Q.1 What is the primary physical phenomenon that produces X‑rays in an X‑ray tube?
Bremsstrahlung radiation
Fluorescence emission
Cherenkov radiation
Compton scattering
Explanation - When high‑energy electrons are decelerated upon hitting the anode, they emit bremsstrahlung X‑rays, which form the continuous spectrum.
Correct answer is: Bremsstrahlung radiation
Q.2 Which material is most commonly used as the target (anode) in a diagnostic X‑ray tube?
Copper
Tungsten
Aluminium
Lead
Explanation - Tungsten has a high atomic number and a high melting point, making it ideal for efficient X‑ray production and heat resistance.
Correct answer is: Tungsten
Q.3 The term “kVp” in X‑ray imaging stands for:
Kilovolt peak
Kilo‑volume per minute
Kinetic voltage potential
Kilo‑valve power
Explanation - kVp is the peak voltage applied across the X‑ray tube and determines the maximum photon energy and penetrating ability of the beam.
Correct answer is: Kilovolt peak
Q.4 Increasing the kVp of an X‑ray beam will generally:
Increase image contrast
Decrease patient dose
Increase photon energy and penetration
Reduce the field of view
Explanation - Higher kVp produces higher‑energy photons, which can penetrate thicker tissues more effectively, but may reduce contrast.
Correct answer is: Increase photon energy and penetration
Q.5 What is the purpose of an X‑ray collimator?
To increase tube current
To limit the size and shape of the X‑ray beam
To cool the anode
To convert X‑rays to visible light
Explanation - Collimators shape the beam, reducing patient dose and scatter, and defining the area of interest.
Correct answer is: To limit the size and shape of the X‑ray beam
Q.6 Which interaction is most responsible for image contrast in soft tissue X‑ray imaging?
Compton scattering
Photoelectric absorption
Pair production
Rayleigh scattering
Explanation - Photoelectric absorption varies with atomic number and photon energy, providing contrast between different soft tissues.
Correct answer is: Photoelectric absorption
Q.7 The half‑value layer (HVL) of an X‑ray beam is a measure of:
Beam intensity at the detector
The thickness of material that reduces beam intensity by 50%
The focal spot size of the tube
The exposure time needed for a diagnostic image
Explanation - HVL quantifies beam quality; a larger HVL indicates higher beam energy (more penetrating).
Correct answer is: The thickness of material that reduces beam intensity by 50%
Q.8 Which detector technology is most commonly used in modern digital radiography (DR)?
Photographic film
Photostimulable phosphor plates
Flat‑panel amorphous silicon (a‑Si) detectors
Charge‑coupled devices (CCD)
Explanation - a‑Si flat‑panel detectors directly convert X‑rays to electrical signals, providing fast readout and high image quality.
Correct answer is: Flat‑panel amorphous silicon (a‑Si) detectors
Q.9 In computed tomography (CT), the term “slice thickness” refers to:
The physical thickness of the detector array
The width of the X‑ray beam
The reconstructed image thickness along the patient’s axis
The distance between the X‑ray source and detector
Explanation - Slice thickness determines the volume represented by each image and affects spatial resolution and noise.
Correct answer is: The reconstructed image thickness along the patient’s axis
Q.10 Which contrast agent is most frequently used for enhancing vascular structures in X‑ray angiography?
Gadolinium‑based agents
Iodine‑containing compounds
Barium sulfate suspension
Technetium‑99m
Explanation - Iodine has a high atomic number, providing strong X‑ray attenuation and highlighting blood vessels during angiography.
Correct answer is: Iodine‑containing compounds
Q.11 The primary advantage of using a high‑frequency X‑ray generator over a low‑frequency generator is:
Higher tube voltage
Lower patient dose for the same image quality
Larger focal spot size
Longer exposure times
Explanation - High‑frequency generators produce X‑rays more efficiently, reducing heat and allowing lower mA for the same output, which reduces patient dose.
Correct answer is: Lower patient dose for the same image quality
Q.12 Which of the following best describes the term “quantum mottle” in digital X‑ray images?
Noise caused by patient motion
Variations due to low photon statistics
Artifacts from detector dead pixels
Blur caused by focal spot size
Explanation - Quantum mottle arises when insufficient X‑ray photons reach the detector, leading to grainy appearance.
Correct answer is: Variations due to low photon statistics
Q.13 In mammography, why is a lower kVp (around 25‑30 kVp) typically used compared to general radiography?
To increase patient comfort
To enhance contrast between adipose and glandular tissue
To reduce the size of the focal spot
To decrease exposure time
Explanation - Lower kVp increases photoelectric effect differences between soft tissues, improving contrast for detecting microcalcifications.
Correct answer is: To enhance contrast between adipose and glandular tissue
Q.14 Which physical law explains why higher‑Z materials attenuate X‑rays more effectively?
Ohm’s law
Beer‑Lambert law
Fick’s law
Planck’s law
Explanation - The Beer‑Lambert law describes exponential attenuation, where attenuation coefficient increases with atomic number.
Correct answer is: Beer‑Lambert law
Q.15 What is the main purpose of a “grid” in conventional radiography?
To increase the X‑ray beam intensity
To absorb scattered radiation before it reaches the detector
To focus the X‑ray beam
To cool the X‑ray tube
Explanation - Grids consist of alternating strips of lead and radiolucent material that preferentially absorb scattered photons, improving image contrast.
Correct answer is: To absorb scattered radiation before it reaches the detector
Q.16 Which of the following best defines “spatial resolution” in an X‑ray image?
Ability to distinguish small differences in X‑ray intensity
Ability to differentiate two closely spaced structures
Amount of radiation dose delivered
Speed of image acquisition
Explanation - Spatial resolution refers to the smallest object size that can be distinguished, often expressed in line pairs per millimeter (lp/mm).
Correct answer is: Ability to differentiate two closely spaced structures
Q.17 The term “radiographic density” refers to:
The amount of radiation absorbed by the patient
The optical density of the image on film or detector
The thickness of the X‑ray beam
The voltage applied to the X‑ray tube
Explanation - Radiographic density measures the darkness (or pixel value) of the image, reflecting the amount of radiation that reached the detector.
