1
Q
How does increasing mAs affect receptor exposure?
A
Increase
2
Q
How does decreasing mAs affect receptor exposure?
A
Decrease
3
Q
How does increasing kVp affect receptor exposure?
A
Increase
4
Q
How does decreasing kVp affect receptor exposure?
A
Decrease
5
Q
How does increasing kVp affect image contrast?
A
Decrease
6
Q
How does decreasing kVp affect image contrast?
A
Increase
7
Q
How does increasing kVp affect subject contrast? Why?
A
Decrease
Due to scatter from PT
8
Q
How does decreasing kVp affect subject contrast? Why?
A
Increase
Due to scatter from PT
9
Q
How does increasing OID affect image contrast?
A
Increase
10
Q
What can increasing OID be used for?
A
Air gap technique
11
Q
How does increasing OID affect spatial resolution
A
Decrease
12
Q
How does increasing OID affect distortion? If yes, what kind
A
Increase (magnification)
13
Q
How does increasing SID affect receptor exposure
A
Decrease
14
Q
How does decreasing SID affect receptor exposure
A
Increase
15
Q
How does increasing SID affect spatial resolution
A
Increase
16
Q
How does decreasing SID affect spatial resolution
A
Decrease
17
Q
How does increasing SID affect distortion
A
Decrease
18
Q
How does decreasing SID affect distortion
A
Increase
19
Q
How does increasing focal spot size affect spatial resolution
A
Decrease
20
Q
How does decreasing focal spot size affect spatial resolution
A
Increase
21
Q
How does increasing grid ratio affect receptor exposure (*assume no technique compensation unless otherwise indicated)
A
Decrease
22
Q
How does decreasing grid ratio affect receptor exposure (*assume no technique compensation unless otherwise indicated)
A
Increase
23
Q
How does increasing grid ratio affect image contrast
A
Increase
24
Q
How does decreasing grid ratio affect image contrast
A
Decrease
25
How does increasing tube filtration (excessive) affect receptor exposure
Decrease
26
How does decreasing tube filtration (insufficient) affect receptor exposure
Increase
27
How does increasing tube filtration (excessive) affect image contrast
Decrease
28
How does decreasing tube filtration (insufficient) affect image contrast
Increase
29
How does increasing beam restriction (collimation) affect receptor exposure
Decrease
30
How does decreasing beam restriction (collimation) affect receptor exposure
Increase
31
How does increasing beam restriction (collimation) affect image contrast
Increase
32
How does decreasing beam restriction (collimation) affect image contrast
Decrease
33
How does the presence of motion affect spatial resolution
Decrease
34
How does the presence of the anode heel effect affect receptor exposure from the anode side
Decrease
35
How does the presence of the anode heel effect affect receptor exposure from the cathode side
Increase
36
How does increasing patient factors affect receptor exposure
Decrease
37
How does decreasing patient factors affect receptor exposure
Increase
38
How does increasing patient factors affect image contrast
Decrease
39
How does decreasing patient factors affect image contrast
Increase
40
How does increasing patient factors affect subject contrast
Decrease
41
How does decreasing patient factors affect subject contrast
Increase
42
How does increasing patient factors affect distortion
Increase
43
How does decreasing patient factors affect distortion
Decrease
44
How does increasing angle (tube, part, patient) affect spatial resolution
Decrease
45
How does increasing angle (tube, part, patient) affect distortion? If yes, what kind?
Increase (shape)
46
Angling what causes elongation
Tube
47
Angling what causes foreshortening
Part or IR
48
What is an exposure indicator?
A numerical value that indicates the level of radiation exposure to a digital image receptor.
49
What does the exposure indicator represent in CR and DR systems?
The exposure level received by the imaging plate, image receptor, or flat panel detector.
50
Are exposure indicator values the same for all systems?
No, they are vendor-specific.
51
What is quantum noise (mottle)?
Visible brightness or density fluctuations on an image caused by too few photons reaching the image receptor.
52
What happens to quantum noise when fewer x-ray photons reach the IR?
Quantum noise increases.
