Misc. Flashcards
(92 cards)
1
Q
mAs affects:
kVp affects:
OID affects:
SID affects:
A
RECEPTOR EXPOSURE ONLY
RECEPTOR EXPOSURE & CONTRAST
CONTRAST, SPATIAL RESOLUTION & DISTORTION
RECEPTOR EXPOSURE, SPATIAL RES & DISTORTION
2
Q
FOCAL SPOT SIZE AFFECTS:
GRIDS AFFECT:
TUBE FILTRATION AFFECTS:
BEAM RESTRICTION AFFECTS:
A
SPATIAL RESOLUTION ONLY
RECEPTOR EXP., & CONTRAST
RECEPTOR EXP., & CONTRAST
RECEPTOR EXP., & CONTRAST
3
Q
MOTION AFFECTS:
ANODE HEEL AFFECTS:
PATIENT FACTORS AFFECT:
ANGLE AFFECTS:
A
SPATIAL RESOLUTION ONLY
RECEPTOR EXPOSURE ONLY
RECEPTOR EXP, CONTRAST, SPATIAL RES & DISTORTION
SPATIAL RES & DISTORTION
4
Q
WHAT FACTORS AFFECT RECEPTOR EXPOSURE?
WHAT FACTORS AFFECT CONTRAST?
A
MAS, KVP, SID, GRIDS, FILTRATION, BEAM RESTRICTION, ANODE HEEL EFFECT, PATIENT FACTORS
KVP, OID, GRIDS, FILTRATION, BEAM RESTRICTION, PATIENT FACTORS
5
Q
WHAT AFFECTS SPACIAL RESOLUTION?
WHAT AFFECTS DISTORTION?
A
OID, SID, FOCAL SPOT SIZE, MOTION, PATIENT FACTORS & ANGLE
OID, SID, PATIENT FACTORS, ANGLE
6
Q
INCREASING MAS, ______ IR EXPOSURE
INCREASING MAS, ______ CONTRAST
INCREASING MAS, ______ SPATIAL RESOLUTION
INCREASING MAS, ______ DISTORTION
A
INCREASE
NO AFFECT
N/A
N/A
7
Q
INCREASING KVP, ______ IR EXPOSURE
INCREASING KVP, ______ CONTRAST
INCREASING KVP, ______ SPATIAL RESOLUTION
INCREASING KVP, ______ DISTORTION
A
INCREASE IR
DECREASE CONTRAST
N/A
N/A
8
Q
INCREASING OID, ______ IR EXPOSURE
INCREASING OID, ______ CONTRAST
INCREASING OID, ______ SPATIAL RESOLUTION
INCREASING OID, ______ DISTORTION
A
N/A
HIGHER CONTRAST
DECREASED SR
INCREASED DISTORTION
9
Q
INCREASING SID, ______ IR EXPOSURE
INCREASING SID, ______ CONTRAST
INCREASING SID, ______ SPATIAL RESOLUTION
INCREASING SID, ______ DISTORTION
A
DECREASED IR EXP.
N/A CONTRAST
INCREASED SR
DECREASED DISTORTION
10
Q
INCREASING FSS, ______ IR EXPOSURE
INCREASING FSS, ______ CONTRAST
INCREASING FSS, ______ SPATIAL RESOLUTION
INCREASING FSS, ______ DISTORTION
A
N/A
N/A
DECREASE SR (WANT SMALL FSS)
N/A
11
Q
INCREASING GRID RATION, ______ IR EXPOSURE
INCREASING GRID RATIO, ______ CONTRAST
INCREASING GRID RATIO, ______ SPATIAL RESOLUTION
INCREASING GRID RATIO, ______ DISTORTION
A
DECREASED IR EXP
HIGHER CONTRAST
N/A
N/A
12
Q
INCREASING FILTER, ______ IR EXPOSURE
INCREASING FILTER, ______ CONTRAST
INCREASING FILTER, ______ SPATIAL RESOLUTION
INCREASING FILTER, ______ DISTORTION
A
DECREASED IR EXP
LOWER CONTRAST
N/A
N/A
13
Q
INCREASING BEAM RESTICT, ______ IR EXPOSURE
INCREASING BEAM RESTRICT, ______ CONTRAST
INCREASING BEAM RESTRICT, ______ SPATIAL RESOLUTION
INCREASING BEAM RESTRICT, ______ DISTORTION
A
DECREASE IR EXP
HIGHER CONTRAST
N/A
N/A
14
Q
INCREASING MOTION, ______ IR EXPOSURE
INCREASING MOTION, ______ CONTRAST
INCREASING MOTION, ______ SPATIAL RESOLUTION
INCREASING MOTION, ______ DISTORTION
A
N/A
N/A
DECREASE S.R
N/A
15
Q
INCREASING PATIENT FACTORS, ______ IR EXPOSURE
INCREASING PT FACTORS, ______ CONTRAST
INCREASING PT FACTORS, ______ SPATIAL RESOLUTION
INCREASING PT FACTORS, ______ DISTORTION
A
DECREASE IR EXP
LOWER CONTRAST
DECREASE SR
INCREASE DISTORT
16
Q
INCREASING ANGLE, ______ IR EXPOSURE
INCREASING ANGLE, ______ CONTRAST
INCREASING ANGLE, ______ SPATIAL RESOLUTION
INCREASING ANGLE, ______ DISTORTION
A
N/A
N/A
N/A
INCREASE DISTORTION
17
Q
MAS DETERMINES ________
RELATIONSHIP BTWN MAS & IR EXPOSURE:
CONTROLLING FACTOR OF _________
A
QUANTIY
DIRECT, INCREASE 1 & OTHER INCREASES
IR EXPSOURE
18
Q
KVP DETERMINES _________
WHAT IS 15% RULE?
