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At least 217 records · Page 12Linked to original sources
PubMed2006

Fourier-domain angle-resolved low coherence interferometry through an endoscopic fiber bundle for light-scattering spectroscopy.

We present a novel endoscopic fiber bundle probe incorporated in a Fourier-domain angle-resolved low coherence interferometry system for the measurement of depth-resolved angular scattering distributions to permit the determination of scatterer size via elastic scattering properties. Depth resolution is achieved with a superluminescent diode via a Mach-Zehnder interferometer. The sample is illuminated with a collimated beam, and a Fourier plane image of the backscattered light is collected by a coherent fiber bundle. The angular scattering distribution relayed by the fiber bundle is mixed with the reference field and made to coincide with the input slit of an imaging spectrograph. The data collected are processed in real time, producing a depth-resolved angular scattering distribution in 0.37 s. The data are used to determine the sizes of polystyrene microspheres with subwavelength precision and accuracy.

Endoscopes↗
PubMed1995

Interferometry: a new method for no-touch measurement of the surface and volume of ulcerous skin lesions.

A new interferometry procedure (Holon View measuring system) permits non-invasive and objective measurement of the surface, height/depth and volume of ulcerous lesions. The method, which uses a combination of the so-called phase-shift and gray-code technique, is new in dermatology. The measuring system consists of a diffraction grating projection system, a video camera and a computer-aided, digital image processing and analysis system. A diffraction grating consisting of 320 lines is projected onto the skin surface or a silicone impression of the ulcerous lesion. The course of the light-intersection lines is recorded by a video camera and read into an image computer. The special feature of the method is the combination of grey-code projection and a phase-shift procedure. For evaluation of the method in dermatology, 2,000 interferometric measurements of volume were carried out on objects of known volume, on silicone impressions and on leg ulcers. The accuracy of the method has been proven by means of the evaluation of objects of known volume. The results of interferometric measurements were compared with the values of the volume determined by water capacity and those of the surface determined by image analysis. The healing of a leg ulcer was followed over an 8-week period. The Holon View measuring system permits no-touch measurement of the volume and surface of ulcerous skin lesions with a high degree of accuracy and precision, in a short time.

Body Water↗
PubMed1980

Holographic interferometry applied to the study of the human skull.

A laboratory technique that allows strain measurements of the skull is described. Holographic interferometry allows the entire surface displacement of the skull to be mapped within 1/10 of the wavelength of light. Holographic interferometric pictures are presented following various stress applications to the skull. The method, besides being exquisitely sensitive, allows strain measurements simultaneously in any desired direction over the entire skull. No physical contact with the skull is required, and the experimental set-up is simple.

Holography↗
PubMed1991

Assessment of red blood cell aggregation with dextran by ultrasonic interferometry.

Aggregation of human red blood cells (RBCs) induced by dextrans of various molecular weight has been studied by using a new ultrasonic interferometry method. This method, based on A-mode echography, allowed for the measurement of the accumulation rate of particles on a solid plate which is related to their sedimentation rate (i.e., to their mean size). The initial aggregation process, the mean and the maximum sedimentation rate of aggregates and the packing of the sedimented RBCs have been investigated. Effects of hematocrit, molecular weight of dextrans and inhibition by dextran 40 on the RBC aggregation induced by dextran of higher molecular weight have been determined by analysing variations of the aggregate size. Results obtained confirm the aggregation effect of dextrans of molecular weights equal or higher than 70,000 dalton and disaggregation effect of dextran 40,000 dalton on aggregation by dextrans of higher molecular weight.

Dextrans↗
PubMed1990

[Influence of liquid volume in the middle ear on tympanic membrane vibration (experimental study by holographic interferometry)].

The influence of middle ear liquid on the tympanic membrane (TM) vibration was studied using the holographic interferometry. The physiological saline solution was injected into the middle ear cavity of the canine temporal bone. The liquid volume in the middle ear cavity was changed into 3 grades in order to observe the difference of the vibration pattern between them. The vibratory patterns of a normal canine TM remained unchanged in their first mode up to a frequency of approximately 2 kHz. In this mode, there were peak displacement regions in the posterior and anterior quadrants. The TM vibrations showed sectional patterns, above 3 kHz in the posterior and above 4 kHz in the anterior. After liquid retention, the following were observed. 1. The frequency at which sectional patterns occurred shifted to a lower frequency in the immerged portion, but showed no definite tendency in the unimmerged portion. 2. Maximum amplitudes of the anterior and posterior quadrants of the TM and the mallar tip shifted to somewhat higher frequencies for the liquid volume below the level of the tip portion, but contrary, shifted to lower frequencies for the liquid volume there above. 3. The ossicular chain tended not to make normal function for the TM vibration with an increase of liquid volume.

