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C5 > COMPUTED TOMOGRAPHY > Flashcards

COMPUTED TOMOGRAPHY Flashcards

1
Q

A scan of air in the gantry used to calibrate the scanner based on air density.

A

air calibration

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2
Q

Define “algorithm” in the context of CT imaging.

A

A mathematical formula for enhancing image features like soft tissue and edges.

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3
Q

Resolution where voxel dimensions differ along three axes.

A

anisotropic spatial resolution

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4
Q

What does “aperture” mean in a CT scanner?

A

The opening in the gantry where the patient passes during the scan.

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5
Q

Storing CT images on long-term devices like tapes or disks.

A

archiving

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6
Q

An image distortion unrelated to the subject being scanned.

A

artifact

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7
Q

What is “attenuation” in CT imaging?

A

The reduction of x-ray intensity by tissue density, resulting in CT numbers.

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8
Q

What plane does “axial” refer to in CT imaging?

A

The transverse plane.

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9
Q

What is a “bolus” in CT imaging?

A

Rapid IV injection of contrast media to enhance vascular imaging.

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10
Q

Rows of detector assemblies in the scanner.

A

channel

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11
Q

What is Computed Tomography (CT)?

A

A rotating x-ray tube and detector assembly creating cross-sectional images.

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12
Q

Volumetric imaging to construct 3D images of vascular structures.

A

CT angiography

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13
Q

How are CT numbers related to tissue density?

A

Higher CT numbers indicate denser tissues, and lower numbers indicate less dense tissues.

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14
Q

What is the CT number assigned to water?

A

0

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15
Q

What is the purpose of curved planar reformations in CT?

A

To create images in irregular or oblique planes using post-processing.

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16
Q

Converts analog signals to digital signals for CT image computation.

A

Data Acquisition System (DAS)

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17
Q

What materials are CT detectors commonly made of?

A

High-density photo-reactive crystals or pressurized stable gases.

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18
Q

A dose descriptor summarizing the radiation exposure over a scanned length.

A

dose-length product (DLP)

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19
Q

What is “dynamic scanning” in CT imaging?

A

Continuous raw data collection for later reconstruction, often used for high-flow vascular imaging.

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20
Q

What is the field of view (FOV) in CT?

A

The anatomical area displayed on the monitor, adjustable as needed.

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21
Q

What does the gantry in a CT scanner house?

A

X-ray tube, cooling system, detector assembly, and DAS.

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22
Q

What are the primary benefits of helical CT scanning?

A

Faster imaging with a continuous spiral data path and improved 3D reformation.

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23
Q

What are Hounsfield Units (HU)?

A

Numerical values indicating tissue density in a CT scan.

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24
Q

What is “image misregistration”?

A

Distortion caused by table movement or patient respiration during scans.

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25
Q

What is isotropic spatial resolution?

A

Voxel dimensions are equal along all three axes.

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26
Q

What is the CT matrix composed of?

A

Rows and columns of individual pixels containing numerical CT values.

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27
Q

What is the purpose of a Maximum Intensity Projection (MIP)?

A

To construct 3D images by displaying the brightest pixels from image stacks.

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28
Q

What is noise in a CT image?

A

Random CT number variations creating a grainy appearance.

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29
Q

Weighted averaging of densities in a voxel with multiple tissue types.

A

partial volume averaging

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30
Q

A single cell in the image matrix, representing a part of the scanned tissue.

A

pixel

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31
Q

A set of instructions for performing a CT scan, including slice thickness and table increments.

A

protocol

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32
Q

Noise from random variations in the number of detected x-ray photons.

A

quantum noise

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33
Q

Creating a digital image from raw scan data.

A

reconstruction

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34
Q

A specific area selected for analyzing tissue density.

A

region of interest” (ROI)

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35
Q

An electrical component allowing continuous gantry rotation.

A

slip ring

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36
Q

The ability to distinguish small, high-contrast objects in an image.

A

spatial resolution

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37
Q

What is the function of post-processing techniques in CT?

A

Enhancing images by applying special reconstruction algorithms.

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38
Q

The ability to capture motion within the shortest imaging time.

A

temporal resolution

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39
Q

What is the primary component of the CT imaging matrix?

A

A grid of pixels organized into rows and columns.

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40
Q

The CT number used to define structures in 3D reconstructions.

A

threshold value

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41
Q

What does voxel stand for?

A

Volume element, combining pixel area with slice thickness.

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42
Q

It controls the range of gray levels, affecting contrast.

A

window width

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43
Q

What is the historical significance of Godfrey Hounsfield?

A

He developed the first clinically viable CT scanner in 1970.

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44
Q

What are the key advantages of multi-detector CT (MDCT)?

A

Faster imaging, reduced motion artifacts, and better contrast resolution.

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45
Q

An increase in x-ray beam energy as it passes through denser objects.

