Chapter 13-16 Flashcards
EfD does not include:
Personal medical exposure
Natural background exposrue
Lifetime EfD in mSv should not exceed __ times the person’s age in years
10
Annual occupation EfD limit is
50 mSv
Annual occupational EfD limit of 50 mSv is a/an _____ boundary limit
Upper
Annual EfD limit for the general population is
1 mSv for frequent exposures
5 mSv for infrequent exposures
The amount of radiation received by the workforce can be larger than the amount recieved by the general public without alteration in the:
Genetically significant dose (GSD)
Radiography is not considered a ___________ profession
Hazardous
During a diagnostic examination, the patient becomes a source of scattered radiation as a consequence of the _______ interaction process
Compton
At a 90 degree angle to the primary x-ray beam at a distance of 1m, the scattered x-ray intensity is approximately ___________ of the intensity of the primary x-ray beam
1/1000
Removes nonuseful low-energy photons from the primary beam
Filtration
Shielding protects patient from what type of radiation
Scatter and leakage (secondary sources)
What is the minimum lead thickness for aprons
.25mm
What is the standard lead thickness for aprons
.5mm
What is the standard lead thickness for fluoroscopy
.5mm
How does beam energy effect side scatter?
The higher the beam energy, the less side scatter to strike imaging personnel
What is the purpose of the lead apron and additional monitor during pregnancy
To ensure the monthly EqD to the empryo-fetus does not exceed .5 mSv
What is the lead thickness of a maternity protective apron
.5-mm lead over the entire length and width and an extra 1-mm panel that runs transversely across the width of the apron
What is the relationship between time and radiation dose
Direct; as the length of exposure time increases, the radiation dose increases
What is the most effective means of protection from ionizing radiation
Distance
Inverse Square Law states that the intensity of radiation is ____________ proportional to the square of the distance from the source
Inversely
Most common materials used for shielding
Lead and concrete
Effectiveness on shielding material depends on:
Atomic number
Density
Thickness
Specifications for primary protective barrier for 130 kVp beam
1.6mm lead
Extends 2.1m (7 feet) upward from the floor of the room when the xray tube is 1.5-2.1m (5-7 feet) from the wall
To prevent direct, or unscattered radiation from reaching personnel or members of the general public on the other side of the barrier
Primary protective barrier
Protects against secondary radiation
Secondary protective barrier
Location of secondary protective barrier
Any wall or barrier that is never struck by the primary xray beam
The secondary protective barrier should overlap the primary protective barrier by:
1.27 cm (1/2”)
Secondary protective barrier should consist of __ mm of lead
0.8mm
Used to protect the radiographer from secondary radiation
Control-booth barrier
Control booth barrier must extend ___m upward from the floor and must be permanently secured to the floor
2.1m (7ft)
How many times should diagnostic x-rays scatter before reaching any area behind the control-booth barrier
2 times
Oberservation window consists of __mm lead
1.5
With appropriate lead equivalent in the barrier, exposure of the radiographer will not exceed a maximum of __ mSv per week
1 mSv
In a well designed facility, exposure of the radiographer should not exceed __ mSv per week
.02
Clear lead-acrylic materials are impregnanted with approx __% lead by weight
30
Modular x-ray barriers are:
Shatter resistant
Can extend 2.1m (7ft) from the floor
Available in lead equivalency from .3 to 2mm
For 100 kVp, apron must be equivalent to at least ___mm thickness of lead
.25mm
___mm of lead is appropriate for mammography
.25mm
___mm lead equivalent is the most widely recommended thickness in diagnostic imaging for aprons
.5mm
____mm lead equivalent is used for gloves
.25mm
Thyroid shields should be a minimum of ___mm lead equivalent
.5mm
Optically clear eyeglass lenses contain a minimal equivalent of ___mm
.35mm
Fluoro protective curtain should have a minimum of ___mm lead equivalent
.25mm
Bucky slot shield should have at least a ____mm lead equivalent
.25mm
Diagnostic imaging personnel who receive the highest occupational exposure
Fluoroscopy
Mobile radiography
Special procedures
IR
For mobile x-ray units, the cord should be long enough to permit the radiographer to stand at least ___ from the patient/tube/useful beam
2m (6ft)
During a mobile radiographic procedure, the radiographer should attempt to stand at a ___ degree angle to the patient
90
During c-arm fluoroscopy, patterns of exposure direction are ______ predictable
Less
During c-arm fluoroscopy, where is the exposure rate caused by scatter the highest?
Near the entrance surface of the patient
During c-arm fluoroscopy, the location of the lower potential scatter dose is located on which side of the patient?
On the side of the patient away from the xray tube (image intensifier side)
The exposure rate during high-level IR procedures can range upward of:
20 to 40 cGy/minute
Annual EqD limit to localized areas of the skin and hands is:
500 mSv
Types of secondary radiation
Scatter and leakage
Radiation output-weighted time that the unit is actually delivering radiation during the week
Workload (W)
A quantity that was introduced to select the fractional contact time that most structures in diagnostic x-ray suite are struck by radiation to some degree for some fraction of the weekly beam-on time
Use factor (U)
Used to modify the shielding requirement for a particular barrier by taking into account the fraction of the work week during whcih the space beyond barrier is occupied
Occupancy factor (T)
Weekly maximum permitted equivalent dose for controlled areas
1000 uSv or
1 msV
Weekly maximum permitted equivalent dose for uncontrolled areas
20 uSv
Calculating barrier shielding requirements
mA-minutes x U x T
The objective of a shielding calculation is described as determining the thickness of a barrier sufficient to reduce the __________ in a full or partially occupied area to a value that is _____ than or equal to the ratio P/T
Air kerma
Less
Atoms that have the same number of protons within the nucleus but have different numbers of neutrons
Isotopes
Isotopes that are unstable because of their neutron-proton configuration
Radioisotopes
What type of cells are the most sensitive to damage by radiation
Well-oxygenated, rapidly dividing
What type of radiation is used for radiation therapy
Gamma or beta
What is the most important therapeutic radioisotope for cancers within the prostate gland
Iodine-125
Iodine-131 has a half life of:
8 days
What radioactive compound can be orally administered to deliver a destructive dose to a specific cancer site
Sodium iodide
Radioactive decay process
Beta decay
Nuclear medicine employs radioisotopes to:
Study organ function
Detect the spread of cancer
Treat certain types of diseases
Common radioisotopes used in nuclear medicine
Iodine-123
Technetium-99 (most common)
Technetium-99 is produced from the radioactive decay of what isotope
Molybdenum
Makes use of annihlation radiation events that are a byproduct of pair production
PET
How is annihilation radiation initiated?
Radioactive decay of the nucleus of an unstable isotope having too many protons
Unstable isoptope releases a neutron and positron
Positron will interact destructively with an electron and their masses will be converted into energy that will be carried off by two photons emerging from the annhiliation; each with a kinetic energy of 511 keV
Most important isotope used in PET scanning
Fluorine-18
What is the radioactive tracer that is metabolized by cancerous cells
Fluorodeoxyglucose (FDG)