WHAT IS THE INVERSE SQUARE LAW?
A
QUALITY & SUBJECT CONTRAST
ONLY TAKES 15% KVP INCREASE TO DOUBLE IR EXPOSURE
as the SID increases the x rays spread out, less x rays per
area striking the image receptor
- as the SID doubles the receptor exposure would be reduced 4X
19
Q
WHAT IS SUBJECT CONTRAST?
AS SID DOUBLES, IR EXPOSURE ______
WHAT IS MOIRE EFFECT?
A
-(the difference in tissue density between adjacent anatomical parts that is affected by patient size and shape, factors that attenuate/reduce radiation intensity and the kVp/energy of the beam)
REDUCE BY 4X
FALSE LINEAR PATTERN
20
Q
WHAT ARE GRIDS USED FOR?
INCREASE GRID RATIO = _________ IR EXPOSURE
GCF:
NO GRID =
5:1 =
6:1 =
8:1 =
12:1 =
16:1 =
A
ABSORB SCATTER BEFORE REACHES IR
DECREASED
NO GRID = 1
5 = 2
6 = 3
8 = 4
12 = 5
16 = 6
21
Q
TYPES OF TUBE FILTRATION:
WHAT IS CONTRAST?
WHAT DETERMINES CONTRAST?
A
TUBE FILTER & COMPENSATING FILTER
contrast in digital images is the difference in brightness between adjacent areas on a display monitor
look-up tables determine the contrast in a digital image; using the mouse to change the window width will change the contrast
22
Q
INCREASED KVP = _______ SCATTER
WHAT IS SPATIAL RESOLUTION?
WHAT IS UNSHARPNESS?
A
INCREASED SCATTER = INCR. FOG
spatial resolution is a measure of how well an imaging system can display two closely spaced objects as separate; it determines the sharpness of the structural lines in the
digital image
(a loss of sharpness is known as unsharpness)
23
Q
UNIT OF SPATIAL RESOLUTION:
WHAT IS ACR MINIMUM?
WHAT IS CLARITY OF AN IMAGE DETERMINED BY?
HIGHER THE SPATIAL RESOLUTION, THE _______ THE DETAIL
A
LINE PAIRS PER MM
2.5 LP/MM
SPATIAL RESOLUTION
SHARPER
24
Q
SIZE OF IS DETERMINED BY:
A
MATRIX SIZE & FIELD OF VIEW SIZE
25
WHAT IS THE MATRIX SIZE?
WHAT IS THE FIELD OF VIEW SIZE?
WHAT SIZE IS DESIRED FOR FIELD OF VIEW? MATRIX? PIXEL?
number of columns and rows that are displayed
on the monitor
WHAT IS SEEN ON DISPLAY MONITOR
the smaller the field of view, the smaller the pixel and the better the spatial resolution;
- the same number of columns and rows are fit into a smaller field of view, making the pixel size smaller which improves the spatial resolution;
26
DETAILS SMALLER THAN PIXEL SIZE =
CR PIXEL SIZE DETERMINED BY:
FLAT PANEL DETECTOR IS MADE OF:
CAN NOT BE RECORDED
CR = SIZE OF LASE & LIGHT SPREAD
MILLIONS OF INDIVIDUAL DELS
27
WHAT IS PIXEL PITCH?
