Concepts of Radiation Protection

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Radiation quantities and units

Section 2.1

Radiation Units

Traditional Units

1.roentgen (R)

2.rad(rad)

3.rem(rem)

4.curie (Ci)

SI Units

1.air kerma(Gyor Gya)

2.gray (Gyor Gyt)

3.seivert(Sv)

4.becquerel(Bq)

SI Units

•Le SystèmeInternational d’Unités

•International System of Unit

–Adopted in 1960

–Extension of the metric system

–All branches of radiation science

•SI units and traditional units are in use today.

Exposure

•The total electrical charge per unit mass that x-ray photons with energies up to 3MeV generate in dry air at standard temperature and pressure

•Precise measurement of radiation exposure requires a device called an ionization chamber

Exposure

•Traditional unit: Roentgen (R)

•SI Unit: Air kermaexpressed in gray (Gyor Gya)

•Relationship: 1 Gy~ 115 R

•Conversions:

1 R = 1 Gydivided by 115 R

= 0.008695 GyOR 8.695 mGy

(SC35 ~8.73 mGy)

Absorbed Dose (D)

•The amount of energy absorbed per unit mass of the medium

•Absorbed energy is responsible for any biologic damage

–Amount of energy absorbed depends on the atomic number (Z) and mass density of the tissue (kg/m3)and the energy of the incident photon (keV)

Unit of Absorbed Dose

•Traditional unit: rad(radiation absorbed dose)

–1 rad= 100 ergs/g

•SI Unit: Gray (Gyor Gyt)

–1 Gy= 1 J/kg

•Relationship: 1 Gy= 100 rad

•Conversions:

1 rad= 1 Gydivided by 100 rad

= 0.01 GyOR 10 mGy

Dose Equivalence

•Takes into consideration that different types of radiation, in equal absorbed doses, cause different amounts of biologic damage

•A quality factor (Q) is used to adjust the absorbed dose value

Radiation Weighting Factor (WR)

•Chosen for each type andenergy of radiation

•Selected by national and international scientific advisory bodies (NRCP, ICRP)

•Important in radiation protection

Equivalent Dose (EqD)

•Product of average absorbed dose in Gy(D) and its radiation weighting factor (WR)

EqD= D x WR

Unit of Equivalent Dose

•Traditional unit: rem(radiation equivalent man)

•SI unit: Sieverts(Sv)

•Relationship:

1 Sv= 100 rem

•Conversions:

1 rem= 1 Svdivided by 100 rem

= 0.01 SvOR 10 mSv

Calculating Equivalent Dose

EqD= D x WR

(Sv) = (Gy) x WR

Read and study examples on P. 65 StatkiewiczSherer

Tissue Weighting Factor (WT)

•Takes into account the overall harm to each organ and tissue

•Measure of relative risk associated with irradiation of different tissues

Effective Dose (EfD)

•Provides an overall risk of exposure to ionizing radiation

•Incorporates the effect of the type of radiation used (WR), and radiosensitivityof the organ or part irradiated (WT)

Unit of Effective Dose

•Traditional unit: rem(radiation equivalent man)

•SI unit: Sieverts(Sv)

•Relationship:

1 Sv= 100 rem

•Conversions:

1 rem= 1 Svdivided by 100 rem

= 0.01 SvOR 10 mSv

Calculating Effective Dose

EfD= D x WR x WT

(Sv) = (Gy) x WR x WT

Read and study examples on P. 66 StatkiewiczSherer

Read and study Table 3-4 on P. 67 StatkiewiczSherer

Diagnostic Radiology

•X-rays are used to acquire images in diagnostic radiology therefore…

1R = 1 rad= 1 rem

1 Gya= 1 Gyt= 1 Sv

Collective Effective Dose (ColEfD)

•Radiation exposure to a population or group from low doses of radiation

•Product of average effective dose of an individual belonging to the exposed population andnumber of persons exposed

