Radiation Protection/exposure Reduction Flashcards
(189 cards)
0
Q
Time
A
Minimizing the amount of time spent in the vicinity of the ionizing radiation source
1
Q
The 3 cardinal rules for protection of personnel
A
Time
Distance
Shielding
2
Q
Distance
A
Maximize the distance between your body and the source of ionizing radiation
3
Q
Shielding
A
Interpose as much shielding material as possible between your body and the source of ionizing radiation
4
Q
Two types of fixed barriers
A
Primary protective barriers
Secondary protective barriers
5
Q
Primary protective barriers
A
Areas exposed to direct impact of the primary X-ray beam (up to 140 KVP). Requires 1/16 inch lead or equivalent and must extend up to a height of 7 feet from the floor.
6
Q
Secondary protective barriers
A
Areas exposed to scattered and leakage radiation only. Require 1/32 inch lead or equivalent. Plaster or concrete ca. Serve as a secondary barrier.
7
Q
Secondary protective barrier - control booth
A
X-rays must scatter at least 2 times before hitting the control booth
8
Q
Secondary protective barrier - observation window
A
Obtained in lead equivalencies from .3-2mm. Average glass lead window consists of 1.5 mm lead.
9
Q
Secondary protective barrier - miscellaneous protection
A
Exposure cord short enough so exposure is only possible when radiographer in the booth. Walls must be 7feet high and mounted to the floor. Door should be interlocked with control panel so it cannot be opened.
10
Q
Protective tube housing
A
X-ray tube enclosed by a lead metal covering serves to reduce leakage radiation to an assigned safe level. Required shielding being approximately 1.5mm lead.
11
Q
Leakage from X-ray tube housing should not exceed
A
100mR/hr at 3 feet or 1 meter.
12
Q
During radiography and fluoroscopy procedures at 1 meter from the patient, beam intensity is reduced by a factor or 1000 or .1% the original beam intensity.
A
Yup.
13
Q
Barrier thickness depends on the distance between radiation source and barrier.
A
The greater the distance between radiation source and barrier the less lead needed for the barrier.
14
Q
Barrier thickness factors
A
Time of occupancy
Workload - radiation capacity - max KVP/mAs
Use - % of time beam is on
15
Q
Time of occupancy factor
A
The amount of time a hospital area is occupied by people
16
Q
Occupancy factors - 2 types
A
Controlled
Uncontrolled
17
Q
Controlled area
A
Area occupied by radiation personnel
Occupancy factor of 1
Meaning radiation workers are always present
18
Q
Uncontrolled area
A
Area occupied by the general public
Designated as full, partial or occasional
19
Q
Uncontrolled occupancy
A
Stairways, unattended elevators, outside areas. Factor depends on use of the area.
Hallways - factor of 1/4
Unattended elevators - 1/16
20
Q
Controlled area require barriers to reduce the exposure rate to less than 100 mrem/week
A
Yup
21
Q
Uncontrolled area
A
Require barriers to reduce exposure rate to less than 10mrem/week.
Uncontrolled walls have 1/10 value layer of lead compared to controlled wall.
22
Q
Workload depends on
A
Radiation level activity in that room, the more exams, the thicker the barrier.
Accounts for weekly average tube current and operating time, measured in milliampere minutes/week.
23
Q
Workload for small office
A
Less than 100 mA-min/week
24
Workload for hospital
500 mA-min/week
25
Use factor
Percentage of time X-ray beam is energized and directed to a particular wall.
26
NCRP recommendations for use factor
Primary wall barriers and floor barriers - use factor of 1
Non primary wall -use factor of 1/4
Secondary barriers - user factor of 1
27
Secondary barrier
Struck only by scatter radiation from patient.
28
The primary barrier is located
Any wall which the primary beam is directed
| Minimum 1/16 of an inch of lead equivalent
29
Secondary barrier is located
On any wall against which only scatter or leakage impacts (control console)
Minimum 1/32 of an inch lead equivalent.
30
Barriers do not have to be lead
But they must absorb X-rays as well as the lead equivalent. Examples are concrete, steel, brick, drywall, wood, glass, even air.
31
Barrier height must be at least
7 feet high.
