A new photoacoustic imaging platform for potential applications in prostate cancer

Photoacoustic imaging combines high optical contrast due to wavelength selectivity of chromophores in the tissue with relatively deep imaging enabled by ultrasound. This study introduces a new imaging platform by combining high resolution clinical transrectal micro-Ultrasound with transurethral light delivery for photoacoustic imaging of the prostate. A clinical 512-element, 22.5 MHz transrectal ultrasound system was modified to acquire acoustic signal synchronous to optical excitation using a tunable laser. Offline beamforming and image reconstruction algorithms were developed to generate photoacoustic images. A single core multimode optical fiber was adapted for use as a side-firing transurethral light delivery. The combined micro-Ultrasound and photoacoustic imaging system was characterized in PVC-plastisol phantoms. The measured axial and lateral resolutions were 150±20 µm and 450±25 µm respectively. The imaging capability of the system was tested by imaging porphysome contrast agent. The system was capable of imaging ~10 µM concentration of contrast agent at an optical depth of 15 mm.