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At least 1,027 records · Page 57Linked to original sources
PubMed2006

52 mJ narrow-bandwidth degenerated optical parametric system with a large-aperture periodically poled MgO:LiNbO3 device.

We have demonstrated efficient, high-energy, narrow-spectral-bandwidth 2.128 microm pulse generation by use of periodically poled MgO:LiNbO3 devices with a 36 mm length and a 5 mm x 5 mm large aperture. A free-running degenerated optical parametric oscillator (OPO) pumped with a Q-switched 1.064 microm Nd:YAG laser exhibits a high slope efficiency of 75% and an optical-to-optical conversion efficiency of 70% with a broad spectral bandwidth (>100 nm). In a configuration with a spectrally narrowed master oscillator followed by a power amplifier, we have achieved an output pulse energy of 52 mJ with a spectral bandwidth of less than 2 nm at the degeneracy point. The total optical-to-optical conversion efficiency of the system reached 50%.

Journal Article↗
PubMed1999

Phase-separated composite films for liquid crystal displays

A method of preparing liquid crystal devices by phase separation of liquid crystal from its solution in a prepolymer, which results in adjacent layers of liquid crystal and polymer, is described. Liquid crystals in these phase-separated composite films exhibit electro-optical properties not observed in devices prepared by conventional methods, polymer dispersion, or polymer-stabilization methods. Devices incorporating ferroelectric liquid crystals have gray scale and switch 100 times faster at low fields than conventional surface-stabilized devices. This method makes it possible to prepare devices with liquid crystal film thickness comparable to optical wavelengths.

Journal Article↗
PubMed2001

A new system for digital image acquisition, storage and presentation in an accident and emergency department.

OBJECTIVES: To develop a computer based storage system for clinical images-radiographs, photographs, ECGs, text-for use in teaching, training, reference and research within an accident and emergency (A&E) department. Exploration of methods to access and utilise the data stored in the archive. METHODS: Implementation of a digital image archive using flatbed scanner and digital camera as capture devices. A sophisticated coding system based on ICD 10. Storage via an "intelligent" custom interface. RESULTS: A practical solution to the problems of clinical image storage for teaching purposes. CONCLUSIONS: We have successfully developed a digital image capture and storage system, which provides an excellent teaching facility for a busy A&E department. We have revolutionised the practice of the "hand-over meeting".

Computer Security↗
PubMed2003

Use of a night vision intensifier for direct visualization by eye of far-red and near-infrared fluorescence through an optical microscope.

We describe the design, construction and testing of a prototype device that allows the direct visualization by eye of far-red and near-infrared (NIR) fluorescence through an optical microscope. The device incorporates a gallium arsenide (GaAs) image intensifier, typically utilized in low-light or 'night vision' applications. The intensifier converts far-red and NIR light into electrons and then into green light, which is visible to the human eye. The prototype makes possible the direct, real-time viewing by eye of normally invisible far-red and NIR fluorescence from a wide variety of fluorophores, using the full field of view of the microscope to which it is applied. The high sensitivity of the image intensifier facilitates the viewing of a wide variety of photosensitive specimens, including live cells and embryos, at vastly reduced illumination levels in both fluorescence and bright-field microscopy. Modifications to the microscope are not required in order to use the prototype, which is fully compatible with all current fluorescence techniques. Refined versions of the prototype device will have broad research and clinical applications.

Animals↗
PubMed2001

A hierarchical storage management (HSM) scheme for cost-effective on-line archival using lossy compression.

A hierarchical storage management (HSM) scheme for cost-effective on-line archival of image data using lossy compression is described. This HSM scheme also provides an off-site tape backup mechanism and disaster recovery. The full-resolution image data are viewed originally for primary diagnosis, then losslessly compressed and sent off site to a tape backup archive. In addition, the original data are wavelet lossy compressed (at approximately 25:1 for computed radiography, 10:1 for computed tomography, and 5:1 for magnetic resonance) and stored on a large RAID device for maximum cost-effective, on-line storage and immediate retrieval of images for review and comparison. This HSM scheme provides a solution to 4 problems in image archiving, namely cost-effective on-line storage, disaster recovery of data, off-site tape backup for the legal record, and maximum intermediate storage and retrieval through the use of on-site lossy compression.

