Radiation protection & safety in nuclear medicinePresentation Transcript
Radiation Protection & Safety in Nuclear Medicine Y4S2 Dr.Damayanthi Nanayakkara MBBS, MPhil(UK), PhD Senior Lecturer in Nuclear Medicine
RADIATION• Public perception about anything “NUCLEAR” have been very negative• To counter balance irrational public fears we need to educate professionals & Public• Radiation use & Radiation protection
Radiation• What is radiation?• What forms of radiation are used in Nuclear Medicine?• How safe is radiation?• Why dose radiation need to be handle carefully?• How do you protect from unnecessary radiation or minimize radiation exposure?
What is radiation? Electrons Nucleus (P/N)ATOM
• What forms of radiation are used in Nuclear Medicine?
• The sources used in nuclear medicine are mainly unsealed sources.• Sealed sources are used for calibration and QC of equipment.• Several types of unsealed sources (radiopharmaceuticals) are used in different applications both in diagnosis and therapy.• Pure -emitter e.g. Tc-99m, In-111, Ga-67, I-123• Positron emitters (ß+) e.g. F-18• & ß- emitters (e.g. I-131)• Pure ß- emitters (e.g. P-32, Sr-89, Y-90, Er-169)• -emitters (e.g. At-211, Bi-213)
Typical Mo-Tc Generator
How safe is radiation?• Effects of radiation High dose – deterministic effects • Radiation sickness • Skin burns • Impaired fertility • Hair loss • Damage to eyes Low dose – stochastic effects • Cancer induction • Genetic defects *Effects is proportional to the dose, duration, mode of isotope decay etc.
• Why dose radiation need to be handle carefully?
Radiation doses• Natural Background – 2 mSv / year in UK – 4mSv/year in Italy – 8mSv/year in Finland - 8mSv Kerala (thorium)• Concorde UK to US 0.2mSv• General population – 1mSv/year not exceeding 5mSV for next 5 years• Radiation workers – 1.5mSv per year not exceeding 20mSV for next 5 years
Who Exposed to Radiation?1. Radiation workers2. General Public including doctors , nurses except those are working with radiation3. Patients
International Commission of Radiation Protection (ICRP)• Guidelines• Annual dose limits• In many NM procedures the radiation dose is actually lower than conventional x ray procedures• Cost/ benefit & Risk/ benefit
• The operating philosophy in radiation protection is “maintaining radiation exposure As Low As Reasonably Achievable ALARA concept
Radiation doses• 100mSv- temporary sterility• 500mSV- damge to lense• 3 SV – Erythema – Hair loss – Sterility• 2-5 Sv - death in several weeks• 5-10 Sv death in days• 20 Sv death in hours
Factors affect the radiation dose• Decay scheme of an Isotope(unstable) 99MO 99mTc (6h) 99Tc (stable)42 43 43 (metastable) Energy
Factors affect the radiation dose• Energy• Administered activity• Absorbed dose• Tissue factors• Biological status of the interested organ• Other drugs/ compounds• Waste disposal
What forms of radiation are used in Nuclear Medicine?• Nuclear Medicine – Unsealed radioactive materials (radionuclide) – Natural radiation – Emits alpha( ),Beta(β) and gamma( ) X ray - is produced in a machine ,high voltage current is passed between the anode and the cathode
Medical exposure chest 0.02mSv DMSA 0.7mSv skull 0.15mSv MAG3/DTPA 3.0mSvabdomen 1.0mSv Lumbar 2.0mSv Bone 3.0mSv spine Cardiac 4.0mSv IVU 3.5mSv Ba meal 3.0mSv Thyroid 1.0mSvBa enema 7.0mSv Lung 1.0mSv CT head 3.5mSv perfusionCT chest 8.0mSv CT liver 10.0mSn
The radiopharmaceuticals can be classified as follows: • ready-to-use e.g. 131 IMIBG, 131 I, 201Tl-chloride, 111In- DTPA • instant kits for preparation of products e.g. 99mTc-MDP, 99mTc-MAA, 99mTc-HIDA, 99mTc- DMSA, 99mTc-DTPA • kits requiring heating e.g. 99mTc-MAG3, 99mTc-MIBI • products requiring significant manipulation e.g. labelling of blood cells (RBC, WBC, monoclonal antibodies etc.)
What protection techniques are used to protect patients and workers in Nuclear Medicine and radio nuclide therapy procedures?• Diagnostic nuclear medicine, – Either radioactive material or a labeled product of radionuclide are injected into or swallowed by the patient. – Or the patient may breathe a radioactive gas or aerosol. – Patient become temporarily a radioactive source• Radiation emits from the patient• Using a gamma camera these emitted radiation will detct and present as a pictorial image or show the location of the radioactive material in the patient• In these cases, the patient becomes a source of radiation and remains so until the radioactive material decays or is excreted from the body
RadioNuclide therapy• Unsealed radioactive materials, in the form of compounds or elemental radionuclides, are injected into or swallowed by the patient – Because of the chemical nature of the material, it will be taken up by specific organs or tissues to disrupt the growth of tumors and cancers Eg. 131I – Thyroid cancer, thyrotoxicosis. 90Y -Rh. Arthritis/ hemophiliac arthritis 32P - Bone pain/ PRV 188 Re lipiodol – Liver cancer 111I-Octreotide - Neuroendocrine tumors
• For patients, radiation protection is ensured – (1) by performing only those tests and treatments that are necessary, – (2) by using calibrated equipment to provide the best test results or treatment outcomes, – (3) by using standard tests, procedures, and administrative controls, and – (4) by having knowledgeable and trained personnel. – The overriding principal is that any test or treatment should offer the maximum benefit to the patient and limit the radiation exposure.
