CHAPTER 11 Flashcards
1
Q
What is the RADIOLOGIC EQUIPMENT designed with?
A
It is designed with many devices that radiologists and technologists can use
2
Q
What is the RADIOLOGIC EQUIPMENT designed for?
A
It is designed to:
▫To optimize the quality of the image
▫ To reduce radiation exposure to patients undergoing various imaging procedures
3
Q
What are EQUIPMENT COMPONENTS, ACCESSORIES AND METHODS ARE AVAILABLE TO?
A
They are available to
“Minimize radiation exposure of patients”
4
Q
Measures must be taken to ensure that radiographic equipment operates safely to protect?
A
-All Patients
-All personnel
5
Q
What must every diagnostic imaging system must have ?
A
They must have a:
▫ Protective tube housing
▫ Correctly functioning control panel
6
Q
A radiographic examination table and other devices and accessories must be designed to?
A
Reduce the patient’s radiation dose.
7
Q
Diagnostic-Type Protective
Tube Housing
A
What are the requirements?
8
Q
What type of tube housing is required?
A
A lead-lined metal diagnostic-type protective tube
9
Q
What is a A lead-lined metal diagnostic-type protective tube required to do?
A
It is required to protect the patient and imaging personnel from
-Off-focus radiation
leakage radiation
10
Q
HOW DOES tube housing protect the patient from leakage radiation or OFF FOCUS?
A
By restricting the emission of x-ray to the area of the useful or primary beams.
11
Q
What standard must X-ray tube housing meet to limit radiation leakage away from the useful beam?
A
The tube housing must ensure that radiation leakage does not exceed 0.88 mGya/hr (100 mR/hr) at a distance of 1 meter
-HIGHEST VOLTAGE?
when the tube is operated at its highest voltage and current for continuous operation.
12
Q
What is the maximum allowable radiation leakage from an X-ray tube housing, measured at a distance of 1 meter, when operated at its highest voltage and current for continuous operation?
A
0.88 mGya/hr (100 mR/hr).
13
Q
Where must the CONTROL PANEL/CONSOLE be located?
A
Must be located behind a suitable PROTECTIVE BARRIER that has a radiation-absorbent window that permits observation of the patient during any procedure
14
Q
What must the CONTROLE PANEL/CONSOLE INDICATE?
A
Must “indicate the conditions of exposure and provide a positive indication when the X-ray tube is energized”
15
Q
The control panel, where technical exposure factors are selected and visually displayed for the equipment operator, must be located?
.
A
behind a suitable protective barrier that has a radiation-absorbent window that permits observation of the patient during any procedure.
16
Q
What must be visable on the CONTROL PANEL?
A
- Has visible mA and kVp digital readouts that permit the
operator to assess exposure conditions
17
Q
When the exposure begins, how do you know? What is emitted? And what is stopped when the exposure terminates?
A
When the exposure begins,
A TONE is emitted,
and the
SOUND stops when the exposure terminates.
18
Q
What does AUDIBLE SOUND indicates?
A
Audible sound indicates that the
- x-ray tube is energized and
- ionizing radiation is being emitted
19
Q
RADIOGRAPHIC TABLE
A
REQUIRMENTS?
20
Q
Why must the RADIOGRAPHIC EXAM TABLE BE STRONG?
A
Must be strong enough to adequately SUPPORT PATIENTS who WEIGHT IS IN EXCESS OF 400LBS
21
Q
HOW MUCH LBS SHOULD THE TABLE BE ABLE TO SUPPORT?
A
EXCESS 400LBS
22
Q
What are the pros of having a FLATING TABLE TOP?
A
A floating table top makes it easier to maneuver the patient
23
Q
How should the THICKNESS OF THE TABLE be?
A
Must be of UNIFORM THICKNESS
24
Q
Should the table be RADIOPAQUE OR RADIOLUCENT?
A
It should be a RADIOLUCENT TABLE
25
Why should it be RADIOLUCENT?
Must be as radiolucent as possible so that it will absorb ONLY THE MINIMAL AMOUNT OF RADIATION
26
What radiolucent material is the table made with?