Animals↗
PubMed1990

[Effects of an increase or decrease in the middle ear pressure on tympanic membrane vibrations (experimental study by holographic interferometry)].

The effects of positive and negative pressure in the middle ear on tympanic membrane (TM) vibrations were studied in twenty canine temporal bones by holographic interferometry. The displacement of the TM was measured by moiré topography. 1) When pressure was applied to the tympanic cavity, the curvature of the TM became small under negative pressure and large under positive pressure, with the displacement being greater under positive pressure. 2) Without pressure load, the vibration pattern below 2 kHz was simple and there were peak displacement regions in the posterior and anterior parts of the membrane and the peaks occurred approximately halfway along the manubrium. The TM vibrations showed sectional patterns, above 3 kHz in the posterior and above 4 kHz in the anterior. The amplitude of the anterior peak was larger than that of the mallear tip, but smaller than that of the posterior. 3) At frequencies below 2 kHz, the vibration pattern was not affected by negative pressure load. At frequencies of 3 kHz or higher, the sectional patterns changed into the simpler patterns and the sectional vibrations diminished as the pressure increased. 4) Below 2 kHz, the TM amplitude decreased with increasing negative pressure. Above 3 kH, the amplitude showed an initial increase but decreased at higher negative pressure loading. With the amplitude of the mallear tip, the same tendency was observed. The resonance frequency shifted to a higher frequency range with pressure loading. 5) Under positive pressure, the vibration pattern remained unchanged below 2 kHz, and above 3 kH, sectional vibrations changed to the simple vibrations.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

[Effects of the perforation of the tympanic membrane on its vibration--with special reference to an experimental study by holographic interferometry].

Using canine temporal bone, perforations were surgically prepared at the anterior, inferior and posterior parts of the tympanic membrane, and the influences of these perforations on the tympanic vibration were observed and analyzed by holographic interferometry. Normal canine tympanic membrane had its respective single maximum amplitude points at its anterior and posterior parts at a frequency from the low compass to 2 kHz or so and showed a concentric circular vibration pattern centering mainly there around. At 3 and 4 kHz or so, the posterior and anterior parts began to show their respective sectional vibrations and with an increase in frequency, showed their further complicated multi-sectional vibrations. Resonance frequency was 1 or 2 kHz or so. The tympanic vibration following the preparation of perforations was as follows: 1) For the posterior perforation, the frequency at which the anterior sectional vibration began passed to a higher frequency, while for the other perforations, no change was noted in vibration pattern of the remaining tympanic membrane. 2) Comparative examination of the vibration amplitude at the mallear tip revealed that for a small perforation, no change in resonance frequency was noted regardless of the location of perforation and an increase in vibration amplitude was noted near the resonance frequency. 3) For the anterior perforation, no change in resonance frequency was noted even with an expansion of perforation and an increase in vibration amplitude was noted near the resonance frequency. 4) For the posterior and inferior perforations, the resonance frequency passed to a higher frequency with an expansion of perforation and an increase in vibration amplitude was noted near the resonance frequency.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2000

Fine structure of parvocellular receptive fields in the primate fovea revealed by laser interferometry.

Optical blurring in the eye prevents conventional physiological techniques from revealing the fine structure of the small parvocellular receptive fields in the primate fovea in vivo. We explored the organization of receptive fields in macaque parvocellular lateral geniculate nucleus cells by using sinusoidal interference fringes formed directly on the retina to measure spatial frequency tuning at different orientations. Most parvocellular cells in and near the fovea respond reliably to spatial frequencies up to and beyond 100 cycles/ degrees of visual angle, implying center input arising mainly from a single cone. Temporal frequency and contrast response characteristics were also measured at spatial frequencies up to 130 cycles/degrees. We compared our spatial frequency data with the frequency responses of model receptive fields that estimate the number, configuration, and weights of cones that feed the center and surround. On the basis of these comparisons, we infer possible underlying circuits. Most cells had irregular spatial frequency-response curves that imply center input from more than one cone. The measured responses are consistent with a single cone center together with weak input from nearby cones. By exposing a fine structure that cannot be discerned by conventional techniques, interferometry allows functional measurements of the early neural mechanisms in spatial vision.

