Download presentation
Published bySarah Kelley Modified over 9 years ago
1
Components of Image Quality & Radiographic Artifacts
Radiologic Technology A SPRING 2012
2
X-ray Exposure Factors
Radiographic Density & Contrast Components of Image Quality Radiographic Artifacts
3
Review Primary radiation exits the tube
Interacts with various densities in the body Photons may be absorbed Scattered Passed through without any interference to the cassette or image receptor (IR)
5
How well we can see something on the image
6
Image detail is affected by: Photographic properties and Geometric properties
7
Photographic Properties
Contrast Density
8
X-ray Exposure Factors
TECHNIQUE SELECTION: Radiographer selects the Kilovoltage peak (kVp) Milliamperage (mA) & time (s) Milliamperage x time = mAs (milliamperage multiplied by a set time measured in seconds)
9
Kilovoltage Peak kVp One kilovolt = 1000 volts
The amount of voltage selected for the x-ray tube. Range 30 to 150 kVp kVp controls contrast
10
Milliamperage One milliampere (mA) = one thousandth of an ampere.
The amount of current supplied to the x-ray tube How many x-rays will be produced Range 10 to 1200 mA
11
Time In seconds How long x-rays will be produced 0.001 to 6 seconds
12
Milliampere Seconds Technologists think in terms of mAs
Calculated by mA x seconds Ex: 100mA X 0.2s = 20 mAs How many x-rays will be produced and for how long. Modern x-ray machines only allow control of mAs controls density
13
Factors Affecting Density
Primary control factor mA Time (seconds) Influencing factors kVp Grids Beam restriction Body structures (size of pt, pathology Processing SID & OID Film Screen combinations
14
Primary Controlling Factor of Density
mAs mA = AMOUNT of electrons sent across the tube combined with TIME (S) = mAs mAs controls DENSITY on radiograph primary function of mAs is DENSITY
15
Imagine this… If the mA station is changed from 200 to 400 mA, twice as many electrons will flow from the cathode to the anode. From 10 mA to 1000 mA = 100 x more mA controls how many electrons are coming at the target mAs is a combination of how many and for how long (seconds)
16
10 mA 1000 mA
18
Changing Mas – Changes Density + 25 % + 50 % mas
19
Influencing Factor on Density: kVp
20
15% kVp = doubling of exposure to the film
kVp more energy = more photons passing though tissue & striking the image 15% kVp = doubling of exposure to the film 15% kVp = halving of exposure to the film 15% rule will also change the contrast of the image because kV is the primary method of changing image contrast. Remember : 15% change ( ) KVP has the same effect as doubling or ½ the MAS on density 15% rule: 15% kVp = doubling of exposure to the film 15% kVp = halving of exposure to the film 15% rule will also change the contrast of the image because kV is the primary method of changing image contrast. Remember : 15% change ( ) KVP has the same effect as doubling or ½ the MAS on density
21
Change in kVp kVp controls the energy level of the electrons and subsequently the energy of the x-ray photons. A change from 72 kVp will produce x-rays with a lower energy than at 82 kVp Difference between a ball traveling 72 mph and 82 mph (how much energy did it take to throw the ball at the rates?)
22
+ 15% kvp - 15% kvp This will also influence the density on the image
Increasing kVp = increase energy reaching the IR
23
Radiolucent vs. Radiopaque
Radiolucent materials allow x-ray photons to pass through easily (soft tissue). Radiopaque materials are not easily penetrated by x-rays (bones)
24
Creating the Image Transmission Scatter Absorption no interaction
Responsible for dark areas Scatter (grays) – produces no diagnostic info Absorption (photoelectric effect) Responsible for light areas
25
Images DENSITY = THE AMOUNT OF BLACKENING “DARKNESS” ON THE RADIOGRAPH (mAs) CONTRAST – THE DIFFERENCES BETWEEN THE BLACKS TO THE WHITES (kVp)
26
Why you see what you see…
The films or images have different levels of density – different shades of gray X-rays show different features of the body in various shades of gray. The gray is darkest in those areas that do not absorb X-rays well – and allow it to pass through The images are lighter in dense areas (like bones) that absorb more of the X-rays.
27
Image Production Primary Radiation – The beam of photons, B4 it interacts with the pt’s body. Remnant Radiation – The resulting beam that is able to exit from the patient. Scatter Radiation – Radiation that interacts with matter & only continues in a different direction – not useful for image production. Attenuation – Primary radiation that is changed (partially absorbed) as it travels through the pt. Primary Radiation – The beam of photons, B4 it interacts with the pt’s body. Remnant Radiation – The resulting beam that is able to exit from the patient. Scatter Radiation – Radiation that interacts with matter & only continues in a different direction – not useful for image production. Attenuation – Primary radiation that is changed (partially absorbed) as it travels through the pt.