WHY DOES OID DECREASE SPATIAL RESOLUTION?
HOW DOES GREATER SID AFFECT SPATIAL RESOLUTON?
DISTANCE BETWEEN CENTER OF ONE PIXEL TO CENTER OF THE OTHER
DUE TO MAGNIFICATION
LONGER SID = MORE CR USED IN IMAGE = BETTER SPATIAL RES.
28
WHAT IS DISTORTION?
TYPES:
FACTORS:
misrepresentation of the true size or shape of an object
PHOTO & GEOMETRIC
OID, SID, PATIENT FACTORS & ANGLE/EQUIPTMENT
29
TO PREVENT SHAPE DISTORTION = (IR / PART/ CR RELATIONSHIP)
CR ANGLED =
OBJECT/PART ANGLED =
OBJECT & IR PARALLEL, CR PERPENDICULAR
CR ANGLED = ELONGATED
OBJECT ANGLED = FORESHORTENED
30
INVERSE SQUARE LAW FORMULA =
31
EXCPOSURE MAINTANCE FORUMLA =
AKA =
DIRECT SQUARE LAW
32
MAGNIFICATION FACTOR FORMULA =
MF = SID/SOD
33
FIXED VS VARIABLE KVP:
CAST & TECHNICAL FACTORS:
WET PLASTER:
DRY PLASTER:
FIBROGLASS:
fixed kVp technique charts set a kVp for a particular part and then varies the mAs to control the exposure for various part thicknesses
variable kVp technique charts set a mAs for a particular part and then varies the kVp to control the exposure for various part thicknesses
plaster would require a 15 kVp increase when wet and 10 kVp increase when dry
casts made of fiberglass usually do not require an increase in kVp,
thicker fiberglass wraps may require a 5 kVp increase
34
ADDATIVE PATHOLOGY = ____ KVP CHANGE
DESTRUCTIVE PATHOLOGY = _____ KVP CHANGE
IN PEDS, USE ____ MAS & _____ KVP
DO YOU CHANGE KVP FOR GERIATRICS
KVP FOR IODINATED:
KVP FOR BARIUM:
ADD 5
SUBTRACT 5
SHORTEST EXP. TIME & INCREASED KVP
TYPICALLY THINNER SO DECREASE KVP
DONT EXCEED 70 KVP
DONT EXCEED 100 KVP
35
WHAT IS AEC?
WHAT DOES IT PROVIDE?
WHAT MUST YOU ENSURE WITH AEC?
Use either photocells or ionization chambers to achieve a predetermined exposure, all other Technical factors (kVp, mA, SID, focal spot size, grid ratio, screen speed, etc.) must be set by the Radiographer.
exposure provides a constant optical density regardless of the patient thickness which typically results in a reduction in repeat images,
correct detector selection and current positioning over photocell
36
SPATIAL RESOLUTION BEST WITH WHAT SIZE PIXEL, MATRIX & FIELD OF VIEW?
IN FLAT PANEL DETECTORS, PIXEL SIZE IS DETERMINED BY:
WHAT IS FILL FACTOR?
LARGE MATRIX, SMALL FIELD OF VIEW & SMALL PIXEL SIZE
DEL SIZE
fraction of each detector element that efficiently
collects charges from the energy deposited by the x-ray signal
37
THE LARGER THE MATRIX, THE ______ THE PIXEL OR DEL
WHAT IS SAMPLING FREQUENCY?
WHAT IS RELATION WITH PIXEL PITCH?
SMALLER
-number of times data is recorded as an imaging plate is being read
- faster the sampling frequency the smaller the pixel pitch and the better the spatial resolution
38
WHAT IS BIT DEPTH?
THE GREATER THE BIT DEPTH, THE ______ IMAGE QUALITY
WHAT IS MTF?
WHAT DOES IT RESULT IN?
number of shades of gray that can be used to define each pixel
GREATER BIT DEPTH = MORE SHADES = HIGHER QUALITY IMAGES
modulation transfer function (MTF)
MTF is a measure of how well an imaging system can transfer a signal
-REDUCED CONTRAST
39
WHAT IS DQE?
WHAT DOES IT MEASURE?
detective quantum efficiency (DQE)
how efficiently a system converts the x-ray input signal into a useful output image
IMAGE QUALITY
40
WHAT IS DYNAMIC RANGE?
BETTER IN DIGITAL OR FILM?
