05. Occupational protection - Radiation Protection of Patients

IAEA Training Material on Radiation Protection in Nuclear Medicine

Part 5

Occupational Exposure

Protection of the Worker

Occupational Exposure

Definition

All exposures of workers incurred in the course of their work, with the exception of exposures excluded from the Standards and exposures from practices or sources exempted by the Standards

2 Nuclear Medicine Part 5. Occupational Protection

Objective

To become familiar with the BSS detailed requirement and the Safety Guide on occupational exposures for radiation protection of workers in nuclear medicine

Nuclear Medicine Part 5. Occupational Protection 3

Nuclear Medicine

Contents

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 Responsibilities and conditions of service

Classification of areas

Sources of exposure

Safe handling of sources

Monitoring

Emergency procedures

Local rules and supervision

Health surveillance

Records

Part 5. Occupational Protection 4

IAEA SAFETY STANDARDS

BSS:

Interim Version 2011


The System of Protection and

Safety: BSS (2011)

These Standards are based on the following safety principles:

• Responsibility for safety

• Role of Government

• Leadership and Management for safety

• Justification of Facilities and Activities

• Optimization of Protection

• Limitation of Risks to Individuals

• Protection of present and future generations

• Prevention of Accidents

• Emergency Preparedness and Response

• Protective actions to reduce existing or unregulated radiation risks



Part 5. Occupational Exposure


Module 5.1. Responsibilities

Responsibility for Safety:

BSS 1.8 (2011)

• The prime responsibility for safety must rest with the person or organization responsible for facilities and activities that give rise to radiation risks.

• Other parties also bear certain responsibilities. For instance, suppliers of radiation generators and radioactive sources have responsibilities in relation to the design and manufacture and operating instructions for their safe use.

• Health professionals may be involved in the preparation for, and the conduct of, radiological procedures, and each type has specific responsibilities, as established in these

Standards.


Role of Government:

BSS 1.9 (2011)

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A properly established governmental, legal and regulatory framework for safety provides for the regulation of facilities and activities that give rise to radiation risks.

There is a hierarchy of responsibilities within this framework, from governments to regulatory bodies to the organizations responsible for and the persons engaged in activities involving radiation exposure.

The government is responsible for the adoption within its national legal system of such legislation, regulations, and standards and measures as may be necessary to fulfil all its national and international obligations effectively, and for the establishment of an independent regulatory body.

In some cases, more than one governmental organization may have the functions of a regulatory body for activities within their jurisdictions relating to the control of radiation and radioactive material


Role of Government:

BSS 1.10 (2011)

 Both the government and the regulatory body have important responsibilities in establishing the regulatory framework for protecting people and the environment from harmful effects of radiation, including establishing standards.

 These standards require the government to ensure that there is coordination of government departments and agencies that have responsibilities for protection and safety.


Role of Government:

BSS 1.11 (2011)

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The government is also responsible for ensuring, as necessary, that provision is made for support services such as education and training, and technical services.

If these services are not available within the State, other mechanisms to provide them may have to be considered.

The regulatory body is responsible for carrying out its required regulatory functions, such as the establishment of requirements and guidelines, the authorization and inspection of facilities and activities, and the enforcement of legislative and regulatory provisions.


Responsibilities of the regulatory body to occupational exposure

Requirement 19: BSS (2011)

 The government or regulatory body shall establish and enforce requirements to ensure that protection and safety is optimized, and the regulatory body shall enforce compliance with dose limits for occupational exposure.




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3.69. The government or regulatory body shall establish the responsibilities of employers, registrants and licensees with regard to application of the requirements for occupational exposure in planned exposure situations.

3.70. The government or regulatory body shall establish and enforce requirements to ensure that protection and safety is optimized for occupational exposure.

3.71. The government or regulatory body shall establish and the regulatory body shall enforce compliance with the dose limits specified in Schedule III for occupational exposure.




 3.72. Before authorization of a new or modified practice, the regulatory body shall require, as appropriate, and review supporting documents from the responsible parties that state:

(a) design criteria and design features relating to the exposure and potential exposure of workers in all operational states and accident conditions;

Nuclear Medicine

(b) design criteria and design features of the appropriate systems and programmes for monitoring of workers for occupational exposure in all operational states and accident conditions .


Requirements for monitoring and recording of occupational exposure


 The regulatory body shall establish and enforce requirements for the monitoring and recording of occupational exposures in planned exposure situations.




 3.73. The regulatory body shall be responsible, as appropriate, for:

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

 a) Establishment and enforcement of requirements for the monitoring, recording and control of occupational exposures in planned exposure situations in accordance with the requirements of these Standards;

(b) Review of monitoring programmes of registrants and licensees, which shall be adequate to ensure that the requirements with regard to occupational exposure in planned exposure situations are met;

(c) Authorization or approval of service providers for individual monitoring and calibration services;




 3.73. The regulatory body shall be responsible, as appropriate, for:

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(d) Review of periodic reports on occupational exposure

(including results of monitoring programmes and dose assessments) submitted by employers, registrants and licensees;

(e) Provision for maintaining exposure records and results of the assessment of doses from occupational exposure;

(f) Verification of compliance of an authorized practice with the requirements on the control of occupational exposure


Responsibilities of employers, registrants and licensees for the protection of workers


 Employers, registrants and licensees shall be responsible for the protection of workers against occupational exposure. Employers, registrants and licensees shall ensure that protection and safety is optimized and that the dose limits for occupational exposure are not exceeded.




 3.74. For workers who are engaged in activities in which they are or could be subject to occupational exposure in planned exposure situations, employers, registrants and licensees shall be responsible for:

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

(a) Protection of workers against occupational exposure;

(b) Compliance with other relevant requirements of these

Standards.

 3.75. Employers who are also registrants or licensees shall have the responsibilities of both employers and registrants or licensees .




 3.76. Employers, registrants and licensees shall ensure, for all workers engaged in activities in which they are or could be subject to occupational exposure, that:

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(a) Occupational exposure is controlled so that the relevant dose limits for occupational exposure specified in Schedule

III are not exceeded;

(b) Protection and safety is optimized in accordance with the requirements of these Standards;

(c) Decisions with regard to measures for protection and safety are recorded and made available to relevant parties, through their representatives where appropriate, as specified by the regulatory body;



Requirement 21: BSS (2011) contd..

