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Encyclopedia > Medical imaging

Medical imaging designates the ensemble of techniques and processes used to create images of the human body (or parts thereof) for clinical purposes (medical procedures seeking to reveal, diagnose or examine disease) or medical science (including the study of normal anatomy and function). As a discipline and in its widest sense, it is part of biological imaging and incorporates radiology (in the wider sense), radiological sciences, endoscopy, (medical) thermography, medical photography and microscopy (e.g. for human pathological investigations). Measurement and recording techniques which are not primarily designed to produce images, such as electroencephalography (EEG) and magnetoencephalography (MEG) and others, but which produce data susceptible to be represented as maps (i.e. containing positional information), can be seen as forms of medical imaging. Image File history File links 50pman_medical_imaging. ... Image File history File links 50pman_medical_imaging. ... In common usage, an image (from Latin imago) or picture is an artifact that reproduces the likeness of some subject—usually a physical object or a person. ... A medical procedure is a course of action intended to achieve a result in the care of patients, used by medical or paramedical personnel. ... Diagnosis (from the Greek words dia = by and gnosis = knowledge) is the process of identifying a disease by its signs, symptoms and results of various diagnostic procedures. ... A disease or medical condition is an abnormality of the body or mind that causes discomfort, dysfunction, distress, or death to the person afflicted or those in contact with the person. ... Image A: A normal chest X-ray. ... Endoscopic images of a duodenal ulcer Endoscopy means looking inside and refers to looking inside the human body for medical reasons. ... Thermography can refer to a printing process and an imaging process. ... It has been suggested that this article or section be merged into microscope. ... In common usage, an image (from Latin imago) or picture is an artifact that reproduces the likeness of some subject—usually a physical object or a person. ... Electroencephalography is the neurophysiologic measurement of the electrical activity of the brain by recording from electrodes placed on the scalp or, in special cases, subdurally or in the cerebral cortex. ... EEG can mean: Electroencephalography - the method and science of recording and interpreting traces of brain electrical activity as recorded from the skull surface or the device used to record such traces Emperor Entertainment Group - A Hong Kong entertainment company. ... Magnetoencephalography (MEG) is the measurement of the magnetic fields produced by electrical activity in the brain, usually conducted externally, using extremely sensitive devices such as SQUIDs. ... Meg may refer to: Meg (film), unproduced. ... A map is a simplified depiction of a space which highlights relations between components (objects, regions) of that space. ...


In the clinical context, medical imaging is generally equated to Radiology or Clinical imaging and the medical practician responsible for interpreting (and sometimes acquiring) the images is a radiologist. Diagnostic radiography (see Radiography) designates the technical aspects of medical imaging and in particular the acquisition of medical images. The radiographer or radiologic technologist is usually responsible for acquiring medical images of diagnostic quality, although some radiological interventions are performed by radiologists. Image A: A normal chest X-ray. ... Please wikify (format) this article or section as suggested in the Guide to layout and the Manual of Style. ... Radiology is the branch of medical science dealing with the medical use of x-ray machines or other such radiation devices. ... Radiography is the creation of images by exposing a photographic film or other image receptor to X-rays. ... Radiography is the creation of radiographs, photographs made by exposing a photographic film or other image receptor to X-rays. ... Radiology is the branch of medical science dealing with the medical use of x-ray machines or other such radiation devices. ...


