Orris
attachment

100 MCQs provide me for this syllabus medium and hard level tomorrow is my exam

Reading File
Finding Sources
The library doesn't have a dedicated radiography/X-ray technology textbook — this is a technical radiology syllabus (not clinical medicine). I'll generate the 100 MCQs directly from my comprehensive knowledge of X-ray physics and equipment technology, covering all 5 modules at medium and hard difficulty.

100 MCQs — X-Ray Technology

Modules I–V | Medium & Hard Level

MODULE I: X-Ray Tube, Production of X-Rays, Types of X-Ray Tube

Q1. The efficiency of X-ray production in a tungsten target at 100 kVp is approximately:
  • A) 0.1%
  • B) 1%
  • C) 5%
  • D) 10%
Answer: B) 1% Efficiency ≈ 1% at 100 kVp; the remaining 99% is converted to heat.
Q2. Which property of tungsten makes it the preferred anode material?
  • A) High atomic number (74) and high melting point (3422°C)
  • B) Low atomic number and high thermal conductivity
  • C) Low density and high melting point
  • D) High atomic number and low boiling point
Answer: A) High atomic number (74) and high melting point (3422°C)
Q3. In a Coolidge tube, the electron source is:
  • A) A gas discharge
  • B) A thermionic emission filament
  • C) A photoelectric cathode
  • D) A field emission tip
Answer: B) A thermionic emission filament
Q4. The line focus principle is used to:
  • A) Increase actual focal spot size while keeping effective focal spot small
  • B) Decrease actual focal spot size while increasing effective focal spot
  • C) Eliminate off-focus radiation
  • D) Improve heat dissipation in stationary anodes
Answer: A) Increase actual focal spot size while keeping effective focal spot small The angled anode allows a larger area for heat distribution while projecting a smaller effective focal spot.
Q5. The heel effect causes X-ray intensity to be:
  • A) Greater on the anode side than the cathode side
  • B) Greater on the cathode side than the anode side
  • C) Equal on both sides
  • D) Greater at the center of the beam
Answer: B) Greater on the cathode side than the anode side Anode self-absorption reduces intensity toward the anode end.
Q6. A rotating anode X-ray tube rotates at approximately:
  • A) 100–200 rpm
  • B) 500–1000 rpm
  • C) 3000–10,000 rpm
  • D) 20,000–50,000 rpm
Answer: C) 3000–10,000 rpm Standard rotation is ~3000 rpm; high-speed anodes reach 9000–10,000 rpm.
Q7. The space charge effect refers to:
  • A) The positive charge accumulated on the anode
  • B) The cloud of electrons near the filament that limits emission
  • C) The charge stored in the capacitor bank
  • D) The electrostatic repulsion between X-ray photons
Answer: B) The cloud of electrons near the filament that limits emission
Q8. Off-focus (extra-focal) radiation originates from:
  • A) Electrons hitting the glass envelope
  • B) Electrons striking areas of the anode outside the focal spot
  • C) Backscattered X-rays from the patient
  • D) Leakage through the tube housing
Answer: B) Electrons striking areas of the anode outside the focal spot
Q9. In a gas-filled X-ray tube (ion tube), the electron stream is produced by:
  • A) Thermionic emission from a tungsten filament
  • B) Ionisation of residual gas molecules
  • C) Photoelectric emission
  • D) Secondary electron emission from the anode
Answer: B) Ionisation of residual gas molecules
