Mock Exam Deck Flashcards
What is the difference between excitation and ionisation?
Excitation: When an electron is moved from a lower energy level to a higher one within the atom. Ionisation: When an electron is removed completely from the atom.
What energy is required to initiate an Lα transition in molybdenum?
At least 2670 eV is required to initiate an Lα transition.
Why is the energy released during de-excitation referred to as a “characteristic” photon?
The energy is ‘characteristic’ because the difference between energy levels in an atom is unique, meaning the photon energy is specific to that atom.
Define a heterogeneous beam and half-value layer.
Heterogeneous beam: A beam that consists of photons with different energies. Half-value layer: The thickness of material required to reduce the intensity of the beam by half.
What are the two main processes of x-ray photon production?
Bremsstrahlung: Caused by the interaction between an electron and the nucleus, where energy is released as a photon. Characteristic radiation: Occurs when a thermionic electron ejects an inner-shell electron, and another electron drops into its place, releasing a photon.
What happens in the ‘space charge limited’ and ‘saturated’ regions of x-ray production?
Space charge limited region: Not all thermionic electrons are accelerated to the anode. Saturated region: All thermionic electrons are accelerated, making kVp and mAs independent.
What is the purpose of tube voltage and filament current?
Tube voltage (kVp): Accelerates electrons from the cathode to the anode. Filament current (A): Heats the filament to produce thermionic emission of electrons.
Why must the x-ray filament have a large surface area and low work function?
A large surface area helps electrons escape the filament. A low work function requires less energy to produce thermionic emission.
Why does ‘Spectrum 2’ have no characteristic spikes in the x-ray spectrum?
The tube voltage is too low to ionise the atoms and cause de-excitation, so no characteristic x-rays are produced.
How does increasing filtration affect the x-ray spectrum?
The height (quantity) of the curve decreases. The mode (energy) of the curve increases. The minimum energy of photons increases.
Compare the performance of small and large anode angles in x-ray tubes.
Small angle: Smaller apparent focal spot, reduced field coverage, poor power loading, increased heel effect. Large angle: Larger focal spot, increased field coverage, good power loading, decreased heel effect.
What is emitted during alpha, beta-positive, beta-negative, and gamma decay?
Alpha decay: Two protons and two neutrons. Beta-positive decay: A positron. Beta-negative decay: An electron. Gamma decay: A photon of energy.
What does ALARA stand for, and who does it protect?
ALARA stands for As Low As Reasonably Achievable. It protects patients by minimizing radiation exposure to the lowest necessary level.
What is the difference between somatic and genetic effects of radiation?
Somatic effects: Appear in the individual exposed to radiation. Genetic effects: Appear in the offspring of the exposed individual.
What are the three principles of radiation protection?
Justification: Benefit must outweigh the risk. Optimization: Keep exposure as low as reasonably achievable (ALARA). Limitation: Set limits for different groups’ radiation exposure.