• Because of the nature of nuclear medicine practice we have to use radioactive materials and the staff expect to receive radiation exposure in the course of their duties• To keep exposures As Low As Reasonably Achievable, staff receive special training in procedures and have available equipment that will provide shielding to keep their exposures below regulatory guidelines – Training, – Proper equipment, – Procedure guidelines – Appropriate shielding Minimizes the radiation burden to workers when working with radiation sources, including the patient.
• lead syringe holders & syringe shields reduce the technologists‘/ doctors hand and body exposure while injecting patients with radioactive material• Portable lead panels on wheels are used to reduce the exposure of the technologists and staff when procedures are carried out• Lead and concrete are used in the walls around nuclear medicine clinics and treatment rooms to shield adjacent areas occupied by the other staff and public
3 Golden Rules in RP• To protect staff and patients against the effects of unwanted radiation 3 important factors should be considered – Distance – Shielding – Time
RP- Distance• All magnetic radiation obey the inverse square law – Doubling your distance from a source reduces the intensity of radiation to one quarter
Shielding• The damage that is caused to human tissues by ionizing radiation during medical exposure can be minimized using shielding• Lead shielding (syringe shields, lead glasses, lead viewing panels, lead pots, lead apron etc
Time• The greater the time that you are exposed to a radiation the greater the radiation dose you will receive• When working with radiation sources which emits gamma rays you have to keep the source in a lead shield for as long as possible
Other aspects• Isolation until decay• Patient education• Monitoring – Self monitoring – Area – Patient monitoring• Enforce rules and regulations• Follow the rules and regulations
• Medical use of ionizing radiation is a large contributor to the overall annual dose to a person• It is important to reduce the overall dose to the general public /patents and the staff – 100-250 new cases of cancer in UK are due to unnecessary diagnostic procedures
Risk of cancer to children• Radiation risks in childhood are greater than in adult (less than 5 y risk is >20 times)• Reasons – Delayed effects of cancer induction, longer time period for the risk to be expressed – During adulthood likelihood of having children is higher, so genetic effects is much greater than for adults
Justification• Working knowledge of the patents condition, dose limits for the procedure can eradicate unnecessary exposure• Avoid clinically unhelpful examinations(20% radiological investigations are inappropriate)• Avoid unnecessary large dose to a patent• Previous reports• Avoid unnecessary repeats because previous study has been lost
• All doctors have a responsibility for reducing patient dose (not just the NM physicians & Radiologists) – CLINICAL JUSTIFICATION – DOSE JUSTIFICATION• The use of radiation must produce a net benefit to the patients health• Procedure involving radiation should only be carried out when it is likely to change a patients’ cause of treatment
Civil defense symbol for fallout shelters Radiation Warning Symbol (Trefoil) safety whereas the radiation warning A fallout shelter represents symbol represents a hazard.
• University of California• Why did they chose this symbol? There is no answer, only speculation.• It was used to warn of spinning propellers???• The central circle is a radiation source and that the three blades represent radiation, perhaps one blade each for alpha, beta and gamma• Whatever the reason, it was a good choice because it is simple and readily identifiable
Nuclear Medicine Technicians working station
Typical fume hood
Waste disposal- Hot Lab
RADIATION SAFETY PRACTICE IN NUCLEAR MEDICINE• use international radiation warning symbol (trefoil)• Radiation monitors are to be worn by staff at all times when in radiation areas• Eating, drinking, smoking and the use of cosmetics are prohibited in the radio pharmacy and in any room where unsealed radionuclide are used
• All containers used for radioactive materials should be clearly labeled• All such containers are to be adequately sealed and shielded at all times• if possible, tongs or forceps for vials and syringe shields should be used• All work surfaces should be covered with absorbent paper• Pipetting by mouth of any radioactive substance is strictly forbidden
• Staff involved in radiopharmaceutical preparation must check their hands for contamination before leaving the radio pharmacy suite• All radiopharmaceutical preparation and administration procedures should be carried out behind suitable lead or lead-glass shielding,• disposable gloves and a radiation monitor should be worn, and preferably a laboratory coat• Gloves should be removed in the proper surgical manner (with one glove held inside the other) and disposed of correctly as radioactive waste after use• All radioactive sources are to be returned to safe storage immediately when no longer required
• All operations involving radioactive gases or aerosols should be carried out in a fume hood or similar ventilated device to prevent airborne contamination• All staff should be familiar with radiation accident and decontamination procedures Packaging and containers for radioactive material must be checked for contamination on opening.• Containers, lead pots, etc., that are no longer contain radioactive material and require to be disposed of must have any radiation warning labels removed or obliterated before disposal