Podcast
Questions and Answers
What is the primary function of intensifying screens in radiography?
What is the primary function of intensifying screens in radiography?
- To protect the film from light
- To enhance image contrast
- To sandwich the film for processing
- To reduce the required exposure time (correct)
When examining denser parts of the body, which of the following best describes grid usage?
When examining denser parts of the body, which of the following best describes grid usage?
- Grids are ineffective in digital image acquisition
- Grids increase the amount of secondary radiation produced
- Focused grids are designed to function best at a specific distance (correct)
- Grids should always be used regardless of body density
What factor is NOT considered when selecting the mAs for exposure in radiography?
What factor is NOT considered when selecting the mAs for exposure in radiography?
- Kilovoltage settings
- Type of image-acquisition device
- Grid factor
- Patient age (correct)
How can one effectively handle grid cut-off during radiographic procedures?
How can one effectively handle grid cut-off during radiographic procedures?
Which statement about digital image capture is true?
Which statement about digital image capture is true?
What is subject contrast primarily influenced by?
What is subject contrast primarily influenced by?
Which of the following factors contributes to subjective contrast?
Which of the following factors contributes to subjective contrast?
What is the relationship between magnification and focus-to-object distance (FOD)?
What is the relationship between magnification and focus-to-object distance (FOD)?
Which of the following does NOT affect radiographic (objective) contrast?
Which of the following does NOT affect radiographic (objective) contrast?
What type of unsharpness is caused by the geometry of the X-ray source?
What type of unsharpness is caused by the geometry of the X-ray source?
What does radiographic contrast measure?
What does radiographic contrast measure?
Which factor is least likely to affect image sharpness in radiography?
Which factor is least likely to affect image sharpness in radiography?
Which of the following best defines subjective contrast?
Which of the following best defines subjective contrast?
What term refers to the difference in density between structures of interest within an image?
What term refers to the difference in density between structures of interest within an image?
How is subject contrast defined in the context of radiographic imaging?
How is subject contrast defined in the context of radiographic imaging?
What happens to X-rays as they pass through the body?
What happens to X-rays as they pass through the body?
In radiographic imaging, what is the term for the amount of signal detected in the image receptor?
In radiographic imaging, what is the term for the amount of signal detected in the image receptor?
Which type of imaging captures images digitally using systems like computed radiography?
Which type of imaging captures images digitally using systems like computed radiography?
What does image density refer to in radiographic terminology?
What does image density refer to in radiographic terminology?
What characterizes a low-contrast image?
What characterizes a low-contrast image?
Which factor does NOT influence subject contrast in radiographic imaging?
Which factor does NOT influence subject contrast in radiographic imaging?
What effect does increasing focal spot size have on geometric unsharpness?
What effect does increasing focal spot size have on geometric unsharpness?
Which of the following methods can help reduce movement unsharpness during an exposure?
Which of the following methods can help reduce movement unsharpness during an exposure?
Which of the following exposure factors directly determines the amount of radiation used?
Which of the following exposure factors directly determines the amount of radiation used?
What is the preferred kilovoltage range used in diagnostic radiography for most examinations?
What is the preferred kilovoltage range used in diagnostic radiography for most examinations?
Why is a kilovoltage of 120 kVp often used in chest radiography?
Why is a kilovoltage of 120 kVp often used in chest radiography?
What is the standard focus-to-film distance (FFD) used in most radiographic examinations?
What is the standard focus-to-film distance (FFD) used in most radiographic examinations?
How does increasing the kilovoltage affect exposure time?
How does increasing the kilovoltage affect exposure time?
What type of imaging technology uses computed radiography (CR) and direct digital radiography (DDR)?
What type of imaging technology uses computed radiography (CR) and direct digital radiography (DDR)?
Flashcards
Radiographic Image Formation
Radiographic Image Formation
X-rays, originating from a specific area of the X-ray tube, pass through the body. The absorbed and unabsorbed X-rays create an image on the detector.
