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Question 1. Which component of the X‑ray tube is primarily responsible for producing the electron stream that strikes the anode? A) Focusing cup B) Filament (cathode) C) Target material D) High‑voltage transformer Answer: B Explanation: The filament is heated to emit electrons via thermionic emission; these electrons are then accelerated toward the anode. Question 2. The anode heel effect results in which of the following variations across the X‑ray field? A) Increased intensity on the cathode side B) Uniform intensity across the field C) Decreased intensity on the cathode side D) Decreased intensity on the anode side Answer: D Explanation: The heel effect causes the X‑ray intensity to be greater on the cathode side and reduced on the anode side due to absorption within the anode material. Question 3. In the X‑ray spectrum, characteristic radiation is produced when: A) Electrons are decelerated in the target material
B) Electrons knock out inner‑shell electrons of the target atom C) Photons are absorbed by the patient’s tissues D) High‑energy photons convert into electron‑positron pairs Answer: B Explanation: Characteristic radiation occurs when an incident electron ejects an inner‑shell electron, and an outer‑shell electron fills the vacancy, emitting a photon with energy equal to the difference between the shells. Question 4. Which factor most directly influences the penetrating ability (quality) of an X‑ray beam? A) Milliamperage (mA) B) Kilovoltage peak (kVp) C) Exposure time D) Filtration thickness Answer: B Explanation: kVp determines the maximum photon energy and thus the beam’s penetrating power; higher kVp yields a more penetrating beam. Question 5. Adding a 2 mm aluminum filter to an X‑ray beam will primarily: A) Increase patient dose by adding low‑energy photons B) Decrease image contrast by removing high‑energy photons C) Remove low‑energy photons, reducing patient skin dose
Explanation: Compton scattering predominates at the photon energies used in diagnostic radiology (30–150 keV) and is the main source of scatter. Question 8. According to the Law of Bergonie and Tribondeau, which cells are most radiosensitive? A) Mature neurons B) Fully differentiated fibroblasts C) Lymphocytes in the S‑phase D) Skeletal muscle cells Answer: C Explanation: Cells that are undifferentiated, rapidly dividing, and have a high mitotic rate (e.g., lymphocytes) are most radiosensitive. Question 9. The deterministic effect of radiation with a threshold dose is: A) Cancer induction B) Genetic mutation C) Cataract formation D) Stochastic DNA damage Answer: C Explanation: Deterministic effects, such as cataracts, have a threshold dose below which the effect does not occur; severity increases with dose above the threshold.
Question 10. The ALARA principle is best achieved by optimizing which three factors? A) Time, distance, shielding B) kVp, mAs, SID C) Filtration, grid ratio, collimation D) Contrast, resolution, noise Answer: A Explanation: ALARA (As Low As Reasonably Achievable) relies on minimizing exposure time, maximizing distance from the source, and using appropriate shielding. Question 11. For occupational monitoring, which dosimeter type uses optically stimulated luminescence? A) Film badge B) Thermoluminescent dosimeter (TLD) C) OSL badge D) Pocket ion chamber Answer: C Explanation: OSL (Optically Stimulated Luminescence) dosimeters store dose information in crystal traps and are read by stimulating with light. Question 12. The annual occupational effective dose limit for a pregnant radiologic technologist (excluding the fetus) is:
B) Pulsed fluoroscopy with low pulse rate C) Increasing focal spot size D) Reducing collimation width Answer: B Explanation: Pulsed fluoroscopy delivers X‑rays only during short pulses, reducing overall dose compared with continuous exposure. Question 15. The primary function of an intensifying screen in film‑screen radiography is to: A) Convert X‑ray photons into visible light B) Increase the film’s speed by absorbing scattered photons C) Reduce the need for a protective lead apron D) Provide a digital read‑out of the image Answer: A Explanation: The screen’s phosphor layer absorbs X‑ray photons and re‑emits them as visible light, exposing the film more efficiently. Question 16. In computed radiography (CR), the latent image is stored as: A) Trapped electrons in a photostimulable phosphor layer B) Chemical changes in a silver halide emulsion C) Magnetic domains on a hard‑disk platter D) Voltage differences across a CCD sensor
Answer: A Explanation: CR plates contain photostimulable phosphor crystals that trap electrons when exposed to X‑rays; these are later released by a laser during scanning. Question 17. A direct‑conversion flat‑panel detector (FPD) uses which material to convert X‑ray photons directly to electrical charge? A) Cesium iodide (CsI) scintillator B) Amorphous selenium (a‑Se) C) Gadolinium oxysulfide (GOS) D) Silicon photodiodes Answer: B Explanation: Amorphous selenium directly converts X‑ray photons into electron‑hole pairs without an intermediate light‑producing step. Question 18. In digital imaging, the histogram is primarily used to: A) Measure patient dose B) Display the distribution of pixel gray levels C) Determine the focal spot size D) Calculate the exposure index Answer: B Explanation: A histogram plots the number of pixels at each gray level, helping assess image contrast and exposure.
