Protection of Patient Flashcards
1
Q
What are common goals of all radiologic equiptment?
A
- Optimize the quality of the image
- reduce radiation exposure to patients
2
Q
Who are protected when radiographic equipment is used safely?
A
Patients and all personnel
3
Q
What are the two required features for every diagnostic imaging system?
A
- protective tube housing
- correctly functioning control panel
4
Q
What other components of diagnostic systems have been designed to reduce patient dose?
A
Radiographic exam tables and other devices
5
Q
What material is required of tube housing?
A
Needs to be lead lined
6
Q
What does a lead-line tube housing protect patients and personnel from?
A
Off focus or leakage radiation
7
Q
How do lead lined tube housing reduce off-focus and leakage radiation?
A
Restrict the emission of x-rays to the area of the primary beam
8
Q
What are the leakage requirements for tube housing?
A
It needs to be constructed so that any leakage measured 1 m from the x-ray source does not exceed 0.88 mGy/hr
9
Q
Where does a control panel/console need to be located?
A
Behind a suitable protective barrier
10
Q
What are the features of the suitable protective barrier?
A
Has a radiation-absorbent window that permits observation of the patient during a procedure
11
Q
What features are required of a control panel?
A
Must indicate the conditions of exposure and provide a positive indication when the tube is energized
12
Q
How are exposure conditions represented on a console?
A
Through visible mA and kVp readouts
13
Q
What happens on the console when the exposure begins?
A
A tone is emitted and then stops when it terminates
14
Q
What does the audible sound indicate?
A
That the x-ray tube is energized and ionizing radiation is being emitted
15
Q
What is the main feature of a radiographic examination table?
A
It needs to be strong enough to support patient whose weight is in excess of 400 lbs
16
Q
What feature do exam table usually have?
A
A floating tabletop that makes it easier to maneuver a patient
17
Q
What needs to remain uniform on an exam table?
A
Thickness
18
Q
What is an important function of the material of a exam table?
A
Needs to be radiolucent so that it only absorbs a minimum amount of radiation
19
Q
What material are exam tables usually made of?
A
Carbon fiber
20
Q
What are two additional features of an exam table?
A
Have a grid and slot cover
21
Q
What does the SID indicator provide?
A
A way to measure the distance from the anode focal spot is maintained
22
Q
What are used to measure SID?
A
Lasers or tape measures
23
Q
At what range are distance and centering indicator accurate?
A
Within 2% and 1% of the SID, respectively
24
Q
What is a standard rule for the primary beam?
A
That it should be not larger than the size of the IR being used
25
What is light-localizing variable-aperture rectangular collimator used for?
Its used to adjust the size of the x-ray beam automatically or manually
26
What is the predominant x-ray beam limitation device?
Collimator
27
What is the purpose of a collimator?
To reduce scatter radiation
28
How are light-localizing variable-aperture rectangular collimators constructed?
With 2 sets of lead shutters, a light source and a mirror
29
What do the 1st shutter placed close to the window do?
Reduce off-focus radiation
30
What are the minimum skin sparing distance for fixed machines?
15 cm
31
What is the minimum skin sparing distance for mobile machines?
30 cm
32
What is luminance?
Brightness of the light source
33
What are the benefits of restricting x-ray field size to only include area of interest?
- Significant Reduction in patient dose, because Less scatter is produced
- Improves overall quality of the image
34
What is positive beam limitation?
When the beam of light is automatically adjusted to the size of the IR being used
35
What must the radiographer ensure when PBL is in use?
That the collimation is accurate and adjusted to the size of the part and no bigger than the IR
36
What are radiographic cones?
Circular metal tubes that attach to the x-ray tube housing and limit the beam to a predetermined size and shape
37
What are the two types of cones?
Flared metal tubes and straight cylinders
38
What types of cones are used in dental radiography?
Beam-defining cones
39
What is another type of beam limiting device?
Aperture diaphragm
40
What is an aperture diaphragm?
A flat piece of lead with a hole in it of a designated size and shape
41
Where is an aperture diaphragm placed?
Directly below the window of the x-ray tube to confine the primary beam to the given size of the hole
42
What do sizes of aperture diaphragms relate to?
Each size IR and SID
43
What is the purpose of beam filtration?
To remove low energy photons
44
How does beam filtration effect patient dose?
It lowers patient dose, by hardening the beam and making it more penetrating
45
How is the energy of the beam affected by filtration?
