SEARCH · PubMed Health

Results for “INTERFEROMETRY”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 37 records · Page 2Linked to original sources

PubMed1995

[Experimental deformation in a bone fixation plate: measurement using holographic interferometry].

The minute mechanical properties of the tibia fixed by a metal plate and screws were investigated under various simulated loading conditions. The bracing technique and the design of the osteosynthetic plate are discussed based on the measurement results. The specimens were eight dried human tibias. Four different fixation method were employed using an AO plate system, and also using an Eggers plate system. The bending force, torsion force and axial force were applied to the tibia. Deformation in the tibia and/or metal plate was measured using double exposure holographic interferometry. The mechanical properties were estimated from the fringe pattern and from the deformation curve obtained from the reconstruction image of the holographic interferometry. The fixation capability of the plate systems differed according to the direction of the loading. The reconstruction image of the hologram showed that deformation increased mainly in the plate corresponding to the fracture line of the tibia. Screws nearer the fracture line were more important in increasing the fixation capability of the plate. Twisted deformations in the plate were observed under a simple bending force. The new measurement method of holographic interferometry clearly showed the two dimensional bending and the twisted deformation in detail.

Biomechanical Phenomena↗

PubMed1997

[Laser interferometry in preoperative evaluation of visual acuity in children].

PURPOSE: To study the possibility of using laser interferometry in prediction of visual acuity in children after cataract surgery. Until now this method has been used only in adults. In the literature no papers were found about prediction of visual acuity in children. MATERIAL AND METHODS: Laser interferometry was performed before surgery in 27 eyes of children aged 6-15 and the results were compared with visual acuity after cataract extraction with IOL implantation. RESULTS: Laser interferometry is of limited value in pediatric patients.

Adolescent↗

PubMed1984

Use of microscopic interferometry for measuring changes in water content of small samples of tissue.

Oedema following periods of ischaemic arrest and subsequent reperfusion has been shown experimentally and clinically to affect the functional state of the heart. Tissue water content has been measured in myocardial sections by microscopic interferometry and densitometry, and the results correlated with those obtained by wet and dry weight analysis (r = 0.87; p less than 0.001). Microscopic interferometry also revealed the distribution of the water in the tissue. Experimentally induced ischaemic arrest in isolated rat hearts resulted in predominantly intra-fibrillar oedema, whilst subsequent reperfusion resulted in interfibrillar oedema. Microscopic interferometry facilitates accurate measurement of water content in tissue samples as small as 2 mg wet weight and shows (as conventional wet/dry weight analysis cannot) the distribution of the water in the tissue.

Animals↗

PubMed2003

Mapping of tooth deformation caused by moisture change using moiré interferometry.

UNLABELLED: Bonding of composite restorative materials to teeth usually involves surface etching and drying of both dentin and enamel. These two hard tissues have very different water contents. OBJECTIVES: The purpose of this study was to evaluate the effects of changes in humidity on the dimensional changes in dentin disks constrained by enamel and in unconstrained dentin. METHODS: Changes in humidity were used to induce changes in the moisture level of the hard tissues, which created a mechanical load across the dentin-enamel junction (DEJ). High-sensitivity moiré interferometry was used to measure the magnitudes of the strains. Diffraction gratings (with a sensitivity of 2400 lines/mm) were transferred to moist polished sections of human teeth, which were subsequently dehydrated and then hydrated again. The fringe patterns from moiré interferometry recorded the change in deformation between the moisture states. RESULTS: The results indicated that there were wide variations in strain between the two specimen geometries. The strains were fairly constant through the bulk of the dentin in both specimen types. However, the strain gradients were very high across the dentin-enamel interface into the dentin in the unconstrained geometry, and nearly zero in the constrained geometry. SIGNIFICANCE: Moiré interferometry is a powerful tool to study the deformation of materials that are not isotropic and are not linearly elastic. It provides full-field, high-resolution deformation fields in tooth specimens. Deformations observed in this study indicate that the DEJ zone is a unique material interface that needs to be better understood in terms of normal tooth function, and that its material properties be taken into account when natural hard tissues are restored.

Algorithms↗

PubMed2002

Coda wave interferometry and the equilibration of energy in elastic media.

