In vivo imaging in the oral cavity by endoscopic optical coherence tomography

Abstract

The common way to diagnose hard and soft tissue irregularities in the oral cavity is initially the visual inspection by an experienced dentist followed by further medical examinations, such as radiological imaging and/or histopathological investigation. For the diagnosis of oral hard and soft tissues, the detection of early transformations is mostly hampered by poor visual access, low specificity of the diagnosis techniques, and/or limited feasibility of frequent screenings. Therefore, optical noninvasive diagnosis of oral tissue is promising to improve the accuracy of oral screening. Considering this demand, a rigid handheld endoscopic scanner was developed for optical coherence tomography (OCT). The novelty is the usage of a commercially near-infrared endoscope with fitting optics in combination with an established spectral-domain OCT system of our workgroup. By reaching a high spatial resolution, in vivo images of anterior and especially posterior dental and mucosal tissues were obtained from the oral cavity of two volunteers. The convincing image quality of the endoscopic OCT device is particularly obvious for the imaging of different regions of the human soft palate with highly scattering fibrous layer and capillary network within the lamina propria.

In Vivo Endoscopic Optical Coherence Tomography of the Healthy Human Oral Mucosa: Qualitative and Quantitative Image Analysis

“…Comparing the measurement points of the buccal side, epithelium was thickest at the central part. The basement membrane was intact in 60.8%, however, an amount of 22.4% was stated as not assessable due to the increased epithelial thickness and the limited imaging depth in biological tissue [ 36 ]. With regard to future studies, automated segmentation of the epithelium of the buccal mucosa could be challenging due to hyperkeratinization and a reduced visibility of the basement membrane.…”

“…Acquisition of OCT image series was realized by the use of a customized optical probe (lateral resolution: 17.4 , working distance: 7.5 mm) based on a commercial rigid endoscope (8711 AGA, Karl Storz GmbH & Co. KG, length: 200 mm, insertion diameter: 10 mm, angle of view: 0 ) [ 36 ] in combination with a self-built spectrometer-based OCT system using a fiber-coupled superluminescent diode (SLD-371-HP1, Superlumdiodes Ltd., center wavelength: = 840 nm, FWHM: = 45 nm) and a customized spectrometer [ 37 ], providing an axial resolution in air of 11.6 . Cross-sectional OCT images (64 B-scans) consisting of 480 A-scans were detected with increments of x = 5 (fast scanning axis) and y = 10 (slow scanning axis) to cover a scanning field of 2.4 mm × 0.6 mm in about 2.5 s (f A-scan = 11.88 kHz).…”

Low-cost, ultracompact handheld optical coherence tomography probe for in vivo oral maxillofacial tissue imaging

“…For example, the hidden crack on a tooth is hardly distinguishable from demineralization based on visual inspection since both appear as whitish spots on the tooth surface. 20 However, these two defects look totally different in OCT images. While demineralization is manifested as strong scattering throughout the affected enamel, 20 the hard-objectinduced inner crack exhibits normal enamel signal with high scattering signal localized to near the crack boundary [ Fig.…”

“…7(c)]. Vertically extended low scattering regions within the enamel layer above the crevice were shadows caused by high scattering microcracks 20 [white asterisks in Fig. 7(b)].…”

An Intraoral OCT Probe to Enhanced Detection of Approximal Carious Lesions and Assessment of Restorations

“…The lateral resolution was d x = 50 µm and the axial resolution d z = 20 µm [ 32 ]. Some in vivo applications of OCT followed with special hand-held probes to also image carious or non-carious lesions [ 33 , 34 , 35 , 36 , 37 ] or soft tissue [ 38 ] and to evaluate composite restorations using a standard device in long-term clinical studies [ 20 , 24 , 25 ]. In particular, the combination of clinical evaluation of composite restorations and the OCT assessment of the tooth-composite bond failure showed that OCT could provide important additional diagnostic information.…”