The effective energy of the beam is increased
46
What are the 3 types of filtration?
- Inherent
- Added
- Total
47
How do beam filters work?
They absorb the low energy photons and permit high energy photons to pass through
48
What is the minimum total filtration required when more than 70 kVp is used?
2.5 mm Al equivalent
49
What is the minimum total filtration required when 50-70 kVp is used?
1.5 mm Al equivalent
50
What is the minimum total filtration required when less than 50 kVp is used?
0.5 Al equivalent
51
How is filtration most widely expressed?
In aluminum or its equivalent
52
What is the required Al eq for inherent filtration?
0.5 mm Al eq - glass and oil
1.0 mm Al eq - collimator mirrors
53
What is the required Al eq for added filtration?
1.0 Al (thin sheets of aluminum
54
What is the Al equivalent for total filtration?
2.5 Al eq
55
What is the minimum Al eq filtration for mobile diagnostic and fluoroscopic equipment?
2.5 mm Al eq
56
What is half value layer?
The thickness of a designated absorbed required to decrease the intensity of the primary beam by 50% of its initial value
57
Why must the HVL be measured?
To verify that the x-ray beam is adequately filtered
58
Who should obtain the HVL measurement?
A radiologic physicist
59
When should a radiologic physicist obtain the HVL?
At least once a year, after an x-ray tube is replaced or when the housing or collimator have been repaired
60
How is HVL expressed?
In millimeters of aluminum
61
What does HVL measure specifically?
Beam quality or effective energy of the x-ray beam
62
What is the range if minimum requireed HVL for kVp's between 30-120?
From 0.3 to 3.2, with 70 kVp requiring 1.5 mm Al
63
What are compensating filters made up of?
Aluminum, lead acrylic or other suitable material
64
What are compensating filters used for?
To accomplish dose reduction and uniform imaging of body parts that vary considerably in thickness/tissue composition
65
How do compensating filters work?
They partially attenuate x-rays directed towards the thinner areas and allow more x-rays to strike the thicker areas
66
What are the two types of compensating filters?
- wedge filter
- trough, or bilateral wedge filter
67
What procedures are wedge filters usually used on?
Feet
68
What procedures are trough or bilateral wedge filters usually used on?
Chests
69
What are the two required radiation exposure characteristics?
- exposure reproducibility
- exposure linearity
70
What does exposure reproducibility provide?
Consistency in output radiation intensity for identical generator settings between individuals
71
What variance is accepted for exposure reproducibility?
A variance of 5% or less
72
How can reproducibility be verified?
By using the same technical exposure factors to make a series of repeated exposures and then observing with a calibrated ion chamber and seeing how the intensity varies
73
What does exposure linearity provide?
Consistency in output radiation intensity at selected kVp settings when generator settings are changed from on Mas and time combination to another
74
What is linearity?
The ratio of the differences in mSv/mAs or mR/mAs between two successive generator stations to the sum of these mSv/mAs or mR/mAs values
75
What does the linearity ratio need to be?
Less that 0.1
76
What is the variation percent when settings are changed from one mA to a neighboring mA station?
0.1
77
What is AEC?
An x-ray termination device that ends the radiation when a predetermined amount of radiation is received by an arrangement of sensors
78
What does AEC produce?
An acceptable image while limiting radiation exposure to a patient
79
What is a safety feature that is part of AEC?
A backup timer
80
What is phototiming?
Old terminology referring to photomultiplier tubes
81
What do today's AEC systems utilize?
Ionization chambers
82
What is a radiographic grid?
A device made of parallel radiopaque strips alternately separated with low-attenuation strips of aluminum, plastic or wood
83
Where is a radiographic grid placed?
Between the patient and the IR
84
What do radiographic grids do?
Remove scattered x-ray photons that emerge from the patient before it can reach the IR and decrease image quality
85
What impact do radiographic grids have on image quality?
They increase radiographic contrast and visibility of detail
86
What size parts require the use of radiographic grids?
Parts that are 10 cm or more
87
Why does patient dose increase when using grids?
Because you need to adjust the exposure 2x for every 4cm over the average and the beam needs to be able to penetrate through the grid as well
88
What is grid ratio?
Refers to the height of the lead strips divided by the distance between each strip
89
What is the minimum SSD that should be used for mobile units?
Minimum SSD is at least 30 cm (12 inches)
90
What is the distance generally used for mobile radiography?
