NationMaster - Encyclopedia: Computed axial tomography

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CT apparatus in a hospital

Computed axial Tomography refers to imaging by sections or sectioning. Please see: Computed axial tomography (CT) Electrical impedance tomography (EIT) Positron emission tomography (PET) Optical coherence tomography (OCT) Single photon emission computed tomography (SPECT) Tomogram Tomographic reconstruction This is a disambiguation page — a navigational aid which lists other pages that might... tomography (CAT), computer-assisted tomography, computed tomography, CT, or body section roentgenography is the process of using digital processing to generate a 3-D or 3D abbreviates three dimensional and is often related to a stereoscopic display that exploits binocular vision. Three dimensional objects have volume and may be measured and described using three orthogonal directions. In animation, 3-D sometimes refers to shaded, modeled shapes that have an apearance of depth... three-dimensional Image of the Wikimedia Commons logo. The Commons is a free shared repository that you can use with Wikipedia. In common usage, an image (from Latin imago) or picture is an artefact that reproduces the likeness of some subject—usually a physical object or a person. Images may be... image of the internals of an object from a large series of two-dimensional 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... X-ray images taken around a single axis of rotation. The word "tomography" is derived from the The Greek language (Greek Ελληνικά, IPA – Hellenic) is an Indo-European language with a documented history of some 3,000 years. Ancient Greek in its various forms was the language both of classical Greek civilisation and of the origins of Christianity, and... Greek tomos (slice) and graphia (describing).

Although most common in healthcare, CT is also used in other fields, e.g. In nondestructive testing, tests are carried out in such a way as to not disturb the specimen’s structural or surface integrity. This type of testing is valuable because the specimen is not destroyed, however, these techniques generally require greater operator skill and the results are not always straightforward... nondestructive materials testing.

Contents

1 History

2 Principles

3 Diagnostic use

3.1 Cranial CT
3.2 Chest CT
3.3 Cardiac CT
3.4 Abdominal and pelvic CT
3.5 Extremities

4 See also

History

The CT system was invented in 1972 was a leap year that started on a Saturday. Events January January 2 - the Pierre Hotel Heist - Six men rob the safety deposit boxes of the Pierre Hotel in New York City. Loot is at least $4 million January 5 - President of the United States Richard Nixon orders the... 1972 by Sir Godfrey Newbold Hounsfield (28 August 1919 - 12 August 2004) was an English electrical engineer who shared the 1979 Nobel Prize for Physiology or Medicine with Allan McLeod Cormack for his part in developing the diagnostic technique of computerized axial tomography (CAT). His name is immortalised in the Hounsfield scale... Godfrey Newbold Hounsfield of The EMI Group is a major record label, based in the United Kingdom and with operations in over 25 other countries. History The Electric and Musical Industries Ltd formed in March 1931 from a merger of the UK Columbia Graphophone Company and the Gramophone Company/HMV. In 1955, to replace... EMI Central Research Laboratories (now Sensura [1] (http://www.sensaura.com/) owned by Creative Technology Ltd.) using 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... X-rays. Allan McLeod Cormack (February 1924 - May 7, 1998) was a South Africa-born American physicist who shared a part of the 1979 Nobel Prize in Physiology or Medicine for his work on the computerized axial tomography (CAT) scan. Cormack was born in Johannesburg, South Africa. He received his Bachelor of... Allan McLeod Cormack of Tufts University is a university located in Medford, Massachusetts (near Boston). In 1852, Charles Tufts founded Tufts College, and donated the land for the campus on Walnut Hill, the highest point in Medford. Tufts said that he wanted to set a light on the hill. Originally affiliated with the Universalist... Tufts University independently invented the same process and they shared a The Nobel Prizes (pronounced no-BELL or no-bell) are awarded annually to people who have done outstanding research, invented groundbreaking techniques or equipment, or made outstanding contributions to society. It is generally regarded as the supreme commendation in the world today. The prizes were instituted by the final will... Nobel Prize in See drugs, medication, and pharmacology for substances that are used to treat patients. This article is about medical practice. Medicine is a branch of health science concerned with restoring and maintaining health. Broadly, it is the practical science of preventing and curing diseases. However, medicine often refers more specifically to... medicine in 1979 is a common year starting on Monday. Events January January 1 - United States and the Peoples Republic of China establish diplomatic relations January 4 - State of Ohio agrees to pay $675,000 to families of dead and injured in Kent State University shootings. January 7 - Vietnam and Vietnam... 1979 (See also The history of brain imaging, began in the early 1900s with a technique called pneumoencephalography. This process involved draining the cerebrospinal fluid from around the brain and replacing it with air, altering the relative density of the brain and its surroundings, to cause it to show up better on an... history of brain imaging). The first scanner took several hours to acquire the raw data and several days to produce the images. Modern multi-detector CT systems can complete a scan of the chest in less time than it takes for a single breath (useful if the patient cannot hold his/her breath) and display the computed images in a few seconds.