CARBON FIBER
27
Which of the following materials is commonly used in the tabletop of a radiographic examination table to make the tabletop as radiolucent as possible so that it will absorb only a minimal amount of radiation, thereby reducing the patient’s radiation dose?
Carbon fiber material
28
What does table also contain?
1. GRID
2. SLOT COVER
29
SOURCE TO IMAGE DISTANCE (SID)
REQUIREMENTS
30
What does the SID MEASURE?
SID measures the distance from the anode focal spot to the IR
(XRAY TUBE TO IR)
31
What are used to measure SID?
-Simple tape measure
-lasers
Are also frequently used to
measure SID.
32
Distance and centering indicators must be accurate to?
Collimator/light field to radiation field alignment: Must be accurate to within
within 2% and 1% of the SID,
respectively.
2% of the source-to- image receptor distance (SID)
33
When a quality control test is performed to ensure that the penetrating ability of the x-ray beam is accu- rate, the result must be within what amount of the control panel setting?
a. 2% of SID
34
The collimator must be accurate to a level of:
±2% or 1% of SID
35
These two coincidence requirements are respectively known as:
* Alignment * Congruence
36
XRAY BEAM LIMITATION DEVICES (BEAM LIMITERS)
-COLLIMATORS
-CYLINDER CONES
-APERATURE DIAPHRAM
37
What must the primary x-ray beam size be limited to?
no larger than the size of the IR being
used for the examination
38
What is Light-localizing variable-aperture rectangular collimator?
It is used to adjust the size and shape of the x-ray beam either automatically or manually.
39
What device is currently the PREDOMINENT X RAY BEAM LIMITATION DEVICE?
THE COLLIMATOR
40
What is the purpose of the COLLIMATOR?
It reduces scatter radiation
41
What is the construction of light-localizing variable-aperture rectangular collimators?
Construction
(2 sets of lead shutters, light
source and mirror)
42
MY NOTES
1ST SHUTTER
( Higher set of lead shutters) is placed near the x-ray tube window to absorb off-stem (off-focus) radiation
2ND SHUTTER
( lower set of lead shutters) is placed near the bottom of the collimator box to restrict the beam further as it exits
43
What is the 1st SHUTTERS placed close to the windows for?
Reduction of off-focus radiation
44
MY NOTES ON SKIN SPARING and XRAY SYSTEMS
Skin sparing refers to the practice of reducing the radiation dose delivered to the skin during an X-ray procedure to minimize the risk of skin damage.
2 XRAY SYSTEMS
-FIXED
-MOBILE
45
In skin sparing, how much cm below the skin surface should be from the collimator box?
Skin sparing (skin surface below coll box minimum
-15cm for fixed xray system
-30cm for mobile xray system
46
What is LUMINENCE?
Brightness of light source
(Luminance is a technical term referring to the brightness of a surface)
47
Luminance is determined by measuring the concentration of light?
Over a particular field of view.
48
WHAT DOES LUMINENCE QUANTIFIES?
luminance quantifies the intensity of a light source (i.e., the amount of light per unit area coming from its surface
49
In Alignment and Congruence:
Coincidence between the radiographic beam and the localizing light beam.
-Has a 2% limit
my notes : congruence ensures that what you see in the light field is exactly what will be captured on the radiograph.
50
MY NOTES
What are POSITIVE BEAM LIMITATIONS(PBL)
AKA AUTOMATIC COLLIMATORS
Positive beam limitation (PBL) A feature of radiographic collimators that automatically adjusts them so that the radiation field size matches the size of the image receptor. Also known as automatic collimation.
51
Positive beam limitation (PBL) is also known as:
Automatic collimation
52
in Positive beam limitation
(PBL) WHAT SHOULD THE RADIOGRAPHER ENSURE?
The radiographer must ensure that collimation is adequate by
collimating the radiographic beam so
that it is no larger than the IR.
53
What is the Benefit of restricting x-ray
field size to include only the anatomic structures of clinical interest?