100 cm (40 inches) or 120 cm (48 inches)
91
What effect does SSD have on patient entrance exposure?
With increased SSD there is a more uniform distribution of exposure throughout the patient
92
When are mobile units used?
For patients who can't be transported to a fixed unit
93
What are the 5 digital processed radiography imaging modes?
- Computed tomography (CT)
- Computed radiography (CR)
- Digital radiography (DR)
- Digital Fluoroscopy (DF)
- Digital Mammography (DM)
94
What are negative features of conventional radiography: analog images?
- Latent image creation and Latent imaging processing
- Time consuming processing Time
- Images often lost
95
What is a positive feature of conventional radiography: analog images?
Produced optimal-quality images
96
What has conventional radiography: analog images been replaced by?
Digital imaging
97
What is digital imaging?
Process of producing an electronic image
98
What are some limitations of digital imaging?
Inherent limitations with respect to spatial and contrast resolution due to dimensions of pixels
99
What is digital imaging subject to?
Artifacts because digital imaging are produced collectively by a matrix of elements and are subject to noise
100
How are images formed in digital imaging?
Latent image is formed by x-ray photons on a radiation detector
101
What is brightness in digital imaging?
The amount of luminance (light emission) on a display monitor
102
What are digital images composed of?
Numerical data that is stored in rows and columns called the image matrix
103
How does digital radiography work?
Image receptors convert energy into electric signals
104
What is a scintillator?
Converts x-ray energy into visible light and is made of amorphous silicone
105
What is visible light transformed into in digital radiography?
Transformed into electrical signals by charge-coupled devices (CCDs)
106
What is a photoconductor?
Converts x-ray energy directly into electrical signals which are then read by transistors.
107
What are photoconductors made of?
Amorphous selenium
108
Where can digital images be accessed?
At multiple workstations
109
What are the two types of conversion in digital imaging?
Indirect and direct conversion
110
What type of conversion does Scintillator use?
Indirect Conversion
- Scintillator > Photodiode > Thin-film transistor array > Electrical signals
- Scintillator > Charge-coupled device array > Electrical Signals
111
What type of conversion does Photoconductor use?
Direct conversion
- Photoconductor > Thin-film transistor array > Electrical signals
112
How are images generated in computed radiography (CR)?
Using photostimulable luminescence (PSL)
113
How is CR different than DR?
CR uses conventional radiographic equipment, traditional positioning and standard technical exposure factors
114
What doe CR cassettes contain?
Photostimulable phosphors
115
How are images read in CR?
A read unit scans the photostimulable phosphor plate with a laser beam and then displays it on a monitor
116
Which type of radiography has a greater KV flexibility?
CR
117
What type of radiography requires a more frequent use of grids?
CR since the imaging patients are more sensitive to scatter
118
What are the advantages of DR?
- lower doses
- greater ease of use and faster patient throughput
- immediate imaging results
- additional image manipulation
- Less overall maintenance
119
What are the disadvantages of DR?
- more costly
- not cross compatible
- single detector size
- PSP imaging plates are subject to mechanical damage and chemical oxidation
- high replacement costs
120
What are the 3 types of artifacts DR are subject to?
Image aliasing, Moire patterns and contouring defects
121
What is aliasing?
Distortion that shows up as jagged or saw-toothed lines
122
What is More patterns?
A wavy looking pattern that is overlayed on an image
123
What are contouring artifacts?
Patterns of small blocks on an otherwise smooth image
124
How does DR eliminate the need for retakes?
Improper technical selections that produce contrast or brightness issues can be manipulated after image acquisition
125
Why is there an increased repeat rate in DR?
Because of the ease of repeating images
126
How are mispositioning repeats monitored?
An independent quality control technologist at a separate monitor
127
Where does the body area need to be positioned on a CR IR?
In or near the center of the IR
128
What are fluoroscopic procedures used for?
To capture dynamic or active motion images of selected anatomic structures
129
Which type of radiography produces the greatest patient radiation exposure rate?
Fluoroscopic radiography
130
How are fluoroscopic procedures performed?
With a fluoroscopic tube inside the xray table facing up toward the surface of the table
131
What do non-digital fluoroscopic units use to amplify signals?
Image intensifier tube
132
How does an image intensifier fluoroscopic unit work?
It converts the pattern of x-rays transmitted through the patient into a corresponding and amplified visible light pattern
133
What are the benefits of image intensification fluoroscopy?