Q10. The heat unit (HU) for a single-phase full-wave rectified generator is calculated as:
  • A) HU = kVp × mA × s
  • B) HU = kVp × mA × s × 1.35
  • C) HU = kVp × mA × s × 1.41
  • D) HU = kVp² × mA × s
Answer: A) HU = kVp × mA × s For three-phase, multiply by 1.35 (6-pulse) or 1.41 (12-pulse).
Q11. The anode angle in most diagnostic X-ray tubes ranges between:
  • A) 5°–10°
  • B) 7°–17°
  • C) 20°–30°
  • D) 45°–60°
Answer: B) 7°–17°
Q12. Which of the following best describes the function of the focusing cup (cathode assembly)?
  • A) It accelerates electrons toward the anode
  • B) It focuses the electron beam onto a small area of the anode
  • C) It filters out low-energy X-rays
  • D) It dissipates heat generated at the cathode
Answer: B) It focuses the electron beam onto a small area of the anode
Q13. The quality (penetrating power) of an X-ray beam is primarily determined by:
  • A) Tube current (mA)
  • B) Exposure time (s)
  • C) Tube voltage (kVp)
  • D) Focal spot size
Answer: C) Tube voltage (kVp)
Q14. The intensity of the primary X-ray beam is primarily controlled by:
  • A) kVp
  • B) mAs (milliampere-seconds)
  • C) Filtration
  • D) Source-to-image distance
Answer: B) mAs (milliampere-seconds)
Q15. In a rotating anode tube, the anode is typically made of:
  • A) Pure tungsten
  • B) Tungsten–rhenium alloy on a molybdenum/graphite substrate
  • C) Copper with tungsten coating
  • D) Tantalum with gold coating
Answer: B) Tungsten–rhenium alloy on a molybdenum/graphite substrate Rhenium improves thermal properties; molybdenum/graphite substrate reduces mass.
Q16. The primary purpose of the tube housing is to:
  • A) Maintain vacuum within the tube
  • B) Provide radiation protection and mechanical support
  • C) Focus the electron beam
  • D) Control the kVp applied
Answer: B) Provide radiation protection and mechanical support The housing also contains oil for cooling and provides leakage radiation shielding.
Q17. Grid-controlled X-ray tubes are primarily used in:
  • A) Mammography
  • B) Pulsed fluoroscopy and serial angiography
  • C) Conventional chest radiography
  • D) Dental radiography
Answer: B) Pulsed fluoroscopy and serial angiography
Q18. The primary method of heat dissipation from the anode to the tube housing is:
  • A) Conduction through the anode stem
  • B) Convection via oil circulation
  • C) Radiation (infrared) across the vacuum
  • D) Conduction through the glass envelope
Answer: C) Radiation (infrared) across the vacuum In a vacuum, heat cannot be transferred by conduction or convection — only radiation.
Q19. As anode angle decreases, which of the following occurs?
  • A) Effective focal spot increases, field coverage increases
  • B) Effective focal spot decreases, field coverage decreases
  • C) Effective focal spot decreases, field coverage increases
  • D) No change in effective focal spot
Answer: B) Effective focal spot decreases, field coverage decreases
Q20. The characteristic X-ray spectrum of tungsten shows peaks corresponding to:
  • A) K-alpha and K-beta transitions
  • B) L-shell and M-shell transitions only
  • C) Bremsstrahlung spectrum without discrete peaks
  • D) Only M-shell transitions
Answer: A) K-alpha and K-beta transitions Characteristic X-rays from tungsten occur when electrons fill vacancies in inner shells.