•Traditional Unit: man-rem

•SI Unit: person-sievert

Read and study example on P. 67 StatkiewiczSherer

Radiation Units

Table 3-5: SI and Traditional Unit Equivalents

P. 67 StatkiewiczSherer

Table 3-6: Summary of Radiation Quantities and Units

P. 68 StatkiewiczSherer

PERSONNEL MONITORING

Section 2.2

Personnel Dosimetry

•Refers to monitoring of individuals who are exposed to occupational radiation

–All operators of X-ray equipment

–Personnel routinely participating in radiological procedures

•Monitoring is necessary for anyone who may receive 1/20thof annual dose limit

(SC35 P. 10: 2.1.6 )

•Personnel monitoring devices are worn to ensure:

–Workers receive doses below the stated dose limits in SC35

–To monitor radiation safety practices

•Characteristics

–Lightweight and easy to carry

–Durable, ability to withstand normal daily use

–Ability to detect both small and large doses consistently and reliably

–Withstand sensible amount of heat, humidity, and pressure

–Reasonably inexpensive to purchase and maintain

Wearing the personnel dosimeter

•Radiography (no protective lead apron worn)

1.On trunk of body at level of waist, on anterior surface of the individual

2.Upper chest region at level of collar area, on anterior surface of the individual

•Fluoroscopy (protective lead apron worn)

–Mustbe worn under the apron

–“If extremities are likely to be exposed to significantly higher doses, additional dosimeters shouldbe worn at those locations on the body.” (SC35 P. 10: 2.1.7)

Personnel Dosimeters

•Types of personnel dosimeters that detect ionizing radiation

–Film badge

–Optically stimulated luminescent (OSL)

–Pocket ionization chamber

–Thermoluminescentdosimeter (TLD)

Film Badge

•Have been in use since the 1940s

•Consist of a small case with a piece of film placed between filters

–Filter material is usually aluminum and copper

–Allow estimation of the photon energy

–Filter shapes may be different in the front of the film back compared to the back of the film badge

•Uses special radiation dosimetryfilm that is predominantly sensitive to x-rays

Film Badge

•Based of the photographic effect; the ability of radiation to blacken photographic film

•The film is processed and the optical densities are read with a densitometer

•Radiation dose may be measured using a dose-density curve

–A dose-density curve is obtained by exposing a number of different films to known doses of radiation

Control Badge

•Included with each batch of film badges

•Stored in a non-ionizing area in the facility

–The optical density reading should indicate only a base plus fog (B+F) measurement

•Serves as a basis to compare the optical density readings from other badges

–Ensures false readings are not recorded

Advantages of Film Badges

•Inexpensive, easy to use and easy to process

•Mechanical integrity

•Able to differentiate between primary beam and scatter radiation exposure

•Provide a permanent record of personnel exposure

Disadvantages of Film Badges

•Are able to detect at or above 0.1 mSv(10 mrem)

–Are not sensitive to lower levels of radiation

•Susceptible to fogging caused by high temperatures and humidity

–Limited wearing period of one month

•Time required to process and compare to standard test film

Personnel Dosimeters

•Types of personnel dosimeters that detect ionizing radiation

–Film badge

–Optically stimulated luminescent (OSL)

–Pocket ionization chamber

–Thermoluminescentdosimeter (TLD)

OSL Dosimeter

•Developed in the late 1990s

•A plastic blister pack enclosing an aluminum oxide (Al2O3) strip sandwiched within a filter pack that is sealed within a light-tight black paper wrapper

–Filter material is aluminum, tin and copper

–Enables radiation energy discrimination

•Uses aluminum oxide (Al2O3) as the radiation detector

Review of Energy levels

•Valence band

–Electrons are loosely bound and are free for sharing by adjacent atoms or molecules

•Conduction band

–Electrons within this band are free to move providing they maintain a certain minimum energy

–If the electrons fall below the minimum, they return to the valence band or other vacant electron site

•Carlton and Adler

–Figure 3-10 P. 48

•Position of the valence band and conduction band

Review of Energy levels

•Forbidden band or gap

–Electrons may pass through this gap if they are energetic enough, but cannot exist within this area

•When energy is absorbed by the electrons in the radiation monitors, they [the electrons] get trapped in the forbidden band and reside there until there energy level is increased allowing them to move into the conduction band

OSL Dosimeter

•Irradiation of Al2O3→ some electrons are stimulated into an “excited” state and are trapped in the forbidden gap or band

