Radiation Safety Program Radiation Safety Program Overview and TerminologyOverview and Terminology

Robert Forrest, CHP

Radiation Safety OfficerEnvironmental Health and Radiation Safety

RememberRemember

Don’t be the RSO!

Who gets the blame?Who gets the blame?

“The licensee, through its Radiation Safety Officer, failed to ensure that radiation safety activities were being performed in accordance with the

established procedures.”

Radiation SymbolRadiation Symbol

New ISO Radiation SymbolNew ISO Radiation Symbol

Public PerceptionsPublic Perceptions

Nuclear Weapons

Cancer

Invisible, industrial hazard

Recommending Groups Recommending Groups

ICRP - International Commission on Radiological Protection

NCRP - National Council on Radiological Protection

ICRU - International Commission on Radiological Units

BEIR - Biological Effects of Ionizing Radiation Committee

Regulatory AgenciesRegulatory Agencies

NRC

DOE

DOT

EPA

FDA

OSHA

Naval Reactors

US Post Office

States

Local Municipalities

Main Regulatory AuthoritiesMain Regulatory Authorities

NRC regulates:

Byproduct material

Reactors and Fuel

State regulates:

Accelerator material

Energized Equipment

Agreement States vs. NRCAgreement States vs. NRC

State accepts NRC rules

State can be more restrictive

NRC retains control of Reactors and Fuel

Radiation Safety ProgramRadiation Safety Program

Commensurate with scope of activities

Governed by:

Regulations

License Conditions

Local Policies and Procedures

NRC LicensesNRC Licenses

License authorizes who, what, where and how

Requirements above and beyond regulations

Includes all correspondence back and forth between licensee and regulatory agency

NRC LicensesNRC Licenses

Specific License

Names authorized users

Requires amendments to change small items

Broad Scope License

Licensee can designate authorized users

Licensee can modify “ministerial” items

Organizational Organizational ResponsibilitiesResponsibilities

Executive Management

Radiation SafetyCommittee

Radiation Safety Officer

TerminologyTerminology

Radioactive Material

Radiation

Contamination

Half-life

Activity

Radioactive MaterialRadioactive Material(unstable material which spontaneously transforms (unstable material which spontaneously transforms

usually emitting some type of radiation)usually emitting some type of radiation)

RadiationRadiation(particulate or electromagnetic energy emitted during (particulate or electromagnetic energy emitted during

radioactive decay)radioactive decay)

ContaminationContamination(radioactive material spread into an unwanted place)(radioactive material spread into an unwanted place)

Half-LifeHalf-Life

The time required for any given radioisotope to decrease to one half of its original activity.

T1/2 = ln 2 /

The radiological half-lives for Tc-99m and

I-131 are 6 hours and 8 days, respectively.

Half lifeHalf life

Tc-99m Decay

0

500

1000

0 10 20 30 40

Hours

Ato

ms

Half lifeHalf life

Tc-99m Decayλ = 0.116 hr-1

1

100

10000

0 12 24 36 48 60

Hours

Ato

ms

ActivityActivity the rate of decay * the number of atomsthe rate of decay * the number of atoms

A = A = *N*N

Current Unit

Curie (Ci)

1Ci = 3.7 E 10 Bq

SI Unit

Becquerel (Bq)

1 Bq = 1 d/s

1 Bq = 2.7 E -11 Ci

ActivityActivity

A = *N

If N = 1x109 atoms

Tc-99m, A = (0.116 hr-1)(1x109 atoms)

A = 3.22 x 104 Bq (0.87 μCi)

I-131, A = (3.61x10-3 hr-1)(1x109 atoms) A = 1 x 103 Bq (0.027 μCi)

ActivityActivity

Biomedical Research uses Ci quantities

Nuclear Medicine uses mCi quantities– Bone Scan uses 25 mCi of Tc-99m

Radiation Oncology uses mCi-Ci quantities– LDR implants use 100-200 mCi of Cs-137– HDR implants use 10 Ci Ir-192

Sources used in Radiation WorkSources used in Radiation Work

Biomedical Research

C-14, H-3, I-125, P-32, S-35

Nuclear Medicine

Tc-99m and I-131

both use unsealed sources

contamination usually biggest problem

Sources Used in Radiation WorkSources Used in Radiation Work

Radiology

x-ray equipment

Oncology

Cs-137, Ir-192, Pd-103, x-ray equip. & linacs

machine and sealed sources

external exposure is the biggest concern

Annual Average Background Annual Average Background Dose DistributionDose Distribution

(total =360 mrem)(total =360 mrem)

Radon55%

Other3%

Terrestrial8%

Cosmic8%

Internal11%

Nuclear Medicine

4%Medical Xrays

11%

Acute Radiation EffectsAcute Radiation Effects

Minor blood changes 25,000 mrem

Hemopoietic Syndrome 200,000 mrem

Erythema 200-300,000 mrem

LD50,30 450,000 mrem

Delayed Radiation EffectsDelayed Radiation Effects

Cancer

Genetic Effects

Extrapolating Risk FactorsExtrapolating Risk Factors

KnownEffects

X X

X

X

X

X

Effect

Radiation Dose

Extra

polated R

isk

OccupationalDose Levels

Dose LimitsDose Limits(10 CFR 20.1201-8)(10 CFR 20.1201-8)

Total Effective Dose Equivalent 5000 mrem

Total Organ Dose Equivalent 50,000 mrem

Lens of the Eye 15,000 mrem

Skin and Extremities 50,000 mrem

Declared Pregnant Worker 500 mrem

Minor 500 mrem

General Public 100 mrem

Declared Pregnant WorkerDeclared Pregnant Worker

a woman who has voluntarily informed her employer, in writing, of her pregnancy and the estimated date of conception.