As a field of scientific investigation, medical imaging constitutes a sub-discipline of biomedical engineering, medical physics or medicine depending on the context: Research and development in the area of instrumentation, image acquisition (e.g. radiography), modelling and quantification are usually the preserve of biomedical engineering, medical physics and computer science; Research into the application and interpretation of medical images is usually the preserve of radiology and the medical sub-discipline relevant to medical condition or area of medical science (neuroscience, cardiology, psychiatry, psychology, etc) under investigation. Many of the techniques developed for medical imaging also have scientific and industrial applications. The AbioCor artificial heart, an example of a biomedical engineering application of mechanical engineering with biocompatible materials for Cardiothoracic Surgery using an artificial organ. ... Medical physics is a branch of applied physics concerning the application of physics to medicine. ... This article is about the field and science of medical practice and health care. ... Radiography is the creation of images by exposing a photographic film or other image receptor to X-rays. ... The AbioCor artificial heart, an example of a biomedical engineering application of mechanical engineering with biocompatible materials for Cardiothoracic Surgery using an artificial organ. ... Medical physics is a branch of applied physics concerning the application of physics to medicine. ... Computer science, or computing science, is the study of the theoretical foundations of information and computation and their implementation and application in computer systems. ... Image A: A normal chest X-ray. ... Drawing of the cells in the chicken cerebellum by S. Ramón y Cajal Neuroscience is a field that is devoted to the scientific study of the nervous system. ... Cardiology is the branch of medicine dealing with disorders of the heart and blood vessels. ... Psychiatrist redirects here, for the party game, see Psychiatrist (game) Psychiatry is a medical specialty dealing with the prevention, assessment, diagnosis, treatment, and rehabilitation of mental illness. ... Psychology is an academic and applied field involving the scientific study of mental processes and behavior. ... Part of a scientific laboratory at the University of Cologne. ...


Medical imaging is often perceived to designate the set of techniques that produce images of the internal aspect of the body (without having to open it). In this restricted sense, medical imaging can be seen as the solution of mathematical inverse problems. This means that cause (the properties of living tissue) is inferred from effect (the observed signal). In the case of ultrasonography the probe consists of ultrasonic pressure waves and echoes inside the tissue show the internal structure. In the case of projection radiography, the probe is X-ray radiation which is absorbed at different rates in different tissue types such as bone, muscle and fat. Euclid, Greek mathematician, 3rd century BC, known today as the father of geometry; shown here in a detail of The School of Athens by Raphael. ... The inverse problem is the task that often occurs in many branches of science and mathematics where the values of some model parameter(s) must be obtained via manipulation of observed data. ... In the NATO phonetic alphabet, X-ray represents the letter X. An X-ray picture (radiograph) taken by Röntgen An X-ray is a form of electromagnetic radiation with a wavelength approximately in the range of 5 pm to 10 nanometers (corresponding to frequencies in the range 30 PHz... Electromagnetic radiation can be imagined as a self-propagating transverse oscillating wave of electric and magnetic fields. ...

Contents

Modern imaging technology

Fluoroscopy

Main article: Fluoroscopy

Fluoroscopy produces real-time images of internal structures of the body in a similar fashion to radiography, but employs a constant input of x rays. Contrast media, such as barium, iodine, and air are used to visualize internal organs as they work. Fluoroscopy is also used in image-guided procedures when constant feedback during a procedure is required. A modern fluoroscope. ... Radiography is the creation of images by exposing a photographic film or other image receptor to X-rays. ... In the NATO phonetic alphabet, X-ray represents the letter X. An X-ray picture (radiograph) taken by Röntgen An X-ray is a form of electromagnetic radiation with a wavelength approximately in the range of 5 pm to 10 nanometers (corresponding to frequencies in the range 30 PHz...


Magnetic resonance imaging (MRI)