Algorithms↗
PubMed2006

Quality assessment of confocal microscopy slide-based systems: instability.

BACKGROUND: All slide-based fluorescence cytometry detections systems basically include an excitation light source, intermediate optics, and a detection device (CCD or PMT). Occasionally, this equipment becomes unstable, generating unreliable and inferior data. METHODS: A number of tests have been devised to evaluate equipment performance and instability. The following four instability tests are described: galvanometer scanning, stage drift, correct wavelength spectral detection, and long-term laser power. RESULTS: Quality assurance tests revealed that a confocal microscope can become unstable in the following parameters, yielding inaccurate data: laser power, PMTs functionality, spectrophotometer accuracy, galvanometer scanning and laser stability, and stage drift. Long-term laser power stability has been observed to vary greatly. CONCLUSIONS: Confocal systems can become unstable in the following parameters: long-term laser power, galvanometer scanning, spectrophotometer accuracy, and stage stability. Instability in any of these parameters will affect image quality. Laser power fluctuations result from either a defective Acousto-optic tunable filter or improper heat dissipation. Spectrophotometer instability will generate unreliable spectra data, extra light reflections, and poor image quality. Galvanometer scanning instability yields poor image quality while microscope stage drift results in a sample going out of the plane of focus. With minor modifications, these tests may be applicable to other slide-based systems.

Animals↗
PubMedDate not supplied

Label-free measurement of microbicidal gel thickness using low-coherence interferometry.

Spectral-domain low-coherence interferometry (LCI) was used to measure the thickness of microbicidal gels applied to a cylindrical calibration test socket. Microbicides are topical formulations containing active ingredients targeted to inhibit specific pathogens that are currently under development for application to the epithelial lining of the lower female reproductive tract to combat sexually transmitted infections such as HIV. Understanding the deployment and drug delivery of these formulations is vital to maximizing their effectiveness. Previously, in vivo measurements of microbicidal formulation thickness were assessed using fluorescence measurements of fluorescein-labeled gels via an optical endoscope-based device. Here we present an LCI-based device that measures the thickness of a formulation without the use of any exogenous agents by analyzing the interference pattern generated between the reflections from the front and back surface of the sample. Results are presented that validate the effectiveness and performance of the LCI measurement in a clinically relevant system as compared to an existing fluorescence-based method. The impact of the new LCI-based design on in vivo measurements is discussed.

Anti-Infective Agents↗
PubMed2006

One-dimensional to two-dimensional channel formatting with micro-optics for wavelength division multiplexing networks.

We present a method of interfacing a conventional wavelength multiplexing and demultiplexing device with a two-dimensional (2-D) array of surface-active elements, such as micro-electromechanical system devices or photodetectors. We use diffractive optical elements to transform wavelength division multiplexed signals spread along a line into a 2-D array. We applied this technique to build a device that is compatible with an arrayed-waveguide grating. The theoretical insertion loss predicted by combining beam propagation and rigorous coupled-wave analysis is 2.75 dB. However, the experimental loss is 10 dB. The difference is due to the poor quality of the diffraction gratings. Nevertheless, the formatting operation was performed successfully.

Journal Article↗
PubMed2003

Imaging scleral expansion bands for presbyopia with optical coherence tomography.

A 57-year-old woman was treated for mild presbyopia with implantation of scleral expansion bands (SEB). Although near vision was temporarily restored, the effect dissipated after 1 year. Slitlamp-adapted optical coherence tomography (OCT) at 1310 nm allowed precise cross-sectional visualization of the hyporeflective intrascleral segments. The OCT method provided precise images of the segment depth and thickness, the scleral thickness at the scleral spur, the anterior chamber angle, and the angle-opening distance. Intrascleral tilting of 1 segment was seen; this required removal of the SEB because of marked foreign-body sensation. Noncontact, slitlamp-adapted OCT can be used to evaluate scleral changes after SEB implantation.

Female↗
PubMed2002

Use of visual screening methods for cervical cancer screening.

