Transcript Training
Radiation Safety Program Overview and Terminology Robert Forrest, CHP Radiation Safety Officer Environmental Health and Radiation Safety
Remember
Don’t be the RSO!
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 Symbol
New ISO Radiation Symbol
Public Perceptions Nuclear Weapons Cancer Invisible, industrial hazard
ICRP Recommending Groups NCRP ICRU BEIR International Commission on Radiological Protection National Council on Radiological Protection International Commission on Radiological Units Biological Effects of Ionizing Radiation Committee
NRC DOE DOT EPA FDA Regulatory Agencies OSHA Naval Reactors US Post Office States Local Municipalities
Main Regulatory Authorities NRC regulates: State regulates: Byproduct material Reactors and Fuel Accelerator material Energized Equipment
Agreement States vs. NRC State accepts NRC rules State can be more restrictive NRC retains control of Reactors and Fuel
Radiation Safety Program Commensurate with scope of activities Governed by: Regulations License Conditions Local Policies and Procedures
NRC 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 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 Responsibilities Executive Management Radiation Safety Officer Radiation Safety Committee
Terminology Radioactive Material Radiation Contamination Half-life Activity
Radioactive Material (unstable material which spontaneously transforms usually emitting some type of radiation)
Radiation (particulate or electromagnetic energy emitted during radioactive decay)
Contamination (radioactive material spread into an unwanted place)
Half-Life The time required for any given radioisotope to decrease to one half of its original activity.
T 1/2 = ln 2 / The radiological half-lives for Tc-99m and I-131 are 6 hours and 8 days, respectively.
Half life
Tc-99m Decay
1000 500 0 0 10 20
Hours
30 40
Half life
Tc-99m Decay λ = 0.116 hr-1
10000 100 1 0 12 24 36
Hours
48 60
Activity the rate of decay * the number of atoms A = *N Current Unit SI Unit Curie (Ci) 1Ci = 3.7 E 10 Bq Becquerel (Bq) 1 Bq = 1 d/s 1 Bq = 2.7 E -11 Ci
Activity A = *N If N = 1x10 9 atoms Tc-99m, A = (0.116 hr -1 )(1x10 9 atoms) A = 3.22 x 10 4 Bq (0.87 μCi) I-131, A = (3.61x10
-3 hr -1 )(1x10 9 atoms) A = 1 x 10 3 Bq (0.027 μCi)
Activity Biomedical Research uses m 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 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 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 Dose Distribution (total =360 mrem)
Cosmic 8% Internal 11% Nuclear Medicine 4% Medical Xrays 11% Terrestrial 8% Other 3% Radon 55%
Acute Radiation Effects Minor blood changes Hemopoietic Syndrome Erythema LD 50,30 25,000 mrem 200,000 mrem 200-300,000 mrem 450,000 mrem
Delayed Radiation Effects Cancer Genetic Effects
Effect Extrapolating Risk Factors X X X X X X Known Effects Occupational Dose Levels Radiation Dose
Dose Limits (10 CFR 20.1201-8) Total Effective Dose Equivalent Total Organ Dose Equivalent Lens of the Eye Skin and Extremities Declared Pregnant Worker Minor General Public 5000 mrem 50,000 mrem 15,000 mrem 50,000 mrem 500 mrem 500 mrem 100 mrem
Declared 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
Copper Tin
Dosimeter Filters
Open window Al 2 O 3 strip Image filter
Low energy - static
Radiation
Low energy - dynamic
Radiation
Pregnant 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 Patient
Effective Doses to Patients from Diagnostic Studies DEXA Chest x-ray AP abdomen Upper GI CT abdomen < 1mrem ~ 10 mrem ~ 70 mrem ~ 300 mrem ~ 700-1000 mrem Coron. Angioplasty ~ 2200 mrem Source: Hall, Radiobiology for the Radiologist, 5 th edition
Effective Doses to Patients from Diagnostic Studies 4 mCi Tc MAA 15 mCi Tc DTPA 25 mCi Tc MDP 15/40 mCi Tc Mibi 10 mCi 18F-FDG ~ 160 mrem ~ 270 mrem ~ 525 mrem ~ 1700 mrem ~ 700 mrem 15 mCi FDG PET/CT ~2500 mrem Source: ICRP 80, Radiation Dose to Patients from Radiopharmaceuticals
Radiation Induced Skin Injuries 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] Figure from [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?
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 Erythemia at 3 weeks
Ulceration at 5 months
Debridement at 6.5 months
Nuclear Medicine Authorized Users Requirements in 10 CFR 35 You are NOT an Authorized User UNTIL approved: • specific license: NRC • broad scope license: Rad. Safety Committee
Accurate 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 Event (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 Event (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 Examples 1) Therapy dose mishaps are generally medical events 2) Diagnostic dose events are generally not medical events.
General Radiation Safety External Exposure Control: • Time • Distance • Shielding Internal Exposure Control • Contamination prevention
Time Minimize time spent with patients after being dosed may not be practical
Distance Maximize distance from patient to greatest extent possible monitor with electronic dosimeter to find where max. dose is received
Distance Maximize distance from patient to greatest extent possible monitor with electronic dosimeter to find where max. dose is received
Distance - example
From a patient with a typical stress dosage, a worker at edge of treadmill receives about 9 mR/hr.
Distance - example
At 1 meter from the treadmill, the exposure rate is about 2 mR/hr.
Shielding Beta Shielding low Z material (plexi-glass) thickness > beta particle range Gamma Shielding high Z material calculate required thickness
Lead 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 = x-rays = 74% >95%
Internal Exposure Control: Contamination 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.
Inspections Be honest Answer questions which are asked Have organized records
Emergencies Spills are the most common problem Must have procedures in place Will demonstrate program weaknesses
Summary Know the regulations Know license requirements and minimize commitments Know the regulators Get program support Stay organized Be honest and admit your mistakes When in doubt, ask your RSO
Remember