1
Q
What is the primary function of the cathode in an x-ray tube?
A
Emit electrons toward the anode.
2
Q
What is the effect of using a smaller focal spot?
A
Improves spatial resolution.
3
Q
What is the main advantage of high-frequency generators?
A
More constant x-ray output and reduced exposure time.
4
Q
What is the typical composition of a protective lead apron?
A
Lead or lead-equivalent material.
5
Q
What does mA control in an x-ray exposure?
A
Number of electrons flowing from cathode to anode.
6
Q
What does kVp primarily affect in the x-ray beam?
A
Penetrating power and contrast.
7
Q
What is the primary interaction responsible for image formation in soft tissue?
A
Photoelectric effect.
8
Q
What is the common voltage used for general diagnostic radiography?
A
50–150 kVp.
9
Q
What is a common artifact caused by patient motion?
A
Blurring.
10
Q
What is the primary purpose of automatic exposure control (AEC)?
A
Maintain consistent image receptor exposure.
11
Q
What does a bucky tray do?
A
Holds the image receptor and may contain a grid to reduce scatter.
12
Q
Why is patient positioning critical in radiography?
A
Reduces distortion and improves diagnostic quality.
13
Q
What is the main safety concern with fluoroscopy?
A
Radiation dose to patient and staff.
14
Q
What is the principle of ALARA in practice?
A
Minimize time, maximize distance, and use shielding.
15
Q
Which imaging modality is most sensitive for detecting fractures?
A
CT.
16
Q
Which imaging modality uses sound waves?
A
Ultrasound.
17
Q
What is the unit of radiation exposure in air?
A
Coulomb per kilogram (C/kg) or Roentgen (R).
18
Q
What is the effect of scatter on image quality?
A
Reduces contrast and adds noise.
19
Q
Why is gonadal shielding used?
A
Protects reproductive organs from unnecessary radiation.
20
Q
What is the common thickness of lead in thyroid shields?
A
0.5 mm lead equivalent.
21
Q
What is the main purpose of collimation?
A
Limit beam to area of interest and reduce dose.
22
Q
What does PACS stand for?
A
Picture Archiving and Communication System.
23
Q
What does DICOM standardize?
A
Medical image formats and communication protocols.
24
Q
What is the principle of CT slice acquisition?
A
Sequential or helical scanning with reconstruction.
25
What does iterative reconstruction reduce in CT?
Noise and patient dose.
26
What is pitch in CT scanning?
Table movement per rotation divided by slice width.
27
What is the difference between CTDIvol and DLP?
CTDIvol measures dose per slice; DLP includes scan length.
28
What is the main advantage of multidetector CT (MDCT)?
Faster scans and thinner slices.
29
What is the role of contrast agents in imaging?
Enhance visibility of structures or vessels.
30
Which contrast agent is used in MRI?
Gadolinium-based agents.
31
Which contrast agent is used in CT?
Iodinated contrast.
32
Which patient factor affects contrast agent choice?
Renal function.
33
What is the main risk with iodinated contrast?
Allergic reaction or nephropathy.
34
What is the main risk with gadolinium?
Nephrogenic systemic fibrosis in renal failure.
35
What is the most radiosensitive organ in adults?
Bone marrow.
36
Which body part is most radiosensitive in children?
Thyroid and gonads.
37
What is the principle of beam hardening artifact?
Dense objects preferentially absorb low-energy photons.
38
What is a common MRI artifact caused by metal?
Susceptibility artifact.
39
What is the main difference between T1 and T2 MRI?
T1 shows fat bright; T2 shows fluid bright.
40
What is the main safety concern in MRI?
Projectile risk from ferromagnetic objects.
41
What is the principle of ultrasound imaging?
Sound waves reflect at tissue interfaces.
42
What affects ultrasound resolution?
Frequency and transducer size.
43
What is the advantage of Doppler ultrasound?
Measures blood flow velocity and direction.
44
Which nuclear medicine scan uses technetium-99m?
Bone scan, cardiac perfusion scan, thyroid scan.
45
What is the half-life of Tc-99m?
6 hours.
46
What is the main advantage of PET imaging?
Functional imaging of metabolic activity.
47
Which isotope is used in PET?
Fluorine-18.
48
What is the difference between SPECT and PET?
SPECT uses gamma emitters; PET uses positron emitters.
49
What is a dose-length product (DLP)?
CT dose multiplied by scan length.
50
What is a typical effective dose for a chest CT?
5–7 mSv.
51
What is the purpose of lead glasses?
Protect lens of eyes from scatter.
52
What is the main factor affecting radiation dose in fluoroscopy?
Fluoroscopy time and dose rate.
53
How can staff reduce exposure during fluoroscopy?
Increase distance, use shielding, reduce time.
54
What is the purpose of a dosimeter badge?
Monitor cumulative occupational radiation dose.
55
Where is a typical dosimeter badge worn?
At collar level outside lead apron.
56
What is the additional purpose of a second badge under the apron?
Estimate effective dose.
57
What is the common thickness of protective lead gloves?
