In a CT scanner, how does the X-ray tube move relative to the patient during image acquisition?

The X-ray tube rotates around the patient to acquire projections from multiple angles.

Why does the X-ray tube in a CT scanner need to acquire data from multiple angles?

To obtain sufficient projection data from different directions, which is required for mathematical reconstruction of cross-sectional images.

What type of X-ray beam geometry is used in CT scanning to reduce scatter?

A narrow, collimated X-ray beam.

How does using a collimated X-ray beam improve CT image quality?

It reduces scatter radiation reaching the detectors, which improves image contrast and quality.

What energy characteristic should the X-ray beam in a CT scanner ideally have?

It should be monochromatic (single energy).

AQA A-Level Physics 7408

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Medical Physics

CT scanner

4 things to know
Paper 3, section B

Overview

How a CT image is reconstructed, and the dose and cost weighed against the detail gained.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Evaluation

What do reconstruction algorithms do, and what detail advantage does CT offer?

Key term

Why is a monochromatic beam preferred, and where are the detectors placed?

Evaluation

How do the dose and cost of CT compare with a plain X-ray, and what risk follows?

Key term

How can three-dimensional images of anatomy be generated from CT data?

Questions from this subtopic

Each one with the model answer underneath.

1
In a CT scanner, how does the X-ray tube move relative to the patient during image acquisition?
Model answer
The X-ray tube rotates around the patient to acquire projections from multiple angles.
2
Why does the X-ray tube in a CT scanner need to acquire data from multiple angles?
Model answer
To obtain sufficient projection data from different directions, which is required for mathematical reconstruction of cross-sectional images.
3
What type of X-ray beam geometry is used in CT scanning to reduce scatter?
Model answer
A narrow, collimated X-ray beam.
4
How does using a collimated X-ray beam improve CT image quality?
Model answer
It reduces scatter radiation reaching the detectors, which improves image contrast and quality.
5
What energy characteristic should the X-ray beam in a CT scanner ideally have?
Model answer
It should be monochromatic (single energy).
6
What imaging artefact is avoided by using a monochromatic X-ray beam in CT?
Model answer
Beam hardening artefacts.

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