Reproducibility of Results: The statistical reproducibility of measurements (often in a clinical context), including the testing of instrumentation or techniques to obtain reproducible results. The concept includes reproducibility of physiological measurements, which may be used to develop rules to assess probability or prognosis, or response to a stimulus; reproducibility of occurrence of a condition; and reproducibility of experimental results.Observer Variation: The failure by the observer to measure or identify a phenomenon accurately, which results in an error. Sources for this may be due to the observer's missing an abnormality, or to faulty technique resulting in incorrect test measurement, or to misinterpretation of the data. Two varieties are inter-observer variation (the amount observers vary from one another when reporting on the same material) and intra-observer variation (the amount one observer varies between observations when reporting more than once on the same material).Sensitivity and Specificity: Binary classification measures to assess test results. Sensitivity or recall rate is the proportion of true positives. Specificity is the probability of correctly determining the absence of a condition. (From Last, Dictionary of Epidemiology, 2d ed)Image Processing, Computer-Assisted: A technique of inputting two-dimensional images into a computer and then enhancing or analyzing the imagery into a form that is more useful to the human observer.Reference Standards: A basis of value established for the measure of quantity, weight, extent or quality, e.g. weight standards, standard solutions, methods, techniques, and procedures used in diagnosis and therapy.Imaging, Three-Dimensional: The process of generating three-dimensional images by electronic, photographic, or other methods. For example, three-dimensional images can be generated by assembling multiple tomographic images with the aid of a computer, while photographic 3-D images (HOLOGRAPHY) can be made by exposing film to the interference pattern created when two laser light sources shine on an object.Quality Control: A system for verifying and maintaining a desired level of quality in a product or process by careful planning, use of proper equipment, continued inspection, and corrective action as required. (Random House Unabridged Dictionary, 2d ed)Laboratories: Facilities equipped to carry out investigative procedures.Reference Values: The range or frequency distribution of a measurement in a population (of organisms, organs or things) that has not been selected for the presence of disease or abnormality.Image Interpretation, Computer-Assisted: Methods developed to aid in the interpretation of ultrasound, radiographic images, etc., for diagnosis of disease.Diagnostic Techniques, Ophthalmological: Methods and procedures for the diagnosis of diseases of the eye or of vision disorders.Evaluation Studies as Topic: Studies determining the effectiveness or value of processes, personnel, and equipment, or the material on conducting such studies. For drugs and devices, CLINICAL TRIALS AS TOPIC; DRUG EVALUATION; and DRUG EVALUATION, PRECLINICAL are available.Calibration: Determination, by measurement or comparison with a standard, of the correct value of each scale reading on a meter or other measuring instrument; or determination of the settings of a control device that correspond to particular values of voltage, current, frequency or other output.Automation: Controlled operation of an apparatus, process, or system by mechanical or electronic devices that take the place of human organs of observation, effort, and decision. (From Webster's Collegiate Dictionary, 1993)Magnetic Resonance Imaging: Non-invasive method of demonstrating internal anatomy based on the principle that atomic nuclei in a strong magnetic field absorb pulses of radiofrequency energy and emit them as radiowaves which can be reconstructed into computerized images. The concept includes proton spin tomographic techniques.Algorithms: A procedure consisting of a sequence of algebraic formulas and/or logical steps to calculate or determine a given task.Tomography, Optical Coherence: An imaging method using LASERS that is used for mapping subsurface structure. When a reflective site in the sample is at the same optical path length (coherence) as the reference mirror, the detector observes interference fringes.Image Enhancement: Improvement of the quality of a picture by various techniques, including computer processing, digital filtering, echocardiographic techniques, light and ultrastructural MICROSCOPY, fluorescence spectrometry and microscopy, scintigraphy, and in vitro image processing at the molecular level.Photography: Method of making images on a sensitized surface by exposure to light or other radiant energy.Reagent Kits, Diagnostic: Commercially