AQA · A-Level · Physics

    Course version: 7408 · Version from Sept 2016

    Advantages of FTP detector compared with photographic detection.

    Full specification wording

    Image detection and enhancement (A-level only): Advantages of FTP detector compared with photographic detection.

    Photographic detection uses film that must be chemically developed before the image can be seen, and the film responds over a limited exposure range.

    Checked against the AQA 7408 specification (opens in a new tab) on .

    • Point 2 of 4
    • 4 key terms

    Study notes

    From the checked teaching notes for this specification point.

    The idea

    Photographic detection uses film that must be chemically developed before the image can be seen, and the film responds over a limited exposure range. A flat panel detector instead produces an electrical signal that is digitised immediately, so the image is available within seconds and can be displayed, stored and transmitted electronically. Because the pixel response is linear over a wide range of X-ray intensities, subtle differences in attenuation remain visible, improving contrast resolution. The digital data can be windowed and enhanced after exposure without repeating the scan, reducing patient dose. There is no film to load, process, handle or archive physically, so workflow is faster and storage is compact. Electronic images can also be shared across networks for reporting and comparison with previous examinations.

    What earns the marks

    • Immediate electronic readout gives the image in seconds, whereas photographic film requires chemical development before viewing.
    • Digital storage and transmission replace bulky film archives, allowing rapid access, copying and comparison with earlier images.
    • A wide linear dynamic range means small differences in X-ray attenuation are recorded, improving contrast resolution compared with film.
    • Post-acquisition processing such as windowing and enhancement can improve the displayed image without further patient exposure.
    • Lower retake rates and reduced repeat exposures follow from immediate checking of image quality, lowering overall patient dose.
    • No chemical developer or fixer is needed, removing processing consumables and associated waste.

    Common mistakes and how to put them right

    • Claiming flat panel detectors use no radiation.

      Put it right: They still require X-rays, but the dose per useful image can often be reduced.

    • Saying film gives an instant image.

      Put it right: Film needs development time before it can be viewed.

    • Assuming digital images cannot be altered.

      Put it right: They can be processed and enhanced, which is an advantage when used appropriately.

    Exam tips

    • Structure comparisons as paired points: what film does, what the flat panel detector does, and why that matters clinically.
    • Use precise terms such as dynamic range, contrast resolution and post-acquisition processing rather than vague words like better.
    • Where dose is mentioned, explain the mechanism, for example fewer repeat exposures because the image can be checked immediately.

    Try the lesson

    The start of the Image detection and enhancement (A-level only): Advantages of FTP detector compared with photographic detection. lesson, made from checked teaching notes for this specification point.

    Have a go first

    Which advantage does an FTP detector have over photographic film when a radiographer needs the image immediately?

    Listen

    Photographic detection uses film that must be chemically developed before the image can be seen, and the film responds over a limited exposure range. A flat panel detector instead produces an electrical signal that is digitised immediately, so the image is available within seconds and can be displayed, stored and transmitted electronically. Because the pixel response is linear over a wide range of X-ray intensities, subtle differences in attenuation remain visible, improving contrast resolution. The digital data can be windowed and enhanced after exposure without repeating the scan, reducing patient dose. There is no film to load, process, handle or archive physically, so workflow is faster and storage is compact. Electronic images can also be shared across networks for reporting and comparison with previous examinations. A strong answer earns marks for these points. Immediate electronic readout gives the image in seconds, whereas photographic film requires chemical development before viewing. Digital storage and transmission replace bulky film archives, allowing rapid access, copying and comparison with earlier images. A wide linear dynamic range means small differences in X-ray attenuation are recorded, improving contrast resolution compared with film. Post-acquisition processing such as windowing and enhancement can improve the displayed image without further patient exposure. A common slip: Claiming flat panel detectors use no radiation. Instead, they still require X-rays, but the dose per useful image can often be reduced. Exam tip: Structure comparisons as paired points: what film does, what the flat panel detector does, and why that matters clinically.

    See it

    A top-down flowchart with two starting points. On the left, a node reading 'Photographic film: chemical development before viewing' leads to 'Limited exposure range'. On the right, a node reading 'Flat panel detector: electrical signal digitised immediately' branches into three paths. The first path leads to 'Image available within seconds', which leads to 'Displayed, stored and transmitted electronically', which leads to 'Compact storage and network sharing'. The second path leads to 'Linear pixel response over wide range of X-ray intensities', then to 'Subtle attenuation differences remain visible', then to 'Improved contrast resolution'. The third path leads to 'Windowing and enhancement after exposure', then to 'Reduced patient dose'.
    It contrasts photographic film, which needs chemical development and has a limited exposure range, with a flat panel detector, whose immediate digital readout, wide linear range and post-acquisition processing give faster workflow, better contrast resolution and reduced patient dose.

    Key words

    Say what each word means before you turn the card.

    Digital versus analogue imaging

    Try answering aloud or in your head before turning the card.

    Patient dose optimisation

    Try answering aloud or in your head before turning the card.

    Image quality and contrast resolution

    Try answering aloud or in your head before turning the card.

    Clinical workflow and data storage

    Try answering aloud or in your head before turning the card.

    See every definition
    Digital versus analogue imaging
    A flat panel detector produces an electrical signal that is digitised immediately, so the image is available within seconds, whereas photographic film must be chemically developed before the image can be seen.
    Patient dose optimisation
    Digital data can be windowed and enhanced after exposure without repeating the scan, and lower retake rates and reduced repeat exposures follow from immediate checking of image quality, lowering overall patient dose.
    Image quality and contrast resolution
    Because the pixel response is linear over a wide range of X-ray intensities, subtle differences in attenuation remain visible, improving contrast resolution.
    Clinical workflow and data storage
    There is no film to load, process, handle or archive physically, so workflow is faster and storage is compact, and electronic images can be shared across networks for reporting and comparison with previous examinations.

    Label the diagram

    Some boxes have lost their names. Pick the right name for each number.

    The diagram again, with 3 boxes numbered instead of named. A top-down flowchart with two starting points. On the left, a node reading 'Photographic film: chemical development before viewing' leads to 'Limited exposure range'. On the right, a node reading 'Flat panel detector: electrical signal digitised immediately' branches into three paths. The first path leads to 'Image available within seconds', which leads to 'Displayed, stored and transmitted electronically', which leads to 'Compact storage and network sharing'. The second path leads to 'Linear pixel response over wide range of X-ray intensities', then to 'Subtle attenuation differences remain visible', then to 'Improved contrast resolution'. The third path leads to 'Windowing and enhancement after exposure', then to 'Reduced patient dose'.

    • 1Box 1

    • 2Box 2

    • 3Box 3

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