Radiation Protectionin

Nuclear Medicine

Urmia University of medical scienceMedical physics DepartmentPresented by M.Shafiee, MSc of Medical Physics

Shafieemp@yahoo.com

Aims and Objectives of Radiation Protection

A L A R A

The objectives of radiation protection can be achieved byreducing all exposure to as low as reasonably achievable(ALARA) and by applying dose limits for controlling occupational and general public exposures.For radiation protection purposes, it is assumed that the risk of stochastic effects is strictly proportional todose without threshold throughout the range of doseand dose rates of importance in radiation protection.

Radiation ProtectionPrinciples

Time Minimize the amount off time during the exposure..

Distance Maximize the distance from the radiation source..Inverse-Square Law states that as you DOUBLE the distance

from a radiation source,, you reduce the exposure levels by ONE-FOURTH ( 1/4 )..

Shielding Utilize shielding to avoid direct exposure to the radiation source..

Hot Laboratory

• The center of receivement,store, transportation and exit of radioactive materials in nuclear medicine depatment.

Radiation Protection in PET/CT

8

Mo-99 Tc-99m Tc-99 66 h 6h

NaCl

AlO2

Mo-99+Tc-99m

Tc-99m

Technetium generator

99Mo-99mTc GENERATOR

99Mo 87.6% 99mTc

140 keVT½ = 6.02 h

99Tc

ß- 292 keVT½ = 2*105 y

99Ru stable

12.4%

ß- 442 keV 739 keVT½ = 2.75 d

11

Categorization of hazard

Based on calculation of a weighted activity using weighting factors according to radionuclide used and the type of operation performed.

Weighted activity Category< 50 MBq Low hazard50-50000 MBq Medium hazard>50000 MBq High hazard

CLASSIFIED AREASShould 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

“I.23. Registrants and licensees shall:

(a) delineate controlled areas by physical means or, where this is

not reasonably practicable, by some other suitable means;

(c) display a warning symbol

(d) establish occupational protection and safety measures,

including local rules and procedures that are appropriate for

controlled areas;

(e) restrict access to controlled areas

CONTROLLED AREA

(f) provide, as appropriate, at entrances to controlled

areas: (i) protective clothing and equipment; (ii) monitoring equipment; and (iii) suitable storage for personal clothing; (i) equipment for monitoring for contamination of skin and clothing;(ii) equipment for monitoring for contamination of any

object or substance

(iii) washing or showering facilities(iv)suitable storage

CONTROLLED AREA

Shielding

Bench top shield

Vial shields

Syringe shields

SHIELDING OF SOURCES

Factors affecting the design:

•radionuclide•activity•shielding material

Dose rate constantThe dose rate (μSv/h) at 1 m from a point source of 1 MBq

Syringe 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 pb)

0.004 mSv/h

0.01 mSv/h

0.04 mSv/h

0.16 mSv/h

6 mSv/h

Part 5. Occupational Protection

18

Vial Shield

560 mGy/h

1 mGy/h

Tc-99m10 GBq10 ml

2 mm lead

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&MBqTVL: 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 & MBqTVL: 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.

Lead shield

QC(quality control) in nuclear medicine center:

• AntisepticAntiseptic technique for work with this agents

• Air Quality Air Quality should be controled. Check up for air pressure,air flow direction,air violocity and efficentcy of filterring

• Good ventilation Good ventilation (hoods-laminar air flow cabinets)

Display a warning symbol...

Equipment:

For radionucleid generators and kits the following equipment is necessary:

• Activitymeter• Choromatographic equipment• Microscop for controlling fallout• Antiseptic testing equipments

• Shower and lavatory for cleaning contamination• There should be one radiation detector for survey

floor and surface of workbench• When you working with radioactive substances

you should have disposal glove or lattix disposal gloves.

• For pick up and transportation radioactive vials should employ tongs with prolong handles, to made greater distance and reducing absorbed dose

Staff that work in nuclear medicine besides other part in hospital,at entering and exiting from nuclear medicine department should exchange their covers, because of prevention of carring contamination to other area in hospitals!

Personal dosimeter sholdn’t use out of nuclear medicine department!

Laboratory Rules for the Use of Radioactive Materials

• Wear laboratory coats, or other protective clothing at all times in areas where radioactive materials are used..

• Wear disposable gloves at all times while handling radioactive materials..

• Monitor hands and clothing for contamination after each procedure or before leaviing the area..

• Use syringe shields for preparation of patient doses and administration to patients except in circumstances,, such as pediatric cases, where theiir use would compromise the patient's well-being..