Correct answer is: The optical density of the image on film or detector
Q.18 In a fluoroscopy system, the image intensifier primarily serves to:
Generate X‑rays
Convert X‑rays to visible light and amplify the image
Store the image for later retrieval
Reduce patient dose by filtering the beam
Explanation - The intensifier converts X‑rays to light, then to electrons, and finally back to a brighter light image displayed on a monitor.
Correct answer is: Convert X‑rays to visible light and amplify the image
Q.19 Which of the following statements about “dual‑energy X‑ray imaging” is true?
It uses two different exposure times to improve motion blur.
It acquires images at two distinct kVp settings to differentiate materials.
It requires two X‑ray tubes placed at orthogonal angles.
It eliminates the need for a detector.
Explanation - Dual‑energy imaging exploits differences in attenuation at low and high energies to separate bone from soft tissue or detect contrast agents.
Correct answer is: It acquires images at two distinct kVp settings to differentiate materials.
Q.20 What is the principal health risk associated with repeated exposure to ionizing radiation from X‑rays?
Thermal burns
Radiation‑induced cancer
Magnetic field interference
Acoustic trauma
Explanation - Ionizing radiation can cause DNA damage leading to an increased lifetime risk of malignancy.
Correct answer is: Radiation‑induced cancer
Q.21 In digital X‑ray systems, the term “dynamic range” describes:
The range of X‑ray energies that can be produced
The ratio between the largest and smallest detectable signal levels
The physical size of the detector
The time interval over which an image can be acquired
Explanation - Dynamic range indicates the detector’s ability to capture both very low and very high exposures without saturation or loss of detail.
Correct answer is: The ratio between the largest and smallest detectable signal levels
Q.22 Which of the following is a common artifact in chest radiographs caused by patient movement?
Ring artifact
Motion blur
Beam hardening
Edge enhancement
Explanation - Patient motion during exposure leads to smearing of anatomical structures, reducing image sharpness.
Correct answer is: Motion blur
Q.23 The term “effective dose” in radiology is used to:
Measure the energy of X‑ray photons
Quantify the biological risk considering tissue sensitivities
Determine the exposure time needed for an image
Calculate the size of the X‑ray beam
Explanation - Effective dose (measured in sieverts) incorporates the type of radiation and the radiosensitivity of different tissues.
Correct answer is: Quantify the biological risk considering tissue sensitivities
Q.24 What is the main function of a “lead apron” in radiographic procedures?
To focus the X‑ray beam
To protect the patient’s eyes from radiation
To shield parts of the body from unnecessary radiation exposure
To improve image contrast
Explanation - Lead aprons attenuate X‑ray photons, reducing dose to protected body regions such as the abdomen and reproductive organs.
Correct answer is: To shield parts of the body from unnecessary radiation exposure
Q.25 Which imaging modality uses a rotating X‑ray source and detector to acquire multiple projections for 3‑D reconstruction?
Mammography
Fluoroscopy
Computed Tomography (CT)
Digital Subtraction Angiography
Explanation - CT acquires many angular views as the X‑ray tube and detectors rotate around the patient, enabling cross‑sectional imaging.
Correct answer is: Computed Tomography (CT)
Q.26 In X‑ray spectroscopy, the K‑edge of an element corresponds to:
The energy at which K‑shell electrons are ionized
The maximum energy of the X‑ray beam
The point where Compton scattering dominates
The energy required for pair production
Explanation - The K‑edge is the abrupt increase in attenuation when photon energy exceeds the binding energy of K‑shell electrons.
Correct answer is: The energy at which K‑shell electrons are ionized
Q.27 Which of the following statements about “scatter radiation” is correct?
It improves image contrast
It is primarily caused by the photoelectric effect
It originates from interactions of primary photons with matter
It can be ignored in high‑kVp imaging
Explanation - Scatter arises from Compton and Rayleigh interactions, degrading image contrast and increasing patient dose.
Correct answer is: It originates from interactions of primary photons with matter
Q.28 A typical focal spot size for a general‑purpose radiography X‑ray tube is:
0.1 mm
0.5 mm
1.0 mm
5.0 mm
Explanation - A focal spot of about 0.5 mm balances sharpness (spatial resolution) and heat handling for most diagnostic exams.
Correct answer is: 0.5 mm
Q.29 What is the primary reason for using “filtration” (e.g., aluminium filter) in an X‑ray beam?
To increase the tube voltage
To remove low‑energy photons that would increase patient dose without improving image quality
To focus the beam
To cool the X‑ray tube
Explanation - Filtration hardens the beam, reducing skin dose and improving beam quality.
Correct answer is: To remove low‑energy photons that would increase patient dose without improving image quality
Q.30 In digital radiography, “bit depth” of the detector influences:
The size of the detector
The number of grayscale levels that can be displayed
The exposure time
The tube current
Explanation - Higher bit depth (e.g., 14‑bit) provides more grayscale levels, improving subtle contrast detection.
Correct answer is: The number of grayscale levels that can be displayed
Q.31 Which of the following is a common clinical use of portable X‑ray units?
Screening for lung cancer in asymptomatic patients
Intra‑operative imaging during orthopedic surgery
High‑resolution imaging of dental enamel
Brain functional imaging
Explanation - Portable units enable bedside or intra‑operative imaging, such as confirming fracture reduction.
Correct answer is: Intra‑operative imaging during orthopedic surgery
Q.32 The term “beam hardening” in CT imaging refers to:
Increase in beam intensity with depth
Reduction in beam energy due to preferential absorption of low‑energy photons
Focusing of the X‑ray beam
Cooling of the X‑ray tube
Explanation - Beam hardening leads to artifacts such as cupping and streaks because the spectrum becomes more penetrating as it passes through dense material.
Correct answer is: Reduction in beam energy due to preferential absorption of low‑energy photons
Q.33 In an X‑ray tube, the “cathode” is responsible for:
Emitting electrons via thermionic emission
Generating X‑rays directly
Collimating the X‑ray beam
Cooling the anode
Explanation - The heated cathode releases electrons that are accelerated toward the anode to produce X‑rays.
