A - DIGITAL IMAGES
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Questions and Answers

The size of a digital image file is determined solely by the number of pixels in the image.

False (B)

What is the term used for the individual picture elements that make up a digital image?

Pixels

The file extension for a Digital Imaging and Communications in Medicine (DICOM) file is ______.

.dcm

Match the following imaging modalities with their corresponding signal types:

<p>Radiography = X-ray emission Computed Tomography (CT) = Fan-beam x-ray attenuation Ultrasound = Sound wave reflection Magnetic Resonance Imaging (MRI) = Radiofrequency emission</p> Signup and view all the answers

Which of these factors does NOT directly affect the spatial resolution of a digital image?

<p>Image contrast (C)</p> Signup and view all the answers

A digital image with a larger matrix size will always have a larger file size.

<p>True (A)</p> Signup and view all the answers

What is the name of the additional information stored in a DICOM file aside from the image data itself?

<p>Metadata tags</p> Signup and view all the answers

What is the primary difference between analog and digital imaging in radiography?

<p>Digital imaging uses a digital recording device instead of a film cassette. (B)</p> Signup and view all the answers

The number of gray shades a pixel can display is directly related to the image's bit depth.

<p>True (A)</p> Signup and view all the answers

In digital radiography, each pixel is assigned a ____ of gray.

<p>shade</p> Signup and view all the answers

What are the two main types of digital radiography acquisition hardware?

<p>Computed radiography (CR) and direct digital radiography (DDR)</p> Signup and view all the answers

What happens to the contrast of an image if a pixel can only display a few gray shades?

<p>The image will have high contrast. (B)</p> Signup and view all the answers

Match the following terms with their corresponding definitions:

<p>Bit depth = The number of allowable zeroes and ones per pixel, determining the number of possible gray shades. Pixel size = The physical size of a single pixel in the image. Contrast = The difference in brightness or density between adjacent areas in an image. Spatial resolution = The ability to distinguish between two closely spaced objects in an image.</p> Signup and view all the answers

Software manipulation of the image can improve its quality, even more than pixel density.

<p>True (A)</p> Signup and view all the answers

Explain why assigning multiple gray shades to each pixel is crucial for diagnostic value in digital images.

<p>Multiple gray shades allow for a nuanced contrast scale, enabling differentiation of subtle variations in tissue density. This detail is essential for accurate diagnosis and medical imaging applications.</p> Signup and view all the answers

CR plate readers are generally more portable than automatic x-ray film processors.

<p>False (B)</p> Signup and view all the answers

CCD systems are a type of DDR.

<p>True (A)</p> Signup and view all the answers

What is a major limitation of CR systems in ambulatory settings?

<p>Cassettes must be returned to the practice for processing, delaying image evaluation. (D)</p> Signup and view all the answers

What is the primary component of a CR cassette?

<p>Photostimulable phosphor (B)</p> Signup and view all the answers

Compared to replacing a damaged CR cassette, replacing a damaged ____ plate is considerably more expensive.

<p>DDR</p> Signup and view all the answers

In CR imaging, the latent image in the PSP is read out optically as ______ when the plate is stimulated by a laser.

<p>photostimulated luminescence</p> Signup and view all the answers

Name one advantage of CR systems compared to non-wireless digital imaging plates.

<p>CR cassettes are not tethered to a computer by a cable, allowing for greater flexibility in obtaining nonstandard views.</p> Signup and view all the answers

What are the two main reasons why CR is less popular in veterinary imaging compared to human imaging?

<p>Slower processing time compared to DDR systems and lack of workflow improvement over analog imaging.</p> Signup and view all the answers

Match the following components of the CR system to their functions:

<p>CR cassette = Holds the PSP plate PSP = Stores the latent image Laser scanner = Illuminates the PSP plate Photomultiplier tube = Converts visible light into electronic signal Digital file = Stores the digitized image</p> Signup and view all the answers

Match the type of DDR with its corresponding description:

<p>Indirect flat-panel detector = Uses an intensifying screen to convert x-rays into visible light. Direct flat-panel detector = Converts x-rays directly into an electrical signal. CCD system = Uses a charge-coupled device to capture x-rays and convert them into an image.</p> Signup and view all the answers

CR is known for its faster image acquisition compared to DDR systems.

<p>False (B)</p> Signup and view all the answers

Cesium iodide intensifying screens are more efficient in detecting x-rays compared to gadolinium oxysulfide screens.

<p>True (A)</p> Signup and view all the answers

Which of the following is NOT a characteristic of indirect flat-panel detectors?

<p>Converts x-rays directly into an electrical signal. (A)</p> Signup and view all the answers

What happens to the PSP plate after it has been read by the laser scanner?

<p>It is exposed to bright white light to reset it for the next exposure. (D)</p> Signup and view all the answers

Describe the process by which the latent image in the PSP plate is converted into a digital image.

<p>The PSP plate is illuminated by a laser, causing it to emit visible light. The light strikes a photomultiplier tube, which converts the light into an electronic signal. This signal is then digitized and stored as a digital file.</p> Signup and view all the answers

What is the primary advantage of DDR over CR systems?

<p>DDR systems provide instant image availability for quality control evaluation within a few seconds.</p> Signup and view all the answers

Which of the following technologies is increasingly replacing CR systems in veterinary medicine?