QUANTUM MOTTLE VS QUANTUM NOISE:
WHEN DOES THIS OCCUR?
the range of exposures that may be captured by a detector
DIGITAL HIGHER
MOTTLE = FILM, NOISE = DIGITAL
WHEN IR EXPOSURE IS 50% OR BELOW EXPOSURE
41
TYPES OF NOISE IN DIGITAL:
WHAT IS SNR?
WHAT SNR IS DESIRED?
detector noise and quantum noise
signal to noise ratio (SNR)
if the image signal (exposure) is high enough, both types of noise can be eliminated
a high SNR produces better images
42
WHAT ARE FLUX LINES?
WHEN IS A MAGNETIC FIELD INDUCED?
FERROMAGNETIC MATERIAL MEANS:
EXAMPLE:
NON-MAGNETIC MATERIAL EXAMPLE:
PARAMAGNETIC MATERIAL MEANS:
EXAMPLE:
MAGNETIC FIELD LINES
whenever there is a charge in motion (electric current).
MAGNETIC, IRON
RUBBER
ALUMINUM / WEAKLY MAGNETIC/ATTRACTED
43
OPERATING CONSOLE CONSISTS OF:
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
on/off switch
mA selector
time selector
kVp selector
focal spot size
grid movement (correct selection of Bucky)
tube selection [RAD 1] [RAD 2] [Fluoro]
automatic exposure control (AEC)
anatomically programmed radiography (APR)
rotor switch and exposure switch
44
NEGATIVE TERMINAL OF XRAY TUBE =
WHAT IS DUAL FOCUS TUBE?
WHAT IS IT MADE OF?
what does a focusing cup do?
CATHODE
electrons are released from one of the two filaments
(large and small tungsten filaments);
cup focuses the electrons into a narrow beam that is directed toward the anode
45
WHAT IS ELECTRON SOURCE?
WHAT IS THE POSITIVE TERMINAL OF XRAY TUBE?
WHAT IS IT MADE OF?
CATHODE
ANODE
tungsten disk (alloyed with rhenium to handle the stress, layered with molybdenum to minimize weight);
46
WHAT ARE TWO TYPES OF ANODES?
XRAY USES:
ANODE IS MADE OF
WHY?
stationary and rotating,
ROTATING
tungsten - HIGH ATOMIC #, HIGH MELTING POINT & GOOD HEAT CONDUCTOR?
-alloyed with rhenium to handle the stress,
-layered with molybdenum to minimize weight);
47
ANODE ANGLE RANGE: ___________
WHY?
WHAT IS THE ACTUAL FOCAL SPOT?
WHAT IS THE EFFECTIVE FOCAL SPOT?
10-17*
10 = ANODE HEEL EFFECT
12* TO COVER 14X17
ACTUAL = AREA ON ANODE EXPOSED TO ELECTRONS
EFFECTIVE = PROJECTED ON PATIENT / IR
48
TUBE FAILURE RELATED TO:
HOW CAN THIS BE PREVENTED?
WHAT IS INDUCTION MOTOR MADE OF?
WHAT IS INDUCTION MOTOR?
THERMAL CHARACTERISTICS
WARM-UP PROCEDURES
copper rotor
induction motor is an electric motor that uses electrical
current to magnetize the stator and the rotor, causing the rotor to spin
49
WHAT MAGNETIZES THE STATOR & ROTOR, CAUSING THE ROTOR TO SPIN?
HOW FAST DOES MOTOR SPIN? WHY?
WHAT IS AEC?
INDICTUION MOTOR
3600 RPM FOR HEAT DISTRIBUTION ACROSS SURFACE
automatic exposure control (AEC) designed to reproduce a predetermined exposure
50
WHAT IS AN IONIZATION CHAMBER?
HOW DOES IT WORK?
WHERE IS IT LOCATED/WHY?
RADIATION DETECTOR IN AEC
an ionized gases' electrons will charge a capacitor and shut off the exposure at a predetermined mR , once the correct number of x rays have passed through the patient the exposure will automatically shut off
the ionization chamber located between the patient and the image receptor so the number of x rays can be measured before they reach the image receptor
51
WHAT IS A PHOTOMULTIPLIER TUBE?
HOW DOES IT WORK?
AEC PROVIDES ___________ FOR STRUCTURES LOCATED _________.
RADIATION DETECTOR IN AEC
a photocathode's electrons will charge a capacitor and shut off the exposure at a predetermined mR
AEC devices provide proper exposure for structures positioned directly above the Selected ionization chambers
52
BACK UP TIMER SET FOR:
IF TIMER TOO SHORT:
- RESULTING IN:
WHAT IS MOST IMPORTANT ABOUT AEC?