Correct answer is: Emitting electrons via thermionic emission
Q.34 Which parameter is most directly related to patient entrance skin dose (ESD) in a radiographic exam?
kVp
mA·s (mAs)
Focal spot size
Image receptor size
Explanation - mAs determines the total number of X‑ray photons produced, directly influencing the dose delivered to the patient’s skin.
Correct answer is: mA·s (mAs)
Q.35 A “Bucky” grid is used in radiography to:
Focus the X‑ray beam
Move the grid during exposure to reduce grid lines in the image
Increase the kVp automatically
Provide patient positioning cues
Explanation - The Bucky system oscillates the grid, blurring the grid lines and improving image uniformity.
Correct answer is: Move the grid during exposure to reduce grid lines in the image
Q.36 In digital subtraction angiography (DSA), the subtraction process is performed to:
Increase patient dose
Remove background bone and soft tissue, highlighting contrast‑filled vessels
Enhance motion artifacts
Reduce the need for contrast agents
Explanation - DSA subtracts a pre‑contrast mask image from the post‑contrast image, isolating the vascular structures.
Correct answer is: Remove background bone and soft tissue, highlighting contrast‑filled vessels
Q.37 Which of the following best describes the concept of “radiographic magnification”?
Increasing the kVp to enlarge the image
Placing the object farther from the detector and closer to the X‑ray source
Using a larger focal spot size
Increasing the exposure time
Explanation - Magnification occurs because of geometric projection; the farther the object from the detector, the larger its image.
Correct answer is: Placing the object farther from the detector and closer to the X‑ray source
Q.38 Which type of X‑ray detector is based on a phosphor screen that stores a latent image to be read later by a laser scanner?
Computed Radiography (CR)
Direct Digital Radiography (DR)
Film‑Based Radiography
Fluoroscopy
Explanation - CR plates capture X‑ray energy in a photostimulable phosphor; a laser reads the stored image to create a digital file.
Correct answer is: Computed Radiography (CR)
Q.39 The primary advantage of “cone‑beam CT (CBCT)” over conventional CT for dental imaging is:
Higher radiation dose
Faster acquisition of volumetric data with lower dose
Superior soft‑tissue contrast
Ability to image the entire body in one rotation
Explanation - CBCT uses a cone‑shaped beam and flat‑panel detector, providing high‑resolution 3‑D images of the maxillofacial region with lower dose than conventional CT.
Correct answer is: Faster acquisition of volumetric data with lower dose
Q.40 In radiology, the term “ALARA” stands for:
As Low As Reasonably Achievable
Always Light And Radiation Absorbed
Advanced Low‑dose Automated Radiography Apparatus
Amplitude Limitation of X‑ray Radiation
Explanation - ALARA is a guiding principle to minimize radiation exposure while obtaining sufficient diagnostic information.
Correct answer is: As Low As Reasonably Achievable
Q.41 Which physical interaction dominates X‑ray attenuation in bone at diagnostic energies (30‑150 keV)?
Compton scattering
Photoelectric absorption
Pair production
Rayleigh scattering
Explanation - Bone contains calcium (high Z), leading to strong photoelectric effect, which enhances contrast against soft tissue.
Correct answer is: Photoelectric absorption
Q.42 What is the purpose of a “beam stop” in X‑ray imaging systems?
To prevent the X‑ray tube from overheating
To block the central portion of the beam for calibration
To protect the detector from direct radiation during dark‑field calibration
To increase patient dose
Explanation - A beam stop shields the detector while acquiring a dark image used for noise correction.
Correct answer is: To protect the detector from direct radiation during dark‑field calibration
Q.43 In mammography, why are compression plates used during image acquisition?
To increase the patient’s comfort
To flatten the breast, reducing thickness and improving image quality
To increase the exposure time
To enhance scatter radiation
Explanation - Compression reduces tissue thickness, improves photon utilization, and decreases motion blur and scatter.
Correct answer is: To flatten the breast, reducing thickness and improving image quality
Q.44 Which of the following best describes “image lag” in flat‑panel detectors?
Delayed readout of the previous image causing ghosting
Increased patient dose due to longer exposure
Loss of spatial resolution due to large focal spot
Enhanced contrast in the image
Explanation - Image lag occurs when residual charge from a prior exposure remains, creating a faint replica of the previous image.
Correct answer is: Delayed readout of the previous image causing ghosting
Q.45 What is the most common cause of “ring artifacts” in CT images?
Patient motion
Miscalibrated detector elements
Improper collimation
High kVp settings
Explanation - Ring artifacts appear as concentric circles caused by defective or miscalibrated detector rows.
Correct answer is: Miscalibrated detector elements
Q.46 In X‑ray safety, the term “inverse square law” indicates that intensity varies with:
The square of the distance from the source
The inverse of the distance
The inverse square of the distance from the source
The cube of the distance
Explanation - Radiation intensity decreases proportionally to 1/(distance²), a key principle for shielding and positioning.
Correct answer is: The inverse square of the distance from the source
Q.47 Which of the following is a typical indication for a chest X‑ray?
Evaluation of suspected pneumonia
Assessment of dental caries
Screening for breast cancer
Diagnosis of osteoporosis
Explanation - Chest radiography is commonly used to detect lung infiltrates, effusions, and other thoracic pathology.
Correct answer is: Evaluation of suspected pneumonia
Q.48 The “air kerma” measurement in X‑ray dosimetry refers to:
The kinetic energy released per unit mass of air
The total dose absorbed by the patient
The number of X‑ray photons emitted per second
The voltage applied to the tube
Explanation - Air kerma (in gray) quantifies the energy transferred from photons to air, used as a standard dosimetric quantity.
Correct answer is: The kinetic energy released per unit mass of air
Q.49 Which imaging technique combines X‑ray acquisition with real‑time display, often used for guiding interventional procedures?
Computed Tomography (CT)
Digital Subtraction Angiography (DSA)
Fluoroscopy
Mammography
Explanation - Fluoroscopy provides continuous X‑ray images at video rates, enabling dynamic observation and guidance.
Correct answer is: Fluoroscopy
Q.50 In X‑ray imaging, the term “contrast resolution” refers to:
The ability to distinguish small objects
The ability to differentiate differences in X‑ray attenuation
The speed of image acquisition
The size of the detector
Explanation - Contrast resolution measures how well subtle variations in tissue density are visualized.