•Processing involves laser illumination → stimulates electrons and increases there energy state therefore moving them temporarily into a higher energy level; the conduction band

•The electrons fall back into the “vacant electron site” they had previously occupied and the loss of energy causes emission of light proportional to dose received

Advantages of OSL Dosimeters

•Ability to detect a dose of 0.01 mSv(1 mrem)

•Reanalysis to confirm the dose

•Qualitative information about the exposure

•Ability to read energies from 5 keVto > 40 MeV

•May be worn for a period of one year

–Common practice; 2 month wearing period

Disadvantage of OSL Dosimeters

•OSL dosimeters are shipped to the monitor company for processing therefore do not provide immediate dose results

Pocket Dosimeter

•Resembles a large pen

•Contains an ionization chamber with an eyepiece at one end and a charging rod at the other end

–Ionization chamber contains two electrodes/fibres; one fixed and the other movable

–The movable fibre can be seen through the transparent scale (reading scale) of the eyepiece

•Special charging unit

–The pocket dosimeter is charged to a predetermined voltage so the quartz fibre indicates a zero reading

•The pocket dosimeter is charged causing the moveable quartz fibre to repel the fixed central electrode/fibre

•Exposure to radiation causes ionizations within the chamber

•The ionizations cause the moveable fibre to move closer to the fixed fibre

•The scale is read through the eyepiece providing an estimated X-ray dose

Advantages of Pocket Dosimeter

•Provides an immediate exposure reading

•Compact, easy to carry and convenient to use

–High-exposure areas i.e. cardiac catheterization procedures

•Easily recharged and reused

•Reasonably accurate and sensitive

–Sensitivity ranges from 0 to 200 mR

Disadvantages of Pocket Dosimeters

•Expensive ~ $150.00 per unit

•If not read on a timely basis may result in an inaccurate reading

•Mechanical shock may lead to false high readings

•No permanent legal record of personnel exposure

TLDs

•Appearance similar to a film dosimeter

•Contains a holder and an insert

•Insert consists of an aluminum plaque, lithium fluoride chips/powder and an identification number

–Lithium fluoride (LiF) is the radiation sensing material

–TLD chips are usually 3 mm x 3 mm x 1 mm thick

•Requires a TLD analyzer for measuring the dose received to the TLD badge

TLDs

•The TLD absorbs energy when exposed to x-rays and stores the energy in an “excited” higher state; the number of electrons that become trapped is proportional to the absorbed dose

•To measure the dose the plaque containing the LiFcrystals is placed in the TLD analyzer and exposed to increasing temperatures

•The heat frees the “trapped” electrons and alters the state of the crystal structure causing the electron to return to the valance band → light is released in the proportion to the amount of radiation absorbed

TLDs

•The amount of light released (luminescence) is measured with a photomultiplier tube or a photodiode

•The intensity of light is plotted on a glow curve

•The parameters are measured and converted to a dose

Advantages of TLDs

•LiFcrystals interact with ionizing radiation similar to soft tissue

–The Z of LiFis equal to 8.2; Z of soft tissue is 7.4

•Exposures as low as 0.05 Gyt(5 mrad) can be measured

•Withstand certain amount of heat, humidity, and pressure

•Can be worn for 3 months

•Crystals are reusable as the heating process restores the crystal to its original condition

•TLD responds proportionally to dose; if the dose is doubled the TLD response is doubled

•Instantaneous readings are possible if a department has a TLD analyzer

•TLD monitors are also used to measure patient dose

–There small size and various configurations allow them to monitor doses in a small area such as a body cavity

Disadvantages of TLDs

•High cost

•Generally are sent to a facility for analysis of dosimeter results

•Can only be read once, readout process destroys the stored information

•TLD crystals that are energy dependent need to be calibrated to the appropriate energy level they will be measuring

•TLDs do not respond to individual ionizing events; therefore cannot be used as a rate meter detection device

Dosimetry report

•Occupational exposure documentation and records are maintained;

1.Radiation safety program control and evaluation

2.Regulatory compliance

3.Epidemiological research

4.Litigation

•Report provided for each dosimeter submitted

Information on a Personnel Monitoring Report

•Group number

–Number assigned to Red River College

•Date of report

•Description of the type of service

–TLD service, Quarterly, X-ray/Gamma/Beta

•Period Start-End (1)

–The wearing period start and end dates

•Dosimeter serial # (2)

Information on a Personnel Monitoring Report (2)

•Full name (3)

–Surname, First given name, Second given name

•Multiple Group (4)

–“Yes” indicates person is active in more than one group. Cumulative totals are all inclusive. Blank indicates person is active in one group only.