A Mangetic Resonance Imaging instrument (MRI scanner) uses powerful magnets to polarise and excite hydrogen nuclei (single proton)) in water molecules in human tissue, producing a detectable signal which is spatially encoded resulting in images of the body. In brief, MRI involves the use of three kinds of electromagnetic field: a very strong (of the order of units of Tesla) static magnetic field to polarize the hydrogen nuclei, called the static field; a weaker time-varying (of the order of 1kHz) for spatial encoding, called the gradient field(s); and a weak radio-frequency (RF) field for manipulation of the hydrogen nuclei to produce measurable signals, collected through an RF antenna. Like CT, MRI traditionally creates a 2D image of a thin "slice" of the body and is therefore considered a tomographic imaging technique. Modern MRI instruments are capable of producing images in the form of 3D blocks, which may be considered a generalisation of the single-slice, tomographic, concept. Unlike CT, MRI does not involve the use of ionizing radiation and is therefore not associated with the same health hazards; for example there are no known long term effects of exposure to strong static fields (this is the subject of some debate; see 'Safety' in MRI) and therefore there is no limit on the number of scans to which an individual can be subjected, in contrast with X-ray and CT. However, there are well identified health risks associated with tissue heating from exposure to the RF field and the presence of implanted devices in the body, such as pace makers. These risks are strictly controlled as part of the design of the instrument and the scanning protocols used. CT and MRI being sensitive to different properties of the tissue, the appearance of the images obtained with the two techniques differ markedly. In CT, X-rays must be blocked by some form of dense tissue to create an image, therefore the image quality when looking at soft tissues will be poor. An MRI can ONLY "see" hydrogen based objects, so bone, which is calcium based, will be a void in the image, and will not affect soft tissue views. This makes it excellent for peering into the brain and joints. This article or section does not cite its references or sources. ... Image File history File links Brain_Mri_nevit. ... Image File history File links Brain_Mri_nevit. ... General Name, Symbol, Number hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1, 1, s Appearance colorless Atomic mass 1. ... Properties [1][2] In physics, the proton (Greek proton = first) is a subatomic particle with an electric charge of one positive fundamental unit (1. ... This article or section may be confusing or unclear for some readers, and should be edited to rectify this. ... Tesla can refer to: Scientist and inventor Nikola Tesla The tesla, an SI unit named after Nikola Tesla. ... Rough plot of Earths atmospheric transmittance (or opacity) to various wavelengths of electromagnetic radiation, including radio waves. ... RF may be: RF is the IATA code for Florida West International Airways Rf or RF may stand for: Radio frequency, a term in broadcasting. ... In biology, antenna (plural: antennae) refers to the sensing organs of several arthropods. ... Ionizing radiation has many practical uses, but it is also dangerous to human health. ... The mri are a fictional alien species in the Faded Sun Trilogy of C.J. Cherryh. ... In the NATO phonetic alphabet, X-ray represents the letter X. An X-ray picture (radiograph) taken by Röntgen An X-ray is a form of electromagnetic radiation with a wavelength approximately in the range of 5 pm to 10 nanometers (corresponding to frequencies in the range 30 PHz... Look up CT, Ct, ct in Wiktionary, the free dictionary. ...


MRI, or "NMR imaging" as it was originally known, has only been in use since the early 1980's. Effects from long term, or repeated exposure, to the intense static magnetic field are not known.


Nuclear Medicine

Main article: Nuclear Medicine

Images from gamma cameras are used in Nuclear Medicine to detect regions of biological activity that are often associated with diseases. A short lived isotope, such as 131I is administered to the patient. These isotopes are more readily absorbed by biologically active regions of the body, such as tumors or fracture points in bones. Bone scintigraphy of a young woman. ... Diagrammatic cross section of a gamma camera detector A gamma camera is an imaging device, most commonly used as a medical imaging device in nuclear medicine. ... Isotopes are any of the several different forms of an element each having different atomic mass. ... Iodine-131, also called radioiodine, is a radioisotope of iodine. ... A fracture is the separation of a body into two, or more, pieces under the action of stress. ...


Positron Emission Tomography (PET)

Positron Emission Tomography is used to detect certain brain diseases. Similiarly to Nuclear Medicine, a short-lived isotope, such as 18F, is incorporated into a substance used by the body such as glucose which is abosrbed by the tumor of interest. PET scans are often viewed along side computed tomography scans, which can be performed on the same equipment without moving the patient. This allows the tumors detected by the PET scan to be viewed next to the rest of the patient's anatomy detected by the CT scan. Image of a typical positron emission tomography (PET) facility Positron emission tomography (PET) is a nuclear medicine medical imaging technique which produces a three dimensional image or map of functional processes in the body. ... Glucose (Glc), a monosaccharide (or simple sugar), is the most important carbohydrate in biology. ... This article does not cite its references or sources. ...