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(d) Policies, procedures and organizational arrangements for protection and safety are established for implementing the relevant requirements of these Standards, with priority given to design measures and technical measures for controlling occupational exposure;

(e) Suitable and adequate facilities, equipment and services for protection and safety are provided, the type and extent of which are commensurate with the expected likelihood and magnitude of the occupational exposure;

(f) Necessary health surveillance and health services for workers are provided;

 (g) Appropriate monitoring equipment and personal protective equipment are provided and arrangements are made for its proper use, calibration, testing and maintenance;

 (h)



Requirement 21: BSS (2011) contd …

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(h) Suitable and adequate human resources and appropriate training in protection and safety are provided, as well as periodic retraining as required to ensure the necessary level of competence;

(i) Adequate records are maintained in accordance with the requirements of these Standards;

(j) Arrangements are made to facilitate consultation of and cooperation with workers with regard to protection and safety, through their representatives where appropriate, on all measures necessary to achieve the effective application of these Standards;

(k) Necessary conditions for promoting a safety culture are provided.




 3.77. Employers, registrants and licensees shall:

 (a) Involve workers, through their representatives where appropriate, in optimization of protection and safety;

 (b) Establish and use, as appropriate, constraints as part of optimization of protection and safety.

 3.78. Employers, registrants and licensees shall ensure that workers exposed to radiation from sources within a practice that are not required by or directly related to their work have the same level of protection against such exposure as members of the public.




 3.79. Employers, registrants and licensees shall take such administrative actions as are necessary to ensure that workers are informed that ensuring protection and safety is an integral part of a general occupational health and safety programme in which they have specific obligations and responsibilities for their own protection and the protection of others against radiation exposure and for the safety of sources.




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3.80. Employers, registrants and licensees shall record any report received from a worker that identifies circumstances that could affect compliance with the requirements of these Standards, and shall take appropriate action.

3.81. Nothing in these Standards shall be construed as relieving employers from complying with applicable national and local laws and regulations governing hazards in the workplace.

3.82. Employers, registrants and licensees shall facilitate compliance by workers with the requirements of these

Standards.



Compliance by Workers


 Workers shall fulfil their obligations and carry out their duties for protection and safety.

 3.83. Workers:

 (a) Shall follow any applicable rules and procedures for protection and safety as specified by the employer, registrant or licensee;

 (b) Shall use properly the monitoring equipment and personal protective equipment provided;

 (c) Shall cooperate with the employer, registrant or licensee with regard to protection and safety, and programmes for workers’ health surveillance and programmes for dose assessment;




 (d) Shall provide to the employer, registrant or licensee such information on their past and present work that is relevant for ensuring effective and comprehensive protection and safety for themselves and others;

 (e) Shall abstain from any wilful action that could put themselves or others in situations that would not be in accordance with the requirements of these Standards;

 (f) Shall accept such information, instruction and training in protection and safety as will enable them to conduct their work in accordance with the requirements of these

Standards.




 3.84. A worker who identifies circumstances that could adversely affect protection and safety shall report such circumstances to the employer, registrant or licensee as soon as possible.


Workers Responsibilities

“Workers shall:

• follow any applicable rules for protection

• use properly the monitoring devices and the protective equipment and clothing provided

• co-operate with the licensee with respect to protection”


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Cooperation between employers and registrants and licensees


Employers and registrants and licensees shall cooperate to the extent necessary for compliance by all responsible parties with the requirements for protection and safety.

3.85. If workers are engaged in work that involves or that could involve a source that is not under the control of their employer, the registrant or licensee responsible for the source and the employer shall cooperate to the extent necessary for compliance by both parties with the requirements of these

Standards.





Module 5.2. Classification of Areas

CLASSIFICATION OF AREAS

• Controlled area

• Supervised area



Arrangements under the radiation protection programme: Employers, registrants and licensees shall establish and maintain organizational, procedural and technical arrangements for the designation of controlled areas and supervised areas, for local rules and for monitoring of the workplace, in a radiation protection programme for occupational exposure.


Classification of Areas:

Controlled Area

“3.88. Registrants and licensees shall designate as a controlled area any area in which specific measures for protection and safety are or could be required for:

(a) controlling exposures or preventing the spread of contamination in normal operation;

(b) preventing or limiting the likelihood and magnitude of exposures in anticipated operational occurrences and accident conditions.

3.89. In determining the boundaries of any controlled area , registrants and licensees shall take account of the magnitudes of the exposures expected in normal operation, the likelihood and magnitude of exposures in anticipated operational occurrences and in accident conditions, and the type and extent of the procedures required for protection and safety.”


Controlled Area

“3.90. Registrants and licensees:

(a) Shall delineate controlled areas by physical means or, where this is not reasonably practicable, by some other suitable means;

(b) Shall, where a source is only intermittently brought into operation or energized, or is moved from place to place, delineate an appropriate controlled area by means that are appropriate under the prevailing circumstances and shall specify exposure times;

(c) Shall display the symbol recommended by the International

Organization for Standardization (ISO) and shall display instructions at access points to and at appropriate locations within controlled areas;

(d) Shall establish measures for protection and safety, including, as appropriate, physical measures to control the spread of contamination and local rules and procedures for controlled areas;

(e) Shall restrict access to controlled areas by means of administrative procedures such as the use of work permits, and by physical barriers, which could include locks or interlocks, the degree of restriction being commensurate with the likelihood and magnitude of exposures;”


Controlled Area

(f) Shall provide, as appropriate, at entrances to controlled areas:

(i) Personal protective equipment;

(ii) Equipment for individual monitoring and workplace monitoring;

(iii) Suitable storage for personal clothing;

(g) Shall provide, as appropriate, at exits from controlled areas:

(i) Equipment for monitoring for contamination of skin and clothing;

(ii) Equipment for monitoring for contamination of any objects or material being removed from the area;

(iii) Washing or showering facilities and other personal decontamination facilities;

(iv) Suitable storage for contaminated personal protective equipment;

(h) Shall periodically review conditions to assess whether there is any need to modify the measures for protection and safety or the boundaries of controlled areas;

(i) Shall provide appropriate information, instruction and training for persons working in controlled areas.”


