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Physics > AIM: Ch 21: Radiation Protection > Flashcards

AIM: Ch 21: Radiation Protection Flashcards

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1
Q

The majority of the effective dose caused by cosmogenic radionuclides is from ____

A

Carbon 14

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2
Q

The radioactive materials that have been present on the Earth since its formation are called ____

A

Primordial radionuclides

Primordial radionuclides with physical half-lives comparable to the age of the Earth (~4.5 billion years) and their radioactive decay products are the LARGEST sources of terrestrial radiation exposure

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3
Q

Most radionuclides with atomic numbers greater than lead decay to stable isotopes of lead through a series of radionuclide decays called ____

A

Decay chains

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4
Q

The short-lived alpha particle-emitting decay products of ____ are believed to be the most significant source of exposure from the inhalation of naturally occurring radionuclides

A

Radon 222 (Rn-222)

Radon-222, a noble gas, is produced in the U-238 decay chain by the decay of radium 226 (Ra-226)

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5
Q

The single greatest controllable source of radiation exposure in the US population is from ____

A

Medical imaging

The majority of the exposure is from x-ray imaging (primarily from diagnostic radiology), with a smaller contribution from nuclear medicine.

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6
Q

The following radiologic procedure deliver majority, approximately 75%, of the collective effective dose:
I: CT
II: Nuclear medicine
III: Conventional radiography
IV: Fluoroscopy

a. I
b. I and II
c. I, II, III
d. I, II, III and IV

A

b. I and II

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7
Q

Identify the personel dosimeter and its parts

A

Film Badge
A: Film pack
B: Envelope
C: Film
D. Film badge

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8
Q

Film badges typically have an area where the film is not covered by a metal filter or plastic and thus is directly exposed to the radiation. This ____ is used to detect medium and high-energy beta radiation that would otherwise be attenuated

A

“Open window”

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9
Q

A film badge consists of a small sealed packet of radiation sensitive film, similar to dental x-ray film, placed inside a special plastic holder that can be clipped to clothing. Radiation striking the emulsion causes a darkening of the developed film. The amount of darkening increases with the absorbed dose to the film emulsion and is measured with a ____.

A

Densitometer

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10
Q

In film badges, the film emulsion contains grains of ____, resulting in a higher effective atomic number than tissue; therefore, the dose to the film is not equal to the dose to tissue.

A

Silver bromide

Most film badges can record doses from about 100 μSv to 15 Sv (10 mrem to 1,500 rem) for photons and from 500 μSv to 10 Sv (50 mrem to 1,000 rem) for beta radiation. The film in the badge is usually replaced monthly and sent to the commercial supplier for processing. The developed film is usually kept by the vendor, providing a permanent record of radiation exposure

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11
Q

The most commonly used TLD material for personnel dosimetry is ____

A

Lithium fluoride (LiF)

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12
Q

These dosimeters can be used over a long time interval (up to 6 months if necessary) before being returned to the vendor for analysis.

A

TLD
(Thermoluminescent Dosimeters)

Some dosimeters contain storage phosphors in which a fraction of the electrons, raised to excited states by ionizing radiation, become trapped in excited states. When these trapped electrons are released, either by heating or by exposure to light, they fall to lower energy states with the emission of light. The amount of light emitted can be measured and indicates the radiation dose received by the phosphor material.

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13
Q

Name the dosimeter

A

Finger ring dosimeter

TLDs are routinely used in nuclear medicine as extremity dosimeters; a finger ring containing a chip of LiF worn on the hand is expected to receive the highest exposure during radiopharmaceutical preparation and administration.