150 percent of the anticipated time
when the back-up time is too short, it will terminate the exposure before the AEC signal
- producing an underexposed image
POSITIONING OVER CORRECT IONIZATION CHAMBER
53
IS EXPOSURE ADJUSTMENT USED TO COMPENSATE FOR PART THICKNESS ?
WHAT IS MINIMUM RESPONSE TIME?
WHAT IS IT IN AEC?
WHY IS IT IMPORTANT TO KNOW IN AEC?
exposure adjustment should not be used to compensate for part thickness
the shortest exposure time that a system can produce
with AEC the time is approximately 1 ms
ensure that your AEC exposure times do not fall below this time
54
WHAT ARE THE MANUAL EXPOSURE FACTORS?
________ - CONTROLS QUANTITY OF XRAYS, AKA: ______
________ - CONTROLS QUALITY OF XRAYS, AKA ______ & ______
WHAT IS BEAM RESTRICTION USED FOR?
MAS & KVP
mAs - quantity of x rays AKA exposure
kVp - quality of x rays AKA penetrability & subject contrast
e. beam restriction
used to restrict the beam to the area of interest
55
WHAT ARE TYPES OF BEAM RESTRICTIONS USED?
WHAT DOES KVP CONTROL?
WHAT DOES MAS CONTROL?
automatic collimators/collimators
cylinders and extension cylinders
cones and diaphragms
KVP = QUALITY, PENETRABILITY, SUBJECT CONTRAST
MAS = QUANITY, EXPOSURE
56
WHAT IS TRANSFORMER LAW FORMULA?
WHAT IS THE TURNS RATIO?
Transformer law: Vs/Vp = Ns/Np
(V is the voltage generated in the circuit,
N is the number of turns of the coil,
s is secondary,
p is primary)
(Ns/Np is the turns ratio)
57
FORMULA FOR POWER =
OHMS LAW FORMULA =
Power: P=IV
(I is current and V is volts)
Ohm’s law: V=IR
(V is volts, I is current, R is resistance)
58
WHAT TYPE OF STUDY IS FLURO?
DIGITAL FLURO SYSTEMS USE _______________ OR ____________
WHAT IS FPD? WHAT DOES IT REPLACE?
HOW DOES IT WORK?
fluoroscopy is a dynamic study
-a CCD camera coupled to the image intensifier
- or a dynamic flat-panel detector
FLAT PANEL DETECTOR:
FPD Replaces the image intensifier;
the analog signal is sent to an analog-to-digital converter;
59
INPUT PHOSPHUR OF IMAGE INTENSIFER IR MADE OF:
STEPS:
1. INPUT PHOSPHUR ABSORBS ________ & EMITS _________
2. _________ ABSORBS _______ & EMITS _____________
3. _________ ACCELERATE & FOCUS ELECTRONS
4. __________ CONVERTS ELECTRONS INTO _______
(cesium iodide)
1. absorbs the x-ray photons and emits light photons
2. photocathode absorbs light photons & emits electrons
3. electrostatic lenses
4. output phosphor TO electron into visible light image
60
WHAT IS FORMULA FOR BRIGHTNESS GAIN
WHEN DOES IT OCCUR?
WHAT REPLACED IMAGE INTENSIFIER? WHY?
(flux gain x minification gain)
occurs from acceleration and focusing of the electron beam
the flat panel
- dynamic images can be displayed in real time
- high low-contrast resolution
- high DQE, distortions are eliminated
61
ANOTHER NAME FOR AUTOMATIC BRIGHTNESS CONTROL?
WHEN IS IT USED?
WHAT DOES ABC DO?
HOW DOES IT DO THIS?
WHY IS IT BETTER?
automatic exposure rate control (AERC)
IN FLURO
maintains image brightness
- by adjusting for part thickness by automatically varying
the kVp, mA, or both
-adjusting automatically is faster than manually, thereby reducing fluoroscopy time and patient exposure
62
WHAT IS MAGNIFICATION MODE IN FLURO?
WHY USED? WHATS THE CON?
WHY IS FPD PREFFERED?
- make small details easier to see with image intensification,
- better spatial resolution but higher patient exposure
- FPD allow the operator to zoom without an increase in spatial resolution or patient exposure
63
IMPORTANT CHARACTERISTIC OF FLURO TABLE =
GRIDS ARE DESIGNED TO:
MADE OF:
WHAT IS GRID RATIO?
