Digital Image Artifacts Flashcards
1
Q
Define artifacts.
A
- Unintended optical density on an image
- False visual feature that stimulate anatomy or obscure tissues.
- Excludes scatter and fog
- Degrades image (may necessitate repeat exam)
2
Q
What are some category of artifacts?
A
Hardware, software, object
3
Q
What are hardware artifacts?
A
Image receptor artifacts (imaging plate artifacts), plate reader artifacts, printer artifacts
4
Q
What software artifacts?
A
Image processing artifacts, histogram errors, rescaling, image compression
5
Q
What are object artifacts?
A
Collimating, back scatter, patient positioning
6
Q
What happens when the cassette is exposed with the back of a cassette toward the source?
A
Result: image with a white grid-type pattern and white areas that correspond hinges.
7
Q
What kind of digital artifacts can happen with improper collimating (too much or too little)?
A
- Exposure field recognition errors
- Histogram analysis errors (software cannot find VOI; result: rescaling error- poor density, contrast on image).
8
Q
What happens with no collimation?
A
- Too much exposure in histogram
- Exposure indicator number reflects plate overexposure (but maybe it wasn’t overexposed)
9
Q
What are exposure field recognition errors?
A
Preprocessing software cannot fund exposure field edge.
10
Q
What is the result of exposure field recognition errors?
A
Scatter, off focus, unattenuated radiation included in histogram.
11
Q
What does exposure field recognition errors lead to?
A
- light dark, or low contrast images.
- Incorrect exposure indicator number
- histogram and rescaling errors (if software cannot find borders, all image data is included. Histogram applied to all image data, not just VOI.)
12
Q
What happens when there are rescaling errors?
A
- When rescaled, software cannot properly adjust image to reference histogram.
- LUT cannot properly apply contrast.
- Image may look dark or light, have little contrast latitude (cannot window/level image.)
13
Q
How to collimate?
A
- Collimation borders parallel to IR border (4 distinct margins are best)
- Even number of collimated fields
- One image per plate
- Center part to IR
14
Q
What are IR artifacts?
A
- Dust, dirt, scratches (from imaging plate handling, plate in and out of cassette of CR reader).
- Dirt on optics (lenses, mirrors, light guide) - appear as horizontal white lines (along path of plate travel), service engineers must clean.
15
Q
What are more artifacts that can be found?
A
- Stains from cleaning chemical (leakage into cassette, wrong chemical used on IP - anhydrous alcohol only)
- Pixel malfunctions (sampling errors, bad pixels on flat panel detectors).
- Ghost images (incomplete erasure, incorrect erasure settings)
16
Q
What are plate reader artifacts?
A
- Extraneous lines/ patterns on image
- Due to plate reader electronics malfunctioning
- Appears on multiple images- not same plate
17
Q
What are printer artifacts?
A
- Dirt in laser printer causes fine white lines
- Service engineers must clean, calibrate.
- Easy to differentiate from plate reading artifacts.
18
Q
What are software artifacts?
A
- Dead pixels (software interpolates data to fill in - correction algorithms that assign values to dead pixels upon values of adjacent pixels).
- flat field correction (software corrects irregular patterns in image, uniform response to uniform x-ray beam).
- Incorrect image compression (compresses for transmission, some post processing application need raw data).
19
Q
Is quantum mottle considered a software artifact?
A
Yes
20
Q
What causes quantum mottle?
A
Not enough radiation exposure to the detector.
21
Q
How do we fix quantum mottle?
A
Usually more mAs.
22
Q
What are grid artifacts?
A
When grid lines are parallel to scanning laser in CR reader, a moire effect can occur.
23
Q
What eliminates grid artifacts?
A
Oscillating grids
24
Q
How many lines should high frequency grids have?
A
103 lines/in
25
What is ideal grid position?
Grid lines are perpendicular to translation of laser.
26
What are object artifacts?
- Exam menu selection (wrong menu = wrong histogram).
| - Collimation
27
What are operator errors?
- Backward cassette (grid pattern of cassette support seen over image).