32
Control console walls and leaded glass are
Secondary barriers and should never receive the primary beam
33
With modern X-ray rooms that have flexible mobile buckeys and image receptors
Every wall becomes a potential primary barrier
34
Why lead?
All matter attenuated X-ray energy
Lead is very efficient
High atomic number of 82 - 82 electrons per atom
X-ray interacts with electrons.
More electrons in the path of an X-ray means an increased probability of interaction.
35
Why lead 2?
```
Plentiful
Cheap
Low melting temperature
Malleable
Inert
```
36
There's nothing magical about lead...
Lead does not attract X-rays, electrons just get in the way of X-rays, absorbing energy.
37
Leaded sterile gloves
Lead protects from scatter radiation only, does not protect hands from primary X-ray.
38
If you can see phalanges on the C-arm monitor than the fingers
Are being penetrated
39
Leaded glasses
Prevent X-ray energy to the lens of the eye, reduce cataract formation
40
Lead gloves
To be used when required to place hands in or near the primary beam
41
Thyroid collar
Protect Thyroid tissue amongst the more radio sensitive tissues of the body
42
Leaded barriers see through barrier
Leaded glass
43
Leaded barriers - solid barriers
Come in mobile or fixed barriers
44
Lead underwear
Protect reproductive organs for both male and female.
Keep radiation IN - brachytherapy of prostate.
45
Protective garments contain
Lead due to high atomic number and absorbs most scattered photons.
46
Shields evaluated by half value layers (HVLs) - which refers to
Lead thickness that will reduce the intensity of radiation to 50%
47
Lead aprons are lead impregnated with vinyl or rubber, their thickness
Should be .25, .5 and 1 mm lead equivalencies.
| When facing the primary X-ray beam approximately 3/4 of the body's active bone marrow is covered.
48
Maternity aprons need to be a minimum
.5mm lead equivalent.
49
Lead gloves
Used for personnel when hands are in the beam.
Minimum lead equivalency of .25mm
50
Thyroid shield
Primarily used during fluoroscopy
Minimum lead equivalency of .5mm.
51
Mobile exams
Effective communication and assessment necessary, clear and protect all persons in area, announce X-ray loud/clear.
Distance oneself from patient and remember inverse square law.
52
A mobile unit switch should allow the technologist to obtain a distance of
At least 6 feet from the patient.
53
Fluoroscopic exams
Lead apron should be at least .5 mm if lead equivalent. The primary source of exposure is the patient.
54
The highest energy scatter occurs at a
90 degree angle to the incident beam.
55
Bucky slot cover - fluoroscopic exams
Located at gonad level, lead shield must cover this slot, strips of lead rubber form a drape between the patient and radiologist (absorbs a majority of the scatter).
56
Deadman switch - fluoroscopic exams
Fluoroscopic exposure switch, usually a foot pedal or hand switch only emits radiation when constant pressure is applied
57
Source to table top distance for mobile fluoroscopic exams must be a minimum
Of 12 inches for mobile fluoro units.
58
Source to tabletop distance for fixed fluoroscopic units is
15 inches
59
Total filtration of the fluoroscopic equipment must be at least
2.5mm aluminum equivalent.
60
Image intensifier component (primary barrier) lead equivalent must be
2mm
61
Cumulative timing device
Creates audible signal after 5 minutes of fluoro
| Timer resets after 5 minutes and resets after each exam.
62
Fluoroscopic X-ray intensity at tabletop must not exceed
10R/min
63
High level control fluoroscopy (HLCF) must not exceed
5R/min
64
The radiologist should be trained to use intermittent or pulsed fluoroscopy
And should also Collimate to the area of interest only
65
Inverse square law
The intensity of radiation at a given distance from a source is inversely proportional to the square of the distance of the object from the source.
66
Inverse square law (2)
As distance from source goes down, your exposure goes up
As distance from source goes up your exposure goes down
I1/I2 = D2^2/D1^2
67
When involuntary motion is a factor
Use short exposure time and a high mA
Use positioning aides (sponges, sandbags, tape, etc)
Explain why immobilization is being used!