- table cannot absorb too much radiation to avoid shadows, loss of signal and loss of contrast in the image
- absorb scatter
- radiopaque strips of lead, & radiolucent strips of aluminum
grid ratio is height of the lead strips divided by the distance between the strips;
64
GRID RATIO FOR DIGITAL RADIOGRAPHY? WHY?
WHAT IS MOIRE EFFECT?
WHAT DIRECTION SHOULD GRID LINES BE?
TYPES OF GRIDS?
high ratio to compensate for the higher grid frequency
-Moire effect = false linear pattern
-grid lines should be perpendicular to the direction of the laser scans
- focused or unfocused
65
DIFFERENCE BETWEEN FOCUSED & UNFOCUSED GRIDS?
WHAT IS GRID CUTOFF?
CAUSES OF GRID CUTOFF?
RESULTS OF GRID CUTOFF?
HOW IS IT ADJUSTED IN DIGITAL?
focused grids have their lead strips angled so they will
match the divergence of the x-ray beam,
- unfocused grids have parallel lead strips
grid cut-off is an error where the primary x-ray beam gets absorbed by the grid
1. off-level
2. off-center
3. off-focus
- grid cutoff will produce an image with low contrast, quantum noise and an incorrect exposure indicator number
- in digital, histogram analysis tries to rescale the digital image
66
WHAT IS BUCKEY ASSEMBLY?
WHAT DOES IT DO?
WHAT IS IT CALLED?
- device that moves grid during exposure,
- blurs the lead strips so they will not be visible on image
- Potter-Bucky diaphragm
67
WHAT ARE PREPROCESSING FUNCTIONS?
____________ - each pixel is assigned a number and a predesigned grayscale is assigned to that number
a pixel represents what?
analog-to-digital converter (ADC)
quantization
corrections (e.g., rescaling, flat fielding, dead pixel correction)
HISTORGRAM
b. quantization
- each pixel represents a voxel (volume element) within the patient
68
PRE PROCESSING CORRECTIONS INCLUDE:
__________ - the histogram has the ability to determine which numbers represent anatomy and which ones represent areas outside of the anatomy values of interest
__________ - dead pixels are removed from the matrix by making a mask of the dead pixels
___________ - using a software technique, dead pixels are identified in the matrix and then removed from all subsequent images
- rescaling, flat fielding, dead pixel correction)
rescaling
flat fielding
dead pixel correction
69
What is a graphical display of the pixel values that make up the image versus the frequency of those values?
WHAT ARE THREE PURPOSES OF HISTOGRAM?
WHATS USED FOR EXPOSURE INDICATOR DETERMINATION?
HISTOGRAM
1. determine the values of interest
2. determine the median number,
3. automatically rescale the values of interest
- the median number is used for exposure indicator determination
70
IN DIGITAL, WHAT IS "SCALE OF CONTRAST"
________ - refers to the number of different shades of gray visible in a digital image
FEW SHADES =
SEVERAL SHADES =
grayscale
grayscale
- few shades of gray (short grayscale), you have high contrast
- several shades of gray (long grayscale), you have low contrast
71
LONG GRAYSCALE MEANS:
SHORT GRAYSCALE MEANS:
WHAT IS EDGE ENHANCEMENT?
WHAT IS THE BENEFIT OF IT?
LONG = LOW CONTRAST, SEVERAL SHADES OF GRAY
SHORT = HIGH CONTRAST, FEW SHADES GRAY
- (S.H.O. - SHORT SCALE, HIGH CONTRAST, ONLY FEW GRAYS)
- increases the contrast along the edges of structures
- it improves the visibility of details
72
WHAT CAUSES HALO EFFECT?
_________ -process by which soft tissue and bone are enhanced so all the information within a ROI seen
EXCESSIVE ABOVE CAN RESULT IN:
WHAT DOES SMOOTHING CAUSE?
excessive edge enhancement causes a halo artifact around edges
c. equalization
(excess equalization can cause noise or saturation)
smoothing causes a loss of spatial resolution
73
Histogram numbers that represent anatomy are referred to as ___________(____)
_________ - convert the values of interest to different numbers to determine the grayscale in an image
EACH ANATOMICAL PART HAS OWN ___________ TO DEPICT ITS GRAYSCALE / CONTRAST
value of interest (VOI)
look-up table (LUT)
each anatomical part has its own look-up table
74
POST PROCESSING FUNCTIONS INCLUDE:
__________ - intensity of light of the various pixels that make up the image on a monitor.
_______ - range of values/shades of gray displayed by an imaging system
WHAT ARE LOOK UP TABLES USED FOR?
brightness, stitching, electronic cropping, contrast, ROI
brightness
the dynamic range
- used to enhance the contrast in a digital image
75
WHY IS BRIGHTNESS NEEDED IN DIGITAL?
