dr. mohammed alnafea [email protected] radiation protection in nuclear medicine

Dr. Mohammed AlnafeaDr. Mohammed [email protected]@ksu.edu.sa

RADIATION PROTECTION IN NUCLEAR MEDICINE

Outline Outline Introduction to Radiation SafetySocietal Benefits of RadiationSources of RadiationOccupational Risks Protection MethodsPersonal Dosimetry Instrumentation Demonstration

2 6th lecture RAD 311

A Typical Radiation A Typical Radiation SituationSituation

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 3113

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 LawThe 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.


The Inverse Square LawThe 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 I 1/r 1/r22


Types of Ionizing Radiation

Alpha (heavy ion, damaging, not penetrating).

Beta (electron, medium damage, little penetration)

Gamma (photon, less damage, penetrating)

X-ray (photon, less damage, penetrating)


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??


Sources of Ionizing Radiationto General Public

Natural (82%)Radon ( 55 %)Cosmic ( 8 %)Terrestrial ( 8 %)Internal ( 11 %)


Sources of Radiation Artificial (18%)

x-ray ( 11 %)nuclear medicine ( 4 %)consumer products ( 3 %)nuclear power ( <1 %)fallout ( <1 %)


Occupational Exposure Limits(Whole Body)

“Trained” Radiation Worker 5 rem Pregnant Radiation Worker 0.5 rem

General Public 0.1 rem


What is a rem ???

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

tissuetissue

What level of radiation is safe ??

Consensus of Scientific Opinion:5 rem annual exposure to an adult

Acute Radiation Dose Effects 450 rem LD 50/60 200 rem Hemopoietic Syndrome 100 rem Acute Radiation Syndrome 50 rem 1st identifiable sign of

effects 5 rem Yearly dose limit for

Radiation Worker. 0.5 rem Gestation dose limit


However, the concept of ALARA must also be

implemented

What is ALARA?

ALARA As Low As Reasonable Achievable


ALARA for External Radiation

ProtectionMinimize Time in Radiation Field

Maximize Distance from Radiation Source

Use of Shielding


Examples of External Radiation

Diagnostic X-rayDiagnostic Nuclear MedicineTherapeutic Nuclear Medicine Radiotracer uses in Research

(e.g., C-14, H-3, P-32, S-35, P-33, I-125)


ALARA for Internal Radiation

Protection

Use of protective clothing Spill preventionUse of fume hoodsRespiratory protection if neededEngineering controls if neededMonitor for loose contaminationNo eating, drinking, smoking in laboratory


Early Protective Suit•Lead glasses

•Filters

•Tube shielding

•Early personal “dosemeters”

•etc.


Examples of Internal Radiation

ResearchAccidental Intake (Ingestion, Inhalation)

Nuclear MedicineAccidental intake Misadministration


Spill ResponseSpill Response


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 Monitor all persons and define the area of contaminationcontamination

Basic Principals of Radiation Basic Principals of Radiation ProtectionProtection

JustificationBenefit > risk

OptimisationDoses as low as reasonably achievable

LimitationAbsolute legal limits for staff and publicReference levels as guidance for patients.


ALARAALARA

As Low As Reasonably Achievablemeans making every reasonable effort to

maintain exposures to radiation as far below the dose limits as is practicable.

How?How?Time, Distance and Shielding

Reduce time exposedIncrease distance from sourceUse shielding between you and the source

Minimize internal contaminationPlan work


RadiationRadiation ProtectionProtection


Decrease Decrease TimeTime

Increase Increase DistanceDistance

Increase Increase ShieldingShielding

Basic Principles

Time

Distance

Shielding


Distance

•Double distance = 1/4 dose

•Triple distance = 1/9th dose.



2

20

0 r

rII

2

20

0 r

rDD

The radiated energy can be considered to be spread over a sphere of area 4r2 at any distance r from the source. Since the radiation intensity is equal to the energy per unit area :

If the radiation intensity is I0 at a distance r0 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 :

24Energy


Radiation ProtectionRadiation ProtectionReducing Radiation ExposureReducing Radiation Exposure

DistanceMaintain 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


Lead Apron StorageLead Apron Storage

Always return to hangerDo not

folddump on floor and run

trolleys over the top of them!!!

X-ray will check annuallyBut if visibly damaged,

ask X-ray to check them.


Detecting and Measuring Detecting and Measuring RadiationRadiation


InstrumentsInstrumentsLocate contamination - GM Survey Meter Locate contamination - GM Survey Meter

(Geiger counter)(Geiger counter)Measure exposure rate - Ion ChamberMeasure exposure rate - Ion Chamber

Personal Dosimeters - measure doses to staffPersonal Dosimeters - measure doses to staffRadiation Badge - Film/TLDRadiation Badge - Film/TLDSelf reading dosimeter (analog & digital)Self reading dosimeter (analog & digital)

Measurement of Radiation Exposure ReceivedPersonnel Monitoring Device - External

Sources of RadiationBioassay - Internal Radiation)

blood sampleurine samplethyroid monitoring


My time is up!

Any questions ??


dr. mohammed alnafea [email protected] radiation protection in nuclear medicine

Documents

source of radiation

radiation source

1r26th lecture rad

radiation exposure

radiation beam

human tissue6th lecture

level of radiation

ionizing radiation field