<p>Flat-panel systems (D)</p> Signup and view all the answers

Modern-day intensifying screens cause a significant amount of light diffusion.

<p>False (B)</p> Signup and view all the answers

What is the primary advantage of wireless DDR plates, especially in an equine setting?

<p>Wireless DDR plates eliminate the risk of tripping hazards caused by cables, particularly important in the equine setting.</p> Signup and view all the answers

Newer flat-panel detectors use a flexible ______ film as the base substrate for the thin-film transistor array.

<p>plastic</p> Signup and view all the answers

Match the following technologies with their primary application in veterinary radiography:

<p>CCD = Less common than CR or flat-panel DDR radiography CR = A fully developed technology, though less preferred than flat-panel systems Flat-panel DDR = Increasingly preferred over CR due to higher throughput and lower price Wireless DDR plates = Provide convenience and safety, especially in equine settings</p> Signup and view all the answers

In an indirect flat-panel detector, what converts visible light into an electronic signal?

<p>Photodiodes (D)</p> Signup and view all the answers

Direct flat-panel detectors utilize an intensifying screen to convert x-rays into visible light.

<p>False (B)</p> Signup and view all the answers

What is the primary advantage of direct flat-panel detectors over indirect ones?

<p>Direct flat-panel detectors eliminate the light diffusion that occurs in indirect systems, potentially resulting in improved image clarity and sharpness.</p> Signup and view all the answers

The size of a full-size imaging plate in an indirect flat-panel detector is typically approximately ______ cm × ______ cm.

<p>43 × 43</p> Signup and view all the answers

Match the terms related to flat-panel detectors with their respective descriptions:

<p>Photodiode = Converts visible light into an electronic signal Thin-film transistor array = Reads out the signal from the photodiodes and converts it to an electronic file Intensifying screen = Converts x-rays into visible light Amorphous selenium = Photoconductor used in direct flat-panel detectors to absorb x-rays and generate an electronic signal</p> Signup and view all the answers

What is the bit depth typically offered by most digital radiographic systems?

<p>10 to 16 bits</p> Signup and view all the answers

The human eye can distinguish more than 16,384 shades of gray.

<p>False (B)</p> Signup and view all the answers

What is the primary reason for the higher cost of flat-panel detectors compared to film-screen cassettes?

<p>The complex electronics required for signal processing and localization (B)</p> Signup and view all the answers

Study Notes

Digital Image File

  • A digital image file is a computer file containing information measured from a signal.
  • In diagnostic medical imaging, this signal can be x-ray emission, x-ray attenuation, sound waves, or radiofrequency emissions.
  • The DICOM format is a standard computer file format for medical images, similar to .jpeg and .tiff, denoted by the .dcm extension.
  • DICOM files include metadata, such as the manufacturer, date and time of acquisition, patient information, and other relevant parameters.
  • The DICOM format ensures consistency and interconnectivity between imaging devices.
  • Without a standard format, image viewing is limited to specific software, reducing convenience.

Components of a Digital Image

  • Digital image files are made up of individual picture elements called pixels, arranged in a matrix.
  • The number of pixels determines the matrix size and file size.
  • Larger pixel numbers equate to higher image spatial resolution (ability to detect smaller objects).
  • Pixel size is measured in microns or line pairs per mm.
  • Recommended standards for spatial resolution exist.
  • Images use binary notation to assign gray shades to pixels.
  • Bit depth determines the number of possible gray shades (more bits = more shades).
  • The bit depth of an image is directly related to its file size.

Digital Radiography Acquisition Hardware

  • Two main types are computed radiography (CR) and direct digital radiography (DDR).
  • Both use conventional x-ray tubes and tables.
  • CR systems use a flexible imaging plate (within a cassette) to record x-ray distribution.
  • DDR systems use rigid imaging plates or chips (no cassette).
  • Choosing the right system depends on the specific needs and workflow.

Computed Radiography (CR)

  • CR uses a cassette resembling a film cassette but containing a photostimulable phosphor (PSP) plate.
  • The PSP plate temporarily stores the x-ray pattern (latent image).
  • The plate is processed in a reader using a laser to stimulate luminescence and convert it to a digital image.
  • CR is still used in some applications due to portability and affordability of its cassettes.

Direct Digital Radiography (DDR)

  • DDR systems use detectors, such as flat-panel detectors or charged-coupled devices (CCDs) to directly convert x-rays into digital signals.
  • Indirect detectors use an intensifying screen to convert x-rays to light, which is then converted to an electronic signal.
  • Direct detectors convert x-rays directly to an electronic signal, without an intermediary step.
  • DDR systems offer faster image acquisition and potentially reduced radiation doses.

Charged-Coupled Device (CCD)

  • CCD chips are small, light-sensitive, and require an intensifying screen to convert x-rays to light; then light is converted to an electronic signal.
  • Image quality in CCD systems can be less than other types due to the multiple intermediary steps.
  • Therefore requiring the device to be large and non-portable.

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Description

Test your knowledge on diagnostic medical imaging concepts. This quiz covers various topics including image resolution, digital image storage, and the differences between imaging modalities. Challenge yourself and see how well you understand the fundamentals of medical imaging.

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