A

beam hardening

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46
Q

What causes ring artifacts in third-generation CT scanners?

A

Faulty or out-of-calibration detectors.

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47
Q

They restrict the x-ray beam, reducing patient dose and improving contrast.

A

collimators

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48
Q

Generation of CT Scan that eliminates ring artifacts due to stationary detectors.

A

fourth-generation

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49
Q

What is a major limitation of fifth-generation CT scanners?

A

High cost and limited availability.

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50
Q

The ratio of table movement per gantry rotation to the beam width.

A

pitch

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51
Q

What is the primary feature of sixth-generation CT scanners?

A

Continuous gantry rotation with slip ring technology for helical scans.

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52
Q

What distinguishes seventh-generation CT scanners?

A

They use multiple detector arrays, such as 64-slice configurations.

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53
Q

What are the main components of a CT scanner?

A

Gantry, operating console, and computer.

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54
Q

What materials are used for CT patient couches?

A

Low atomic number materials like carbon fiber.

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55
Q

What is the function of pre-patient collimators?

A

They limit the area of the patient exposed to the x-ray beam.

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56
Q

They equalize radiation intensity across the detector array.

A

bow-tie filter

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57
Q

What are common scan planes in CT?

A

Axial, coronal, sagittal, and oblique planes.

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58
Q

A preliminary image used for positioning and planning the scan.

A

scout view

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59
Q

Continuous data acquisition during table movement and gantry rotation.

A

spiral CT

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60
Q

They visualize high-intensity structures like blood vessels.

A

maximum intensity projection (MIP)

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61
Q

The ability to differentiate between tissues with small density differences.

A

contrast resolution

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62
Q

What determines slice thickness in CT?

A

The collimator settings and detector configuration.

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63
Q

They ensure accurate image data by correcting variations in detector response.

A

detector calibration

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64
Q

Distortion due to averaging different tissue densities within one voxel.

A

partial volume effect

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65
Q

What are the typical power requirements for CT x-ray tubes?

A

> 120 kVp and 400 mA.

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66
Q

They supply high-frequency power to the x-ray tube.

A

high-voltage generator

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67
Q

What does slice overlap achieve in CT imaging?

A

Improved resolution and reduced partial volume effects.

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68
Q

What does beam collimation improve in CT?

A

Image contrast and reduction of scatter radiation.

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69
Q

How does table speed affect pitch in CT?

A

Faster table speed increases pitch, reducing image resolution.

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70
Q

What is a voxel?

A

A 3D volume element representing tissue, defined by pixel size and slice thickness.

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71
Q

What factors influence CT image noise?

A

Tube current, pixel size, slice thickness, and patient dose.

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72
Q

What is the principle behind dual-source CT?

A

Using two x-ray tubes and detector arrays to reduce scan time.

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73
Q

What is modulation transfer function (MTF) in CT?

A

A measure of how accurately a scanner reproduces details at varying spatial frequencies.

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74
Q

What is the effect of using a higher kVp in CT?

A

Increased x-ray penetration and reduced image noise.

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75
Q

What is the role of scintillation detectors in CT?

A

Converting x-rays to light and then to electrical signals for image reconstruction.

76
Q

What is the advantage of thin-slice imaging in CT?

A

Higher spatial resolution and reduced partial volume effects.

77
Q

What is the primary advantage of helical CT scanners?

A

Faster acquisition of volumetric data during a single breath-hold.

78
Q

What is CT dose index (CTDI)?

A

A measure of radiation exposure from a single CT scan.

79
Q

What is “automatic tube current modulation” in CT?

A

A system adjusting tube current based on patient size and density.

80
Q

What is a cone-beam artifact?

A

Distortion caused by the geometry of wide-beam CT acquisitions.

81
Q

High-density objects like metal causing bright or dark streaks in images.

A

streak artifacts

82
Q

It causes streaks or dark bands, particularly near dense structures.

A

beam hardening

83
Q

How is patient positioning critical in CT?

A

To ensure all relevant anatomy is within the scan field and reduce artifacts.

84
Q

What are the typical CT numbers for air and dense bone?

A

Air: -1000; Dense bone: +3000.

85
Q

Amplifies weak signals from detectors for processing.

A

preamplifier

86
Q

What is a significant limitation of spiral CT at higher pitches?

A

Reduced resolution along the z-axis.

87
Q

What are the benefits of adaptive filtration in CT?

A

Improved image quality by reducing noise and artifacts.

88
Q

What is the main advantage of curved detector arrays in CT?

A

Better alignment with the fan beam geometry for accurate detection.

89
Q

What are the key advantages of a multislice CT detector array?

A

Faster scans and better coverage of anatomical regions.

90
Q

A 3D rendering technique for visualizing surfaces of structures.

A

shaded surface display (SSD)

91
Q

It represents 262,144 individual cells for detailed image representation.

