Rongguang Liang

Multimodal imaging system for dental caries detection

Dental caries is a disease in which minerals of the tooth are dissolved by surrounding bacterial plaques. A caries process present for some time may result in a caries lesion. However, if it is detected early enough, the dentist and dental professionals can implement measures to reverse and control caries. Several optical, nonionized methods have been investigated and used to detect dental caries in early stages. However, there is not a method that can singly detect the caries process with both high sensitivity and high specificity. In this paper, we present a multimodal imaging system that combines visible reflectance, fluorescence, and Optical Coherence Tomography (OCT) imaging. This imaging system is designed to obtain one or more two-dimensional images of the tooth (reflectance and fluorescence images) and a three-dimensional OCT image providing depth and size information of the caries. The combination of two- and three-dimensional images of the tooth has the potential for highly sensitive and specific detection of dental caries.

A compact NIR fluorescence imaging system with goggle display for intraoperative guidance

Near infra-red (NIR) fluorescence imaging offers high sensitivity and specificity for cancer detection and tumor margin localization. In this paper, a compact and wearable NIR fluorescence imaging system (FIS) for image guided surgery is presented. The proposed FIS captures 27 frames per second of both NIR and visible spectrum data, allowing for minimum detection of 10nM of ICG concentration. The design tradeoffs of the complete system are carefully analyzed. The performance of the proposed FIS is evaluated under both sensitivity test and experimental mouse study. The imaging system is currently used in clinical trials for imaging sentinel lymph nodes in breast cancer and melanoma patients.

Intraoperative imaging and fluorescence image guidance in oncologic surgery using a wearable fluorescence goggle system

We have developed a wearable, fluorescence goggle based system for intraoperative imaging of tumors and image guidance in oncologic surgery. Our system can detect fluorescence from cancer selective near infra-red (NIR) contrast agent, facilitating intraoperative visualization of surgical margins and tumors otherwise not apparent to the surgeon. The fluorescence information is displayed directly to the head mounted display (HMD) of the surgeon in real time, allowing unhindered surgical procedure under image guidance. This system has the potential of improving surgical outcomes in oncologic surgery and reduce the chances of cancer recurrence.

System design and evaluation of the array confocal fluorescence microscope

The scanning speed for conventional confocal fluorescence imaging systems is limited due to several factors. To improve the speed of scanning, we develop an array confocal fluorescence microscope (ACFM) that can image large 3D volumes faster than conventional confocal microscopes over a large field of view (FOV). This paper will discuss the design and evaluation of the array confocal fluorescence microscope.

Optical design of a multimodal imaging system

A multimodal imaging system has been developed for tooth tissue imaging. This imaging system is designed to obtain one or more two-dimensional images of the tooth tissue, and those two-dimensional images are rendered with advanced algorithms to provide a high-contrast image. This system combines polarized reflectance imaging, fluorescence imaging, and optical coherence tomography (OCT) imaging. The imaging system design, as well as some experimental results, will be discussed in the presentation.

Development of a dual-modality, dual-view smartphone-based imaging system for oral cancer detection

Oral cancer is a rising health issue in many low and middle income countries (LMIC). Proposed is an implementation of autofluorescence imaging (AFI) and white light imaging (WLI) on a smartphone platform providing inexpensive early detection of cancerous conditions in the oral cavity. Interchangeable modules allow both whole mouth imaging for an overview of the patients’ oral health and an intraoral imaging probe for localized information. Custom electronics synchronize image capture and external LED operation for the excitation of tissue fluorescence. A custom Android application captures images and an image processing algorithm provides likelihood estimates of cancerous conditions. Finally, all data can be uploaded to a cloud server where a convolutional neural network classifies the images and a remote specialist can provide diagnosis and triage instructions.

Depth-of-focus extended chromatic dual-foci OCT (Conference Presentation)

The depth scanning range of high-resolution OCT is limited by its depth-of-focus (DOF). To solve this problem, we developed a chromatic dual-foci technology to maintain a transverse resolution of 1-2 um over a DOF of about 300 micrometers, which is 2-3 times larger than the single-focus OCT system. In this OCT system, a supercontinuum source is used to provide illumination from 700 to 1600 nm. The interference fringe is detected by a dual-spectrometer system, which engages a Si camera and an InGaAs camera. The Si camera detects the spectral single from 700 to 950 nm, and InGaAs camera covers 1100 to 1600 nm spectral range. As the focal region for long wavelength section is deeper than the short one, the two spectral sections are processed separately to form two OCT images of different depths in the sample. After combining the two images, we obtained DOF extended OCT images.