Principles

X-ray slice data is generated using an X-ray source that rotates around the object; X-ray sensors are positioned on the opposite side of the circle from the X-ray source. Many data scans are progressively taken as the object is gradually passed through the gantry.

Newer machines with faster computer systems and newer software strategies can process not only individual cross sections but continuously changing cross sections as the gantry, with the object to be imaged, is slowly and smoothly slid through the X-ray circle. These are called helical or spiral CT machines. Their computer systems integrate the data of the moving individual slices to generate three dimensional volumetric information, in turn viewable from multiple different perspectives on attached CT workstation monitors.

EBT Machine File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. Click on date to download the file or see the image uploaded on that date. (del) (cur) 04:31, 21 Sep 2004 . . MAlvis (5961 bytes) (EBT Machine) File...

EBT Machine

In conventional CT machines, an An X-Ray tube is a vacuum tube designed to produce man made X-Ray photons on demand. The development of X-Ray tubes was an important historical event which enabled the field of radiology, for both imaging and treatment applications. Over decades, the development and usefulness of internal imaging... X-Ray tube is physically rotated behind a circular shroud (see the image above right); in the less used Functional Geometry Electron beam tomography is a specific form of computed axial tomography (CAT or CT) in which the X-Ray tube is not mechanically spun in order to rotate the source of X-Ray photons. This different design was explicitly developed to better image heart structures which never stop... electron beam tomography (EBT) the tube is far larger, note the internal funnel shape in the photo, with a hollow cross-section and only the electron current is rotated.

The data stream representing the varying radiographic intensity sensed reaching the detectors on the opposite side of the circle during each sweep—360 degree in conventional machines, 220 degree in EBT—is then computer processed to calculate cross-sectional estimations of the radiographic density, expressed in The Hounsfield scale is a quantitative scale for describing radiodensity. It was established by Sir Godfrey Newbold Hounsfield, one of the principal engineers and developers of computed axial tomography (CAT, or CT scans). CT machines were the first imaging devices for detailed visualization of the internal three-dimensional anatomy of... Hounsfield units.

CT is used in medicine as a diagnostic tool and as a guide for interventional procedures. Sometimes contrast materials such as An intravenous drip in a hospital Intravenous therapy or IV therapy is the administration of liquid substances directly into a vein. It can be intermittent or continuous; continuous administration is called an intravenous drip. The word intravenous simply means within a vein, but is most commonly used to refer to... intravenous General Name, Symbol, Number iodine, I, 53 Series halogens Group, Period, Block 17 (VIIA), 5 , p Density, Hardness 4940 kg/m3, no data Appearance violet-dark grey, lustrous Atomic properties Atomic weight 126.90447 amu Atomic radius (calc.) 140 (115) pm Covalent radius 133 pm van der Waals radius 198... iodinated contrast is used. This is useful to highlight structures such as blood vessels that otherwise would be difficult to delineate from their surroundings. Using contrast material can also help to obtain functional information about tissues. See See also the main article computed axial tomography for the technical aspects of C(A)T scanning. Since its introduction in the 1970s, computed tomography (CT-scan, CAT-scan) has become an important tool in medical imaging to supplement X-rays and medical ultrasonography. Although it is still quite expensive... diagnostic uses of a CT scan for more detail.

