Enhanced detection of dentinal lesions in OCT images using the RKT transformation

Abstract

Several studies have shown that optical coherence tomography (OCT) can be used to measure the remaining enamel thickness and detect the location of subsurface lesions hidden under the sound enamel. The purpose of this study was to develop algorithms to enhance the visibility of subsurface structures such as hidden occlusal lesions and the dentinal-enamel junction. Extracted teeth with natural occlusal lesions were imaged with OCT with and without added high index fluids. A Rotating Kernel Transformation (RKT) nonlinear image processing filter was applied to PS-OCT images to enhance the visibility of the subsurface lesions under the sound enamel. The filter significantly increased (P<0.05) the visibility of the subsurface lesions.

Clinical monitoring of smooth surface enamel lesions using CP‐OCT during nonsurgical intervention

“…The steps involved in converting the 3D CP‐OCT images into the mean values of the lesion depth ( L d ) and integrated reflectivity over the lesion depth (Δ R ) in the ROI are described in reference and shown graphically in the flowchart of that paper. For speckle noise reduction, signals not exceeding four standard deviations from the mean background noise floor were reduced to the mean background value and a Gaussian blur smoothing algorithm was applied using a 5 × 5 pixel convolution kernel . Finally, a modified rotating kernel transformation (RKT) emphasizing more on horizontal edges than on vertical edges was applied to each 2D b‐scan image to further increase signal‐to‐noise ratio thereby increasing the optical penetration .…”

“…For speckle noise reduction, signals not exceeding four standard deviations from the mean background noise floor were reduced to the mean background value and a Gaussian blur smoothing algorithm was applied using a 5 × 5 pixel convolution kernel . Finally, a modified rotating kernel transformation (RKT) emphasizing more on horizontal edges than on vertical edges was applied to each 2D b‐scan image to further increase signal‐to‐noise ratio thereby increasing the optical penetration . In the edge‐detection approach, the enamel edge, and the lower lesion boundary were determined by applying an edge locator .…”

“…Finally, a modified rotating kernel transformation (RKT) emphasizing more on horizontal edges than on vertical edges was applied to each 2D b‐scan image to further increase signal‐to‐noise ratio thereby increasing the optical penetration . In the edge‐detection approach, the enamel edge, and the lower lesion boundary were determined by applying an edge locator . The program first locates the maximum of each a‐scan, and differentiates the a‐scan maximum as either demineralized or sound using the signal‐to‐noise ratio as a threshold.…”

Enhancement of OCT images with vinyl polysiloxane (VPS)

“…Various imaging analysis methods have been developed for enhancing structures and edges, speckle reduction and denoising OCT images [14–16]. Last year we demonstrated that image processing methods can further improve the visibility of subsurface occlusal lesions [17]. …”

Use of an optical clearing agent to enhance the visibility of subsurface structures and lesions from tooth occlusal surfaces

“…Our recent studies show that the visibility of hidden occlusal lesions can be significantly increased by use of optical clearing agents and image analysis methods. 19,20 Optical clearing agents have routinely been used in biological microscopy and have found recent application in clinical imaging, including OCT. 21,22 We postulate that OCT is ideally suited for monitoring and improving the diagnosis of QOCs, and methods can be developed to enhance the visibility of hidden subsurface lesions. Even though the optical penetration of near-IR light can easily exceed 7 mm through sound enamel to image lesions on proximal surfaces with high contrast, 23 the large increase in light scattering due to demineralization 24 typically limits optical penetration in highly scattering lesions (also dentin and bone) to 1 to 2 mm, thus cutting off the OCT signal before it reaches the dentinal-enamel junction (DEJ).…”