53
What causes quantum mottle to be more visible?
Underexposure and low mAs.
54
What happens with severe overexposure or underexposure?
Loss of image contrast.
55
What is saturation in digital imaging?
Excessive overexposure resulting in burned-out areas that cannot be corrected with post-processing.
56
What is “dynamic range” in digital imaging?
The range of exposures that a detector can accurately capture.
57
What happens when exposure exceeds the dynamic range?
Image data cannot be accurately reproduced, leading to saturation or data loss.
58
What should be done if a chest image displays saturation in the lung fields?
The image must be repeated using decreased technique.
59
What is contrast in radiography?
The visible difference between any two selected areas of brightness on a radiographic image.
60
What determines image contrast in digital systems?
The processing algorithm.
61
What is a default algorithm?
The preset processing code that determines initial image display contrast and brightness.
62
What is grayscale?
The number of brightness levels or shades of gray visible in an image, related to system bit depth.
63
Which contrast scale: slight differences between shades of grey
Long/low contrast
64
Which contrast scale:
major differences between shades of grey
Short/high contrast
65
Which contrast scale:
more number of grey shades
Long/low contrast
66
Which contrast scale:
less number of grey shades
Short/high contrast
67
What is spatial resolution?
The sharpness of structural edges in an image; the smallest detail that can be detected.
68
What determines spatial resolution?
Pixel size and pixel pitch.
69
What happens to spatial resolution when pixel size increases?
Spatial resolution decreases.
70
What happens to spatial resolution when pixel size decreases?
Spatial resolution increases.
71
What happens to spatial resolution when pixel pitch increases?
Spatial resolution decreases.
72
What happens to spatial resolution when pixel pitch decreases?
Spatial resolution increases.
73
What happens to spatial resolution when OID (object-to-image distance) increases?
Spatial resolution decreases.
74
What happens to spatial resolution when OID decreases?
Spatial resolution increases.
75
What happens to spatial resolution when SID (source-to-image distance) increases?
Spatial resolution increases.
76
What happens to spatial resolution when SID decreases?
Spatial resolution decreases.
77
What happens to spatial resolution when focal spot size increases?
Spatial resolution decreases.
78
What happens to spatial resolution when focal spot size decreases?
Spatial resolution increases.
79
How does motion affect spatial resolution?
Motion decreases sharpness and spatial resolution.
80
What causes magnification and loss of sharpness?
Increased OID or decreased SID.
81
What is distortion?
Any geometric misrepresentation of an anatomic structure on an image.
82
What causes size distortion (magnification)?
Increased OID or decreased SID.
83
What is the result of size distortion?
The anatomic structure appears larger than its actual size.
84
What causes shape distortion?
Misalignment of the x-ray tube, body part, or image receptor.
85
What are the two types of shape distortion?
Elongation and foreshortening.
86
What causes elongation?
Improper angulation or alignment of the tube, part, or IR along the long axis of the part.
87
What causes foreshortening?
Angulation against the long axis of the part.
88
How do you calculate magnification factor (MF)?
Image size/object size = SID/SOD
89
What should all radiographs include?
Anatomical side markers (R/L), patient name, date, and institution information.
90
What type of anatomical markers must be used?
Radiopaque right or left markers.
91
Where should markers be placed?
Inside the collimation field, but not obstructing anatomy.
92
What additional patient data should appear digitally on the image?
Name, date of exam, MRN or accession number, DOB, and facility name.
93
What is an image artifact?
Any false visual feature on an image that simulates or obscures anatomy.
94
What are the three classifications of artifacts in DR?
Image receptor artifacts, software artifacts, and object artifacts.
95
What causes image receptor artifacts?
Rough handling, scratches, dust, or incomplete erasure of imaging plates.
96
What's the image receptor artifact?
Dust on the 3rd phalage
97
What's the image receptor artifact?
CR plate coming apart/damage and peeling
98
What are ghost images?
Artifacts caused by incomplete erasure of a previous image on a CR plate.
99
How can ghost images be corrected?
By performing an additional erasure cycle.