Classification of Areas:

Supervised Area

“3.91. Registrants and licensees shall designate as a supervised area any area not already designated as a controlled area but for which occupational exposure conditions need to be kept under review, even though specific measures for protection and safety are not normally needed.

3.92. Registrants and licensees, taking into account the nature, likelihood and magnitude of exposures or contamination in the supervised areas:

(a) Shall delineate the supervised areas by appropriate means;

(b) Shall display approved signs, as appropriate, at access points to supervised areas;

(c) Shall periodically review conditions to assess whether there is any need for further measures for protection and safety or any need for changes to the boundaries of supervised areas.”


Nuclear Medicine

Classified Areas

Should be defined by the RPO and RPC

Controlled areas:

• Room for preparation of radiopharmaceuticals

• Room for dispensing radiopharmaceuticals

• Room for storage of radionuclides

• Room for storage of radioactive waste

• Room for administration of radiopharmaceuticals

• Imaging rooms, if or when administration is done

Supervised areas:

• The whole department


…...appropriate instructions at access points


…..display a warning symbol


WORK IN CONTROLLED AREA

1 Access to controlled areas must be limited to essential staff , patients and other personnel as may be authorized by the Head of Department.

Anyone entering a controlled area must follow these rules.

2 All staff who regularly work in controlled areas will be issued a personal dosimeter which must be worn whenever they enter a controlled area.

3 The occasional entry to a controlled area of any other person not wearing a dosimeter (e.g. patients' relatives or escorts) may be permitted provided that they remain under the supervision of an authorized member of staff.

4 Other people who need to enter a controlled area on an occasional basis at times when they are not under the supervision of an authorized member of staff (e.g. works staff or contractors working outside normal hours) must be issued with a 'Permit to enter a controlled area' .

5 Outside normal working hours controlled areas must be locked to prevent unauthorized access.



6 To avoid skin contamination and/or accidental ingestion of radionuclides: a) laboratory coats or other suitable clothing should be worn to prevent accidental contamination of normal clothes; b) disposable plastic gloves should be worn when working with any unsealed source (e.g. preparing radiopharmaceuticals, drawing up a dose or giving an injection); c) laboratory coats should be removed and hands washed before eating or drinking and before going home; d) disposable paper handkerchiefs should be used; e) skin cuts and abrasions should be covered before working with unsealed sources; f) if there is any risk of splashing, eyes should be protected (e.g. behind the transparent door of the laminar flow cabinet); g) mouth pipettes must never be used. Always use a bulb pipette or a syringe for measuring radioactive solutions;



h) no one should eat, drink, smoke or apply cosmetics in controlled areas with the following exceptionsi) eating and drinking by a patient as part of a diagnostic procedure, ii) in the nursing station patients and escort staff may eat provided that no administration of radioactive substances is being carried out at the time and any contamination from previous administrations has been dealt with by a suitably qualified member of staff, iii) in the waiting room patients, escorts and accompanying persons may normally eat and drink; there should be no radioactive contamination hazard because the area must not be used for administration of radioactive substances.

However, if contamination has occurred (e.g. if a patient vomits or leaks urine or other body fluid after the radiopharmaceutical has been administered) then the area must be considered to be 'Controlled' under the regulations relating to internal hazard and no-one may eat or drink until it has been decontaminated and/or monitored and pronounced safe by a suitably trained member of staff.



7 To avoid spread of contamination : a) activity must not be splashed around (e.g. do not squirt syringes to expel the air); b) as far as is practicable all operations involving unsealed sources should be carried out over a drip tray; c) syringes containing radioactive solutions should be placed, with their shielding, in a tray before being transported; d) any bench top which is used for the manipulation of unsealed sources (e.g. blood samples) should be covered with absorbent paper which should be replaced if contamination occurs; and e) while wearing gloves which may be contaminated, unnecessary contact with all other objects should be avoided.

Gloves should be removed and disposed of in the radioactive waste bin as soon as work with radioactive substances is finished.



8 To minimize the hazard from external radiation: a) sources must be kept within suitable lead shielding when not in use. Vials of activity should only be removed from their lead pots when this is absolutely necessary (e.g. to place in the ionization chamber); b) unshielded vials of activity should only be manipulated with long handled tongs ; c) syringes containing radioactivity should be fitted with lead syringe shields whenever possible; d) patient doses should be kept in the shielded storage area until required. Unused doses should be returned to the radionuclide laboratory at the end of each session; and e) personnel should keep as far away as possible from all sources and organize work so as to minimize the time spent in close proximity to large sources , (e.g. stand back while the 99m Tc generator is eluting).





Module 5.3. Sources of Exposure

EXPOSURES IN NUCLEAR MEDICINE

Internal

Ingested and/or inhaled radionuclides

External

Vials, syringes, patients.


Optimization of Protection

Risk Dose

Unacceptable Limit for workers

Source related constraints

Tolerable

Optimized working procedures

Nuclear Medicine

Acceptable Occupational exposure


Exposure of the Worker

Unpacking radioactive material

Activity measurements

Storage of sources

Internal transports of sources

Preparation of radiopharmaceuticals

Administration

Examination of the patient

Care of the radioactive patient

Handling of radioactive waste

Accidents


Contamination of the Worker

•spills

•improper administration

•experimental work with animals

•emergency surgery of a therapy patient

•autopsy of a therapy patient


Patient as Source of Exposure

Examination

Bone (MDP)

Liver (colloid)

Heart (RBC)

Myocardium

(Thallium

)

0 h post inj

Dose rate nGy/h/MBq

2 h post inj

0 m 0.3 m 1.0 m 0 m

13

0.3 m

7 27

27

13

13

4

4 20

20

10

10 27

36

13

18

4

6 36 10

1.0 m

2

3

3

6


Nuclear Medicine

Dose to Worker

2,5

2

1,5

1

0,5

0

Bone scan

400 MBq, Tc-99m

Dispensing Injection Examination


Contamination

The activity on the hands after elution, preparation and administration of Tc99m-radiopharmaceuticals has been measured to 0.02-200 kBq, which results in a skin dose of

0.005 to 50 mSv/h

Radionuclide

Co-57

Ga-67

Tc-99m

In-111

I-123

I-125

I-131

Tl-201

Dose rate mSv*cm2/MBq*h

78

324

243

376

365

417

1694

343


CONTAMINATION

Administered activity: 1000 MBq I-131

Excretion Concentration Contamination

Saliva <2 MBq/g

Perspiration <20 Bq/cm

Breathing 100 Bq/l

2

Urine < 500 kBq/ml utensils 2 kBq surfaces 10 Bq/cm 2 air 1 Bq/l toilet 2 kBq/cm 2