prepared reagent sets, with accessory devices, containing all of the major components and literature necessary to perform one or more designated diagnostic tests or procedures. They may be for laboratory or personal use.Time Factors: Elements of limited time intervals, contributing to particular results or situations.Translations: Products resulting from the conversion of one language to another.Analysis of Variance: A statistical technique that isolates and assesses the contributions of categorical independent variables to variation in the mean of a continuous dependent variable.Equipment Design: Methods of creating machines and devices.Predictive Value of Tests: In screening and diagnostic tests, the probability that a person with a positive test is a true positive (i.e., has the disease), is referred to as the predictive value of a positive test; whereas, the predictive value of a negative test is the probability that the person with a negative test does not have the disease. Predictive value is related to the sensitivity and specificity of the test.Radiographic Image Interpretation, Computer-Assisted: Computer systems or networks designed to provide radiographic interpretive information.Blood Flow Velocity: A value equal to the total volume flow divided by the cross-sectional area of the vascular bed.Respiratory-Gated Imaging Techniques: Timing the acquisition of imaging data to specific points in the breathing cycle to minimize image blurring and other motion artifacts. The images are used diagnostically and also interventionally to coordinate radiation treatment beam on/off cycles to protect healthy tissues when they move into the beam field during different times in the breathing cycle.Feasibility Studies: Studies to determine the advantages or disadvantages, practicability, or capability of accomplishing a projected plan, study, or project.Phantoms, Imaging: Devices or objects in various imaging techniques used to visualize or enhance visualization by simulating conditions encountered in the procedure. Phantoms are used very often in procedures employing or measuring x-irradiation or radioactive material to evaluate performance. Phantoms often have properties similar to human tissue. Water demonstrates absorbing properties similar to normal tissue, hence water-filled phantoms are used to map radiation levels. Phantoms are used also as teaching aids to simulate real conditions with x-ray or ultrasonic machines. (From Iturralde, Dictionary and Handbook of Nuclear Medicine and Clinical Imaging, 1990)Anatomic Landmarks: Reference points located by visual inspection, palpation, or computer assistance, that are useful in localizing structures on or within the human body.Software: Sequential operating programs and data which instruct the functioning of a digital computer.Diet Records: Records of nutrient intake over a specific period of time, usually kept by the patient.Oligonucleotide Array Sequence Analysis: Hybridization of a nucleic acid sample to a very large set of OLIGONUCLEOTIDE PROBES, which have been attached individually in columns and rows to a solid support, to determine a BASE SEQUENCE, or to detect variations in a gene sequence, GENE EXPRESSION, or for GENE MAPPING.Questionnaires: Predetermined sets of questions used to collect data - clinical data, social status, occupational group, etc. The term is often applied to a self-completed survey instrument.Specimen Handling: Procedures for collecting, preserving, and transporting of specimens sufficiently stable to provide accurate and precise results suitable for clinical interpretation.Prospective Studies: Observation of a population for a sufficient number of persons over a sufficient number of years to generate incidence or mortality rates subsequent to the selection of the study group.Electrophoresis, Capillary: A highly-sensitive (in the picomolar range, which is 10,000-fold more sensitive than conventional electrophoresis) and efficient technique that allows separation of PROTEINS; NUCLEIC ACIDS; and CARBOHYDRATES. (Segen, Dictionary of Modern Medicine, 1992)Automation, Laboratory: Controlled operations of analytic or diagnostic processes, or systems by mechanical or electronic devices.Diet Surveys: Systematic collections of factual data pertaining to the diet of a human population within a given geographic area.Methods: A series of steps taken in order to conduct research.Tomography, X-Ray Computed: Tomography using x-ray transmission and a computer algorithm to reconstruct the image.Gene Expression Profiling: The determination of the pattern of genes expressed at the level of GENETIC TRANSCRIPTION, under specific circumstances or in a specific cell.Chromatography, High Pressure Liquid: Liquid chromatographic techniques which feature high inlet pressures, high sensitivity, and high speed.Contrast Media: Substances