100
What should be done if a CR plate has not been used for 24 hours?
It should be erased before use.
101
What causes software artifacts?
Errors in image pre-processing, post-processing, or image compression.
102
What is image compression used for?
To reduce file size and improve transmission time for archiving or PACS systems.
103
What problem can result from image compression?
Compression artifacts may cause CAD or archiving systems to miss lesions due to data loss.
104
What causes object artifacts?
Technologist errors such as poor positioning, improper collimation, or incorrect histogram selection.
105
What happens if the wrong histogram is used (e.g., PA chest selected for abdomen)?
The image may appear too light, dark, or noisy due to incorrect reconstruction.
106
What is an exposure field recognition error?
An error caused by improper collimation or positioning that leads to inaccurate histogram analysis.
107
What do exposure field errors result in?
Images that are too dark, too light, or have excessive noise.
108
What are patient artifacts?
Artifacts caused by clothing, jewelry, or items in the imaging area that are not part of the anatomy of interest.
109
What is radiation fog?
Unwanted image exposure that does not contribute diagnostic information.
110
What causes radiation fog?
Scatter radiation reaching the IR or leaving imaging plates in the room during exposure.
111
Why are digital IRs more sensitive to fog?
They detect lower levels of radiation intensity than film systems.
112
What effect does fog have on an image?
Decreases image contrast.
113
What are the two types of digital imaging systems?
Cassette-based computed radiography (CR) and cassetteless direct or indirect digital radiography (DR).
114
What is computed radiography (CR)?
A digital imaging system that uses cassettes containing imaging plates that must be read by a scanner.
115
What is direct/indirect digital radiography (DR)?
A cassetteless imaging system that uses detector panels hardwired to the image processor.
116
Why must the correct exam or body part be selected on the workstation?
To ensure the proper lookup table (LUT) is applied for accurate rescaling and contrast.
117
What happens after a CR imaging plate is exposed?
It’s processed in a reader, where laser light releases stored energy and the signal is digitized.
118
What does the photomultiplier tube (PMT) do in CR?
Collects light and converts it to an electrical signal.
119
What is the function of the analog-to-digital converter (ADC)?
Converts the analog electrical signal into digital data.
120
What is an exposure recognition field algorithm?
A program that identifies the volume of interest (VOI) and shapes the histogram correctly before rescaling.
121
What is a DEL (detector element) in DR?
A pixel-sized element that detects radiation and converts it into an electric signal.
122
What does each DEL contain?
A thin-film transistor (TFT) that collects and transfers the signal.
123
What happens after exposure in DR?
Each DEL’s signal is sent to the computer and assigned a gray shade value for image creation.
124
What is a histogram?
A graphical representation of pixel values (gray levels) versus the number of pixels at each value.
125
What does the x-axis of the histogram represent?
The pixel gray shade values.
126
What does the y-axis of the histogram represent?
The number of pixels with each gray shade value.
127
What does the histogram represent in digital imaging?
The subject contrast from the remnant radiation.
128
What determines the shape of the histogram?
Total exposure factors — mainly kV and mAs.
129
What is a Type 1 histogram?
Used for extremity procedures — exposure area between anatomy and collimation border.
130
What is a Type 2 histogram?
Used for procedures like the abdomen — no raw exposure tail on the right side.
131
What is a Type 3 histogram?
Used when a large radiopaque object is in the field (e.g., contrast media or metal prosthesis).
132
What is a lookup table (LUT)?
A reference or “ideal” histogram stored in the system for each projection.
133
What does automatic rescaling do?
Adjusts the histogram of the acquired image to match the ideal LUT.
134
How does rescaling affect brightness?
Moves values left or right to match the LUT’s brightness level.
135
How does rescaling affect gray scale?
Adjusts values up or down to match the LUT’s contrast (gray range).
136
What happens if the image is too bright or too dark despite correct exposure?
A histogram or LUT selection error likely occurred.
137
What does the exposure indicator (EI) represent?
The amount of radiation intensity (photon quantity) that struck the image receptor.
