title: Photoacoustic Characterization of Radiofrequency Ablation Lesions.
abstract: Radiofrequency ablation (RFA) procedures are used to destroy abnormal electrical pathways in the heart that can cause cardiac arrhythmias. Current methods relying on fluoroscopy, echocardiography and electrical conduction mapping are unable to accurately assess ablation lesion size. In an effort to better visualize RFA lesions, photoacoustic (PA) and ultrasonic (US) imaging were utilized to obtain co-registered images of ablated porcine cardiac tissue. The left ventricular free wall of fresh (i.e., never frozen) porcine hearts was harvested within 24 hours of the animals' sacrifice. A THERMOCOOL®Ablation System (Biosense Webster, Inc.) operating at 40 W for 30-60 s was used to induce lesions through the endocardial and epicardial walls of the cardiac samples. Following lesion creation, the ablated tissue samples were placed in 25 °C saline to allow for multi-wavelength PA imaging. Samples were imaged with a Vevo®2100 ultrasound system (VisualSonics, Inc.) using a modified 20-MHz array that could provide laser irradiation to the sample from a pulsed tunable laser (Newport Corp.) to allow for co-registered photoacoustic-ultrasound (PAUS) imaging. PA imaging was conducted from 750-1064 nm, with a surface fluence of approximately 15 mJ/cm2maintained during imaging. In this preliminary study with PA imaging, the ablated region could be well visualized on the surface of the sample, with contrasts of 6-10 dB achieved at 750 nm. Although imaging penetration depth is a concern, PA imaging shows promise in being able to reliably visualize RF ablation lesions.
authors.affiliation: Department of Imaging Physics, MD Anderson Cancer Center, Houston, TX, USA ; Department of Biomedical Engineering, University of Texas at Austin, Austin, TX, USA.
authors.forename: Richard
authors.initials: R
authors.lastname: Bouchard
authors.affiliation: Department of Biomedical Engineering, University of Texas at Austin, Austin, TX, USA.
authors.forename: Nicholas
authors.initials: N
authors.lastname: Dana
authors.affiliation: Department of Biomedical Engineering, University of Texas at Austin, Austin, TX, USA ; Texas Cardiac Arrhythmia Institute, St. David's Medical Center, Austin, TX, USA ; Department of Cardiology, University of Foggia, Foggia, Italy.
authors.forename: Luigi
authors.initials: L
authors.lastname: Di Biase
authors.affiliation: Department of Biomedical Engineering, University of Texas at Austin, Austin, TX, USA ; Texas Cardiac Arrhythmia Institute, St. David's Medical Center, Austin, TX, USA.
authors.forename: Andrea
authors.initials: A
authors.lastname: Natale
authors.affiliation: Department of Imaging Physics, MD Anderson Cancer Center, Houston, TX, USA ; Department of Biomedical Engineering, University of Texas at Austin, Austin, TX, USA.
authors.forename: Stanislav
authors.initials: S
authors.lastname: Emelianov
keywords: cardiac arrhythmias; lesion imaging; photoacoustic imaging; radiofrequency catheter ablation