IN A LUT, THE STEEPER THE SLOPE, THE ________ CONTRAST
WHAT IS ELECTRONIC CROPPING USED FOR?
AKA?
WHAT IS STITCHING FOR?
-to make the details in a digital image visible
- the steeper the slope the higher the contrast.
- image may be surrounded by white light on the display monitor; this white light can fatigue the radiologist's eyes or worse, cause a misdiagnosis
- cropping or masking that turns this white area black; the
masking feature can be turned on or off
- allows multiple images to be joined when the anatomy is too large for one exposure the final image is a seamless image
76
QUALITY OF IMAGE / ACCURACY DEPENDS ON:
1. _________ 2. _________ 3. _________
__________ - the amount of light emitted from the monitor
THE BRIGHTER THE IMAGE, THE ______ THE CONTRAST RESOLUTION
_______ - the maximum angle at which a display monitor can be viewed with acceptable visual performance
1. spatial resolution
2. luminance
3. contrast resolution
luminance
the brighter the image the better the contrast resolution
viewing angle
77
__________ - the overall illumination of a room
CONSIST OF:
_________ - the ability of the monitor to display fine details
PIXEL SIZE IS DETERMINED BY ______
___________ - the distance from center-to-center of pixels
ambient lighting
- consists of natural light, fluorescent lights and lamps;
b. spatial resolution
pixel size is determined by the pixel matrix
pixel pitch
78
WINDOW LEVEL =
____________ - intensity of light of the various pixels that make up the digital image on a monitor
WINDOW WIDTH =
________- in digital imaging is the difference in brightness between adjacent areas on a display monitor
__________ - a standard for handling, storing, printing, and transmitting information
LEVEL = BRIGHTNESS
BRIGHTNESS
WIDTH = CONTRAST
DICOM (Digital Imaging and Communications in Medicine)
79
_______ - term used to describe the long-term storage of images and documents
_________ - includes the acquisition, transmission, archive and display of digital images all via a computer network
_________ - Intranet used in the radiology department to store, manipulate and distribute patient data and images;
_________ - patient information can be accessed from
a number of locations; all that is needed is a user ID and password to get access
archive
PACS (picture archival and communication system)
RIS (radiology information system)
HIS (hospital information system)
80
RIS COMPRISED OF: 1. ____ 2. _____ 3. ____& 4. ______
WHERE ARE ORDERS & WORKLISTS LOCATED?
__________ - digital version of a chart with patient information
stored in a computer
INCLUDES WHAT INFO?
RIS = Patient tracking, scheduling, reporting and image tracking
Located in HIS
electronic medical record (EMR)
- medical history, diagnosis, medications, immunization dates and allergies
81
DIFFERENCE BETWEEN EMR & EHR
DIFFERENCE BETWEEN RAM & ROM
EMR are limited to the practice
electronic health records (EHR) makes the information available to practices and health organizations
- RAM or random access memory
data that can be accessed at random from anywhere in main memory in equal amounts of time, regardless of where they are located.
- ROM or read only memory contains manufacturer supplied information that cannot be written to or erased by the user.
82
________ - expresses the original x-ray exposure to the image receptor and thus the patient
LOW CAUSED BY? RESULTS IN?
HIGH CAUSED BY? RESULTS IN?
DESIRED TECHNICAL FACTORS:
________- insufficient number of x rays striking the image receptor results in this
exposure indicator
- low exposure indicator = insufficient exposures and can cause quantum noise
- high exposure indicator = high exposures and can cause unacceptable high levels of exposure to the patient
high kVp and low mAs
quantum noise (quantum mottle)
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QUANTUM NOISE VS QUANTUM MOTTLE
AN IMAGE (UNDER OR OVER) EXPOSED BY ____% WILL HAVE QUATUM NOISE.
________ - if the image receptor is grossly overexposed, causing black areas in the image.
- BAD BECAUSE:
HOW DOES DIGITAL ADJUST OVEREXPOSURE?
