Purpose: The term “image-guided therapy” has traditionally been confined to predominantly macroscopic imaging modalities (e.g., CT, MR, and US), which offer resolution on the order of mm, for guiding therapeutic interventions. Here, we introduce the concept of microscopic image guidance for real-time thermal therapy monitoring in epithelial lesions using optical frequency domain imaging (OFDI), which offers high-speed, high-resolution (10 mm) imaging in 3D. Our earlier clinical studies using our OFDI balloon catheters have shown promise in Barrett’s esophagus (BE) screening. This study aims to develop a versatile, OFDI-based thermal therapy monitoring platform to precisely target epithelial lesions, such as BE with dysplasia.
Materials: We developed a microscopic thermal therapy guidance platform that integrates a flexible bipolar radiofrequency ablation (RFA) electrode array around the clinical balloon OFDI catheter. Imaging was performed between consecutive electrodes in porcine esophagus ex vivo. We developed a therapy monitoring technique based on complex differential variance (CDV) that enables the direct, noninvasive visualization of the coagulation zone at high spatial resolution using real-time, dynamic fluctuations in the OFDI signals. This is contrary to conventional, temperaturebased RFA monitoring techniques, which are often invasive and only provide an indirect measure of tissue injury, or emerging techniques (e.g., MR and US thermometry) limited by spatial resolution.
Results: We demonstrated real-time, direct, label-free visualization of the coagulation process during RFA ablation at high-resolution using our integrated RFA therapy delivery and OFDI balloon catheter-based guidance system. Our histological analysis using nitroblue tetrazolium chloride (NBTC) frozen sections confirmed that the CDV-based technique accurately and directly delineates the thermal coagulation zone in porcine esophagus ex vivo.
Conclusions: The ability to delineate thermal lesions at high resolution opens up the possibility of performing microscopic image-guided procedures in numerous clinical applications, especially in epithelial lesions where the precise delivery of thermal energy is critical.