- Increased image brightness
- saving of Time for the radiologist
- patient dose Reduction
134
How is an image intensifier used?
It’s placed over the patient on this table during the examination and is used in conjunction with the tube
135
How much is the brightness of the fluoroscopic image increased compared to non-image intensified fluoroscopy?
10,000 times
136
How much mA is reduced when fluoroscopic vs intensified fluoroscopic?
Reduced from 3-5 mA to 1-1.5 mA
137
What features are present in the vast majority of image intensifier tubes?
Magnification
138
What is pulsed fluoroscopy?
Involves manual or automatic periodic activation of the tube rather than continuous activation
139
What are the benefits of pulsed and interrupted fluoroscopy?
- Significantly decreases patient dose
- Extends tube life
- Has a last-image hold feature
140
What is the standard kVp range for adult patients using non-digital fluoroscopic imaging systems?
75-110 kVp
141
What is the SSD for stationary fluoroscopes?
No less that 38 cm
142
What is the SSD for mobile fluoroscope?
No less than 30 cm
143
How should kVp be adjusted for children in non-digital fluoroscopic imaging systems?
KVp should be decreased as much as 25%
144
In what ways are exposures limited for children using fluoroscoping imaging systems?
Decreasing technical factors, maintaining SSD and minimizing height of image intensifier entrance surface above patient
145
What is the purpose of filtration in fluoroscopy?
To reduce patient skin absorbed dose from soft x-rays
146
What is the HVL for non-digital fluoroscopic image systems?
HVL of 3-4.5 mm Al acceptable when kVp ranges from 80-100
147
What is a cumulative timing device?
Measures the x-ray beam on time and sounds an alarm when the tube has been activated for 5 minutes
148
Who sets up current standard limits for entrance skin exposure rates?
Federal government
149
What is the maximum entrance skin exposure rate for non-digital fluoroscopic imaging systems?
Maximum of 88 mGya/min (10R/min)
150
What is the maximum entrance skin exposure for fluoroscopic units equipped with high level control?
Maximum of 176 mGya/min (20 R/min)
151
What is the primary protective barrier of non-digital fluoroscopic imaging systems?
2mm lead equivalent
152
What type of exposure control switch does fluoroscopic machine need to have?
A dead man type
153
What is the shape of a portable fluoroscopic unit?
C shaped with c-ray tube attached at one end and an image intensifier at the other
154
What are portable fluoroscopic units used for?
In the operating room for orthopedic procedures, cardiac imaging and interventional procedures
155
What risk do patients and personnel have with mobile fluoroscopic units?
Risk of large radiation doses from scatter
156
What must C-arm equipment operate have?
Appropriate education and training to ensure they follow safety guidelines and meet safety protocols
157
What is the source to end collimator distance required for mobile fluoroscopic units?
30 cm
158
What should the distance be for image-intensifiers in mobile fluoroscopy units?
As short as possible to reduce entrance dose
159
How should the C arm be positioned to reduce patient dose?
Under the patient since it limits scatter
160
What happens when the C arm is positive over the patient?
Scatter becomes more intense and exposure increases correspondingly
161
What system do digital fluoroscopy systems use for dose reduction?
Pulse progressive systems
162
How does the pulse progressive system work?
Utilizes a brief high intensity pulse of radiation to create an entire image on the ouput phosphor, then the image is scanned to display on the screen and is brieftly deactivated which lowers patient dose
163
What is last image hold?
The last image formed remains on the monitor so that no further radiation exposure is needed to regenerate it
164
What are interventional procedures?
Locate high contrast using small objects such as catheters, stems or electrical leads
165
What is digital subtraction angiography?
Visualization of blood vessels through the use of contrast materials
166
How does DSA work?
A reference image is taken before contrast is injected and then subsequent images are taken with contrast which allows the differences between the two images to be emphasized
167
What is roadmapping?
A static image of the vasculature may be obtained through subtraction, pre and post contrast injection
168
Where is a catheter inserted?
Into vessels or tissues
169
What is the purpose of a catheter?
- Drainage
- Biopsy
- Alteration of vascular occlusions or malformation
170
What is High-level-control fluoroscopy?
An operating mode for state of the art fluoroscopic equipment in which exposure rates are substantially higher than those normally allowed in routine procedures to see areas not usually seen in standard fluoro
171
What has the FDA recommended for procedures involving fluoroscopic radiology?
