Radiation Safety Training
for Fluoroscopy in Research
Radiation Safety OfficeIndiana University Purdue University Indianapolis
and Associated Facilities
2
Radiation Safety Concerns
in Fluoroscopy Monitor radiation exposure of operators
Keep exposures “as low as reasonably achievable” (ALARA)
Minimize deleterious effects to subjects from radiation exposure
3
Radiation Quantities & Units
Traditional Units
SI Units
Exposure(Air Kerma)
R or mR c/kg
Absorbed Dose
rad or mrad Gy or mGy
Dose Equivalent
rem or mrem Sv or mSv
4
Conversions - Traditional to SI Units 1 R = 2.58 x 10-4 c/kg 1 rad = 0.01 Gy 1 rem = 0.01 Sv
Conversions - SI to Traditional Units 1 c/kg = 3876 R 1 Gy = 100 rad 1 Sv = 100 rem
1 R ≈ 1 rad ≈ 1 rem 1 Gy ≈ 1 Sv
Radiation Quantities & Units
5
Sources of Ionizing Radiation
Natural Sources• Radon gas• Uranium and Thorium in
rock and stone• Galaxy & Sun
Man-Made Sources• Medical x-rays• Nuclear medicine studies• Consumer products
(e.g., smoke detectors, exit signs)
6
Sources of Radiation Exposure to the US Population
Radon54%
Cosmic8%
Terrestrial8%
Internal11%
Medical X-rays11%
Nuclear Medicine4%
Other1%
Consumer Products3%
Average Dose Equivalent~360 mrem/yr
Radon54%
Cosmic8%
Terrestrial8%
Internal11%
Medical X-rays11%
Nuclear Medicine4%
Other1%
Consumer Products3%
Naturally Occurring
7
Dose Comparisons
“Typical” Doses
Flight from Los Angeles to London 5 mrem (.05 mSv)
Chest X-Ray 10 mrem (0.1 mSv)
Average annual background dose 360 mrem (3.6 mSv)
“Comparative” Dose
Skin erythema (reddening) ~300,000 mrad (~3000 mGy)
8
Radiation Dose Limits Occupational limits
Effective dose equivalent limit - 5,000 mrem/yr
Skin, organs, or extremities - 50,000 mrem/yr
Lens of the eye - 15,000 mrem/yr
“Declared pregnant woman” - 500 mrem to embryo/fetus
Member of the public - 100 mrem/yr
9
ALARA
Location Limit(mrem/yr)
ALARA I(mrem/qtr)
ALARA II(mrem/qtr)
Whole body 5000 125 375
Lens of the Eye 15,000 375 1125
Extremities/Skin 50,000 1250 3750
10
Personnel Monitoring Two body badges
One badge should be worn under all leaded apparel.
Second badge should be worn at the collar level outside all leaded apparel.
DO NOT INTERCHANGE THESE BADGES
11
Ring badges should be worn by operators whose hands are very near the primary beam
Personnel Monitoring
12
Minimizing Operator Dose
↑ Subject dose ↑ Operator Dose
↑ Clarity or detail of image ↑ Operator Dose
13
Subject Dose Measurement
Indicators of Dose Fluoroscopy time DAP (Dose Area Product) Cumulative dose at IRP
LimitationsField sizesMovement of x-ray tube
14
Cataract originating in the posterior pole ofthe lens of an interventionalist, consistentwith radiation-induced cataract
Biological Effects of Radiation to Operator
15
Biological Effects of Radiation to Subject
Skin injury to animal
Can range from skin reddening to tissue necrosis
May take weeks to months for skin problems to occur
16
Correlation of Dose Operator and Subject
With the exception of magnification, “scatter” radiation dose to operator is affected by the same parameters as the radiation dose to the subject
Low dose to subject = Less scatter = Low dose to operator
17
Lower Dose
INCREASE QUALITY
18
Decrease Radiation Field Size
Collimate to the smallest practical field size Reduces exposure to subject Reduces scatter to operator Improves image
19
Increase Tube Potential (kVp)
Lowers scatter since fewer photons will be needed to penetrate the subject
In automatic mode, the mA decreases as the kVp increases
Therefore, higher kVp generally results in a lower skin dose to the subject and less scatter to the operator
20
Subject Thickness ↑ Thickness ↑ Photons to get to II
Large subjects and oblique beam angles may result in significantly higher skin doses and scatter
May not be negotiable
21
Thickness vs Skin Entrance Exposure Rate
1.47
2.74
4.2
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
0 2 4 6 8 10 12
Thickness of Subject
Exp
. R
ate
(R
/min
)
Exp. Rate
22
Use Magnification Sparingly Machine automatically reduces the field
size Higher “Mag” modes result in higher
doses to smaller areas of the skin May negatively affect your research
results Instead, reduce field size to the extent
practical when in “normal” mode
23
Lower Pulse Rate Lower pulse rates result in lower
exposure to the subject and less scatter to the operator
Dynamic image quality will be reduced (image may appear “jerky”)
Operate in “pulse rate” mode whenever possible
24
Exposure RateAffected by Magnification and Pulse Rate
2.09
4
2.68
5.23
3.15
6.24
0
1
2
3
4
5
6
7
7.5 15
Pulse Rate (Pulses/sec)
Exp
. Rat
e (R
/min
)
Normal (9")
Mag1 (7")
Mag2 (5")
25
Minimize High Dose Rate Mode (Cine)
A high dose rate mode (“cine”) is used to capture digital images
20 times the dose rate from standard fluoroscopy
A minimum number of these runs should be used consistent with obtaining adequate information
26
Maximize distance between tube & subject
Minimize distance between subject and II
Subject Distances to Tube and II
27
“Danger” Zone betweenX-ray Tube and Subject
28
“Danger Zone” Analogy
29
Reducing Exposures“TDS”
Time
Distance
Shielding
30
Reducing ExposuresTime
Minimize fluoro time to reduce subject dose and scatter dose to operator
Use “image hold” capabilities to reduce need for additional fluoro time
Personnel should not be in the room unless their presence is necessary to the procedure.
31
Reducing ExposuresDistance
Radiation follows the “inverse square law”
8 R/min 32 R/min2 R/min
½ meter
1 meter
2 meters
32
Reducing ExposuresShielding
Pb aprons (at least 0.5 mm Pb equivalent) should be worn by all personnel involved in fluoro/cine procedures
Thyroid collars and Pb glasses may also be recommended or required
33
Reducing ExposuresShielding
Portable/pull-down shields may be utilized
Pb drapes on table and image intensifier
34
Dose Reduction Summary Use pulsed fluoroscopy or other low-dose-
rate modes of operation Keep tube current low and tube potential
high Optimum kVp – below gives better contrast
at expense of dose increase and above decreases subject dose and image quality
Use heavy beam filtration to increase kVp Use “image hold” to avoid repetitive
exposure Use magnification modes sparingly
35
Do not remove devices designed to maintain adequate distance between x-ray tube & subject (beam separator device)
Collimate to the smallest reasonable field size Utilize dose monitoring equipment (e.g.,
radiation badge) Keep x-ray tube as far from subject as possible
and image intensifier as close to subject as possible
Avoid prolonged exposures over the same skin area, especially through thick body masses
Dose Reduction Summary
36
Radiation Safety Office
Clinical Building – Room 159
274-4797
After hours pager 312-1519