:: ct abbreviations

A glossary of abbreviation and acronyms you may have seen on the ImPACT web site, or in relation to CT scanning. Let us know if there are any you think we have missed out, or if you think any term could be explained better!

American Association of Physicists in Medicine Link
As Low As Reasonably Achievable: principle used in radation protection relating to doses to people which should always be as low as possible, after all 'reasonable' methods of reduction have been applied.
Anterio-Posterior: from the front (anterior) towards the back (posterior) of a patient. Common orientation for radiographic images.
The British Institute of Radiology. Link
Computed (or Computerised) Axial Tomography (aka CT): an imaging technique that uses views of an object from many directions to synthesise a transaxial or cross sectional image.
The Centre for Evidence-based Purchasing; part of NHS PASA. More
Computed (or Computerised) Tomography (aka CAT): An imaging technique that uses views of an object from many directions to synthesise a transaxial or cross sectional image.
Computed Tomography Dose Index: a term used in radiation dosimetry that describes the dose from a single rotation of a CT scanner. There are a number of definitions of CTDI commonly used - see the following presentation for more details: Link
Data Acquisition System: the part of a CT scanner that connects the detectors of a CT scanner to the computer, processing and measuring their output.
Digital Imaging and Communication in Medicine: a standard for communicating medical image information between a wide range of imaging equipment.
Dose-Length Product: a basic measure of radiation risk calculated by multiplying the CTDI for a scan sequence by the length of coverage in the z-direction (along the patient's length).
Electron Beam Computed Tomography: type of CT scanner that does not need a rotating x-ray tube to produce x-rays. Used for specialist purposes, particularly cardiac imaging.
ElectroCardioGram: graph of electrical activity in the heart over time.
Edge Spread Function: the response of an imaging system to a step function.
Food and Drug Administration: US body responsible for legislation relating to medical equipment. Link
Focus to Detector Distance: the distance between the x-ray tube focal spot and the x-ray detectors.
Focus to Isocentre Distance: distance from x-ray tube focus to the scan isocentre (the centre of rotation of the CT gantry).
Field Of View (See also SFOV and RFOV): size of an area being imaged.
Full Width at Half Maximum: method for characterising the width of a peak on a graph.
Geometric Efficiency: the ratio of the imaged to irradiated slice widths. Also a well known CT scanner manufacturer!
Hospital Information System. Hospital-wide computer system containing patient details and records.
Hounsfield Unit. The CT scanner display unit. The arbitrary scale is defined by air, which has a CT number of -1000 HU, and water, with a CT number of 0 HU. Named after Sir Godfrey Hounsfield, who developed the first clinical CT scanner. Link
International Electrotechnical Commission. Link
Imaging Performance Assessment of CT scanners. The UK's CT scanner evaluation group. Link
Institute of Physics and Engineering in Medicine. Link
Low Contrast (Detail) Detectablility. The ability of imaging equipment to distinguish between objects that have similar properties. For CT, the ability to distinguish between objects that have similar x-ray attenuation coefficients.
Low Contrast Resolution (aka LCD).
Linear Interpolator. In spiral scanning, a method for estimating the scan data at a particular position along the patient's length using meaured data points on either side. See the following presentation for more details: Link
Medical Devices Agency. The UK agency former responsible for ensuring medical devices meet appropriate standards of safety, quality and performance. This body has since been superseded by the MHRA.
Multi-Detector Computed Tomography (aka MSCT). CT performed with more than one row (or bank) of detectors along the patient's length, capable of producing more than one image simulateously.
Medicines and Healthcare products Regulatory Agency. The MHRA was created on 1 April 2003 from the merger of the Medical Devices Agency and the Medicines Control Agency. MHRA is an executive agency of the Department of Health. Further details available here: Link
Minimum Intensity Projection. Similar to MIP, but used to display low density objects. See MIP.
Maximum Intensity Projection. Pseudo-3D visualisation technique for viewing volumes of data, where the CT number of each pixel is given by the maximum CT number through the volume.
Multiple Scan Average Dose. The mean dose to an exposed region of a patient from a CT scan sequence.
Multi-Slice Computed Tomography (aka MDCT). CT performed with more than one row (or bank) of detectors along the patient's length, capable of producing more than one image simultaneously.
Modulation Transfer Function. A description of the ability of imaging equipment to reproduce spatial detail in an object. See this presentation for more details: Link
National Health Service. The UK's public health body, responsible for providing healthcare for all UK subjects. Link
The NHSnet is similar to the Internet but is only accessible to computers within the UK's National Health Service. ImPACT have an NHSnet website. Link
National Radiological Protection Board. Link
Picture archiving and communications system. Electronic means to store and distribute medical images (rather than conventional x-ray film).
The NHS Purchasing And Supply Agency. Link
Point Spread Function. The response of an imaging system to a point or impulse input.
The Royal College of Radiologists. Link
Reconstruction Field Of View. Size of the SFOV that is reconstructed to form a CT image.
Radiology Information System. Radiology department computer system containing patient details and records.
Region Of Interest. A user defined area of an image that can used for purposes such as calculation of pixel statistics.
Radiological Society of North America. Link
Service Class Provider. A piece of equipment offering a DICOM service class for other equipment to use.
Service Class User. A piece of equipment using a DICOM service class provided by another piece of equipment.
Standard Deviation. Statistical measure of variation of a series of values around the mean. Used to characterise noise in CT images.
Scan Field Of View. Size of area being imaged (scanned).
Scan Projection Radiograph. Scan acquired using a static tube and moving bed that is used to plan scan sequences. Variously known as topogram, scout view, scanogram, surview or pilot scan on different scanners.
Surface Shaded Display. Method of displaying 3-D volumes achieved by finding 'surfaces' at the boundaries of organs, vessels etc, and displaying them as solid objects.
Volume Rendered Image. Method for displaying 3-D image data, that assigns colours and degrees of transparency to different CT number ranges. Good for displaying overlapping structure.