Image Density
Image Density
The degree of 'blackening' in a radiographic image; amount of signal recorded.
Patient Density
Patient Density
The mass per unit volume of body structures and their absorption of X-rays.
Radiographic Contrast
Radiographic Contrast
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Subject Contrast
Subject Contrast
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X-ray Attenuation
X-ray Attenuation
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Optical Density
Optical Density
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High Contrast Image
High Contrast Image
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Magnification
Magnification
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Geometric Unsharpness
Geometric Unsharpness
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Image Distortion
Image Distortion
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Image Sharpness
Image Sharpness
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Factors affecting Radiographic Contrast
Factors affecting Radiographic Contrast
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Movement Unsharpness
Movement Unsharpness
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Exposure Time
Exposure Time
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mAs
mAs
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kVp
kVp
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FFD
FFD
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Grids
Grids
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Exposure Factors
Exposure Factors
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What is the formula for calculating mAs at different FFDs?
What is the formula for calculating mAs at different FFDs?
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What are intensifying screens?
What are intensifying screens?
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Explain the concept of grid cut-off.
Explain the concept of grid cut-off.
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What is the purpose of a grid in radiography?
What is the purpose of a grid in radiography?
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What factors influence the selection of mAs?
What factors influence the selection of mAs?
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Study Notes
Radiographic Image Formation
- X-rays are produced in a small area of the X-ray tube.
- X-rays diverge outwards in straight lines.
- X-rays pass through the body, some are absorbed by organs/structures, some pass through.
- Detection devices are used to create the image.
Density
- Patient/physical density: Mass per unit volume of structures. Absorption characteristics.
- Image density: Amount of signal detected in the image receptor. Often described as 'blackening'. Optical density if measured by densitometer.
- Diagnostic density: Small area of pathology in an image.
Projection and View
- Radiographic image is a projection of the object.
Density and Contrast
- Density: Degree of 'blackening' in an image. Greater radiation, greater density.
- Photographic density/optical density: Term used when capturing an image on photographic film.
- Digital Image Density: Term used with digital capture systems (CR, DR).
- Contrast: Difference in density between structures of interest. Low contrast shows little difference, high contrast shows large difference.
Types of Contrast
- Subject contrast: Feature of the object under examination.
- Radiographic contrast: Difference in optical density on different parts of the processed film.
- Subjective contrast: Personal appreciation of the differences in optical density.
Density and Contrast (continued)
- Subject Contrast: X-rays are attenuated by different amounts based on tissue thickness, density, and atomic number.
- Differences in intensity of the emergent beam are called subject/radiation contrast.
Radiographic Image: Magnification and Distortion
- Magnification: Image size/object size = object distance/image distance (FFD/FOD)
- Image distortion: Occurs when object and film are not parallel. Different parts of the object have varying degrees of magnification.
- Image sharpness/unsharpness: Aims to produce the sharpest possible image. Unsharpness is caused by several factors: geometric, movement, absorption, photographic/acquisition factors.
Radiographic Image: Movement Unsharpness
- Movement during exposure causes unsharpness.
- Increased sharpness achieved using shorter exposure times (lower mAs with higher kVp.)
Image Acquisition and Display
- Several methods: conventional film/screen, fluoroscopy/fluorography, digital imaging (CR, DDR).
Exposure Factors
- Exposure factors need to be selected for each radiograph.
- Factors depend on region being examined (thickness, density, pathology).
- Milliampere-seconds (mAs): Intensity of X-ray radiation; product of tube current (mA) and exposure time (seconds).
- Kilovoltage (kVp): Penetrating ability of the X-ray beam.
- Focus-to-film distance (FFD): Distance between focal spot and image receptor.
Intensifying Screens
- Used in conjunction with film. Films sandwiched between screens.
- Enhance image quality.
Secondary Radiation Grid
- Used for dense body parts.
- Grids have a lattice to reduce scattered radiation.
- Grid ratio: ratio of lead-to-spacing.
- Useful to improve image contrast.
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