used to allow enhanced visualization of tissues.Nerve Fibers: Slender processes of NEURONS, including the AXONS and their glial envelopes (MYELIN SHEATH). Nerve fibers conduct nerve impulses to and from the CENTRAL NERVOUS SYSTEM.Pathology, Clinical: A subspecialty of pathology applied to the solution of clinical problems, especially the use of laboratory methods in clinical diagnosis. (Dorland, 28th ed.)Language: A verbal or nonverbal means of communicating ideas or feelings.Polymerase Chain Reaction: In vitro method for producing large amounts of specific DNA or RNA fragments of defined length and sequence from small amounts of short oligonucleotide flanking sequences (primers). The essential steps include thermal denaturation of the double-stranded target molecules, annealing of the primers to their complementary sequences, and extension of the annealed primers by enzymatic synthesis with DNA polymerase. The reaction is efficient, specific, and extremely sensitive. Uses for the reaction include disease diagnosis, detection of difficult-to-isolate pathogens, mutation analysis, genetic testing, DNA sequencing, and analyzing evolutionary relationships.Clinical Laboratory Techniques: Techniques used to carry out clinical investigative procedures in the diagnosis and therapy of disease.Glaucoma: An ocular disease, occurring in many forms, having as its primary characteristics an unstable or a sustained increase in the intraocular pressure which the eye cannot withstand without damage to its structure or impairment of its function. The consequences of the increased pressure may be manifested in a variety of symptoms, depending upon type and severity, such as excavation of the optic disk, hardness of the eyeball, corneal anesthesia, reduced visual acuity, seeing of colored halos around lights, disturbed dark adaptation, visual field defects, and headaches. (Dictionary of Visual Science, 4th ed)Brain: The part of CENTRAL NERVOUS SYSTEM that is contained within the skull (CRANIUM). Arising from the NEURAL TUBE, the embryonic brain is comprised of three major parts including PROSENCEPHALON (the forebrain); MESENCEPHALON (the midbrain); and RHOMBENCEPHALON (the hindbrain). The developed brain consists of CEREBRUM; CEREBELLUM; and other structures in the BRAIN STEM.Optic Disk: The portion of the optic nerve seen in the fundus with the ophthalmoscope. It is formed by the meeting of all the retinal ganglion cell axons as they enter the optic nerve.Limit of Detection: Concentration or quantity that is derived from the smallest measure that can be detected with reasonable certainty for a given analytical procedure.Photogrammetry: Making measurements by the use of stereoscopic photographs.Chromatography, Liquid: Chromatographic techniques in which the mobile phase is a liquid.Autoanalysis: Method of analyzing chemicals using automation.Tomography: Imaging methods that result in sharp images of objects located on a chosen plane and blurred images located above or below the plane.Radiopharmaceuticals: Compounds that are used in medicine as sources of radiation for radiotherapy and for diagnostic purposes. They have numerous uses in research and industry. (Martindale, The Extra Pharmacopoeia, 30th ed, p1161)Capillary Electrochromatography: A separation technique which combines LIQUID CHROMATOGRAPHY and CAPILLARY ELECTROPHORESIS.Corneal Pachymetry: Measurement of the thickness of the CORNEA.Mass Spectrometry: An analytical method used in determining the identity of a chemical based on its mass using mass analyzers/mass spectrometers.Cephalometry: The measurement of the dimensions of the HEAD.Knee Joint: A synovial hinge connection formed between the bones of the FEMUR; TIBIA; and PATELLA.Laboratory Proficiency Testing: Assessments aimed at determining agreement in diagnostic test results among laboratories. Identical survey samples are distributed to participating laboratories, with results stratified according to testing methodologies.Positron-Emission Tomography: An imaging technique using compounds labelled with short-lived positron-emitting radionuclides (such as carbon-11, nitrogen-13, oxygen-15 and fluorine-18) to measure cell metabolism. It has been useful in study of soft tissues such as CANCER; CARDIOVASCULAR SYSTEM; and brain. SINGLE-PHOTON EMISSION-COMPUTED TOMOGRAPHY is closely related to positron emission tomography, but uses isotopes with longer half-lives and resolution is lower.Data Interpretation, Statistical: Application of statistical procedures to analyze specific observed or assumed facts from a particular study.Linear Models: Statistical models in which the value of a parameter for a given value of a factor is assumed to be equal to a + bx, where a and b are constants. The models predict a linear regression.Statistics as Topic: The science and art of collecting, summarizing, and