138
Does EI indicate patient dose?
No — it only measures exposure to the detector, not absorbed dose.
139
How is the EI value determined?
By the median gray shade value (Sₐᵥₑ) of the VOI.
140
What is the technologist’s goal regarding EI?
To keep the EI value as close as possible to the system’s ideal.
141
What happens if the EI number is much higher than ideal?
The image is overexposed and the patient received unnecessary dose.
142
What happens if the EI number is much lower than ideal?
The image is underexposed and may show quantum noise.
143
What are histogram analysis errors?
Occur when the image histogram shape doesn’t match the expected analysis type.
144
What do histogram errors cause?
EI errors and projections that appear too light, dark, or have incorrect contrast.
145
What causes histogram analysis errors?
Wrong exam or body part selected, Incorrect centering or collimation, Presence of artifacts, Improper grid use or scatter control, Multiple exposures on one plate (CR).
146
What happens if the wrong exam is selected on the workstation?
The image is rescaled using the wrong LUT, resulting in incorrect brightness or contrast.
147
How can this be corrected?
By reprocessing with the correct LUT before sending to PACS.
148
Why is proper CR centering important?
Incorrect centering or excessive collimation alters the VOI and changes histogram shape.
149
How close should CR centering be to the VOI?
Within 0.5–1 inch.
150
How do external or internal artifacts affect the histogram?
They create unexpected “white” areas that shift the histogram curve to the left.
151
What is the effect of excessive scatter radiation?
It can distort the histogram and reduce contrast.
152
How can scatter be controlled?
Use proper collimation and a grid when appropriate.
153
What special issue applies only to computed radiography (CR)?
The need to clearly define the VOI and avoid multiple exposures on one plate.
154
What percent of the IR should be covered by anatomy in CR?
At least 30%.
155
What causes background radiation fogging on CR plates?
Leaving cassettes in the exam room or storage for too long without erasure.
156
What is IR exposure?
The amount of radiation that reaches the image receptor to form an image.
157
What controls IR exposure?
Primarily mAs, which determines the number of x-ray photons produced.
158
How are IR exposure and mAs related?
They are directly proportional — doubling mAs doubles IR exposure.
159
How does kVp affect IR exposure?
Increasing kVp increases exposure because of higher beam energy and penetration.
160
What happens to IR exposure if SID is increased?
It decreases — due to the inverse square law.
161
What happens to IR exposure if OID increases?
It decreases — due to greater beam divergence and air attenuation.
162
How do grids affect IR exposure?
Grids decrease IR exposure by absorbing scatter radiation.
163
How does collimation affect IR exposure?
Tight collimation reduces IR exposure by limiting the beam size and scatter.
164
What happens to IR exposure when patient part thickness increases?
It decreases, because thicker tissue absorbs more radiation.
165
How does filtration affect IR exposure?
Added filtration decreases IR exposure by removing low-energy photons.
166
What is brightness in digital imaging?
The lightness or darkness of the image as displayed on a monitor.
167
How is brightness controlled?
By the computer system and LUT processing, not by mAs.
168
Can brightness errors be corrected post-processing?
Yes — the system automatically adjusts it during rescaling.
169
Why must exposure still be accurate even though brightness can be fixed?
Because overexposure increases patient dose, and underexposure causes noise and data loss.
170
What is contrast?
The visible difference between any two selected areas of brightness in an image.
171
What determines image contrast in digital systems?
Primarily the LUT and processing algorithms, not kVp.
172
What is the difference between image contrast and subject contrast?
Subject contrast: The physical differences in tissue densities and kVp used. Image contrast: The final contrast displayed after processing.
173
What type of contrast does high kVp produce?
Low contrast (long scale of grays).
174
What type of contrast does low kVp produce?
High contrast (short scale of grays).
175
Can digital contrast be adjusted post-processing?
Yes — within limits, using window width adjustments.
176
What is quantum noise (mottle)?
A grainy or blotchy appearance on an image caused by too few x-ray photons reaching the IR.
177
What exposure factor most influences quantum noise?
mAs — underexposure (low mAs) causes quantum noise.