•Type/Location (5)

–Dosimeter type and wearing location

Information on a Personnel Monitoring Report (3)

•Current dose (6)

–Current period dose

•Cumulative dose (mSv) Year (7)

–Cumulative dose for current year

•Cumulative dose (mSv) Life (8)

–Cumulative dose for life time

•Anomaly

–*See descriptions at the end of the report for details

Additional information

•StatkiewiczSherer6thEdition

–P. 84 –85 Table 4-2 “ Advantages and Disadvantages of Personal Dosimeters”

–P. 76 Fig. 4-6 “Personnel monitoring report…”

Radiation detection and measurement

Section 2.3

 

Introduction

•Instruments used to measure cumulative radiation intensity are called radiation dosimeters

•Instruments used to detect radiation are called radiation detection devices

Methods of Detection

•Radiation may be detected by the following methods

–Ionization

–Photographic effect

–Luminescence

–Scintillation

Ionization

•Ionization chamber

–Gas filled chamber, negative and positive electrodes, dc amplifier, and an electrometer

•Radiation produces ion pairs → ions attracted to opposite electrodes → flow of electrons is a measure of radiation intensity

•Measures radiation by detecting the number of ionizations within a known volume of air

–Refer to Concepts of Radiation Protection –Information Sheet 2.1

•Measures either the total quantity of electrical charge orthe rate the electrical charge is produced

•E.g. Cutie pie, proportional counter, and the Geiger-Muller (GM) detector

•Used in areas around a fluoroscope, radionuclide generators and syringes, vicinity of NM or therapy patients, outside of protective barriers, and for precise calibration of diagnostic x-ray equipment

Calibration Instruments

•Used to calibrate radiographic and fluoroscopic x-ray equipment

•The ionization chamber is connected to an electrometer

–Both the ionization chamber and the electrometer must be periodically calibrated to meet provincial and federal requirements

•Used by medical physicists to perform standard measurements, i.e. x-ray output (mR), reproducibility and linearity of output etc.

Proportional Counter

•Proportional counters are sensitive instruments, generally used in laboratory settings to detect small quantities of radioactivity

–Proportional counters detect alpha and beta radiations

Geiger-Muller Detector

•Used for contamination control in nuclear medicine laboratories

–A portable instrument may be used to detect the presence of radioactive contamination on work surfaces and laboratory apparatus

•Very sensitive instruments able to detect one ionizing event

–May be equipped with audio amplifier and a speaker therefore allowing one to hear the crackle of individual ionizations

Radiation Survey Instruments: Requirements

1.Easy to carry enabling one person to efficiently operate the device

2.Durable to withstand normal use

3.Must be reliable

4.Interact with ionizing radiation in a similar manner to how human tissue reacts

5.Should be able to detect all common types of ionizing radiation

6.The energy nor the direction of the incident radiation should not affect the units performance

7.Cost effective including maintenance charges

Methods of Detection –Discussion

•Radiation may be detected by the following methods;

–Ionization

–Photographic effect

–Luminescence

–Scintillation

RADIATION PROTECTION ORGANIZATIONS

Section 2.4

Introduction

•Safety standards, recommendations and guidelines in place today are based on the work of various radiation protection organizations throughout the world

•Organizations are divided, and serve either internationalor nationalfunctions

•Organizations may focus on:

–Biological Effects of Radiation

–Radiation Protection

International Organizations

1.ICRP

2.UNSCEAR

3.NAS/NRC-BEIR

4.RERF

ICRP

•International Commission on Radiological Protection

•Established : 1928

•Provides recommendationson occupational and public dose limits.