28
Patient Body Size and Pathology
29
3 Different Body Habitus Hypersthenic Sthenic Hyposthenic
Dr. Charman, Eric Guzman, Adam Guzman Thank you to the 3 men in my life ! DCharman
30
PATHOLOGY Pleural Effusion Excessive fluid in lung More dense than air
31
Pneumonia
32
Pneumothorax The right lung is almost completely collapsed;
vascular shadows can not be seen in this area (arrow). Lung collapses No tissue in space Easy to penetrate with x-ray photons Pneumothorax
33
Lung Cancer
34
LUNG CANCER
35
Density and Images
36
Goal: Producing optimal radiographs DENSITY
Could be caused by kVP or mAs. Too dark Too light
38
Controlling Factor of Contrast
39
Controlling Factor of Contrast
Kilovolts to anode side – kVp Kilovolts controls how fast the electrons are sent across the tube kVp – controls CONTRAST on images
40
Producing optimal radiographs Contrast Scale
Long scale short scale
42
Scale of Contrast? Which one is “better” How does the kVp affect these images?
45
Beam Restriction and Grids
46
Scatter Creates fog Lowers contrast (more grays) Increases as
kV increases Field size increases Thickness of part increases
47
Effects of collimation (beam restriction) on scatter
48
Collimate to area of interest -reduces scatter and radiation dose to the patient
49
Grids A device with lead strips that is placed between the patient and the cassette Used on larger body parts to reduce the number of scattering photons from reaching the image
50
Basic Grid Construction
Radiopaque lead strips Separated by radiolucent interspace material - Typically aluminum Allow primary radiation to reach the image receptor (IR) Absorb most scattered radiation Primary disadvantage of grid use Grid lines on film
51
GRIDS
52
Grid is placed between patient (behind table or upright bucky) & cassette
53
Grids absorb scatter – prevents it from reaching the image
STOPS SCATTER
55
Contrast changes with the use of a grid
Less scatter radiation – shorter scale = “better contrast” With Grid No Grid
56
GRIDS CAN LEAVE LINES ON THE IMAGE
57
GEOMETRIC Properties Recorded Detail DISTORTION Size distortion
Magnification Shape distortion Elongation Foreshortening
58
RECORDED DETAIL
59
The degree of sharpness in an object’s borders and structural details.
RECORDED DETAIL The degree of sharpness in an object’s borders and structural details. How “clear” the object looks on the radiograph
60
Recorded Detail The degree of sharpness in an object’s borders and structural details. Other names: -sharpness of detail -definition -resolution -degree of noise
61
RESOLUTION TEST TOOLS LINE PAIRS/ MM Depicts how well you can see the differences in structures More lines=more detail
63
Factors that affect Recorded Detail
Geometric unsharpness OID SID SIZE SHAPE Motion unsharpness (blurring) Intensifying Screens Film Speed / Composition Film – Screen contact Kvp & Mas (density / visibility)
65
MOTION AKA Blurring
66
Motion Can be voluntary or involuntary
Best controlled by short exposure times Use of careful instructions to the pt. Suspension of pt. respiration Immobilization devices
68
Decrease Motion Unsharpness
Instruct patient not to move or breath Use Immobilization devices Use Short exposure times Lock equipment in place
69
Blurring of image due to patient movement during exposure.
71
Object Unsharpness Main problem is trying to image a 3-D object on a 2-D film. Human body is not straight edges and sharp angles. We must compensate for object unsharpness with factors we can control: focal spot size, SID & OID
72
SID Source to Image Distance
The greater the source X-ray tube) to image (cassette) distance, the greater the image sharpness. Standard distance = 40 in. most exams Exception = Chest radiography 72 in.
73
The SID will influence magnification
The SID will influence magnification. The farther away – the less magnified ↑SID ↓ MAGNIFICATION The position of the tube (SID) to IR Will influence how the structures appear on the image The farther away – the less magnified ↑SID ↓ MAGNIFICATION
74
SID Shine a flashlight on a 3-D object, shadow borders will appear “fuzzy” -On a radiograph called Penumbra Penumbra (fuzziness) obscures true border – umbra Farther the flashlight from object = sharper borders. Same with radiography.
76
OID Object to Image Distance
The closer the object to the film, the sharper the detail. OID , penumbra , sharpness OID , penumbra , sharpness Structures located deep in the body, radiographer must know how to position to get the object closest to the film. The closer the object to the film, the sharper the detail. OID , penumbra , sharpness OID , penumbra , sharpness Structures located deep in the body, radiographer must know how to position to get the object closest to the film. *See page 74 in your book
77
The position of the structure in the body will influence how magnified it will be seen on the image
The farther away – the more magnified
79
Distortion Misrepresentation of the true size or shape of an object
MAGNIFICATION size distortion TRUE DISTORTION shape distortion
80
MAGNIFICATION TUBE CLOSE TO THE PART (SID)
PART FAR FROM THE CASSETTE (OID)
81
Demonstrates increased OID which increases magnification
82
http://www. coursewareobjects. com/objects/mroimaging_v1/mod04i/0416a
83
Size Distortion & OID If source is kept constant, OID will affect magnification As OID , magnification The farther the object is from the film, the more magnification
84
Which side is more magnified?