That a notation be placed in their record if skin dose is in the range of 1-2 Gy received
172
What are the procedures that involve extended fluoroscopic time?
- percutaneous transluminal angioplasty
- radio frequency cardiac catheter ablation
- vascular embolozation
- stent and filter placement
- thrombocytes and fibrinolytic procedures
- percutaneous trashepatic cholangiograpy
- Endoscopic retrograde cholangiopancreatography
- transjugular intrahepatic portosystemic shunt
- percuraneous neprostomy
- biliary Drainage
- urinary or biliary stone removal
173
What do non-radiologist physicians need when using fluoroscopic equipment?
Ongoing education and training
174
What type of approach is essential during diagnostic x-ray procedures?
Holistic approach
175
What does holistic care begin with the patient?
Effective communication between radiographers and patients
176
What are the benefits of effective communication?
- Alleviate the patient’s uneasiness
- increases the likelihood of cooperation and successful completion of the imaging procedure
177
How must radiographers limit patient’s exposure to ionizing radiation?
- employ appropriate radiation Reduction techniques
- use protective devices that minimize exposure
178
What are the 9 ways patient exposure can be substantially reduced by?
1. Effective communication
2. Use of proper body or part immobilization
3. Use of motion reduction techniques
4. Use of appropriate beam limitation techniques
5. Adequate filtration of the c-ray beam
6. Use of specific area shielding
7. Select suitable exposure factors in conjunction with computer-generated digital images
8. Use of appropriate digital image processing
9. Elimination of repeat radiographs
179
When is communication between radiographers and patient effective?
When verbal and nonverbal messages are understood as intended
180
What does effective communication encourage in patients?
Encourages a reduction in anxiety and emotional stress
181
What does effective communication enhance?
The professional image of the radiographer as a person who cares about patient well being
182
What does effective communication increase the chances of?
Successful completion of the the x-ray exam
183
What must the radiographer do if a procedure will case pain, discomfort or strange sensations?
Inform the patient of all before the procedure begins without overemphasizing them
184
What is a result of poor communication with a patient?
The need to do a repeat radiograph because of inadequate or misinterpreted instructions
185
What should patient protection begin with during a diagnostic x-ray?
Begins with clear, concise instructions
186
Why is there a need for immobilization in imaging?
To prevent the patient from moving during the image which will create blur
187
What are the consequences of blurred image?
- exams need to be repeated
- results in additional radiation exposure
188
How can patient motion be eliminated or minimized?
- proper body or part immobilization
- use of motion Reduction techniques
189
What are the two types of patient motion?
Voluntary and involuntary
190
What type of motion does adequate immobilization during exams help reduce?
Voluntary motion
191
Why is shielding needed?
To prevent radiation exposure to radio sensitive body organs
192
Which areas of the body should be shielded whenever possible?
- lens of eye
- breasts
- Reproductive organs
- thyroid glands
193
What is the first step in gonadal shielding?
Collimating
194
What types of shields are used for the eyes?
Contact type shields that are positioned directly on the patient
195
How much more exposure do female reproductive organs involving the pelvis receive than males?
3 times
196
How much exposure is reduced in females by a 1mm lead flat contact shield?
50% reduction
197
How much is exposure reduced in males with a 1mm lead contact shield?
90-95%
198
Where must gonadal shielding be placed to provide protection?
Directly over the patient’s reproductive organs
199
What should be used to guide placement of testicular or ovarian shields?
External landmarks
200
In male patients in supine position what can be used to guide shield placement over the testes?
The pubic symphysis
201
In female patients what should be used to guide shield placement of the ovaries?
Shield should be placed approximately 2.5medial to each ASIS
202
What are the types of gonadal shields?
- Flat contact shields
- shadow shields
- shaped contact shields
- clear lead shields
203
What are flat contact shields?
An uncontoured, flat lead shield that is placed over the patients gonads
204
What is a shadow shield?
A suspended shield that is placed above the beam defining system that casts a shadow on the patient directly over their gonads
205
What is a lead filter?
A type of shadow shield that has breast and gonadal shielding plates and casts a shadow on the patient
206
What are shaped contact shields?
Cuplike shields that may be held in place with a suitable carrier
207
What are the benefits of specific area shielding?
- minimize the number of potential deleterious c-ray induced mutations expressed in future generations
- reduces exposure to specific areas that are shielded
208
Why is the selection of appropriate technical factors essential in diagnostic imaging?