MODULE II: X-Ray Generator Circuits and Circuit Types

Q21. In a half-wave rectified circuit, the X-ray tube conducts during:
  • A) Both positive and negative half-cycles
  • B) Only the positive half-cycle
  • C) Only the negative half-cycle
  • D) A portion of both half-cycles
Answer: B) Only the positive half-cycle
Q22. A three-phase, six-pulse generator produces a ripple factor of approximately:
  • A) 100%
  • B) 13%
  • C) 3–4%
  • D) <1%
Answer: B) 13% Six-pulse: ~13% ripple; 12-pulse: ~3–4% ripple; constant potential: ~0%.
Q23. The auto-transformer in an X-ray circuit is used to:
  • A) Step up voltage to kilovolt levels
  • B) Provide variable low-voltage taps for kVp selection
  • C) Rectify the alternating current
  • D) Stabilize the filament current
Answer: B) Provide variable low-voltage taps for kVp selection
Q24. Space charge compensation in X-ray generators is achieved by:
  • A) Increasing the kVp at high mA settings
  • B) Increasing the filament voltage/current to maintain mA as kVp increases
  • C) Using a capacitor to filter the HT supply
  • D) Reducing the anode rotation speed
Answer: B) Increasing the filament voltage/current to maintain mA as kVp increases As kVp rises, space charge disperses, reducing mA — compensation raises filament current.
Q25. In a high-frequency (medium-frequency) generator, the mains supply is first:
  • A) Stepped up then rectified
  • B) Rectified, then inverted to high-frequency AC, then stepped up and rectified again
  • C) Stepped down then inverted
  • D) Directly applied to the X-ray tube
Answer: B) Rectified, then inverted to high-frequency AC, then stepped up and rectified again
Q26. The main advantage of a high-frequency generator over a three-phase generator is:
  • A) Lower output voltage
  • B) Smaller size, lower ripple, and more accurate kVp control
  • C) Higher ripple factor for better image contrast
  • D) Simpler circuit design
Answer: B) Smaller size, lower ripple, and more accurate kVp control
Q27. A solid-state (semiconductor) diode is preferred over a vacuum tube diode because:
  • A) It requires higher filament current
  • B) It is smaller, more reliable, and requires no heating
  • C) It produces higher voltage output
  • D) It operates only with AC
Answer: B) It is smaller, more reliable, and requires no heating
Q28. The purpose of the mains voltage compensator (MVC) is to:
  • A) Regulate the filament current
  • B) Correct for fluctuations in the incoming mains voltage to maintain constant kVp
  • C) Control the exposure time
  • D) Stabilize the rectifier output
Answer: B) Correct for fluctuations in the incoming mains voltage to maintain constant kVp
Q29. Automatic Exposure Control (AEC) terminates the exposure when:
  • A) A preset kVp is reached
  • B) A preset quantity of radiation (charge) has reached the detector
  • C) The filament reaches a set temperature
  • D) The anode reaches its maximum heat capacity
Answer: B) A preset quantity of radiation (charge) has reached the detector
Q30. In a three-phase 12-pulse circuit, the number of rectifier diodes required is:
  • A) 4
  • B) 6
  • C) 12
  • D) 24
Answer: C) 12 A 12-pulse circuit uses two sets of 6-pulse bridges = 12 diodes.
Q31. The kVp compensator in an X-ray circuit corrects for:
  • A) Variation in mAs
  • B) Voltage drop across the circuit elements during exposure
  • C) Frequency variations only
  • D) Heat buildup in the transformer
Answer: B) Voltage drop across the circuit elements during exposure
Q32. In a falling-load generator:
  • A) mA decreases and kVp increases as exposure proceeds
  • B) mA starts at maximum and decreases to maintain constant HU per unit time
  • C) kVp falls while mA remains constant
  • D) Both mA and kVp fall together
Answer: B) mA starts at maximum and decreases to maintain constant HU per unit time
Q33. The purpose of a relay in an X-ray circuit for overload protection is to:
  • A) Increase the current when demand is high
  • B) Automatically disconnect the circuit when preset limits are exceeded
  • C) Stabilize the filament voltage
  • D) Reduce electromagnetic interference
Answer: B) Automatically disconnect the circuit when preset limits are exceeded
Q34. The contactor (exposure switch) in a high-voltage circuit must be rated to handle:
  • A) Mains voltage only (220/110 V)
  • B) High voltage (up to 150 kVp) and high current simultaneously
  • C) Only low-frequency signals
  • D) Signal-level voltages for timing circuits
Answer: B) High voltage (up to 150 kVp) and high current simultaneously
Q35. Single-phase full-wave rectification produces a ripple of:
  • A) 0%
  • B) 13%
  • C) 100%
  • D) 50% (half-cycles missing)
Answer: C) 100% Full-wave single-phase still has voltage dropping to zero between each half-cycle = 100% ripple.
Q36. A capacitor discharge (CD) generator stores energy in a capacitor bank and:
  • A) Produces constant kVp throughout the exposure
  • B) Shows falling kVp as the capacitor discharges through the X-ray tube
  • C) Requires three-phase mains power
  • D) Is used only for high-power angiography
Answer: B) Shows falling kVp as the capacitor discharges through the X-ray tube
Q37. The high-tension selector switch allows the operator to select:
  • A) mAs values
  • B) The focus (focal spot) size and associated kVp range
  • C) The grid ratio
  • D) The exposure timer type
Answer: B) The focus (focal spot) size and associated kVp range
Q38. In a self-rectified X-ray circuit, the X-ray tube itself acts as a rectifier because:
  • A) The anode emits electrons during reverse voltage
  • B) The cathode emits electrons only when heated, preventing reverse current flow
  • C) The glass envelope blocks reverse current
  • D) The oil surrounding the tube acts as a dielectric rectifier
Answer: B) The cathode emits electrons only when heated, preventing reverse current flow
Q39. Which timer type is most accurate for very short exposure times (<10 ms)?
  • A) Clockwork timer
  • B) Synchronous motor timer
  • C) Electronic timer
  • D) Photometric timer
Answer: C) Electronic timer
Q40. The primary circuit of an X-ray generator operates at:
  • A) Kilovolt levels (40–150 kV)
  • B) Mains voltage levels (110–440 V)
  • C) Millivolt levels
  • D) DC only
Answer: B) Mains voltage levels (110–440 V)