- No collimation (unattended radiation strikes IR, alters histogram)
- Wrong size IR ( image appears small).
28
What are operator errors?
- Insufficient collimation results in unattenuated radiation striking the image plate. The resulting histogram is changed so that it is outside the normal exposure indicator range for the body part selected.
- Contrast reduction due to overexposure.
29
What are some histogram errors not caused by a radiographer?
- Unexpected are of increased/decreased attenuation in body.
- Artificial joint, Barium in bowel, uneven lead shield border.
- Area of low lucency included in histogram. Oops! Software thinks image underexposed.
- Compensates with rescaling/LUT application: image looks dark.
30
What is partitioning?
- Multiple images on 1 plate
- Symmetry is key
- 4 sided collimation
- Symmetric part placement
- Appropriate technique
- Software averages all image data
31
As with film/screen systems, artifacts can what?
Degrade images in digital systems.
32
What are artifacts?
Are any undesirable densities on the processed image other than those caused by scatter radiation or fog.
33
What are the 4 common types of artifacts in addition to operator errors that may cause artifacts?
Image plate artifacts, plate reader artifacts, image processing artifacts, and printer artifacts.
34
As the imaging plate ages it becomes prone to what?
Cracks from the action of removing and replacing the imaging plate within the reader.
35
Cracks in the imaging plate appear as areas of what?
Radiolucency on the image.
36
The imaging plate must be replaced when?
When cracks occur in clinically useful areas.
37
Adhesive tape used to secure lead markers to a surface can leave what?
Residue behind
38
If static exists because of low humidity, hair can do what this creating what?
Hair can cling to the imaging plate, creating another type of image plate artifact.
39
Backscatter is created by what and can cause what?
It is caused by x-ray photons transmitted through the back of the cassette and can cause dark line artifacts.
40
Areas of the lead coating on the cassette that are worn or cracked allow what?
Scatter to image these weak areas.
41
Proper collimation and regular cassette inspection help to eliminate what?
That areas of the lead coating on the cassette that are worn or cracked allow scatter to image these weak areas.
42
Processing artifacts can occur for many different reasons, such as what?
Choosing the incorrect processing parameter for a particular part or incorrect sampling of the image file.
43
Why is it very important to set appropriate technical factors and choose the correct body part so that what?
The software algorithms will produce the desired image.
44
Poor technique such as what can cause these algorithms to misrepresent the image?
Collimation, Grid selection, mAs, kVp, and positioning
45
The technologist must remain aware of what, because if not it can influence change in the final processed image?
All factors
46
The intermittent appearance of extraneous line patterns can be caused by?
Problems in the plate reader’s electronics.
47
What may have to be replaced to remedy this problem?
Reader electronics
48
White lines that are parallel to the direction of the plate travel are caused by what??
Dirt, dust, or scratches on the light guide.
49
What is a rare but possible artifact that can occur?
When multiple imaging plates are loaded into a single cassette.
50
In an instance where multiple imaging plates are loaded into a single cassette, what will happen?
Usually only one of the plates will be extracted, which leaves the other plate to be exposed multiple times.
51
What is this similar to?
A conventional film/screen double-exposed cassette.
52
Insufficient erasure after an overexposure may result in what?
Residual image information being left in the imaging plate before the next exposure.
53
Fine white lines may appear On The image because of?
Debris on the mirror in the laser printer.
54
Who will have to clean the printer?
Service personnel
55
Insufficient collimation can result in an improper what?
Calculation of the exposure indicator.
56
Improper calculation of the exposure indicator may result in what?
A misrepresentation of the displayed image.
57
If the cassette is exposed with the back of the cassette toward the source, the result will be?
Artifacts from any hinges or other hardware present on the back of the cassettes.
58
Care should be taken to expose only what?
The tube side of the cassette.
59
Underexpose produces __________ and overexposure reduces _________.
Quantum mottle
| Contrast
60
The proper selection of technical factors is critical for both ?
Patient dose image quality and to ensure the appropriate production of light from the imaging plate.