Pixels in an image obtained by CT scanning are displayed in terms of relative Radiodensity is the property of relative transparency to the passage of X-rays through a material. Radiolucent indicates greater transparency to X-Ray photons. Radiodense indicates greater opacity to X-Ray photons. X-Rays are part of the electromagnetic spectrum, with photon energies above visible (and ultraviolet) light photons. They... radiodensity. The pixel itself is displayed according to the mean attenuation of the tissue that it corresponds to on a scale from −1024 to +3071 on the The Hounsfield scale is a quantitative scale for describing radiodensity. It was established by Sir Godfrey Newbold Hounsfield, one of the principal engineers and developers of computed axial tomography (CAT, or CT scans). CT machines were the first imaging devices for detailed visualization of the internal three-dimensional anatomy of... Hounsfield scale. Water has an attenuation of 0 The Hounsfield scale is a quantitative scale for describing radiodensity. It was established by Sir Godfrey Newbold Hounsfield, one of the principal engineers and developers of computed axial tomography (CAT, or CT scans). CT machines were the first imaging devices for detailed visualization of the internal three-dimensional anatomy of... Hounsfield units (HU) while air is −1000 HU, bone is typically +400 HU or greater and metallic implants are usually +1000 HU.

Improvements in CT technology have meant that the overall radiation dose has decreased, scan times have decreased and the ability to reconstruct images (for example, to look at the same location from a different angle) has increased over time. Still, the Radiation generally means the transmission of objects or information from a source into a surrounding medium or destination. Within physics, related concepts are: Ionizing radiation is a stream of particles (photons or other particles) with sufficient energy to cause ionization of atoms or molecules. Non-ionizing radiation does not have... radiation dose from CT scans is several times higher than conventional X-ray scans.

2005 is a common year starting on Saturday of the Gregorian calendar. It has been designated: The World Year Of Physics 2005 The International Year of Microcredit The International Year for Sport and Physical Education Events January Worldwide aid effort continues to develop in response to the 2004 Indian Ocean... Presently, the cost of an average CT scanner was $1.3 million U.S.

Diagnostic use

Since its introduction in the 1970s - Wikipedia /**/ @import /skins/monobook/IE50Fixes.css; @import /skins/monobook/IE55Fixes.css; @import /skins/monobook/IE60Fixes.css; /**/ 1970s From Wikipedia Millennia: 1st millennium - 2nd millennium - 3rd millennium Events and trends Although in the United States and in many other Western societies the 1970s are often seen as a period of... 1970s, CT has become an important tool in Medical imaging is the process by which physicians evaluate an area of the subjects body that is not normally visible. Medical imaging may be clinical, seeking to diagnose and examine disease in specific human patients (see pathology). Alternatively, it may be research-motivated, attempting to understand processes in humans... medical imaging to supplement 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... X-rays and Medical ultrasonography is an ultrasound-based imaging diagnostic technique used to visualize internal organs, their size, structure and their pathological lesions. Uses Ultrasonography is widely utilized in medicine, primarily in gastroenterology, cardiology, gynaecology and obstetrics, urology and endocrinology. It is possible to perform diagnosis or therapeutic procedures with the guidance... medical ultrasonography. Although it is still quite expensive, it is the A gold standard is the best test to determine whether something exists or not. The term gold standard is commonly used in medicine to distinguish the one test that identifies whether an individual has a disease process or not. An ideal gold standard test has a sensitivity of 100% (it... gold standard in the diagnosis of a large number of different disease entities.

Cranial CT

Diagnosis of This article is about stroke as medical term. For other uses of stroke, see stroke (disambiguation) A stroke or cerebrovascular accident (CVA) occurs when the blood supply to a part of the brain is suddenly interrupted by occlusion (an ischemic stroke) or by hemorrhage (a hemorrhagic stroke). The former, ischemia... cerebrovascular accidents and This article needs cleanup. Please edit this article to conform to a higher standard of article quality. There are several types of intracranial hemorrhage, all of them relatively readily diagnosed by CT. First, basic principles: Normal brain tissue has CT numbers of about 30 HU (white matter) to about 40... intracranial hemorrhage is the most frequent reason for a "head CT" or "CT brain". Scanning is done without intravenous contrast agents (contrast may resemble a bleed). CT generally does not exclude In medicine, infarction is necrosis of tissue due to upstream obstruction of its arterial blood supply. It is the culmination of ischemia. Although infarction can affect any organ in the context of a number of disease states, it is most closely associated with atherosclerosis. When an atherosclerotic plaque ruptures, a... infarct in the acute stage, but is useful to exclude a bleed (so An anticoagulant is a substance that prevents coagulation; that is, it stops blood from clotting. A group of pharmaceuticals called anticoagulants can be used in vivo as a medication for thrombotic disorders. Some chemical compounds are used in medical equipment, such as test tubes, blood transfusion bags, and renal dialysis... anticoagulant medication can be commenced safely).