Generally larger than the derived limits for contamination given by ICRP (publ 57)





Module 5.4.Local Rules and

Procedures

LOCAL RULES

Written and practiced local rules

•normal working conditions

•incidents and accidents


LOCAL RULES

(SAFETY MANUAL)

The Safety Manual should contain:

• a statement of the purpose of the Rules and of the legal basis;

• definition of responsibilities of those involved in the management of radiation protection;

• specification of controlled and supervised areas;

• systems of work for those who enter controlled areas;

• details of storage of radionuclides; locations and maximum activities permitted;

• details of how and where radionuclides may be handled;

• monitoring procedures;

• records to be kept;

• safety assessments when appropriate; and

• contingency plans.


Nuclear Medicine

LOCAL RULES

1. Ordering radionuclides

2. Unpacking and check of shipment

3. Storage of radionuclides

4. Work in controlled and supervised areas

5. Personal and workplace monitoring

6. Internal transports of radionuclides

7. Radioactive waste

8. Administration of radiopharmaceuticals

9. Patient examinations

10. Cleaning facilities

11. Care of radioactive patients


Local Rules and Procedures

3.93. Employers, registrants and licensees shall minimize the need to rely on administrative controls and personal protective equipment for protection and safety by providing well engineered controls and satisfactory working conditions, in accordance with the following hierarchy of preventive measures:

 (1) Engineered controls;

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(2) Administrative controls;

(3) Personal protective equipment.



“3.94. Employers, registrants and licensees, in consultation with workers or through their representatives:

 (a) Shall establish in writing local rules and procedures that are necessary for protection and safety for workers and other persons;

 (b) Shall include in the local rules and procedures any relevant investigation level or authorized level, and the procedures to be followed in the event that any such level is exceeded;

 (c) Shall make the local rules and procedures and the measures for protection and safety known to those workers to whom they apply and to other persons who may be affected by them;”



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“(d) Shall ensure that any work in which workers are or could be subject to occupational exposure is adequately supervised and shall take all reasonable steps to ensure that the rules, procedures, and measures for protection and safety are observed;

 (e) Shall designate, as appropriate, a radiation protection officer in accordance with criteria established by the regulatory body.”


Condition of Service

Employers, registrants and licensees shall not offer benefits as substitutes for measures for protection and safety:

“3.111. The conditions of service of workers shall be independent of whether they are or could be subject to occupational exposure. Special compensatory arrangements, or preferential consideration with respect to salary, special insurance coverage, working hours, length of vacation, additional holidays or retirement benefits, shall neither be granted nor be used as substitutes for measures for protection and safety in accordance with the requirements of these Standards.”


Condition of Service

Alternative employment:

“3.112. Employers shall make all reasonable efforts to provide workers with suitable alternative employment in circumstances for which it has been determined, either by the regulatory body or in the framework of the programme for workers’ health surveillance in accordance with the requirements of these Standards, that workers, for health reasons, may no longer continue in employment in which they are or could be subject to occupational exposure.”





Module 5.5. Personal Protective

Equipment

Personal Protective Equipment

“3.95. Employers, registrants and licensees shall ensure that:

(a) Workers are provided with suitable and adequate personal protective equipment that meets relevant standards or specifications, including as appropriate:

(i) protective clothing;

………..

(iii) protective aprons and gloves and organ shields;

………..

(d) All personal protective equipment, including equipment for use in an emergency, is maintained in proper condition and, if appropriate, is tested at regular intervals;


Protective Clothing

Nuclear Medicine

Appropriate clothing should as a minimum include lab coat and gloves.National regulations may require more.


Safety equipment needed depends on the type of work

Example unpacking:

•check for damage

•check for contamination

•check the content

•check the activity

Safety equipment:

•protective clothing

•contamination monitor

•shields

•forceps, tongs

Part 5. Occupational Protection 68 Nuclear Medicine

Nuclear Medicine

Safety Equipment

PREPARATION OF

RADIOPHARMACEUTICALS

•Shields

•Protective clothing

•Tools for remote handling of radioactive material

•Containers for radioactive waste

•Dose rate monitor with alarm

•Contamination monitor

•Decontamination kit

•Signs, labels and records


ADMINISTRATION

Nuclear Medicine

Syringe shield

Gloves

Lead apron?

Absorbing pads


Nuclear Medicine

Syringe Shield

No shield Shielded (2mm W)

0.4 mSv/h 0.004 mSv/h

0.8 mSv/h

4.2 mSv/h

22 mSv/h

0.01 mSv/h

0.04 mSv/h

0.16 mSv/h

8 mSv/h 6 mSv/h

400 MBq Tc-99m in 1 ml


Nuclear Medicine

Vial Shield

Tc-99m

10 GBq

10 ml

560 mGy/h

1 mGy/h

2 mm lead


Annual Dose to Fingers

Elution: 30 GBq/d (Tc-99m), 200 days

Dispensing: 3 GBq/d

Injections: 8 patients/d 400 MBq/patient

Procedure Mean/max dose Mean/max dose

(no syringe shield) (with shield)

Elution

Dispensing

Injection

(mSv) (mSv)

50/180 50/180

110/420

450/2600

90/420

80/330


Patient Examination

Movable shield

Lead apron


Lead Apron?

