Publications (9)7.62 Total impact
-
Article: Long range extensometer for civil structure monitoring using fibre Bragg gratings
[show abstract] [hide abstract]
ABSTRACT: We report on an extensometer based on fibre Bragg gratings (FBG) which offers a relatively large and high dynamic range for the monitoring of the relative displacement between two adjacent buildings with individual foundations located in an earthquake-prone area. The sensor consists of a sensing FBG subjected to strain and a reference FBG. The fibre containing the strain-sensing FBG is directly surface mounted onto the walls of both buildings, with the fixations ∼1 m apart. A large range of ±20 mm is achieved by desensitization through a tilt of the fibre axis with respect to the displacement vector (∼6 • away from the normal). The sensor is illuminated by a broadband source (SLD with λ 0 = 815 nm) and the reflected signal is monitored directly by a CCD-based optical spectrum analyser. The recorded spectra are curve-fitted to two Gaussian distribution functions on a PC. A precision of 36 µm displacement with an integration time of 3 ms has been achieved.Meas. Sci. Technol. 01/2005; 16:2005-2010. -
Article: Quantification of root caries using optical coherence tomography and microradiography: a correlational study.
[show abstract] [hide abstract]
ABSTRACT: The use of transverse microradiography (TMR) to quantify the amount of mineral lost during demineralization of tooth tissue has long been established. In the present study, the use of an en-face Optical Coherence Tomography (OCT) technology to detect and quantitatively monitor the mineral changes in root caries was investigated and correlated with TMR. We used an OCT system, developed initially for retina imaging, and which can collect A-scans, B-scans (longitudinal images) and C-scans (en-face images) to quantitatively assess the development of root caries. The power to the sample was 250 microW, wavelength lambda = 850 nm and the optical source linewidth was 16 microm. Both the transversal and longitudinal images showed the caries lesion as volumes of reduced reflectivity. Quantitative analysis using the A-scan (reflectivity versus depth curve) showed that the tissue reflectivity decreased with increasing demineralization time. A linear correlation (r = 0.957) was observed between the mineral loss measured by TMR and the percentage reflectivity loss in demineralized tissue measured by OCT. We concluded that OCT could be used to detect incipient root caries, and that the reflectivity loss in root tissue during demineralization, measured by OCT, could be related to the amount of mineral lost during the demineralization.Oral health & preventive dentistry 02/2004; 2(4):377-82. · 0.55 Impact Factor -
Article: Correlation of quantitative light-induced fluorescence and optical coherence tomography applied for detection and quantification of early dental caries.
[show abstract] [hide abstract]
ABSTRACT: Fluorescence loss in enamel following demineralization has been correlated with the amount of mineral lost during the demineralization. The correlation between fluorescence loss measured by quantitative light-induced fluorescence (QLF) and the reflectivity loss measured by a versatile en face optical coherence tomography (OCT) system was investigated in a demineralization process to produce artificial dental caries. We used an OCT system that can collect A-scans (reflectivity versus depth), B-scans (longitudinal images), and C-scans (en face images). The power to the sample was 250 microW, the wavelength lambda = 850 nm, and the depth resolution in air 16 microm. A-scans, which show the profile of the reflectivity versus the depth of penetration into the tooth tissue, were used for quantitative analysis of the reflectivity loss. The results have shown that both the fluorescence radiance and reflectivity of the enamel decrease with increasing de- mineralization time. A linear correlation was observed between the percentage of fluorescence loss measured by QLF and the percentage of reflectivity loss measured by OCT. It was concluded that the decrease in reflectivity of the enamel during demineralization, measured by OCT, could be related to the amount of mineral lost during the de- mineralization process.Journal of Biomedical Optics 11/2003; 8(4):642-7. · 3.16 Impact Factor -
Article: Quasi-simultaneous OCT en-face imaging with two different depth resolutions
[show abstract] [hide abstract]
ABSTRACT: We report a system capable of acquiring two quasi-simultaneous en-face optical coherence tomography (OCT) images of different depth resolution (one better than 20 μm and the other between 80 and 330 μm) at a frame rate of 2 Hz. The larger depth resolution image makes it ideal for target positioning in the OCT imaging of moving organs, such as eye fundus and cornea, as well as in the alignment of stacks of en-face OCT images. This role is similar to that of the confocal channel in a previously reported dual channel OCT/confocal imaging instrument. The system presented operates as a dual channel imaging instrument, where both channels operate on the OCT principle. We illustrate the functionality of the system with examples from a coin, skin from a finger and optic nerve in vivo.Journal of Physics D Applied Physics 07/2003; 36(14):1696. · 2.54 Impact Factor -
Article: International Symposium on Biomedical Optics
[show abstract] [hide abstract]