MODULE III: Control of Scattered Radiation

Q41. The grid ratio is defined as:
  • A) The ratio of grid height to interspace width (h/D)
  • B) The ratio of lead strip width to interspace width
  • C) The number of grid lines per centimetre
  • D) The ratio of transmitted primary to transmitted scattered radiation
Answer: A) The ratio of grid height to interspace width (h/D)
Q42. The Bucky factor (grid factor) represents:
  • A) The ratio of primary to scatter transmission
  • B) The increase in exposure required when using a grid compared to no grid
  • C) The number of grid lines per mm
  • D) The ratio of the grid ratio to the scatter fraction
Answer: B) The increase in exposure required when using a grid compared to no grid
Q43. Grid cut-off occurs when:
  • A) The X-ray beam is perfectly aligned with grid lines
  • B) The X-ray beam strikes the lead strips at an angle, absorbing primary radiation
  • C) Scattered radiation exceeds primary radiation
  • D) The grid moves too slowly during exposure
Answer: B) The X-ray beam strikes the lead strips at an angle, absorbing primary radiation
Q44. A focused grid differs from a parallel grid in that:
  • A) It has curved lead strips that converge at the focal distance
  • B) It contains more lead strips per centimetre
  • C) It is used only in stationary positions
  • D) It has a higher grid ratio
Answer: A) It has curved lead strips that converge at the focal distance
Q45. The selectivity of a grid is defined as:
  • A) The ratio of transmitted primary radiation to transmitted scattered radiation
  • B) The ratio of grid frequency to grid ratio
  • C) The Bucky factor minus 1
  • D) The ratio of lead content to total grid area
Answer: A) The ratio of transmitted primary radiation to transmitted scattered radiation
Q46. A crossed grid (cross-hatch grid) consists of:
  • A) Two superimposed focused grids with lines at right angles
  • B) A single grid with alternating lead and aluminium strips
  • C) A grid used exclusively with crossed X-ray beams
  • D) A grid with diagonal lead strips
Answer: A) Two superimposed focused grids with lines at right angles
Q47. In oscillatory (reciprocating) grid movement, the grid moves:
  • A) In one direction only during the exposure
  • B) Back and forth continuously during the exposure to blur grid lines
  • C) In a circular pattern
  • D) Only before the exposure begins
Answer: B) Back and forth continuously during the exposure to blur grid lines
Q48. The Potter-Bucky diaphragm moves the grid:
  • A) Before the exposure to pre-position it
  • B) During the exposure to blur grid lines from the image
  • C) After the exposure to reset it
  • D) Synchronously with the anode rotation
Answer: B) During the exposure to blur grid lines from the image
Q49. Added filtration in an X-ray beam is typically made of:
  • A) Lead
  • B) Aluminium (Al) for general radiology; copper for high-kV techniques
  • C) Steel
  • D) Glass
Answer: B) Aluminium (Al) for general radiology; copper for high-kV techniques
Q50. Inherent filtration includes:
  • A) Added aluminium filters placed at the tube port
  • B) The glass/beryllium window of the tube, oil, and tube port cover
  • C) The collimator mirror and light source
  • D) The patient's skin and soft tissue
Answer: B) The glass/beryllium window of the tube, oil, and tube port cover