Multiple-scattered waves usually are not useful for creating deterministic images of the interior of elastic media. However, in many applications, one is not so much interested in making a deterministic image as in detecting changes in the medium. Cases in point are volcano monitoring and measuring the change in hydrocarbon reservoirs during enhanced recovery operations. Coda wave interferometry is a technique wherein changes in multiple-scattered waves are used as a diagnostic for minute changes in the medium. This technique was developed previously for scalar waves; however, the application of this technique in geophysics, nondestructive testing, and other applications where elastic waves are used, requires the extension of the existing formulation of coda wave interferometry to include conversions between P and S waves. Here, a simple model for the equilibration between P and S waves incorporates into the theory of coda wave interferometry the mode conversions that are inherent to multiply scattered elastic waves.

Journal Article↗

PubMed2000

Limitations of interferometry due to the flicker noise of laser diodes

Interferometry with laser diodes is a cost-effective way to perform displacement measurement. The tunability of laser diodes is also of great interest in multiple-wavelength interferometry. However, the additional flicker noise in the frequency-noise spectrum of semiconductor lasers may become a limiting factor. Investigations on the limitations due to the 1/f noise of laser diodes are presented for both classical and multiple-wavelength interferometry. Measurements at the limit of the coherence length of laser diodes with the corresponding phase fluctuations are reported. The theoretical results are verified experimentally.

Journal Article↗

PubMed1999

Evaluation of orbital stress dissipation in pediatric and adult skulls using electronic speckle pattern interferometry.

OBJECTIVES: To measure and quantitatively compare the degree of force dissipation in pediatric and adult skulls subjected to similar dynamic forces. DESIGN: An anatomical study using electronic speckle pattern interferometry, which allows generation of displacement vectors after application of a force. SUBJECTS: Five human skulls (3 pediatric and 2 adult). INTERVENTION: Each skull was subjected to a reproducible and quantifiable force created by a steel ball pendulum striking a precise periorbital focus: (1) infraorbital foramen, (2) supraorbital notch, (3) malar eminence, and (4) nasofrontal suture. Electronic speckle pattern interferometry was used to construct interferogram fringe patterns to determine skull regions with the greatest degree of displacement. RESULTS: Interferogram analysis revealed that the adult skull has a tendency to dissipate force with minimal resultant displacement. In contrast, the pediatric skulls demonstrated greater displacements (ie, increased fringe density) at the same periorbital foci. CONCLUSIONS: The pediatric skull dissipates periorbital stress differently than the adult skull, as illustrated by quantitative interferogram analysis. This finding parallels clinical data that demonstrate a varying pattern of fractures in pediatric and adult skulls related to craniofacial development.

Adult↗

PubMed2000

Use of holographic laser interferometry to study the diffusion of polymers in gels.

The aim of this study was to demonstrate the potential for holographic interferometry to be used for diffusion studies of large molecules in gels. The diffusion and partitioning of BSA (67,000 g/mol) and pullulans (5,900-112,000 g/mol) in agarose gel were investigated. The gel diffusion coefficients obtained for BSA were higher when distilled water was used as a solvent compared to those obtained with 0.1 M NaCl as the solvent. Furthermore, the gel diffusion coefficient increased with increasing BSA concentration. The same trend was found for liquid BSA diffusion coefficients obtained by DLS. BSA partition coefficients obtained at different agarose gel concentrations (2-6%, w/w) decreased slightly with increasing gel concentration. However, all BSA gel diffusion coefficients measured were significantly lower than those in pure solvent and they decreased with increasing agarose concentration. The gel diffusion coefficients obtained for pullulans decreased with increasing pullulan molecular weight. The same effect from increased molecular weight was seen in the liquid diffusion coefficients measured by DLS. The pullulan partition coefficients obtained decreased with increasing molecular weight. However, pullulans with a larger Stokes' radius than BSA had partition coefficients that were higher or approximately the same as BSA. This implied that the pullulan molecules were more flexible than the BSA molecules. The results obtained for BSA in this study agreed well with other experimental studies. In addition, the magnitude of the relative standard deviation was acceptable and in the same range as for many other methods. The results thereby obtained showed that holographic interferometry is a suitable method for studying diffusion of macromolecules in gels.

Diffusion↗

PubMed2002

Interferometry in flow to sort unstained X- and Y-chromosome-bearing bull spermatozoa.

BACKGROUND: It was found earlier that the difference in volume between unstained X- and Y-chromosome-bearing sperm heads could be detected using interference microscopy in visible light. This could be the basis for an alternative to the conventional method to sort X and Y sperm, which uses DNA staining and ultraviolet (UV)-excitation that may be harmful to sperm cells. A novel technique is introduced combining interferometry with flow cytometry. MATERIALS AND METHODS: Interference optics were built into an existing flow cytometer/cell sorter and used to sort fresh unstained bull sperm cells on the basis of their head volume. Sorted fractions were stained with a DNA stain, and reanalyzed using the conventional method. RESULTS: Purities between 60-66% were found in both X- and Y-enriched fractions. It was possible to sort up to 300 cells per second. The system was found to be less sensitive to the orientation of sperm cells than the conventional method. CONCLUSIONS: Interferometry can be combined with flow cytometry and used to obtain significantly enriched fractions of X- and Y-bearing sperm without staining and UV light. Sorting speeds and purities at this point, however, are much lower than with the conventional method.