analyzing data that are subject to random variation. The term is also applied to the data themselves and to the summarization of the data.Blood Chemical Analysis: An examination of chemicals in the blood.Pathology: A specialty concerned with the nature and cause of disease as expressed by changes in cellular or tissue structure and function caused by the disease process.Chemistry Techniques, Analytical: Methodologies used for the isolation, identification, detection, and quantitation of chemical substances.Head: The upper part of the human body, or the front or upper part of the body of an animal, typically separated from the rest of the body by a neck, and containing the brain, mouth, and sense organs.Proteomics: The systematic study of the complete complement of proteins (PROTEOME) of organisms.Equipment Failure Analysis: The evaluation of incidents involving the loss of function of a device. These evaluations are used for a variety of purposes such as to determine the failure rates, the causes of failures, costs of failures, and the reliability and maintainability of devices.Ultrasonography, Doppler: Ultrasonography applying the Doppler effect, with frequency-shifted ultrasound reflections produced by moving targets (usually red blood cells) in the bloodstream along the ultrasound axis in direct proportion to the velocity of movement of the targets, to determine both direction and velocity of blood flow. (Stedman, 25th ed)Radiography, Dental, Digital: A rapid, low-dose, digital imaging system using a small intraoral sensor instead of radiographic film, an intensifying screen, and a charge-coupled device. It presents the possibility of reduced patient exposure and minimal distortion, although resolution and latitude are inferior to standard dental radiography. A receiver is placed in the mouth, routing signals to a computer which images the signals on a screen or in print. It includes digitizing from x-ray film or any other detector. (From MEDLINE abstracts; personal communication from Dr. Charles Berthold, NIDR)Biological Markers: Measurable and quantifiable biological parameters (e.g., specific enzyme concentration, specific hormone concentration, specific gene phenotype distribution in a population, presence of biological substances) which serve as indices for health- and physiology-related assessments, such as disease risk, psychiatric disorders, environmental exposure and its effects, disease diagnosis, metabolic processes, substance abuse, pregnancy, cell line development, epidemiologic studies, etc.Biosensing Techniques: Any of a variety of procedures which use biomolecular probes to measure the presence or concentration of biological molecules, biological structures, microorganisms, etc., by translating a biochemical interaction at the probe surface into a quantifiable physical signal.Tonometry, Ocular: Measurement of ocular tension (INTRAOCULAR PRESSURE) with a tonometer. (Cline, et al., Dictionary of Visual Science, 4th ed)Electrodes: Electric conductors through which electric currents enter or leave a medium, whether it be an electrolytic solution, solid, molten mass, gas, or vacuum.Macula Lutea: An oval area in the retina, 3 to 5 mm in diameter, usually located temporal to the posterior pole of the eye and slightly below the level of the optic disk. It is characterized by the presence of a yellow pigment diffusely permeating the inner layers, contains the fovea centralis in its center, and provides the best phototropic visual acuity. It is devoid of retinal blood vessels, except in its periphery, and receives nourishment from the choriocapillaris of the choroid. (From Cline et al., Dictionary of Visual Science, 4th ed)Artifacts: Any visible result of a procedure which is caused by the procedure itself and not by the entity being analyzed. Common examples include histological structures introduced by tissue processing, radiographic images of structures that are not naturally present in living tissue, and products of chemical reactions that occur during analysis.Microchemistry: The development and use of techniques and equipment to study or perform chemical reactions, with small quantities of materials, frequently less than a milligram or a milliliter.Radiography, Dental: Radiographic techniques used in dentistry.Arthrometry, Articular: Measurements of joint flexibility (RANGE OF MOTION, ARTICULAR), usually by employing an angle-measuring device (arthrometer). Arthrometry is used to measure ligamentous laxity and stability. It is often used to evaluate the outcome of ANTERIOR CRUCIATE LIGAMENT replacement surgery.Ultrasonography: The visualization of deep structures of the body by recording the reflections or echoes of ultrasonic pulses directed into the tissues. Use of ultrasound for imaging or diagnostic purposes employs frequencies ranging from 1.6 to 