- alternative to grid use - long SID and increased OID - does NOT result in decrease in production of secondary or scattered radiation

- emitted from xray tube - limited to 100 mR/hr at 1 meter (1 mGy/hr at 1 meter)

Safety 2 Flashcards by Talar Kouchian

Filtration effect on skin and organ exposure

-reduces entrance skin exposure to pt

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Filtration effect on average beam energy

removes low energy, non diagnostic xray photons from beam

- increases the effective energy and quality of xray beam (hardening)

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Operating kVp below 50

Total filtration (inherent + added)= 
0.5 mm aluminum

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Operating kVp 50-70

Total filtration = 1.5 mm aluminum

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Operating kVp above 70

Total filtration = 2.5 mm aluminum

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Voluntary motion controlled by

Patient communication

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Involuntary motion uses what?

Shortest possible exposure time

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Air gap technique

alternative to grid use
long SID and increased OID
does NOT result in decrease in production of secondary or scattered radiation

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Pt dose reduced by what exposure factors

Increased kVp decreased mAs

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Fluoro time max

5 min or 300 seconds

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Magnification factor

SID/SOD

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Minimum source to skin distance fixed fluoro unit

15 inches (38 cm)

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Minimum source to skin distance mobile fluoro unit

12 inches (30 cm)

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Dose Area Product

To measure total dose to a pt site in order to reduce pt rad dose

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Mobile radiographic unit

Minimum 6 ft/ 72 inches/ 180 cm/ 2 meters

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Medical imaging’s principle of radiation protection is based on what

The non threshold, linear dose response relationship

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Leakage radiation

emitted from xray tube

- limited to 100 mR/hr at 1 meter (1 mGy/hr at 1 meter)

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Natural sources of rad

Radon, cosmic, terrestrial

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Greatest source of artificial radiation

Medical imaging

- other sources can be nuclear fallout, consumer products

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What is the most effective method of personnel protection

Distance

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Inverse square law example

By increasing distance from rad source from 4 ft to 8 ft, rad exposure will decrease by factor of 22, or 4 times

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Half value layer

Thickness of an absorbing material required to reduce the intensity of rad to one half of its original value

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Lead apron lead equivalent

0.5 mm Pb

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Lead apron lead equivalent on port

0.25 mm Pb

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Gloves lead equivalent

0.25 mm Pb

Thyroid shield lead equivalent

0.5 mm Pb

Glasses lead equivalent

0.35 mm Pb

Bucky slot cover lead equivalent

0.25 mm Pb

Spot film device protective curtain lead equivalent

0.25 mm Pb

Clear lead-plastic overhead protective barrier

0.5 mm Pb

Primary protective barrier

- the surfaces that can be struck by primary beam | - located perpendicular to primary beam

Primary protective barrier Pb equivalent

- 1/16 inch (0.16 cm or 1.6 mm) | - if primary barrier is a wall, lead must extend 7 ft (210 cm or 2.3 meters) from floor

Secondary protective barrier

Surfaces struck with leakage and scatter radiation, located parallel to primary beam

Secondary protective barrier Pb equivalent

- 1/32 inch (0.08 cm or 0.8 mm) | - 1/2 inch (1.25 cm) of secondary barrier must overlap primary barrier where they meet

6 ft to meters

1.8 or 2 meters

Typical conventional (non digital) fluoroscopy units operate within what range

2 to 5 mA

Automatic brightness control

Designed to maintain a predetermined level of light intensity exiting the image intensification tube

Fluoroscopic exposure switch should be what type

Dead man

Film badge

- relies on ability of ionizing radiation to effect a density change on the film emulsion - amount of dose received by badge is a function of the degree of film blackening that happens on the surface of the film emulsion that lie under various forms of attenuating filters like tin or copper

Film badge benefits

- good for monitoring over long period of time - inexpensive and reliable - provides permanent or archival record

functional component Of Thermoluminescent dosimeter (TLD)

lithium fluoride

How are reading from TLD made

By heating lithium fluoride chip to a point of combustion

Thermoluminescent dosimeter (TLD)

- the light spectrum the chip yield will change with changing levels of energy absorbed by the chip - once chip is heated it is destroyed - no archival record other than a written record of findings

Pocket dosimeter

-relies on ability of ionizing radiation to ionize a gas within a sealed chamber resulting in a change of charged electrode, discharging the electron

Pros of Pocket dosimeter

- good for short term monitoring or testing (immediate readout) - may be recharged and reused

Cons of Pocket dosimeter

- prone to inaccurate readings with rough handling | - does not offer permanent record of dosage

Detector for Optically stimulated luminescent dosimeter (OSLD)

Aluminum oxide

Optically stimulated luminescent dosimeter (OSLD)

- laser light reads the sensing material which causes the material to become luminescent in proportion to the exposure that the sensing material received - filters made of aluminum, tin, and copper allow for determination of the energy levels striking the badge

Greatest to least sensitive dosimeters

1) greatest sensitivity: pocket dosimeter 2) OSLD 3) TLD 4) least sensitivity: film badge

Annual whole body exposure (occupational)

5 rem (50 mSv)

Lens of the eye (occupational)

15 rem (150 mSv)

Red bone marrow, breast, lung, gonads, skin, and extremities (occupational dose)

50 rem (500 mSv)

Cumulative effective limit (occupational)

1 rem x age in years | 10 mSv x age in years

Annual effective dose equivalent limit (public)

0.5 rem (5 mSv)

Dose equivalent limits for the lens of the eye, skin, and extremities (public)

5 rem (50 mSv)

Embryo/fetus exposure

0.5 rem (5 mSv) for the entire gestational period and max 0.05 rem (0.5 mSv) per month during gestational period

Dose equivalent limits (DEL)

The max dose of radiation that in light of present knowledge would not be expected to yield any significant radiation effects

Inherent filtration includes what

Xray tube window, oil in the xray tube housing, and housing port

Added filtration includes

Aluminum plate and the collimator mirror

Order in which primary xray beam passes through filters in their path

1) xray tube window 2) oil surrounding xray tube 3) xray tube housing port 4) aluminum plate 5) collimator mirror

DAP (dose area product)

Xray exposure in air based on a specific area

Safety 2 Flashcards

(61 cards)