Correct answer is: The ability to differentiate differences in X‑ray attenuation
Q.51 Which of the following best explains why X‑ray tubes require cooling systems?
To maintain the cathode temperature
To prevent overheating of the anode caused by high heat load during X‑ray production
To increase the focal spot size
To reduce the kVp
Explanation - Conversion of kinetic energy to X‑rays is inefficient; most energy becomes heat, requiring active or passive cooling.
Correct answer is: To prevent overheating of the anode caused by high heat load during X‑ray production
Q.52 The “CT number” (Hounsfield Unit) of water is defined as:
-1000 HU
0 HU
+1000 HU
+500 HU
Explanation - Hounsfield Units are calibrated so that water has a value of 0 HU, air -1000 HU, and dense bone +1000 HU (approximately).
Correct answer is: 0 HU
Q.53 Which factor most significantly affects the “geometric unsharpness” of an X‑ray image?
Focal spot size
Tube voltage (kVp)
Patient age
Detector pixel size
Explanation - Larger focal spots increase penumbra, causing more geometric blur; minimizing focal spot size improves sharpness.
Correct answer is: Focal spot size
Q.54 In a digital X‑ray system, the “gain” setting primarily adjusts:
The X‑ray tube voltage
The amplification of the electrical signal from the detector
The size of the image receptor
The patient positioning
Explanation - Gain controls signal amplification to optimize image brightness without saturating the detector.
Correct answer is: The amplification of the electrical signal from the detector
Q.55 Which imaging modality utilizes a rotating anode and a fan‑shaped X‑ray beam?
Mammography
Conventional radiography
Computed Tomography (CT)
Fluoroscopy
Explanation - CT systems have rotating anodes and fan beams that sweep around the patient to collect data for reconstruction.
Correct answer is: Computed Tomography (CT)
Q.56 What is the main benefit of using a “low‑dose” protocol in pediatric X‑ray examinations?
Improved image sharpness
Reduced motion artifacts
Lower radiation exposure, minimizing long‑term risk
Shorter examination time
Explanation - Children are more radiosensitive; low‑dose protocols aim to keep dose as low as reasonably achievable while maintaining diagnostic quality.
Correct answer is: Lower radiation exposure, minimizing long‑term risk
Q.57 Which of the following is NOT a typical component of an X‑ray tube housing?
Glass envelope
High‑voltage transformer
Anode
Focal spot
Explanation - The transformer is external to the tube; the tube housing contains the glass envelope, anode, cathode, and focal spot.
Correct answer is: High‑voltage transformer
Q.58 In X‑ray imaging, “scatter correction” can be achieved by:
Increasing kVp
Using anti‑scatter grids
Increasing exposure time
Widening the focal spot
Explanation - Grids absorb scattered photons before they reach the detector, improving contrast.
Correct answer is: Using anti‑scatter grids
Q.59 What is the typical range of tube voltage (kVp) used for a standard chest X‑ray?
30‑40 kVp
60‑80 kVp
100‑120 kVp
150‑180 kVp
Explanation - Chest radiography generally uses 100‑120 kVp to provide sufficient penetration through the thorax.
Correct answer is: 100‑120 kVp
Q.60 Which of the following statements about “pair production” is true for diagnostic X‑ray energies?
It is the dominant interaction at 30‑150 keV
It occurs only above 1.022 MeV photon energy
It enhances image contrast in soft tissue
It is used to generate X‑rays in the tube
Explanation - Pair production requires photon energies >1.022 MeV, far above diagnostic ranges, thus it does not occur in conventional imaging.
Correct answer is: It occurs only above 1.022 MeV photon energy
Q.61 In digital radiography, the term “noise” most commonly refers to:
Random variations in pixel values caused by statistical fluctuations in photon detection
Deliberate image enhancement
The intentional addition of contrast agents
Motion blur
Explanation - Noise arises from quantum (photon) statistics and electronic readout variations, degrading image quality.
Correct answer is: Random variations in pixel values caused by statistical fluctuations in photon detection
Q.62 Which of the following best characterizes the purpose of a “contrast‑to‑noise ratio (CNR)” metric?
It measures patient dose
It quantifies the ability to differentiate an object from background noise
It indicates the speed of image acquisition
It describes the focal spot size
Explanation - Higher CNR means better detectability of low‑contrast structures amid noise.
Correct answer is: It quantifies the ability to differentiate an object from background noise
Q.63 The “automatic exposure control (AEC)” system in radiography primarily adjusts:
kVp
mA
Exposure time (seconds)
Focal spot size
Explanation - AEC terminates the exposure when a predetermined detector signal is reached, usually by varying exposure time.
Correct answer is: Exposure time (seconds)
Q.64 Which imaging modality uses a synchrotron source for high‑resolution X‑ray phase‑contrast imaging?
Standard radiography
Computed Tomography (CT)
Phase‑contrast X‑ray imaging
Digital Subtraction Angiography
Explanation - Synchrotrons provide highly coherent X‑rays suitable for phase‑contrast techniques that enhance soft‑tissue detail.
Correct answer is: Phase‑contrast X‑ray imaging
Q.65 In orthopedic imaging, a “stress fracture” is best detected using:
Standard X‑ray
Magnetic Resonance Imaging (MRI)
Bone scan (scintigraphy)
Ultrasound
Explanation - Bone scans are highly sensitive for early metabolic changes associated with stress fractures before radiographic changes appear.
Correct answer is: Bone scan (scintigraphy)
Q.66 The term “radiolucent” describes a material that:
Absorbs X‑rays strongly
Allows X‑rays to pass through with little attenuation
Emits X‑rays when stimulated
Reflects X‑rays
Explanation - Radiolucent materials appear dark on radiographs because they attenuate few X‑ray photons.
Correct answer is: Allows X‑rays to pass through with little attenuation
Q.67 Which of the following is a primary benefit of using a “flat‑panel detector” over an image intensifier in fluoroscopy?
Higher radiation dose
Larger physical size
Better image uniformity and reduced geometric distortion
Longer acquisition times
Explanation - Flat‑panel detectors provide consistent pixel geometry, eliminating the pincushion distortion seen with intensifiers.
