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Questions and Answers
Which form of x-ray interaction occurs without any loss of energy?
Which form of x-ray interaction occurs without any loss of energy?
What is the primary consequence of the Compton Effect in an x-ray image?
What is the primary consequence of the Compton Effect in an x-ray image?
In which situation is Compton scattering more likely to occur?
In which situation is Compton scattering more likely to occur?
How does the wavelength of the scattered x-ray from the Compton Effect compare to that of the incident x-ray?
How does the wavelength of the scattered x-ray from the Compton Effect compare to that of the incident x-ray?
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Which x-ray interaction is primarily responsible for the graying of images called film fog?
Which x-ray interaction is primarily responsible for the graying of images called film fog?
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Which x-ray interaction results in the total absorption of an incident x-ray?
Which x-ray interaction results in the total absorption of an incident x-ray?
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What effect does increasing photon energy have on the probability of Compton Effect occurring?
What effect does increasing photon energy have on the probability of Compton Effect occurring?
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What happens to the outer shell electron during the Compton Effect?
What happens to the outer shell electron during the Compton Effect?
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What occurs to the K-shell electron during the photoelectric effect?
What occurs to the K-shell electron during the photoelectric effect?
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Which of the following statements about pair production is true?
Which of the following statements about pair production is true?
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What is the primary outcome of the photoelectric effect in terms of x-ray interaction?
What is the primary outcome of the photoelectric effect in terms of x-ray interaction?
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Which interaction is most likely to occur with tightly bound inner-shell electrons?
Which interaction is most likely to occur with tightly bound inner-shell electrons?
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How does photodisintegration affect x-ray imaging?
How does photodisintegration affect x-ray imaging?
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What is a consequence of Compton scatter in radiographic images?
What is a consequence of Compton scatter in radiographic images?
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Which photon energy level is necessary for pair production to take place?
Which photon energy level is necessary for pair production to take place?
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What describes the behavior of high-energy x-rays above 10 MeV?
What describes the behavior of high-energy x-rays above 10 MeV?
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Study Notes
X-Ray Interaction with Matter
- Five forms of x-ray interactions:
- Classical (or Coherent) Scattering
- Compton Effect
- Photoelectric Effect
- Pair Production
- Photodisintegration
Two Important Diagnostic X-Ray Interactions
- Compton Effect
- Photoelectric Effect
Classical (or Coherent) Scattering
- Also known as Classical, Rayleigh or Thomson Scattering
- Low-energy x-rays interact with atoms
- No energy loss but change in direction
- Wavelength of incident x-ray equals wavelength of scattered x-ray
- Little importance in diagnostic radiology
Classical (or Thompson) Scattering
- No energy loss, no ionization
- Low-energy x-rays (little importance)
- At 70 kVp, a small percentage of x-rays undergo this scattering
- Contributes to film fog
Compton Effect
- Moderate-energy x-rays interact with outer-shell electrons
- Ionization of the target atom (electron ejection)
- Change in x-ray direction, reduction in x-ray energy
- Scattered x-ray has a longer wavelength than the incident x-ray
- Reduces contrast in x-ray images
- Probability similar for soft tissue and bone
- Probability decreases with increased photon energy
- Probability decreases with increased kVp
Compton Effect details
- Reduces x-ray energy and ionizes atoms
- Scattered photon and secondary electron retain most energy
- Secondary interactions are possible
- Ultimately absorbed photoelectrically
Features of Compton Scattering
- Occurs most with outer-shell or loosely bound electrons
- Higher x-ray energy causes increased penetration
- Compton scattering increases relative to photoelectric scattering
- Increased penetration without interaction
- Reduced total Compton scattering
Photoelectric Effect
- Incident x-ray is totally absorbed during ionization of an inner-shell electron
- Incident photon disappears
- Inner-shell electron ejected (photoelectron)
- Total x-ray absorption interaction
- Kinetic energy of photoelectron is proportionally lower
- Characteristic x-rays produced (secondary radiation)
Photoelectric Effect Details
- Characteristic x-rays are lower energy than incident x-ray
- Probability function of photon energy and atomic number of target atom
Features of the Photoelectric Effect
- Most likely in inner-shell electrons
- Also with tightly bound electrons
- Occurs when x-ray energy is greater than electron binding energy
Pair Production
- High-energy x-rays interact with the nucleus
- Electrostatic field causes x-ray to disappear
- Two electrons are created:
- One positively charged (positron)
- One negatively charged (electron)
- Requires 1.02 MeV photon
- Not important in diagnostic x-ray
Photodisintegration
- High-energy x-rays (~10 MeV) interact with nucleus
- Absorbed by nucleus
- Nucleus excitation, nucleon or other nuclear material is released
- Not important in diagnostic x-ray
Differential Absorption
- Compton and photoelectric effects are crucial interactions in diagnostic x-ray
- Scattered x-rays contribute to film fog (generalized image dulling)
- Techniques/apparatus reduce the amount of scattered x-rays reaching the film
- Photoelectrically interacted x-rays provide diagnostic info
- X-rays that penetrate are radiolucent (appear dark/black)
- Those absorbed are radiopaque (appear bright/white)
- Image dependent on difference between absorbed and non-absorbed x-rays (differential absorption)
- Lower kVp increases differential absorption but increases patient radiation
- A compromise is needed for each exam
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Description
Explore the various forms of x-ray interactions with matter, including Classical Scattering, the Compton Effect, and the Photoelectric Effect. This quiz covers fundamental concepts essential for understanding diagnostic radiology. Test your knowledge on the mechanisms behind these interactions and their significance in medical imaging.