It ensures patients only receive a minimal dose of
209
What should high quality images have?
- sufficient brightness to display anatomic structures
- appropriate levels of subject contrast to differentiate anatomic structures
- maximum spatial resolution
- minimal distortion
210
What are the 7 considerations for technical exposure factor?
1. Mass per unit volume of tissue of the area of interest
2. Effective atomic number and electron density of tissues involved
3. Type of image receptors
4. SID
5. Type and quantity of filtration
6. Type of X-ray generator used
7. Balance of radiographic density or brightness and contrast required
211
When AEC is not used what should be used to ensure uniform selection of technical exposure factors?
Technique charts
212
What is a radiographer responsible for checking before imaging?
The technique chart and taking the patients condition into account
213
What combination of kVp and mas reduces patient dose?
Use of higher kVp and lower mAs
214
What does the use of high kVp and low mas result in?
A high energy, penetrating beam and a small,, patient dose
215
What does the use of low kVp and high MAs result in?
A low energy x-ray beam in which the majority will be absorbed by the patient
216
What is correct image post processing essential to in imaging?
Essential to produce a high quality image in which artifacts produced by the IR, software or patient are controlled
217
What does a quality control program include?
Regular monitoring and maintenance of processing and imaging display equipment
218
What does a quality control program mandate?
Full acceptance of new equipment, regular calibration and performance evaluations of existing machines and proactive and consistent image review
219
What is the air gap technique?
An alternate to using a grid to reduce scatter in that the patients is placed using an OID of 4-6 inches and an SID of 10-12 feet
220
At what kVp levels are air gap techniques more useful?
When less than 90 kVp is used
221
At what kVp are air gap techniques successful in chest X-rays?
120-140 kvp
222
How does the air gap technique work?
Many of the scattered X-rays are so low in energy that they are absorbed by the air before they reach the IR
223
Why does the SID need to be increased so much in the air gap technique?
To counteract the magnification that is caused by the increased OID
224
How does patient dose using air gap compare to tabletop and grid?
It’s higher in air gap compared to tabletop but lower than grid
225
What are the consequences of repeat images?
Additionally exposure to the patient, specifically a double dose
226
What type of repeat images should be eliminated?
Repeats resulting from the carelessness or poor judgment of the radiographer
227
When is the only time an additional image is permissible?
When it’s recommended by the radiologist for the purpose of obtaining additional diagnostic info
228
At what rate have repeat images increased?
Approximately 5% but can be as high as 17%
229
What are the main reasons for repeat images?
Positioning errors and ease of repeating
230
What are the benefits of a repeat analysis program?
Helps identify the number of repeats and reasons for producing unacceptable images with the hopes of improving
231
What are the reasons for unaccepatable images?
Patient mispositioning
Incorrect centering of the beam
Patient motion during the exposure
Incorrect collimation
Presence of external foreign bodies
Postprocessing artifacts
232
What are examples of unecessary radiologic procedures?
A chest x-ray examination automatically scheduled on admission to the hospital.
• A chest x-ray examination as part of a preemployment physical.
• Lumbar spine examinations as part of a preemployment physical.
• Chest x-ray examination or other unjustified x-ray examination as part of a routine health checkup.
• Chest x-ray examination for mass screening for tuberculosis (TB).
• Whole-body computed tomography (CT) screening.
233
What are the 3 ways the amount of radiation received can be presented?
Entrance Skin Exposure
Bone Marrow Dose
Gonadal Dose
234
Which measure of radiation received is the most reported?
Entrance skin exposure
235
How is ESE meansured?
Using thermoluminescent dosimeters to measure skin dose direcrly
236
Which measures of radiation received can only be estimated?
Bone marrow and gonadal dose
237
What is used to measure the impact of gonadal dose?
Genetically significant dose (GSD)
238
What is the estimated GSD for US?
0.20 mSv
239
What is fluoroscopic guided positions?
Practice of using fluoroscopt to determine the exact location of the central ray before taking an exposure
240
What is the ASRT's position ong FGP?
That its an unethical process and should never be used in place of appropriate positioning pre-exposure
241
The pro's of FGP are?
Its faster than having a repeat exposure
Reduces the number of repeat exposures
Provides less radiation exposure to the patient
242
What is the position of the ACR on abdominal radiologic exams of female patients?
That they don't need to be postponed or selectively schedules as long as full consideration of the clinical status of the patient is complete
243
How should radiographers determine the possibility of pregnancy?