Correct answer is: Better image uniformity and reduced geometric distortion
Q.68 In X‑ray imaging, the term “k‑edge filtration” is used to:
Increase the beam’s low‑energy component
Remove specific photon energies to enhance contrast for particular elements
Cool the X‑ray tube
Focus the beam
Explanation - K‑edge filters (e.g., gadolinium) absorb photons just above a material’s K‑edge, improving contrast for that material.
Correct answer is: Remove specific photon energies to enhance contrast for particular elements
Q.69 Which of the following best describes the role of “collimation” in reducing patient dose?
Increasing mA
Limiting the size of the X‑ray field to the area of interest
Increasing exposure time
Using higher kVp
Explanation - Collimation reduces the volume of tissue irradiated and minimizes scatter, thereby lowering dose.
Correct answer is: Limiting the size of the X‑ray field to the area of interest
Q.70 In dental radiography, the “bisecting angle technique” is used to:
Reduce patient dose
Obtain a true‑to‑scale image of the tooth
Correct geometric distortion due to angulation of the X‑ray beam
Increase image contrast
Explanation - The bisecting angle method compensates for the divergence of the beam relative to the tooth’s long axis.
Correct answer is: Correct geometric distortion due to angulation of the X‑ray beam
Q.71 Which of the following parameters most directly influences the “contrast agent attenuation” in an X‑ray image?
Atomic number of the contrast element
Focal spot size
Patient age
Grid ratio
Explanation - Higher atomic number (e.g., iodine, barium) provides greater photoelectric absorption, increasing contrast.
Correct answer is: Atomic number of the contrast element
Q.72 The “detector quantum efficiency (DQE)” of an X‑ray detector measures:
The fraction of incident X‑ray photons that are effectively converted into useful image signal
The speed of image acquisition
The detector’s physical size
The tube voltage stability
Explanation - Higher DQE indicates better utilization of photons, leading to improved image quality at lower doses.
Correct answer is: The fraction of incident X‑ray photons that are effectively converted into useful image signal
Q.73 In CT imaging, the “pitch” of a helical scan is defined as:
The ratio of table movement per rotation to the total collimated beam width
The speed of the X‑ray tube rotation
The detector pixel size
The patient’s heart rate
Explanation - Pitch affects scan speed, dose, and image quality; a pitch >1 reduces overlap of slices.
Correct answer is: The ratio of table movement per rotation to the total collimated beam width
Q.74 Which of the following is a typical application of X‑ray imaging in industrial settings?
Detecting bone fractures
Inspecting welds for internal defects
Measuring blood pressure
Monitoring heart rhythm
Explanation - Non‑destructive testing uses X‑rays to reveal internal flaws in metal structures and assemblies.
Correct answer is: Inspecting welds for internal defects
Q.75 The term “modulation transfer function (MTF)” is used to describe:
The detector’s ability to reproduce varying levels of contrast at different spatial frequencies
The patient’s dose distribution
The speed of the X‑ray tube
The contrast agent concentration
Explanation - MTF quantifies spatial resolution performance; higher MTF at a given frequency indicates better detail reproduction.
Correct answer is: The detector’s ability to reproduce varying levels of contrast at different spatial frequencies
Q.76 Which of the following is NOT an advantage of using a “grid” with a high grid ratio (e.g., 12:1) in radiography?
Improved image contrast
Increased patient dose
Reduced scatter radiation
Better image sharpness
Explanation - High‑ratio grids improve contrast by reducing scatter but do not directly affect spatial resolution (sharpness).
Correct answer is: Better image sharpness
Q.77 In digital radiography, a “raw image” refers to:
An image after all processing and enhancement
The unprocessed data directly from the detector before any corrections
A printed film copy
An image that has been compressed to JPEG
Explanation - Raw data retain the original detector signal; post‑processing applies corrections like flat‑fielding and scaling.
Correct answer is: The unprocessed data directly from the detector before any corrections
Q.78 Which of the following best describes the role of “scatter correction algorithms” in CT reconstruction?
They increase the kVp automatically
They estimate and subtract scattered photons to improve image uniformity
They shorten the scan time
They enlarge the field of view
Explanation - Scatter correction algorithms model scatter distribution and remove its contribution, reducing artifacts.
Correct answer is: They estimate and subtract scattered photons to improve image uniformity
Q.79 The “dose‑area product (DAP)” is a quantity used to assess:
The total energy delivered to a specific point in tissue
The total radiation dose multiplied by the irradiated area, reflecting overall patient exposure
The image contrast
The speed of the detector
Explanation - DAP (Gy·cm²) accounts for both dose and field size, useful for comparing overall exposure across procedures.
Correct answer is: The total radiation dose multiplied by the irradiated area, reflecting overall patient exposure
Q.80 In an X‑ray tube, the “anode heat capacity” is important because:
It determines the focal spot size
It limits the maximum tube voltage
It dictates how much heat can be absorbed before cooling is required, affecting exposure time
It controls the beam filtration
Explanation - Higher heat capacity allows longer exposures or higher mA without overheating the anode.
Correct answer is: It dictates how much heat can be absorbed before cooling is required, affecting exposure time
Q.81 Which of the following describes a “metal artifact” in CT imaging?
Uniform bright area due to high photon flux
Streaks and dark bands caused by beam hardening and photon starvation near high‑density objects
Increased image noise due to low mAs
Motion blur of soft tissues
Explanation - Metal objects attenuate X‑rays heavily, leading to reconstruction errors and characteristic streak artifacts.
Correct answer is: Streaks and dark bands caused by beam hardening and photon starvation near high‑density objects
Q.82 The primary reason for using “soft‑tissue windows” (e.g., lung window) when viewing CT images is:
To increase the radiation dose
To adjust the display range to highlight subtle differences in attenuation of soft tissues
To reduce scan time
To change the physical slice thickness
Explanation - Windowing selects a specific Hounsfield Unit range, enhancing contrast for particular tissue types.
Correct answer is: To adjust the display range to highlight subtle differences in attenuation of soft tissues
Q.83 Which of the following is a limitation of conventional film‑screen radiography compared to digital radiography?
Higher dynamic range
Immediate image preview
Ability to post‑process images
Higher sensitivity to low doses
Explanation - Film requires processing before viewing, whereas digital systems provide instant images.