- Significant reduction in patient dose because less scatter radiation is produced
▫ Improves the overall quality
of the radiographic image
54
WHAT ARE CONES USED FOR?
Sometimes used for radiographic
examinations of specific areas such as the head
55
What areas of the body are CONES USED FOR?
THE HEAD
Cones may be used for exam of the os calcis, various skull projections, and cone-down views of vertebral bodies
56
WHERE ARE BEAM-DEFINING CONES USED IN WHAT TYPE OF RADIOGRAPHY?
DENTAL RADIOGRAPHY
57
CONES ARE?
are circular metal tubes that attach to the X-ray tube housing or variable rectangular collimator to limit the radiographic beam to a predetermined size and shape.
58
What are 2 types of cones?
Cone fashioned in the form of
1. flared metal tube
2. straight cylinders
59
What is the APERTURE DIAGRAM?
(MY NOTES)
1. Flat piece of lead with a circle/HOLE or square opening in the middle
2. Placed as close to the x-ray tube window as possible (PLACED DIRECTLY BELOW WINDOW)
TO CONFINE THE PRIMARY RADIOGRAPHIC BEAM DIMENSION SUITABLE TO COVER A GIVEN SIZE OF FILM AT A SPECIFIC SID
3. Has no moving parts
60
When the aperture diaphragm is not adjustable, what is needed for each IR SIZE AND SID?
The aperture diaphragm is not adjustable, so a different diaphragm
would be needed for each IR size
and SID
61
FILTRATION OF THE BEAM
REQUIRMENT
62
What is the purpose of the FILTRATION OF THE BEAM?
Removes low-energy photons
63
WHAT IS FILTRATION?
Filtration removes low-energy photons (long-wavelength or “soft” x-rays) from the beam by absorbing them and permits higher-energy photons to pass through.
This reduces the amount of radiation that the patient receives.
64
What effect does FILTRATION have on patient dose?
Increases effective energy
(hardens beam and makes it
more penetrating)
Lowers patient dose
65
What are the 3 types of FILTRATIONS?
-Inherent
-Added
-Total Filtration
66
WHAT IS THE REQUIREMENT FOR TOTAL FILTRATION?
A minimum of 2.5 mm aluminum
equivalent total filtration is required for fixed radiographic units operating at above 70 kVp.
67
IN A STATIONARY (FIXED) RADIOGRAPHIC EQUIPMENT
(REQUIRED MIN TOTAL FILTRATION)
TUBE POTENTIAL MINIMUM TOTAL FILTRATION REQUIRED ( KVP) VS. MINIMUM FILTRATION REQUIRED
( SPECIFIED IN "mm Al Eq"
ABOVE 70 KVP------- 2.5 mm Al eq
50-70 KVP--------------1.5 mm Al eq
BELOW 50 KVP------0.5 MM Al eq
68
In "Required Filtration" for general diagnostic radiology, what is filtration widely expressed in?
Filtration is most widely expressed in "aluminum and/or its equivalent"
69
WHAT IS ALUMINUM VERY EFFECTIVE IN REMOVING WITHOUT DECREASING BEAM INTENISITY?
Aluminum is very effective in
"removing low-energy photons without
severely decreasing beam intensity"
70
What is the total mmAl eq for the 3 types of filtrations?
Inherent:
0.5 mm Al eq (glass and oil)
1 .0 mm of Al eq (collimator mirrors)
* Added:
1.0 Al (thin sheets of Aluminum)
* Total:
2.5 Al eq
71
How much mm Al Eq do Mobile diagnostic units and fluoroscopic equipment require for "TOTAL PERMENENT FILTRATION?
Mobile diagnostic units and fluoroscopic equipment require a minimum of:
2.5 mm Al Eq total permanent filtration.
72
WHAT IS HALF VALUE LAYER (HVL)?
Thickness of a designated absorber
(e.g., aluminum)
That is required to decrease the intensity of the primary beam by 50% of its initial value.
73
How much percent will decrease the intensity of the primary beam of its inital value?