For detection of Tumor (American English) or tumour (British English) originally means swelling, and is sometimes still used with that meaning. Tumor meaning swelling is one of the five classical characteristics of inflammation. However, the term is now primarily used to denote abnormal growth of tissue. This growth can be either malignant or... tumors, CT scanning with IV contrast is occasionally used but is less sensitive than MRI Image Magnetic resonance imaging (MRI) is a method of creating images of the inside of opaque organs in living organisms as well as detecting the amount of bound water in geological structures. It is primarily used to visualise pathological or other physiological alterations of living tissues and it is... magnetic resonance imaging (MRI).

CT can also be used to detect increases in Intracranial pressure is the pressure of the cerebrospinal fluid within the central nervous system. It is measured in millimeters of water (mm H20). Normal pressure is between 60 mm H20 and 150 mm H20. Intracranial pressure can be measured by means of a lumbar puncture. There are many symptoms associated... intracranial pressure, e.g. before In medicine, a lumbar puncture (colloquially known as a spinal tap) is a diagnostic procedure that is done to collect a sample of cerebrospinal fluid (CSF) for biochemical, microbiological and cytological analysis. Indications The most common indication for a lumbar puncture is to collect cerebrospinal fluid in a case of... lumbar puncture or to evaluate the functioning of a ventriculoperitoneal shunt.

CT is also useful in the setting of trauma for evaluating facial and skull fractures.

Chest CT

CT is excellent for detecting both acute and chronic changes in the The heart and lungs (from an older edition of Grays Anatomy) The lung is an organ belonging to the respiratory system and interfacing to the circulatory system of air-breathing vertebrates. Its function is to exchange oxygen from air with carbon dioxide from blood. The process in which this... lung parenchyma. For detection of airspace disease (such as Pneumonia (the ancient Greek word for lungs) is defined as an infection involving the alveoli of the lungs. It occurs in patients of all age groups, but young children and the elderly, as well as immunocompromised and immune deficient patients, are especially at risk. Causal therapy is with antibiotics. Signs... pneumonia) or Lung cancer is a malignant tumour of the lungs. Most commonly it is bronchogenic carcinoma (about 90%). Lung cancer is the most lethal malignant tumour worldwide, causing up to 3 million deaths. The incidence of lung cancer is highly correlated with smoking. Exposure to carcinogens, such as those present in... cancer, ordinary non-contrast scans are adequate.

For evaluation of chronic interstitial processes ( Emphysema is a chronic lung disease. It is often caused by exposure to toxic chemicals or long-term exposure to tobacco smoke. Signs and symptoms Emphysema is characterised by loss of elasticity of the lung tissue; destruction of structures supporting the alveoli; and destruction of capillaries feeding the alveoli. The... emphysema, Fibrosis is the formation or development of excess fibrous connective tissue in an organ or tissue as a reparative or reactive process, as opposed to formation of fibrous tissue as a normal constituent of an organ or tissue. Diseases: cystic fibrosis of the pancreas, fibrocystic disease of the pancreas, mucoviscidosis... fibrosis, and so forth), thin sections with high spatial frequency reconstructions are used. For evaluation of the The mediastinum is a non-delineated group of structures in the thorax (chest), surrounded by loose connective tissue. Anatomy It is surrounded by the chest wall anteriorly, the lungs laterally and the spine posteriorly. It is continuous with the loose connective tissue of the neck, and extends inferiorly onto the... mediastinum and hilar regions for Lymphadenopathy is seen in infection (e.g. bacterial or viral) lymphoma cat-scratch disease See also Sign (medicine) Categories: Stub ... lymphadenopathy, IV contrast is administered.