0.25–0.5 mm lead equivalent.
58
What is the principle of inverse square law?
Intensity decreases proportionally to the square of distance from source.
59
What is the typical energy range for diagnostic x-rays?
30–150 kVp.
60
What is the effect of increasing kVp on patient dose?
Dose decreases for same image quality due to higher penetration.
61
What is the effect of increasing mAs on patient dose?
Dose increases linearly.
62
What is the main cause of quantum mottle in digital imaging?
Insufficient photon count.
63
What is the purpose of beam filtration?
Remove low-energy photons that contribute dose but not image.
64
What is the main function of the cathode filament?
Emit electrons when heated.
65
What is the effect of focal spot blooming?
Reduces image sharpness at high mA.
66
What is the primary difference between CR and DR?
CR uses cassettes with imaging plates; DR uses flat-panel detectors.
67
What is the common cause of moiré pattern?
Grid frequency interference with digital sampling.
68
What is the principle of AEC backup timer?
Prevent overexposure if AEC fails.
69
Which modality uses ionizing radiation?
X-ray, CT, nuclear medicine.
70
Which modality does not use ionizing radiation?
MRI, ultrasound.
71
What is the effect of patient thickness on exposure?
Thicker patients require higher exposure.
72
What is the main purpose of compression in mammography?
Reduce motion, improve image quality, reduce dose.
73
What is the main function of the collimator light field?
Align x-ray beam with anatomy of interest.
74
What is the principle of kilovoltage peak (kVp)?
Controls energy of x-ray photons and contrast.
75
What is a common artifact in digital radiography?
Detector lag, ghosting, or stitching errors.
76
What is the main advantage of flat-panel detectors over CR?
Faster acquisition and better spatial resolution.
77
What is a typical fluoroscopy frame rate for real-time imaging?
15–30 fps.
78
What is the main effect of increasing filtration on image?
Slightly reduces contrast, reduces skin dose.
79
What is the principle of dynamic range in digital radiography?
Ability to record wide range of exposure levels.
80
What is the purpose of repeat analysis in QC?
Identify causes of repeat exposures to reduce dose.
81
What is a common safety measure during mobile x-ray?
Use distance, lead shields, and minimize exposure.
82
What is the principle of CT iterative reconstruction?
Use algorithms to reduce noise and dose while maintaining image quality.
83
What is the principle of contrast-to-noise ratio (CNR)?
Difference in signal between structure and background relative to noise.
84
What is the purpose of image post-processing?
Enhance visualization, adjust window/level, remove artifacts.
85
What is the effect of grid misalignment?
Grid cutoff or uneven density.
86
What is the purpose of angulation in x-ray projections?
Avoid superimposition and visualize structures.
87
What is the main safety concern with portable x-ray units?
Scatter to staff and bystanders.
88
What is the typical use of a wedge filter?
Compensate for uneven anatomy thickness.
89
What is the function of a beam splitter in nuclear medicine cameras?
Direct scintillation photons to detectors.
90
What is the principle of photon counting detectors?
Count individual photons to improve image quality and reduce dose.
91
What is a common artifact in PET imaging?
Patient motion blur or attenuation correction errors.
92
What is the purpose of ROI (region of interest) in imaging?
Quantitative measurement of signal or dose.
93
What is the main safety check before administering contrast?
Check allergies, renal function, pregnancy.
94
What is the effect of metal implants on CT imaging?
Streak artifacts due to beam hardening.
95
What is the main determinant of radiation exposure in CT?
mA, kVp, scan length, and pitch.
96
What is the purpose of dose modulation in CT?
Adjust tube current according to patient size to reduce dose.
97
What is a common artifact in ultrasound?
Reverberation, shadowing, or mirror image.
98
What is the principle of time-of-flight in PET?
Improves localization of annihilation events.
99
What is the typical half-life of F-18?
110 minutes.
100
What is the role of quality control in radiography?
Ensure image quality and radiation safety.
101
What is the principle of scatter radiation protection?
Use shielding, collimation, and distance.
102
What is the main effect of motion in MRI?
Blurring and ghosting artifacts.
103
What is the function of the gradient coils in MRI?
Spatial encoding of the signal.
104
What is the function of RF coils in MRI?
Transmit and receive radiofrequency signals.
105
What is the principle of T2* imaging?
Sensitive to magnetic field inhomogeneity.
106
What is the effect of slice thickness on spatial resolution?
Thinner slices improve resolution but increase noise.
107
What is the main source of occupational exposure in nuclear medicine?
Handling radiopharmaceuticals.
108
What is the effect of table height in fluoroscopy?
Affects magnification and dose.
109
What is the main advantage of digital mammography over film-screen?
Better contrast, post-processing, and lower dose.
110
What is the purpose of exposure index in digital imaging?
Indicates if correct exposure was used.
111
What is the effect of beam filtration on patient dose?
Reduces skin dose by removing low-energy photons.
112
What is the main artifact in DR from detector defects?
Dead pixels or lines.
113
What is the purpose of QA phantom tests?
Assess image quality parameters like resolution and contrast.
Radiography
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