This article has considered recent advances in visual screening methods. Devices that use electro-optical sensors offer great potential in various clinical roles, but considerable additional work is required to develop these devices and it is unlikely that they will come into widespread clinical use in the next 5 years. In contrast numerous studies, demonstrate that simple visual screening methods, such as DVI, have a sensitivity for the detection of women with biopsy-confirmed high-grade SIL (CIN 2,3) and cancer that is equivalent to that of conventional cervical cytology. The primary disadvantage of the simple visual screening methods is poor specificity. These methods classify up to 30% of all women screened as being test positive and as a result new strategies toward managing DVI positive women must be developed before simple visual screening methods can be adopted for routine screening. Enhanced visual methods that use cervicography and speculoscopy may be more specific and improve detection of biopsy-confirmed SIL, but the added time and expense to perform either of these methodologies must be considered and justified. Currently numerous studies are evaluating the best strategies for incorporating visual screening methods into cervical cancer screening programs. In the near future we should be able to determine whether these approaches should be incorporated into routine clinical care.

Acetic Acid↗
PubMed2002

Experience with optical trocar in performing laparoscopic procedures.

We report on the results of laparoscopic procedures in 1187 patients with use of the OPTIVIEW Optical Surgical Obturator, a device that permits visually guided trocar entry without insufflation. Most of these procedures (78%) involved hiatal hernia repairs, and 51% of our patients had a history of previous abdominal procedures. Visualization and pneumoperitoneum were successfully achieved in all patients, including those who had previously undergone multiple upper-midline abdominal procedures. There were three trocar-related injuries and one late complication (0.3%), including two bowel injuries repaired at the time of initial surgery, a mesenteric injury repaired with a clip applier, and an incisional hernia that resulted from placement of the trocar at midline instead of paramedian. Results of this large series indicate that trocar-related complications associated with use of the OPTIVIEW trocar are rare.

Abdomen↗
PubMed1994

Integration of ultrasound in a fully digital radiology department.

OBJECTIVES: The authors' experiences concerning the use of video-framegrabbers for the integration of ultrasound devices into a fully digital imaging environment are presented. METHODS: Video acquisition workstations (VAW) (Siemens, Gammasonics Inc., Hoffman Estates, IL) are used in our department to link ultrasound devices to the picture archiving and communication system (PACS). A study was carried out concerning the impact of this integration on throughput by comparing the average times for image acquisition and storage in this digital system with the times found in a conventional archive, which is still used for some ultrasound units. The annual costs for the two kinds of archives were compared. RESULTS AND CONCLUSION: Video acquisition is a feasible way of integrating ultrasound in a digital environment. No impact on throughput has been found for the radiologist carrying out the examination, but for the assisting technologist, the times for image retrieval and archiving could be reduced from 3 minutes and 8 seconds to 24 seconds per patient. The instant availability of previous studies could be increased from 93.5% to almost 100%. Archive costs could be reduced by 28%, with further reductions to be expected using different archive configurations.

Austria↗
PubMed2004

Advances in optical coherence tomography imaging for dermatology.

Optical coherence tomography (OCT) is a non-invasive imaging technique, which has previously demonstrated potential for use in dermatology. The purpose of this study is to demonstrate how improvements in image quality, speed, and functionality enable qualitative and quantitative information to be obtained from in vivo human skin. We developed a portable fiber-optic based OCT imaging device that requires only 1 second to simultaneously provide high-resolution images of skin structure, collagen birefringence, and blood flow. Images of normal human skin were acquired in vivo, and features compared with clinical and histologic observations. The layered structure and appendages of skin were apparent in conventional OCT images, and correlated well with corresponding histology. Polarization-sensitive OCT images simultaneously revealed birefringent regions within the dermis corresponding to the location of collagen fibers, as confirmed with polarized light microscopy. Properties of collagen-rich tissues including tendon and scar tissues were quantified. Location of blood flow was also displayed alongside structural and polarization-sensitive images. Significant improvements in OCT technology have been made since its early application in dermatology. In particular, combining the previously described structural and Doppler imaging functions with polarization-sensitive imaging increases the utility of the technique for rapid, non-invasive investigations in the skin.

