Dr. Mohammed Alnafea RADIATION PROTECTION IN NUCLEAR MEDICINE

Outline ä Introduction to Radiation Safety ä Societal Benefits of Radiation ä Sources of Radiation ä Occupational Risks ä Protection Methods ä Personal Dosimetry ä Instrumentation Demonstration 2 6th lecture RAD 311

A Typical Radiation Situation Firstly there is a source of radiation, secondly a radiation beam and thirdly some material which absorbs the radiation. So the quantities which can be measured are associated with the source, the radiation beam and the absorber. 6th lecture RAD 311 3

4 Radiation Exposure, Dose and Quantity Exposure is an index of the ability of a radiation field to ionize air. Dose is a measure of the energy imparted to matter, per unit mass, when an ionizing radiation field interacts with matter. Quantity of radioactive material is expressed as “activity”, the number of nuclear disintegrations that occur in a sample per second. 6th lecture RAD 311

The Inverse Square Law what happens as we move our absorber away from the radiation source. In other words think about the influence of distance on the intensity of the radiation beam. You will find that a useful result emerges from this that has a very important impact on radiation safety. The radiation produced in a radioactive source is emitted in all directions. We can consider that spheres of equal radiation intensity exist around the source with the number of photons/particles spreading out as we move away from the source. 6th lecture RAD 311 5

The Inverse Square Law Consider an area on the surface of one of these spheres and assume that there are a certain number of photons/particles passing though it. If we now consider a sphere at a greater distance from the source the same number of photons/particles will now be spread out over a bigger area. Following this line of thought it is easy to appreciate that the radiation intensity, I will decrease with the square of the distance, r from the source, i.e. I  1/r 2 I  1/r 2 6th lecture RAD 311 6

Types of Ionizing Radiation ç Alpha (heavy ion, damaging, not penetrating). ç Beta (electron, medium damage, little penetration) ç Gamma (photon, less damage, penetrating) ç X-ray (photon, less damage, penetrating) 7 6th lecture RAD 311

Ionizing Radiation’s Interaction With Human Tissue May cause free radicals - Indirect Effects (self-repair mechanism) May cause DNA damage - Direct Effects (self-repair mechanism) Hence, a threshold effect?? 8 6th lecture RAD 311

Sources of Ionizing Radiation to General Public Natural(82%) Radon ( 55 %) Cosmic ( 8 %) Terrestrial ( 8 %) Internal( 11 %) 9 6th lecture RAD 311

Sources of Radiation Artificial(18%) x-ray( 11 %) nuclear medicine( 4 %) consumer products( 3 %) nuclear power( <1 %) fallout( <1 %) 10 6th lecture RAD 311

Occupational Exposure Limits (Whole Body) “Trained” Radiation Worker5 rem Pregnant Radiation Worker0.5 rem General Public0.1 rem 11 6th lecture RAD 311

What is a rem ??? A rem is a unit of measurement for radiation delivered to human tissue

What level of radiation is safe ?? Consensus of Scientific Opinion: 5 rem annual exposure to an adult

Acute Radiation Dose Effects 450 remLD 50/ remHemopoietic Syndrome 100 remAcute Radiation Syndrome 50 rem1st identifiable sign of effects 5 remYearly dose limit for Radiation Worker. 0.5 rem Gestation dose limit 14 6th lecture RAD 311

However, the concept of ALARA must also be implemented What is ALARA?

ALARA As Low As Reasonable Achievable 16 6th lecture RAD 311

ALARA for External Radiation Protection å Minimize Time in Radiation Field å Maximize Distance from Radiation Source å Use of Shielding 17 6th lecture RAD 311

Examples of External Radiation å Diagnostic X-ray å Diagnostic Nuclear Medicine å Therapeutic Nuclear Medicine å Radiotracer uses in Research (e.g., C-14, H-3, P-32, S-35, P-33, I-125) 18 6th lecture RAD 311

ALARA for Internal Radiation Protection å Use of protective clothing å Spill prevention å Use of fume hoods å Respiratory protection if needed å Engineering controls if needed å Monitor for loose contamination å No eating, drinking, smoking in laboratory 19 6th lecture RAD 311

Early Protective Suit Lead glasses Filters Tube shielding Early personal “dosemeters” etc. 20 6th lecture RAD 311

Examples of Internal Radiation å Research å Accidental Intake (Ingestion, Inhalation) å Nuclear Medicine Accidental intake Misadministration 21 6th lecture RAD 311

Spill Response 6th lecture RAD On Skin—flush completely. On Clothing—remove. If Injury—administer first aid. Radioactive Gas Release—vacate area, shut off fans, post warning. Monitor all persons and define the area of contamination Monitor all persons and define the area of contamination

Basic Principals of Radiation Protection Justification Benefit > risk Optimisation Doses as low as reasonably achievable Limitation Absolute legal limits for staff and public Reference levels as guidance for patients. 23 6th lecture RAD 311

ALARA As Low As Reasonably Achievable means making every reasonable effort to maintain exposures to radiation as far below the dose limits as is practicable.How? Time, Distance and Shielding Reduce time exposed Increase distance from source Use shielding between you and the source Minimize internal contamination Plan work 24 6th lecture RAD 311

RadiationProtection Radiation Protection 6th lecture RAD Decrease Time Decrease Time Increase Distance Increase Distance Increase Shielding Increase Shielding

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Basic Principles  Time  Distance  Shielding 27 6th lecture RAD 311

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Distance Double distance = 1 / 4 dose Triple distance = 1 / 9 th dose. 29 6th lecture RAD 311

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6th lecture RAD The radiated energy can be considered to be spread over a sphere of area 4  r 2 at any distance r from the source. Since the radiation intensity is equal to the energy per unit area : If the radiation intensity is I 0 at a distance r 0 from the source, the intensity I at any other distance r will be given by : Since the radiation dose is proportional to the intensity, the dose D can be calculated by the same type of relationship :

6th lecture RAD Radiation Protection Reducing Radiation Exposure Distance Maintain maximal practical distance from radiation source To Limit Care giver Dose to 5 rem Distance Rate Stay time 1 ft 12.5 R/hr 24 min 2 ft 3.1 R/hr 1.6 hr 5 ft 0.5 R/hr 10 hr 8 ft 0.2 R/hr 25 hr

Shielding 34 6th lecture RAD 311

Shielding 35 6th lecture RAD 311

Lead Apron Storage Always return to hanger Do not fold dump on floor and run trolleys over the top of them!!! X-ray will check annually But if visibly damaged, ask X-ray to check them. 36 6th lecture RAD 311

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Detecting and Measuring Radiation 6th lecture RAD Instruments Instruments Locate contamination - GM Survey Meter (Geiger counter) Locate contamination - GM Survey Meter (Geiger counter) Measure exposure rate - Ion Chamber Measure exposure rate - Ion Chamber Personal Dosimeters - measure doses to staff Personal Dosimeters - measure doses to staff Radiation Badge - Film/TLD Radiation Badge - Film/TLD Self reading dosimeter (analog & digital) Self reading dosimeter (analog & digital)

6th lecture RAD

6th lecture RAD

6th lecture RAD

Measurement of Radiation Exposure Received å Personnel Monitoring Device - External Sources of Radiation å Bioassay - Internal Radiation) blood sample urine sample thyroid monitoring 43 6th lecture RAD 311

My time is up! Any questions ?? 44 6th lecture RAD 311