ABSTRACT: The ability of an en-face Optical Coherence Tomography (OCT) system to detect and quantitatively monitor the demineralization of teeth to produce enamel and dentine (root) caries was determined and validated with an established method of quantifying demineralization, transverse microradiography (TMR). We used an OCT system which can collect A-scans, B-scans (longitudinal images) and C-scans (en-face images). The development of enamel and root caries, by 3-day demineralization in acidic buffer solution, was assessed quantitatively every 24 hours. Caries lesions were shown as volumes of reduced reflectivity in both the transversal and longitudinal images. The A-scan, which showed the levels of reflectivity versus the depth of penetration into the tissue, was used for the quantitative analysis of the lesions. Results demonstrated that the reflectivity of tooth tissue decreased with increasing demineralization time. A linear correlation was observed between the mineral loss in enamel (r=1.0) and dentine (r=0.957) measured by TMR and the percentage reflectivity loss measured by OCT. We concluded that OCT could detect incipient enamel and root caries and quantitatively monitor the demineralization of the tissue. The reflectivity loss in tooth tissue during demineralization, measured by OCT, could be related to the amount of mineral lost during the demineralization.© (2002) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.06/2002; -
Article: Simple very low cost high speed 2 input AND gate
[show abstract] [hide abstract]
ABSTRACT: A low cost subnanosecond AND gate is presented based upon a double‐gate GaAs metal‐oxide semiconductor field‐effect transistor. Applications are presented for ANDing coincident pulses, narrowing pulses (from 310 to 120 ps), and discrimination to improve the operation of a photodetector‐based AND used in the configuration of a fiber optic multichannel correlator. © 1995 American Institute of Physics.Review of Scientific Instruments 10/1995; · 1.37 Impact Factor -
Article: Simultaneous low coherence interferometry imaging at two depths using an integrated optic modulator
[show abstract] [hide abstract]
ABSTRACT: A Mach–Zehnder unbalanced LiNbO3 integrated modulator with independent control of the phase of each arm is incorporated into the reference arm of a low coherence interferometer set-up. Using different RF modulation frequency and processing electronics tuned to these frequencies, the system can be used for simultaneous interrogation of the signal reflected from two different depths in tissue or from two different axial positions in profilometry. When a pair of XY scanning mirrors are incorporated into the sensing arm, then two en-face images from different axial positions can be simultaneously produced. The depth separation between the axial positions of the points or layers interrogated is equal to half of the modulator path difference. The operation of the system is illustrated by displaying simultaneously two images from a coin.Optics Communications. -
Article: Versatile optical coherence tomography system applied for imaging of teeth
[show abstract] [hide abstract]
ABSTRACT: The utility of a versatile multifunctional standalone Optical Coherence Tomography (OCT)/confocal system for imaging dental tissue was investigated. The system can collect A-scan (reflectivity versus depth graph), longitudinal (B-scan) and en-face (C-scan) OCT images, simultaneously with a confocal image. The power to the sample was 250 jiW, wavelength x= 850 am and the depth resolution in air was 16 jm. The OCT images showed caries lesions as volumes of reduced reflectivity. Transversal images (C-scan) showed the en-face slices of the tooth tissue like in confocal microscopy. Longitudinal images showed the depth ofthe lesion into the tooth tissue as well as the different structural layers of sound tooth in the same way as seen in ultrasound images. A-scans preformed in locations selected in the en-face images provided quantitative data about the reflectivity versus depth. The confocal channel was extremely useful for guidance and it has also shown the integral of the intensity over depth at transversal locations. We concluded that OCT proved capable to detect an early caries lesion, to show the depth of the lesion into the tissue, and quantitatively assess the degree of demineralisation. -
Article: Optical coherence tomography correlated with a functional fluorescence imaging for detection and quantification of dental caries
[show abstract] [hide abstract]
ABSTRACT: Fluorescence radiance loss in enamel following demineralisation has been correlated to the amount of mineral lost during the demineralisation. The correlation between fluorescence loss measured by Quantitative Light-induced Fluorescence (QLF) and the reflectivity loss measured by an en-face Optical Coherence Tomography (OCT) system was investigated in a demineralisation process to produce artificial caries. We used an OCT system which can collect Ascans (reflectivity versus depth graph), B-scans (longitudinal images) and C-scans (en-face images). The power to the sample was 250 j.tW, wavelength 7 = 850 nm and the depth resolution in air 16 j.tm. Transversal and longitudinal images showed the caries lesion as volumes of reduced reflectivity. A-scans, which show the profile of the reflectivity versus depth of penetration into the tooth tissue, were used for quantitative analysis of the reflectivity loss. Both the fluorescence radiance and reflectivity of the enamel decreased with increasing demineralisation time. A linear correlation was observed between the percentage fluorescence loss measured by QLF and the percentage reflectivity loss measured by OCT. It was concluded that the decrease in reflectivity of the enamel during demineralisation, measured by OCT, could be related to the amount of mineral lost during the demineralisation process
Top co-authors
Top Journals
Institutions
-
2003–2004
-
University of Texas Health Science Center at San Antonio
San Antonio, TX, USA -
University of Kent
- School of Physical Sciences
Canterbury, ENG, United Kingdom
-