Q51. The half-value layer (HVL) is used to measure:
  • A) The intensity of the X-ray beam
  • B) The quality (energy) of the X-ray beam
  • C) The focal spot size
  • D) The grid selectivity
Answer: B) The quality (energy) of the X-ray beam
Q52. A light beam diaphragm (light beam collimator) uses a mirror angled at 45° to:
  • A) Filter out low-energy X-rays
  • B) Project a light field coincident with the X-ray field for positioning
  • C) Reflect scattered radiation away from the film
  • D) Measure the SID (source-to-image distance)
Answer: B) Project a light field coincident with the X-ray field for positioning
Q53. Which grid frequency (lines/cm) is considered high-frequency, reducing grid lines from appearing on the image?
  • A) 8–12 lines/cm
  • B) 20–40 lines/cm
  • C) 60–80 lines/cm
  • D) >100 lines/cm
Answer: C) 60–80 lines/cm
Q54. Grided cassettes (grided Bucky cassettes) are used primarily in:
  • A) Fixed Bucky units
  • B) Mobile/portable radiography where a stationary grid is acceptable
  • C) Fluoroscopy
  • D) CT scanning
Answer: B) Mobile/portable radiography where a stationary grid is acceptable
Q55. The primary purpose of using a cone or cylinder collimator is to:
  • A) Increase scattered radiation
  • B) Restrict the X-ray beam to the anatomical area of interest, reducing patient dose and scatter
  • C) Increase the anode angle
  • D) Improve heat dissipation
Answer: B) Restrict the X-ray beam to the anatomical area of interest, reducing patient dose and scatter
Q56. In a focused grid, the convergence point (focal point) is located at the:
  • A) Center of the grid
  • B) Specified focal distance (focus-grid distance)
  • C) Surface of the image receptor
  • D) Midplane of the patient
Answer: B) Specified focal distance (focus-grid distance)
Q57. Lateral grid decentering (off-center error) results in:
  • A) Uniform reduction in density across the entire image
  • B) Absorption of primary radiation increasing toward one side of the image (unilateral grid cut-off)
  • C) Increased scatter reaching the detector
  • D) No visible effect on the image
Answer: B) Absorption of primary radiation increasing toward one side of the image (unilateral grid cut-off)
Q58. A single-stroke grid movement means:
  • A) The grid completes one full back-and-forth cycle during exposure
  • B) The grid moves in one direction only during the entire exposure
  • C) The grid oscillates at high frequency
  • D) The grid is stationary
Answer: B) The grid moves in one direction only during the entire exposure
Q59. Heavy metal filters (e.g., copper, tin) are used in conjunction with aluminium because:
  • A) They reduce low-energy scattered radiation more effectively than Al alone
  • B) Al absorbs the characteristic X-rays emitted by heavy metals
  • C) They increase beam intensity
  • D) Both A and B
Answer: D) Both A and B Heavy metals filter mid-energy photons; the trailing Al absorbs the heavy metal's own characteristic radiation (K-edge effect).
Q60. The main disadvantage of a high grid ratio is:
  • A) Poor scatter cleanup
  • B) Increased patient radiation dose and strict centering requirements
  • C) Reduced image sharpness
  • D) Increased grid frequency artifacts
Answer: B) Increased patient radiation dose and strict centering requirements

