COMPUTED TOMOGRAPHY Flashcards
A scan of air in the gantry used to calibrate the scanner based on air density.
air calibration
Define “algorithm” in the context of CT imaging.
A mathematical formula for enhancing image features like soft tissue and edges.
Resolution where voxel dimensions differ along three axes.
anisotropic spatial resolution
What does “aperture” mean in a CT scanner?
The opening in the gantry where the patient passes during the scan.
Storing CT images on long-term devices like tapes or disks.
archiving
An image distortion unrelated to the subject being scanned.
artifact
What is “attenuation” in CT imaging?
The reduction of x-ray intensity by tissue density, resulting in CT numbers.
What plane does “axial” refer to in CT imaging?
The transverse plane.
What is a “bolus” in CT imaging?
Rapid IV injection of contrast media to enhance vascular imaging.
Rows of detector assemblies in the scanner.
channel
What is Computed Tomography (CT)?
A rotating x-ray tube and detector assembly creating cross-sectional images.
Volumetric imaging to construct 3D images of vascular structures.
CT angiography
How are CT numbers related to tissue density?
Higher CT numbers indicate denser tissues, and lower numbers indicate less dense tissues.
What is the CT number assigned to water?
0
What is the purpose of curved planar reformations in CT?
To create images in irregular or oblique planes using post-processing.
Converts analog signals to digital signals for CT image computation.
Data Acquisition System (DAS)
What materials are CT detectors commonly made of?
High-density photo-reactive crystals or pressurized stable gases.
A dose descriptor summarizing the radiation exposure over a scanned length.
dose-length product (DLP)
What is “dynamic scanning” in CT imaging?
Continuous raw data collection for later reconstruction, often used for high-flow vascular imaging.
What is the field of view (FOV) in CT?
The anatomical area displayed on the monitor, adjustable as needed.
What does the gantry in a CT scanner house?
X-ray tube, cooling system, detector assembly, and DAS.
What are the primary benefits of helical CT scanning?
Faster imaging with a continuous spiral data path and improved 3D reformation.
What are Hounsfield Units (HU)?
Numerical values indicating tissue density in a CT scan.
What is “image misregistration”?
Distortion caused by table movement or patient respiration during scans.