61
In assessing the patient prior to a radiographic procedure, the radiographer must be aware of any what and why?
* removable prosthetic or orthopedic devices
* casts
* parts of clothing or items in the hair
It may impede full visualization of the anatomy of interest.
62
Carelessness during the the procedure can also result in what?
Parts of the equipment, such as electric cables or intravenous lines, getting in the way of the exposure and causing artifacts in the radiograph.
63
When patients must be held, carelessness result in the radiographer doing what?
In the radiographer’s own hands or the hands of a parent being superimposed over the anatomy of interest.
64
An artifact may be defined in a dictionary as what?
“ a product of artificial character due to an extraneous agency.”
65
“ a product of artificial character due to an extraneous agency.” Means what?
That is, it is not natural, and it is caused or created by something outside itself, such as a human.
66
On a radiograph, an artifact is an image which does not what? And how is it created?
Does not represent the real anatomy of the patient.
Is either created by the process of producing the radiograph or caused by a man-made object.
67
Understanding the geometry of the x-ray beam helps what?
To eliminate and diagnose the specific causes of many artifacts.
68
What happens when an object is placed farther and farther from the film cassette (or nearer to the X-ray tube)?
It’s projected “shadow” on the radiograph will become more magnified in size and more blurry at the edges.
69
Sharp, clear artifact which appears to have what?
A realistic size was probably caused by an object bar or on or in cassette.
70
A slightly blurred artifact was most likely caused by what?
An object on or near the surface of the patient.
71
A grossly magnified and blurred artifact was most likely caused by what?
An object suspended over the patient or attached to the X-ray tube itself.
72
Prior to beginning a radiographic procedure, the technologist also makes an estimation of the probability that the patient motion might occur during the exposure, examples are?
Small children, retarded patients, inebriated patients, trauma patients suffering much pain and senile patients.
73
In such cases when the probability of motion is high what must be anticipated and used?
Extra immobilization methods and modified techniques must be anticipated and used on the 1st attempts at producing quality radiographs.
74
What types of items may inadvertently left on a patient’s person during a radiographic procedure?
* necklaces, rings, jewelry
* hairpins, barrettes,wigs, hair ornaments
* keys, cigarettes, lighters and other items left in pockets
* glasses, hearing aids, dentures, false eyes, prosthetics or cosmetic devices
* snaps, buttons, thick seams, and ornaments on clothing
* blood-soaked Hair or braided hair
* folded, matter or blood soaked clothing, gowns, sheets, blankets or gauze
75
Most of the items left on the patient are ______ and may show up “_____” or lighter than what?
Radiopaque
White
Soft tissue on the image
76
Proper assessment includes what?
Talking to the patient and asking if he or she has any hairpins, protheseses, false eyes, removable orthodontic devices in addition to careful observation.
77
What must be set on top of shoulders for a chest radiographs? With tape and out of lung field
Braided hair, pony tails, or pig tails
78
What must be moved aside whenever possible?
Intravenous lines, catheters, electrical leads, or other equipment attached to patient
79
If they cannot be completely removed from the projected image area, an attempt should be made to at least what?
Minimize their superimposition over the anatomy if interest.
80
Name an example where one can move wires out of the way?
Never leave coils of electrical leads over the lung field when they might be unwound and pulled to the side so that only a single wire to each lead is in the anatomy.
81
What must you also be aware of?
Folds in sheets and gowns as the patient is placed on the radiographic table.
82
What do most radiographer assume won’t show up in the radiograph?
Folds or seams in clothing, gowns, sheets or pillows.
83
When should extra care be taken care of?
Lower kilovoltage techniques, must smooth out sheets under the patient, remove undershirts, take off packed gauze etc, or these cloth indeed show up
84
What is essential for patients for fluoroscopic procedures?
Complete preparation
85
Generally patients should be kept NPO for at least how many hours prior to fluoroscopic procedure?
8
86
What must be effectively performed for colon studies?
Cleansing enemas
87
What does food cause on a radiograph?