CT angiography of the chest (CTPA) is also becoming the primary method for detecting A pulmonary embolism occurs when a blood clot, generally a venous thrombus, becomes dislodged from its site of formation and embolizes to the arterial blood supply of one of the lungs. Symptoms may include difficulty breathing, pain during breathing, and more rarely circulatory instability and death. Treatment is with anticoagulant... pulmonary embolism (PE) and Aortic dissection is a tear of the aorta (the largest artery of the body). This tear causes blood to flow between the layers of the wall of the aorta and dissects the layers apart. Aortic dissection is an extremely serious medical emergency and can quickly lead to death. Overview As... aortic dissection, and requires accurately timed rapid injections of contrast and high-speed helical scanners. CT is the standard method of evaluating abnormalities seen on chest 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... X-ray and of following findings of uncertain acute significance.

Cardiac CT

With the advent of subsecond rotation combined with multi-slice CT (up to 64 slices), high resolution and high speed can be obtained at the same time, allowing excellent imaging of the coronary arteries.

Abdominal and pelvic CT

Many The abdomen (from the Latin word meaning belly) is the part of the body between the pelvis and the thorax. The front of the abdomen is the abdominal cavity, which is separated from the thoracic cavity by the diaphragm. The lining of the abdomen is called the peritoneum, and the... abdominal disease processes require CT for proper diagnosis. The most common uses include diagnosis of Kidney stones are solid accretions (crystals) of dissolved minerals in urine found inside the kidneys or ureters. Also known as nephrolithiasis, urolithiasis or renal calculi. They vary in size from as small as a grain of sand to as large as a golf ball. Kidney stones typically leave the body... renal/urinary stones, Appendicitis is a condition characterised by inflammation of the appendix. While mild cases may resolve without treatment, many require laparotomy with removal of the inflamed appendix. Untreated, mortality is high, mainly due to peritonitis and shock when the inflamed appendix ruptures. Causes It is possible for matter to become lodged... appendicitis, Pancreatitis is inflammation of the pancreas. There are two forms, which are different in causes and symptoms, and require different treatment: Acute pancreatitis Chronic pancreatitis This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. If an article link referred... pancreatitis, Diverticulitis is inflammation of a diverticulum, usually of the large colon. Contents // Categories: Medicine stubs ... diverticulitis, This article is in need of attention. Please see its listing on Pages needing attention and improve it in any way you see fit. When the issues regarding this page have been resolved, remove this notice and the listing, but please do not remove this notice until the article has... abdominal aortic aneurysm, and Bowel obstruction is mechanical blockage of the intestines, preventing the normal transit of the products of digestion. It can occur at any level in the digestive tract, and is a medical emergency. Although many cases are not treated surgically, it is a surgical problem. Causes Small bowel obstruction Causes of... bowel obstruction. CT is also the first line for detecting solid organ injury after trauma. Oral and/or rectal contrast is usually administered (more often iodinated contrast is an intervenous radiographic die containing iodine, which enhances vascular structures and organs. Some pathologies, such as cancer, are particularly improved with iodianted constrast. ... iodinated contrast than Barium is also the Latin name for the city Bari in Italy. General Name, Symbol, Number Barium, Ba, 56 Series alkaline earth metals Group, Period, Block 2(IIA), 6, s Density, Hardness 3510 kg/m3, 1.25 Appearance silvery white Atomic Properties Atomic weight 137.327 amu Atomic radius (Calc... barium due to the tendency of barium to cause imaging artifacts that limit evaluation of abdominal structures).

CT has limited application in the evaluation of the Human male pelvis, viewed from front Human female pelvis, viewed from front The pelvis is the bony structure located at the base of the spine (properly known as the caudal end). The pelvis incorporates the socket portion of the hip joint for each leg (in bipeds) or hind leg (in... pelvis. For the female pelvis in particular, Medical ultrasonography is an ultrasound-based imaging diagnostic technique used to visualize internal organs, their size, structure and their pathological lesions. Uses Ultrasonography is widely utilized in medicine, primarily in gastroenterology, cardiology, gynaecology and obstetrics, urology and endocrinology. It is possible to perform diagnosis or therapeutic procedures with the guidance... ultrasound is the imaging modality of choice.

Extremities

CT is often used to image complex A fractured bone in a living person is treated by immobilization with a plaster or fiberglass cast, and in some cases surgical nails, screws, plates and wires to supplement a cast. By allowing only limited movement, fixation helps preserve anatomical alignment while enabling callus formation, towards the target of achieving... fractures, especially ones around joints, because of the ability to reconstruct the area of interest in multiple planes.

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