Questions and Answers
What is the most common target interaction?
Bremsstrahlung
What percentage of the primary beam, when set to 80-100 keV, is bremsstrahlung photons?
80-90%
All x-ray photons below 69 keV are _____________.
Bremsstrahlung
What does the term Bremsstrahlung mean in German?
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Why do Bremsstrahlung interactions occur?
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What happens during a Bremsstrahlung interaction?
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At what point is an x-ray photon produced?
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As the incident electron slows down, it loses ___________ energy.
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Does the incident electron ever reach the nucleus?
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Brems interactions ONLY occur when the incident electron interacts with the ________________.
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Why are Bremsstrahlung interactions considered to be heterogenetic/polyenergetic?
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What contributes to the differential absorption of x-rays within the patient's body?
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As incident electrons get closer to the nucleus of an atom, a (smaller/larger) deflection of the incident electron occurs.
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The larger the deflection, the (less/more) energy transferred to the photon.
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The energy of the brems photon is exactly the difference between the entering and exiting electron's ______________ energy.
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A Brem's photon with high energy will have a _______________ frequency and a ________________ wavelength.
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Photon's frequency is __________________ related to its wavelength.
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Bremsstrahlung is also known as ____________ or _____________ radiation.
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Operating at 90 kVp, we will have Brem's photons that range from __________ to __________ kVp.
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The majority of the Brem's photons will have approximately _________ of the max energy in a single exposure.
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What effect does binding energy have on Brem's interactions?
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The higher the atomic number of the target material, the more _________________ the Brem's photon becomes.
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Incident electron enters with 100 keV and leaves with 50 keV. How much energy is possessed by the brem's photon released in this interaction?
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An electron is deflected by a nucleus in a tungsten atom (atomic # 74). The electron had 125 keV initially and after interaction now had 45 keV. What is the energy of the brems x-ray as a result of this interaction?
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What makes up the y-axis on an x-ray emission spectrum?
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What makes up the x-axis of an x-ray emission spectrum?
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Brem's x-ray photons have a ___________________ spectrum.
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Study Notes
Bremsstrahlung Overview
- Bremsstrahlung, meaning "breaking" or "slowing" in German, is the most common target interaction in x-ray production.
- 80-90% of the primary beam at 80-100 keV is composed of Bremsstrahlung photons.
- All x-ray photons below 69 keV are classified as Bremsstrahlung, since characteristic photons require at least this energy to dislodge K shell electrons.
Mechanism of Bremsstrahlung Interactions
- Bremsstrahlung occurs when an incident electron is attracted to the positively charged nucleus, interacting with its electrostatic force field instead of colliding with another electron.
- During the interaction, the incident electron slows down, losing kinetic energy, which is converted into an x-ray photon when deflected by the nucleus.
- The incident electron never reaches the nucleus due to insufficient strength.
Photons Characteristics
- Brems photons are heterogeneous or polyenergetic, producing a wide range of x-ray photon energies due to varying distances from the nucleus during each interaction.
- A higher deflection results in a larger energy transfer to the photon, with high-energy Brems photons exhibiting higher frequency and shorter wavelength.
- Photon frequency is inversely related to wavelength; as frequency increases, wavelength decreases.
Energy Dynamics
- The energy of a Brems photon equals the difference between the entering and exiting kinetic energy of the incident electron.
- Operating at 90 kVp, Brems photons can range from 0 to 90 keV, with the majority possessing one-third of the maximum energy in a single exposure (e.g., at 90 kVp, the most common photons will be approximately 30 keV).
Influence of Atomic Number and Binding Energy
- Higher atomic number materials are more efficient in producing Brems photons, although they do not directly increase photon energy; that occurs during characteristic interactions.
- Binding energy does not affect Brems interactions, as these do not occur with electrons in orbit around the nucleus.
X-ray Emission Spectrum
- The y-axis of an x-ray emission spectrum represents the number of x-rays produced (mAs), indicating quantity.
- The x-axis reflects the energy level of the beam (kVp), representing quality.
- Bremsstrahlung x-ray photons create a continuous spectrum, indicating a variety of photons with differing energies below the maximum curve.
Example Calculations
- In an interaction where an electron enters with 100 keV and exits with 50 keV, the resulting Brems photon has an energy of 50 keV.
- For a tungsten atom (atomic # 74), if an electron with 125 keV is deflected and leaves with 45 keV, the energy of the emitted Brems x-ray is 80 keV, showcasing that atomic number does not influence the photon energy in this calculation.
Studying That Suits You
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Description
Test your understanding of Bremsstrahlung with these flashcards from Physics Lesson 20. Learn about its essential concepts, including its significance in x-ray production and percentages involved in beam interactions. This quiz will help reinforce your knowledge and grasp of this important topic in physics.