Correct answer is: Immediate image preview
Q.84 In X‑ray imaging, the “receptor” refers to:
The X‑ray tube cathode
The part of the patient that absorbs the beam
The device that captures the transmitted X‑ray photons to form an image
The shielding wall surrounding the room
Explanation - The receptor can be film, phosphor plate, or digital detector that records the image.
Correct answer is: The device that captures the transmitted X‑ray photons to form an image
Q.85 Which of the following best explains why higher atomic number (Z) materials are used as contrast agents in X‑ray imaging?
They emit X‑rays when excited
They increase photon scattering
They increase photoelectric absorption, enhancing contrast
They reduce the need for filtration
Explanation - High‑Z elements like iodine have a greater probability of photoelectric interaction, attenuating X‑rays more strongly.
Correct answer is: They increase photoelectric absorption, enhancing contrast
Q.86 The “field of view (FOV)” in a CT scan refers to:
The total radiation dose delivered
The diameter of the scanned area that appears in the reconstructed images
The speed of the gantry rotation
The thickness of each image slice
Explanation - FOV determines the anatomical coverage and influences spatial resolution.
Correct answer is: The diameter of the scanned area that appears in the reconstructed images
Q.87 Which of the following best describes the phenomenon of “edge enhancement” used in digital image processing?
Increasing overall image brightness
Sharpening image borders to improve perceived detail
Reducing patient dose
Eliminating motion artifacts
Explanation - Edge enhancement accentuates transitions between areas of differing intensity, making edges appear clearer.
Correct answer is: Sharpening image borders to improve perceived detail
Q.88 In pediatric radiography, the “body size‑specific protocol” primarily adjusts:
kVp only
mAs based on patient thickness
Focal spot size
Collimation width
Explanation - Modulating mAs according to size ensures adequate exposure while minimizing dose for smaller patients.
Correct answer is: mAs based on patient thickness
Q.89 Which of the following is a common cause of “image ghosting” in analog fluoroscopy systems?
Insufficient tube voltage
Residual phosphor emission after exposure
Too high mA
Over‑collimation
Explanation - Phosphor screens may continue to emit light briefly after exposure, creating a ghost image if frames are captured rapidly.
Correct answer is: Residual phosphor emission after exposure
Q.90 The “inverse square law” is most critical when:
Choosing the tube voltage
Positioning the patient relative to the X‑ray source for dose reduction
Setting the focal spot size
Selecting the contrast agent
Explanation - Doubling the distance from the source reduces intensity to one quarter, directly affecting dose and exposure.
Correct answer is: Positioning the patient relative to the X‑ray source for dose reduction
Q.91 Which of the following best describes the term “radiographic density” on a film image?
The thickness of the patient’s tissue
The darkness of the image, proportional to the amount of radiation received
The energy of the X‑ray photons
The size of the X‑ray field
Explanation - Higher density (darker area) indicates more exposure at that point on the film.
Correct answer is: The darkness of the image, proportional to the amount of radiation received
Q.92 In CT imaging, a “high‑resolution” (HRCT) protocol is primarily used to evaluate:
Large abdominal organs
Fine lung parenchymal details
Bone mineral density
Cardiac function
Explanation - HRCT uses thin slices and high spatial resolution to assess interstitial lung disease and small airway pathology.
Correct answer is: Fine lung parenchymal details
Q.93 Which of the following is a typical feature of a “digital radiography (DR) system” that distinguishes it from “computed radiography (CR)”?
Use of photostimulable phosphor plates
Immediate image acquisition without a separate scanning step
Requirement of chemical processing
Dependence on film development
Explanation - DR captures images directly on a solid‑state detector, eliminating the plate‑scanning step required in CR.
Correct answer is: Immediate image acquisition without a separate scanning step
Q.94 In X‑ray imaging, the term “exposure index (EI)” is used to:
Measure the radiation dose delivered to the patient
Quantify the detector’s response to a standard exposure for quality control
Adjust the focal spot size automatically
Determine the optimal kVp
Explanation - EI provides a numeric value indicating whether the detector received an appropriate exposure, aiding in dose management.
Correct answer is: Quantify the detector’s response to a standard exposure for quality control
Q.95 Which of the following best explains why “anti‑scatter grids” are not used in all X‑ray examinations (e.g., pediatric chest)?
Grids increase patient dose, which may not be justified for low‑contrast exams in children
Grids cause motion blur
Grids reduce image resolution
Grids are only compatible with film systems
Explanation - Because grids absorb primary photons as well as scatter, they raise dose; in pediatric exams the dose increase may outweigh the contrast benefit.
Correct answer is: Grids increase patient dose, which may not be justified for low‑contrast exams in children
Q.96 The “Gantry tilt” feature in a CT scanner is primarily used to:
Reduce radiation dose
Avoid artifacts from the shoulder girdle when imaging the neck
Increase the scan speed
Change the image reconstruction algorithm
Explanation - Tilting the gantry moves the shoulders out of the scan plane, reducing beam hardening and streak artifacts in cervical spine imaging.
Correct answer is: Avoid artifacts from the shoulder girdle when imaging the neck
Q.97 Which of the following statements about “beam hardening correction” in CT is TRUE?
It eliminates all artifacts in the image
It involves calibrating the scanner with water phantoms and applying correction algorithms
It increases the patient's radiation dose
It only works for low‑kVp scans
Explanation - Beam hardening correction uses calibration data to adjust for non‑linear attenuation, reducing cupping and streak artifacts.
Correct answer is: It involves calibrating the scanner with water phantoms and applying correction algorithms
Q.98 In an X‑ray imaging system, “pixel size” of the detector directly influences:
Patient dose
Spatial resolution of the image
Tube voltage
Contrast agent concentration
Explanation - Smaller pixels can resolve finer details, enhancing spatial resolution, assuming other factors (e.g., focal spot) are adequate.
Correct answer is: Spatial resolution of the image
Q.99 The “C‑arm” in interventional radiology is named for its:
Circular shape resembling the letter C
Capability to rotate 360° around the patient
Use of C‑shaped X‑ray tube and detector assembly allowing flexible positioning
Compact size for bedside use
Explanation - The C‑arm’s shape provides a movable, semi‑circular geometry, facilitating access to various patient positions.
