Computed Tomography For Technologist Flashcards
(159 cards)
Main advantages of CT over conventional radiography are
☑️elimination of superimposed structures
☑️ability to differentiate small differences of anatomic structures and abnormalities
☑️superior quality of the images
____________ describes the ability of a system to define small objects distinctly.
Spatial Resolution
_________ refers to the ability of a system to differentiate, on the image, objects with similar densities.
Low-contrast resolution
Refers to the speed that the data acquired.this speed is particularly important to reduce or eliminate artifacts that result from object motion, such as those commonly seen when imaging the heart.
Temporal Resolution
The thickness of the cross sectional slice is referred to as its ______
Z Axis
Is the grid formed from the rows and columns of pixels.
Matrix
The number of photons that interact depends on the:
☑️thickness
☑️density
☑️atomic number of the object
Defined as the mass of a substance per unit volume and a degree which matter is crowded together, or concentrated
Density
The relative number of photons interact _________ with the increased density, thickness and atomic number of the object.
Increases
The degree to which an xray beam is reduced by an object is referred to as
Attenuation
The amount of the xray beam that is scattered or absorbed per unit thickness of the absorber is expressed by the ________
Linear Attenuation Coefficient
Quantify the degree that a structure attenuates the xray beam.
Hounsfield Units
Hounsfield Number for air
-1000
Hounsfield number for bone
+1000
Factors that contribute to an inaccurate Hounsfield measurement include
☑️poor equipment calibration
☑️image artifacts
☑️volume averaging
All xray beam sources for CT and conventional radiography produce xray energy that is _________which xray beam comprises photons with varying energies
Polychromatic
Appear as dark streaks or vague areas of decreased density sometimes called cupping artifacts.
Beam-hardening artifacts
The process in CT by which different tissue attenuation values are averaged to produce one less accurate pixel reading is called
Volume Averaging or Partial Volume Effect
The reconstruction that is automatically produced during scanning is often called
prospective reconstruction.
Brain of CT scanner
CPU
The CT process can be broken down into three main segments:
Data Acquisition → Get Data Image Reconstruction → Use Data Image Display → Display Data
The Hounsfield unit value is ________ related to linear attenuation coefficient. _____ HU equals a 0.1percent difference bet the LAC of the tissue as compared with the LAC of water.
Directly
1
Use a brush-like apparatus to provide continuous electrical power and electronic communication across a rotating surface.
Permits the gantry frame to rotate continuously, eliminating the need to straighten twisted system cables.
Slip Rings
________ is used to increase the intensity raeof the beam, increasing its penetrating ability and thereby reducing patient dose. Help also to reduce the heat load on the xray tube by allowing a lower mA setting
High KV