MODULE IV: Meters and Exposure Timers

Q61. In a moving coil galvanometer, the torque that deflects the pointer is produced by:
  • A) A permanent magnet acting on a current-carrying coil
  • B) An electromagnet acting on a permanent magnet pointer
  • C) An AC-induced current in the coil
  • D) A bimetallic strip sensitive to temperature
Answer: A) A permanent magnet acting on a current-carrying coil
Q62. To convert a galvanometer into a voltmeter, you connect:
  • A) A low-resistance shunt in parallel
  • B) A high-resistance multiplier in series
  • C) A capacitor in parallel
  • D) A transformer in series
Answer: B) A high-resistance multiplier in series
Q63. To convert a galvanometer into an ammeter, you connect:
  • A) A high-resistance multiplier in series
  • B) A low-resistance shunt in parallel
  • C) A capacitor in series
  • D) An inductor in parallel
Answer: B) A low-resistance shunt in parallel
Q64. A pre-reading kV meter measures kVp:
  • A) During the actual exposure
  • B) Before the exposure, under no-load conditions, to predict the actual kVp
  • C) After the exposure, using a dosimeter
  • D) Only in digital generators
Answer: B) Before the exposure, under no-load conditions, to predict the actual kVp
Q65. The main advantage of a digital panel meter over an analogue meter in X-ray equipment is:
  • A) It uses a moving coil and is more rugged
  • B) Higher accuracy, no parallax error, and easier to interface with microprocessors
  • C) It can measure only AC quantities
  • D) It is less susceptible to electromagnetic interference
Answer: B) Higher accuracy, no parallax error, and easier to interface with microprocessors
Q66. A synchronous motor timer is driven by:
  • A) A spring-wound mechanism
  • B) The mains supply frequency, providing accurate timing based on cycle counting
  • C) A DC motor with a tachometer
  • D) A quartz crystal oscillator
Answer: B) The mains supply frequency, providing accurate timing based on cycle counting
Q67. The minimum exposure time achievable with a clockwork (mechanical) timer is approximately:
  • A) 0.001 s (1 ms)
  • B) 0.1 s (100 ms)
  • C) 0.01 s (10 ms)
  • D) 1.0 s
Answer: B) 0.1 s (100 ms) Clockwork timers are inaccurate below ~100 ms due to mechanical inertia.
Q68. A photometric timer (phototimer) uses which principle to terminate exposure?
  • A) Ion chamber collecting charge proportional to radiation received
  • B) A photomultiplier tube or photodiode detecting light from a fluorescent screen
  • C) A bimetallic strip responding to tube heat
  • D) A digital counter counting half-cycles of tube current
Answer: B) A photomultiplier tube or photodiode detecting light from a fluorescent screen
Q69. An ion chamber-based AEC (ionization chamber timer) terminates exposure when:
  • A) The chamber temperature reaches a set point
  • B) The integrated charge collected by the ion chamber reaches a preset value
  • C) The kVp across the chamber reaches threshold
  • D) The chamber capacitor is fully charged
Answer: B) The integrated charge collected by the ion chamber reaches a preset value
Q70. The integrated timer (mAs meter) in an X-ray unit measures:
  • A) Peak kilovoltage
  • B) The product of tube current and time (mAs) during the exposure
  • C) The heat units deposited in the anode
  • D) The total radiation dose to the patient
Answer: B) The product of tube current and time (mAs) during the exposure
Q71. In a moving coil instrument, the restoring torque is provided by:
  • A) The permanent magnet field
  • B) Control springs (hair springs) attached to the coil
  • C) Gravity acting on an off-center weight
  • D) An eddy current damping coil
Answer: B) Control springs (hair springs) attached to the coil
Q72. Eddy current damping in a galvanometer is achieved by:
  • A) Wrapping the coil with a resistive wire
  • B) Winding the coil on a light aluminium frame, which develops opposing currents in the field
  • C) Adding a dashpot filled with oil
  • D) Using a heavier pointer to slow oscillation
Answer: B) Winding the coil on a light aluminium frame, which develops opposing currents in the field
Q73. The kV meter used during a fluoroscopic procedure typically reads:
  • A) The peak instantaneous kVp
  • B) The average kV applied to the tube during continuous fluoroscopy
  • C) The stored energy in the HT transformer
  • D) The filament voltage
Answer: B) The average kV applied to the tube during continuous fluoroscopy
Q74. Which of the following timers is MOST suitable for very short exposures (1–2 ms) in digital subtraction angiography?
  • A) Clockwork timer
  • B) Synchronous motor timer
  • C) Electronic timer
  • D) Phototimer
Answer: C) Electronic timer
Q75. A milliammeter used to measure tube current in diagnostic X-ray is placed in:
  • A) The high-voltage secondary circuit
  • B) The centre tap of the high-voltage transformer secondary (earthed point) to allow low-voltage measurement
  • C) The primary circuit of the autotransformer
  • D) The filament circuit
Answer: B) The centre tap of the high-voltage transformer secondary (earthed point) to allow low-voltage measurement