•Recommendations are based on research and findings from various research councils. i.e. BEIR

UNSCEAR

•United Nations Scientific Committee on the Effects of Atomic Radiation

•Established:1955

•Examines the risks and responses of human and environmental radiation.

•Makes predictions about the incidence of biological effects among the general population.

NAS/NRC-BEIR

•National Academy of Sciences/National Research Council on the Biological Effects of Ionizing Radiation

•Established in 1963

•Serves to advise agencies and governments of the health effects of radiation exposures

•Publishes reports on the most current studies and findings.

RERF

•Radiation Effects Research Foundation

•Established:1950’s

•Members: Gov’tof Japan

•Studies the survivors of atomic bombs at Hiroshima and Nagasaki

•Publishes results of studies/research.

National Organizations

1.CRPA

2.CNSC

3.RPB-HC

CRPA

•Canadian Radiation Protection Association

•Established:1982

•Promotes research, scientific study and educational opportunities in radiation protection.

CNSC

•Canadian Nuclear Safety Commission

•Established: 2000

•Federal regulator of nuclear facilities and materials in Canada

•Responsible for setting dose limits to protect workers [nuclear power workers and medical personnel working with ionizing radiation] from overexposure

•Also sets dose limits to ensure the general public is not overexposed to radiation from licensed nuclear facilities or substances in Canada

RPB-HC

•Radiation Protection Bureau-Health Canada

•Provides medical and technical advice

•Coordinates Canada’s preparedness for nuclear emergencies

•Houses the Canadian Radiological Monitoring Network and Laboratory

•National DosimetryServices

–Provides personal radiation monitoring to 100,000 Canadians using ionizing radiation in their work

•National Dose Registry

–A centralized radiation dose record system, which contains the occupational radiation dose records of all monitored radiation workers in Canada.

RPB-HC Publications

•Safety Code 35: Radiation Protection in Radiology –Large Facilities: Safety Procedures for the Installation, Use and Control of X-ray Equipment in Large Medical Radiological Facilities

•Major objectives:

•Minimize patient exposure to ionizing radiation while ensuring diagnostic information

•Ensure adequate protection of personnel

•Ensure adequate protection of other personnel and the general public

Health Canada Publications:RED Act

•Radiation Emitting Devices Act

•Serves to regulate any radiation emitting equipment in Canada

•SC35 Appendix VI: Radiation Emitting Devices Regulations for Diagnostic X-ray Equipment

Safety Code 35: Terminology

•Must: indicates a requirement that is essential to meet currently accepted standards of protection

•Should: indicates an advisory recommendation that is highly desirable and is to be implemented where applicable

Example of Terminology

•4.1Protective Equipment (P. 35)

5.Protective gonad shields for patients musthave a lead equivalent of at least 0.25 mm Pband shouldhave a lead equivalent thickness of 0.5 mm at 150 kVp.

Provincial Organizations

•Radiation Protection Services:

Department of Medical Physics, CancerCareManitoba

•Ensures operational compliance with:

–The Manitoba Regulation 341/88R:

X-ray Safety Regulation –Public Health Act

–RED Act

–SC35

Radiation Protection Services:CancerCareManitoba

•Services:

–Equipment registrations

–Shielding inspections

–X-ray equipment survey and inspection

–Radiation Protection Reports

–Radiation Monitor Service

–Education and Consulting

RADIATION-INDUCED RESPONSES AND GOALS OF RADIATION PROTECTION

Section 2.5

Biologic Effects of Ionizing Radiation

•Somatic effects

–Occur in the body of the irradiated person

–Importance of good safety practices

•Genetic effects

–Damage sustained by an individual’s germ cells that is transferred to their offspring

–Importance of gonad protection

Categories of Radiation-Induced Responses

1.Deterministic (nonstochastic) effects

2.Stochastic effects

1.Deterministic Effects

•A.k.anonstochasticeffects

–Biologic somatic effects directly related to the radiation dose received

–A threshold exists below which no biological damage is observed

–Above the threshold dose the severity of the effect increases with increasing dose

–Generally, high radiation doses are required to produce deterministic effects

Early Deterministic Effects

–Erythema

–Leukocytopenia

–Epilation

•More serious early deterministic effects are noted after very high levels of radiation exposure