Animals↗

PubMed2000

Comparison of immersion ultrasound biometry and partial coherence interferometry for intraocular lens calculation according to Haigis.

BACKGROUND: The precision of intraocular lens (IOL) calculation is essentially determined by the accuracy of the measurement of axial length. In addition to classical ultrasound biometry, partial coherence interferometry serves as a new optical method for axial length determination. A functional prototype from Carl Zeiss Jena implementing this principle was compared with immersion ultrasound biometry in our laboratory. PATIENTS AND METHODS: In 108 patients attending the biometry laboratory for planning of cataract surgery, axial lengths were additionally measured optically. Whereas surgical decisions were based on ultrasound data, we used postoperative refraction measurements to calculate retrospectively what results would have been obtained if optical axial length data had been used for IOL calculation. For the translation of optical to geometrical lengths, five different conversion formulas were used, among them the relation which is built into the Zeiss IOL-Master. IOL calculation was carried out according to Haigis with and without optimization of constants. RESULTS: On the basis of ultrasound immersion data from our Grieshaber Biometric System (GBS), postoperative refraction after implantation of a Rayner IOL type 755 U was predicted correctly within +/- 1 D in 85.7% and within +/- 2 D in 99% of all cases. An analogous result was achieved with optical axial length data after suitable transformation of optical path lengths into geometrical distances. CONCLUSIONS: Partial coherence interferometry is a noncontact, user- and patient-friendly method for axial length determination and IOL planning with an accuracy comparable to that of high-precision immersion ultrasound.

Adult↗

PubMed1994

Characterization of biomembranes by spectral ellipsometry, surface plasmon resonance and interferometry with regard to biosensor application.

Phospholipid bilayers with transport proteins and antigen/antibody interfaces are considered to be suitable biosensor systems. The quality of such membranes or interfaces depends on the properties of the layers. Optical methods have proved to be an appropriate tool for characterizing those layers in situ and in a non-destructive manner. Two systems with potential for biosensor applications are characterized by some of these methods: phospholipid bilayer membranes spread from vesicle solution and protein-antigens both adsorbed on planar solid support. The results of spectral ellipsometry, surface plasmon resonance (SPR) and spectral interferometry are compared with respect to quality of characterization, expenditure of sample preparation and measurement, and time resolution. The phospholipid membranes adsorbed show a relatively low refractive index and a relatively high thickness. Bruggeman effective medium approximation is used to calculate the effective layer thickness. This result is compared to SPR measurements. A correlation between thickness and vesicle concentration may be detected. Further, the test protocol of an immunoassay is examined by spectral interferometry and SPR. Thicknesses determined are compared to results obtained by applying spectral ellipsometry. The data measured by ellipsometry are in agreement with the molecular dimensions of the immunoglobulins. Differences between details can be explained by physical considerations.

Biosensing Techniques↗

PubMed2004

Central corneal thickness measurements with partial coherence interferometry, ultrasound, and the Orbscan system.

OBJECTIVE: To compare the reliability of central corneal thickness measurements (CCT) obtained with partial coherence interferometry (PCI), ultrasound pachymetry, and the Orbscan system. DESIGN: Cross-sectional study. PARTICIPANTS: Twenty healthy subjects with CCT measurements in both eyes. METHODS: The CCT measurements were obtained with PCI, ultrasound pachymetry, and the Orbscan system. In each eye, 2 investigators performed 5 repeated measurements with each pachymetric device. Intraclass correlation coefficients (kappa) were calculated and mean CCT measurements were compared. MAIN OUTCOME MEASURES: The CCT measurements obtained with ultrasound pachymetry, the Orbscan system (Orbtek Inc., Salt Lake City, UT), and PCI. RESULTS: Mean CCT values measured with ultrasound pachymetry were significantly thicker than those measured with PCI (21.5 microm; P<0.001) or the Orbscan system (19.8 microm; P<0.001). The correlation coefficients for the intraobserver variability were 0.999 for PCI measurements, 0.983 for ultrasound pachymetry measurements, and 0.988 for Orbscan system measurements. The correlation coefficients for the interobserver variability were 0.998 for PCI measurements, 0.980 for ultrasound pachymetry measurements, and 0.988 for Orbscan system measurements. There was a slightly better consistency between ultrasound pachymetry and PCI (kappa = 0.96) than between the Orbscan system and PCI (kappa = 0.92) and between ultrasound pachymetry and the Orbscan system (kappa = 0.89). CONCLUSIONS: Partial coherence interferometry was the method with the least intraobserver or interobserver variability. Mean CCT as measured with ultrasound pachymetry was approximately 20 microm thicker than with the Orbscan system and PCI. However, corneal thickness measurements with ultrasound pachymetry and PCI were slightly more consistent than those of the Orbscan system and PCI. This slightly better consistency, however, may be important, especially in corneal refractive surgery.