10 megahertz.Signal Processing, Computer-Assisted: Computer-assisted processing of electric, ultrasonic, or electronic signals to interpret function and activity.Fourier Analysis: Analysis based on the mathematical function first formulated by Jean-Baptiste-Joseph Fourier in 1807. The function, known as the Fourier transform, describes the sinusoidal pattern of any fluctuating pattern in the physical world in terms of its amplitude and its phase. It has broad applications in biomedicine, e.g., analysis of the x-ray crystallography data pivotal in identifying the double helical nature of DNA and in analysis of other molecules, including viruses, and the modified back-projection algorithm universally used in computerized tomography imaging, etc. (From Segen, The Dictionary of Modern Medicine, 1992)Posture: The position or attitude of the body.Bacterial Typing Techniques: Procedures for identifying types and strains of bacteria. The most frequently employed typing systems are BACTERIOPHAGE TYPING and SEROTYPING as well as bacteriocin typing and biotyping.Ultrasonography, Prenatal: The visualization of tissues during pregnancy through recording of the echoes of ultrasonic waves directed into the body. The procedure may be applied with reference to the mother or the fetus and with reference to organs or the detection of maternal or fetal disease.Magnetic Resonance Imaging, Cine: A type of imaging technique used primarily in the field of cardiology. By coordinating the fast gradient-echo MRI sequence with retrospective ECG-gating, numerous short time frames evenly spaced in the cardiac cycle are produced. These images are laced together in a cinematic display so that wall motion of the ventricles, valve motion, and blood flow patterns in the heart and great vessels can be visualized.Cone-Beam Computed Tomography: Computed tomography modalities which use a cone or pyramid-shaped beam of radiation.Analytic Sample Preparation Methods: Use of various chemical separation and extraction methods, such as SOLID PHASE EXTRACTION; CHROMATOGRAPHY; and SUPERCRITICAL FLUID EXTRACTION; to prepare samples for analytical measurement of components.Indicator Dilution Techniques: Methods for assessing flow through a system by injection of a known quantity of an indicator, such as a dye, radionuclide, or chilled liquid, into the system and monitoring its concentration over time at a specific point in the system. (From Dorland, 28th ed)Seveso Accidental Release: 1976 accidental release of DIOXINS from a manufacturing facility in Seveso, ITALY following an equipment failure.Severity of Illness Index: Levels within a diagnostic group which are established by various measurement criteria applied to the seriousness of a patient's disorder.Oxygen Radioisotopes: Unstable isotopes of oxygen that decay or disintegrate emitting radiation. O atoms with atomic weights 13, 14, 15, 19, and 20 are radioactive oxygen isotopes.ComputersWeights and Measures: Measuring and weighing systems and processes.Breath Holding: An involuntary or voluntary pause in breathing, sometimes accompanied by loss of consciousness.Anatomy, Cross-Sectional: Descriptive anatomy based on three-dimensional imaging (IMAGING, THREE-DIMENSIONAL) of the body, organs, and structures using a series of computer multiplane sections, displayed by transverse, coronal, and sagittal analyses. It is essential to accurate interpretation by the radiologist of such techniques as ultrasonic diagnosis, MAGNETIC RESONANCE IMAGING, and computed tomography (TOMOGRAPHY, X-RAY COMPUTED). (From Lane & Sharfaei, Modern Sectional Anatomy, 1992, Preface)Tandem Mass Spectrometry: A mass spectrometry technique using two (MS/MS) or more mass analyzers. With two in tandem, the precursor ions are mass-selected by a first mass analyzer, and focused into a collision region where they are then fragmented into product ions which are then characterized by a second mass analyzer. A variety of techniques are used to separate the compounds, ionize them, and introduce them to the first mass analyzer. For example, for in GC-MS/MS, GAS CHROMATOGRAPHY-MASS SPECTROMETRY is involved in separating relatively small compounds by GAS CHROMATOGRAPHY prior to injecting them into an ionization chamber for the mass selection.Immunoassay: A technique using antibodies for identifying or quantifying a substance. Usually the substance being studied serves as antigen both in antibody production and in measurement of antibody by the test substance.Statistics, Nonparametric: A class of statistical methods applicable to a large set of probability distributions used to test for correlation, location, independence, etc. In most nonparametric statistical tests, the original scores or observations are replaced by another variable containing less information. An important class of nonparametric tests employs the ordinal properties of the data. Another class of tests uses information about whether an observation is above or below some fixed value such as the median, and a third class is based on the frequency of the occurrence of runs in the data. