Fine-resolution photoacoustic imaging of the eye

Ronald H. Silverman; Fanting Kong; Harriet O. Lloyd; Y. C. Chen

doi:10.1117/12.842471

25 February 2010 Fine-resolution photoacoustic imaging of the eye

Ronald H. Silverman, Fanting Kong, Harriet O. Lloyd, Y. C. Chen

Proceedings Volume 7564, Photons Plus Ultrasound: Imaging and Sensing 2010; 75640Y (2010) https://doi.org/10.1117/12.842471
Event: SPIE BiOS, 2010, San Francisco, California, United States

Abstract

Purpose: Ultrasound and optical coherence tomography (OCT) are widely used techniques for diagnostic imaging of the eye. OCT provides excellent resolution, but limited penetration. Ultrasound provides better penetration, but an order-of-magnitude poorer resolution than OCT. Photoacoustic imaging is relatively insensitive to scattering, and so offers a potential means to image deeper than OCT. Furthermore, photoacoustic imaging detects optical absorption, a parameter that is independent of that detected by conventional ultrasound or OCT. Our aim was to develop a photoacoustic system suitable for imaging the eye. Methods: We developed a prototype system utilizing a focused 20 MHz ultrasound probe with a central aperture through which optics were introduced. The prototype system produced 1-μJ, 5-nsec pulses at 532 or 1064 nm with a 20-μm spot size at a 500 Hz repetition rate. The photoacoustic probe was mounted onto computer-controlled linear stages and pulse-echo ultrasound and photoacoustic images obtained on ex vivo pig eyes and in vivo mouse eyes. Results: Lateral resolution was significantly improved by use of a laser spot size much smaller than the acoustic beamwidth. Photoacoustic signals were obtained primarily from melanin in ex vivo tissues and from melanin and hemoglobin in vivo. Image fusion allowed superposition of photoacoustic signals upon the anatomic features detected by conventional ultrasound. Conclusion: Photoacoustic imaging detects the presence of clinically relevant pigments, such as melanin and oxyand deoxy-hemoglobin, and, potentially, from other pathologic pigments occurring in disease conditions (tumors, nevii, macular degeneration). Fine-resolution photoacoustic data provides information not detected in current ophthalmic imaging modalities.

Citation Download Citation

Ronald H. Silverman, Fanting Kong, Harriet O. Lloyd, and Y. C. Chen "Fine-resolution photoacoustic imaging of the eye", Proc. SPIE 7564, Photons Plus Ultrasound: Imaging and Sensing 2010, 75640Y (25 February 2010); https://doi.org/10.1117/12.842471

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