50%
74
Why do we measure the HVL?
We measure it to verify that the X-ray beam is adequately filtered
75
When should a radiology physicist obtain the HVL MEASUREMENT
A radiologic physicist should obtain this
measurement at least once a year and also after an X-ray tube is replaced or when the housing or collimation have been repaired.
76
What is the HVL expressed in?
HVL is expressed in millimeters of
aluminum
77
WHAT DOES HVP MEASURE?
HVL is a measure of beam quality, or
effective energy of the X-ray beam.
A minimal HVL is required at a
given kVp.
78
Half value layer required by the radiation control for health and safety act of 1968
KVP HVL IN "mm Al eq)
30 0.3
40 0.4
50 1.2
60 1.3
70 1.5
80 2.3
90 2.5
100 2.7
110 3.0
120 3.2
79
What are Compensating filters made up of?
-Made of aluminum,
-lead-acrylic,
- or other suitable
materials
80
What are compensating filters used to accomplish?
Used to accomplish dose reduction and uniform imaging of body parts that vary considerably in thickness or tissue composition
81
What do compensating filters partially attenuates?
Partially attenuates X-rays that are directed toward the thinner, or less dense, area while permitting
more x-radiation to strike the thicker, or more dense, area
82
What are the 2 types of COMPENSATING FILTERS?
1. WEDGE FILTER
2. TROUGH, OR BILATERAL WEDGE FILTER
83
As an example the wedge filter is used to provide uniform density when?
the wedge filter is used to provide uniform density when the foot is undergoing radiography in the dorsoplantar projection.
For this examination, the wedge is attached to the lower rim of the collimator and positioned with its thickest part toward the toes and thinnest part toward the heel.
84
Required Radiation Exposure Characteristics
1. EXPOSURE REPRODUCIBILITY
2. EXPOSURE LINEARITY
85
Exposure Reproducibility
Consistency in output radiation
intensity for identical generator
settings from one individual
exposure to subsequent exposures
* Variance of 5% or less is
acceptable.
* Reproducibility may be verified by
using the same technical exposure
factors to make a series of
repeated radiation exposures and
then, observing with a calibrated
ion chamber, how radiation
intensity typically varies
86
Exposure Linearity
Consistency in output radiation
intensity at selected kVp settings
when generator settings are changed
from one mA and time combination
to another
* Linearity is the ratio of the
difference in mSv/mAs or mR/mAs
values between two successive
generator stations to the sum of
these mSv/mAs or mR/mAs values.
It must be less than 0.1.
* When settings are changed from one
mA to a neighboring mA station, the
most that linearity can vary is 10%.
87
When settings are changed from one
mA to a neighboring mA station, the
most that linearity can vary is?
10%.
88
What are Automatic Exposure Control (AEC) and Phototiming?
An x-ray termination device that ends the radiation when a predetermined amount of radiation is received by an arrangement of sensors.
* Designed to produce an acceptable image while limiting radiation exposure to the patient.
* Backup timer: safety feature
* Phototiming: old terminology referring to photomultiplier tubes
* Today’s AEC systems utilize ionization chambers.
89
What are RADIOGRAPHIC GRIDS?
A grid is a device made of parallel radiopaque strips alternately separated with low-attenuation strips of aluminum, plastic, or wood
90
What do Radiographic grids remove?
Radiographic grids remove scattered x- ray photons that emerge from the patient being radiographed before this scattered radiation reaches the image receptor and decreases radiographic
quality
91
Placement of a grid IS BETWEEN?
Placement of a grid is between
the patient and the IR
92
What is the FUNCTION of a RADIOGRAPHIC GRID?
It improves radiographic quality by removing unwanted scattered radiation before it reaches the IR. A grid significantly increases radiographic contrast and visibility of detail.
93
Grid ratio and patient dose
Patient dose increases whenever a grid is used.
Parts that measure 10 cm (4 inches) or more require the use of a grid.
Grid radio refers to the height of the lead strips divided by the distance between each strip.
94
The radiographic grid acts
as?