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed, p1284; Corsini, Concise Encyclopedia of Psychology, 1987, p764-5)Fundus Oculi: The concave interior of the eye, consisting of the retina, the choroid, the sclera, the optic disk, and blood vessels, seen by means of the ophthalmoscope. (Cline et al., Dictionary of Visual Science, 4th ed)Radiographic Image Enhancement: Improvement in the quality of an x-ray image by use of an intensifying screen, tube, or filter and by optimum exposure techniques. Digital processing methods are often employed.Bacteriological Techniques: Techniques used in studying bacteria.Plethysmography: Recording of change in the size of a part as modified by the circulation in it.Moire Topography: A method of three-dimensional morphometry in which contour maps are produced from the overlapping interference fringes created when an object is illuminated by beams of coherent light issuing from two different point sources.Gated Blood-Pool Imaging: Radionuclide ventriculography where scintigraphic data is acquired during repeated cardiac cycles at specific times in the cycle, using an electrocardiographic synchronizer or gating device. Analysis of right ventricular function is difficult with this technique; that is best evaluated by first-pass ventriculography (VENTRICULOGRAPHY, FIRST-PASS).Interferometry: Measurement of distances or movements by means of the phenomena caused by the interference of two rays of light (optical interferometry) or of sound (acoustic interferometry).Perfusion Imaging: The creation and display of functional images showing where the blood flow reaches by following the distribution of tracers injected into the blood stream.Healthy Volunteers: Persons with no known significant health problems who are recruited to participate in research to test a new drug, device, or intervention as controls for a patient group. (from http://clinicalcenter.nih.gov/recruit/volunteers.html, accessed 2/14/2013)Diagnosis, Computer-Assisted: Application of computer programs designed to assist the physician in solving a diagnostic problem.Diagnostic Errors: Incorrect diagnoses after clinical examination or technical diagnostic procedures.Exercise Test: Controlled physical activity which is performed in order to allow assessment of physiological functions, particularly cardiovascular and pulmonary, but also aerobic capacity. Maximal (most intense) exercise is usually required but submaximal exercise is also used.Biological Assay: A method of measuring the effects of a biologically active substance using an intermediate in vivo or in vitro tissue or cell model under controlled conditions. It includes virulence studies in animal fetuses in utero, mouse convulsion bioassay of insulin, quantitation of tumor-initiator systems in mouse skin, calculation of potentiating effects of a hormonal factor in an isolated strip of contracting stomach muscle, etc.Colorimetry: Any technique by which an unknown color is evaluated in terms of standard colors. The technique may be visual, photoelectric, or indirect by means of spectrophotometry. It is used in chemistry and physics. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)Tomography, Emission-Computed, Single-Photon: A method of computed tomography that uses radionuclides which emit a single photon of a given energy. The camera is rotated 180 or 360 degrees around the patient to capture images at multiple positions along the arc. The computer is then used to reconstruct the transaxial, sagittal, and coronal images from the 3-dimensional distribution of radionuclides in the organ. The advantages of SPECT are that it can be used to observe biochemical and physiological processes as well as size and volume of the organ. The disadvantage is that, unlike positron-emission tomography where the positron-electron annihilation results in the emission of 2 photons at 180 degrees from each other, SPECT requires physical collimation to line up the photons, which results in the loss of many available photons and hence degrades the image.Technetium Tc 99m Mertiatide: A technetium diagnostic aid used in renal function determination.Conductometry: Determination of the quantity of a material present in a mixture by measurement of its effect on the electrical conductivity of the mixture. (Webster, 3d ed)False Positive Reactions: Positive test results in subjects who do not possess the attribute for which the test is conducted. The labeling of healthy persons as diseased when screening in the detection of disease. (Last, A Dictionary of Epidemiology, 2d ed)Technetium Tc 99m Diethyl-iminodiacetic