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Questions and Answers
What is the characteristic of the first generation of computed tomography?
What is the characteristic of the first generation of computed tomography?
How long is the imaging time for the second generation of computed tomography?
How long is the imaging time for the second generation of computed tomography?
What type of X-ray beam shape is used in the second generation of computed tomography?
What type of X-ray beam shape is used in the second generation of computed tomography?
What is one disadvantage of the first generation of computed tomography?
What is one disadvantage of the first generation of computed tomography?
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Which generation of computed tomography introduces the use of multiple detectors?
Which generation of computed tomography introduces the use of multiple detectors?
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Which of the following describes a key characteristic of the first generation's imaging method?
Which of the following describes a key characteristic of the first generation's imaging method?
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What is a key advantage of the second generation of computed tomography?
What is a key advantage of the second generation of computed tomography?
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Which aspect of imaging in the first generation of computed tomography is critical in its design?
Which aspect of imaging in the first generation of computed tomography is critical in its design?
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Who proposed the method for representing a single slice of the body on radiographic film in the 1930s?
Who proposed the method for representing a single slice of the body on radiographic film in the 1930s?
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What distinguishes the plane of the image in conventional or axial tomography?
What distinguishes the plane of the image in conventional or axial tomography?
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What does the term 'binary digit' or 'bit' represent in computing?
What does the term 'binary digit' or 'bit' represent in computing?
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In what year did Hounsfield and Cormack share the Nobel Prize in Physics?
In what year did Hounsfield and Cormack share the Nobel Prize in Physics?
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What is a key feature of the 4th generation CT scanner?
What is a key feature of the 4th generation CT scanner?
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What type of image does computed tomography primarily produce?
What type of image does computed tomography primarily produce?
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What is the primary advantage of the helical or spiral CT scanner in the 6th generation?
What is the primary advantage of the helical or spiral CT scanner in the 6th generation?
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What does the term 'projection' refer to in the context of computed tomography?
What does the term 'projection' refer to in the context of computed tomography?
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Which of the following was the first clinical CT scanner installed?
Which of the following was the first clinical CT scanner installed?
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What dynamic range of gray levels does the detector signal for CT typically have?
What dynamic range of gray levels does the detector signal for CT typically have?
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Flashcards
Reconstruction Time
Reconstruction Time
The time it takes a computer to display a digital image after a medical exam is completed.
First Generation CT
First Generation CT
Early Computed Tomography (CT) using a pencil beam and a single detector.
Second Generation CT
Second Generation CT
CT improvement using a fan beam and several detectors to obtain images faster.
CT Reconstruction
CT Reconstruction
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Pencil Beam
Pencil Beam
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Fan Beam
Fan Beam
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Multiple Detectors
Multiple Detectors
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Imaging Time
Imaging Time
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Computed Tomography (CT)
Computed Tomography (CT)
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CT Scanner
CT Scanner
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Binary System (in CT)
Binary System (in CT)
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Transaxial/Transverse Image
Transaxial/Transverse Image
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Projection (in CT)
Projection (in CT)
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Detector signal (CT)
Detector signal (CT)
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Algorithm (in CT)
Algorithm (in CT)
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Detector Array
Detector Array
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Storage Requirement (CT)
Storage Requirement (CT)
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Study Notes
Computed Tomography (CT)
- CT creates cross-sectional images of the body using a rotating fan beam, detector array and computed reconstruction
- Other names include Axial Tomography (CAT), Computed Transaxial Tomography (CTAT), Computed Reconstruction Tomography (CRT), and Digital Axial Tomography (DAT)
- Greek word "tomos"—slice/section; "graphia"—describing
- 1930's - Alessandro Vallebona proposed a method to represent a single slice of the body on radiographic film (topography)
- 1970 - Godfrey Newboid Hounsfield developed the CT technique
- 1972-1974 - First CT scanners were installed
- 1979 - Used a binary system of 0s and 1s to represent shades of gray
- 1980 - Hounsfield & McLeod Cormack shared the Nobel Prize in physics for their work on CT
- CT scan machines became widely available
- The first CT scan machine had 180 translations/1° rotation
- 1st CT system that could make images of any part of the body and did not require a water tank (ACTA)
Principles of Operation
- Conventional/Axial Tomography: The plane of the image is parallel to the long axis of the body; Produces sagittal and coronal images
- Computed Tomography: The plane of the image is perpendicular to the long axis of the body; Produces transverse image
CT Image
- A transaxial/transverse image
- Translation/Sweep: Movement of the X-ray source-detector assembly across the patient
- Projection: Represents the attenuation pattern of patient profile
- Detector signal: Has a dynamic range of 12 bits (4096 gray levels)
Algorithms
- Computer-adapted mathematical calculations applied to raw data during image reconstruction
- Different generations of CT scanners
Reconstruction
- Creating an image from the data.
- Time needed for the computer to create the image after the examination.
- Time between imaging and the image’s appearance.
Generations of Computed Tomography
(The given text contains information on 1st to 7th generation technologies).
CT Image Characteristics
- Imaging matrix: Layout of cells in rows and columns of information
- Pixel: A picture element; the size is FOV divided by the matrix size
- Voxel: A volume element; the volume is determined by the pixel size multiplied by the slice thickness
- CT Number/Hounsfield Unit (HU): Represents the number assigned to each tissue.
CT Numbers for Various Tissues
(A table of various tissues and their corresponding CT numbers)
Image Reconstruction
- Filter back projection: Process by which an image is acquired, stored, and reconstructed.
Image Quality
- Spatial Resolution, Contrast Resolution, Noise, Linearity, Uniformity
Physics-Based Artifacts
- Beam-hardening artifact, Cupping artifact, Streak artifact
- Partial Volume artifacts, Photon Starvation artifacts, Metal artifacts
Patient-Based Artifacts
- Patient Motion artifacts, Incomplete projections
Scanner-Based Artifacts
- Ring artifacts
Data Acquisition System (DAS)
- Computer controlled electronic amplifier and switching device.
- Connects the signal from the detectors.
- Consists of preamplifier, integrator, multiplexer, logarithmic amplifier, etc
High Voltage Generator
- High frequency power, high voltage step-up transformers
- Power is required that is >120 kVp and 400mA
Other important topics
- Collimation: Restricts the volume of tissue irradiated, reducing patient dose, and improving contrast.
- Three Important Factors for Detector Efficiency: The geometry of CT detectors (e.g., pixel size). The quantum efficiency, converting X-ray photons to electrical signals. overall/dose efficiency.
- Operating Console: Contains meters and controls, enabling operators to adjust various imaging parameters or to retrieve information.
- Gantry: The largest component of the CT system containing the X-ray source (e.g., X-ray tube).
- Computers: Used in the control systems, and for data reconstructions, calculations, and for storage.
- Two Monitors: One for viewing and diagnosis, and the second for operator manipulation.
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Description
This quiz covers the fundamental concepts of Computed Tomography (CT), including its history, operation, and various terminologies associated with the technique. Explore the developments in CT technology and the contributions of key figures in this field. Ideal for students in medical physics or radiology.