Adult↗

PubMed2005

Holographic interferometry of cerebral pulsations.

BACKGROUND: Holographic interferometry is a noninvasive method used to analyze the mechanical displacement affecting an object undergoing deformation. This technique has been primarily applied to inanimate entities owing to the difficulty in producing stress forces in living subjects. In this report, the possibility of harnessing cerebral pulsations as a displacement force to produce interferograms in neurosurgical patients was studied. METHODS: This work evaluates the application of this technology to patients with areas of calvarial defects. Using a pulse ruby laser, holographic interferograms were created in neurosurgical patients with areas of calvarial loss. The cardiac cycle was used to trigger the firing of the laser. RESULTS: The holographic interferograms were accurate up to within 0.5 mm in outlining the region of bony deficiency. CONCLUSION: Holographic interferometry imaging was successfully accomplished using cerebral pulsations as a cyclic displacement-producing force. This method accurately outlined the area of bony loss. A discussion of this technology is included.

Adult↗

PubMed2001

Improved prediction of intraocular lens power using partial coherence interferometry.

PURPOSE: To evaluate the feasibility of using a new optical biometry technique, dual-beam partial coherence interferometry (PCI), to improve intraocular lens (IOL) power prediction in cataract surgery. SETTING: Department of Ophthalmology, Vienna General Hospital, and Institute of Medical Physics, University of Vienna, Vienna, Austria. METHODS: Preoperative axial length (AL) data obtained with PCI biometry and applanation ultrasound (US) biometry in 77 eyes of 51 patients was applied to 4 commonly used IOL power formulas. The refractive outcome and the mean absolute error (MAE) were calculated for each formula using both biometry methods. A linear multiple-regression model based on preoperative PCI biometry data was derived to predict the postoperative anterior chamber depth (ACD). The predictive power of this regression model was assessed by adding the predicted ACD to the SRK/T formula. Predicted residuals were calculated to evaluate the feasibility and stability of this modified IOL power formula. RESULTS: Using PCI instead of US biometry significantly improved the refractive outcome with all 4 IOL power formulas. The Holladay I and SRK/T formulas yielded an MAE of 0.44 diopter (D) using PCI AL data and 0.56 D and 0.57 D, respectively, using US biometry data. The SRK/T formula combined with the PCI regression model for postoperative ACD prediction performed slightly better (MAE 0.42 D) than the conventional SRK/T formula alone. Predicted residuals revealed an MAE of 0.46 D, proving the predictive performance of the new formula. CONCLUSIONS: Partial coherence interferometry biometry applied to several widely used IOL power formulas yielded significantly better IOL power prediction and therefore refractive outcome in cataract surgery than US biometry. Further improvement can be achieved by applying PCI to a modified SRK/T formula that predicts the postoperative ACD using PCI biometry data.

Biometry↗

PubMed2002

Accuracy and reproducibility of biometry using partial coherence interferometry.

PURPOSE: To determine whether partial coherence interferometry is comparable to standard contact ultrasonic biometry in accuracy, reproducibility, and ease of use. SETTING: Academic university practice. METHODS: In this prospective study, simultaneous biometry was performed in 91 consecutive patients (111 eyes) using partial coherence interferometry (IOLMaster, Zeiss Humphrey Systems) and ultrasonic biometry (I(3), Innovative Imaging, Inc.). The differences between the predicted spherical equivalent in diopters (D) and the actual results with both techniques were compared. RESULTS: The IOLMaster was significantly better in the mean absolute error (0.533 D +/- 0.589 [SD] versus 0.757 +/- 0.723 D; P = .012) and the percentage of eyes within +/-0.5 D (61.2% versus 42.3%; P = .003) and +/-1.0 D (87.4% versus 77.5%; P =.05) of the predicted refraction. CONCLUSION: The IOLMaster was more accurate and reproducible than the contact ultrasonographic technique.

