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Medical Physics

Imaging comparisons

  • 7 things to know
  • Paper 3, section B

Overview

Weighing X-ray, CT, ultrasound, MRI and PET on resolution, dose, cost and availability.

What you need to know

Answer each one before you reveal it.

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Process

How available, fast and costly is X-ray imaging?

Numbers

Why do cost and scan duration matter when comparing imaging methods?

Evaluation

How do CT scan times compare with plain X-rays, and what justifies the extra cost?

Evaluation

Why is MRI ruled out for some patients, and how does its cost compare?

Process

Why is PET scanning expensive, why is its availability limited, and why does it need a cyclotron?

Evaluation

What long-term health risk is associated with repeated exposure to ionising radiation from medical imaging?

Key term

What thermal effect can occur in tissues during MRI scanning?

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    What type of spatial resolution does X-ray imaging provide, and for which structures is it particularly effective?

    Model answer

    X-ray imaging provides high spatial resolution, particularly effective for dense structures such as bone.

  2. 2

    What advantage does CT scanning offer in terms of image detail compared to plain X-rays?

    Model answer

    CT scanning offers detailed cross-sectional images with good resolution, providing three-dimensional information.

  3. 3

    For which type of tissue does MRI provide excellent contrast resolution?

    Model answer

    MRI provides excellent soft tissue contrast resolution.

  4. 4

    How does the spatial resolution of ultrasound compare to other imaging techniques?

    Model answer

    Ultrasound has lower spatial resolution than X-ray, CT, or MRI, but it is adequate for many diagnostic purposes.

  5. 5

    What characterises PET scanning in terms of spatial resolution and functional information?

    Model answer

    PET scanning has relatively low spatial resolution but high functional sensitivity, allowing detection of metabolic activity.

  6. 6

    Name one convenience factor related to the physical characteristics of imaging equipment.

    Model answer

    Equipment portability — some imaging devices can be moved to the patient's location while others require dedicated rooms.

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