In response to a broad-based need for point-of-care multiplex diagnostic capability, we have developed a novel hybrid platform to analyze optically encoded microspheres arranged on a 2-dimensional planar array. The microspheres which we have initially selected are developed by Luminex Inc. as substrates for sandwich-type fluorescent immunoassays and are typically used in conjunction with a customized flow analyzer. CCD-based optics are the essential feature which enables the development of a rugged diagnostic instrument which can be scaled for point-of-care applications. We have characterized the Multiplex Immunoassay Diagnostic System (MIDS) using a benchtop prototype built around a conventional 12-bit CCD. This system is capable of resolving up to 6 discrete classes of fluorescent microbeads, and measuring their corresponding reporter signal. The MIDS sensitivity to the phycoerythrin (PE) reporter compared favorably to that of the reference Luminex flow system, and is capable of identifying viral, bacterial, and protein simulants in laboratory samples, at concentrations less than 1μg/ml. The ability to
resolve small differences in the average PE fluorescence is a direct function of CCD performance, and may be a necessary trade-off for developing a portable and economical detection system. However, we are
confident that the MIDS platform can easily be scaled to meet the nominal requirements of any given point-of-care or screening application, and furthermore provide much-needed diagnostic functionality in this particular environment.
The purpose of this initial study was to begin development of a new, objective diagnostic instrument that will allow simultaneous quantitation of multiple proteases within a single periodontal pocket using a chemical fiber optic senor. This approach could potentially be adapted to use specific antibodies and chemiluminescence to detect and quantitate virtually any compound and compare concentrations of different compounds within the same periodontal pocket. The device could also be used to assay secretions in salivary ducts or from a variety of wounds. The applicability is, therefore, not solely limited to dentistry and the device would be important both for clinical diagnostics and as a research too.
The laser-tissue interaction code LATIS is used to analyze photon scattering histories representative of optical coherence tomography (OCT) experiments performed at Lawrence Livermore National Laboratory. Monte Carlo photonics with Henyey-Greenstein anisotropic scattering is implemented and used to simulate signal discrimination of intravascular structure. An analytic model is developed and used to obtain a scaling law for optimization of the OCT signal and to validate Monte Carlo photonics. The appropriateness of the Henyey-Greenstein phase function is studied by direct comparison with more detailed Mie scattering theory using an ensemble of spherical dielectric scatterers. Modest differences are found between the two prescription for describing photon angular scattering in tissue. In particular, the Mie scattering phase functions provide less overall reflectance signal but more signal contrast compared to the Henyey-Greenstein formulation.
There is no diagnostic technology presently available utilizing non-ionizing radiation that can image the state of demineralization of dental enamel in vivo for the detection, characterization and monitoring of early, incipient caries lesions. In this study, a Polarization Sensitive Optical Coherence Tomography (PS-OCT) system was evaluated for its potential for the non-invasive diagnosis of early carious lesions. We demonstrated clear discrimination in PS-OCT imags between regions of normal and demineralized enamel in bovine enamel blocks containing well-characterized artificial lesions. Moreover, high-resolution, cross- sectional images were acquired that clearly discriminate between the normal and carious regions of extracted human teeth. Regions that appeared to be demineralized in the PS- OCT imags were verified using histological thin sections examined under polarized light. The PS-OCT system discriminates between normal and carious regions by measuring the state of polarization of the back-scattered 1310 nm light, which is affected by the state of demineralization of the enamel. The demineralized regions of enamel have a large scattering coefficient, thus depolarizing the incident light. This initial study shows that PS-OCT has great potential for the detection, characterization, and monitoring of incipient caries lesions.
We have developed a hand-held fiber optic based optical coherence tomography (OCT) system for scanning of the oral cavity. We have produced, using this scanning device, in vivo cross-sectional images of hard and soft dental tissues in human volunteers. Clinically relevant anatomical structures, including the gingival margin, periodontal sulcus, and dento- enamel junction, were visible in all the images. The cemento- enamel junction and the alveolar bone were identified in approximately two thirds of the images. These images represent, or our knowledge, the first in vivo OCT images of human dental tissue.
A polarization sensitive optical coherence tomography (OCT) system is developed and used to measure birefringence in porcine myocardium tissue, producing 2-D cross-sectional images of the tissue birefringence. These birefringence images are then used to quantify thermal damage in the tissue. Signal to noise issues which cause systematic measurement errors are analyzed to determine the regime in which such measurements are accurate. The advantage of polarization sensitive OCT systems over standard OCT systems in avoiding image artifacts caused by birefringence is also demonstrated.
We have developed a hand-held in vivo scanning device for use in the oral cavity. We produced, using this scanning device, in vivo OCT images of dental tissues in human volunteers. All the OCT images were analyzed for the presence of clinically relevant anatomical structures. The gingival margin, periodontal sulcus, and dento-enamel junction were visible in all the images. The cemento-enamel junction was discernible in 64% of the images and the alveolar bone presumptively identified for 71% of the images. These images represent, to our knowledge, the first in vivo OCT images of human dental tissue.
We have, in this preliminary study, investigated the use of optical coherence tomography for diagnosis of periodontal disease. We took in vitro OCT images of the dental and periodontal tissues from a young pig and compared them to histological sections. These images distinguish tooth and soft tissue relationships that are important in diagnosing and assessing periodontal disease. We have imaged the attachment of gingiva to the tooth surface and located the cemento-enamel junction. This junction is an important reference point for defining attachment level in the diagnosis of periodontal disease. the boundary between enamel and dentin is also visible for most of the length of the anatomical crown, allowing quantitation of enamel thickness and character.
We have developed a fiber-optic chemical sensor technology for the remote monitoring of various volatile solvents. The accuracy, linearity, and sensitivity of the sensor (<5 ppb by weight in water, determined by comparison with standard gas chromatographic measurements) are sufficient for environmental monitoring of at least trichloroethlyene (TCE) and chloroform.
A fiber optic chemical sensor has been designed for groundwater and vadose zone monitoring of volatile halogenated hydrocarbons. The principle of detection is a quantitative, irreversible chemical reaction that forms visible light absorbing products. This absorption is measured remotely using fiber optics. Modifications of our previous sensor design have resulted in lower detection limits and increased durability. In this paper we describe the measurement system and present the new sensor design along with calibration data and preliminary field test results.
We have developed a differential-absorption fiber-optic sensor for use in groundwater and vadose zone monitoring of certain volatile organochiorides. The principle of detection is a quantitative irreversible chemical reaction that forms visible light-absorbing products. The sensor has been evaluated against gas chromatographic (GC) standard measurements and has demonstrated accuracy and sensitivity sufficient for the environmental monitoring of trace levels of trichioroethylene (TCE) and chloroform. This sensor is currently under evaluation in monitoring well and vadose zone applications. In this paper we describe the principles of the existing single measurement sensor technology and show preliminary field test results.