Causes dark artifacts breaking up the barium bolus and rendering any useful diagnosis hopeless.
88
After the patient is successfully prepared what must happen?
Such studies must be repeated.
89
What are the many kinds of foreign bodies?
Bullet fragments
Silvers
Swallowed objects or objects inserted into the skin, nose, ears, penis, vagina, or rectum that might be considered as “artifacts”, particularly if they superimpose anatomy of interest.
90
More often, however, foreign bodies are the what?
“Anatomy” or pathology of interest and will not be further discussed here.
91
What are some radiopaque items that can’t be removed?
Casts
92
Radiopaque items such as cast may require what and in order to do what?
Technique adjustment or positioning modifications in order to minimize the deleterious effect of the artifacts.
93
For proper demonstrations of anatomy superimposed by casts or splints radiographic techniques must certainly be what?
Adjusted upward
94
To determine the extent of this increase, one must take into consideration what?
Composition of the materials used, their thickness and configuration, and whether they are wet or dry.
95
Radiographs taken after limb of the body has been set and casted are called?
Post-reduction radiographs
96
Full plaster casts require what?
minimum doubling of overall exposure factors from the usual technique for that body part
97
How can doubling be achieved?
Either by doubling the mAs or by increasing the kVp by 15%.
98
Full plaster casts which are still wet, having just being applied require what?
3 times the overall technique.
99
Unusually thick plaster may be applied around where?
The femur and the torso
100
A full cast of unusually thick plaster which is dry will require what?
A tripling of the usual technique.
101
A plaster cast of this thickness which is still wet can require what?
As much as 4 times the original technique.
102
Often, “half casts” are secured to a limb by what?
By wrapping a partial cast with an Ace bandage.
103
Half casts with a partial cast with Ace bandage, use what?
50% increase in technique.
104
Half again as much as _____, or approximately ____ percent more KVp.
Mas
| 8
105
Remember to employ the increase only when what?
The projection of the part of interest passes through the cast material.
106
An example maybe on a lateral view of a forearm in a half cast the bones may not be ?
Covered by the cast and a normal technique should be used.
107
What has become popular as a casting medium?
Fiberglass mesh
108
Fiberglass is very what and allows for what?
Radiolucent, allowing the x-ray beam to pass through it virtually unaffected.
109
Normal techniques may b used in most cases when what?
Pure fiberglass is used.
110
Fiberglass is often mixed in roughly equal to what?
Proportions with plaster
111
What is a general rule of thumb on technique for casts made of mixed fiberglass and plaster?
Increase mAs by 50%, or kVp by 8%.
112
Projections must sometimes be made through what?
Splints if wood or aluminum or through plastic devices.
113
These materials (wood, aluminum, plastic) may require from ___ to ____ percent _______ in overall technique.
35 to 65
| Increases
114
Whether the splint is applied to one side or to both sides of the limb the radiograph we must do what?
Assess the total thickness of material to be transverse by the x-ray beam.
115
mAs should be increased by what for 1/2 inch of wood? 1 inch should be increased by?
35% (1/3) for 1/2 inch
| 50% (1/2) for 1 inch
116
As a rule of thumb increase mAs by how much for wood or aluminum splints?
50%
117
It is not possible to completely eliminate the artifacts caused by casts or splints, but a proper what will do what?
A proper increase in technique will darken the image density to enhance the visibility of the anatomy through the obstructing material.
118
The radiographer must always be aware of any type of what?
Equipment which lies between the X-ray tube and the film.
119
What are some examples of anything that falls within the collimated light field?
Whether it’s near the X-ray tube, over the patient, in the patient or behind the patient.
120
Anything which falls within the collimated light field will be images as what?
An artifact and may obscure essential diagnostic information.
121
What is a common example of troublesome radiographic equipment?
Electrical cables which connect to the X-ray tube, especially on older machines.
122
Sometimes these cables are not what?
Secured to the ceiling crane or tube armature.
123
With cables it is possible when turning the tube and collimator into certain positions to get?
To get the cables in front of the tube.
124
Troublesome patient care equipment includes?
