Chapter 11 Equipment Design for Radiation Protection Flashcards by Danielle Brough

What kind of radiation does the tube housing protect the patient and personnel from?

off focus or leakage radiation

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What does the tube housing prevent?

electrical shock, damage to rough handling, helps with cooling of the tube

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What is the tube housing lined with?

lead

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Off focus radiation creates what?

ghosting

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The limit of off focus radiation for the tube housing is to not exceed ____ one meter away at highest voltage

.88 mGya/hr (100 mR/hr)

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Who required an audible sound and visible radiation symbol?

Radiation Control for Health and Safety Act of 1968

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What is required of radiographic tables and why?

must be as radiolucent as possible so that it will absorb only a minimal amount of radiation reducing the patients radiation dose

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What are the radiographic tables made of?

carbon fiber material

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The _____ to IR is the source to image receptor distance indicator

anode focal spot

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The accuracy of the indicator must be accurate within ____ of the indicated SID and centering must be within _____ of SID indicator

2%
1%

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How large should the primary beam be?

collimated to no larger than the size of the IR

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Image quality is increased when collimating by _____ the amount of ______ radiation

decreasing
scatter

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What were earlier collimation devices made of?

Cones and cyllinders

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This is the automatic or manual collimator that is used on digital units today

light localizing variable aperture rectangular collimator

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The first set of shutters is ____ to the tube window and ____ off focus radiation but ______ do anything to reduce primary beam

close
reduces
does not

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The second set of shutters is the ____ ____ type and is _____ on the underside of the collimator head when looking at the light

variable aperture
visible

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The patient skin surface should be at least _____ below the collimator head on fixed units and _____ on mobile units

15cm
30cm

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______ refers to the brightness of a surface and quantifies the intensity of light source

luminance

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The unit of measure is ____ for luminance

nit - candela per square meter, intensity measured at 40” should be 15 foot-candles = 161 nit

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Coincidence between radiographic beam and localizing light beam must be within ____ of SID

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This must ensure that the collimation is adequate by collimating the radiographic beam so that it is no larger than the IR

positive beam limitation

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The state requirements for the positive beam limitation is _____ of the SID

2-3%

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______ reduces exposure to patient skin and superficial tissue by absorbing most lower-energy photons, increases beam quality and test rid of soft rays

filtration

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Filtration is also referred to as

hardening the beam

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reducing exposure to the skin ______ absorbed dose

decreases

What are the two types of filtration?

inherent and added

Where is inherent filtration?

glass envelope, insulating oil, glass window

What is the normal aluminum equivalency, light localizing collimator equivalency and minimum aluminum filtration?

.5mm 1mm 1.5mm

1.5mm equivalent aluminum filtration is also called

intrinsic filtration

Added filtration is located _____ the glass envelope but _____ the collimator shutters

outside above

inherent + added = ______

total filtration

70 kVp and above is ____ AI Eq 50-70 kVp is _____ AI Eq below 50 kVp is _____ AI Eq

2.5mm 1.5mm .5mm

Aluminum has an atomic number of

Aluminum ______ low energy photons from a poly energetic beam without severely _____ the intensity of the beam

removes decreasing

Why is aluminum used?

lightweight, sturdy, inexpensive, easily available

Quality assurance test to check filtration, thickness of absorber to decrease the intensity of the primary beam by 50%, measure of beam quality

half value layer

The _____ act of _____ required to have adequate filtration in all tubes

Radiation Health and Safety Act of 1968

kVp _____ determines the amount of required filtration

potential

Compensating filters help with dose _____ and provides ______, made up of aluminum or lead acrylic

reduction uniformity

What are the two types of compensating filters and where do they go?

wedge - foot trough - chest

The thick part of the compensating filter goes over the ____ part of the body

thin

The function of a compensating filter is to even out ______ of the body part with different _______, helps with dose reduction and uniformity

densities thicknesses

Consistency of exposures of same technique set throughout the day, variance of _____ or less is acceptable

exposure reproducibility 5%

must be less than .1 (10%), consistency in output radiation intensity at selected kVp settings when generator settings are changed from one mA and time setting to another

exposure linearity

Radiographic grids are used to _____ image quality and _____ scatter

improve reduce

Grids use _____ dose

_____ grid ratios increase the patient dose

higher

Virtual grids work in post processing by the system removing _____

scatter

In mobile radiography at least _____ source to skin distance is required

30cm (12")

When the SSD is small, the patient entrance exposure is significantly ______ than exit exposure

greater

The larger the image matrix and smaller the individual units the ______ the resolution

better

The size of a pixel is about ____micrometers

What are the three materials used for image receptors

amorphous silicon - scintillator that converts x-ray energy to visible light charge coupled device - converts visible light into electrical signals amorphous selenium - converts x-ray directly into electrical signals

What are advantages to digital imaging

lower dose ease of use and faster exams immediate images image manipulation

What are disadvantages to digital imaging

more costly one IR size

The computed radiography plate is made of _____

europium activated barium fluorohalide phosphors

_____ ______ is the process of using automatic settings leading to an increased dose because you are not paying attention to exposure index numbers

dose creep

____ is more sensitive to scatter so grids should be used ____ often

CR more

_____ produces the greatest patient exposure rate in diagnostic radiology

fluoroscopy

What are three benefits of fluoroscopy

brighter image low mA image intensifier tubes

How much brighter are fluoroscopy tubes

10,000 times

how low can mA settings go during fluoro

new systems 1-1.5 mA old systems 3-5 mA

What are the two multi field or magnification phosphors and what are they made of?

input phosphor - cesium iodide output phosphor - zinc cadmium sulfide

magnification produces a smaller area but causes it to be more magnified which ______ the mA

increases

magnified images have more of an ____ appearance so there is _____ noise

even less

the ____ _____ _____ feature should be used to reduce patient and personnel dose

last image hold

for pulsed and interrupted fluoroscopy the kVp increases, the tube SSD should for fixed units should be no less than _____ and ____ for mobile units

38cm 30cm

The half value layer for pulsed and interrupted fluoroscopy should be ____ aluminum for 80-100 kVp

3mm-4.5mm

_____ ______ _____ is an alarm that is sounded after 5 minutes of Fluoro time, all fluoroscopy time should be documented at the end for physician and radiologist

cumulative timing device

The exposure rate limitations for entrance skin exposure should be ______ per minute at 30cm

88 mGya (10 R)

The fluoroscopy exposure control switch is what type of switch

dead man

The image intensifier should be _____ to the patient to reduce scatter

as close as possible

Weakest scatter is _____ in relation to the patient

on top of the patient

What is used in vascular imaging

digital subtraction angiography

reference image of the same area before contrast is administered

mask

remove of overlying structures to view vessels more clearly

roadmapping

When are high level control interventional procedures done

catheters, vascular type studies, fluid drainage, occlusions

visualization of smaller and lower contrast objects requires a ______ exposure rate

higher

When did the FDA issue warnings about high level control fluoro

1974

in 1994 the FDA limited table top exposure rates to _____

100 mGy/minute (10 R/min)