Computed Tomography 2 Flashcards
CT scanner equipment
What does a CT scanner consist of
Gantry = houses the x-ray tube, detectors and generator
X-ray tube which rotates 360 degrees in the axial plane around the patient’s body
Filter = which improve the efficiency of the x-ray beam
Collimators = reduce patient dose and improve image quality
Detectors = arranged in rows rotating in a continuous arch directly opposite the x-ray tube
What features do CT x-ray tubes have to help them dissipate heat quickly?
- High-speed rotors which provide good heat dissipation
- Direct oil cooling of the anode
- Scanners are designed to use focal spot cooling algorithms
Where are the collimators in a CT scanner located?
Ct scanners have collimators in two positions.
There are pre patient collimators that collimate the x-ray beam at the x-ray tube
There are pre detectors that collimate the x-ray beam after it passes through the patient.
What is the purpose of collimators in CT
- Collimators reduce the radiation dose by limiting the volume of tissue irradiates.
- They also improve the image contrast by limiting scatter and reducing noise
- The pre detector collimators provide a contrast beam width on the detectors.
What is the purpose of detectors in CT ?
Detectors convert x-ray photons into electrical signals called analog data which is then converted to digital information for computer reconstruction.
What are the ideal properties of a CT detector?
- They should have a high dynamic range to allow the detector to respond to a wide range of X-ray intensities.
- The detector should be highly efficient so it can capture, absorb and convert x-ray photons to electrical signals
- The detector should be robust, stable, and have a fast response.
- The detector should produce little after glow to maintain image quality