LRA-216 Review Flashcards
What describes the energy that is absorbed in matter from any type of ionizing radiation, and is considered the unit of absorbed dose?
rad/ gray
What is the unit of dose equivalent or occupational exposure?
rem/ sievert
What is the SI unit for Roentgen (R)?
coulomb/kilogram
Which of the following is the SI unit for the rad?
gray
What is the SI unit for the rem?
sievert
_____ is a measure of the energy transferred to material as an ionizing particle travels through it. This measure is used to quantify the effects of ionizing radiation on biological specimens.
linear energy transfer (LET)
A graphical representation of observed effects compared with radiation dose is termed a
dose response relationship (curve)
How tall must primary protective barriers be?
7 ft
A type of dosimeter consisting of radiation dosimetry film to determine the amount of exposure personnel have received is the
film badge
A device containing lithium fluoride or calcium fluoride crystals to calculate the amount of personnel exposure is the
thermoluminescent dosimeter (TLD)
A dosimeter containing filters composed of aluminum, tin, and copper, and thin strips of aluminum oxide, which when stimulated by a laser light becomes luminescent to the amount of radiation received is the
optically stimulated luminescent dosimeter (OSL)
A device which uses an ionization chamber to determine personal exposure level is the
pen dosimeter
The measurement of ionizing radiation doses to personnel is termed
dosimetry
The primary protective barriers must consists of ___ inch lead
1/16
Lead aprons worn during a mobile exam must have a lead equivalency of at least _____ mm.
0.5
Modern radiation protection guidelines are established on the philosophy of keeping exposures
As low as reasonably achievable achievable (ALARA)
The general public has an annual effective dose limit of _____ Seiverts.
0.05
What is a measure of the radiation to a patient’s skin at the entrance surface?
Entrance skin exposure (ESE)
Increasing the distance between the individual and the source of radiation is an effective method to reduce exposure to radiation. Distance utilizes what?
Inverse square law
Controlled area design limits require barriers to reduce the exposure rate to less than _____ mrem/wk.
100
Applying the inverse square law, if we double our distance from the source, the intensity at our new distance is _____ as much as the original intensity.
1/4
Involuntary patient motion is best dealt with by
using a short exposure time and high mA
Radiation monitoring of personnel is required when personnel receive _____% of the annual effective dose limit.
10
Which of the following combinations would reduce patient radiation dose during an x-ray exam?
High kVp, Low mAs, increased filtration
To within what percent of the SID must the collimator light and actual irradiated area be accurate?
2%
How much total filtration is required when using over 70 kVp?
2.5 mm of Al EQ
The number of repeat radiographs can be reduced by
eliminating voluntary patient motion using immobilization devices
Half-value layer (HVL) is defined as the thickness of a designated absorber required to
decrease the intensity of the primary beam by 50% of its initial value
An effective way of reducing patient dose is through
accurate and effective positioning
Which of the following are placed between the patient and the image receptor (IR) to preferentially absorb scatter radiation?
Radiographic grids
