CT Glosssary Flashcards
1
Q
The reformatting of cross-sectional images to produce images of the surfaces of anatomical structures
A
3D Surface Rendering
2
Q
A mechanism of attenuation in which x-ray photons interact with the patient’s tissues and never leave the body
A
Absorption
3
Q
A hardware component used to increase the strength of a signal
A
Amplifier
4
Q
Information expressed in a continuous fashion
A
Analog
5
Q
The component that converts the analog data into digital information to be temporarily stored in the raw data file
A
Analog-to-Digital Converter (ADCs)
6
Q
The positive terminal of the CT x-ray tube and the part of the tube where the target material is located
A
Anode
7
Q
Saving the patient’s digital images on a long-term storage device
A
Archiving
8
Q
A specialized computer component used to reconstruct the CT images
A
Array Processor
9
Q
Annoying anomalies which sometimes appear in CT images
A
Artifacts
10
Q
A reduction in the number of photons in the x-ray beam as it passes through the tissues in the patient’s body
A
Attenuation
11
Q
A calculation used for reconstructing the final CT images from the raw data by adding together the attenuation information collected from all of the projections
A
Back Projection
12
Q
A type of oral contrast agent known for providing very good opacification of the bowel, but is slower moving through the GI tract compared to iodinated agents
A
Barium Sulfate Oral Contrast Agent
13
Q
The increase in the average energy of the x-ray beam as it penetrates tissues
A
Beam Hardening
14
Q
Refers to the timing immediately following an IV contrast injection defined by at least a 30 HU difference between the abdominal aorta and the inferior vena cava
A
Bolus Phase of Enhancement
15
Q
X-rays produced as a result of an electron colliding with or passing near the nucleus of an atom in the target
A
Bremsstrahlung (braking radiation)
16
Q
The negative terminal of the CT x-ray tube and the part of the tube where the negatively charged electrons flow into the tube from the high voltage generator
A
Cathode
17
Q
X-rays produced as a result of an electron in the target replacing one ejected by a fast-moving incoming electron
A
Characteristic Radiation
18
Q
Components on the CT scanner that restrict the path of the x-ray photons
A
Collimator
19
Q
An x-ray tomographic technique which uses computers to reconstruct the images
A
Computed Tomography
20
Q
A calculation used for reconstructing the final images from the raw data used on multi-row detector scanners with the capability of collecting more than four slices in a single rotation
A
Cone Beam Reconstruction
21
Q
Having no gaps between adjacent slices
A
Contiguous
22
Q
Conditions that would preclude a patient from having a CT study performed in a given manner (i.e. with contrast)
A
Contraindications
23
Q
The ability to differentiate small differences in density on the image
A
Contrast
24
Q
A compound, usually pharmaceutical in nature, which when administered to a patient, may improve the sensitivity and specificity of the clinical diagnosis
A
Contrast Agent
25
A study of cross-sectional images characterized by an increment of the patient table after each x-ray tube rotation
Conventional Scan
26
The process of applying a reconstruction filter to the raw data
Convolution
27
Aligned perpendicular to the axis which travels from anterior to posterior in the patient
Coronal
28
Sections made by cutting anything at right angles to any axis
Cross-sections
29
A number that correlates to the Hounsfield scale which ranks various materials by their attenuation properties
CT Number
30
A study which uses IV contrast media to visualize vascular structures
CT Angiography (CTA)
31
Indicator of radiation dose which includes the radiation located within the intended slice thickness as well as that from the penumbra
CT Dose Index (CTDI)
32
A CT hardware component which measures the x-rays that pass through the patient's body
Detector
33
A group of detectors
Detector Array
34
The standard used for communicating digital medical image information, which was established to improve workflow efficiency between imaging systems in healthcare environments worldwide
Digital Imaging and Communications in Medicine (DICOM)
35
Information expressed in terms of discrete numbers
Digital
36
The components that convert the digital commands coming out of the scan controller into analog commands that can then be executed by the power-producing and mechanical components
Digital-to-Analog Converters (DACs)
37
A filter applied to the digital image data to further sharpen or smooth the appearance of the tissues
Display Filter
38
The amount of ionizing radiation absorbed by an object per unit mass
Dose
39
The best indicator of radiation dose reflecting the total energy from a CT scan absorbed by the patient
Dose Length Product (DLP)
40
A calculated sum of the absorbed dose of all of the tissues in the body, each individually multiplied by a weighting factor for that organ or region
Effective Dose
41
Stationary metal contacts through which electrical signals are transferred to and from the rotating slip ring
Electrical Brushes
42
A CT scanner that has no x-ray tube with fast scan time making it well-suited for cardiac and coronary artery imaging.
