ch 11 study quiz radiation protection

When obtaining a dorsoplantar projection of a foot, which of the following types of filters should be used to provide a greater uniform density of the anatomy?

Wedge filter

Which of the following is not an x-ray beam limitation device?

Filter

When performing a mobile radiographic procedure, to reduce the radiation exposure to the patient, the radiographer must use a minimal source-skin distance of

30 cm.

The control panel, where technical exposure factors are selected and visually displayed for the equipment operator, must be located

behind a suitable protective barrier that has a radiation-absorbent window that permits observation of the patient during any procedure.

When generator settings are changed from one mA and time combination to another, the most that linearity can vary is

10%.

What is the purpose of radiographic beam filtration?

To reduce exposure to the patient's skin and superficial tissues by absorbing most of the lower-energy photons from the heterogeneous beam.

Digital radiography images can be accessed

at several workstations at the same time, thus making image viewing very convenient for physicians providing patient care.

Digital radiography systems offer several advantages over computed radiography. Some of these include

1. lower dose.

2. ease of use.

3. immediate imaging results.

4. manipulation of the image.

1, 2, 3, and 4

Which of the following materials is commonly used in the tabletop of a radiographic examination table to make the tabletop as radiolucent as possible so that it will absorb only a minimal amount of radiation, thereby reducing the patient's radiation dose?

Carbon fiber material

Luminance is determined by measuring the concentration of light

over a particular field of view.

To visualize smaller and lower contrast objects during interventional procedures, high level control fluoroscopy uses exposure rates that are ____________ those normally used in routine fluoroscopy.

higher than

Total filtration of _______________________ for fixed x-ray units operating above 70 kVp is the regulatory standard.

2.5-mm aluminum equivalent

During a fluoroscopic examination, a resettable cumulative timing device measures the x-ray beam-on time and sounds an audible alarm or in some cases temporarily interrupts the exposure after the fluoroscope has been activated for what length of time?

5 minutes

When a fluoroscopic image is electronically amplified by the use of an image intensification system, which of the following benefits results?

1. Increased image brightness

2. Saving of time for the radiologist

3. Patient dose reduction

1, 2, and 3

In digital radiography the number of different shades of gray that can be stored in memory and displayed on a computer monitor is termed

grayscale.

When using digital fluoroscopy systems, making use of the last image hold feature can

be an effective dose reduction technique.

In standard image intensification fluoroscopy, an x-ray beam half-value-layer (HVL) of 3 to 4.5 mm aluminum is considered acceptable when kVp ranges from

80 to 100.

When an exposed computed radiography imaging plate is ready to be processed, an imaging reading unit is used to scan the photostimulable phosphor imaging plate with a helium-neon laser beam. This process results in the emission of violet light that is changed into an electronic signal by a device called a

photomultiplier tube.

The protective tube housing serves as a shield against _____________________ entering the x-ray tube, thereby preventing electric shock while also facilitating cooling of the x-ray tube.

the high voltage

Fluoroscopic devices are capable of subjecting the patient, the equipment operator, and other personnel near the fluoroscopic equipment to substantial doses of ionizing radiation. These devices include

1. C-arm fluoroscopes.

2. fluoroscopes on stationary equipment with HLC mode used for interventional procedures.

3. biplane interventional fluoroscopic systems.

1, 2, 3, and 4

If the luminance of the collimator light source is adequate, the localizing light beam will satisfactorily outline the margins of the radiographic beam on the area of clinical interest on

all patients.

Depending on the area of the body being examined with a fluoroscopic image intensification system, a range of ___________ kVp is generally used for adult patients.

75 to 110

Current federal standards limit entrance skin exposure rates of general-purpose intensified fluoroscopic units with maximum technique factors engaged to a maximum of ________________, as measured at tabletop, with the image intensifier entrance surface at a prescribed 30 cm above the tabletop.

100 mGya/min

Of the following procedures, which involve extended fluoroscopic time?

1. Biliary drainage

2. Stent and filter placement

3. Urinary or biliary stone removal

1, 2, and 3

Computed radiography, because of its higher exposure latitude, makes grid use on the pediatric population

less necessary than was previously believed.

adjustable lead shutters mounted within the device at different levels, a light source to illuminate the x-ray field & permit it to be centered over the area of clinical interest, & a mirror to deflect the light beam toward the patient to be radiographed

Light-Localizing variable-Aperture rectangular collimator

Are mounted as close as possible to the tube window to reduce the amount of off-focus radiation (x-rays emitted from parts of the tube other than the focal spot) coming from the primary beam & exiting at various angles from the x-ray tube window, upper part

First Set Shutters

They consist of two pairs of lead plates oriented at right angles to each other, lower part

Second Set Shutters

Lower shutters; are mounted below the level of the light source & mirror & function to confine further the radiographic beam to area of clinical interest

Second Set Shutters

the brightness of a surface, it quantifies the intensity of a light source, Must be adequate to permit the localizing light beam to outline the margins of the radiographic beam adequately on the patients anatomy

