Endovenous laser ablation (EVLA) is a minimally invasive surgical procedure, often guided by ultrasound (US) imaging, for treating venous insufficiencies. US imaging limitations in accurately visualizing the catheter and the lack of a temperature monitoring system can lead to sub-optimal outcomes. An integrated photoacoustic (PA)-guided EVLA system has been previously developed and reported to overcome the shortcomings of US-guided procedure. In this study, we further characterized the system and tested the in vivo utility. In addition, PA thermometry was further explored by compensating the variation of PA signal with temperature with respect to the temperature-dependent absorption of blood and water. In vivo imaging results indicated that the PA-guided EVLA system can provide high contrast and accurate images of the ablation catheter tip overlaid on US images of the background tissue. Additionally, absorption-compensated PA signal amplitudes over a relevant range of temperature were measured and demonstrated.

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Accurate fiber tip tracking is a critical clinical problem during endovenous laser ablation (EVLA) of small perforating veins. Currently, ultrasound (US) imaging is the gold-standard modality for visualizing and for accurately placing the ablation fiber within the diseased vein. However, US imaging has limitations such as angular dependency and comet tail artifacts. In addition, EVLA is often performed without any real-time temperature monitoring, which could lead to an insufficient thermal dose or overheating the surrounding tissue. We propose a new technique that combines US and photoacoustic (PA) imaging for concurrent ablation fiber tip tracking and real-time temperature monitoring during EVLA procedures. Our intended implementation of PA imaging for fiber tracking requires minimal modification of existing systems, which makes this technology easy to adopt. Combining US and PA imaging modalities allows for simultaneous visualization of background anatomical structures as well as high contrast, artifact-free, and angle-independent localization of the ablation fiber tip. Preliminary data demonstrates that changes in the amplitude of the PA signal can be used to monitor the localized temperature at the tip of the ablation fiber, which will be invaluable during EVLA procedures. These improvements can enhance the physician’s accuracy in performing EVLA procedures and will have a significant impact on the treatment outcomes.

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