major's bio FOUR

most classical scatter photons

are absorbed in the body

to produce a radiographic image that represent anatomy, there must be

photoelectric interactions

pair productions _

never occurs in radiographic procedures

the effect of classical scatter interactions on image quality

is minimal

barium sulfate is used as a contrast agent to visualize soft tissue structures such as the stomach because it

has a high atomic number

imaging tissues with lower atomic numbers results in

decreased attenuation

to minimize occupational exposure, the technologist should

wear protective apparel

pair production occurs when the incident photon interacts with

nucleus of the atom

compton scattering results in

• Compton electron

• secondary electron

• Compton scatter electron

all of the above

the probablity of a compton interaction occurring depends on

the energy of the incoming x-ray photon

when it does intersect with the IR, the compton scatter photon contributes no useful info b/c

it has changed directions

photoelectric interactions are more likely to occur in

bone

scattering in the diagnostic range is due to

compton effect

coherent scattering typically occurs with x-ray photons in the energy range of

5-10 kev

for photodisintegration to occur, to incident photon must have an energy level of at least

10 mev

after a photoelectric interaction, the incident photon

loses all of its energy and no longer exists

what is produced as a result of pair production

positron and electron only

excessive absorption is the result of

using a kvp that is too low for the exam

for photoelectric interactions to occur, the energy of the incident photon

may be the same or greater than the binding energy of an inner shell electron

increasing the thickness of the part being imaged results in

increased attenuation

the photoelectric interaction involves removal of

an inner-shell electron

attenuation of the x-ray beam in the diagnostic range is due to

absorption

pair production requires an x-ray photon with an energy of at least

1.02 mev

classical interactions are also known as

coherent or thomson

compton scattering invovles the x-ray photon

removing a middle or outer shell electron

in reference to pt rad dose, classical scatter interactions

slightly increase dose

radiation interacting with bone is more likely to be absorbed, resulting in that area of the image being

a shade of white

at higher kilovoltages within the diagnostic range

the percentage of photoelectric interactions increases

differential absorption occurs because different tissues have varying amounts of

photoelectric interactions

during a photoelectric interaction

an inner shell electron is ejected

photoelectric interactions

contribute significantly to pt dose

the ability to remove electrons from an atom is

ionization

coherent scattering involves

an x-ray photon with low energy

in producing a radiographic image, wotf occurs last

radiation interacts with the IR

reducing the amount of compton scattering

is very important in producing quality images

the x-ray photon produced during classical scattering

travels in a different direction than the incoming photon

the end product of a photoelectric interaction is

a photoelectron and an ionized atom

the primary source of rad exposure to the radiographer who is in the room during an exposure is

from scatter from the pt

at higher kilovoltages within the diagnostic range

the percentage of compton interactions increases

photodisintegration interactions

never occur in radiographic procedures

AEC controls the amount of rad reaching the IR by controlling the

time of exposure

when there is a significant amount of scatter rad reaching the detector, the exposure time will

reach the backup mas

if the backup time is shorter than the actual exposure time needed for a properly exposed image

the IR will be underexposed

the detectors selected for an image should be

the ones that are SI by the anaotmic structure of interest

wotf would be considered an additive disease

congestive heart failure

ioniation chamber AEC detectors are entrance-type devices because the x-rays must

enter the detector before getting to the IR

with digital imaging using AEC, if an AP thoracic spine is imaged using 110 kvp instead fo 80 kvp, the pt exposure is __

lower

using a lower mA station during an AEC exam results in

increased exposure time

with digital imaging using AEC, if an AP thoracic spine is imaged with the exposure adjustment changed from 0 to 2, the exposure time is

longer

wotf patient conditions requires a change in technical factors

• plaster cast

• obesity

• additive disease

all of the above

__ identitfy optimal kvp values and alter the mAs for variations in part thickness

fixed kvp variable mas

with digital imaging using AEC, what factor is decreased if an AP thoracic spine is imaged using an outside instead of the detector

exposure time

an ionization chamber is a hollow cell that contains

air

once the electric charge from an AEC detector reaches a preset point

the exposure will stop

the AEC minimum response time may pose a problem when

the pt is unable to hold still for the exposure

these can be adjusted to increase or decrease the amount of radiation needed to terminate the exposure using AEC

density setting

anatomically programmed technique is a system in which the radiographer selects

preset settings based on the part of being imaged

the two types of detectors used in AEC are

phototimers and ionization chambers

phototime AEC detectors are usually exit-type devices because

the x-rays must exit the IR to get to the detector

if the pt for an AP thoracic spine image is centered so that the spine is not over the top of the detector

the IR exposure will be insufficient

when imaging a pts right hip, which detector should be activated

center only

If the AEC detectors are not completely covered by the part being imaged and are exposed to primary radiation

The exposure will terminate very quickly 

Which of the following is the most critical aspect of successfully performing an examination using AEC?

Centering the anatomy of interest over the detector

If the radiographer is doing an upright chest using AEC but the table bucky is selected

• the back-up time will be reached.

•  the patient will be exposed to excessive radiation.

• the IR will be overexposed.

all of the above

AEC devices should be calibrated

• when the unit is first installed.

•  at regular intervals.

•  when there is a change in the type of I being used.

all of the above

primary purpose of AEC is to

control the amount of radiation reaching the IR

If the back-up time is set by the equipment, the exposure time should end when the mAs reaches

600

There is typically a configuration of at least __ AEC detectors in place

3

The predetermined level of radiation exposure needed to terminate the exposure when using AEC is set by

the equipment service personnel

when using AEC, the kvp

is set appropriate for the study

The actual amount of exposure used for an image when AEC is being used is the

mAs readout

in imaging a child, a short exposure time is needed for an examination using AC. Therefore, the mA setting should

be high

today’s AEC system is most likely to use an

ionization chamber

When your patient for an AP abdomen is very heavy, using AEC

appropriate exposure to the IR

the reason to have a back-up time is to

protect the patient from excessive exposure and keep the tube from excessive heat-loading

the orginial type of AEC detector was the

phototimer

using a higher kVp during an AEC examination results in

a shorter exposure time

when the radiographer has the opportunity to set the back-up time, it should be approximately __ of the expected exposure time

150%

the shortest exposure time that a radiographic tube with AEC can have is the

minimum response time

when using AEC with digital imaging, errors resulting in overexposure to the IR result in

images with appropriate brightness and overexposed pts

pre-established guidelines used by the radiographer to select standardized manual or AEC exposure factors for each typical radiographic examination are called

exposure technique charts

when using AEC, destructive pathologic conditions can cause

overexposure

when the x-rays enter the ionization chamber

• Atoms become ions

• Atoms give up electrons

• Electrons and positive ions become electricity

all of the above

the maximum length of time that an exposure lasts when using AEC is the

back-up time

the device that converts the light energy to an electric signal is the

photodiode and photomultiplier