Projection Radiography

Radiographs, more commonly known as x-rays, are often used to determine the type and extent of a fracture as well as for detecting pathological changes in the lungs. With the use of radio-opaque contrast media, such as barium, they can also be used to visualize the structure of the stomach and intestines - this can help diagnose ulcers or certain types of colon cancer. In the NATO phonetic alphabet, X-ray represents the letter X. An X-ray picture (radiograph) taken by Röntgen An X-ray is a form of electromagnetic radiation with a wavelength approximately in the range of 5 pm to 10 nanometers (corresponding to frequencies in the range 30 PHz... General Name, Symbol, Number barium, Ba, 56 Chemical series alkaline earth metals Group, Period, Block 2, 6, s Appearance silvery white Atomic mass 137. ... Diagram of the stomach, colon, and rectum Colorectal cancer includes cancerous growths in the colon, rectum and appendix. ...


Tomography

Tomography is the method of imaging a single plane, or slice, of an object resulting in a tomogram. There are several forms of tomography: Tomography is imaging by sections or sectioning. ... Tomography involves the generation of a two-dimensional image representing a slice or section through a three-dimensional object. ... Tomography is imaging by sections or sectioning. ...


Linear Tomography: This is the most basic form of tomography. The X-ray tube moved from point "A" to point "B" above the patient, while the cassette holder (or "bucky") moves simultaneously under the patient from point "B" to point "A." The fulcrum, or pivot point, is set to the area of interest. In this manner, the points above and below the focal plane are blurred out, just as the background is blurred when panning a camera during exposure. No longer carried out and replaced by computed tomography. Look up Fulcrum in Wiktionary, the free dictionary Fulcrum may refer to one of the following. ... The focal plane of a lens is a plane that is perpendicular to the axis of the lens and passes through its focus. ... This article does not cite its references or sources. ...


Poly Tomography: This was a complex form of tomography. With this technique, a number of geometrical movements were programmed, such as hypocycloidic, circular, figure 8, and elliptical. Philips Medical Systems [1] produced one such device called the 'Polytome.' No longer carried out, replaced by computed tomography. This article does not cite its references or sources. ...


Zonography: This is a variant of linear tomography, where a limited arc of movement is used. It is still used in some centres for visualising the kidney during an intravenous urogram (IVU)


Orthopantomography (OPT): The only common tomographic examination in use. This makes use of a complex movement to allow the radiographic examination of the mandible, as if it were a flat bone. It is often referred to as a "Panaray", but this is incorrect, as it is a trademark of a specific company's equipment


Computed Tomography (CAT or CT): (Main article: computed tomography): A CT scan, also known as a CAT scan (Computed Axial Tomography scan), is a helical tomography (latest generation), which traditionally produces a 2D image of the structures in a thin section of the body. It uses X-rays. It has a greater ionizing radiation dose burden than projection radiography, repeated scans should be limited. This article does not cite its references or sources. ... CAT apparatus in a hospital Computed axial tomography (CAT), computer-assisted tomography, computed tomography, CT, or body section roentgenography is the process of using digital processing to generate a three-dimensional image of the internals of an object from a large series of two-dimensional X-ray images taken around... In the NATO phonetic alphabet, X-ray represents the letter X. An X-ray picture (radiograph) taken by Röntgen An X-ray is a form of electromagnetic radiation with a wavelength approximately in the range of 5 pm to 10 nanometers (corresponding to frequencies in the range 30 PHz... Ionizing radiation has many practical uses, but it is also dangerous to human health. ...