Examination Dose ( m

Sv)

Bone (400 MBq, 99m Tc)

CBF (1000 MBq, 99m Tc)

Myocard (75 MBq, 201 Tl)

Blood pool (800 MBq, 99m Tc)

Others (100 MBq, 99m Tc) without apron with apron

2.2

12.0

0.3

4.7

0.4

1.0

5.0

0.2

2.2

0.2


Radiation Protection Measures

Depend on:

• activities used

• type of radionuclide and its chemical properties

• type of procedure


Radiation Protection Measures

• Time

• Distance

• Shielding


Time

Dose is proportional to the time exposed

Nuclear Medicine

Dose = Dose-rate x Time


Consequence

 Reduce time in contact with radiation sources as much as compatible with the task

 Training of a particular task using nonradioactive dummy sources helps


Distance

Inverse square law (ISL):

Dose-rate



1/(distance) 2

Nuclear Medicine distance


Patient with Iodine-131

0.5 0.1 0.06 0.03 mSv/h

1000 MBq

I-131

Nuclear Medicine

0 0.5 1 2 m


Consequence

 Distance is very efficient for radiation protection as the dose falls off in square

 Examples:

 long tweezers for handling of sources

 big rooms for imaging equipment


incident radiation

Shielding

Barrier thickness transmitted radiation


Shielding

Nuclear Medicine

Bench top shield

Vial shields

Syringe shields


Shielding of Sources

Factors affecting the design:

•radionuclide

•activity

•shielding material


Shielding in PET

Biodex Medical

Nuclear Medicine

Protection against high energy photons requires lead shield of significant thickness (cm)


External Exposure from Radionuclides

Nuclide

H-3

C-14

Na-24

P-32

S-35

K-42

K-43

Ca-45

Ca-47

Cr-51

Fe-59

Co-57

Co-58

Cu-64

Ga-67

Zn-65

Se-75

Tc-99m

In-111

I-125

I-123

I-131

Tl-201

Doserate constant

( m

Sv/h MBq)

0. 016

0. 150

0. 032

0. 022

0. 085

0. 056

0. 017

0. 084

0. 034

0. 044

0. 057

0. 012

-

-

0. 500

-

-

0. 038

0. 147

-

0. 150

0. 005

0. 170

TVL

(mm Pb)

0. 7

28

25

5. 3

42

5

0. 9

2. 5

0. 06

1. 2

11

0. 6

53

18

-

46

7

44

-

-

59

-

-

Skin dose

(mSv

 cm2/MBq

 h

78

*

*

324

*

*

243

376

417

365

1694

343

*

305

2357

2397

332

*

*

884

*

*

1283


Definitions

Dose rate constant

The dose rate ( μSv/h) at 1 m from a point source of

1 MBq

TVL

Tenth value layer, which is the thickness of a material that reduces the number of incident photons by a factor of 10.


Nuclear Medicine

Lead Shield

Estimate the thickness of a lead container for 30 GBq of Tc-99m. Dose rate at 1 m should be 2 μSv/h

Dose rate constant: 0.017 μSv/h&MBq

TVL: 0.9 mm lead

Dose rate for unshielded source: 0.017*30000=

510 μSv/h

Reduce exposure 255 times which equals 2.4 TVL=

2.2 mm lead.


Lead Shield

Estimate the thickness of a lead container for 15 GBq of I-131.

Dose rate at 0.1 m should be 200 μSv/h

Dose rate constant: 0.058 μSv/h & MBq

TVL: 11 mm lead

Dose rate for unshielded source: 0.058*15000=

870 μSv/h at 1 m

Dose rate for unshielded source at 0.1 m= 87 mSv/h

Reduce dose rate 435 times which equals 2.64 TVL=

30 mm lead.


Structural Shielding

The absorbed dose is determined by factors such as:

•source strength;

•length of exposure;

•distance from the source;

•transmission through the protective barrier.

Patient with I-131 Ordinary patient

Nuclear Medicine

D mSv/h 0.3 mSv/procedure

Distance d


Structural Shielding

Example:

Source strength : 1 mSv/h at 1 m from the radioactive patient

Length of exposure : 1 week=168 h. We assume that the ordinary patient will be in bed all the time.

Distance from the source: 3 m

The unshielded exposure of the ordinary patient will be 1/9 mSv/h =

= 18.7 mSv in a week.

The dose to the ordinary patient should be constrained to 0.3 mSv in a week, which means that we need a protective barrier that reduces the exposure by a factor of 18.7/0.3=62.

Is the wall between the rooms enough or do we need an extra shield?


CONTAMINATION


To Minimize Contamination Risks

- adopt clean operating conditions

- adopt good laboratory practices

do not eat, smoke etc…

- use protective gloves and clothing


DECONTAMINATION

PROCEDURES

• Use adsorbent paper on wet spill or wet absorbent paper on dry spill

• Repetitively swab the area inwards towards the center of the spill

• Place contaminated paper in a plastic bag or container

• Monitor the area

• Repeat the procedure until the exposure rate is below given limits

• If the decontamination is not successful, mark the contaminated area and classify the room as a controlled area If not already done) until the contamination is completely removed.


Decontamination

Nuclear Medicine

120

Remaining activity (%)

100

80

60

40

20

0

Tc99m pertechnetate

0 1 2 3 4

Number of washings

5 6


Decontamination of Skin

If contamination of the skin occurs, immediately the area should be thoroughly washed using mild soap and tepid (not hot) water. Particular care should be paid to cleaning under the fingernails. If this does not bring the contamination to an acceptably low level the procedure should be repeated using a decontaminating detergent. Scrub with a nail brush but take care not to break the skin.


DECONTAMINATION OF SKIN

Remaining activity (%)

1 2

Method

3 Substance 4

---------------------------------------------------------------------------

Tc99m-DTPA 1 0 1 1

Tc99m-MDP 7 1 3 5

Pertechnetate

Tc99m-colloid

5

<1

7

<1

5 7

<1 <1

I131-hippuran

I131-iodide

Ga67-citrate

<1

8

3

<1

5

1

<1 <1

<1

4

2

1

In111-DTPA <1 <1 <1 <1

----------------------------------------------------------------------------

1 : 90 s in water, 2 : 90 s in soap and water, 3 : skin lotion and 90 s in soap and water, 4 : commercial decontamination substance





Module 5.6. Monitoring of the

Workplace

Monitoring of the Workplace

“3.96. Registrants and licensees, in cooperation with employers where appropriate, shall establish, maintain and keep under review a programme for workplace monitoring under the supervision of a radiation protection officer or qualified expert.

“3.97. The type and frequency of workplace monitoring shall:

 (a) Be sufficient to enable:

 (i) Evaluation of the radiological conditions in all workplaces;

 (ii) Assessment of exposures in controlled areas and supervised areas;

 (iii) Review of the classification of controlled areas and supervised areas;”


Monitoring of the Workplace



“(b) Be based on dose rate, activity concentration in air and surface contamination, and their expected fluctuations, and on the likelihood and magnitude of exposures in anticipated operational occurrences and accident conditions.