Biometry↗

PubMed2002

Immersion A-scan compared with partial coherence interferometry: outcomes analysis.

PURPOSE: To compare 2 methods of axial length measurement, immersion ultrasonography and partial coherence interferometry, and to elucidate surgical outcomes based on immersion measurements. SETTING: Oregon Eye Institute, Eugene, Oregon, USA. METHODS: Axial length measurements in 50 cataractous eyes were obtained by optical biometry (IOLMaster, Zeiss Humphrey Systems) and immersion ultrasound (Axis II, Quantel Medical), and the results were compared. Intraocular lens (IOL) power calculations in the same eyes after cataract extraction and posterior chamber IOL implantation were evaluated retrospectively based on the postoperative spherical equivalent prediction error. RESULTS: Immersion ultrasonography and partial coherence interferometry measurements correlated in a highly positive manner (correlation coefficient = 0.996). Outcomes analysis demonstrated 92.0% of eyes were within +/-0.5 diopter of emmetropia based on immersion axial length measurements. CONCLUSION: Immersion ultrasonography provided highly accurate axial length measurements and permitted highly accurate IOL power calculations.

Biometry↗

PubMed2002

Biometry of cataractous eyes using partial coherence interferometry: clinical feasibility study of a commercial prototype I.

PURPOSE: To evaluate the clinical feasibility of the prototype version of a commercial partial coherence interferometry instrument (axial length measurement, ALM, Carl Zeiss Jena) for noninvasive, high-precision biometry in cataractous eyes. SETTING: Department of Ophthalmology, Vienna General Hospital, and Institute of Medical Physics, University of Vienna, Austria. METHODS: The preoperative axial length in 49 eyes of 37 cataract patients was measured with the commercial (ALM) and laboratory (PCI) prototypes of the partial coherence interferometry instrument, as well as with immersion ultrasound (IUS). RESULTS: Axial length measurements with the ALM and PCI did not differ significantly (P = .23). Both prototypes assessed longer axial lengths than the IUS technique (P < .0001; median 203 microm; range -476 to +635 microm). The precision of the axial length measurement was 18 microm, 28 microm, and 54 microm with the PCI, ALM, and IUS, respectively. CONCLUSIONS: Partial coherence tomography is a high-precision, high-resolution, noncontact biometric technique.The commercial PCI prototype is practical in clinical use, with improved comfort for patients, no need for anesthesia, and a reduced risk of infection. However, the difference between the PCI and IUS in axial length measurement must be considered when using the constants supplied by intraocular lens (IOL) manufacturers for IOL power calculations.

Adult↗

PubMed2002

Comparison of ultrasound pachymetry and partial coherence interferometry in the measurement of central corneal thickness.

PURPOSE: To compare central corneal thickness (CCT) measurements obtained with 3 ultrasound pachymeters and with partial coherence interferometry (PCI) and evaluate the effect of repeated contact by a pachymetry probe on corneal thickness. SETTING: Department of Ophthalmology, University of Vienna, Vienna, Austria. METHODS: Central corneal thickness was measured in 20 eyes of 20 healthy volunteers with 3 different ultrasound pachymeters (DGH 500, DGH Technology Inc.; SP 2000, Tomey Inc.; Paxis, Biovision Inc.) and with PCI. In each eye, 5 measurements with PCI were followed by 5 measurements with each ultrasound pachymetry device and another 5 measurements with PCI. RESULTS: The mean CCT measured with the DGH 500, SP 2000, and Paxis was 541.0 microm, 539.2 microm, and 545.1 microm, respectively. Although the differences among the 3 ultrasound pachymetry devices were within 6.0 microm, they were statistically significant (P<.05). The PCI measurements were significantly smaller (P <.05) than the ultrasound measurements: 518.8 microm before and 517.5 microm after repeated contact with the ultrasound pachymetry probe (P <.05). The mean precision (standard deviation) was 0.77 microm for PCI and between 2.40 microm and 3.58 microm for ultrasound pachymetry measurements. The correlation coefficients for the intraobserver variability were 0.999 for PCI and between 0.987 and 0.995 for ultrasound pachymetry measurements. CONCLUSIONS: Partial coherence interferometry was the more precise method of measuring CCT and had better intraobserver variability. Repeated contact by a pachymetry probe reduced corneal thickness by 1.3 microm. However, the reason for the smaller measurements with PCI than with ultrasound pachymetry remains unclear.

Adult↗