Radiation Safety Training

for Fluoroscopy in Research

Radiation Safety OfficeIndiana University Purdue University Indianapolis

and Associated Facilities

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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

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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

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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

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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)

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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

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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)

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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

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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

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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

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Ring badges should be worn by operators whose hands are very near the primary beam

Personnel Monitoring

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Minimizing Operator Dose

↑ Subject dose ↑ Operator Dose

↑ Clarity or detail of image ↑ Operator Dose

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Subject Dose Measurement

Indicators of Dose Fluoroscopy time DAP (Dose Area Product) Cumulative dose at IRP

LimitationsField sizesMovement of x-ray tube

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Cataract originating in the posterior pole ofthe lens of an interventionalist, consistentwith radiation-induced cataract

Biological Effects of Radiation to Operator

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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

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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

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Lower Dose

INCREASE QUALITY

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Decrease Radiation Field Size

Collimate to the smallest practical field size Reduces exposure to subject Reduces scatter to operator Improves image

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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

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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

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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

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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

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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

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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")

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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

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Maximize distance between tube & subject

Minimize distance between subject and II

Subject Distances to Tube and II

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“Danger” Zone betweenX-ray Tube and Subject

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“Danger Zone” Analogy

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Reducing Exposures“TDS”

Time

Distance

Shielding

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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.

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Reducing ExposuresDistance

Radiation follows the “inverse square law”

8 R/min 32 R/min2 R/min

½ meter

1 meter

2 meters

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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

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Reducing ExposuresShielding

Portable/pull-down shields may be utilized

Pb drapes on table and image intensifier

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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

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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

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Radiation Safety Office

Clinical Building – Room 159

274-4797

After hours pager 312-1519