MODULE V: Fluoroscopy, Care and Maintenance of X-Ray Equipment

Q76. Fluorescence differs from phosphorescence in that:
  • A) Fluorescence continues after the exciting radiation is removed; phosphorescence stops immediately
  • B) Fluorescence stops immediately when radiation ceases; phosphorescence continues (afterglow)
  • C) Fluorescence requires UV light; phosphorescence requires X-rays
  • D) Fluorescence is a thermal process; phosphorescence is photochemical
Answer: B) Fluorescence stops immediately when radiation ceases; phosphorescence continues (afterglow)
Q77. The material most commonly used in fluoroscopic intensifying screens (image intensifier input phosphor) is:
  • A) Zinc cadmium sulphide
  • B) Caesium iodide (CsI) — structured/columnar crystalline form
  • C) Barium platinocyanide
  • D) Calcium tungstate
Answer: B) Caesium iodide (CsI) — structured/columnar crystalline form CsI's needle-like crystal structure limits light spread, improving resolution.
Q78. Dark adaptation of the eyes before fluoroscopy (in conventional fluoroscopy) was required because:
  • A) The fluoroscopic image was produced by very low light levels requiring rod cell sensitivity
  • B) The room lights could damage the image intensifier
  • C) The X-ray beam was visible to dark-adapted eyes
  • D) High ambient light caused screen burn
Answer: A) The fluoroscopic image was produced by very low light levels requiring rod cell sensitivity
Q79. The tilting fluoroscopic table (Bucky stand/tilting table) allows patient positioning from:
  • A) 0° to 45° only
  • B) 0° (horizontal) to 90° (vertical) and sometimes to Trendelenburg (head-down)
  • C) Only vertical (90°) to 45°
  • D) 0° to 180° (full inversion)
Answer: B) 0° (horizontal) to 90° (vertical) and sometimes to Trendelenburg (head-down)
Q80. In a modern image intensifier tube, the conversion gain refers to:
  • A) The ratio of output screen area to input screen area
  • B) The overall increase in image brightness achieved by the tube
  • C) The ratio of kVp output to kVp input
  • D) The ratio of electron gain to photon input
Answer: B) The overall increase in image brightness achieved by the tube Conversion gain = minification gain × flux gain.
Q81. When testing the performance of X-ray exposure timers, the most common test tool used is:
  • A) A dosimeter
  • B) A spinning top (for single-phase) or synchronous spinning top (for three-phase)
  • C) A kV meter
  • D) A focal spot test tool
Answer: B) A spinning top (for single-phase) or synchronous spinning top (for three-phase)
Q82. The focal spot size of an X-ray tube can be measured using:
  • A) A densitometer
  • B) A star test pattern or slit camera
  • C) A spinning top
  • D) An ion chamber
Answer: B) A star test pattern or slit camera
Q83. During routine quality assurance of the light beam diaphragm, acceptable congruence between the light field and X-ray field is:
  • A) Within 5% of the SID (source-to-image distance) at each edge
  • B) Within 2% of SID total (sum of misalignments)
  • C) Within 1 cm regardless of SID
  • D) Exact alignment with zero tolerance
Answer: B) Within 2% of SID total (sum of misalignments)
Q84. The mAs reproducibility test assesses:
  • A) Whether the same mAs setting produces the same radiation output consistently
  • B) The accuracy of the kVp meter
  • C) The alignment of the X-ray beam with the Bucky
  • D) The heat capacity of the anode
Answer: A) Whether the same mAs setting produces the same radiation output consistently
Q85. High-tension (HT) cables in X-ray equipment require special precautions because:
  • A) They carry low-frequency DC up to 150 kV
  • B) They can store residual high voltage charge even after the generator is switched off
  • C) They emit strong magnetic fields
  • D) They are brittle at room temperature
Answer: B) They can store residual high voltage charge even after the generator is switched off
Q86. The purpose of brakes and locks on an X-ray tube stand is to:
  • A) Allow rapid repositioning of the tube
  • B) Secure the tube in position during exposure and prevent accidental movement
  • C) Reduce vibration from the rotating anode
  • D) Electrically ground the tube housing
Answer: B) Secure the tube in position during exposure and prevent accidental movement
Q87. Functional testing of the X-ray machine should include verification of:
  • A) kVp accuracy, mAs linearity, timer accuracy, and radiation output reproducibility
  • B) Only the kVp meter calibration
  • C) The colour of the collimator light
  • D) The brand of the image receptor used
Answer: A) kVp accuracy, mAs linearity, timer accuracy, and radiation output reproducibility
Q88. Afterglow (phosphorescence) in a fluoroscopic screen is undesirable because:
  • A) It increases patient dose
  • B) It causes image lag, superimposing a previous image on the current one
  • C) It reduces the brightness of the fluorescent image
  • D) It increases the grid ratio
Answer: B) It causes image lag, superimposing a previous image on the current one
Q89. The maximum permissible leakage radiation from an X-ray tube housing (at 1 metre) is:
  • A) 10 mR/hr
  • B) 100 mR/hr (1 mGy/hr)
  • C) 1 R/hr
  • D) 10 R/hr
Answer: B) 100 mR/hr (1 mGy/hr) International standard: leakage ≤ 1 mGy/hr at 1 m under worst-case operating conditions.
Q90. When measuring available kVp, the test is performed to ensure that:
  • A) The kVp displayed on the control panel matches the actual kVp at the tube
  • B) The mAs is accurately timed
  • C) The focal spot is within specification
  • D) The grid lines are not visible on the image
Answer: A) The kVp displayed on the control panel matches the actual kVp at the tube

MIXED / INTEGRATION QUESTIONS (Hard Level)