Correct answer is: Use of C‑shaped X‑ray tube and detector assembly allowing flexible positioning
Q.100 Which of the following best defines “radiographic exposure time” (seconds)?
The duration for which the X‑ray tube is energized during an image acquisition
The time the patient remains in the room
The time needed to process a film
The interval between two consecutive exposures
Explanation - Exposure time, together with mA, determines the total number of electrons (and thus X‑rays) produced.
Correct answer is: The duration for which the X‑ray tube is energized during an image acquisition
Q.101 In CT imaging, the term “partial volume effect” refers to:
Loss of signal due to patient motion
Blurring caused by large focal spots
Apparent averaging of different tissue densities within a single voxel
Increase in dose due to overlapping scans
Explanation - When a voxel contains multiple tissue types, the measured attenuation is a weighted average, reducing contrast of small structures.
Correct answer is: Apparent averaging of different tissue densities within a single voxel
Q.102 Which of the following is an example of a “non‑ionizing” imaging modality, often used as an alternative to X‑rays for soft‑tissue evaluation?
Ultrasound
Computed Tomography (CT)
Mammography
Fluoroscopy
Explanation - Ultrasound uses high‑frequency sound waves, not ionizing radiation, making it safe for many soft‑tissue applications.
Correct answer is: Ultrasound
Q.103 The “Bucky‑POT” system in radiography is primarily used to:
Increase the tube voltage
Move the anti‑scatter grid during exposure to blur grid lines
Cool the X‑ray tube
Automate patient positioning
Explanation - The Bucky‑POT oscillates the grid, reducing the visibility of grid lines while maintaining scatter reduction.
Correct answer is: Move the anti‑scatter grid during exposure to blur grid lines
Q.104 Which of the following best explains why “high‑resolution detectors” often have lower detective quantum efficiency (DQE) at high spatial frequencies?
Because they use larger pixels
Because increased electronic noise dominates at fine detail levels
Because they require higher kVp
Because they are made of lower‑Z materials
Explanation - At high spatial frequencies, signal levels are low, so electronic noise reduces the effective DQE.
Correct answer is: Because increased electronic noise dominates at fine detail levels
Q.105 In X‑ray imaging, the “kVp‑mAs” product is important because it determines:
The size of the focal spot
The total number of X‑ray photons produced (exposure) and their energy (quality)
The speed of the image acquisition
The detector's pixel size
Explanation - kVp sets photon energy (quality), while mAs controls photon quantity (exposure). Their product influences both dose and image contrast.
Correct answer is: The total number of X‑ray photons produced (exposure) and their energy (quality)
Q.106 Which imaging technique employs a “dual‑source” configuration to improve temporal resolution in cardiac CT?
Single‑source CT
Dual‑source CT
Cone‑beam CT
Digital Subtraction Angiography
Explanation - Dual‑source CT uses two X‑ray tubes and detectors offset by 90°, allowing faster data acquisition and reduced motion artifacts.
Correct answer is: Dual‑source CT
Q.107 In radiography, the term “exposure factor” (EF) is defined as:
kVp ÷ mAs
kVp × mAs
kVp + mAs
kVp – mAs
Explanation - EF represents the overall exposure setting, combining tube voltage and tube current‑time product.
Correct answer is: kVp × mAs
Q.108 Which of the following best describes the purpose of “phase‑contrast X‑ray imaging”?
To increase patient dose for better images
To detect differences in the phase shift of X‑ray waves, enhancing soft‑tissue contrast
To speed up image acquisition
To replace the need for contrast agents
Explanation - Phase‑contrast techniques exploit variations in the refractive index, providing higher contrast for weakly absorbing tissues.
Correct answer is: To detect differences in the phase shift of X‑ray waves, enhancing soft‑tissue contrast
Q.109 In dental panoramic radiography, the “focal trough” refers to:
The region of sharp focus where anatomical structures are imaged with minimal distortion
The maximum exposure time allowed
The size of the X‑ray beam
The type of detector used
Explanation - The focal trough is a three‑dimensional curved zone where the image is acceptably sharp; structures outside this zone appear blurred.
Correct answer is: The region of sharp focus where anatomical structures are imaged with minimal distortion
Q.110 Which of the following is a typical indication for performing a “CT pulmonary angiography (CTPA)”?
Assessing bone density
Evaluating suspected pulmonary embolism
Screening for breast cancer
Diagnosing liver cirrhosis
Explanation - CTPA uses contrast‑enhanced CT to visualize pulmonary arteries and detect emboli.
Correct answer is: Evaluating suspected pulmonary embolism
Q.111 In X‑ray imaging, the term “scatter fraction” quantifies:
The proportion of primary photons that reach the detector
The ratio of scattered photons to total photons detected
The percentage of beam filtered by the anode
The speed of image acquisition
Explanation - Scatter fraction indicates how much of the detected signal originates from scatter, which degrades contrast.
Correct answer is: The ratio of scattered photons to total photons detected
Q.112 Which of the following best describes the effect of increasing the “grid ratio” (e.g., from 6:1 to 12:1)?
Decreases patient dose
Improves scatter reduction and image contrast, but requires higher exposure
Reduces image noise without changing dose
Widens the X‑ray beam
Explanation - Higher grid ratios block more scatter, increasing contrast but also absorbing more primary photons, necessitating higher mAs.
Correct answer is: Improves scatter reduction and image contrast, but requires higher exposure
Q.113 In X‑ray imaging, the “detector gain” is adjusted to compensate for:
Variations in tube voltage
Variations in patient size
Fluctuations in ambient temperature
Differences in detector quantum efficiency
Explanation - Gain amplification can be increased for larger patients (who attenuate more) to maintain adequate image brightness.
Correct answer is: Variations in patient size
Q.114 The “sinogram” is a term used in which imaging modality?
Mammography
Computed Tomography (CT)
Fluoroscopy
Ultrasound
Explanation - A sinogram records raw projection data (intensity versus angle) before reconstruction into cross‑sectional images.
Correct answer is: Computed Tomography (CT)
Q.115 Which of the following best explains why “low‑kVp” imaging improves soft‑tissue contrast?