A) Source‑to‑image distance (SID) B) Object‑to‑image distance (OID) C) Focal spot size D) Grid ratio Answer: B Explanation: Magnification = (SID + OID)/SID; thus, increasing OID increases magnification. Question 22. The primary purpose of a radiographic grid is to: A) Increase patient dose for better contrast B) Reduce scattered radiation reaching the image receptor C) Align the central ray with the anatomy D) Shorten exposure time Answer: B Explanation: Grids absorb scatter, improving image contrast at the cost of increased patient dose. Question 23. A focused grid is most beneficial when: A) The X‑ray tube is far from the patient (large SID) B) The patient is very thin C) The SID is short, increasing the angle of incident scatter
D) The exposure is performed at low kVp Answer: C Explanation: Focused grids have lead strips angled to match the diverging beam, reducing grid cutoff errors at short SID. Question 24. In an automatic exposure control (AEC) system, the “backup time” refers to: A) The maximum exposure time allowed if the detector does not reach the preset exposure B) The time required to reset the AEC circuit between exposures C) The delay before the X‑ray tube voltage rises D) The interval between successive exposures Answer: A Explanation: Backup time is the maximum exposure duration the AEC will allow before terminating the exposure if the preset detector signal is not achieved. Question 25. The term “contrast” in radiography most accurately describes: A) The difference in X‑ray intensity between the primary and scattered beams B) The difference in optical density between adjacent shades on the image C) The spatial resolution of the image D) The amount of patient motion during exposure Answer: B
Question 28. When positioning a PA chest radiograph, the central ray should be directed: A) 10 cm inferior to the clavicles B) 5 cm posterior to the sternum at the level of the 7th thoracic vertebra C) Through the middle of the clavicle at the level of the first intercostal space D) 2 cm lateral to the mid‑line at the level of the diaphragm Answer: B Explanation: For a PA chest, the CR is aimed at the mid‑sternum, 5 cm posterior to the skin, at the level of T7 to include the entire thorax. Question 29. In a lateral lumbar spine view, the patient should be positioned with the hips and shoulders: A) Parallel to the image receptor B) At 90° to each other (cross‑legged) C) Slightly rotated toward the image receptor to center the vertebral bodies D) In a flexed position to open the intervertebral spaces Answer: C Explanation: Slight rotation aligns the vertebral bodies centrally on the image, reducing distortion. Question 30. The “Decubitus” position is most useful for detecting: A) Pneumothorax on the right side
B) Fractures of the femur C) Foreign bodies in the gastrointestinal tract D) Pulmonary edema in supine patients Answer: A Explanation: A lateral decubitus view (patient lying on side) allows free air to rise, facilitating detection of pneumothorax. Question 31. The primary advantage of a “frog‑leg” lateral hip view is: A) Improved visualization of the femoral neck without superimposition of the pelvis B) Reduced radiation dose compared with AP pelvis C) Better detection of acetabular fractures D) Enhanced image of the sacroiliac joints Answer: A Explanation: The frog‑leg position rotates the femur outward, separating the femoral neck from the pelvis and improving its visualization. Question 32. When performing a hand PA view, the central ray should be directed at: A) The distal interphalangeal joint of the third digit B) The metacarpophalangeal joint of the second digit C) The midpoint of the third metacarpal bone
Explanation: Grid lines become visible when a CR plate is scanned with the grid still attached, imprinting the grid’s pattern onto the image. Question 35. In a skull Waters view, the central ray is directed at which anatomical landmark? A) The nasion B) The external auditory meatus (EAM) C) The orbital rim D) The occipital protuberance Answer: B Explanation: The Waters view uses a 30° caudal angulation with the CR aimed at the EAM to visualize the maxillary sinuses. Question 36. The primary reason to use a “C‑arm” in interventional radiology is: A) To provide high‑resolution CT images intra‑operatively B) To deliver a rotating X‑ray beam for 3‑D reconstruction C) To obtain real‑time fluoroscopic imaging with flexible positioning D) To replace conventional radiography for all exams Answer: C Explanation: A C‑arm provides mobile fluoroscopic imaging, allowing real‑time guidance during procedures.
Question 37. Which contrast medium is considered “negative” and primarily displaces air in the gastrointestinal tract? A) Barium sulfate suspension B) Iodinated water‑soluble contrast C) Carbon dioxide gas D) Gadolinium‑based agent Answer: C Explanation: Negative contrast agents, such as carbon dioxide, replace air and appear radiolucent, outlining structures. Question 38. A patient develops a mild urticaria after receiving an iodinated contrast injection. The most appropriate immediate action is: A) Administer epinephrine intramuscularly B) Stop the injection and observe the patient C) Give a high‑dose corticosteroid intravenously D) Perform immediate hemodialysis Answer: B Explanation: Mild reactions (urticaria) are managed by stopping the injection and monitoring; severe reactions would require epinephrine. Question 39. In a digital radiography system, the detective quantum efficiency (DQE) is a measure of:
C) Motion blur D) Ring artifact Answer: B Explanation: Inadequate erasure leaves residual latent images, causing ghosting on subsequent exposures. Question 42. In PACS, the DICOM standard primarily defines: A) The compression algorithm for JPEG images B) The network protocol for transmitting medical images and related information C) The hardware specifications for image receptors D) The radiation dose limits for patients Answer: B Explanation: DICOM (Digital Imaging and Communications in Medicine) standardizes the format and transmission of medical images and associated data. Question 43. For a pediatric chest X‑ray, the recommended technique to reduce patient dose is: A) Increase kVp and decrease mAs B) Use a higher‑speed film C) Increase SID to 180 cm D) Apply a grid with a high ratio Answer: A
Explanation: Raising kVp reduces the required mAs for adequate exposure, lowering dose while maintaining image quality; pediatric protocols favor high kVp, low mAs techniques. Question 44. During a radiographic exposure, the “inverse square law” indicates that if the SID is increased from 100 cm to 150 cm, the intensity of the X‑ray beam at the image receptor will: A) Increase by 2.25 times B) Decrease to 2/3 of the original intensity C) Decrease to 44% of the original intensity D) Remain unchanged Answer: C Explanation: Intensity ∝ 1/(SID)²; (100/150)² = (2/3)² = 4/9 ≈ 44% of the original intensity. Question 45. In a lateral knee view, the central ray should be directed at: A) The medial femoral condyle B) The intercondylar notch C) The tibial tuberosity D) The midpoint of the patella Answer: B Explanation: Centering at the intercondylar notch provides optimal visualization of the entire knee joint.
