The Influence of Diode Laser Intensity Modulation on Photoacoustic Image Quality for Oral Soft Tissue Imaging

Rini Widyaningrum; Mitrayana Mitrayana; Rellyca Sola Gracea; Dewi Agustina; Munakhir Mudjosemedi; Harry Miyosi Silalahi

doi:10.34172/jlms.2020.S15

The Influence of Diode Laser Intensity Modulation on Photoacoustic Image Quality for Oral Soft Tissue Imaging

J Lasers Med Sci. 2020 Fall;11(Suppl 1):S92-S100. doi: 10.34172/jlms.2020.S15. Epub 2020 Dec 30.

Authors

Rini Widyaningrum¹, Mitrayana Mitrayana², Rellyca Sola Gracea¹, Dewi Agustina³, Munakhir Mudjosemedi¹, Harry Miyosi Silalahi⁴

Affiliations

¹ Department of Dentomaxillofacial Radiology, Faculty of Dentistry, Universitas Gadjah Mada, Jl. Denta, Sekip Utara, Yogyakarta, Indonesia.
² Department of Physics, Faculty of Mathematics and Natural Sciences, Universitas Gadjah Mada, Sekip Utara Unit III BLS 21, Yogyakarta, Indonesia.
³ Department of Oral Medicine, Faculty of Dentistry, Universitas Gadjah Mada, Jl. Denta, Sekip Utara, Yogyakarta, Indonesia.
⁴ Department of Applied Physics, University of Tunghai, Taiwan.

Abstract

Introduction: Imaging technologies have been developed to assist physicians and dentists in detecting various diseases. Photoacoustic imaging (PAI) is a new technique that shows great applicability to soft tissues. This study aimed to investigate the effect of diode laser intensity modulation on photoacoustic (PA) image quality. Methods: The prototype of the PAI system in this study utilized a non-ionizing 532 nm continuouswave (CW) diode laser illumination. Samples in this study were oral soft tissues of Sprague-Dawley rats fixed in 10% formalin solution. PA images were taken ex vivo by using the PAI system. The laser exposure for oral soft tissue imaging was set in various duty cycles (16%, 24%, 31%, 39%, and 47%). The samples were embedded in paraffin, and PA images were taken from the paraffinembedded tissue blocks in a similar method by using duty cycles of 40%, 45%, 50%, 55%, 60% respectively to reveal the influence of the laser duty cycle on PA image quality. Results: The oral soft tissue is clearly shown as a yellow to red area in PA images, whereas the nonbiological material appears as a blue background. The color of the PA image is determined by the PA intensity. Hence, the PA intensity of oral soft tissue was generally higher than that of the nonbiological material around it. The Kruskal-Wallis test followed by Mann-Whitney post-hoc analysis revealed significant differences (P<0.05) in the quality of PA images produced by using a 16%-47% duty cycle of laser intensity modulation for direct imaging of oral soft tissue fixed in 10% formalin solution. The PA image quality of paraffin-embedded tissue was higher than that of direct oral soft tissue images, but no significant differences in PA image quality were found between the groups. Conclusion: The PAI system built in this study can image oral soft tissue. The sample preparation and the diode laser intensity modulation may influence the PA image quality for oral soft tissue imaging. Nonetheless, the influence of diode laser intensity modulation is not significant for the PA image quality of paraffin-embedded tissue.

Keywords: Image quality; Laser; Modulation; Oral soft tissue; Photoacoustic.