A

512x512 matrix

92
Q

They ensure even x-ray exposure across the detector array, reducing artifacts.

A

bow-tie filter

93
Q

What are examples of post-processing techniques in CT?

A

MIP, SSD, and MPR (Multiplanar Reformation).

94
Q

What is an example of an MSCT (Multi-Slice CT) advantage?

A

Reduced scan times for larger anatomical coverage.

95
Q

What is an artifact commonly associated with patient movement?

A

Motion artifacts, appearing as blurring or double images.

96
Q

How does pixel size affect spatial resolution in CT?

A

Smaller pixels improve spatial resolution.

97
Q

What are the two types of collimators in CT?

A

Pre-patient and post-patient collimators.

98
Q

What is the function of a scintillator in CT detectors?

A

To convert x-rays into light for further signal processing.

99
Q

What is a characteristic of third-generation CT scanners?

A

Rotating x-ray tube and detector array with a wide fan beam.

100
Q

What does “anisotropic voxel” mean?

A

A voxel with unequal dimensions along its axes.

101
Q

What are streak artifacts caused by?

A

High-density objects, such as metal implants or dense bone.

102
Q

What is the effect of thick slices in CT imaging?

A

Reduced spatial resolution but potentially lower noise.

103
Q

It reduces aliasing and enhances edge clarity.

A

oversampling

104
Q

What is the effect of increased pitch in spiral CT?

A

Faster scanning but reduced z-axis resolution.

105
Q

Estimating values between known data points for smoother images.

A

interpolation

106
Q

How is scatter radiation reduced in CT?

A

Through the use of collimators and high-efficiency detectors.

107
Q

What is a typical reconstruction algorithm in CT?

A

Filtered back projection or iterative reconstruction

108
Q

What are common CT contrast agents?

A

Iodinated compounds and sometimes barium for specific studies.

109
Q

What is a primary limitation of dual-source CT?

A

Increased complexity and cost of the scanner.

110
Q

What is a key advantage of electron beam CT?

A

High-speed imaging, often used for cardiac studies.

111
Q

What is the purpose of a histogram in CT image analysis?

A

To evaluate pixel value distribution and image uniformity.

112
Q

It represents a 3D tissue volume in the scanned area.

A

voxel

113
Q

The fraction of incident x-rays absorbed and converted to usable signals.

A

quantum efficiency

114
Q

What is a major advantage of iterative reconstruction in CT?

A

Improved image quality with lower noise and radiation dose.

115
Q

What is the difference between axial and spiral CT scanning?

A

Axial scans are step-by-step, while spiral scans involve continuous rotation and table movement.

116
Q

ensure accuracy in image data and reduce system noise.

A

calibration

117
Q

What is a cone-beam CT scanner typically used for?

A

Dental imaging and certain orthopedic studies.

118
Q

The time taken by the computer to create images from raw data.

A

reconstruction time

119
Q

It serves as the primary interface between the operator and system components.

A

host computer

120
Q

What is the advantage of high-speed rotors in CT x-ray tubes?

A

They dissipate heat efficiently, enabling prolonged imaging sessions.

121
Q

The distance the table moves between each scan acquisition.

A

table increment

122
Q

How does gantry tilting benefit certain CT scans?

A

It helps to avoid artifacts and improve visualization of specific anatomical planes.

123
Q

What is the benefit of using thinner slices in CT imaging?

A

Better resolution and reduced partial volume artifacts.

124
Q

The range between the smallest and largest detectable signals.

A

dynamic range

125
Q

To emit x-rays for capturing internal body structures.

A

x-ray tube

126
Q

Software to adjust for artifacts caused by x-ray energy changes.

A

beam hardening correction software

127
Q

How does CT achieve high temporal resolution?

A

By reducing gantry rotation time and using dual-source technology.

128
Q

Gradual deviation of CT numbers due to variations in data capture.

A

shading

129
Q

Reducing scatter radiation to improve image quality.

A

scatter suppression

130
Q

What is the effect of slice thickness on noise in CT images?

A

Thicker slices reduce noise but decrease spatial resolution.

131
Q

The inherent variability in CT numbers for a uniform object.

A

“system noise”

132
Q

What is a shaded volume display (SVD) used for in CT?

A

Creating 3D images sensitive to operator-selected pixel ranges.

133
Q

The ability to process and display data immediately during acquisition.

A

real-time reconstruction

134
Q

limit scatter reaching the detector and improve contrast resolution.

A

pre-detector collimators

135
Q

It minimizes artifacts like beam hardening and motion streaks.

A

artifact correction

136
Q

What is the principal use of CT angiography (CTA)?

A

Visualizing blood vessels in 3D for diagnostic purposes.

137
Q

What is the function of the integrator in CT data acquisition systems?

A

To sum the signals received from detectors.