Visibility of solid and liquid fiducial markers used for image-guided radiation therapy on optical coherence tomography: an esophageal phantom study (Conference Presentation)

Radiation therapy (RT) is used in operable and inoperable esophageal cancer patients. Endoscopic ultrasound-guided fiducial marker placement allows improved translation of the disease extent on endoscopy to computed tomography (CT) images used for RT planning and enables image-guided RT. However, microscopic tumor extent at the time of RT planning is unknown. Endoscopic optical coherence tomography (OCT) is a high-resolution (10-30µm) imaging modality with the potential for accurately determining the longitudinal disease extent. Visibility of fiducial markers on OCT is crucial for integrating OCT findings with the RT planning CT. We investigated the visibility on OCT (NinePoint Medical, Inc.) of 13 commercially available solid (Visicoil, Gold Anchor, Flexicoil, Polymark, and QLRAD) and liquid (BioXmark, Lipiodol, and Hydrogel) fiducial markers of different diameter. We designed and manufactured a set of dedicated Silicone-based esophageal phantoms to perform imaging in a controlled environment. The esophageal phantoms consist of several layers with different TiO2 concentrations to simulate the scattering properties of a typical healthy human esophagus. Markers were placed at various depths (0.5, 1.1, 2.0, and 3.0mm). OCT imaging allowed detection of all fiducial markers and phantom layers. The signal to background ratio was 6-fold higher for the solid fiducial markers than the liquid fiducial markers, yet OCT was capable of visualizing all 13 fiducial markers at all investigated depths. We conclude that RT fiducial markers can be visualized with OCT. This allows integration of OCT findings with CT for image-guided RT.

Surgical instrument biocontaminant fluorescence detection in ambient lighting conditions for hospital reprocessing and sterilization department (Conference Presentation)

Hospitals currently rely on simple human visual inspection for assessing cleanliness of surgical instruments. Studies showed that surgical site infections are in part attributed to inadequate cleaning of medical devices. Standards groups recognize the need to objectively quantify the amount of residues on surgical instruments and establish guidelines. We developed a portable technology for the detection of contaminants on surgical instruments through fluorescence following cleaning. Weak fluorescence signals are usually detected in the obscurity only with the lighting of the excitation source. The key element of this system is that it works in ambient lighting conditions, a requirement to not disturb the normal workflow of hospital reprocessing facilities. A biocompatible fluorescent dye is added to the detergent and labels the proteins of organic residues. It is resistant to the harsh environment in a washer-disinfector. Two inspection devices have been developed with a 488nm laser as the excitation source: a handheld scanner and a tabletop station using spectral-domain and time-domain ambient light cancellation schemes. The systems are eye safe and equipped with image processing and interfacing software to provide visual or audible warnings to the operator based on a set of adjustable signal thresholds. Micron-scale residues are detected by the system which can also evaluate soil size and mass. Unlike swabbing, it can inspect whole tools in real-time. The technology has been validated in an independent hospital decontamination research laboratory. It also has potential applications in the forensics, agro-food, and space fields. Technical aspects and results will be presented and discussed.

Fast searching measurement of absolute displacement based on submicron-aperture fiber point-diffraction interferometer

The submicron-aperture fiber point-diffraction interferometer (SFPDI) can be applied to realize the measurement of three-dimensional absolute displacement within large range, in which the performance of point-diffraction wavefront and numerical iterative algorithm for displacement reconstruction determines the achievable measurement accuracy, reliability and efficiency of the system. A method based on fast searching particle swarm optimization (FS-PSO) algorithm is proposed to realize the rapid measurement of three-dimensional absolute displacement. Based on the SFPDI with two submicron-aperture fiber pairs, FS-PSO method and the corresponding model of the SFPDI, the measurement accuracy, reliability and efficiency of the SFPDI system are significantly improved, making it more feasible for practical application. The effect of point-diffraction wavefront error on the measurement is analyzed. The error of pointdiffraction wavefront obtained in the experiment is in the order of 1×10-4λ (the wavelength λ is 532 nm), and the corresponding displacement measurement error is smaller than 0.03 μm. Both the numerical simulation and comparison experiments have been carried out to demonstrate the accuracy and feasibility of the proposed SFPDI system, high measurement accuracy in the order of 0.1 μm, convergence rate (~90.0%) and efficiency have been realized with the proposed method, providing a feasible way to measure three-dimensional absolute displacement in the case of no guide rail.