Image Production- Basics And Scan Modes Flashcards
On the basis of what can an image of an object be reconstructed and occurs as radiation is transmitted through that object?
Attenuation
What rotated around the patient, exposing a given volume of tissue from all directions?
X-ray beam
What measures the radiation that is transmitted through the patient?
Detectors
What is based on the magnitude of X-ray attenuation that occurs at spatially distributed points within the patient?
Magnitude
What are the 4 major steps to the general process of CT imaging?
Data acquisition, data reconstruction, multidimensional image display, and image archival and communication
Measurement of the attenuation that occurs along each path through the patient from X-ray tube to detector?
Data acquisition
Computerized processing of the transmission measurements into the CT image?
Data reconstruction
Display of the reconstructed grayscale image in 2D and 3D format; representation of the attenuation that occurred across the scanned volume of tissue?
Multidimensional image display
Display as well as storage, both short-term and long-term, of images on computer workstations?
Image archival and communication
What is the most basic scan mode utilized by a CT system?
Scout image
How are the tube and detectors fixed around the patient for a scout image?
Stationary
What are two other names for a scout?
Scan organ or localizer
What positions may a scout image be reproduced in?
AP, PA, lateral, or oblique
What is a term describing the angle of the tube and detectors in relationship to the patient position during a scout acquisition?
Azimuth
What scanning method involves a complete revolution of the X-ray tube around the patient, acquiring a single data set at a certain location?
Axial/conventional
What is another name for axial scanning?
Step-and-shoot
How does axial acquisition work to obtain data?
Patient is scanned when table is not moving, data processed, table moves patient into next position, patient is scanned, and so on.
What three components make up the CT system?
Powerful computer and display system, patient bed, gantry components
What components are housed within the CT gantry?
Generator, X-ray tube, assorted collimators, DAS, slip-rings and detectors
What were the CT systems originally composed of that prevented continuous rotation in the gantry?
Hardware cables
What new CT technology eliminated the need for cables by utilizing a system of contact brushes that supply electricity to power the system and enable passage of transmission data to the computer?
Slip-ring technology
What new type of image acquisition was made possible by slip-ring technology?
Helical scanning
What are 4 technical elements of helical CT acquisition?
Continuous rotation of the gantry components (slip-rings),
Tube capable of long exposure output, continuous movement of patient bed,
Specialized mathematical reconstruction techniques
What type of data acquisition is allowed for by helical geometry?
Volumetric
What is image reconstruction slice thickness controlled by, makes the width uniform, and is set before acquisition?
Collimation