68
Holding of patients
Radiographer is last choice
- wear a lead apron, thyroid shield, gloves, glasses, etc
NO DH - designated holder
69
When X-ray enters matter one of three things will happen
X-ray energy will pass through without interaction
X-ray energy will be absorbed by matter
X-ray energy will be redirected due to interaction
70
An X-ray is a shadow image - a shadow is formed by
Energy absorbed, and energy passing through and around
71
Radiations to consider
```
Primary
Secondary
Scatter
Remnant
Leakage
Off-focus
```
72
Primary radiation is sometimes referred to as
The useful beam.
Radiation produced in the X-ray tube
73
The focal spot is the "s" in the term
"SID"
74
Secondary radiation
X-ray produced at a point other than the focal spot of the anode, produced in the patient by classical/coherent interactions and photoelectric interactions
75
Scatter
Redirected primary - produced in the tube
76
Secondary
A brand new X-ray produced in patient
77
Scatter radiation
Redirected primary beam radiation due to interaction with matter (Compton, collision)
The patient is the source of scatter.
78
Effects of scatter
Increase in patient dose, tech dose.
Degradation of image quality - unwanted density
Decrease in image contrast - useless grays
79
Remnant radiation
Portion of primary beam that survives the trip through the patient, passes through without interraction, good for the image formation.
80
How can an X-ray pass through a solid object?
Bohr atom theory
- mini solar system
- mostly empty space
- X-ray weaves through matter, sometimes without hitting anything
81
Off focus radiation
X-ray produces at points of the anode other than the true/focal spot
82
2 sets of lead shutters
A high set and a low set, dramatically decrease off focus radiation
83
Leakage radiation
X-ray that escapes the tube housing at a point other than the tube window.
Must be less than 100mR/hr at 1 meter
84
Radiation survey equipment is used to detect and measure ionizing radiation, two types:
Geiger-Muller aka Geiger counter - electrical conduction of inert gas within the detection chamber
Ionization Chamber Survey Meter aka cutie pie - ionization of air within the detection chamber
85
Occupational Exposure Annual Dose Limits - whole body
5 rem (50mSv)
86
Occupational Exposure Annual Dose Limits - lens of eye
15 rem (150 mSv)
87
Occupational Exposure Annual Dose Limits - skin/extremities
50 rem (500 mSv)
88
Occupational Exposure Annual Dose Limits - Whole body cumulative
Age x 1rem (age x 10 mSv)
89
Occupational Exposure Annual Dose Limits - Fetus (nine month)
.5 rem (5mSv)
90
Occupational Exposure Annual Dose Limits - Fetus (one month)
.05 rem (.5 mSv)
91
Occupational Exposure Annual Dose Limits - Student less than 18 years of age
.1 rem (1mSv)
92
Annual dose limits public exposure - infrequent exposure
.5 rem (5mSv)
93
Annual dose limit public exposure - frequent exposure
.1 rem (1 mSv)
94
ALARA
```
A - as
L - low
A - as
R - reasonably
A - achievable
```
95
As patient exposure goes up...
Image quality goes up
96
X-ray is...
Bundles of pure energy in transit through space, undetectable to human senses.
No mass, no charge, speed of light, waveform movement
97
Characteristics of X-ray
Energy in transit through space (electromagnetic energy). Created on demand, polyenergetic, divergent, Isotropic, interacts with matter at the level of the atom.
98
X-ray begins and ends with
Electrons
99
The X-ray technologist controls
When X-rays are created (exposure switch)
The strength of X-rays created (KVP adjustment)
How many X-rays are created (mAs adjustment)
For how long the X-rays are crated (exposure timer)
100
3 things for X-ray production
Source of free electrons (thermionic emission of the filament)
Acceleration of free electrons (application of KV)
Abrupt halting of high speed electrons (tungsten target)
101
Reducing patient dose can be done by adjusting the following
```
Filtration
Collimation
Shielding
High KVP/low mAs techniques
Beam projection
Motion control (voluntary/involuntary)
Get it right the first time (positioning/technique)
```
102
Why filter the X-ray beam?
To selectively remove weaker X-rays that cannot penetrate patient and cannot contribute to image formation.
103
Beam filtration is rated in
Aluminum equivalency - anything between the focal spot and the patient (glass, oil, plastic, mirror, air, etc)
104
Federal guidelines require a minimum filtration of at least
2.5 mm Al/eq (aluminum equivalency).