Animals↗
PubMed2000

Nuclear medicine image registration by spatially noncoherent interferometry.

UNLABELLED: This article introduces a technique for obtaining high-resolution body contour data in the same coordinate frame as that of a rotating gamma camera, using a miniature range finder, the conoscope, mounted on the camera gantry. One potential application of the technique is accurate coregistration in longitudinal brain SPECT studies, using the face of the patient (or "mask"), instead of SPECT slices, to coregister subsequent acquisitions involving the brain. METHODS: Conoscopic holography is an interferometry technique that relies on spatially incoherent light interference in birefringent crystals. In this study, the conoscope was used to measure the absolute distance (Z) between a light source reflected from the skin and its observation plane. This light was emitted by a 0.2-mW laser diode. A scanning system was used to image the face during SPECT acquisition. The system consisted of a motor-driven mirror (Y axis) and the gamma-camera gantry (1 profile was obtained for each rotation step, X axis). The system was calibrated to place the conoscopic measurements and SPECT slices in the same coordinate frame. RESULTS: Through a simple and robust calibration of the system, the SE for measurements performed on geometric shapes was less than 2 mm, i.e., less than the actual pixel size of the SPECT data. Biometric measurements of an anthropomorphic brain phantom were within 3%-5% of actual values. The mask data were used to register images of a brain phantom and of a volunteer's brain, respectively. The rigid transformation that allowed the merging of masks by visual inspection was applied to the 2 sets of SPECT slices to perform the fusion of the data. CONCLUSION: At the cost of an additional low-cost setup integrated into the gamma-camera gantry, real-time data about the surface of the head were obtained. As in all other surface-based techniques (as opposed to volume-based techniques), this method allows the match of data independently from the dataset of interest and facilitates further registration of data from any other source. The main advantage of this technique compared with other optically based methods is the robustness of the calibration procedure and the compactness of the sensor as a result of the colinearity of the projected beam and the reflected (diffused) beams of the conoscope. Taking into account the experimental nature of this preliminary work, significant improvements in the accuracy and speed of measurements (up to 1000 points/s) are expected.

Brain↗
PubMed2000

Interferometry in the assessment of biomechanical features of the masticatory system hard segments.

Biomechanical studies have found wide application and solved many problems in dental medicine. An interdisciplinary approach has allowed an ever-faster progress in the field. The aim of this study was to point out the advantages of holographic interferometry. With the use of this method, the study object is observed as a whole rather than as a substrate, thus providing a three-dimensional holographic image visualizing the load transmission from one jaw to another, tooth pressure against the alveolus, and strain of Sharpey's fibers, and yielding precise data on deformities, dislocations and force distribution.

Anthropometry↗
PubMed2000

[Laser doppler interferometry, a new clinical instrument?].

INTRODUCTION: In a prospective trial, the diagnostic value of laser Doppler interferometry (LDI) was analysed in the clinical sphere. METHOD: LDI was compared with standard audiometry for preoperative differential diagnosis of a conductive hearing loss. The intraoperative diagnosis was considered the gold standard. RESULTS: LDI was applicable in the clinical sphere and allowed, in contrast to standard audiological methods, a statistically highly significant differentiation of middle ear pathologies. CONCLUSION: LDI is a valuable addition to standard audiology for preoperative evaluation of the integrity and mobility of the ossicular chain.

Audiometry↗
PubMed2002

Sensitivity of the ultrasonic interferometry method (Echo-Cell) to changes of red cell aggregation: application to diabetes.

The sensitivity of the ultrasonic interferometry method (Echo-Cell) to changes in red blood cell (RBC) aggregation was investigated in comparison to the Regulest erythroaggregometry known as a reference method. In experiments where different concentrations of dextrans of 40 or 70 kD molecular weights were added to normal RBCs, the Echo-Cell was proved as sensitive as erythroaggregometry. A comparative study using RBC samples from normal and diabetic subjects showed that the Echo-Cell was much more sensitive when aggregation was measured in diluted than undiluted plasma. The sensitivity of Echo-Cell measurements in diluted plasma was similar to that of erythroaggregometry. Further analysis revealed that RBC aggregation was underestimated by Echo-Cell when measurements were made in undiluted plasma containing high fibrinogen levels, implying that in that case an elevated plasma viscosity might indirectly affect the sensitivity of the Echo-Cell. The low sensitivity of the Echo-Cell to detect an abnormal RBC aggregation when suspensions were prepared in undiluted plasma, is likely related to a relatively high shear stress exerted on RBC aggregates by the suspending medium. In conclusion, the sensitivity of the Echo-Cell to detect abnormal changes in RBC aggregation can be optimized by diluting the plasma.