Acid: A nontoxic radiopharmaceutical that is used in the clinical evaluation of hepatobiliary disorders in humans.Microcomputers: Small computers using LSI (large-scale integration) microprocessor chips as the CPU (central processing unit) and semiconductor memories for compact, inexpensive storage of program instructions and data. They are smaller and less expensive than minicomputers and are usually built into a dedicated system where they are optimized for a particular application. "Microprocessor" may refer to just the CPU or the entire microcomputer.Breath Tests: Any tests done on exhaled air.Tomography, Emission-Computed: Tomography using radioactive emissions from injected RADIONUCLIDES and computer ALGORITHMS to reconstruct an image.Indicators and Reagents: Substances used for the detection, identification, analysis, etc. of chemical, biological, or pathologic processes or conditions. Indicators are substances that change in physical appearance, e.g., color, at or approaching the endpoint of a chemical titration, e.g., on the passage between acidity and alkalinity. Reagents are substances used for the detection or determination of another substance by chemical or microscopical means, especially analysis. Types of reagents are precipitants, solvents, oxidizers, reducers, fluxes, and colorimetric reagents. (From Grant & Hackh's Chemical Dictionary, 5th ed, p301, p499)Models, Statistical: Statistical formulations or analyses which, when applied to data and found to fit the data, are then used to verify the assumptions and parameters used in the analysis. Examples of statistical models are the linear model, binomial model, polynomial model, two-parameter model, etc.Ophthalmology: A surgical specialty concerned with the structure and function of the eye and the medical and surgical treatment of its defects and diseases.Software Validation: The act of testing the software for compliance with a standard.Physical Examination: Systematic and thorough inspection of the patient for physical signs of disease or abnormality.Anterior Chamber: The space in the eye, filled with aqueous humor, bounded anteriorly by the cornea and a small portion of the sclera and posteriorly by a small portion of the ciliary body, the iris, and that part of the crystalline lens which presents through the pupil. (Cline et al., Dictionary of Visual Science, 4th ed, p109)Automatic Data Processing: Data processing largely performed by automatic means.Smiling: A facial expression which may denote feelings of pleasure, affection, amusement, etc.DNA Fingerprinting: A technique for identifying individuals of a species that is based on the uniqueness of their DNA sequence. Uniqueness is determined by identifying which combination of allelic variations occur in the individual at a statistically relevant number of different loci. In forensic studies, RESTRICTION FRAGMENT LENGTH POLYMORPHISM of multiple, highly polymorphic VNTR LOCI or MICROSATELLITE REPEAT loci are analyzed. The number of loci used for the profile depends on the ALLELE FREQUENCY in the population.Gas Chromatography-Mass Spectrometry: A microanalytical technique combining mass spectrometry and gas chromatography for the qualitative as well as quantitative determinations of compounds.Lasers: An optical source that emits photons in a coherent beam. Light Amplification by Stimulated Emission of Radiation (LASER) is brought about using devices that transform light of varying frequencies into a single intense, nearly nondivergent beam of monochromatic radiation. Lasers operate in the infrared, visible, ultraviolet, or X-ray regions of the spectrum.Nucleic Acid Amplification Techniques: Laboratory techniques that involve the in-vitro synthesis of many copies of DNA or RNA from one original template.Osteoarthritis, Knee: Noninflammatory degenerative disease of the knee joint consisting of three large categories: conditions that block normal synchronous movement, conditions that produce abnormal pathways of motion, and conditions that cause stress concentration resulting in changes to articular cartilage. (Crenshaw, Campbell's Operative Orthopaedics, 8th ed, p2019)Radiographic Magnification: Use of optic and geometric techniques to enhance radiographic image quality and interpretation. It includes use of microfocal X-ray tubes and intensifying fluoroscopic screens.Cluster Analysis: A set of statistical methods used to group variables or observations into strongly inter-related subgroups. In epidemiology, it may be used to analyze a closely grouped series of events or cases of disease or other health-related phenomenon with well-defined distribution patterns in relation to time or place or both.Blood Pressure Determination: Techniques for measuring blood pressure.Molecular Diagnostic Techniques: MOLECULAR BIOLOGY techniques used in the diagnosis of