Efficacy of High Temporal Frequency Photoacoustic Guidance of Laser Ablation Procedures

Abstract

Inaccurate placement of the ablation catheter and the inability to monitor the real-time temperature within the tissue of interest such as veins curbs the treatment efficacy of laser ablation procedures during thermal therapies. Our previous studies have validated the efficacy of photoacoustic (PA) imaging during endovenous laser ablation (EVLA) procedures. However, the PA-guided therapies suffer from low temporal resolution, due to the low pulse repetition rates of pulsed lasers, which could cause a problem during fast catheter motion and rapid temperature changes. Herein, to enhance the accuracy and sensitivity for tracking the ablation catheter tip and temperature monitoring, we proposed to develop a high frame rate (500 Hz), combined ultrasound (US), and PA-guided ablation system. The proposed PA-guided ablation system was evaluated in a set of ex vivo tissue studies. The developed system provides a 2 ms temporal resolution for tracking and monitoring the ablation catheter tip’s location and temperature, which is 50 times higher temporal resolution compared to the previously proposed 10 Hz system. The proposed system also provided more accurate feedback about the temperature variations during rapid temperature increments of 10°C per 250 ms. The co-registered US and PA images have an imaging resolution of about 200 μm and a field of view of 45 × 40 mm2. Tracking the ablation catheter tip in an excised tissue layer shows higher accuracy during a relatively fast catheter motion (0.5–3 mm/s). The fast US/PA-guided ablation system will potentially enhance the outcome of ablation procedures by providing location and temperature feedback.

Ultrasound and Photoacoustic Imaging for the Guidance of Laser Ablation Procedures

“…Inaccuracies induced by low PA imaging frame rates can generate a non-uniform ablation pattern and cause the recurrence of the malady being treated. The low energy of pulsed lasers for integrated PA imaging and ablation catheters provides an opportunity to use higher repetition rate lasers such as diode-pumped solid-state (DPSS) lasers at higher pulse repetition rates [ 74 ]. The high repetition rate of PA imaging detected more intermediate positions of the ablation catheter tip, improving the system’s temporal resolution and providing more precise tracking of the ablation catheter tip.…”

“…The high repetition rate of PA imaging detected more intermediate positions of the ablation catheter tip, improving the system’s temporal resolution and providing more precise tracking of the ablation catheter tip. We have previously demonstrated using a 500 Hz laser (NL 204-1K-SH, EKSPLA) to enhance PA thermometry accuracy during ablation [ 74 ]. The fast PA-guided laser ablation system provided more accurate feedback about the rapid temperature variations in increments of 100 °C per 250 ms.…”

Optimized Reconstruction Procedure of Photoacoustic Imaging for Reflection Artifacts Reduction

“…The spectrograms show the information of the signals along with both the frequency domain and time domain. The IBM was calculated according to the spectrogram of M-E DAS and equation (1). A binary matrix was created at the same size as the spectrogram.…”

“…Photoacoustic (PA) imaging [1][2][3] plays a promising role in medical diagnosis. Especially for functional imaging, it owns potential value in melanoma detection, [4][5][6] breast cancer detection, 7,8 vasculature imaging, [9][10][11] and molecular imaging.…”