Degree

Doctor of Philosophy (PhD)

Department

Department of Electrical and Computer Engineering

Document Type

Dissertation

Abstract

Nowadays, X-ray imaging is serving as the mainstream imaging method for diagnosing dental diseases, but the major issue of this method is the ionizing radiation due to the high energy of X-ray photons. This project aims to develop near-infrared fluorescence (NIRF) dental imaging by using Indocyanine Green (ICG) as a fluorescence agent, demonstrate its feasibility in the rat model (an endoscope employed) and human extracted teeth. In the rat model, the dental structures were recognized from ICG-NIRF dental images in the first (700-1,000 nm, ICG-NIRF-I) and second (1,000-1,700 nm, ICG-NIRF-II) NIR windows. Oral administration (mouthwash in erupted molars) could serve as an alternative approach for the non-invasive ICG delivery. Better imaging quality for both erupted and unerupted molars were found at a short imaging time (within 4 h). The remarkable glow-in-the-dark effect was found in unerupted molars at a longer imaging time (24-96 h): only the molars remained bright, and the background tissues were relatively dark. We also found that using the laser to ablate dental follicles could greatly disrupt the molar eruption; ICG-NIRF dental imaging could recognize the abnormal eruption of laser-treated molars. In human extracted teeth, ICG-NIRF imaging had better efficiency in the two NIR windows than the conventional NIRi-II (NIR illumination-II). Most enamel cracks, the location where the crack on the teeth originated, could not be detected by X-ray imaging but were clearly observed using ICG-NIRF images. From the crack's shadow, crack depth was accurately evaluated using ICG-NIRF images. The severe cracks and enamel-only cracks could be identified from the bright difference at the two sides of the crack phase: large dark regions on one side (shadow side) but bright on the other side were more likely to be enamel-dentin cracks. In contrast, enamel-only cracks had a narrow shadow. For crack depth, ICG-NIRF-II imaging with transillumination exposure could obtain the most accurate crack depth when compared to other ICG-based imaging. Overall, ICG-NIRF dental imaging could be a useful imaging technique in dental research. This method potentially can serve as a novel ionizing-radiation-free imaging approach for diagnosing dental diseases.

Committee Chair

Xu, Jian

Available for download on Wednesday, November 01, 2028

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