138
Q

What is the typical range of CT numbers for fat and muscle?

A

Fat: -100; Muscle: 50.

139
Q

control imaging parameters and monitor scan progress.

A

operating console

140
Q

How is field of view (FOV) related to matrix size?

A

Larger FOV increases pixel size for the same matrix.

141
Q

What is a slip-ring technology advantage in CT?

A

It allows continuous rotation of the gantry for faster scans.

142
Q

What is the purpose of a patient couch in CT?

A

To position the patient accurately for imaging.

143
Q

The automated movement of the patient table between scans.

A

“couch indexing”

144
Q

Enhancements like 3D reconstructions and multiplanar reformation.

A

post-processing

145
Q

What are the benefits of multislice CT (MSCT)?

A

Faster acquisition, greater coverage, and higher resolution imaging.

146
Q

The ratio of table movement per rotation to beam width.

A

pitch

147
Q

limit x-ray exposure to the area of interest, reducing scatter.

A

beam collimation

148
Q

A preliminary image used to position the patient before scanning.

A

scout image

149
Q

A circular artifact caused by a faulty or miscalibrated detector.

A

ring artifact

150
Q

What is the principle of CT reconstruction?

A

Converting raw data into cross-sectional images using algorithms.

151
Q

a measure of radiation dose in a single scan slice.

A

CT Dose Index (CTDI)

152
Q

What is the impact of increased detector rows in CT?

A

Faster scan times and better anatomical coverage.

153
Q

enhances image quality and reduce patient radiation dose.

A

iterative reconstruction

154
Q

What is “volume imaging” in CT?

A

Capturing a continuous 3D data set instead of individual slices.

155
Q

What is “temporal resolution” in CT?

A

The scanner’s ability to image moving objects clearly.

156
Q

What are common post-processing techniques in CT?

A

MIP, MPR, SSD, and volume rendering.

157
Q

An artifact caused by insufficient x-ray photons reaching the detector.

A

photon starvation

158
Q

What are the key factors affecting spatial resolution in CT?

A

Pixel size, slice thickness, and detector size.

159
Q

What is “contrast enhancement” in CT imaging?

A

Using contrast agents to improve the visualization of structures.

160
Q

What is the significance of the matrix size in CT imaging?

A

Larger matrix sizes provide better image detail.

161
Q

The longitudinal distance the patient table moves per gantry rotation.

A

table speed

162
Q

An image where pixel values are represented as varying shades of gray.

A

gray-scale image

163
Q

What is the impact of high kVp settings in CT?

A

Increased penetration with reduced noise and beam hardening artifacts.

164
Q

What is “detector efficiency” in CT?

A

The ability of a detector to capture and convert x-rays to signals.

165
Q

Software or techniques to minimize artifacts from energy shifts in the x-ray beam.

A

beam-hardening correction

166
Q

What does “data interpolation” achieve in CT?

A

Filling in missing data points to create smoother images.

167
Q

It determines resolution and influences partial volume effects.

A

slice thickness

168
Q

A 3D imaging technique using the entire voxel data for visualization.

A

volume rendering

169
Q

What is “effective dose” in CT radiation measurements?

A

The total radiation risk considering tissue sensitivity.

170
Q

What is a “pixel” in CT imaging?

A

smallest 2D element in the imaging matrix.

171
Q

performs calculations and logical operations for image reconstruction.

A

central processing unit

172
Q

What is “maximum intensity projection” (MIP)?

A

A technique to display the highest-intensity pixels along viewing lines.

173
Q

Bright or dark lines caused by high-density objects or beam hardening.

A

streak artifacts

174
Q

What is a major advantage of dual-energy CT?

A

Differentiating materials based on their energy-dependent attenuation properties.

175
Q

Techniques to minimize random variations in pixel values.

A

noise reduction

176
Q

What is “isotropic resolution” in CT imaging?

A

Equal spatial resolution in all dimensions (x, y, z).

177
Q

Filtering techniques to enhance image quality by reducing noise.

A

adaptive filtration

178
Q

What is the benefit of “overlapping slices” in CT?

A

Improved z-axis resolution and reduced artifacts.

179
Q

To measure x-rays after they pass through the patient and convert them into signals.

A

detectors

180
Q

What is the impact of low pitch values in CT scanning?

A

Increased resolution but higher patient dose.

181
Q

What is “partial volume effect”?

A

Misrepresentation of tissue density due to averaging within a voxel.

182
Q

How is “slice thickness” related to image noise?

A

Thicker slices reduce noise levels in the image.

183
Q

Adjusting for distortions like beam hardening and motion artifacts.

A

artifact correction

184
Q

What is the purpose of “gantry tilt” in CT imaging?

A

To align the scan plane with the anatomy or avoid certain structures.

185
Q

What is “table increment” in CT?

A

The distance the patient table moves between consecutive scans.

C5 (5 decks)

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