Cicatrix↗
PubMed2004

High-power blue/UV light-emitting diodes as excitation sources for sensitive detection.

With advances in III-V nitride manufacturing processes, high-power light-emitting diode (LED) chips in the blue and UV wavelengths are now commercially available at reasonable cost and can be used as excitation sources in optical sensing. We describe the use of these high-power blue and UV LEDs for sensitive fluorescence detection, including chip-based flow cytometry, capillary electrophoresis (CE), and single-molecule imaging. By using a blue LED with a focusable power of approximately 40 mW as the excitation source for fluorescent beads, we demonstrate a simple chip-based bead sorter capable of enriching the concentration of green fluorescent beads from 63% to 95%. In CE experiments, we show that a mixture of analyte solution containing 30 nM 6-carboxyrhodamine 6G and 10 nM fluorescein can be separated and detected with excellent signal-to-noise ratio (approximately 17 for 10 nM fluorescein) using the collimated emission from a blue LED; the estimated mass detection limit was approximately 200 zmol for fluorescein. We also demonstrated ultrasensitive fluorescence imaging of single rhodamine 123 molecules and individual lambda-DNA molecules. At a small fraction of the cost of an Ar+ laser, high-power blue and UV LEDs are effective alternatives for lasers and arc lamps in fluorescence applications that demand portability, low cost, and convenience.

Cells↗
PubMed2004

Microfluidic sorting of mammalian cells by optical force switching.

Microfluidic-based devices have allowed miniaturization and increased parallelism of many common functions in biological assays; however, development of a practical technology for microfluidic-based fluorescence-activated cell sorting has proved challenging. Although a variety of different physical on-chip switch mechanisms have been proposed, none has satisfied simultaneously the requirements of high throughput, purity, and recovery of live, unstressed mammalian cells. Here we show that optical forces can be used for the rapid (2-4 ms), active control of cell routing on a microfluidic chip. Optical switch controls reduce the complexity of the chip and simplify connectivity. Using all-optical switching, we have implemented a fluorescence-activated microfluidic cell sorter and evaluated its performance on live, stably transfected HeLa cells expressing a fused histone-green fluorescent protein. Recovered populations were verified to be both viable and unstressed by evaluation of the transcriptional expression of two genes, HSPA6 and FOS, known indicators of cellular stress.

Cell Separation↗
PubMed2000

Effects of nicotinamide and carbogen on oxygenation in human tumor xenografts measured with luminescense based fiber-optic probes.

BACKGROUND AND PURPOSE: In head and neck cancer, addition of both carbogen breathing and nicotinamide to accelerated fractionated radiotherapy showed increased loco-regional control rates. An assay based on the measurement of changes in tumor pO(2) in response to oxygenation modification could be helpful for selecting patients for these new treatment approaches. MATERIALS AND METHODS: The fiber-optic oxygen-sensing device, OxyLite, was used to measure changes in pO(2), at a single position in tumors, after treatment with nicotinamide and carbogen in three human xenograft tumor lines with different vascular architecture and hypoxic patterns. Pimonidazole was used as a marker of hypoxia and was analyzed with a digital image processing system. RESULTS: At the position of pO(2) measurement, half of the tumors showed a local increase in pO(2) after nicotinamide administration. Steep increases in pO(2) were measured in most tumors during carbogen breathing although the increase was less pronounced in tumor areas with a low pre-treatment pO(2). A trend towards a faster local response to carbogen breathing for nicotinamide pre-treated tumors was found in all three lines. There were significant differences in hypoxic fractions, based on pimonidazole binding, between the three tumor lines. There was no correlation between hypoxic marker binding and the response to carbogen breathing. CONCLUSION: Temporal changes in local pO(2) can be measured with the OxyLite. This system was used to quantitate the effects of oxygen modifying treatments. Rapid increases in pO(2) during carbogen breathing were observed in most tumor areas. The locally measured response to nicotinamide was smaller and more variable. Bio-reductive hypoxic cell marker binding in combination with OxyLite pO(2) determination gives spatial information about the distribution patterns of tumor hypoxia at the microscopic level together with the possibility to continuously measure changes in pO(2) in specific tumor areas.