It increases photon flux
It enhances the photoelectric effect, which is more Z‑dependent
It reduces scatter radiation
It shortens exposure time
Explanation - Lower photon energies increase photoelectric interactions, accentuating attenuation differences between soft tissues.
Correct answer is: It enhances the photoelectric effect, which is more Z‑dependent
Q.116 In X‑ray imaging, the term “over‑exposure” typically results in:
A pale image with low density
A dark image with high density and possible loss of detail in high‑attenuation areas
Increased motion blur
Improved spatial resolution
Explanation - Excess exposure saturates the detector/film, producing an overly dark image and reducing diagnostic information.
Correct answer is: A dark image with high density and possible loss of detail in high‑attenuation areas
Q.117 Which of the following is a primary benefit of using “iterative reconstruction” algorithms in CT?
Elimination of all motion artifacts
Reduction of image noise, allowing lower radiation dose
Increase in scan speed
Automatic patient positioning
Explanation - Iterative reconstruction models the imaging process more accurately, reducing noise and permitting dose reduction while preserving image quality.
Correct answer is: Reduction of image noise, allowing lower radiation dose
Q.118 In X‑ray imaging, the “air gap technique” is used to:
Increase the field of view
Reduce scatter by increasing the distance between patient and detector
Decrease patient dose by lowering kVp
Improve detector quantum efficiency
Explanation - An air gap allows scattered photons to diverge away from the detector, improving contrast, though it may increase geometric unsharpness.
Correct answer is: Reduce scatter by increasing the distance between patient and detector
Q.119 Which of the following best defines “spatial resolution” measured in line pairs per millimeter (lp/mm)?
The ability to differentiate between different X‑ray energies
The maximum number of line pairs that can be distinguished per millimeter of image
The speed at which an image can be acquired
The total radiation dose delivered
Explanation - Spatial resolution is quantified by the finest set of alternating dark and light lines (line pairs) that can be resolved.
Correct answer is: The maximum number of line pairs that can be distinguished per millimeter of image
Q.120 In a conventional X‑ray setup, what is the effect of increasing the source‑to‑image distance (SID) while keeping other parameters constant?
Increases geometric unsharpness
Decreases magnification and reduces geometric unsharpness
Increases patient dose
Reduces beam filtration
Explanation - A larger SID reduces the penumbra size, leading to sharper images with less magnification.
Correct answer is: Decreases magnification and reduces geometric unsharpness
Q.121 Which imaging modality utilizes “time‑resolved” X‑ray acquisition to capture rapid physiological processes, such as cardiac motion?
Fluoroscopy
Mammography
Dual‑energy X‑ray absorptiometry
Digital Subtraction Angiography
Explanation - Fluoroscopy provides real‑time X‑ray video, enabling visualization of moving structures like the heart.
Correct answer is: Fluoroscopy
Q.122 The “contrast‑to‑noise ratio (CNR)” improves when:
Image noise increases
Contrast between the structure and background decreases
Both contrast increases and noise decreases
Exposure time is reduced
Explanation - CNR is the ratio of the difference in signal between a feature and background to the image noise; higher contrast and lower noise raise CNR.
Correct answer is: Both contrast increases and noise decreases
Q.123 In X‑ray imaging, the term “kilogray (kGy)” is used to measure:
Radiation dose absorbed by tissue
Electric field strength of the tube
Photon energy
Exposure time
Explanation - The gray (Gy) is the SI unit for absorbed dose; 1 kGy = 1000 Gy.
Correct answer is: Radiation dose absorbed by tissue
Q.124 Which of the following best describes the purpose of a “lead apron” in X‑ray rooms?
To focus the X‑ray beam
To block scattered radiation and protect staff and patients from unnecessary exposure
To increase image contrast
To enhance detector sensitivity
Explanation - Lead aprons attenuate ionizing radiation, reducing dose to protected body parts.
Correct answer is: To block scattered radiation and protect staff and patients from unnecessary exposure
Q.125 In digital radiography, the term “flat‑field correction” refers to:
Adjusting the patient’s position
Compensating for non‑uniform detector response by using a uniform exposure image
Increasing the kVp
Reducing motion blur
Explanation - Flat‑field correction normalizes pixel variations, ensuring consistent image brightness across the detector.
Correct answer is: Compensating for non‑uniform detector response by using a uniform exposure image
Q.126 Which of the following is a typical advantage of using “cone‑beam CT (CBCT)” in dental imaging?
Higher radiation dose compared to conventional CT
Rapid 3‑D acquisition with lower dose and high spatial resolution for maxillofacial structures
Ability to image the entire body in one rotation
Real‑time video imaging of soft tissues
Explanation - CBCT provides detailed 3‑D images of teeth and jaws with relatively low radiation exposure.
Correct answer is: Rapid 3‑D acquisition with lower dose and high spatial resolution for maxillofacial structures
Q.127 In X‑ray imaging, “scatter correction” can also be achieved by:
Increasing kVp
Using anti‑scatter grids
Reducing exposure time
Widening the focal spot
Explanation - Grids absorb scattered photons, decreasing scatter reaching the detector and improving image contrast.
Correct answer is: Using anti‑scatter grids
Q.128 Which of the following best describes the function of “image receptor calibration” in digital radiography?
Setting the tube voltage
Ensuring consistent detector response across the field of view
Adjusting patient positioning
Increasing the focal spot size
Explanation - Calibration corrects pixel‑to‑pixel variations, providing uniform image quality.
Correct answer is: Ensuring consistent detector response across the field of view
Q.129 The “gantry” in a CT scanner houses which of the following components?
Patient table only
X‑ray tube and detector array that rotate around the patient
Image processing computer
Lead shielding wall
Explanation - The gantry is the rotating part that contains the X‑ray source and detectors for data acquisition.
Correct answer is: X‑ray tube and detector array that rotate around the patient
Q.130 In X‑ray imaging, the term “radiographic magnification factor” is calculated as:
SID ÷ SOD
SOD ÷ SID
kVp ÷ mAs
mA ÷ exposure time
Explanation - Magnification factor = Source‑to‑Image Distance divided by Source‑to‑Object Distance.
Correct answer is: SID ÷ SOD