85
In terms of recorded detail and magnification the best image is produced with a
small OID & large SID
86
Minimal magnification small OID
Magnification - large OID
87
Size Distortion & SID Major influences: SID & OID
As SID , magnification Standardized SID’s allow radiologist to assume certain amt. of magnification factors are present Must note deviations from standard SID Major influences: SID & OID As SID , magnification Standardized SID’s allow radiologist to assume certain amt. of magnification factors are present Must note deviations from standard SID
91
40” SID VS 72” SID
93
SHAPE DISTORTION Elongation and Foreshortening
94
Shape Distortion Misrepresentation of the shape of an object
Controlled by alignment of the beam, part (object), & image receptor Influences: Central ray angulation & body part rotation
95
A = good B & C = shape distortion (elongation of part)
96
D & E = shape distortion (foreshortening of part)
97
Image Distortion When the part to be imaged – does not lay parallel with the IR (cassette) If the Central Ray is not perpendicular to the part CR should be at right angle with the cassette
98
Central Ray Angulation
Body parts are not always 90 degrees from one another Central ray angulation is used to demonstrate certain details that can be hidden by superimposed body parts. Body part rotation or obliquing the body can also help visualize superimposed anatomy.
99
Central Ray Radiation beam diverges from the tube in a pyramid shape.
Photons in the center travel along a straight line – central ray Photons along the beam’s periphery travel at an angle When central ray in angled, image shape is distorted.
103
Elongation Foreshortened Normal
105
Distortion (x-ray beam not centered over object & film)
Distortion (object & film not parallel)
106
Distortion of multiple objects in same image (right) due to x-ray beam not being centered over objects.
107
Focal Spot Size Smaller x-ray beam width will produce a sharper image.
Fine detail = small focal spot (i.e. small bones) General radiography uses large focal spot Beam from penlight size flashlight vs. flood light beam
108
ANODE ANODE
109
THE SMALLER THE BEAM TOWARDS THE PATIENT - THE BETTER THE DETAIL OF THE IMAGE PRODUCED
110
FOCAL SPOT ANGLE SMALLER ANGLE – SMALLER BEAM AT PATIENT
111
ARTIFACTS: AN UNWANTED DENSITY ON THE FILM
112
Artifacts - Types Processing Artifacts Exposure Artifacts Handling & Storage Artifacts
113
Processing Artifacts Emulsion pickoff Chemical fog Guide-shoe marks
Water marks Chemical spots Guide-shoe & roller scratches
114
Developer Spots
115
Water spot
116
Discolored film due to hypo (fixer) retention.
Chemicals not washed off – over time will turn film brown
117
Scratch marks from rollers in automatic processor.
118
Exposure Artifacts Motion Improper patient position
Wrong screen-film match Poor film/screen contact Double exposure Warped cassette Improper grid position
119
Artifact
121
Blurred image due to patient motion
122
PATIENT ARTIFACT - JEWERLY
123
Handling & Storage Artifacts
Light fog Radiation fog Static Kink marks Scratches Dirty cassettes
124
Crimping /cresent mark
125
2 exposures made on top of each other –
Double Exposure 2 exposures made on top of each other – from poor handling of cassettes
127
Static electricity
128
Dirt on screen mimicking a foreign object.
129
Scratch marks from improper handling.
130
Light fog
131
Kink mark or nail pressure mark
132
cast
133
POOR SCREEN CONTACT
134
Patient motion
135
motion
136
Double exposure Child
137
Poor screen contact
138
Double exposure
139
?
140
? Is it motion or double exposure
142
Pt clothing
143
Hip replacement
144
2 chest tubes in the patient
145
Patient swallowed batteries
What size are they?
147
PATHOLOGY NOT ARTIFACT
148
Name & cause of this?
149
scratches
150
Digital image Mis- Registration error
151
Roller marks from film stuck – then pulled from processor
152
Hardware In cervical spine
153
Dust in imaging plate can cause white marks on image
Both in film/screen and computed radiography
154
E E G MONITOR
155
What do you See? 2 exposures
158
Evaluating Images What do you think?
159
See anything wrong with this image?
160
Contrast? What influences this? (kVp in f/s)
161
Collimation – reducing the size of beam helps to improve the image, and reduce the dose to the patient
162
?
Similar presentations
© 2025 SlidePlayer.com. Inc.
All rights reserved.