• Do not eat,drinking,smoke or apply cosmetics in any area where radioactive material is stored or used..

• Assay each patientt dose in the dose calibrator prior to administration..

Laboratory Rules for Use of Radioactive Materials-cont

• Do not use any doses that differ from the prescribed dose by

more than 10%..

• Wear personnel monitoring devices (Film badge or TLD) at all

times while in areas where radioactive materials are used or

stored. These should be worn at chest or waist level.

• Wear finger badges during elution of generator and

preparation, assay and injection of radiopharmaceuticals.

• Dispose of radioactive waste onlly in specially designated

recepttaclles.

• Never pipette by mouth..

• Survey generator, kit preparation and injection areas for

• contamination after each procedure or at the end of the day.

Decontaminate if necessary.

• Confine radioactive solutions in covered containers plainly

identified and labeled with name of compound, radionuclide,

date, activity and radiation level if applicable.

• Always transport radioactive material in shielded containers.

Laboratory Rules for Use of Radioactive Materials-cont

Radiological Units:

Quantity Unit Value SI Unit

Radiation Exposure

R 2.58 X 10-4 C/Kg

Absorbed Dose

Rad 1 X 10-2 Gy

Dose Equivalent

Rem 1 X 10-2 Sv

Radioactivity curie 3.7 X1010 becquerel

Sealed sources for calibration of activity meters

RadionuclideRadionuclide Photon energy Photon energy (keV)(keV)

Half-lifeHalf-life ActivityActivity(MBq)(MBq)

Co-57Co-57 122122 271 d271 d 185185

Ba-133Ba-133 81, 35681, 356 10.7 y10.7 y 9.39.3

Cs-137Cs-137 662662 30 y30 y 7.47.4

Co-60Co-60 1173, 13321173, 1332 5.27 y5.27 y 1.91.9

Summary of dose limits established in the Basic Safety Standards.

DOSE LIMIT (1)

APPLICATION

Occupational

Effective dose 20 mSv per year averaged over defined periods of 5 years (2) Effective dose to the embryo or foetus

1 mSv

Annual equivalent dose in the lens of the eye the skin (4) the hands and feet

150 mSv 500 mSv 500 mSv

1. 2. 3. 4.

The limits apply to the sum of the relevant doses from external exposure in the specified period and the 50-year committed dose (to age 70 years for children) from intakes of radioactive nuclides in the same period With the further provision that the effective dose should not exceed 50 mSv in any single year. In special circumstances a higher value of effective dose could be allowed in a single year, provided that the average over 5 years does not exceed 1 mSv per year. The limitation on the effective dose provides sufficient protection for the skin against stochastic effects. An additional limit is needed for localised exposures to prevent deterministic effects.

Dose monitoring tools

Ion chambers Semiconductors TLDs FilmAdvantages Well understood,

accurate, variety offorms available

Small, robust Small, no cablesrequired

Two dimensional,ease of use

Disadvantages Large, high voltagerequired

Temperaturedependence

Delayed readout,complex handling

Not tissueequivalent, notvery reproducible

Common use Referencedosimetry, beamscanning

Beam scanning, invivo dosimetry

Dose verification,in vivo dosimetry

QA, assessment ofdose distributions

Comment Most common andimportantdosimetrictechnique

New developments(MOSFETs) mayincrease utility

Also used fordosimetricintercomparisons(audits)

New developments(radiochromicfilm) may increaseutility

0

0,5

1

1,5

2

2,5

Dispensing Injection Examination

Dos

e (u

Sv)

Bone scan400 MBq, Tc-99m

Dose to worker

Part 5. Occupational Protection

34

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 Dose rate mSv*cm2/MBq*h

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

Contamination

Comparsion typical Effective Radiation Dose from Diagnostic X Ray—Single Exposure

• Radiological x-ray procedures

Occupational Exposure

Pregnant staff

• For external irradiation from Tc-99m or I-131, a dose of 1.3 mSv to the surface of the maternal abdomen has been shown to give rise to a dose of 1 mSv to the fetus.

• For higher energy photons, such as those from positron emitters, the dose to the fetus may be similar to the dose at the surface of the abdomen.