105
Inherent filtration
Built into tube and housing
106
Added filtration
Between the housing and the patient
107
Total filtration
Inherent + added
108
Collimation
Controlling the size and shape of the beam, minimizing the amount of tissue irradiated.
109
Shielding
All persons all the time, especially radiation sensitive tissues.
110
Blood is the most sensitive body system.
Yup.
111
Technical factors that are within the techs control
```
KVP selection
MAs selection
Exposure time
Digital speed class
Grid selection
```
112
Traditionally KVP has been used to control
Contrast
This is the dominant control factor with film/screen imaging
113
With digital imaging
KVP is less critical to image contrast.
KVP can be increased while maintaining high contrast.
114
As KVP increases, MAS decreases
To maintain image density (15%rule)
115
MAs is the number of X-rays in beam
As mAs does down, patient dose goes down
116
Fewer X-rays =
Less dose
117
KVP is the photon strength in the beam
As KVP goes up patient does goes down
As KVP increases average X-ray strength increases.
118
Stronger X-rays are more likely to pass through the patient, an X-ray that passes through
Does not deposit energy into tissue
119
With digital imaging, KVP no longer
Controls contrast but is still needed for penetration of part.
120
CR speed class controls
Size and speed of the laser
121
DR speed class controls
Sampling rate of data
122
As speed goes down, patient dose
Goes up
123
Slow imaging speed
Requires an increase in mAs - increased dose
124
Use of a grid
Requires an increase in mAs - increased dose
125
Low KVP/high mAs
To establish high contrast/to minimize quantum mottle
Requires an increase in mAs - increased dose
126
Increased SID
Requires an increase in mAs
Though not necessarily increased patient dose.
127
Benefits of a higher ratio grid
More scatter absorbed
| Higher contrast
128
Benefits of a lower ratio grid or no grid at all
Lower mAs can be used - lower patient dose
| Greater latitude - fewer grid errors/repeats
129
Drawbacks of higher ratio grid
More mAs required - higher patient dose
Lower latitude -more grid errors/repeats
130
Drawbacks of lower ratio or no grid
Less scatter absorbed
Loss of contrast - image can be very gray
131
ESE
Entrance skin exposure
132
AP vs PA projection
Radiation sensitive tissues tend to be anterior
- thyroid
- lens of eye
- gonads
- intestinal linings
133
Maximum dose occurs where the
Beam enters the body
Attenuation results in decreased exposure
134
Attenuation
Partial absorption and partial transmission of X-ray energy as it passes through matter
135
Motion control
To minimize the risk of repeat exposure.
136
Voluntary motion
Within control of the patient - wiggling, talking, breathing.
Best controlled by clear instruction.
137
Involuntary motion
Not within the patients control - heartbeat, peristalsis, pulsation of vessels.
Best controlled by short exposure time.
Immobilization - as required.
138
Patient immobilization
Use positioning aids (sandbags, sponges, straps, tape, etc)
| Explain why immobilization is required! - especially to parents when a child is the patient
139
Radiographs can only be performed on the
Order of a physician or licensed practitioner.
Evaluate and question orders as needed, be the expert.
140
Understanding which tissues are sensitive is important to
Take special care to protect those tissues.
141
The least mature and least specialized cells, high reproductive activity, and the longest mitotic phase as the most
Radiation sensitive cells
142
Bergonie and Tribondeau discovered that
Discovered that radio sensitivity is a function of the metabolic state of the cell receiving the exposure.
143
The law of Bergonie and Tribondeau states
The radio sensitivity of cells is directly proportional to the reproductive activity and inversely proportional to their degree of differentiation
144
Stem cells are
Undifferentiated cells and are not yet specialized, these tend to be very sensitive to radiation.
145
Lymphocytes are the most
Radiation sensitive tissue of the body.
146
The hematopoietic system is the most
Radiation sensitive of all body systems.
147
Radiation impact upon the circulatory system
Reduce the body's ability to protect and heal itself,
decrease the number of blood cells in the bone marrow,
reduce the number of cells in circulation
148
Radiation primarily affects
Immature erythrocytes
- red bone marrow
- stem cells for the hematopoietic system
149
Once mature, erythrocytes are
Much less radio sensitive
150
Erythrocytes
Red blood cells. - carry gasses within the blood
151
Thrombocytes
Lifespan of only 30 days
Initiate clotting and prevent bleeding
AKA platelets
152
Epi/endothelial tissue
Cells found in/on body, in lining of intestines, respiratory tract, pulmonary alveoli, lining of blood and lymphatic vessels.
