Photoacoustic (PA) imaging with internal light illumination through optical fiber could enable imaging of internal organs at deep penetration. We have developed a transurethral probe with a multimode fiber inserted in a rigid cystoscope sheath for illuminating the prostate. At the distal end, the fiber tip is processed to diffuse light circumferentially over 2 cm length. A parabolic cylinder mirror then reflects the light to form a rectangular-shaped parallel beam which has at least 1 cm2 at the probe surface. The relatively large rectangular beam size can reduce the laser fluence rate on the urethral wall and thus reduce the potential of tissue damage. A 3 cm optical penetration in chicken tissue is achieved at a fluence rate around 7 mJ/cm2 . For further validation, a prostate phantom was built with similar optical properties of the human prostate. A 1.5 cm penetration depth is achieved in the prostate mimicking phantom at 10 mJ/cm2 fluence rate. PA imaging of prostate can potentially be carried out in the future by combining a transrectal ultrasound transducer and the transurethral illumination.
Min Ai, Tim Salcudean, Robert Rohling, Purang Abolmaesumi, and Shuo Tang, "Transurethral illumination probe design for deep photoacoustic imaging of prostate," Proc. SPIE 10494, Photons Plus Ultrasound: Imaging and Sensing 2018, 104940C (Presented at SPIE BiOS: January 28, 2018; Published: 19 February 2018); https://doi.org/10.1117/12.2291164.
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