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14
Q

Name the parts of the TLD

A
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15
Q

These dosimeters are similar to that of TLDs, except that the release of trapped electrons and light emission are stimulated by laser light instead of by heat

A

Optically stimulated luminance (OSL)

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16
Q

T/F: OSL dosimeters have certain advantages over TLDs in that they can be reread several times and an image of the filter pattern can be produced to differentiate between static (i.e., instantaneous) and dynamic (i.e., normal) exposure

A

True

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17
Q

Dosimeters of choice when longer dose assessment intervals (e.g., quarterly) are required

A

TLDs or OSLs

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18
Q

It is a relatively new technology in which a nonvolatile analog memory cell, surrounded by a gas-filled ion chamber, is used to record radiation exposure

A

Direct ion storage dosimeters

The initial interactions of the x-ray and gamma-ray photons occur in the wall material, and secondary electrons ionize the gas of the chamber. The positive ions are collected on a central negative electrode resulting in a reduction in voltage that is proportional to the dose received by the dosimeter. The dose recorded by the dosimeter can be read at any time by connecting it to the USB port of any computer with Internet access.

The advantages of this technology include a broad dose and photon energy response range (0.01 mSv to 5 Sv and 5 keV to 6 MeV), unlimited real-time dose readings by the user without the need for a special reader, online management of dosimeter assignment and dosimetry reports, and elimination of the periodic distribution and collection of dosimeters as well as the delay and cost associated with returning the dosimeters for processing by the dosimetry vendor

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19
Q

Identify the dosimeter

A
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20
Q

T/F: A dosimeter is typically worn on the part of the torso that is expected to receive the largest radiation exposure or is most sensitive to radiation damage

A

True

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21
Q

Most radiologists, x-ray technologists, and nuclear medicine technologists wear a dosimeter at ____ or ____ level

A

Waist
Shirt-pocket

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22
Q

During fluoroscopy, a dosimeter is typically placed at ____ level ____ (underneath or in front?) of the lead apron to measure the dose to the thyroid and lens of the eye because most of the body is shielded from exposure

A

Collar
In front

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23
Q

Alternatively, a dosimeter can be placed at the ____ level ____ of the radiation-protective apron, and a second dosimeter can be worn on the ____ level ____ the apron

A

Collar, in front
Torso, underneath

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24
Q

A pregnant radiation worker typically wears an additional dosimeter at ____ level ( ____ the lead apron, if worn) to assess the fetal dose.

A

Waist, behind

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25
Q

The only pesonnel monitoring device with permanent record of radiation exposure

A

Film badge

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26
Q

The only pesonnel monitoring device which can measure gamma rays

A

Pocket dosimeter

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27
Q

Identify the device

A

Pocket dosimeter

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28
Q

These are used to detect the presence and provide semiquantitative estimates of the intensities of radiation fields

A

Geiger-Mueller survey instruments

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29
Q

These are used when accurate measurements of radiation exposure rates are required

A

Portable ionization chamber survey meters

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30
Q

ICRP means

A

International Commission on Radiological Protection (ICRP)

31
Q

This principle states that any decision that alters the radiation exposure situation, for example, by introducing a new radiation source or by reducing existing exposure, should do more good than harm, that is, yield an individual or societal benefit that is higher than the detriment it causes.

A

Justification

32
Q

This principle ensures the selection of the best protection option under the prevailing circumstances, that is, maximizing the margin of good over harm

A

Optimization

Optimization involves keeping exposures as low as reasonably achievable (ALARA), taking into account economic and societal factors.

33
Q

This principle states that in planned situations, the total dose to any individual from all the regulated sources should not exceed the appropriate regulatory limits

A

Limitation of maximum dose

34
Q

This is the only principle recommended by ICRP to not apply to medical exposure of patients or emergency situations

A

Limitation of maximum dose

35
Q

Give the four principal methods by which radiation exposures to persons can be minimized

A

(1) Reducing time of exposure
(2) Increasing distance
(3) Using shielding
(4) Controlling contamination by radioactive material

36
Q

This law states that the exposure rate from a source of radiation decreases with increasing distance from the source, even in the absence of an attenuating material.