–Acute radiation syndromes

 

Late Deterministic Effects

•These effects may be observed months or even years after high levels of radiation exposure

–Cataract formation

–Fibrosis

–Organ atrophy

–Loss of parenchymalcells

–Reduced fertility

–Sterility

Stochastic Effects

•Described as “mutational, nonthreshold, randomly occurring biologic somatic effects…”

•The severity of the effect is notdose dependent

•Based on probability, therefore with each successive exposure the probability of sustaining a stochastic effect increases

•Examples of stochastic effects are cancer and genetic damage

•Stochastic events are termed “all-or-nothing” responses

•There is no minimal safe dose

–This explains the concern of the increased use of ionizing radiation (i.e. CT scans) to the general population

Occurrence of Radiation-induced Malignancy

•To develop cancer it is the somatic cells that absorb the dose

–The dose may be 0.5 Gy or 2 Gy, either has the potential of causing radiation induced cancer

–The cancer will not be more severe if 2 Gy of radiation was absorbed versus 0.5 Gy

–However, the probability of radiation induced cancer would be greater at 2 Gy versus 0.5 Gy

Damage to Reproductive Cells

•When ionizing radiation is absorbed in the germ cells (ova/sperm), mutations may occur with the potential of negative affects on future generations

Risk of Cancer Induction

•Data used when assessing the risk of cancer induction has been from groups who were exposed to high doses of radiation (i.e. atomic bomb survivors)

•Estimates have been extrapolated from high dose data to determine the effects from low-level ionizing radiation exposure

•Consideration to the naturally occurring risks of cancer, birth defects and genetic mutations

ALARA Concept

•ICRP Publication No. 37 and Publication No. 55 referred to ALARA as “optimization”

•By practicing ALARA the doses received by occupational and non-occupational workers is well below the allowable dose limits

•The model (dose-response curve) used in the ALARA concept depicts no threshold dose therefore overestimating the risk of injury

Objectives of Radiation Protection

1.To prevent any clinically significant radiation-induced deterministic effects

–This may be achieved by adhering to the dose limits based on recommendations by ICRP, specified in ICRP Publication 60

2.To limit the risk of stochastic responses to a moderate level

–This may be achieved by ensuring justification and optimization for every x-ray examination ordered

Current Philosophy

•Assumption of a linear, nonthresholdrelationship between ionizing radiation dose and biological response

–There is no known safe level of radiation dose

•The premise that ionizing radiation posses both a beneficial and a destructive potential

–The benefit of exposure to ionizing radiation must outweigh the potential risk

Information Sheet 1.2

RADIATION EXPOSURE RISK AND DOSE LIMITS

Section 2.6

Risk

•Any exposure to ionizing radiation has risk associated with that exposure

•One way to illustrate that risk is to compare a dose received during a certain diagnostic examination to a comparable dose received by background radiation

–BERT = Background Equivalent Radiation Time

•Another way to evaluate risk is to compare radiation workers with other “risky conditions”

–Smoking cigarettes, driving “fast”, having heart disease, etc.

ICRP Recommendations

•In 1991 ICRP recommended that the annual dose limit for radiation workers be lowered from 50 mSvto 20 mSv

–This decision was made based on new information obtained from the Japanese atomic bomb survivors

–Damage was determined to be 3 –4 times greater than previously estimated

•SC 35 has incorporated the new 20 mSvannual dose limit for radiation workers

Research

•The BEIR V report adopted the linear no-threshold view based on extrapolated data from atomic bomb survivors who received doses > 0.5 Sv(50 rem)

–Recall that annual natural radiation doses average 2.5 mSvin Canada and 3.3 mSvUSA

•The RERF has determined that atomic bomb survivors have received an apparent threshold dose of 0.2 and 0.5 Sv

•The doses of 0.2 and 0.5 Svcorrespond to the average natural radiation received in a persons lifetime

•Research has demonstrated that atomic bomb survivors that have been exposed to moderate levels of radiation (5 mSvto 50 mSvequivalent to 1½ to 15 years of natural radiation exposure) have a reduced cancer rate when compared to the normally exposed control population