Adult↗
PubMedDate not supplied

[Slow photoinduced changes in reaction centers of Rhodobacter sphaeroides R-26 by holographic interferometry].

Using the on-line holographic interferometry, changes in the refraction index of illuminated solutions containing the Rhodobacter sphaeroides R-26 reaction centers isolated from membranes by detergents of ionic and nonionic nature were registered. Factors affecting the refraction index of these solutions were analyzed. It was shown that the photoinduced changes in this parameter are due to structural changes in the molecular complex of reaction centers. The results of measurements of the kinetics of absorption spectra at lambda = 865 nm for two detergent types are presented, which coincide qualitatively with the results of holographic measurements. The change in the volume of the molecular complex of reaction centers was estimated to be 0.1 divided by 1%.

Holography↗
PubMed2003

In situ detection of neoplastic transformation and chemopreventive effects in rat esophagus epithelium using angle-resolved low-coherence interferometry.

We present a quantitative study of the nuclear morphometry of epithelial cells in an animal model of esophageal carcinogenesis. Changes in the size and texture of cell nuclei as a result of neoplastic transformation and chemopreventive action are observed in situ using a new optical technique, angle-resolved low-coherence interferometry (a/LCI). The capabilities of a/LCI are demonstrated via quantitative in situ measurements of the nuclear morphometry of basal epithelial cells, approximately 50-100 microm beneath the tissue surface without the need for exogenous contrast agents or tissue fixation. The measurements quantify changes in nuclear size, characterized by average diameter, and nuclear texture, characterized by fractal dimension of the subcellular structures. Using this technique, we observed changes in the morphometry of rat esophageal epithelial cells in response to treatment with the carcinogen N-nitrosomethylbenzylamine. In addition, morphometric changes were observed in the esophagi of rats treated with N-nitrosomethylbenzylamine and two chemopreventive agents, difluoromethylornithine and perillyl alcohol. These agents induced either apoptosis in the basal epithelium (difluoromethylornithine) or both apoptosis and vacuolation of basal epithelial cells (perillyl alcohol). Vacuolation was associated with cellular toxicity. The light-scattering measurements were compared with histological images of the same tissues. The potential of a/LCI as a noninvasive means to investigate the development of epithelial neoplasia and for tracking the efficacy of chemopreventive agents appears high. This technique also may provide a new screening tool for intraepithelial neoplasia.

Animals↗
PubMed1992

Measurement of corneal thickness by laser Doppler interferometry.

The laser Doppler interferometry (LDI) technique, which was recently developed for axial eye length measurement, has been modified to measure the corneal thickness of the human eye in vivo. High accuracy is achieved. The standard deviation of the technique is about 7 microns, and improvement by a factor of 5 is possible. First comparisons with a usual slit lamp pachometer show a general agreement but a systematic difference of about 20 microns. Possible reasons for this discrepancy are discussed. Finally, the new method is compared to standard optical and ultrasound pachometry from a theoretical point of view, and advantages and drawbacks of the various techniques are discussed.

Cornea↗
PubMed1989

[The study of holographic interferometry of the maxilla].

The method which combines the removable appliance with a headgear attached to the maxillary dentition is widely used in treatment of the maxillary protrusion of growing children. The initial reaction of maxillary complex caused by the removable appliance retraction was studied by the holographic interferometry. In this paper, the results indicate that when the pull applied along the occlusal plane the maxilla was moved downward, whereas when the pall applied along the occlusal plane at 15 the maxilla was moved upward and backward. The advantage of this method and model of the experimentation was discussed in the paper.

Biomechanical Phenomena↗
PubMedDate not supplied

[Clinical applications and critical evaluation of helium-neon laser interferometry].

Exploration of macular function in patients opaque media has been performed routinely with Helium-Neon Laser interferometry for more than 5 years. Our results in patients with cataract, macular diseases, retinal detachment and functional amblyopia are reported. Accurate correlations, overestimations and underestimations are differentiated with special emphasis on overestimations.

Amblyopia↗