Occupational Exposure in Nuclear Medicine

DevakumarDepartment of Nuclear Medicine

Christian Medical CollegeVellore

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EXPOSUREEXPOSURESS IN NUCLEAR MEDICINE IN NUCLEAR MEDICINE

InternalIngested and/or inhaledradionuclides

ExternalVials, syringes, patients.

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Unpacking and Storage

Activity measurements

Preparation of radiopharmaceuticals

AdministrationExamination of the patient (Scan)

Care of the radioactive patient

Handling of radioactive waste

Accidents

Exposure to the Worker

Part 5. Occupational Protection 4

Excretion Concentration Contamination

Saliva <2 MBq/g utensils 2 kBqPerspiration <20 Bq/cm2 surfaces 10 Bq/cm2

Breathing 100 Bq/l air 1 Bq/lUrine < 500 kBq/ml toilet 2 kBq/cm2

Administered activity: 1000 MBq I-131 (27mCi)

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

Contamination(from patient)

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The activity on the hands after elution, preparation andadministration 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 Dose ratemSv*cm2/MBq*h

Co-57 78Ga-67 324Tc-99m 243In-111 376I-123 365I-125 417I-131 1694Tl-201 343

Contamination and dose rate(from handling radioactive materials)

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Elution: 30 GBq/d (810mCi/d) (Tc-99m), 200 days

Dispensing: 3 Gbq/d

Injections: 8 patients/d 400 MBq/patient

Annual Dose to FingersAnnual Dose to Fingers

Procedure Mean/max dose Mean/max dose (no syringe shield) (with shield)

(mSv) (mSv)Elution 50/180 50/180Dispensing 110/420 90/420

Injection 450/2600 80/330

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•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

Safety EquipmentSafety EquipmentPREPARATION OF RADIOPHARMACEUTICALSPREPARATION OF RADIOPHARMACEUTICALS

Part 5. Occupational Protection 8

Time - ConsequenceTime - Consequence

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

● Training of a particular task Training of a particular task using non-radioactive dummy using non-radioactive dummy sources helpssources helps

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Distance – For patientDistance – For patient with with Iodine-131Iodine-131

1000 MBqI-131

0 0.5 1 2 m

0.5 0.1 0.06 0.03 mSv/h

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Distance - ConsequenceDistance - Consequence● Examples:Examples:

long tweezers for handling of sourceslong tweezers for handling of sources big big roomsrooms for for imagingimaging equipment equipment

Part 5. Occupational Protection 11

Shielding of SourcesShielding of SourcesFactors affecting the design:

•radionuclide•activity•shielding material

Part 5. Occupational Protection 12

Syringe ShieldSyringe Shield

400 MBq Tc-99m in 1 ml

No shield

0.4 mSv/h

0.8 mSv/h

4.2 mSv/h

22 mSv/h

8 mSv/h

Shielded (2mm W)

0.004 mSv/h

0.01 mSv/h

0.04 mSv/h

0.16 mSv/h

6 mSv/h

Part 5. Occupational Protection 13

Vial ShieldVial Shield

560 mGy/h

1 mGy/h

Tc-99m10 GBq10 ml

(270 mCi)

2 mm lead

Part 5. Occupational Protection 14

Shielding in PETShielding in PET

Biodex Medical

Protection against high energyphotons requires lead shield ofsignificant thickness (cm)

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Examination Dose (Sv) without apron with apron

Bone (400 MBq, 99mTc) 2.2 1.0CBF (1000 MBq, 99mTc) 12.0 5.0Myocard (75 MBq, 201Tl) 0.3 0.2Blood pool (800 MBq, 99mTc) 4.7 2.2Others (100 MBq, 99mTc) 0.4 0.2

During scanLead Apron?

Part 5. Occupational Protection 16

Structural ShieldingStructural Shielding

Patient with I-131

0.3 mSv/procedure

Distance d

Ordinary patient

The absorbed dose is determined by factors such as:•source strength;•length of exposure;•distance from the source;•transmission through the protective barrier.

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Remaining activity (%)

Number of washings

Tc99m pertechnetate

Decontamination

0

20

40

60

80

100

120

0 1 2 3 4 5 6

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Decontamination of SkinDecontamination of Skin

Immediately wash the area of the skin thoroughly 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.

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DECONTAMINATION OF SKINDECONTAMINATION OF SKIN

Remaining activity (%) Method

Substance 1 2 3 4---------------------------------------------------------------------------Tc99m-DTPA 1 0 1 1Tc99m-MDP 7 1 3 5Pertechnetate 5 7 5 7Tc99m-colloid <1 <1 <1 <1I131-hippuran <1 <1 <1 <1I131-iodide 8 5 <1 2Ga67-citrate 3 1 4 1----------------------------------------------------------------------------1: 90 s in water, 2: 90 s in soap and water, 3: skin lotionand 90 s in soap and water, 4: commercial decontaminationsubstance

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WHOLE BODY MONITORINGWHOLE BODY MONITORING(contamination)(contamination)

The gamma camera without collimator can be used(In addition to Contamination monitor)

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MONITORING OF THYROIDMONITORING OF THYROID(internal contamination)(internal contamination)

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EXPOSURE OF THE WORKEREXPOSURE OF THE WORKER

The monitored effective dose for workers in a nuclearmedicine department is about 3-5 mSv per year.

The extremity dose (fingers) is about 10 times higher.

Occupational Exposure LimitsOccupational Exposure Limits

For occupational exposure of workers over the age of 18 For occupational exposure of workers over the age of 18 years, the dose limits are:years, the dose limits are: (a) An effective dose of (a) An effective dose of 20 mSv per year20 mSv per year averaged over averaged over

five consecutive years (100 mSv in 5 years), and of 30 five consecutive years (100 mSv in 5 years), and of 30 mSv in any single year;mSv in any single year;

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

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

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

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Site Investigation Level Investigation Level for a Four Week for a Thirteen week Period (mSv) Period (mSv)

Body 0.5 2 

Eye 5 20 Individual organs

/extremities 15 50

SUGGESTED INVESTIGATION SUGGESTED INVESTIGATION LEVELSLEVELS

Thank you

Check

Tissue weighting factor for lensOccupational annual equivalent dose limit for lens

Radiotoxicity

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Derived limits for Derived limits for surface contaminationsurface contamination

AreaRadio- Controlled Supervised Bodytoxicity (Bq/cm2) (Bq/cm2) (Bq/cm2)Class

A 30 3 3 B 300 30 30 C 3000 300 300