of AP amplitude (APA), shortening of AP duration at 50% repolarization, AP triangulation, decrease of optical AP rise, and change of conduction velocity along tissue depth direction within and surrounding HIFU lesions. The threshold of irreversible change in APA correlating to lesions was determined to be 43 ± 1% with a receiver operating characteristic (ROC) area under curve (AUC) of 0.96 ± 0.01 (n = 13). Ultrasound imaging parameters such as integrated backscatter, Rayleigh (α) and log-normal (σ) parameters, cumulative extrema of σ were tested, with the cumulative extrema of σ performing the best in detecting lesion (ROC AUC 0.89 ± 0.01, n = 13) and change of APA (ROC AUC 0.79 ± 0.03, n = 13). In conclusion, characteristic tissue and AP changes in HIFU ablation were identified and spatiotemporally correlated using optical mapping and ultrasound imaging. Parametric ultrasound imaging using cumulative extrema of σ can detect HIFU lesion and APA reduction.
术中成像对于指导心脏心律失常消融至关重要。在消融过程中，很难获得热损伤形成与透壁平面动作电位 (AP) 变化的术中相关性。本研究使用冠状动脉灌注犬心室楔形标本（n = 13）测试了超声参数成像在高强度聚焦超声 (HIFU) 消融中的透壁成像和 AP 变化。标本从心外膜/心内膜表面起搏，并进行 HIFU 应用（3.5 MHz，11 Hz 脉冲重复频率，70%占空比，持续时间 4 s，3500 W/cm(2)），在此期间，同时进行光学映射（1 kframes/s）使用 di-4-ANEPPS 和楔形相同透壁表面的超声成像（30 MHz）。时空相关的 AP 测量和超声成像允许定量测量 AP 幅度（APA）的减少、AP 复极化 50%时的持续时间缩短、AP 三角化、光学 AP 上升减少以及组织深度方向上的传导速度变化在 HIFU 损伤内和周围。确定与病变相关的 APA 不可逆变化的阈值为 43 ± 1%，ROC 曲线下面积 (AUC) 为 0.96 ± 0.01（n = 13）。测试了回波强度、瑞利 (α) 和对数正态 (σ) 参数等超声成像参数，以及σ的累积极值，其中σ的累积极值在检测病变（ROC AUC 0.89 ± 0.01，n = 13）和 APA 变化（ROC AUC 0.79 ± 0.03，n = 13）方面表现最佳。总之，使用光学映射和超声成像，识别并时空相关地分析了 HIFU 消融中的特征性组织和 AP 变化。使用σ的累积极值的参数超声成像可以检测 HIFU 病变和 APA 减少。