Q91. A radiographer notices a pattern of increased optical density on the cathode side and decreased density on the anode side of a chest radiograph. The MOST likely cause is:
  • A) Grid cut-off from lateral decentering
  • B) The heel effect — the cathode side always has higher intensity
  • C) Scattered radiation buildup
  • D) Off-focus radiation artifact
Answer: B) The heel effect — the cathode side always has higher intensity
Q92. For a three-phase 12-pulse generator, the HU formula multiplier compared to single-phase is:
  • A) 1.0
  • B) 1.35
  • C) 1.41
  • D) 2.0
Answer: C) 1.41 12-pulse multiplier = 1.41 (compared to 1.35 for 6-pulse).
Q93. If the anode of an X-ray tube is bombarded with 100 kV electrons at 500 mA, the total power input is:
  • A) 5 kW
  • B) 50 kW
  • C) 500 kW
  • D) 5000 W
Answer: B) 50 kW Power = kV × mA = 100 × 500 = 50,000 W = 50 kW.
Q94. A focused grid designed for a 100 cm focal distance is used at 150 cm SID. The result is:
  • A) No visible effect on the image
  • B) Peripheral grid cut-off — decreased density at both edges of the image
  • C) Central grid cut-off — decreased density in the middle of the image
  • D) Increased scatter on both sides
Answer: B) Peripheral grid cut-off — decreased density at both edges of the image When SID > focal grid distance, lead strips are angled away from the beam at the periphery.
Q95. The effective focal spot size is SMALLEST when the anode angle is:
  • A) 45°
  • B) 30°
  • C) 17°
  • D) 7°
Answer: D) 7° Effective focal spot = actual focal spot × sin(anode angle) — smaller angle gives smaller effective spot.
Q96. In a high-frequency generator operating at 25 kHz compared to 50 Hz mains:
  • A) The transformer requires a 500× larger core
  • B) The transformer core can be 500× smaller (transformer size ∝ 1/frequency)
  • C) The output ripple increases proportionally
  • D) The rectifier circuit is simpler
Answer: B) The transformer core can be 500× smaller (transformer size ∝ 1/frequency)
Q97. A spinning top test on a single-phase full-wave rectified unit set to 0.1 s should show:
  • A) 6 dots
  • B) 12 dots (at 60 Hz supply) or 10 dots (at 50 Hz supply)
  • C) 24 dots
  • D) A continuous arc
Answer: B) 12 dots (at 60 Hz supply) or 10 dots (at 50 Hz supply) Full-wave rectification = 2 pulses per cycle. At 50 Hz: 100 pulses/s × 0.1 s = 10 dots.
Q98. The space charge compensation circuit is MOST critical at:
  • A) Low kVp and high mA settings
  • B) High kVp settings where filament emission would naturally increase excessively
  • C) Any kVp with low mA
  • D) During the warm-up of the X-ray tube
Answer: B) High kVp settings where filament emission would naturally increase excessively At high kVp, space charge disperses → more electrons flow → compensation reduces filament current to prevent mA overshoot.
Q99. Which of the following changes would BOTH reduce patient dose AND reduce scatter reaching the image receptor?
  • A) Increasing kVp and decreasing mAs, with a grid
  • B) Increasing field size and removing the grid
  • C) Collimating the beam to the area of interest and using a grid
  • D) Increasing mAs and using a faster screen
Answer: C) Collimating the beam to the area of interest and using a grid
Q100. In an image intensifier, vignetting refers to:
  • A) Geometric distortion at the periphery of the image
  • B) Reduction in brightness at the edges of the image due to the electrostatic lens design
  • C) Temporal lag caused by phosphorescent afterglow
  • D) Increased noise at low dose rates
Answer: B) Reduction in brightness at the edges of the image due to the electrostatic lens design

Summary by Module

ModuleQuestionsFocus Areas
I — X-Ray Tube & X-Ray ProductionQ1–Q20Anode materials, line focus principle, heel effect, rotating anode, heat units, efficiency
II — Generator CircuitsQ21–Q40Rectification types, ripple factors, HF generators, AEC, timers, relays
III — Scattered Radiation ControlQ41–Q60Grid ratio, Bucky factor, cut-off errors, filtration, collimation
IV — Meters & TimersQ61–Q75Galvanometer, ammeter/voltmeter conversion, timer types, mAs meter
V — Fluoroscopy & MaintenanceQ76–Q90Fluorescence vs phosphorescence, QA tests, HT cable safety, focal spot measurement
Integration (Hard)Q91–Q100Multi-concept clinical problem solving
Good luck on your exam tomorrow! Focus especially on:
  • Heel effect direction (cathode = higher intensity)
  • Grid cut-off types (lateral, focal distance, angular)
  • Ripple percentages (single-phase 100%, 6-pulse 13%, 12-pulse ~3–4%)
  • HU multipliers (1× for 1-phase, 1.35× for 6-pulse, 1.41× for 12-pulse)
  • Heat dissipation in vacuum = radiation only (no conduction/convection)
  • AEC termination = preset charge collected, not kVp or time
This is a shared conversation. Sign in to Orris to start your own chat.