3.98. Registrants and licensees, in cooperation with employers where appropriate, shall maintain records of the findings of the workplace monitoring programme. The findings of the workplace monitoring programme shall be made available to workers, where appropriate through their representatives.”



Assessment

“3.99. Employers, as well as self-employed persons, and registrants and licensees shall be responsible for making arrangements for assessment of the occupational exposure of workers, on the basis of individual monitoring where appropriate, and shall ensure that arrangements are made with authorized or approved dosimetry service providers that operate under a quality management system

.

3.100. For any worker who usually works in a controlled area, or who occasionally works in a controlled area and may receive a significant dose from occupational exposure, individual monitoring shall be undertaken where appropriate, adequate and feasible. In cases where individual monitoring of the worker is inappropriate, inadequate or not feasible, the occupational exposure shall be assessed on the basis of the results of workplace monitoring and information on the locations and durations of exposure of the



Assessment

“ 3.101. For any worker who regularly works in a supervised area or who enters a controlled area only occasionally, the occupational exposure shall be assessed on the basis of the results of workplace monitoring or individual monitoring, as appropriate.

“3.102. Employers shall ensure that workers who could be subject to exposure due to contamination are identified, including workers who use respiratory protective equipment. Employers shall arrange for appropriate monitoring to the extent necessary to demonstrate the effectiveness of the measures for protection and safety and to assess intakes of radionuclides and the committed effective doses.”


Monitoring

Personal

(effective dose, extremity dose & contamination)

Workplace

(external dose rate & contamination)


Individual Monitoring

 control of radiation exposure

 assessment of optimization principle

 identifies high doses

 assessment of working practices


Who Should be Monitored?

Those who are working with preparation and administration of radiopharmaceuticals and those who are performing patient examinations and quality control of the equipment such as:

Nuclear medicine specialist

Nuclear medicine technicians

Medical physicist

…and more?

Who should decide?



The Radiation Protection Committee should specify:

- workers who have to be monitored routinely

- ancillary workers who occasionally work in controlled areas and should be monitored

- type of personnel which will be individually monitoring

- place where the monitor should be worn

- if extremity dosimeters should be worn (if compatible with good clinical practice) for special tasks

- period of exchange of dosimeters and receipt of the dose reports

- responsible person for dosimeter exchange

- procedure for lost individual dosimeter


Different types of personal dosemeters for monitoring external exposure

• film

• termoluminescence dosemeters (TLD)

• ”electronic” dosemeters


plastic filter

Film Badge

metal filters open windows open window

Nuclear Medicine detects beta, gamma, X-ray


Processed Films

Nuclear Medicine gamma

Part 5. Occupational Protection misuse

110

Thermoluminescence

thermoluminescent material photomultiplier heating filament emitted light


TLD


TLDs

whole body

Nuclear Medicine Part 5. Occupational Protection extremity

113

Film

Film or TLD?

TLD advantages disadvantages advantages disadvantages wide exposure range; independent of dose rate; provides information on the type of radiation; small and relatively inexpensive; permanent record.

no direct reading; the response depends on energy, temperature, humidity, angle of incidence of radiation; processing and interpreting are required high sensitivity; linear dose response curve over a wide range of doses; dose response independent of dose-rate; and they are reusable.

heating the dosemeter destroys the dosimetry information; the instrumentation for TLD is relatively expensive to purchase; skilled, trained experts are required to run the service


MONITORING OF THYROID

(internal contamination)


WHOLE BODY MONITORING

(contamination)

The gamma camera without collimator can be used


EXPOSURE OF THE

WORKER

The monitored effective dose for workers in a nuclear medicine department is about 3-5 mSv per year. The extremity dose (fingers) is about 10 times higher.


Occupational Exposure Limits

For occupational exposure of workers over the age of

18 years, the dose limits are:





(a) An effective dose of 20 mSv per year averaged over five consecutive years (100 mSv in 5 years), and of 50 mSv in any single year;

(b) An equivalent dose to the lens of the eye of 20 mSv per year averages over 5 consecutive years (100 mSv in 5 years) and of 50 mSv in any single year;

 (c) An equivalent dose to the extremities (hands and feet) or the skin of 500 mSv in a year.

Additional restrictions apply to occupational exposure for a female worker who has notified pregnancy or is breast-feeding.


Occupational Exposure Limits

For occupational exposure of apprentices of 16 to 18 years of age who are being trained for employment involving radiation and for exposure of students of age 16 to 18 who use sources in the course of their studies, the dose limits are:

 (a) An effective dose of 6 mSv in a year;

 (b) An equivalent dose to the lens of the eye of

20 mSv in a year;

 (c) An equivalent dose to the extremities (hands and feet) or the skin 66 of 150 mSv in a year.



RPC will conduct formal investigations, as required by the Regulatory

Authority, whenever:

(a) the individual annual effective dose exceeds the investigation

(b)

(c)

(d) level any of the operational parameters subject to periodic quality control are out of the normal range established for operational conditions any severe accident or error takes place any other event or unusual circumstance that causes, or has the potential to cause a dose in excess of the regulatory limits.


SUGGESTED

INVESTIGATION LEVELS

Site Investigation Level Investigation Level for a Four Week for a Thirteen week

Period (mSv) Period (mSv)

Body

Eye

Individual organs

/extremities

0.5

5

15

2

20

50


Investigations and Follow-up

3.179. Registrants and licensees shall promptly investigate any of the following unintended or accidental medical exposures:

(a) Any medical treatment delivered to the wrong individual or to the wrong tissue of the patient, or using the wrong radiopharmaceutical, or with an activity, a dose or dose fractionation differing substantially from (over or under) the values prescribed by the radiological medical practitioner, or that could lead to unduly severe secondary effects;

(b) Any diagnostic radiological procedure or image guided interventional procedure in which the wrong individual or the wrong tissue of the patient is subject to exposure;

(c) Any exposure for diagnostic purposes that is substantially greater than was intended;

(d) Any exposure arising from an image guided interventional procedure that is substantially greater than was intended;

(e) Any inadvertent exposure of the embryo or fetus in the course of performing a radiological procedure;

(f) Any failure of medical radiological equipment, software failure or system failure, or accident, error, mishap or other unusual occurrence with the potential for subjecting the patient to a medical exposure that is substantially different from what was intended


Workplace Monitoring

Programmes

Provide information which allows :

 evaluation of radiation conditions

 assessment of potential exposures

 ongoing review of classification of controlled and supervised areas


Monitoring Instruments



Nuclear Medicine

• Ionization chambers

• Proportional counters

• GM-tubes

• Scintillation detectors


Nuclear Medicine


Count rate meters for contamination detection purposes

Dose rate meters for measuring dose rate


Nuclear Medicine

Choice of Monitoring

I nstrument…

… depends on...