178
How does quantum noise affect image quality?
It decreases detail visibility and lowers diagnostic quality.
179
How can quantum noise be reduced?
Increase mAs or use appropriate exposure for the body part.
180
What happens if you try to fix quantum noise by adjusting contrast post-processing?
It can’t be corrected digitally — only prevented with adequate exposure.
181
What is the signal-to-noise ratio (SNR)?
The ratio of the meaningful image signal to the amount of noise present.
182
What happens when SNR is high?
Image quality improves — the signal (useful data) dominates over noise.
183
What happens when SNR is low?
The image appears grainy, with poor visibility of detail.
184
What is the best way to improve SNR?
Increase exposure (usually mAs).
185
What happens if SNR is increased too much?
Patient dose increases unnecessarily, even though image quality improves.
186
What is contrast-to-noise ratio (CNR)?
The ability of an imaging system to distinguish anatomic structures with similar contrast levels, despite background noise.
187
Why is high CNR important?
It ensures subtle tissue differences (like liver vs. spleen) are visible.
188
What decreases CNR?
Excessive noise or underexposure.
189
How can CNR be improved?
By increasing exposure or improving detector efficiency.
190
What is contrast resolution?
The system’s ability to distinguish small differences in tissue density or gray shades.
191
What determines contrast resolution in digital systems?
Bit depth — the number of bits used to represent each pixel.
192
How is bit depth related to gray shades?
More bits = more gray shades = higher contrast resolution.
193
What is the bit depth formula?
2ⁿ (where n = number of bits per pixel).
194
What bit depth range is typical in digital radiography?
10–16 bits per pixel (1,024–65,536 gray shades).
195
How does contrast resolution affect diagnostic visibility?
Higher contrast resolution allows subtle tissue differences to be seen clearly.
196
What is spatial resolution?
The ability of an imaging system to distinguish and display small details of an object — also known as recorded detail or sharpness.
197
What controls spatial resolution in digital imaging?
Pixel size and pixel pitch.
198
What determines pixel size?
The size of the detector element (DEL) in DR or matrix size in CR.
199
How does smaller pixel size affect spatial resolution?
Smaller pixels increase spatial resolution.
200
How does larger pixel size affect spatial resolution?
Larger pixels decrease spatial resolution.
201
What is pixel pitch?
The distance from the center of one pixel to the center of the adjacent pixel.
202
How does pixel pitch affect resolution?
Smaller pixel pitch increases resolution; larger pixel pitch decreases resolution.
203
What are the main geometric factors affecting spatial resolution?
OID, SID, and focal spot size.
204
What happens to spatial resolution when OID increases?
Resolution decreases (more magnification and unsharpness).
205
What happens to spatial resolution when OID decreases?
Resolution increases.
206
What happens to spatial resolution when SID increases?
Resolution increases (less magnification).
207
What happens to spatial resolution when SID decreases?
Resolution decreases.
208
What happens to spatial resolution when focal spot size increases?
Resolution decreases (more penumbra).
209
What happens to spatial resolution when focal spot size decreases?
Resolution increases (sharper detail).
210
What causes size distortion?
Changes in OID and SID.
211
How does increasing OID affect size distortion?
It increases magnification.
212
How does increasing SID affect size distortion?
It decreases magnification.
213
What is the ideal relationship between OID and SID to minimize magnification?
Use the smallest OID and largest SID possible.
214
What are the two types of motion in radiography?
Voluntary motion (controlled by the patient) and involuntary motion (caused by internal body processes).
215
How can voluntary motion be reduced?
Clear patient instructions, immobilization devices, or shorter exposure times.
216
How can involuntary motion be minimized?
Use of short exposure times and possibly higher mA.
217
Why is motion blur more noticeable in digital imaging?
Because digital detectors have high contrast resolution, making any loss of sharpness more visible.
218
What does 'visibility of detail' refer to?
The ability to see recorded structures clearly on the image.
219
What two major factors determine visibility of detail?
Image contrast and spatial resolution.