Q. NOISE = DIGITAL / Q. MOTTLE = FILM
underexposed by 50% or more / 2X underexposed
saturation
- anatomical information will be lost;
- histograms can readjust the brightness by automatic rescaling;
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IF HISTOGRAM DOESNT MATCH PART, WHAT OCCURS?
HOW CAN PROTHESIS EFFECT AN IMAGE?
WHAT IS WORSE, SCATTER RADIATION OR BACKGROUND RADIATION? WHY?
WHEN IS LOSS OF CONTRAST NOTICEABLE IN DIGITAL?
- image may be automatically rescaled too light or too dark
a prosthesis may cause the image to be too dark because the prosthesis is automatically rescaled to normal tissue density making the normal tissue too dark
- scatter radiation will degrade the image more than background radiation
-noticeable when the image receptor is 4X overexposed;
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HISTOGRAMS ANALYZING INFORMATION OUTSIDE AREA OF INTEREST RESULTS IN:
WHAT CAUSES HISTOGRAM ANALYZE INFO OUTSIDE AREA?
IMAGES COMING OUT TOO LIGHT USUALLY RESULT OF:
LOW CONTRAST IAGES ARE USUALLY _________ IMAGES
come out too dark
1. improper collimation
2. collimating too tightly
3. scatter or off-focus radiation obscuring collimated borders;
1. grid cut-off
2. gross underexposure
- overexposed images that have been automatically rescaled
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HOW DOES GRID CUTOFF PRODUCE LOW CONTRAST IMAGES?
WHEN PROPER CONTRAST ISNT PRESENT, ITS BECAUSE:
1.
BECAUSE histogram analysis tries to rescale the digital image to the proper brightness which produces the low contrast, quantum noise, and an incorrect exposure indicator number
1. insufficient data (e.g., grid cut-off, poor
collimation, overexposure or underexposure),
2. an unexpected object in the field,
3. a failure to erase the plate,
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TYPES OF FILTRATION:
DIFFERNECES:
spatial resolution will be the best when _________ is used
beam filtration and compensating filtration
beam filtration filters the low energy x rays from the x-ray beam,
compensating filter designed to compensate for differences in tissue thicknesses
spatial resolution will be the best when the small focal spot is used;
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VOLUNTARY VS INVOLUNTARY MOTION
BEST WAY TO PREVENT MOTION?
_________- misrepresentation of the true size or shape of an object
MAGNIFICATION IS CONTROLLED BY:
-voluntary motion can be controlled by the patient
- involuntary motion is a result of physiological activities within the body and cannot be controlled by the patient;
shortest possible exposure time
distortion
OID and SID
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INCREASE IN OID = ______ MAGNIFICATION
INCREASED SID = ______ MAGNIFICATION
MOST COMMON ARTIFACTS:
GRID LINES ARE CAUSED BY:
an increase in OID will increase magnification
an increase in SID will decrease magnification
-forgetting to remove jewelry and clothing is the most common cause of artifacts on images
- improper grid alignment which will cause grid cut-off (off-level, off-center, off- focus)
90
________ - WAVY PATTERN (FALSE-LINEAR PATTERN) IN IMAGES
WHEN DOES ALIASING OCCUR? RESULT IN?
WHAT IS NYQUIST FREQUENCY?
_________- an image from the previous exposure if the imaging plate is not fully erased
______- alternating light/dark strips caused by transport of the imaging plate through the CR reader in the slow scan direction
Moire effect
aliasing is caused when the sampling frequency is less than two samples per cycle (Nyquist frequency) and it produces an inaccurate image manifested by a Moire pattern;
ghost image may be
banding artifact
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WHAT CAUSES MOIRE EFFECT?
WHAT IS THE SOLUTION?
WHAT CAUSES FOG ON IMAGE?
- digital system is sampling at the same frequency as the grid frequency and the grid lines run in the same direction as the laser is reading the imaging plate,
- 1. sample the digital data at a faster frequency
- 2. use a higher frequency grid
- 3. make sure the grid lines are perpendicular to the direction of the laser beam
electromagnetic radiation from a variety of sources (light, x rays, gamma rays, heat) can fog a digital image
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LIGHT FIELD TO RADIATION ALIGNMENT = _____% OF ____
WHAT HAPPENS IF SID DOESNT MATCH FOCAL RANGE?
WHAT HAPPENS IF CR IS NOT TO CENTER OF FOCUSED GRID?
WHAT DOES "OFF-LEVEL" MEAN? RESULTS IN?
- no more than +/- 2% of the SID
UNDEREXPOSED
UNDEREXPOSED
GRID & CR ARENT PERPENDICULAR
