Radiography Exam Radiation Physics & Principles 2 — Questions and Answers
Question 1: What is the primary purpose of added filtration in an x-ray tube assembly?
- Increase mAs
- Remove low-energy photons that contribute only to patient dose (Correct answer)
- Increase beam intensity
- Reduce scatter reaching the detector
Correct answer: Remove low-energy photons that contribute only to patient dose
Added filtration removes low-energy (soft) x-rays that would be absorbed by the patient without contributing to image formation.
Question 2: Half-value layer (HVL) is used to describe which characteristic of an x-ray beam?
- Beam divergence
- Beam quality (penetrating ability) (Correct answer)
- Beam quantity (number of photons)
- Focal spot size
Correct answer: Beam quality (penetrating ability)
HVL is the thickness of a specified material that reduces beam intensity by half, describing the beam's penetrating quality.
Question 3: Compton scatter is most likely to occur when x-ray photons interact with which type of electrons?
- Inner-shell (K) electrons
- Nucleus-bound neutrons
- Outer-shell (valence) electrons (Correct answer)
- Free protons
Correct answer: Outer-shell (valence) electrons
Compton scatter involves interaction between x-ray photons and loosely bound outer-shell electrons, producing a scattered photon and a recoil electron.
Question 4: Which factor has the greatest influence on the quantity (number of photons) of x-rays produced?
- kVp
- SID
- mAs (Correct answer)
- Filtration
Correct answer: mAs
mAs (milliampere-seconds) directly controls the number of x-ray photons produced and thus beam quantity.
Question 5: What is the primary composition of the x-ray beam produced at the anode?
- Mostly characteristic radiation
- Mostly bremsstrahlung radiation (Correct answer)
- Equal amounts of both
- Mostly coherent scatter
Correct answer: Mostly bremsstrahlung radiation
Bremsstrahlung (braking) radiation makes up approximately 80–90% of the useful x-ray beam at diagnostic energies.
Question 6: Which of the following describes the line-focus principle in x-ray tube design?
- Using a curved anode to focus the beam
- Angling the anode target to create a smaller effective focal spot (Correct answer)
- Placing a lens in the beam path
- Increasing the filament current to sharpen the beam
Correct answer: Angling the anode target to create a smaller effective focal spot
The line-focus principle uses an angled anode target so the effective (projected) focal spot is smaller than the actual focal spot, improving image sharpness.
Radiography Exam Radiation Physics & Principles 2
What is the primary purpose of added filtration in an x-ray tube assembly?