220
What happens to visibility of detail when noise increases?
It decreases — fine details become harder to see.
221
What two types of resolution affect image detail?
Contrast resolution and spatial resolution.
222
How can visibility of detail be optimized?
Use proper exposure, minimize motion, and maximize resolution by correct geometry and detector use.
223
What can cause a “halo” or edge enhancement artifact?
Over-processing or improper use of edge enhancement filters.
224
What happens when collimation is not properly applied?
The computer may misidentify the exposure field, leading to histogram analysis errors.
225
What happens if multiple exposures are made on one CR plate?
The computer cannot correctly identify the exposure fields, resulting in a processing error.
226
What can cause dark or light borders to appear around anatomy?
Improper collimation and exposure field recognition errors.
227
What is window width (WW)?
The range of pixel values displayed — controls image contrast.
228
What happens when window width is increased?
The image shows more gray shades (lower contrast).
229
What happens when window width is decreased?
The image shows fewer gray shades (higher contrast).
230
What is window level (WL)?
The midpoint of the range of pixel values — controls image brightness.
231
What happens when window level is increased?
The image becomes darker.
232
What happens when window level is decreased?
The image becomes lighter.
233
What two main qualities define a diagnostic image?
Proper visibility of detail and accurate geometric representation.
234
What is the best way to maintain consistent image quality?
Follow exposure indicator guidelines, use ALARA principles, and verify histogram accuracy.
235
What factor most directly affects patient dose?
mAs — it controls the number of photons striking the patient.
236
What happens if you “fix” exposure errors with post-processing instead of technique?
The patient may be overexposed without visible evidence (dose creep).
237
What is the best way to avoid dose creep in digital imaging?
Routinely monitor exposure indicator (EI) values and adjust technique as needed.
238
Quality Assurance (QA)
A complete program in the radiology department that ensures quality in all aspects — including customer service, image interpretation, diagnostic accuracy, and report distribution.
239
Quality Control (QC)
A program that focuses specifically on the safe and reliable operation of imaging equipment.
240
Who requires quality control programs?
The Joint Commission.
241
Who is responsible for implementing and maintaining QC programs?
Radiologists, radiology managers, radiation physicists, and QC technologists.
242
What is beam restriction?
Limiting the size of the x-ray beam to reduce patient exposure and scatter radiation production.
243
What is the purpose of light field–to–radiation field alignment?
To ensure that the illuminated field corresponds accurately with the actual x-ray exposure area.
244
How accurate must the collimator light field be to the radiation field?
Within 2% of the SID.
245
What tests are used to verify collimator and beam alignment?
The penny test or collimator and beam alignment test tool template.
246
What is the maximum allowable central ray misalignment?
The CR must not be misaligned by more than 1 degree.
247
What is Continuous Quality Improvement (CQI) in imaging?
An ongoing program that monitors and reviews non-diagnostic images sent to PACS for quality improvement.
248
What happens when poor-quality images are identified?
The images are reviewed by a radiologist and reported to the lead technologist or PACS administrator.
249
What steps should be taken if a poor image is due to equipment malfunction?
Perform the appropriate QC test and follow the service protocol.
250
What if poor image quality is due to technologist error?
The technologist should receive additional training or counseling.
251
Why is maintenance of imaging systems important?
To ensure consistent image quality and safe, reliable equipment performance.
252
Who is responsible for recognizing the need for maintenance and evaluation?
The radiologic technologist.
253
What are examples of digital imaging system maintenance tasks?
Detector calibration and plate reader calibration.
254
What are daily QC tasks?
Inspect system operation and verify status, Create sensitometry strip (for film systems), Erase uncertain cassettes before use, Check images for dust, scratches, or friction marks, Clean cassettes and inspect hinges/latches, Verify network and printer operation.
255
What are weekly QC tasks?
Clean and inspect receptors, Clean air intakes on IP readers, Clean display screens, keyboards, and mice.
256
What are monthly QC tasks?
