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Questions and Answers
What is the recommended lead equivalent thickness for glass used as a protective shield?
What is the recommended lead equivalent thickness for glass used as a protective shield?
What is the primary purpose of using personal dosimeters in a controlled area?
What is the primary purpose of using personal dosimeters in a controlled area?
In patient preparation for imaging, how long should food be withheld before the procedure?
In patient preparation for imaging, how long should food be withheld before the procedure?
What is the function of structural shielding in X-ray facilities?
What is the function of structural shielding in X-ray facilities?
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What should be done with personal dosimeters when not in use?
What should be done with personal dosimeters when not in use?
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What role does the tungsten target play in X-ray generation?
What role does the tungsten target play in X-ray generation?
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Which of the following is a requirement for the safe operation of radiographic equipment?
Which of the following is a requirement for the safe operation of radiographic equipment?
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What is a primary legal requirement for personnel involved in radiographic exposure?
What is a primary legal requirement for personnel involved in radiographic exposure?
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Which step is NOT essential for preparing animals for radiographic exposure?
Which step is NOT essential for preparing animals for radiographic exposure?
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Which component is crucial in controlling the direction of the X-ray beam?
Which component is crucial in controlling the direction of the X-ray beam?
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What is one of the primary advantages of digital radiography?
What is one of the primary advantages of digital radiography?
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Which principle states that radiography should only be performed if there is a definite clinical justification?
Which principle states that radiography should only be performed if there is a definite clinical justification?
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What does ALARA stand for in radiation safety?
What does ALARA stand for in radiation safety?
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What characterizes stochastic effects of radiation exposure?
What characterizes stochastic effects of radiation exposure?
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What is a key disadvantage of digital radiography?
What is a key disadvantage of digital radiography?
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Which of the following is a component of limiting occupational exposure?
Which of the following is a component of limiting occupational exposure?
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Which of these describes a deterministic effect of radiation?
Which of these describes a deterministic effect of radiation?
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What constitutes a controlled area in radiation protection?
What constitutes a controlled area in radiation protection?
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What effect does increasing the kVp have on the x-ray beam?
What effect does increasing the kVp have on the x-ray beam?
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What does mAs represent in x-ray imaging?
What does mAs represent in x-ray imaging?
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What is the purpose of the film focal distance (FFD)?
What is the purpose of the film focal distance (FFD)?
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Which factor increases the likelihood of absorption and contrast in radiographic images?
Which factor increases the likelihood of absorption and contrast in radiographic images?
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What does the term 'latent image' refer to in radiography?
What does the term 'latent image' refer to in radiography?
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What is the primary disadvantage of using intensifying screens in radiography?
What is the primary disadvantage of using intensifying screens in radiography?
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How does scatter radiation affect the quality of a radiographic image?
How does scatter radiation affect the quality of a radiographic image?
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What role do photodiodes play in digital radiography?
What role do photodiodes play in digital radiography?
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What happens to the quantity of radiation at a point as the film focal distance (FFD) increases?
What happens to the quantity of radiation at a point as the film focal distance (FFD) increases?
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In digital radiography, what process is used to delete the latent image after exposure?
In digital radiography, what process is used to delete the latent image after exposure?
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Which material is commonly used in the emulsion layer of radiographic film?
Which material is commonly used in the emulsion layer of radiographic film?
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What would likely happen to the contrast of the image if the atomic number of tissues being imaged decreases?
What would likely happen to the contrast of the image if the atomic number of tissues being imaged decreases?
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What is a primary benefit of using flat panel detectors in digital radiography?
What is a primary benefit of using flat panel detectors in digital radiography?
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Which factor affects the intensity of the x-ray beam during exposure?
Which factor affects the intensity of the x-ray beam during exposure?
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Study Notes
Physics of Radiography and Radiation Safety
- Radiography uses X-rays to create images of internal structures.
- The generation of X-rays involves converting electrical current to electrons, then photons.
- X-ray photons interact differently with different tissues, creating varying shades of grey (contrast) on the image.
- Radiation is a biological hazard and precautions are necessary to minimize occupational exposure.
Learning Objectives
- Students will understand the process of X-ray generation from standard equipment.
- Students will learn the requirements for safe operation of radiographic equipment.
- Students will understand the legal requirements for personnel protection during radiographic exposure.