Approximate fetal whole body dose (mGy) from common nuclear medicine procedures done in early and late pregnancy

Procedure Activity (MBq)

Early 9 months

Tc-99m      

Bone scan Lung V/Q scan Liver colloid Thyroid scan Renal DTPA Red Cell

750240300400750930

4.70.90.64.49.06.0

1.80.91.13.73.52.5 

I-123 Thyroid uptake

30 0.6 0.3

I-131 Thyroid uptake 0.55 0.04 0.15

 

Occupational Exposure Lead ApronsIn certain circumstances staff may need to wear a protective lead

apron. This may be necessary if staff need to be in close contact with patients containing greater than 800 MBq of Tc-99m, such as during myocardial perfusion studies or gated cardiac blood pool studies. Protective aprons should preferably have a thickness of 0.5 mm lead equivalence.

Lead aprons provide little or no protection for higher energy photons and should not be used for Radionuclides such as Ga-67 or I-131 or for positron emitters.

0

20

40

60

80

100

120

0 1 2 3 4 5 6

Decontamination

Remaining activity (%)

Number of washings

Tc99m pertechnetate

MONITORING OF THYROID(internal contamination)

Skin EffectsSkin Effects

By handling unshielded syringes and vials containing radioactive material the threshold dose of skin erythema will be reached in a short time.

Example: The dose rate at the surface of a vialcontaining 30 GBq Tc99m is of the order of 2 Gy/h meaning that the threshold dose will be reached after 2 h of exposure. This corresponds to 36 s per working day in a year

For patient with I-31 therapy and radioactive dosage above 20mci I-131, they should hospitalize in special rooms, and be controlled and folow up for their requirment and when their radiation decay at 1m distance of patients skin stike a balance, they could be discharge.

Patient with iodine-131

1000 MBqI-131

0 0.5 1 2 m

0.5 0.1 0.06 0.03 mSv/h

I-131

8.04 d

- Particle E:

0.33 (9%)0.61 (87%)

more

Photon E:

0.365 (80%)

0.640 (9%)more

Tired..?

THYROID MONITORING LOGBOOK

All Nuclear Medicine personnel involved in use of I-131

sodium iodide in quantities >1 mCi must have a

routine thyroid count performed every 6 months; in

addition, 24 hours after an iodination procedure or

administration of I-131 sodium iodide in liquid form,

the thyroid must be counted.

Examples of Waste from Nuclear Medicine

•Biological waste which may undergo decomposition.

•Infectious waste requiring sterilization prior to disposal.

•Broken glass-ware, syringes etc, requiring collection in

separate containers to prevent personnel being injured.

•Radionuclide generators

•Bed linen and clothing from hospital wards.

•Liquid scintillation solutions

•Patient excreta

50

Segregation/Waste Containers

Containers to allow segregation of different types of radioactive waste should be available in areas where the waste is generated. The containers must be suitable for purpose (volume, shielding, leak proof, etc.)•Glassware with radionuclides (short half-life)•Syringes and needles•Gloves and paper•Glassware with radionuclides (medium half-life)

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A room for interim storage of radioactive waste should be available. The room should be locked, properly marked and ventilated.

Each type of waste should be kept in separate containers properly labeled to supply information about the radionuclide, activity concentration etc. Flammable goods should be kept apart.

Records should be kept where the origin of the waste can identified.

Storage of Radioactive Waste

Part 10. Radioactive waste

52

Storage of Radioactive Waste

Part 10. Radioactive waste

53

•Storage of Radioactive Waste

Part 1. Biological effects of ionizing radiation

54

Health consequences of Chernobyl accident•1800 children diagnosed with thyroid cancer (1998)

• Solid waste.Cover papers, gloves, empty vials and syringes. Radionuclide generators. Items used by hospitalized patientsafter radionuclide therapy. Sealed sources used for calibration of instruments. Animal carcasses and other biological waste.

• Liquid waste.Residues of radionuclides. Patient excreta. Liquid scintil-lation solutions.

• Gaseous waste.Exhausted gas from patients in nuclear medicine

Radioactive Waste in Nuclear Medicine

Part 10. Radioactive waste

56

Example of national regulations of disposal of waste fromhospitals:

Disposal via the public waste treatment system

•The dose rate at the surface of each package should be<5 uGy/h.•The package should not contain any single sealed source with activity >50 kBq.•Each package should be properly labeled with a warningsign containing information on radionuclide and activity. The origin of the waste should also be given on the package.

Disposal of Solid Waste

57

Quality Assurance•Local rules

Normal working conditionsAccidents

•Waste identification and traceabilityRecord system

•Process controlSafe handling of radioactive sourcesFacilitiesMonitoringQuality of containersArrangements for storageDocumentation

•Audits

Good Good LuckLuck