Electron Beam CT Scanner (EBCT)
43
Refers to the timing usually a few minutes after an IV contract injection defined by less than a 10 HU difference between the abdominal aorta and the inferior vena cava
Equilibrium Phase of Enhancement
44
The condition that occurs when the substance being injected misses the vein and instead goes directly into the soft tissue
Extravasation
45
An x-ray beam having a shape similar to an opened paper fan
Fan Beam
46
A structure on the cathode terminal of the CT x-ray tube from which the electron beam is released
Filament
47
The area on the anode target bombarded by the electron beam and a factor in determining the image resolution
Focal Spot
48
The comparison of two imaging modalities yielding co-registered images
Fusion Imaging
49
The part of a CT scanner through which the patient table is advanced and the component that contains the CT x-ray tube and the detectors
Gantry
50
A unit for measuring the absorbed radiation dose in which 1 Gy equals 100 rads
Gray (Gy)
51
A continuous spectrum of shades of the color gray used to differentiate structures on a digital image
Gray Scale
52
A study of cross-sectional images characterized by continuous patient table motion during x-ray tube rotation
Helical Scan
53
The component that creates the high voltage that enables the CT x-ray tube to produce x-ray photons
High Voltage Generator
54
The communications coordinator for the rest of the CT system
Host Computer
55
The grid of rows and columns of pixels which forms the digital image
Image Matrix
56
Compounds that are injected through the theca of the spinal cord into the subarachnoid space during a myelographic study of the spine
Intrathecal Contrast Agents
57
Compounds, typically containing iodine, that are injected into the blood stream in order to better differentiate tissues and better delineate abnormalities on CT images
Intravenous (IV) Contrast Agents
58
A type of oral contrast agent known for moving through the GI tract quickly compared to barium sulfate agents
Iodinated Oral Contrast Agent
59
A type of IV contrast agent that breaks down in the blood stream
Ionic Contrast Agent
60
A type of energy that can cause detrimental changes to occur in the atoms of living tissues
Ionizing Radiation
61
A complex cycle of correction calculations which may be applied during the CT image reconstruction process to reduce image noise, and which allows a greatly reduce dose to be used without compromising image quality
Iterative Reconstruction
62
The scan parameter which is the maximum energy of the x-ray photons and the parameter that controls the contrast in a CT image
kVp
63
A single projection scan obtained with a stationary x-ray tube and a moving patient table generating the image used to position the cross-sectional slices
Localizer Scan
64
The scan parameter which is the mathematical product of the tube current and the rotation time (in sec.) and which determines the number of photons the patient's body is exposed to
mAs
65
The post-processing algorithm used on CTA and MRA data to allow visualization of the complete vascular tree
Maximum Intensity Projection (MIP)
66
Streaks that result from metal located within the scan field-of-view during a CT scan
Metal Artifact
67
Streaks, blurriness, or ghosting that results from motion of any structure in or on the patient's body during a CT scan
Motion Artifact
68
An indicator of radiation dose which corrects the CTDI on conventional scans by factoring in gaps or overlaps between the slices as indicated by the selected table increment
Multiple Slice Average Dose (MSAD)
69
The reformatting of images acquired in one orientation to produce images in other orientations
Multiplanar Reconstruction
70
A CT scanner design that collects information from multiple anatomical slices in each rotation of the x-ray tube
Multi-row Detector CT Scanner (MDCT)
71
A condition in an image that refers to electronic interference and which causes the appearance to be grainy
Noise
72
Refers to the timing shortly after an IV contrast injection defined by a 10-30 HU difference between the abdominal aorta and the inferior vena cava
Non-equilibrium Phase of Entertainment
73
Type of IV contrast that does not break down in the blood stream
Non-Ionic Contrast Agent
74
The link between the technologist and the computerized electronic environment of the CT scanner hardware
Operator's Console
75
Compounds containing iodine or barium sulfate that are swallowed or administered rectally in order to opacify the gastrointestinal tract on CT images
Oral Contrast Agents
76
The concentration of molecular particles in the contrast agent solution