• High or low levels?

• Particles or photons?

• Energy of photons?

• Required accuracy?


Choice of D etector Type…

… may be important for ...

• Required sensitivity

… otherwise NOT so important !

The design of the instrument to fulfill the requirements more important!


Contamination Detectors

β - emitters g

- emitter (< 50 keV) g

- emitter (high energy)

GM-tube

Proportional counter

GM-tube


NaI(Tl) scintillation detector


NaI(Tl) scintillation detector

All with an appropriate design!


g

- emitter

Dose-rate Meters

GM-tube

Ionisation chamber

Scintillation detector

Often designed to meet the requirements to measure one of the operational dose quantities defined in ICRU 47


Making Measurements

• Check batteries

• Switch on before entering radiation area

• Move monitor slowly

Nuclear Medicine

•

Change scale if necessary


Workplace Monitoring

Programmes



Identify the quantity to be measured



Specify location and frequency



Specify procedures



Identify reference levels



Specify record keeping


EXAMPLE: MONITORING

THERAPY WARD

Area or item

Toilet

Washroom floor

Sink and Faucets

Shower

Bed

Armchair

Bedroom floor

TV/Telephone

Bedside table

Doorknobs

Lamp switches

Initial

(Bq/cm

2

)

After cleaning

(Bq/cm

2

)

Derived limit: 3 Bq/cm 2

METHODS

• wipe test

• area monitor


WIPE TEST

Wipe a known surface area with an absorbent material moistened with water or alcohol. Put the sample in a tube and measure the activity in a well counter or a liquid scintillation counter.

(cps-BG)/(E c

*E w

*A) = contamination (Bq/cm 2 ) cps: counts per second for sample

BG: instrument background

E c

: counter efficiency (cps/Bq)

E w

: swipe efficiency (assumed to be 0.1)

A: area swiped (cm 2 )


Derived limits for surface contamination

Area

RadioControlled Supervised Body toxicity (Bq/cm2) (Bq/cm2) (Bq/cm2)

Class

A

B

C

30

300

3000

3

30

300

3

30

300





Module 5.6. Exposures Records

Records of Occupational

Exposure

“3.103. Employers, registrants and licensees shall maintain records of occupational exposure for every worker for whom assessment of occupational exposure is required.

3.104. Records of occupational exposure for each worker shall be maintained during and after the worker’s working life, at least until the former worker attains or would have attained the age of 75 years, and for not less than 30 years after cessation of the work in which the worker was subject to occupational exposure.”

.



Exposure

“3.105. Records of occupational exposure shall include:





(a) Information on the general nature of the work in which the worker was subject to occupational exposure;

(b) Information on dose assessments, exposures and intakes at or above the relevant recording levels and the data upon which the dose assessments were based;

 (c) When a worker is or has been exposed while in the employ of more than one employer, information on the dates of employment with each employer and on the doses, exposures and intakes in each such employment;

 (d) Records of any assessments of doses, exposures and intakes due to actions taken in an emergency or due to accidents or other incidents, which shall be distinguished from assessments of doses, exposures and intakes due to normal conditions of work and which shall include references to reports of any relevant investigations.”.



Exposure

“3.106. Employers, registrants and licensees:











(a) Shall provide workers with access to records of their own occupational exposure;

(b) Shall provide the supervisor of the programme for workers’ health surveillance, the regulatory body and the relevant employer with access to workers’ records of occupational exposure;

(c) Shall facilitate the provision of copies of workers’ exposure records to new employers when workers change employment;

(d) Shall make arrangements for the retention of exposure records for former workers by the employer, registrant or licensee, as appropriate;

(e) Shall, in complying with (a) –(d) above, give due care and attention to maintaining the confidentiality of records.”.


Information, Instructions and

Training

“3.110. Employers, in cooperation with registrants and licensees:





(a) Shall provide all workers with adequate information on health risks due to their occupational exposure in normal operation, anticipated operational occurrences and accident conditions, adequate instruction and training and periodic retraining in protection and safety, and adequate information on the significance of their actions for protection and safety;

(b) Shall provide those workers who could be involved in or affected by the response to an emergency with appropriate information, and adequate instruction and training and periodic retraining, for protection and safety;

 (c) Shall maintain records of the training provided to individual workers.”


EDUCATION AND TRAINING

Personnel shall be instructed in radiation protection before assuming duties with, or in the vicinity of radioactive materials, during annual refresher training, and whenever there is a significant change in duties, regulations, terms of the license, or type of radioactive material or instruments used. Topics should be selected from a syllabus which has been approved by the

RPC.


Training

The records should include the following information:

(a) Name of the person(s) who delivered the instruction or training;

(b) Name of the person(s) who received the instruction or training;

(c) Date and duration of the instruction or training;

(d) List of the topics addressed;

(e) Copy of the certificates of training


Special Arrangements

Employers, registrants and licensees shall make special arrangements for female workers, as necessary, for protection of the embryo or fetus and of breast-fed infants.

Employers, registrants and licensees shall make special arrangements for protection and safety for persons under 18 years of age who are undergoing training.



“3.113. Employers, in cooperation with registrants and licensees, shall provide female workers who are liable to enter controlled areas or supervised areas or who may undertake emergency duties with appropriate information on:

 (a) The risk to the embryo or fetus due to exposure of a pregnant woman;

 (b) The importance for a female worker of notifying her employer as soon as possible if she suspects that she is pregnant or if she is breast-feeding;

 (c) The risk of health effects for a breast-fed infant due to ingestion of radioactive substances.”



“3.114. Notification of the employer by a female worker if she suspects that she is pregnant or if she is breast-feeding shall not be considered a reason to exclude a female worker from work. The employer of a female worker, who has been notified of her suspected pregnancy or that she is breast-feeding, shall adapt the working conditions in respect of occupational exposure so as to ensure that the embryo or fetus or the infant is afforded the same broad level of protection as is required for members of the public.



