General Questions1 Flashcards
What are isotopes?
Isotopes are nuclides with the same atomic number but different atomic mass.
Where does an electron move from when an Mα photon is emitted?
The electron moves from the L-shell to fill the M-shell vacancy.
What is the dose at 2m from an x-ray source if it is 10mSv at 1m?
The dose at 2m would be 2.5 mSv.
What effect do small target angles have?
Small target angles result in a smaller apparent focus and a more pronounced anode heel effect.
What is a characteristic photon?
A photon emitted when an electron ‘falls’ from one shell to another within an atom. The energy difference between the shells is unique to each type of atom.
What is the relationship between tube current and filament current?
The filament current heats the filament to produce electrons, which form the tube current. To increase tube current, filament current must be increased.
Why can isotopes be radioactive?
Isotopes have an imbalance in their proton-to-neutron ratio, which can cause the nucleus to be unstable and radioactive.
What is emitted in alpha, beta, and gamma decay?
Alpha: Two protons and two neutrons. Beta: An electron (negative or positive). Gamma: A photon of energy.
What is Compton scatter?
Compton scatter occurs when a photon collides with an outer electron and ejects it, changing the photon’s direction and energy.
What is the photoelectric effect?
The x-ray photon imparts all its energy to an inner-shell electron, ejecting it from the atom. The probability of this effect depends on the proton number of the attenuator.
What is the difference between total attenuation coefficient and total mass attenuation coefficient?
Total attenuation coefficient changes with material density. Total mass attenuation coefficient is independent of density.
What is the anode heel effect?
The anode heel effect is the reduction in x-ray intensity from the cathode side to the anode side of the tube.
What is meant by the quality and quantity of an x-ray beam?
Quality refers to the penetrating power of the x-ray beam. Quantity refers to the number of photons in the x-ray beam.
What is effective photon energy?
Effective photon energy is the energy of a homogeneous beam that has the same penetrating power as the heterogeneous beam being described.
What is the half-value layer?
The half-value layer is the thickness of a material required to reduce the x-ray beam’s intensity by 50%.
What are the advantages and disadvantages of a small anode angle with a broad focus filament?
Advantages: Small effective focal spot, good heat distribution. Disadvantages: Poor field of view, increased heel effect.
How does the emission spectrum of a tungsten target look with no added filtration and 90 kVp?
The spectrum shows Bremsstrahlung radiation with characteristic peaks and a maximum photon energy of 90 keV.