Ultrasound

Medical ultrasonography uses high frequency sound waves of between 2.0 to 10.0 megahertz that are reflected by tissue to varying degrees to produce a 2D image, traditionally on a TV monitor. This is often used to visualize the fetus in pregnant women. Other important uses include imaging the abdominal organs, heart, male genitalia and the veins of the leg. While it may provide less anatomical information than techniques such as CT or MRI, it has several advantages which make it ideal as a first line test in numerous situations, in particular that it studies the function of moving structures in real-time. It is also very safe to use, as the patient is not exposed to radiation and the ultrasound does not appear to cause any adverse effects, although information on this is not well documented. It is also relatively cheap and quick to perform. Ultrasound scanners can be taken to critically ill patients in intensive care units, avoiding the danger caused while moving the patient to the radiology department. The real time moving image obtained can be used to guide drainage and biopsy procedures. Doppler capabilities on modern scanners allow the blood flow in arteries and veins to be assessed. Medical ultrasonography (sonography) is an ultrasound-based diagnostic imaging technique used to visualize muscles and internal organs, their size, structure and any pathological lesions, making them useful for scanning the organs. ... Medical ultrasonography (sonography) is an ultrasound-based diagnostic imaging technique used to visualize muscles and internal organs, their size, structure and any pathological lesions, making them useful for scanning the organs. ... MegaHertz (MHz) is the name given to one million (106) Hertz, a measure of frequency. ... A human fetus A fetus (or foetus, or fœtus – see below) is a developing mammal after the embryonic stage and before birth. ...


Clinical Imaging, or Biological Imaging Techniques

Electron Microscopy

Main article: Electron microscope

The electron microscope is a microscope that can magnify very small details with high resolving power due to the use of electrons as the source of illumination, magnifying at levels up to 2,000,000 times. A transmission electron microscope. ...


Electron microscopy is employed in anatomic pathology to identify organelles within the cells. Its usefulness has been greatly reduced by immunhistochemistry but it is still irreplaceable for the diagnosis of kidney disease, identification of immotile cilia syndrome and many other tasks. Anatomic pathology is the branch of pathology that is concerned with the diagnosis of disease based on the gross and microscopic examination of cells and tissues. ...


Creation of three-dimensional images

Recently, techniques have been developed to enable CT, MRI and Ultrasound scanning software to produce 3D images for the physician. Traditionally CT and MRI scans produced 2D static output on film. To produce 3D images, many scans are made, then combined by computers to produce a 3D model, which can then be manipulated by the physician. 3D ultrasounds are produced using a somewhat similar technique.


With the ability to visualize important structures in great detail, 3D visualization methods are a valuable resource for the diagnosis and surgical treatment of many pathologies. It was a key resource (and also the cause of failure) for the famous, but ultimately unsuccessful attempt by Singaporean surgeons to separate Iranian twins Ladan and Laleh Bijani in 2003. The 3D equipment was used previously for similar operations with great success. Ladan and Laleh Bijani (in Persian: لادن و لاله بیژنی) (January 17, 1974–July 8, 2003) were Iranian law graduates. ...


Other proposed or developed techniques include:

Some of these techniques are still at a research stage and not yet used in clinical routines. Diffuse optical imaging is a medical imaging modality which uses near infrared light to generate images of the body. ... Elastography is an emerging method in which stiffness or strain images of soft tissue are used to detect tumors. ... Electrical Impedance Tomograpy (EIT), is a medical imaging technique in which an image of the conductivity or permittivity of part of the body is inferred from surface electrical measurements. ... Central to optoacoustic imaging is the optoacoustic effect whereby pulsed laser energy is absorbed by a medium causing a local temperature increase followed by the generation of pressure transients (acoustic waves). ... A phoropter in use. ... A-scan ultrasound biometry, commonly referred to as an A-scan, is routine type of diagnostic test used in ophthalmology. ... B-scan ultrasonography, or B-scan, is a diagnostic test used in ophthalmology to produce a two-dimensional, cross-sectional view of the eye and the orbit. ... A corneal topogram. ... Optical coherence tomography (OCT) is an interferometric, non-invasive optical tomographic imaging technique offering millimeter penetration (approximately 2--3 mm in tissue) with sub-micrometre axial and lateral resolution. ... Scanning laser ophthalmoscopy is a relatively new technology used in the diagnosis of glaucoma. ...


Non-diagnostic imaging

Neuroimaging has also been used in experimental circumstances to allow people (especially disabled persons) to control outside devices, acting as a brain computer interface. Neuroimaging includes the use of various techniques to either directly or indirectly image the structure, function, or pharmacology of the brain. ... A brain-computer interface (BCI) or direct neural interface is literally a direct technological interface between a brain and a computer not requiring any motor output from the user. ...