Ask the date of the LMP or order a pregnancy test before the pelvis is irradiated
244
What are the details needed to fill out a request for radiation dose form for unknown pregnancies that were irradiated?
245
The x-ray unit or units used for the study
• The projections taken
• The number of images associated with each examination
• Each projection’s technical exposure factors (kVp, mAs, image receptor size)
• The source-to-image receptor distance (SID) for each projection
• The patient’s anteroposterior (AP) or lateral dimensions at the site of each projection
• For fluoroscopic irradiation, the approximate kVp, mA, and especially the duration
• For spot images, the number taken, the kVp and mA selected, and the approximate exposure time
246
What is the NCRP's position on risk of fetal exposure with regard to termination of pregnancy?
Risk is considered negligible with doses less than 5 cGy and exposure to the fetus by itself wouldn't be a reason to terminate
247
Who is resposible for reviewing and measuring the absorbed Eqd of a fetus?
RSO
248
What special efforts should be taken to minimize dose of known pregnant patients?
Restrictively selecting exposure factors to produce the smallest exposure needed for a useful image and precisely collimating
249
What shields should be used when imaging known pregnant people?
Lead apron or other contact shields that wrap around the whole body
250
What radiation effects are children more vulnerable to?
Both late somatic effects and genetic effects
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How should childrens dose be adjusted when compared with adults?
Doses need to be made smalled and protection methods need to be used in force
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How can moption be reduced for pediatric patients?
Using short exposure times and effective immobilization
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How can cooperation be gained with pediatric patients?
By using specially designed rooms with appropriate restraining devices, providing suitable entertainment devices and using shielding
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What factors can increase dose in children?
Repeats due to motion, improper shielding or insufficient collimation
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What is the image gently campaign?
To raise awareness about methods for lowering patient dose suring pediatric imaging exams
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What is the image wisely campaign?
To lowe the amount of radiation used in medically necessary procedures
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Which modality is considered a high radiation exposure examination?
Computed Tomography (CT)
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What are patients who receive CT at a higher risk of?
Increased associated cancer risk
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What are the two concerns that relate to patient dose in CT scanning?
Skin dose and dose distribution
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Why are skin doses smaller in CT than in diagnostic imaging?
They use smalled field sizes and use smaller images
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How is dose distribution different in CT versus radiography?
Dose is more uniformly distributed since the tube rotates around the patient
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Why is direct patient shileding not typically used in CT?
Because of the rotational nature of exposure and the tight collimation of the beam
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What is a spiral scan pitch ratio?
Ratio of the movement or advance of the patient couch during a CT scan to the x-ray beam collimator dimensions
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How is patient dose related to higher pitch?
Patient dose is reduced because the numer of x-rays produced during each rotation is spread out
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How is patient dose related to lower pitch?
Patient dose is increased
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How is patient dose optimized in CT?
Tube current modulation (longitudinal or angular), Iterative reconstruction, optimization of tube voltage and scan parameters and correct patient centering
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How is tube current modulation used to reduce patient dose?
mA varies along the longitudinal access and a lower tube current is used for thinner anatomy and higher tube current for thicker anatomy
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How is iterative reconstruction used to reduce patient dose?
CT scan data can be reconstructed, modified and reconstructed again until the image has the lowest noise possible, which allows lower doses to be used
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How is tube voltage optimization used to reduce patient dose?
Increasing voltage lowers patient dose, while all other factors increase it
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How is patient centering used to reduce patient dose?
Miscentering a patient by 2cm can lead to an increase dose of 25%, so positioning properly ensures that dose is kept low and magnification doesn't apply
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What are relevant dose parameters for CT?
CTDI (computed tomography dose index)
CTDI weighted
CTDI volume
Effective mAs
Dose length product
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What is CTDI?
A measurement of ionization that's obtained through the use of a phantom inserted into an ionization chamber which is then irradiated to represent localized dose
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What is CTDI weighted?
The average of two CTDI values, one from the pencil chamber in the middle of the phantom and the other in the periphery of the phantom
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What is CTDI volume?
Average absorbed dose within the scanned volume
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What is DLP?
The produce of CTDI volumen and irradiated scan length
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What is MDCT scanning?
Multidetector computed tomography
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What are the advanctages of MDCT?
Shorter scan durations, improved contrast-enhanced scans, longer scan ranges permitting CT, better use in trauma applications, thinner sections near isotropic imaging
