Mosbys Terms Flashcards
180-degree linear interpolation (180LI)
Type of algorithm used for multi slice computed tomography image reconstruction in which data acquired from a shorter distance (180*) away from the reconstructed slice location are interpolated
360-degree linear interpolation (360LI)
Type of algorithm used for MSCT image reconstruction in which two sets of projection data acquired 360 degrees apart are used to form an image at a precise z-axis location
Absorbed dose
Amount of X-ray energy absorbed in a unit of mass and measured in grays (Gy)
Absorption efficiency
Ability of an individual ct detector to absorb and measure the transmitted X-ray intensity incident upon it. Primarily controlled by characteristics and physical makeup of the detector material
Adaptive array
Type of MSCT detector array configured with the thinnest detectors at the center, surrounded by detectors of incrementally increasing widths along the z-axis
Advanced single-slice rebinning algorithm
Cone beam correction algorithm utilized to overcome potential attenuation calculation errors from the divergent beam of MSCT
Afterglow
Tendency of a scintillation-type ct detector to continue to glow in response to X-ray after exposure source has been terminated
Agatston score
Quantification of volume and density of calcium within the coronary arteries. Calculated for a coronary artery calcification study to indicate a patient’s risk of suffering a cardiac event
ALARA
Acronym for as low as reasonably achievable, cardinal principle of radiation dose reduction for all radiologic procedures
Algorithm
Mathematical filter applied to raw data during ct image reconstruction to remove blurring artifact inherent to back-projection. Also referred to as a kernel
Aliasing
Form of streak artifact caused by insufficient number of views/data samples obtained during data acquisition
Analog to digital converter
Component of DAS responsible for converting electrical signal emitted by ct detectors into digital form
Archival
Storage of ct data in either hard film or soft digital form
Array processor
Component of ct computer system responsible for receiving raw scan data, performing all of the major processing of the ct image, and returning the reconstructed image to the storage memory of the host computer.
Arterial phase
Period of peak enhancement after the bolus IV administration of iodinated contrast material.
Artifact
Form of noise on ct image resulting from errors during the measurement of transmitted radiation by the detectors
Ataxia
Neurological sign characterized by a loss of muscular coordination
Attenuation
Reduction in intensity of a radiation beam as it passes through a substance
Attenuation coefficient
Value assigned to an object quantifying its ability to attenuate along the scan acquisition range to reduce patient radiation dose to a minimum
ATCM
Ct system software used to adjust mA throughout an acquisition to reduce patient radiation dose to a minimum
ATVS
Ct system software used to adjust tube voltage (kvp) based upon the changing patient attenuation along the scan acquisition range to reduce patient radiation dose to a minimum
Back-projection
Mathematical process of CT image reconstruction whereby ray sum data are projected back into a matrix
Beam hardening
Phenomenon whereby low-energy photons are absorbed as the X-ray beam passes through an object, resulting in an increase in average photon energy of beam
Beam pitch
Ratio of table feed per gantry rotation to the total collimation used during acquisition with an MSCT system