Analysis of Variance↗
PubMed2003

Temporal heterogeneity in oxygen tension in human melanoma xenografts.

The spatial heterogeneity of the oxygen tension (pO(2)) in human and experimental tumours has been studied extensively, whereas studies of the temporal heterogeneity in pO(2) are sparse. In the work reported here, pO(2) was measured continuously over periods of at least 60 min in A-07 human melanoma xenografts by using the OxyLite fibre-optic oxygen-sensing device. The main purpose of the work was to establish the usefulness of the OxyLite system in measuring the temporal heterogeneity in pO(2) in tissues and to characterise the fluctuations in tissue pO(2) in A-07 tumours. The OxyLite device was found to be suitable for studies of the temporal heterogeneity in pO(2) in tumours. However, potential pitfalls were identified, and reliable pO(2) measurements require that precautions are taken to avoid these pitfalls, that is, erroneous pO(2) readings caused by tissue trauma induced by the probe, probe movements induced by reflex actions of the host mouse and occasional probe drift. Significant fluctuations in pO(2) were detected in the majority of the 70 tumour regions subjected to measurement. The fluctuations in different regions of the same tumour were in general temporally independent, implying that they were caused primarily by redistribution of the tumour perfusion rather than fluctuations in global perfusion. Fourier analysis of the pO(2) traces showed that the pO(2) usually fluctuated at frequencies lower than 1.5-2.0 mHz, corresponding to less than 0.1 cycle min(-1). Haemodynamic effects may cause pO(2) fluctuations in this frequency range, and hence, the redistribution of the perfusion could have been caused by morphological abnormalities of the tumour microvasculature. Moreover, acute hypoxia, that is, pO(2) fluctuations around 10 or 5 mmHg, was detected in 20 of 70 regions, that is, 29% (10 mmHg), or 27 of 70 regions, that is, 39% (5 mmHg). The median fraction of the time these regions were acutely hypoxic was 73% (10 mmHg) or 53% (5 mmHg). Consequently, if A-07 tumours are adequate models of tumours in man, acute hypoxia may be a commonly occurring phenomenon in neoplastic tissues, and hence, acute hypoxia is likely to cause resistance to radiation therapy and promote tumour aggressiveness.

Animals↗
PubMedDate not supplied

Storage options for the healthcare enterprise.

The storage objectives for the healthcare enterprise (HE) are to ensure that information (images and data) are readily available anywhere and at anytime, images and data are secure, and the storage fulfills legal requirements and the Health Insurance Portability and Accountability Act (HIPAA). These objectives must be satisfied at a minimum economic cost with respect to personnel, hardware, software, space and telecommunications. Many approaches and storage configurations meet these objectives. Which approach is chosen will depend on the size of the institution, patient population, geographic distribution of the institutions (if more than one), type of facility (such as a hospital, outpatient clinic or private imaging center), and financial investment objectives. The quantity of storage required depends on the characteristics of the modalities, the number of imaging devices and databases, the number and location of imaging sites that make up the HE, the size of the data and image, and the projected procedure volume growth. The only certainty with respect to storage requirements is that they will increase significantly with time. The types of storage required in the HE can be described by their functions: Active storage includes both online and long-term storage. Backup images are temporarily backed up on the limited storage capacity of the modality for several days or longer. Additional copies of the study are made on different media (e.g., disk, DVD or tape), in different locations. The process of backing up data and images must be automated. Effective April 21, 2005, HIPAA requires that all healthcare entities have a disaster recovery plan in effect. This requires that a copy of all medical data be secure, retrievable and maintained in a second location, such that if the primary copy of the data is destroyed or made unavailable, the disaster recovery copy would be available. Planning for the HE archive is critical if the HE is to work productively in an integrated digital environment. The information technology department must be an integral part of planning for the HE archive, which must be located in a secure data center and not under the management of any single clinical department. After the technologies currently available are evaluated, it is imperative that the chosen solution is cost-effective and scalable, and that it will allow the HE to take advantage of future storage and storage management technology.

Archives↗