Photoacoustic Imaging Assisted Radiofrequency Ablation: Illumination Strategies and Prospects

Surgical resection is considered the gold standard for tumor treatment with curative intent. However, in most cases, patients are not eligible for resection, especially in functional tissue like liver. Minimally invasive thermal treatment like Radiofrequency Ablation (RFA) is gaining more applicability in this scenario. The success of RFA treatment depends on accurate needle placement and complete tumor ablation. Widely used Ultrasound (US) imaging lacks in providing accurate feedback of RFA device location and ablated tissue boundary. Here we propose Photoacoustic (PA) imaging in combination with US imaging for RFA device guidance and in differentiating ablated tissue. We employ two illumination strategies for PA imaging: an extracorporeal light delivery, and an interstitial light delivery. First, using the extracorporeal illumination we demonstrate how PA imaging can improve RFA device visibility and in differentiating ablated tissue in an ex vivo laboratory setting. Further, we expose the difficulty in imaging highly absorbing tissue using illumination from the surface of the skin. This limitation leads to the development of an interstitial illumination probe. We compare these two illumination strategies and present our preliminary results in RFA device guidance using the interstitial probe. Our results show the potential of PA imaging in improving the accuracy of the RFA procedure.