Erase all plates in inventory, Acquire QC phantom image and measure performance, Verify calibration of QC workstation using AAPM TG-18 test pattern, Perform reject analysis with reasons (e.g., positioning or marker errors), Clean image plates and identify artifacts.
257
What are quarterly QC tasks?
Implement a full cleaning program for cassettes and IPs, Perform phantom analysis for resolution, contrast/noise, laser jitter, and EI accuracy, Review image retake rates and causes, Review exposure indicator trends, Analyze service history and exposure trends.
258
What are annual QC tests performed by physicists?
Evaluate image quality and processing algorithms, Perform acceptance testing and reestablish baselines, Review technologist QC reports and repeat rates, Test image plate dark noise and uniformity, Verify exposure indicator calibration, Evaluate system linearity, laser beam function, and erasure thoroughness, Assess noise, contrast resolution, and spatial accuracy.
259
When should QC testing also be performed?
After hardware or software upgrades or major repairs.
260
What are common QC tests for imaging receptors (CR/DR)?
Erasure thoroughness, Plate uniformity, Spatial resolution.
261
What tool is used to evaluate spatial resolution?
A line-pair resolution test tool.
262
How is erasure thoroughness evaluated in CR?
Expose the IP, then re-expose to check for residual (ghost) images.
263
How is erasure thoroughness evaluated in DR?
Check for image lag from residual charges after exposure.
264
How should IRs be maintained to prevent artifacts?
Visually inspect and clean them regularly according to manufacturer guidelines.
265
What is spatial resolution in display systems?
The ability of a digital display to reproduce fine detail with high accuracy.
266
What is this?
Pattern for display resolution evaluation
267
What is this?
Pattern for resolution uniformity evaluation
268
What does the DICOM Grayscale Standard Display Function (GSDF) ensure?
Consistent grayscale display performance across all monitors.
269
How much variation is acceptable in GSDF performance?
Should not vary by more than 10%.
270
What geometric monitor distortions should be checked for?
Concavity and convexity.
271
What is veiling glare?
Unwanted light that reduces contrast and increases display noise.
272
What is luminance?
The amount of light emitted from a monitor surface, measured in candelas per square meter (cd/m²).
273
What device measures luminance?
A luminance meter or photometer.
274
What is the acceptable luminance range for primary diagnostic monitors?
300–500 cd/m².
275
What is luminance response?
The relationship between displayed luminance and input signal values.
276
How is luminance response evaluated?
Using a test pattern with low-contrast targets visible in all 16 regions.
277
How far from the monitor should this pattern be evaluated?
Approximately 30 cm away.
278
What is a common sign of failure in the luminance response test?
Inability to see one or two dark regions in the pattern.
279
What shielding accessories must be tested annually?
Lead aprons, gloves, and gonadal shields.
280
How should protective apparel be tested?
By radiographing or fluoroscoping them to check for defects.
281
What defects require replacement of protective apparel?
Cracks, tears, or holes in the lead lining.
282
What are common causes of lead apron damage?
Folding, improper storage, or excessive wear.
283
If DI = +3, how should exposure be adjusted?
Decrease mAs by ½ or reduce kVp by 15%.
284
If DI = -3, how should exposure be adjusted?
Double the mAs or increase kVp by 15%.
285
Example — Original: 70 kVp, 25 mAs, DI = +3. What’s optimal?
60 kVp, 25 mAs or 70 kVp, 12.5 mAs.
286
Example — Original: 90 kVp, 50 mAs, DI = -3. What’s optimal?
104 kVp, 50 mAs or 90 kVp, 100 mAs.
287
What is a gross exposure error?
Severe underexposure or overexposure that causes loss of image contrast.
288
What is saturation?
Overexposure that results in burned-out areas that cannot be corrected.
289
What tests ensure monitor quality?
AAPM TG 18 or SMPTE test patterns.
290
What is the allowable grayscale variation?
Should not vary more than 10%.
291
How is luminance measured?
Using a luminance meter or photometer (cd/m²).
292
How often should aprons, gloves, and shields be checked?
Annually for cracks or defects.
RAD 142
flashcards
Decks in class (6)
# Cards