Luminance

Consist of electronic sensors in a cassette holder that sends signals to the collimator housing

Positive Beam Limitation

Consist of a flat piece of lead with a hole of designated size & shape cut in the center (can be rectangular, square, or round)

Aperture Diaphragm

to reduce exposure to the patients skin & superficial tissue by absorbing most of the lower-energy photons

Filtration

Includes the glass envelope encasing the x-ray tube, the insulating oil surrounding the tube, & the glass window in the tube housing

Inherent filtration

The aluminum equivalent of 0.5 mm

inherent filtration

Consist of sheets of aluminum (or equivalent) of appropriate thickness

Added filtration

Located outside the glass window of the tube housing above the collimator shutters

Added filtration

Is the combination of inherent & added filtration ( these combine to equal required amount necessary to filter useful beam adequately)

Total Filtration

regulatory standards is 2.5 mm aluminum equivalent for fixed x-ray units operating above 70 kVp

Total filtration

Is when the thickness of a designated absorber (such as aluminum) is required to decrease the intensity of the primary beam by 50% of its initial value (laws regulate that so much of the low energy rays must be removed)

Half-Value Layer

due to the fact that computerized images can be manipulated after exposure & repeat images are rare, patients receive higher radiation doses than necessary to produce the initial images

Dose-Creep

process that allows the fluoroscopist to see the most recent image without exposing the patient to another pulse of radiation

Last-Image-Hold

Is a resettable device that times the x-ray beams "on-time" & sounds an audible alarm or temporarily interrupts the exposure after the fluoroscope has been activated for 5 minutes

Cumulative Timer

The x-ray tube housing that encloses the x-ray tube must be constructed so that leakage radiation does not reach the patient. At what distance is this measured from the x-ray source & at what dose?

-1m (3.3ft)

-not exceed 100 mR/hr

Why the x-ray table top must be as radiolucent as possible?

so that it will absorb only minimal amounts of radiation, thereby reducing the patients radiation dose

Know the material that the radiographic table is commonly made of?

carbon fiber material

What is the most common x-ray beam limitation device?

Light -localizing variable aperture rectangular collimator

Know the types of x-ray beam limitation devices?

-Light -localizing variable aperture rectangular collimator -aperture diaphragm,

-cones,

-cylinders

Know what these devices confine (join) to do?

the useful, or primary beam, before it enters the area of clinical interest, thereby limiting the quantity of body tissue radiated

Why does the luminance of the collimator light have to be adequate?

to permit the localizing light beam to outline the margins of the radiographic beam adequately on the patients anatomy

Know what happens to the collimator when PBL activated?

the collimators are automatically adjusted so that the radiation field matches the size of the IR

Know how the radiographer ensures that the collimation is adequate?

by collimating the radiographic beam so that it is no larger than the IR

What the dimensions of the hole in the aperture diaphragm determine?

determines the size & shape of the radiographic beam

Know some examples of radiographic exams that would use cones?

head projections (sella turcica), paranasal sinuses, vertebral column, & chest

Know how filtration decreases the overall intensity of radiation?

filtration absorbs some of the photons in a radiographic beam

How much filtration the light-localizing variable aperture rectangular collimator adds?

an additional 1mm aluminum equivalent

What is the most commonly used metal for filters in diagnostic radiology?

aluminum

Why is aluminum metal used?

because it effectively removes low-energy x-rays from a polyenergetic x-ray beam without severely decreasing the x-ray beam intensity

What is the source-skin-distance in general radiology?

12"

What does DR mostly eliminate the need for?

almost all repeats due to improper technique

Even with digital radiography, what is still your responsibility as a radiographer?

to determine & use technical factors the first time you expose

Know the 3 benefits of image intensification fluoroscopy?

1. increased image brightness

2. saving the radiologist time

3. patient dose reduction

What is the significant impact that pulses or intermittent fluoroscopy has made?

-decreases patient dose, especially in long procedures

-helps extend the life of the tube

What is the required & preferred SSD for fluoroscopy?

-Required is 12"

-Preferred is 15"

Know the function of a filter in fluoroscopy?

to reduce patients skin dose

In fluoroscopy what is the total aluminum equivalent filtration that must be permanently installed?

2.5 mm

What are the maximum current federal standards that limit entrance skin exposure rates of general purpose intensified fluoroscopic units?

100 mGy/min (10R/min)

What is the primary protective layer required for an image intensifier?

2mm lead equivalent

Know how to reduce patient entrance dose for C-arm procedures?

the patient to image intensifier distance should be as short as possible

Know who's responsibility it is to monitor & document fluoroscopic procedure times?

the radiographers

The radiographic beam should be collimated so that it is which of the following?

A. Slightly larger that the image receptor

B. No larger than the image receptor

C. Twice as large as the image receptor

D. Four times as large as the image receptor

B. no larger than the image receptor

Both alignment and length and width dimensions of the radiographic and light beams must correspond to within:

A. 1% of the SID

B. 2% of the SID

C. 5% of the SID

D. 10% of the SID

B. 2%

What is the function of a filter in diagnostic radiology?

