Chapter 13-16 Flashcards by Rachel Brenner

EfD does not include:

Personal medical exposure
Natural background exposrue

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Lifetime EfD in mSv should not exceed __ times the person’s age in years

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Annual occupation EfD limit is

50 mSv

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Annual occupational EfD limit of 50 mSv is a/an _____ boundary limit

Upper

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Annual EfD limit for the general population is

1 mSv for frequent exposures

5 mSv for infrequent exposures

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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)

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Radiography is not considered a ___________ profession

Hazardous

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During a diagnostic examination, the patient becomes a source of scattered radiation as a consequence of the _______ interaction process

Compton

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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

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Removes nonuseful low-energy photons from the primary beam

Filtration

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Shielding protects patient from what type of radiation

Scatter and leakage (secondary sources)

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What is the minimum lead thickness for aprons

.25mm

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What is the standard lead thickness for aprons

.5mm

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What is the standard lead thickness for fluoroscopy

.5mm

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How does beam energy effect side scatter?

The higher the beam energy, the less side scatter to strike imaging personnel

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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

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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

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What is the relationship between time and radiation dose

Direct; as the length of exposure time increases, the radiation dose increases

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What is the most effective means of protection from ionizing radiation

Distance

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Inverse Square Law states that the intensity of radiation is ____________ proportional to the square of the distance from the source

Inversely

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Most common materials used for shielding

Lead and concrete

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Effectiveness on shielding material depends on:

Atomic number
Density
Thickness

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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

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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

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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

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

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)