A

Inverse square law

37
Q

The NCRP recommends that personnel should stand at least ____ from the x-ray tube and the patient during radiography with mobile equipment

A

2 m

38
Q

Because it is often not practical to shield the technologist from the radiation emitted from the patient during a nuclear medicine exam (see “Shielding”), ____ is the primary dose reduction technique

A

Distance

39
Q

It is commonly used for shielding, because of its very high atomic number, density, and reasonable cost

A

Lead

Lead is the most commonly used material because of its high-attenuation properties and relatively low cost.

The least thickness commonly installed is 2 lb/ft2 equal to 1/32 inch or 0.79 mm

40
Q

The recommended quantity for shielding design calculations is ____, with the unit of Gy

A

Air kerma (K)

41
Q

The recommended radiation protection quantity for the limitation of exposure of people to sources of ionizing radiation is ____

A

Effective dose

It is defined as the sum of the weighted equivalent doses to specific organs or tissues (the equivalent dose to each organ or tissue being multiplied by a corresponding tissue weighting factor, wT), expressed in Sv (see Chapter 3 for definition); for protection purposes, typical levels of E are expressed in mSv.

42
Q

It is an area to which access is controlled for the purpose of radiation protection and in which the occupational exposure of personnel to radiation is under the supervision of a person responsible for radiation protection.

A

Controlled area

Controlled areas, such as procedure rooms and control booths, are usually in the immediate vicinity of the x-ray and nuclear medicine imaging devices.

The workers in controlled areas are usually radiologic technologists, nurses, radiologists, and other physicians trained in the use of ionizing radiation and whose radiation exposures are typically individually monitored

43
Q

These are most other areas in the hospital or clinic, such as offices adjacent to x-ray rooms

A

Uncontrolled areas

44
Q

NCRP Report No. 147 recommends that the shielding design goal P for controlled areas be ____ mGy per year, and that for uncontrolled areas be ____ mGy per year.

A

5, 1

Shielding design goals, P, are amounts of air kerma delivered over a specified time at a stated reference point that are used in the design and evaluation of barriers constructed for the protection of employees and members of the general public from a medical x-ray or radionuclide imaging source or sources

These are equivalent to shielding design goals, P, of 0.l mGy per week for controlled areas and 0.02 mGy per week for uncontrolled areas.

45
Q

It is the radiation passing through the open area defined by the collimator of the x-ray source

A

Useful beam

46
Q

It arises from the interaction of the useful beam with the patient, causing a portion of the primary x-rays to be redirected

A

Scattered radiation

47
Q

T/F: For radiation protection purposes scatter is considered as a separate radiation source with essentially the same photon energy spectrum (and penetrability) as the primary beam

A

True

The scattered radiation is proportional to the field size, and can be calculated as a fraction of the reference field area

48
Q

It is the radiation that emanates from the x-ray tube housing other than the useful beam

A

Leakage

The exposure due to leakage radiation is limited by FDA regulations to 0.87 mGy/h (100 mR/h) at 1 m from the tube housing when the x-ray tube is operated at the maximum allowable continuous tube current (usually 3 to 5 mA) at the maximum rated kV, typically 150 kV.

49
Q

General purpose radiographic installations produce intermittent radiographic exposures using tube potentials of ____, with the x-ray beam directed toward the patient and the image receptor.

A

50 to 150 kV

50
Q

Fluoroscopic imaging systems are typically operated over a range of ____

A

60 to 120 kV

51
Q

Mammography employs a very low kV in the range of ____

A

25 to 35 kV

52
Q

It is the time integral of the x-ray tube current in milliampereminutes over a period of 1 week (mA-min/wk)

A

Workload

53
Q

Workload distribution is a function of the kV, which is spread over a wide range of operating potentials for:
a. Extremity examinations at ____
b. Abdominal exams at ____
c. Chest exams at greater than ____

A

a. 50 to 60 kV
b. 70 to 80 kV
c. 100 kV

54
Q

The ____ for an area is defined as the average fraction of time that the maximally exposed individual is present while the x-ray beam is on

A

Occupancy factor, T

55
Q

The following belongs to areas with full occupancy level, except:
a. X-ray control rooms
b. Receptionist areas
c. Corridor doors
d. Adjacent x-ray rooms

A

c. Corridor doors

56
Q

It is found in radiographic, dedicated chest, and radiographicfluoroscopic rooms, and is designed to attenuate the primary beam to the shielding design goal.