A. To permit only alpha rays to reach the patients skin

B. To permit only beta particles to interact with the atoms of the patients body

C. To decrease the x-radiation dose to the patients skin and superficial tissue

D. to remove gamma radiation from useful beam

C. to decrease the c-radiation dose to the patients skin and superficial tissue

HVL maybe defines as the thickness of a designated absorber required to do which of the following?

A. increase the intensity of the primary beam by 50% of its initial value

B. increase the intensity of the primary beam by 25% of its initial value

C. Decrease the intensity of the primary beam by 50% of its initial value

D. Decrease the intensity of the primary beam by 25% of its initial value

C. decrease intensity by 50% of the primary beam

When compared with conventional screenfilm systems, the photostimulable phosphor in the computed radiography imaging plate is much more sensitive to scatter radiation before and after it is sensitized through exposure to a radiographic beam. Because of this increased insensitivity, which of the following is true?

1) Five millimeters of added aluminum equivalent filtration must always be used during routine CR imaging

2) A radiographic grid may be used more frequently during CR imaging

3) Any source to image receptor distance can be used during CR imaging without adjustment in technical exposure factors.

A. 1 only

B. 2 only

C. 3 only

D. 1,2, and 3

B. 2- a radiographic grid may be used more frequently during CR imaging

To minimize skin exposure to electrons produces by photon interaction with the collimator, how far below the collimator should the patient's skin surface be?

A. At least 1cm below

B. At least 5 cm below

C. At least 10 cm below

D. at least 15 cm below

D. 15cm

Which of the following aluminum equivalents for total permanent filtration meets the minimum requirement for mobile diagnostic and fluoroscopic equipment?

A. 0.5 mm aluminum equivalent

B. 1.0 mm aluminum equivalent

C. 2.0 mm aluminum equivalent

D. 2.5 mm aluminum equivalent

D. 2.5 mm aluminum equivalent

The trough, or bilateral wedge, filter, which is used in some dedicated chest radiographic units, is an example of which of the following?

A. Compensating filter

B. filter used in all digital imaging systems

C. Filter used in all dedicated mammographic units

D. filter used in all CT systems

A. compensating filter

To decrease patient exposure during fluoroscopic procedures, the fluoroscopist can:

1) limit the size of the fluoroscopic field to include only the are aof anatomy that is of clinical interest

2) Employ the practice of intermittent, or pulsed, fluoroscopy to reduce the overall length of exposure

3) Choose to use a conventional fluoroscope instead of an image intensification fluoroscope

A. 1 and 2 only

B. 1 and 3 only

C. 2 and 3 only

D. 1,2, and 3

A. 1 and 2 only

A diagnostic -type protective tube housing must be constructed so that leakage radiation measured at a distance of 1m from the x-ray source does not exceed _____ when the tube is operated at its highest voltage at the highest current that allows continuous operation.

A. 5 Gy/hr

B. 3 Gy/hr

C. 1 Gy/hr

D. 0.1 Gy/hr

C. 1 Gy/hr

What is the adequate collimation for an x-ray beam?

no larger than the IR

What is the most popular beam limitation device?

collimator

Name three types of beam limitation devices other that the collimator

Aperture diaphrams, cones, cylinders

What is the purpose of beam filtration?

to reduce patient's skin and superficial tissue by absorbing low energy photons from heterogeneous beam (hardening the beam occurs)

When speed of screen film systems doubles, the patients radiation exposure is ______ by approx. ____%.

reduced, 50%

When the amount of silver halide crystals contained in a film emulsion is increased, the speed of the film is _____.

A. increased

B. decreased

C. remains the same

A. increased

The image intensification fluoroscopy benefits in what way

1) increased image brightness

2) saving of time for the radiologist

3) patient dose reduction

A. 1 and 2 only

B. 2 and 3 only

C. 1 and 3 only

D. all

D. all

Total filtration requirement is

2.5mm aluminum equivalent

What is the main constructed material for compensation filters:

aluminum

What type of filters help with dose reduction and uniform radiographic images of body parts?

compensation filters

Wedges and troughs are examples of?

compensating filters

Total filtration includes what?

inherent and added filtration

What is the ratio of the difference in mR/mAs values between two successive generator stations to the sum of those mR/mAs values?

Linearity (L)

Linearity can not exceed what %

10%

Exposure Linearity refers to a consistency in _____ radiation intensity at any selected _____ settings when generator settings are changed from 1 milliamperage and time combination.

output, kVp

How do you find mAs?

mAs= mA x exposure time

How does the last-image hold feature benefit the patient?

reduces patient dose

A cumulative timer must be provided during what exam and unit?

fluoroscopy

Exposure on fluoroscopy units will interrupt the exposure after the unit has been activated for?

5 minutes

Fluoroscopy for adult patients the technical factor range in kVp is ?

75-110 kVp