The radiographic grid acts as a sieve to block the passage of photons that
have been scattered at some angle from their original path
95
WHAT IS THE REQUIREMENT OF MOBILE RADIOGRAPHY?
Requirement
– Minimum SSD is at least 30 cm (12 inches)
– Distance generally used for mobile radiography is 100 cm
(40 inches) or even 120 cm (48 inches)
96
Effect of SSD on patient entrance exposure
-With Increased SSD such as 100 cm or 120 cm there is a more uniform distribution of exposure throughout the patient.
97
Use of mobile units
– Only for patients who cannot be transported to a fixed radiographic installation
98
Digital Processed Radiography
Imaging Modes
* Computed Tomography (CT)
* Computed Radiography (CR)
* Digital Radiography (DR)
* Digital Fluoroscopy (DF)
* Digital Mammography (DM)
99
Radiation Safety Features of Digital Imaging Equipment, Devices, and Accessories
Conventional Radiography: Analog image
▫ Latent image created
▫ Latent image processed to become analog image
▫ Produced optimal-quality images
▫ Processing was time-consuming.
▫ Images often lost.
▫ This technology has been replaced by digital imaging.
100
Digital Imaging Overview
* Process of producing an electronic image
* Inherent limitations with respect to spatial and contrast resolution due to dimensions of pixels.
* Subject to artifacts because digital images are produced collectively by an array or matrix of elements with finite dimensions and are subject to noise.
101
Digital Imaging Overview
* Latent image formed by X-ray photons on a radiation detector.
* Digital image when it is shown on its display
* Brightness is the “amount of luminance (light emission) of a display monitor.
* Gray scale-shades of gray constitute contrast
* Images composed of numerical data that is stored in rows and columns; image matrix
* Matrix comprised of picture elements, or pixels
102
Digital Radiography
▫ Image receptors convert energy into electrical signals.
▫ Scintillator: made of amorphous silicon, converts X-ray energy into visible light.
▫ Visible light is then transformed into electrical signals by charge-coupled devices (CCDs).
▫ Photoconductor: made of amorphous selenium, converts X-ray energy directly into electrical signals that are read by transistors.
* Images can be accessed at multiple workstations.
103
What are the two types of conversion in digital radiography?
Indirect conversion
Direct conversion
104
Computed Radiography (CR)
* Images generated using photostimulable luminescence (PSL)
* Use of conventional radiographic equipment, traditional patient positioning, and standard technical exposure factors
* CR filmless cassette containing a photostimulable phosphor
* Use of an image reading unit to scan the photostimulable phosphor image plate with a helium–neon laser beam
* Digital image display monitor
105
Computed Radiography (CR)
Kilovoltage flexibility
▫ CR has greater kilovoltage flexibility than does
conventional screen-film radiography.
* X-ray Beam Collimation
▫ Position the part at or near the center of the CR/IR
* Use of Radiographic Grids-should be used more frequently because the imaging plate is sensitive to scatter
106
What are the advantages of DIGITAL RADIOGRAPHY (DR)
* Lower doses
* Greater ease of use and
faster patient throughput
* Immediate imaging results
* Additional image manipulation
* Less overall maintenance
107
What are the disadvantages of DIGITAL RADIOGRAPHY (DR)
* Much more costly
* CR is compatible with a
wide range of preinstalled
traditional systems
* Single detector size
* PSP imaging plates are
subject to mechanical
damage and chemical
oxidation
* High replacement cost
108
Repeat Rates Digital Imaging
DR is subject to 3 types of artifacts such as Image
-Aliasing,
-Moiré Patterns and
-Contouring Defects
* DR eliminates the need for almost all retakes required because of improper technical selection because image
contrast and overall brightness may be manipulated after image acquisition.
* Increase in repeat rates due to ease of repeating image
* Mispositioning repeats should be monitored by an independent quality control technologist at a separate
monitor, or a quality control system should be used, whereby the number of images per examination is
compared with the number ordered for each technologist.
109
Repeat Rates in Digital Imaging
* Due to wide exposure latitude, image can be manipulated.
