Computed Tomography 4 Flashcards
generations of ct scanners
Describe a first-gen Ct scanner
It consists of a detector and a pencil-like x-ray beam. It would take 5 minutes tom capture a slice and 20 minutes to analyse the data
Describe a second-gen CT scanner
It has multiple detectors and a fan-shaped beam which made it faster than the first-gen scanner
Describe a third-gen CT scanner
It has a rotating x-ray tube linked to an arch of detectors. However the tube could only rotate 180 degrees to each side of the patient, not 360 otherwise the cables would twist up.
Describe a fourth-gen CT scanner
It has detectors all around the gantry and the X-ray beam could rotate 360 degrees around the patient however it was quite expensive.
Describe a spiral CT scanner
It has rotating slip rings which allow electricity to be conducted by brushes touching them. Its this conduction that permits continuous x-ray tube and detector rotation around the patient without the risk of the cable twisting
What are the advantages of multiple detector scanners over single detector scanners?
They allow us to take multiple slices during a scan speeding up the scanning process and optimizing the time available to scan after contrast injection.
The faster scanning time reduced radiation dose
It allows us to acquire thick and thin slices over large volumes simultaneously. Thick slices produce low image noise allowing good image quality. Thin slices allow more detail to be seen. The ability to capture both types of slices faster allows faster diagnosis ans saves time
Describe and compare the two methods of data acquisition?
Conventional slice by slice data acquisition is the step and shoot method where a slice is scanned and the table moves and the next slice is taken.
Volume data acquisition is when the x-ray tube and detectors continuously rotate around the patient tracing a spiral path to cover the volume of the patient.
The conventional slice by slice method takes more time and gives higher doses whereas the volume acquisition method is faster and has a lower radiation dose.