disease.Single-Blind Method: A method in which either the observer(s) or the subject(s) is kept ignorant of the group to which the subjects are assigned.X-Ray Intensifying Screens: Screens which absorb the energy in the x-ray beam that has penetrated the patient and convert this energy into a light pattern which has as nearly as possible the same information as the original x-ray beam. The more light a screen produces for a given input of x-radiation, the less x-ray exposure and thus shorter exposure time are needed to expose the film. In most film-screen systems, the film is sandwiched between two screens in a cassette so that the emulsion on each side is exposed to the light from its contiguous screen.Pulsatile Flow: Rhythmic, intermittent propagation of a fluid through a BLOOD VESSEL or piping system, in contrast to constant, smooth propagation, which produces laminar flow.Gonioscopy: Examination of the angle of the anterior chamber of the eye with a specialized optical instrument (gonioscope) or a contact prism lens.Intraocular Pressure: The pressure of the fluids in the eye.Breast Neoplasms: Tumors or cancer of the human BREAST.Photometry: Measurement of the various properties of light.Diet: Regular course of eating and drinking adopted by a person or animal.Diagnostic Imaging: Any visual display of structural or functional patterns of organs or tissues for diagnostic evaluation. It includes measuring physiologic and metabolic responses to physical and chemical stimuli, as well as ultramicroscopy.Paraffin Embedding: The infiltrating of tissue specimens with paraffin, as a supporting substance, to prepare for sectioning with a microtome.Microbial Sensitivity Tests: Any tests that demonstrate the relative efficacy of different chemotherapeutic agents against specific microorganisms (i.e., bacteria, fungi, viruses).Protein Array Analysis: Ligand-binding assays that measure protein-protein, protein-small molecule, or protein-nucleic acid interactions using a very large set of capturing molecules, i.e., those attached separately on a solid support, to measure the presence or interaction of target molecules in the sample.Enzyme-Linked Immunosorbent Assay: An immunoassay utilizing an antibody labeled with an enzyme marker such as horseradish peroxidase. While either the enzyme or the antibody is bound to an immunosorbent substrate, they both retain their biologic activity; the change in enzyme activity as a result of the enzyme-antibody-antigen reaction is proportional to the concentration of the antigen and can be measured spectrophotometrically or with the naked eye. Many variations of the method have been developed.Tissue Fixation: The technique of using FIXATIVES in the preparation of cytologic, histologic, or pathologic specimens for the purpose of maintaining the existing form and structure of all the constituent elements.Proteome: The protein complement of an organism coded for by its genome.Enzymes, Immobilized: Enzymes which are immobilized on or in a variety of water-soluble or water-insoluble matrices with little or no loss of their catalytic activity. Since they can be reused continuously, immobilized enzymes have found wide application in the industrial, medical and research fields.Biopsy: Removal and pathologic examination of specimens in the form of small pieces of tissue from the living body.Cardiac-Gated Imaging Techniques: Timing the acquisition of imaging data to specific points in the cardiac cycle to minimize image blurring and other motion artifacts.Case-Control Studies: Studies which start with the identification of persons with a disease of interest and a control (comparison, referent) group without the disease. The relationship of an attribute to the disease is examined by comparing diseased and non-diseased persons with regard to the frequency or levels of the attribute in each group.Dental Instruments: Hand-held tools or implements especially used by dental professionals for the performance of clinical tasks.Photography, Dental: Photographic techniques used in ORTHODONTICS; DENTAL ESTHETICS; and patient education.BrazilMandible: The largest and strongest bone of the FACE constituting the lower jaw. It supports the lower teeth.Perinatology: The branch of medicine dealing with the fetus and infant during the perinatal period. The perinatal period begins with the twenty-eighth week of gestation and ends twenty-eight days after birth. (From Dorland, 27th ed)Cyclopentolate: A parasympatholytic anticholinergic used solely to obtain mydriasis or cycloplegia.Fluorine Radioisotopes: Unstable isotopes of fluorine that decay or disintegrate emitting radiation. F atoms with atomic weights 17, 18, and 20-22 are radioactive fluorine isotopes.Dental Caries Activity Tests: Diagnostic tests conducted in order to measure the increment of active DENTAL CARIES over a period of time.