Digital Radiography Quiz
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Questions and Answers

What effect does increasing the grid ratio have on scatter and exposure?

  • Reduces scatter without affecting exposure
  • Increases scatter and decreases exposure
  • Reduces scatter but requires decreased exposure
  • Reduces scatter but requires increased exposure (correct)

How does filtration affect the quality of the x-ray beam?

  • Reduces beam quality and increases scatter
  • Increases beam quality and enhances scatter
  • Decreases beam quality and reduces patient dose
  • Increases beam quality and reduces patient dose (correct)

What does the Inverse Square Law state about intensity?

  • Intensity is constant regardless of distance
  • Intensity is directly proportional to the square of the distance
  • Intensity is inversely proportional to the distance
  • Intensity is inversely proportional to the square of the distance (correct)

What is a common cause of artifacts in digital imaging?

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

Which of the following strategies can effectively reduce patient dose while maintaining image quality?

<p>Use higher kVp with lower mAs (B)</p> Signup and view all the answers

What effect does smaller pixel size have on spatial resolution?

<p>It increases spatial resolution. (A)</p> Signup and view all the answers

What is the primary material used in indirect digital radiography (DR)?

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

What is the formula for calculating Heat Units (HU) in an x-ray system?

<p>HU = kVp × mAs × generator factor (C)</p> Signup and view all the answers

Which of the following factors can improve contrast resolution?

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

Which characteristic is true regarding mAs in x-ray imaging?

<p>mAs affects beam intensity but not quality. (C)</p> Signup and view all the answers

What relationship does increasing kVp have on beam penetrability and image contrast?

<p>Increases beam penetrability and decreases image contrast. (A)</p> Signup and view all the answers

What is DQE in the context of digital radiography?

<p>Detective Quantum Efficiency (B)</p> Signup and view all the answers

Which of the following factors is influenced by lowering kVp in radiographic imaging?

<p>Increases patient dose and improves contrast. (D)</p> Signup and view all the answers

Flashcards

Pixel Size and Spatial Resolution

Smaller pixel size improves the ability to see details (spatial resolution), but might increase radiation dose to the patient.

Matrix Size vs. Pixel Count

Matrix size is the overall grid; more pixels per square area gives more detail. Pixel count = total pixels in the image. You calculate it by multiplying the number of rows by the number of columns in the matrix.

Detector Element (DEL)

The smallest part of a digital detector that collects x-ray information, directly affecting spatial resolution in digital systems.

Indirect vs. Direct DR

Indirect DR uses amorphous silicon, while direct DR uses amorphous selenium. Both capture x-rays but differ in how they produce the digital image.

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Window Width/Level

Window width controls the range of gray shades shown, while window level controls the center of the range. Both adjust image contrast.

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Bremsstrahlung Radiation

X-rays produced when electrons slow down while interacting with the nucleus.

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kVp and Beam Penetrability

Higher kVp values allow x-rays to penetrate deeper into the body, impacting image contrast.

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Contrast Resolution

The ability to differentiate between tissues with similar densities.

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Bremsstrahlung X-rays

The most common type of X-rays used in diagnostic imaging, produced by electrons slowing down.

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X-ray Filtration

Filtering X-rays to improve image quality and reduce patient dose by removing low-energy X-rays.

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Inverse Square Law

The intensity of radiation is inversely proportional to the square of the distance from the source.

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Grid Ratio

A measure of a diagnostic grid's effectiveness in reducing scatter radiation; calculated by dividing the height of the grid strips by the distance between them.

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Magnification Factor

The ratio of the image size to the object size, or the source-to-image distance (SID) divided by the source-to-object distance (SOD).

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Study Notes

Digital Radiography (DR)

  • Pixel Size and Spatial Resolution: Smaller pixel size improves spatial resolution but might increase patient dose.
  • Matrix Size and Pixel Count: Calculating the number of pixels in a matrix is important.
  • Spatial Resolution Limitation: Limited by the Detector Element (DEL) size in digital systems.
  • Capture Systems:
    • Indirect DR uses amorphous silicon.
    • Direct DR uses amorphous selenium.
  • Pre and Post-Processing:
    • Window width vs. window level
    • Histogram
    • Flatfielding
    • Interpolation
  • Image Characteristics:
    • Improved spatial resolution with higher matrix size and smaller pixel size.
    • Signal processing often involves reusable receptors.

Radiographic Physics and Image Quality

  • Imaging System:
    • Small vs. Large Filament
    • Filament Material
    • Parts of the Anode side of the x-ray tube
    • Parts of the Cathode side of the x-ray tube
    • Comparing single phase, three phase, and high frequency systems
  • Heat Unit Calculation: Formula for calculating heat units.

Radiation Safety and Beam Characteristics

  • Radiation Safety: Leakage radiation from lead-lined housing should not exceed 100 mR/hr at 1 meter.
  • Beam Characteristics:
    • Increased kVp increases beam penetrability and decreases image contrast.
    • mAs impacts beam intensity but not quality.
    • Off-focus radiation
    • MTF (Modulation Transfer Function)
    • DQE (Detective Quantum Efficiency)
  • Foreshortening vs elongation (likely related to image distortion).

Contrast and Spatial Resolution

  • Definitions:
    • Contrast Resolution: Differentiating objects of similar density.
    • Spatial Resolution: Distinguishing objects close together.
  • Factors Influencing Image Quality:
    • Tight collimation, patient compression, and lower kVp improve contrast resolution.
    • Lowering kVp increases patient dose but improves contrast.

X-Ray Production and Interaction

  • X-Ray Interactions: Bremsstrahlung is produced when electrons are decelerated near the nucleus.
  • Characteristic X-Rays: Produced when an inner-shell electron is ejected, creating a vacancy.

Filtration

  • Filtration increases beam quality (hardening) and reduces patient dose

Grids and Scatter Control

  • Grid Use:
    • Grid ratio = height of grid strips/interspace width
    • Higher grid ratios reduce scatter but require increased exposure (mAs).
    • Influenced by kVp, field size, and patient thickness.

Artifacts in Digital Imaging

  • Common Causes: Pixel failure, dust, scratches, or incomplete erasure.
  • Corrections: Dead pixels are corrected using interpolation.
  • Image Artifacts: Can result from improper collimation, patient positioning, incorrect histogram selection.

Radiation Dose and Intensity

  • Inverse Square Law: Intensity is inversely proportional to the square of the distance from the source (1/r^2).
  • Dose Reduction Strategies: Using higher kVp with lower mAs to reduce patient dose without compromising image quality.

Mathematical Problems

  • Magnification Factor: formula relating Magnification Factor, Source Image Distance (SID), Object Image Distance (OID) and Object Size
  • Grid Conversion: mAs adjustments are proportional to grid ratio changes.

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Description

Test your knowledge on digital radiography concepts, including pixel size, spatial resolution, and capture systems. Dive into the details of imaging systems and the physics that influence image quality. This quiz will challenge your understanding of both pre and post-processing techniques used in modern radiography.

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