Medical Imaging Service

This is a specialized area of medical equipment service and repair, which is separate from the Biomedical field. Although a hospital with their own service group may include them in the Biomed department. Health science is the discipline of applied science which deals with human and animal health. ...


At one time, there were only two ways to receive training for this field. One was to learn it in the military, and the other was On-The-Job training (OJT) from the manufacturer. But since the 1980's several independent training centers have been started. One such school is RSTI [2].


There are different means of employment in this occupation. Working for the manufacturer's field service department (OEM), working for a hospital (In-house), and working for an independent (Outside, or Independent provider). The most stable positions are with the OEM or hospital, as you can remain current through on-going training, and the two have good working relationships.


The OEM Service Engineer can expect to spend a lot of time driving from one site to another during the work day, and working non-standard hours. They will install, remove, diagnose, repair, calibrate, perform preventive maintenance, and interface equipment, all while ensuring good customer relations. You may also be required to do yearly testing of the radiation sources for Federal [3] and State compliance.


The In-house person is employed by the hospital. With larger medical facilities, travel between the hospitals' other locations may be required to perform the required services. You may also be required to do yearly testing of the radiation sources for compliance. The OEM or independent will provide installation of purchased equipment, and can be used for back-up service.


An independent is typically someone who has left an OEM, and started their own service business. Staying up-to-date as an independent can be difficult and expensive, as the OEM is usually reluctant to provide training. However, non-OEM training facilities are available, such as the aformentioned RSTI. Competition for service can be aggressive, with OEM's giving hospitals or clinics a reduction in equipment purchase price if they retain some form of OEM service.


The Independent may also sell and install refurbished equipment, or de-install equipment. They will repair, calibrate, and perform preventative maintenance. Because many of the tasks associated with imaging service require expensive, specialized equipment, there may be a financial limit to the independent. Typical equipment used routinely are a Storage Oscilloscope and multimeter (if servicing old vacuum-state equipment, a VOM would be helpful). Additional equipment: Keithley Dosimeter, mAs meter, Biddle contact tachometer, Light to radiation template, etc. A Tektronix model 475A portable analogue oscilloscope, a very typical instrument of the late 1970s. ... howard piA digital multimeter A low cost digital multimeter An analog multimeter A multimeter is an electronic measuring instrument that combines several functions in one unit. ...


See also

A medical test is any kind of diagnostic procedure performed for health reasons. ... In medicine, physical examination is the process by which the physician investigates the body of a patient for signs of disease to aid in determining the correct diagnosis. ... In medical imaging, picture archiving and communication systems (PACS) are computers or networks dedicated to the storage, retrieval, distribution and presentation of images. ... Tomography involves the generation of a two-dimensional image representing a slice or section through a three-dimensional object. ... Digital Imaging and Communications in Medicine (DICOM) is a comprehensive set of standards for handling, storing, printing, and transmitting information in medical imaging. ... Biomedical informatics encompasses both medical informatics (or healthcare informatics) and bioinformatics. ... In image analysis, segmentation is the partition of a digital image into multiple regions (sets of pixels), according to some criterion. ... Signal-to-noise ratio (often abbreviated SNR or S/N) is meaningful both in the context of Electrical engineering and, informally, for Usenet or other newsgroup-like services. ...

External links


  Results from FactBites:
 
Medical imaging - Wikipedia, the free encyclopedia (850 words)
Medical imaging is the process by which sonographers evaluate an area of the subject's body that is not normally visible.
Medical imaging may be "clinical", seeking to diagnose and examine disease in specific human patients (see pathology).
Medical ultrasonography uses high frequency sound waves of between 3.5 to 7.0 megahertz that are reflected by tissue to varying degrees to produce a 2D image, traditionally on a TV monitor.
Medical Imaging: October 2005: The Changing Face of Women's Imaging (164 words)
Medical Imaging: October 2005: The Changing Face of Women's Imaging
Converging technologies in imaging are altering womenÂ’s healthcare, making room for quicker diagnoses and treatments.
Improvements in pediatric imaging are providing faster scans, less radiation, and better distraction methods—pluses for patients and physicians alike.
  More results at FactBites »

 
 

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