- Students will be familiar with the preparation steps for animals undergoing radiographic procedures.
X-ray Generation
- X-ray machines consist of a generator, tube, and an imaging device (e.g., film, screen or digital detector)
- Photons emitted from the generator are targeted at the patient.
- The patient's anatomy creates different levels/intensity of contrast on the imaging device.
- The output image of the patient is captured on film, screen, or a digital detector.
X-ray Tube
- Tungsten target acts as the anode. This target emits the x-ray photons.
- A cathode produces the electrons necessary to generate the X-rays.
- The x-ray beam is collimated (shaped) to better target the patient.
Exposure Settings
- kVp (Peak Kilovoltage): Controls the energy of electrons, affecting the penetration power of the X-ray beam. Increasing kVp leads to more photons and increased penetration.
- mA (Milliamperage): Controls the number of electrons produced, increasing the intensity/quantity of the X-ray beam.
- Time (Seconds): Determines the duration the X-ray beam is on, also influencing the intensity/quantity.
- FFD (Film Focal Distance): The distance between the X-ray tube and the imaging device. It influences the spreading of the beam and affects density and contrast.
mA and Time
- mA × time (mAs): Reflects the intensity of the X-ray beam.
- Increasing mAs leads to more X-ray photons and greater intensity.
Film Focal Distance (FFD)
- FFD = the distance between the focal spot of the X-ray tube and the image receptor.
- The radiation intensity is inversely proportional to the square of the FFD (1/FFD²).
Interaction of X-rays with Matter
- Absorption: Energy is transferred to the patient, contrast between tissues is created. Absorption increases with increasing atomic number of the material.
- Scatter: Energy is deflected away from the patient, reducing image quality and potentially harming the radiographer. Scatter is worse with higher kVp.
Interaction of X-rays with Film/Screen Detectors
- Image recorded on film or intensifying screens is a result of how X-ray photons interact and are absorbed along with differing amounts of film blackening, resulting in differing degrees of contrast.
- Overexposure: excessive film blackening.
- Underexposure: insufficient film blackening.
Interaction of X-rays with Various Tissues
- Gas: appears very dark or black on a radiograph.
- Fat: appears grey.
- Soft tissue/fluid: appears intermediate grey.
- Bone: appears white.
- Metal: appears very white or bright white.
Recording and Displaying the Image
- X-ray film uses silver bromide crystals. The photon interacts with the crystals, causing them to become latent images that can be developed.
- Chemical processing converts the latent image to a viewable image.
- More modern systems use intensifying screens and cassettes which reduce occupational exposure, improve image quality, and reduce exposure times.
Digital Radiography
- Digital radiography uses image plates that are sensitive to X-rays. This sensitive plate is scanned, converting energy into a digital format, immediately accessible on a monitor.
Radiation Safety
- Work practices should be followed for proper radiation safety precautions.
- ALARA technique: radiation is kept as low as reasonably achievable for personnel and the patient.
- Shielding, and distance control reduce exposure to personnel.
Principles of Radiation Protection
- Radiography should only be used when necessary.
- Exposure of personnel should be kept to a minimum.
- No legal dose limits should be exceeded.
Limiting Occupational Exposure
- Time: Limit exposure time with staff rotation.
- Distance: Position personnel at a safe distance, and to maximize the distance from the machine to the operator and patient.
- Shielding: Use appropriate personal protective equipment (PPE) and structural shielding.
Patient Preparation
- Elective procedures vs. emergencies: preparation varies between electivity vs. emergency, including food, positioning and restraint, and coat cleaning.
- Imaging type, view(s), and patient positioning should be planned before the procedure.
Monitoring Personal Exposure
- Personal dosimeters are used to monitor radiation exposure levels for staff. Badges are worn, stored outside areas, and changed regularly.
Summary
- X-ray images are created from electrical impulses converting into photons and interacting with tissue.
- Tissue density affects how photons interact causing varying shades of grey, and ultimately the visible image.
- Radiation safety is crucial to prevent occupational exposure dangers.
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Description
This quiz covers the fundamental principles of radiography, specifically focusing on X-ray generation and radiation safety protocols. Students will learn about the processes involved in X-ray imaging and the necessary precautions for minimizing exposure. Essential legal and operational requirements for safe radiographic practices will also be examined.