“3.115. Employers, registrants and licensees shall ensure that no person under the age of 16 years is or could be subject to occupational exposure.

3.116. Employers, registrants and licensees shall ensure that persons under the age of 18 years are allowed access to a controlled area only under supervision and only for the purpose of training for employment in which they are or could be subject to occupational exposure or for the purpose of studies in which sources are used.”





Module 5.7. Emergency Procedures

SAFETY ASSESSMENT

CONTINGENCY PLAN

A safety assessment will reveal the possible situations where emergency actions have to be taken:

•Loss or damage of radioactive material

•Spillage of radioactive material

•Fire

•Medical emergencies

•...

A detailed contingency plan covering actions to be taken in any foreseeable accident should be available.





Module 5.8. Health Surveillance

Health Surveillance

3.108. Health surveillance programmes shall be:

(a) Shall be based on the general principles of occupational health;

(b) Shall be designed to assess the initial fitnessand continuing fitness of workers for their intended tasks.



 3.109. If one or more workers are to be engaged in work in which they are or could be exposed to radiation from a source that is not under the control of their employer, the registrant or licensee responsible for the source shall, as a precondition for the engagement of such workers, make any special arrangements for workers’ health surveillance with the employer that are needed to comply with the rules established by the regulatory body or other relevant authority.



The following three situations may need to be considered in the initial medical examination and in the subsequent

Reviews:

 The fitness of a worker for wearing protective devices such as respiratory protection devices, lead aprons etc.

 The fitness of a worker with a skin disease, such as eczema or psoriasis

 The fitness of a worker known to have a psychological disorder for work with radiation sources



Health surveillance records should be confidential and preserved in a manner approved by the Regulatory Authority.

The minimum period of record keeping should be the lifetime of the worker concerned. Longer preservation may be advisable.


Overexposed Workers

If a substantial overexposure is suspected to have occurred, the management should promptly undertake an investigation to assess the dose received by the worker concerned. The investigation should include the reading of personal dosimeters and any monitoring instruments and, in the case of internal exposure, in vivo and in vitro monitoring as appropriate.





Module 5.9. Records

Records

• The authorization certificate and documentation supporting the corresponding applications, as well as any correspondence between the Licensee and Regulatory

Authority

• Name of the person authorized and responsible for the radiation protection programme

• Individual doses (current and prior work history)

• Results of area surveys

• Equipment and instrument QC tests and calibration

• Inventory of unsealed and sealed sources

• Incident and accident investigation reports

• Audits and reviews of radiation safety programme

• Training

• Installation, maintenance and repair work

• Facility modification

• Evidence of health surveillance of workers

• Waste disposal

• Transportation:

Package documentation

Package surveys

Transfer/receipt documents

Details of shipments dispatched

• Patient records

• Patient discharge surveys (radionuclide therapy).


Questions?


DISCUSSION

Which categories of staff should be monitored in a nuclear medicine department?

Different policies in different countries?


DISCUSSION

Discuss the design of a room for preparation of radiopharmaceuticals. What safety equipment is needed.

How to establish safe working procedures?


DISCUSSION

In a diagnostic nuclear medicine department, the technicians are performing preparation and administration of radiopharmaceuticals, as well as examination of the patients and quality control of the equipment.

Identify the most hazardous situations and suggest how the exposure of the worker should be optimized.


Where to Get More Information







Other sessions









Part 4. Design of facilities

Part 8 Radionuclide therapy

Part 10 Radioactive waste

Part 12 Potential exposure

Further readings

 IAEA Basic Safety Standards, Interim Edition (2011)







IAEA Safety Guide on Occupational Protection

IAEA Model regulations for nuclear medicine

WHO/IAEA Manual on Radiation Protection in Hospital and General

Practices. Volume 1: Basic requirements & Volume4: Nuclear medicine

Practical sessions









Visit to a Nuclear Medicine facility. Simulated inspection

Workplace monitoring

Decontamination procedures

Shielding of sources


05. Occupational protection - Radiation Protection of Patients

Part 5

Occupational Exposure

Definition

Objective

Contents

IAEA SAFETY STANDARDS

BSS:

Interim Version 2011

The System of Protection and

Safety: BSS (2011)

Module 5.1. Responsibilities

Responsibility for Safety:

BSS 1.8 (2011)

Role of Government:

BSS 1.9 (2011)

Role of Government:

BSS 1.10 (2011)

Role of Government:

BSS 1.11 (2011)

Responsibilities of the regulatory body to occupational exposure

Requirement 19: BSS (2011)

Responsibilities of the regulatory body to occupational exposure

Requirement 19: BSS (2011)

Responsibilities of the regulatory body to occupational exposure

Requirement 19: BSS (2011)

Requirements for monitoring and recording of occupational exposure

Requirement 20: BSS (2011)

Compliance by Workers

Requirement 22: BSS (2011)

Compliance by Workers

Requirement 22: BSS (2011) contd …

Compliance by Workers

Requirement 22: BSS (2011) contd …

Workers Responsibilities

Cooperation between employers and registrants and licensees

Requirement 23: BSS (2011)

Module 5.2. Classification of Areas

CLASSIFICATION OF AREAS

Classification of Areas:

Controlled Area

Controlled Area

Controlled Area

Classification of Areas:

Supervised Area

Classified Areas

WORK IN CONTROLLED AREA

WORK IN CONTROLLED AREA

WORK IN CONTROLLED AREA

WORK IN CONTROLLED AREA

WORK IN CONTROLLED AREA

Module 5.3. Sources of Exposure

Optimization of Protection

Exposure of the Worker

Contamination of the Worker

Patient as Source of Exposure

Dose to Worker

Contamination

CONTAMINATION

Module 5.4.Local Rules and

Procedures

LOCAL RULES

LOCAL RULES

(SAFETY MANUAL)

LOCAL RULES

Local Rules and Procedures

Local Rules and Procedures

Local Rules and Procedures

Condition of Service

Condition of Service

Module 5.5. Personal Protective

Equipment

Protective Clothing

Safety equipment needed depends on the type of work

Safety Equipment

ADMINISTRATION

Syringe Shield

Vial Shield

Annual Dose to Fingers

Patient Examination