A Low Cost Sensitive Transrectal Photoacoustic Probe With Single-Fiber Bright-Field Illumination for In Vivo Canine Prostate Imaging and Real-Time Biopsy Needle Guidance

In implementing prostate cancer screening using photoacoustic imaging (PAI), transrectal delivery of light and transrectal ultrasound (TRUS) transducer for signal detection is the most commonly used approach for PAI system design. In this approach, energy-efficient light delivery and good alignment of laser excitation and acoustic detection are very important for optimal imaging sensitivity. The previously published works adopted dark-field illumination for their probes. In this study, we proposed and achieved bright-field illumination, which enables more laser energy to be delivered to the region of interest for imaging, resulting in higher sensitivity of the probe. Further, by using a single optical fiber instead of fiber bundle, the efficiency of laser transmission was significantly enhanced. The adoption of single optical fiber also enhances the flexibility of the probe for operation and lower the cost. A custom designed photoacoustic imaging system was built in this study to verify the feasibility of the probe for clinical translational application. The spatial resolution and enhanced signal-to-noise ratio (SNR) of the proposed probe were validated using PAI of phantoms. We demonstrated the use of probe in diagnosing prostate cancer in vivo using a canine model mimicking prostate cancer. Our results showed that the proposed probe could achieve high sensitivity and a wide field-of-view (FOV) in imaging prostate cancer. We also performed minimally-invasive real-time guidance of needle biopsy in ex vivo prostate, showing the potential of the probe for early screening of prostate cancer and early preventive treatment of prostate tumor.