licensee shall make efforts to avoid substantial variations in monthly exposures

Dosimeter FiltersDosimeter Filters

Open window

Copper

Tin

Image filter

Al2O3 strip

Low energy - static

Radiation

Low energy - dynamic

Radiation

Pregnant PatientPregnant Patient

Get and read Wagner’s book

If clinically indicated, do the study

Steps should be taken to lower dose if possible

When counseling, use numbers that are understandable

Pregnant PatientPregnant Patient

Effective Doses to Patients Effective Doses to Patients from Diagnostic Studiesfrom Diagnostic Studies

DEXA < 1mrem

Chest x-ray ~ 10 mrem

AP abdomen ~ 70 mrem

Upper GI ~ 300 mrem

CT abdomen ~ 700-1000 mrem

Coron. Angioplasty ~ 2200 mremSource: Hall, Radiobiology for the Radiologist, 5th edition

Effective Doses to Patients Effective Doses to Patients from Diagnostic Studiesfrom Diagnostic Studies

4 mCi Tc MAA ~ 160 mrem

15 mCi Tc DTPA ~ 270 mrem

25 mCi Tc MDP ~ 525 mrem

15/40 mCi Tc Mibi ~ 1700 mrem

10 mCi 18F-FDG ~ 700 mrem

15 mCi FDG PET/CT ~2500 mremSource: ICRP 80, Radiation Dose to Patients from Radiopharmaceuticals

Radiation Induced Skin Radiation Induced Skin Injuries from FluoroscopyInjuries from Fluoroscopy

Skin injuries are the most likely injury resulting from diagnostic procedures.

Fluoro unit outputs average to 1-2 R/min

Fluoro unit outputs can go up to 10 R/min

High Dose modes can go up to 20 R/min

No limits on Cine or digital recordings

Transient erythema at 200 rads

Radiation-Induced Skin Injuries [14, 17]

•Skin “burns” are rare but possible for prolonged fluorocardio & other interventions•FDA has received 60 reports of burns since 1994 ~ 8.6 reported burns per year•How many radiation burns are not reported?

Figure from [17]

Example of chronic skin injury due to cumulative skin dose of ~20,000 mGy (20 Gy) from coronary

angiography and x2 angioplasties

21 months after first procedure, base of ulcer exposes spinous process

estimated 25 Gy dose estimated 25 Gy dose Erythemia at 3 weeksErythemia at 3 weeks

Ulceration at 5 monthsUlceration at 5 months

Debridement at 6.5 monthsDebridement at 6.5 months

Nuclear Medicine Authorized Nuclear Medicine Authorized UsersUsers

Requirements in 10 CFR 35

You are NOT an Authorized User UNTIL approved:

• specific license: NRC

• broad scope license: Rad. Safety Committee

Accurate AdministrationsAccurate Administrations

The department must have a program in place to ensure that the following are correct, as directed by the Authorized User:

• patient identity• radiopharmaceutical• dosage

Medical EventMedical Event(formerly misadministration)(formerly misadministration)An administration involving the wrong individual, wrong radiopharmaceutical, wrong route of administration

AND

the dose to the patient >5 rem EDE or 50 rem to any organ.

Medical EventMedical Event(formerly misadministration)(formerly misadministration)An administration to the correct patient when the total dosage > +/- 20% of the prescribed dosage or the prescribed dosage range

AND

the dose to the patient differs by more than 5 rem EDE or 50 rem to any organ than would have resulted from the prescribed dosage.

Medical Event ExamplesMedical Event Examples

1) Therapy dose mishaps are generally medical events

2) Diagnostic dose events are generally not medical events.

General Radiation SafetyGeneral Radiation Safety

External Exposure Control:

• Time

• Distance

• Shielding

Internal Exposure Control

• Contamination prevention

TimeTime

Minimize time spent with patients after being dosed

may not be practical

DistanceDistance

Maximize distance from patient to greatest extent possible

monitor with electronic dosimeter to find where max. dose is received

DistanceDistance

Maximize distance from patient to greatest extent possible

monitor with electronic dosimeter to find where max. dose is received

Distance - exampleDistance - example

From a patient with a typical stress dosage, a worker at edge of treadmill receives about 9 mR/hr.

Distance - exampleDistance - example

At 1 meter from the treadmill, the exposure rate is about 2 mR/hr.

ShieldingShielding

Beta Shielding

low Z material (plexi-glass)

thickness > beta particle range

Gamma Shielding

high Z material

calculate required thickness

Lead ApronLead Apron

Standard apron thickness is 0.5 mm Pb equival.

PA requires at least 0.25 mm.

Attenuation of 0.5 mm Pb:

Cs-137 = 6%

Tc-99m = 74%

x-rays = >95%

Internal Exposure Control:Internal Exposure Control:Contamination PreventionContamination Prevention

Gloves and lab coat

Personnel surveys: hands, feet, clothing

No eating, drinking, smoking, or applying cosmetics in licensed areas.

Make sure all radioactive material containers are properly closed and carefully handled.

InspectionsInspections

Be honest

Answer questions which are asked

Have organized records

EmergenciesEmergencies

Spills are the most common problem

Must have procedures in place

Will demonstrate program weaknesses

SummarySummary

Know the regulationsKnow license requirements and minimize commitmentsKnow the regulatorsGet program supportStay organizedBe honest and admit your mistakes

When in doubt, ask your RSO

RememberRemember

Don’t be the RSO!