Osmolality
77
Results from selecting slices that are much thicker than the anatomy and pathology which we want to visualize
Partial Volume Artifact
78
Results in blurring of the images and a decreased ability to visualize small structures when the slices are too thick
Partial Voluming
79
A thin, focused beam of x-rays
Pencil Beam
80
A tiny bit of energy contributing to the x-ray beam which travels at the speed of light
Photon
81
The distribution, viewing and storage facility for digital images across an imaging facility's computer network
Picture Archiving and Communication System (PACS)
82
The extent to which the x-ray helix is stretched during a helical scan
Pitch
83
A single picture element formed by the intersection of a row and column of the image grid
Pixel
84
A restriction on unwanted x-rays entering the detector assembly from arbitrary angles
Post-patient Collimation
85
Conditions that would warrant a medical decision as to whether the benefits of the exam outweigh the risks posted to the patient
Precautions
86
A refinement of the thickness of the x-ray beam after it leaves the x-ray tube and before it enters the patient's body
Pre-patient Collimation
87
A view of the anatomical cross-section along the path of the x-ray beam from only one vantage point
Projection
88
Position with the posterior side of the body facing up
Prone
89
A pre-defined set of parameters that is used to run a CT scan for a specific clinical application
Protocol
90
A unit for measuring the absorbed radiation dose
Rad
91
Radiation that extends outside of the intended slice caused by imperfect collimation of the x-ray beam
Radiation Penumbra
92
The measured x-ray photon information
Raw Data
93
The number of millimeters of information reconstructed and displayed in the final image
Reconstruction Field-of-View (FOV)
94
The filter applied to the raw data during image reconstruction
Reconstruction Filter
95
The parameter that determines where helical slices will be reconstructed and if they will be overlapped
Reconstruction Interval
96
A unit for measuring the radiation dose equivalent
Rem (1 rem = 1 rad)
97
A measurement of the smallest structure that we can visualize, or resolve, in the image
Resolution
98
The process of reconstructing images from the raw data using modified parameters, after the initial image reconstruction is complete
Retrospective Reconstruction
99
Aligned perpendicular to the axis which travels from left to right in the patient
Sagittal
100
The collection of anatomical information during the time the x-ray beam is on
Scan
101
The component responsible for the timing and correct performance of each CT system component once the scan has been started
Scan Controller
102
The number of millimeters of anatomy over which projection data is collected
Scan Field-of-View (FOV)
103
A mechanism of attenuation in which x-ray photons interact with a dense structure and change the direction of their path
Scattering
104
The process of determining the patient's current condition and medical history in order to ensure eligibility for the scanning procedure
Screening
105
The number of millimeters of anatomy, intersected by the thickness of the x-ray beam, which is represented in the CT image
Slice Thickness
106
A large rotating ring on the CT scanner to which several hardware components are mounted and which eliminates the need for power and data cables
Slip Ring
107
Positioned with the anterior side of the body face up
Supine
108
The advancement, in millimeters, of the patient table between consecutive conventional slices determining the gaps or overlap between adjacent slices
Table Increment
109
The material in the CT tube which is bombarded with fast-moving electrons to generate x-rays
Target
110
Any imaging method in which the patient's tissues are visualized by "cutting" them into sections
Tomography
111
Aligned perpendicular to the axis which travels from head to foot in the patient
Transverse
112
The parameter that determines the number of x-ray photons produced by the CT x-ray tube
Tube Current (mA)
113
The parameter that determines the energy level of x-ray photons produced by the CT x-ray tube
Tube Voltage (kV)
114
The thickness of a substance in reference to contrast media
Viscosity
115
The center CT number around which the window width is positioned
Window Level
116
The range of CT numbers that occupy the full gray scale on the image monitor
Window Width
117
Adjusting the brightness and contrast of the shades of gray assigned to represent the tissues in the pixels of a CT image
Windowing
118
The source of x-rays in a CT scanner
CT X-ray Tube