A

Primary barrier

57
Q

It is designed to attenuate the unshielded secondary air kerma from leakage and scatter radiation to the shielding design goal (or less).

A

Secondary barrier

58
Q

T/F: For a CT scanner, all walls in the room are secondary barriers, because the detector array within the gantry is the primary radiation barrier

A

True

59
Q

Several items provide protection for staff during a fluoroscopic or radiographic imaging procedure. The first and foremost is the protective apron worn by all individuals who must work in the room when the x-ray tube is operated.

Lead equivalent thicknesses from ____ are typical

A

0.25 to 0.50 mm

60
Q

Whenever the hands must be near the primary beam, protective gloves of ____ thick lead (or greater) should be considered when use does not interfere with the dexterity required to carry out the procedure.

A

0.5-mm

Gonadal shielding should be used to protect the gonads when the shadow of the shield does not interfere with the anatomy under investigation. Because the gonadal shield must attenuate primary radiation, its thickness must be equivalent to at least 0.5 mm of lead

61
Q

The quality (effective energy) of the x-ray beam is assessed by measuring the ____

A

HVL

62
Q

Federal regulations (21 CFR 1020.32[g]) specify a minimum patient (or tabletop) to focal spot distance of ____. Furthermore, maintaining at least ____ is strongly recommended to prevent excessive radiation exposure.

A

20 cm, 30 cm

63
Q

A kV of ____ could be selected for the most obese patients.

A

140

64
Q

The k-absorption edge of iodine—where its attenuation coefficient reaches a maximum—is at about ____ keV

A

30

65
Q

For cardiac CT imaging, the following significantly reduce the dose, except:
a. Minimize the scan range
b. Use heart rate reduction
c. Prospective triggering results in lower dose than does retrospective gating
d. If one is using retrospective gating, employ ECG-gated mA modulation
e. Reduce tube voltage whenever possible to 100 kV or even 80 kV
f. All of the following can reduce the dose

A

f. AOTA

66
Q

Radiopharmaceutical used for myocardial perfusion imaging

A

Tl-201chloride

67
Q

These radiopharmaceuticals, when administered, do not require cessation of breast feeding, except:
a. Tc-99m DTPA, MDP, PYP, RBC, or GH
b. Tc-99m sulfur colloid
c. I-123OIH
d. I-123 NaI

A

d. I-123 NaI

68
Q

It is the dose equivalent to a tissue or organ over the 50 years following the ingestion or inhalation of radioactivity.

A

Committed dose equivalent (H50,T)

69
Q
A
69
Q

The sum of the external and internal doses to the entire body is called ____

A

Total effective dose equivalent (TEDE)

69
Q

a. To limit the risk of stochastic effects, the sum of the external and internal doses to the entire body, the TEDE, may not exceed ____
b. To prevent deterministic effects, the sum of the external dose and committed dose equivalent to any individual organ except the lens of the eye may not exceed ____
c. The dose limit to the lens of the eye is ____
d. The dose to the fetus of a declared pregnant radiation worker may not exceed ____ over the 9-month gestational period and should not substantially exceed ____ in any 1 month

A

a. 50 mSv (5 rem) in a year
b. 500 mSv (50 rem) in a year
c. 150 Sv (15 rem) in a year
d. 5 mSv (0.5 rem), 0.5 mSv (50 mrem)

70
Q

It is an unexpected occurrence involving death or serious physical or psychological injury, or the risk thereof

A

Sentinel event

70
Q

An acute dose of x- or gamma rays to the bone marrow exceeding ____ is usually necessary to cause the syndrome; an acute dose of about 3.5 gray will kill about half of exposed individuals without medical care; and an acute dose exceeding 10 gray will kill nearly all individuals even with medical care

A

0.5 Gy

Physics (16 decks)

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