Air hoses and attachments for ventilators and other respiratory care equipment, intravenous lines and electrical leads for electrocardiographs.
125
The amount of magnification and blur indicate what and why is this helpful?
Indicate the relative distance from the film which is helpful in diagnosing the cause of the artifact.
126
Ventilation hose and plastic attachments are subtle artifacts what is the first reason why?
Because they were hanging in the air over the patient and at that distance were blurred and magnified.
127
What is the second reason the ventilation hose and plastic attachments are subtle artifacts?
They are made of thin plastic which has low x-ray absorption characteristics.
128
The IV line has ____ absorption characteristics but was caught between the patient and the cassette so that it is?
LOW
| Not magnified and shows sharp edges.
129
Movement of any part of the patient, the cassette or the X-ray tube while the exposures taking place will result in what?
Blurring of the details on the rad image.
130
Blur destroys what?
The recognizability of image details.
131
If blue is extreme it can also destroy what?
Image contrast, reducing the visibility of details.
132
Patient motion is often categorized physiologically into two types:
Voluntary or involuntary
133
Voluntary is defined as what?
Conscious motion involving voluntary (striated) muscles.
134
Voluntary motion does not necessarily mean what?
The patient intended to move.
135
Involuntary motion is defined as what?
Motion caused unconsciously by involuntary muscles such as the heart or the lower muscles of the esophagus once a swallowing action is initiated.
136
What are the 4 categories that motion is divided into?
1. Voluntary motion
2. Breathing motion
3. Peristaltic
4. Heart motion
137
Voluntary motion is characterized on an image by what?
General blurring of an entire limb, the head, or the entire torso.
138
During voluntary motion all parts of the anatomical area such as what will appear blurred and indistinct?
The bones, organs, and edges of the part itself will appear blurred and indistinct.
139
Frequently patient movement will result in what?
Double-images of contrasty anatomy such as the ribs and spine.
140
This type of motion (double-images of contrasty anatomy) is prevented mainly by what?
By clear and thorough patient instructions and by proper immobilization of the part.
141
Breathing motion on a chest or abdominal radiograph can be distinguished from what?
General motion
142
Blurred areas will include what ?
The lung markings, the diaphragm, and those organs such as kidneys and fundus of the stomach which lie immediately beneath the diaphragm.
143
Ribs may or may not be obviously blurred depending on what?
The depth of the respiration.
144
What is the key point?
The the bones of the shoulder and the spine will not be blurred, nor will the pelvis and organs of the lower abdomen.
145
Breathing motion is primarily prevented by what?
Clear and proper instructions to the patient
146
With difficult patients the only way of minimizing breathing motion is by what?
Using the shortest possible exposure times.
147
Peristaltic motion includes what?
Any localized movement of the gastrointestinal tract caused by normal digestion or by cramps.
148
Barium or gas will appear blurred where?
Esophagus, stomach, or a restricted portion of the small or large intestine
149
It I’ll be noted that other general areas of the GI tract and the bones of that region are what?
Not blurred
150
Peristaltic motion is reduced by what?
Proper preparation of the patient for GI procedures but is reliably controlled only by using the shortest feasible exposure times.
151
The heart is the only part in the body that causes what?
continuous involuntary motion
152
What is the only way to “freeze” this motion of the heart and produce a sharp radiograph?
By using extremely short exposure times.
153
What can be on any chest radiograph demonstrating obvious heart motion?
That it was taken with a long exposure time.
154
How can the exposure time be minimized ?
By using the highest mA station and high kilovoltages.
155
KVp for grid chests should be?
100-120 kVp
156
KVp for non grid chest?
80-100 kvp
157
Blurring of the image can also be caused by forgetting to do what?
Lock the X-ray tube securely in place prior to exposure.
158
Unlocked tubes will occasionally drift across the room due to what?
Spring tension, crooked ceiling cranes, and gravity.
159
Such movement from unlocked tubes will be what and result in what?
Normally linear and can result in linear streaking artifacts on the image as well as blur.
