In vitro photoacoustic visualization of myocardial ablation lesions.
BACKGROUND
Radiofrequency (RF) ablation to treat atrial arrhythmia is limited by the inability to reliably assess lesion durability and transmurality.


OBJECTIVE
The purpose of this study was to determine the feasibility of photoacoustic characterization of myocardial ablation lesions in vitro. In this study, we investigated the feasibility of combined ultrasound (US) and spectroscopic photoacoustic imaging to visualize RF ablation lesions in three dimensions (3D) based on unique differences in the optical absorption spectra between normal and ablated myocardial tissue.


METHODS
Tissue samples were excised from the ventricles of fresh porcine hearts. Lesions were generated using an RF catheter ablation system using 20 to 30 W of power applied for 40 to 60 seconds. Ablated samples were imaged in the near-infrared regime (740-780 nm) using a combined PA/US imaging system. Measured PA spectra were correlated to the absorption spectra of deoxyhemoglobin and ablated tissue to produce a tissue characterization map (TCM) identifying 3D lesion location and extent. Tissue samples were stained and photographed for gross pathology. TCM and gross pathology images were coregistered to assess TCM accuracy.


RESULTS
TCM reliably characterized ablated and non-ablated tissue up to depths of 3 mm. TCM also assessed lesion position and extent with submillimeter accuracy in multiple dimensions. Segmented TCMs achieved >69% agreement with gross pathology.


CONCLUSIONS
The study results suggest that spectroscopic photoacoustic imaging has the potential to accurately assess RF ablation lesion size and position with submillimeter precision and may be well suited to guide transcatheter RF atrial ablation in clinical practice.
Department of Biomedical Engineering, University of Texas at Austin, Austin, Texas; Department of Imaging Physics, University of Texas MD Anderson Cancer Center, Houston, Texas.
Nicholas
N
Dana
Department of Biomedical Engineering, University of Texas at Austin, Austin, Texas; Texas Cardiac Arrhythmia Institute, St. David's Medical Center, Austin, Texas; Department of Cardiology, University of Foggia, Foggia, Italy; Albert Einstein College of Medicine, Montefiore Hospital, New York, New York.
Luigi
L
Di Biase
Department of Biomedical Engineering, University of Texas at Austin, Austin, Texas; Texas Cardiac Arrhythmia Institute, St. David's Medical Center, Austin, Texas.
Andrea
A
Natale
Department of Biomedical Engineering, University of Texas at Austin, Austin, Texas; Department of Imaging Physics, University of Texas MD Anderson Cancer Center, Houston, Texas.
Stanislav
S
Emelianov
Department of Biomedical Engineering, University of Texas at Austin, Austin, Texas; Department of Imaging Physics, University of Texas MD Anderson Cancer Center, Houston, Texas. Electronic address: RRBouchard@mdanderson.org.
Richard
R
Bouchard
D000818:Animals; D001281:Atrial Fibrillation / Q000473:pathology* / Q000601:surgery; D017115:Catheter Ablation / Q000379:methods*; D004195:Disease Models, Animal; D005260:Female; D006325:Heart Atria / Q000473:pathology / Q000601:surgery*; D009206:Myocardium / Q000473:pathology*; D061088:Photoacoustic Techniques / Q000379:methods*; D015203:Reproducibility of Results; D013552:Swine; D041623:Tomography, Optical Coherence / Q000379:methods*
3D; AF; ARFI; Ablation; Atrial fibrillation; CBR; FOV; Hb; Imaging; MRI; NTB; OCT; PA; PBS; Photoacoustic; RF; ROI; RT; Radiofrequency; TCM; Tissue characterization; US; acoustic radiation force impulse; atrial fibrillation; contrast-to-background ratio; deoxyhemoglobin; field of view; magnetic resonance imaging; nitrotetrazolium blue; optical coherence tomography; phosphate-buffered saline; photoacoustic; radiofrequency; real time; region of interest; sPA; spectroscopic photoacoustic; tPA; thermographic photoacoustic; three-dimensional; tissue characterization map; ultrasound