Single cell thick, transport of materials across linings - short life span
153
Because epi/endothelial tissue/cells are constantly regenerating
They are considered to be highly radio sensitive
154
Crypt cells
Stem cells to produce spit helical and endothelial tissues
155
Spermatogonia
Male genetic cells, both mature and immature exist within the male testes.
156
Oocytes - ova
Female genetic cells that exist both maturely and immaturely in the female ovary. Genetic damage can occur is an irradiated ova is fertilized.
157
Embryo-fetus nervous tissue
More radio sensitive than adult nerve cells.
158
Embryo nervous tissue is most sensitive
8-15 weeks after gestation.
A lower risk exists until 25 weeks.
159
Radioinsensitive cells
```
Muscle
Nerve
Bone
Cartilage
Tendons
Ligaments
```
160
Radium watch dial painters
1920-30's
161
Uranium miners, Navajo
1950-60's
162
Early medical radiation workers
1896-1910's
163
Thorotrast patients
1925-1945
164
Infant thymus gland patients
1940-50's
165
Marshall Islanders
1954
166
Hiroshima/Nagasaki
1945
167
Chernobyl
1986
168
Fukushima daiicchi
2011
169
Natural radiation
Aka background
Cosmic
Terrestrial
Internal
170
Man made radiation
Artificial
CT scanning
Nuclear medicine
Fluoro/X-ray
Consumer products, occupational/industrial
171
Electromagnetic interaction
Charged particles influencing atoms/molecules
172
The simplest way to ionize matter is to
Remove an electron
173
In the X-ray room there are two sources of ionizing radiation to consider
The X-ray tube - primary created on demand
The patient - scatter production
174
We protect ourselves and others from
Scatter
175
When X-ray enters matter one of three things will happen
Pass through without interraction
Will be absorbed by matter
Will be redirected due to interaction
176
What is scatter
Redirected primary beam radiation caused primarily by Compton interactions with tissue proceeding isotropically, carries NO anatomical info.
177
Scatter is useless density into the image/receptor and also known as
"Veil of gray"
178
Scatter variables - scatter produced dependent on...
X-ray beam field size - as area of tissue irradiated^ scatter^
Thickness of tissue irradiated - as thickness^ scatter^
Composition of tissue irradiated - lower density tissue scatters more and absorbs less
Kiliovoltage - as KVP^, scatter^
179
Our job as imaging techs is to
Minimize the production of scatter
Minimize the impact of scatter on the radiograph
Using the tools of collimator and grid
180
The primary tools used for minimizing scatter are
The collimator - minimize production of scatter
The Grid - minimize the impact of scatter
181
Image gently - the society for pediatric radiology
Their goal:
To raise awareness in the imaging community of the need to adjust radiation dose when imaging children
182
People are not one size fits all - X-ray technique should not be either
Use size appropriate settings for children and adults
183
Image wisely is a combined effort of the
ACR - American college of radiology
PSNA - radiologic society of North America
AAPM - American association of physicists in medicine
ASRT - America society of radiologic technologist
184
Image wisely goal
To address concerns about the surge of public exposure to ionizing radiation from medical imaging. To lower the amount of radiation used in medically necessary imaging studies, and to eliminate unnecessary procedures.
185
Repeat analysis
What must be recorded and analyzed is which exam, why, who...
Not meant to be a witch hunt, the goal is patient safety and to minimize patient dose by minimizing repeats
186
Rad techs are not just button pushers, they consider
Patient size
Patient condition
Patient pathology
Patient cooperation
All of these should be considered when imaging and should adjust setting to accommodate these factors.
187
The dose creep phenomenon
Dose creep is when overexposure is purposefully done to obtain an optimal image in digital. Only under exposing will not provide an optimal image so why not overexposed ever time?
188
We can fight dose creep by...
Understanding our systems exposure indicators and continuously evaluate exposure indicator values.
Use a high KVP and low mAs - as long as quantum mottle is under control.
