CT Basics And Model Flashcards
What are the 3 segments of CT imaging?
- Data acquisition
- Image recons
- Image display
What is data acquisition?
X-rays passing through the patient and hitting the detector
What is the gantry?
Ring shaped frame of the CT scanner.
It may be tilted forward or backward depending on patient or exam type.
What are slip rings?
Help the gantry frame continuously rotate for helical scans via electronically powered communication
What is the generator?
Power the scanner that control the exposure factors and are:
- High frequency
- High voltage
- High beam energy
- High penetrating ability
- High patient dose
What exposure technique helps to extend generator life?
High kV and low mAs
What are cooling systems?
Cool the scanner due to high heat from producing x-rays and include…
- blowers
- filters
- oil to air heat exchange
What material is the x-ray source usually made from?
Tungsten because it has a high atomic number and high melting point
What size focal spot is better for image quality and why?
A SMALLER focal spot produces sharper images because it reduces penumbra
(Heat concentrates on smaller portion of anode —> cannot tolerate as much heat)
What is a flying focal spot?
Multiple focal spots that create 2 beams and overlap directed at the same single detector array
What role does filtration have and what are the benefits?
- Filters out low energy x-rays
- Shapes the beam
Reduced patient dose and less image artefact
What filter is commonly used for body imaging?
Bow tie filter (thicker to lessen the beam for the body periphery)
What benefits does collimation have?
- Reduce scatter radiation
- Lower patient dose
- Increases image quality
What does collimation do?
Determine slice thickness and dose profile
What are detectors?
Array/collection of detectors that capture data from x-rays after passing through the patient
What are optimal characteristics of detectors?
- High detector efficiency
- Low/no afterglow
- High scatter suppression
- High stability
What type of detector was and is used?
Past: xenon gas
Now: solid-state crystal
What are different types of detector arrays?
- Matrix array - evenly sized elements
- Hybrid array - most elements the same size with smaller rows in the middle
- Adaptive array - smaller elements in the middle and progressively getting larger the farther it goes out
What determines the scanner generation?
Tube and detector configuration
What is the 1st generation scanner generation?
Thin linear beam over the patient with a single detector opposite to the tube
What beam style is used for a 1st gen scanner generation?
Pencil beam
What is the 2nd generation of the scanner?
Fan shaped beam that is linear over the patient before rotating with single detector array opposite tube
What is the 3rd generation of scanner?
Fan shaped beam travels linearly over patient with detector array opposite to the tube.
Both tube and detectors rotate in the gantry.
What is another name for the 3rd gen scanner?
Rotate rotate scanner