•The data collected by RERF appear to contradict the BEIR V report which suggests that any amount of radiation has the potential to be harmful

•Other studies that have been conducted draw similar conclusions i.e. lower cancer rates in individuals exposed to higher levels of radiation

Radiation Hormesis

•These studies suggest a beneficial consequence of moderate radiation exposure (2 or 3 times natural radiation levels)

•The explanation for such a phenomenon suggests that radiation stimulates hormonal and immune responses to other toxic environmental agents responsible for cancer induction

•The radiation hormesis theory is yet to be proven

•Therefore MRTs must continue to practice ALARA as an ethical approach to managing radiation exposure

SC35: APPENDIXI

Applicable Body Organ or Tissue Radiation Workers (mSv) Members of the Public (mSv)
Whole Body 20 1
Lens of the eye 150 15
Skin 500 50
Hands 500 50
All other organs 500 50

Table AI.1 suggests maximum values. All doses must be kept ALARA and any unnecessary radiation exposure must be avoided

SC35: Appendix I

•There is no recommended discrimination in dose limits between men and women of reproductive capacity (11 to 55 years)

•Technologist-in-training and students must adhere to the dose limits of the general public

•Some provincial or territorial jurisdictions may have different dose limits for some radiation workers; consult Appendix V

•Once pregnancy has been declared by an RTR, the foetus must be protected from X-ray exposure for the duration of the pregnancy

–Effective dose limit of 4 mSvfor remainder of the pregnancy from all sources of radiation

–Occupational exposure to pregnant RTRs generally arise form scatter radiation. Foetal monitoring may be accomplished by placing a TLD on the surface of the abdomen

SC35: Section A: Responsibilities and Protection

1.0Responsibility of Personnel

–All personnel considered to have responsibility for radiation safety must work together for optimal results

1.1Owner

1.2Responsible user

1.3X-ray equipment operator

1.4Medical physicist/Radiation safety officer

1.5Referring physician / Practitioner

1.6Information systems specialist

1.7Repair and maintenance personnel

1.1Owner (P. 7)

–Ultimately responsible for the radiation safety of the facility

–Must ensure the equipment and facility meet applicable radiation standards

–Must ensure a radiation safety program is developed, implemented and maintained for the facility

–May delegate these responsibilities to qualified staff

1.2Responsible user (P. 7: 1-11)

–Main role is to monitor and manage the safety program of the facility including

•Personnel requirements

•Equipment performance and safety procedures

•Communicate safety program information

–There must be at least one person designated as a responsible user

–If the responsible user performs examinations on patients then all requirements listed in 1.3 also apply

1.3X-ray equipment operator (P. 8: 1-11)

–Must carry out requested radiological procedures in a manner that minimizes unnecessary exposure to the patient, themselves and other workers

–Physician, physician/practitioner or a radiation technologist may be considered X-ray equipment operators

1.4Medical Physicist/Radiation Safety Officer (P. 8-9: 1-17)

–Act as an advisor on all radiation protection aspects during initial construction stages, installation of the equipment and during ensuing operations

•Medical physicist is a HCP with specialized training in medical applications of physics

•Radiation Safety Officer (RSO) title assigned to a radiation safety specialist who manages the facilities radiation protection program

1.5Referring Physician/Practitioner (P. 9: 1-4 and 1 –2)

–The individual authorized to prescribe diagnostic or interventional X-ray procedures

–Must ensure the X-ray is justified

–Some jurisdictions authorise a registered nurse or nurse practitioner to order X-rays

1.6Information System Specialist (P. 9-10: 1-7)

–Facilities that perform digital image processing should have access to a trained individual specializing in information technology software and hardware (required for PACS and teleradiology)

•Individual may be on-site or available upon request

–Information system specialist must ensure confidentiality of patient records

1.7Repair and Maintenance Personnel (P. 10: 1-7)

–Authorized to perform hardware and software repairs and maintenance on X-ray generators, control systems, imaging systems and their operating software

•Individual may be on-site or available upon request

•May be contracted to an outside organization or equipment manufacturer

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2 thoughts on “Concepts of Radiation Protection

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    June 26, 2014 at 6:50 am

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    bash said:
    May 12, 2014 at 2:14 am

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