Computed Tomography Scan Parameters Flashcards
is a set of user selectable factors that determines the resultant CT image, the scan length, orientation, image size, thickness and increment, noise etc.
Scan parameters
To change a specific scan parameter is also to change
the resultant images
This is the position of the patient relative to the gantry and the patient couch
SUPINE
PRONE
LEFT OR RIGHT LATERAL DECUBITUS
Where must the body part of interest be placed for CT scans
Isocenter
Are specific points in the body that will determine the scan area
Anatomical landmarks in CT
Anatomical landmark for Heat CT
glabella
Anatomical landmark for Neck CT
thyroid cartilage
Anatomical landmark for chest and neck CT
Sternal notch
Anatomical landmark for Abdominal CT
Xiphoid Process
the scanned projection radiograph, acquired by the CT system to allow the user to prescribe the start and end locations of the scan range
Scout image or the CT localizer radiograph
These images are not cross-sectional in nature; rather they are very similar to images acquired with conventional radiographic projection techniques
Scout Image
What does GE call scout imaging?
Scout
What does Philips call scout imaging?
Surview
What does Siemens call scout imaging?
Topogram
What does Toshiba call scout imaging?
Scanogram
What does Hitachi call scout imaging?
Scanogram
Where is tube suspended during scout generation
above patient
How is the tube positioned for Lat Scout?
90 degree angles to patient
basically the length of the scan (hence the word scan length technologist sometimes refer to) measured in millimeters
Range
This is planned on the scout image, also varies depending on the protocol selected and patient size
scan range
Also called calibration field of view
Scan Field of View (SFOV)
Diameter of the circular region within the scan plane over which projection data are collected
Scan Field of View
It depends on the number of detectors activated to collect the data.
Scan Field of View
How is scan field of view determined?
Number of detectors activated
For best resolution, what is the best scan field of view size?
Smallest possible
Directional coordinate systems have been called
RAS systems (Right-left, Anterior-posterior, Superior-inferior. )
The body part included in the region of interest but outside the scan field of view will not have any data and not included in the scan
OUT OF FIELD artifact
Determines how much raw data is used in displaying the acquired image
Display Field of View
Display Field of View is also called
zoom or target
Relationship of Display field of view with scan field of view
DFOV CAN BE EQUAL OR LESS OF SFOV
Relationship of DFOV size and pixel, resolution and detail
Large DFOV, Large Pixels, = Low Spatial Resolution, Low visibility of detail
Mode where the table stops at the scanning position and the tube rotates around the patient
Conventional/Axial/Regular Mode
Patient continuously moving in the z-axis direction while the tube rotates around
Spiral/Helical
Alternative name for reconstruction algorithms
Convolution kernels
Various filters applied in filtered back projection reconstruction
Reconstruction Algorithm
Various Types of Filter for soft tissue (abdomen , stonogram, muscles)
Head – for the brain
Bone – For osseous parts of the body
Detail – for body parts that requires high spatial resolution (eg. Neck)
Standard
Various Types of Filter for the brain
Bone – For osseous parts of the body
Detail – for body parts that requires high spatial resolution (eg. Neck)
Head
Various Types of Filter for osseous parts of the body
Detail – for body parts that requires high spatial resolution (eg. Neck)
Bone
Various Types of Filter for body parts that requires high spatial resolution (eg. Neck)
Detail
Depending on the examination, the gantry housing can be tilted.
This is mostly done in the axial scanning.
The range of tilt depends on the position of the organs to be scan on the scout image
Gantry Angle
What does lower kV do to the resultant CT image
Lower kV
What happens to kV as it is lowered and how it affects noise?
Lower kV=more noise