* Dose creep
* Exposure indicator
110
Radiation Safety Features of Digital Imaging Equipment, Devices, and Accessories
X-ray beam collimation and centering of body part on CR cassette
▫ Body area or part must be positioned in or near the center of the CR IR.
* Use of radiographic grids in CR
▫ CR is more sensitive to scatter radiation, so a grid should probably be used more frequently except for the majority of pediatric patients.
111
Fluoroscopic Procedures and
Patient Irradiation Rates
Dynamic, or active, motion images of selected anatomic structures
* Greatest patient radiation exposure rate in diagnostic radiology
* Responsibility of physician to evaluate the need for the examination
* Benefit versus risk
* Minimizing patient exposure time
112
Safety Features of Fluoroscopic
Equipment, Devices and Accessories
Fluoroscopy is the x-ray examination which demonstrates the motion of body parts while it is occurring. It is usually performed with a
fluoroscopic tube inside the x-ray table facing up toward the surface of the table.
Fluoroscopy extends over a number of minutes, and gives the highest patient doses in diagnostic radiography.
113
Fluoroscopic Imaging Systems:
Non-digital
REQUIREMENTS
114
Fluoroscopic Imaging Systems:
Non-digital
Brightness of the fluoroscopic
image and patient-absorbed
dose.
-Image intensifier converts the
pattern of X-rays transmitted
through the patient into a
corresponding and amplified
visible light pattern
115
BENEFITS OF IMAGE INTENSIFICATION FLUROSCOPY
1. INCREASED IMAGE BRIGHTNESS
2. SAVING OF TIME FOR THE RADIOLOGIST
3. PATIENT DOSE REDUCTION
116
Fluoroscopic Imaging Systems:
Non-digital
Image intensification fluoroscopy unit. The x-ray tube used in this unit is mounted beneath the unit’s
radiographic table, which supports the patient.
The image intensifier and other image detection devices are then
drawn forward and placed over the patient on the table to
perform the examination.
Other fluoroscopic equipment
arrangements are possible.
117
Fluoroscopic Imaging Systems:
Non-digital
- Image intensifier tubes and magnification
* Magnification mode
* Milliamperage
required and effect
on patient dose
118
Fluoroscopic Imaging Systems:
Non-digital
-Multified or magnification, image intensifier tubes
-SIZE
-NORMAL VIEWING MODE
-COMPONENTS
-METHOD OF OPERATION
-IMAGE QUALITY
-PATIENT DOSE CONSIDERATIONS
119
Safety Features of Fluoroscopic
Equipment, Devices and Accessories
Brightness of the fluoroscopic image is
increased 10,000 times compared to non-image-intensified fluoroscopy
Milliamperage is reduced from 3 to 5 mA to 1 to 1.5 mA.
* Patient dose is lowered
120
Fluoroscopic Imaging Systems:
Non-digital
Pulsed and interrupted fluoroscopy
▫ Significantly decreases patient dose, especially in long procedures
▫ Extends tube life
▫ Last-image-hold feature
* Limiting fluoroscopic field size
▫ Benefit of fluoroscopic field size limitation
▫ Fluoroscopic beam length and width limitation
121
Fluoroscopic Imaging Systems:
Non-digital
Radiation delivery factors
▫ Selection of technical exposure factors for adult
patients
-kVp range: 75 to 110 kVp for adults, depending on the body
area being examined
-SSD not less than 38 cm (15 inches) for stationary fluoroscopes; not less than 30 cm (12 inches) for mobile fluoroscopes
-Position of the input phosphor surface of the image intensifier in relation to the patient should be maintained as
close as is practical to reduce the patient’s entrance exposure
rate.
122
Fluoroscopic Imaging Systems:
Non-digital
Radiation delivery factors
▫ Selection of technical exposure factors for children
Percentage of kVp decrease compared to an adult
should be as much as 25%
Decreasing technical exposure factors, maintaining
SSD, and minimizing the height of the image intensifier entrance surface above the patient further
limit excessive exposure of the pediatric patient.
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