Radiation Protection(1) By: Prof. Dr. Hosna Moustafa Cairo University, Egypt

OBJECTIVES of Radiation Protection To become familiar with the requirement for medical exposure in nuclear medicine: responsibilities. justification. optimization. guidance level. Dose to public , workers , children, pregnant and lactating women.

Effects of Radiation (A) Stochastic effects: The probability of observing spontaneous mutations increases linearly with radiation dose. (B) Deterministic effects: After a threshold, the severity of radiation illness increases nonlinearly with radiation dose.

“ALARA” philosophy ALARA philosophy of radiation protection is based upon the fact that exposure to radiation should be (as low as reasonably achievable). Safe management The safety of individuals and populations depends on the of exposure to ionizing radiation. For maximum safety, dose limits for radiation workers and the general public are based on “non- threshold, linear dose- effect relationship”.

Units of Radiations SI units include: Gray (Gy) = 100 rad. Sievert (Sv) = 1000 mSv = 100 rem. Rem = 10 mSv. Becquerel (Bq): 1 d/sec-1 = 2.703 X 10-11 Ci

Principle of radiation protection Personnel protection. Risks of Radiation exposure. Radiation effect during pregnancy. Radiation effect on developing in embryo. Area Control activities. Late effect of irradiation.

I. Personnel protection 1. External Hazards: Controlled by observing proper techniques in handling radioactive materials and prevention of contamination. The general policy is to avoid all unnecessary exposure. 2. Internal Hazards: are monitored by bioassay and/or external body counting and controlled by observing proper techniques in handling radioactive materials.

1. External Hazards: Monitoring of personnel radiation exposure External Hazards: Controlled by limiting of Time Distance Shielding External Hazards are monitored by film badge or TLD.

2. Internal Hazard: Prevention of internal exposure: Always work in areas designed for handling radionuclides. Work areas should be covered with a plastic, or stainless steel tray, preferably with absorbent paper covering the tray, to control any spills and to prevent the spread of contamination. Do not eat or drink in areas where radionuclides are being used or stored. Work in a well-ventilated area. Wear protective clothing and surgical gloves while working and dispose before leaving the lab. Survey regularly. Wash hands before, eating, drinking or smoking.

Medical Versus Occupational Exposure Exposure incurred by patients as part of their own medical or dental diagnosis or treatment. Occupationally exposure for radiologist, nuclear medicine physician, physists, and technologists during a program of their biomedical research or professional work.

Dose of exposure A- Exposure of general population : Should not exceed 1 mSv (0.1 mrem) B- Exposure of radiation worker: Radiation exposure is not allowed < 18 yrs. Exposure of radiation worker 20 mSv/year. Exposure of pregnant radiation worker: No exposure allowed in first 3 months 1 mSv in subsequent 6 months

Occupional radiation exposure Dose limits* General public / year Radiation worker / year Part of the body mSv rem 1.0 0.1 20 2 Gonads, red bone-marrow and whole body. 10 1 150 15 Eye, Bone, thyroid and skin of whole body 120 12 Any single organ (excluding gonads, red bone-marrow, bone, thyroid and skin of whole body). 500 50 Hands, forearms, feet and ankles

Calculation of Maximum permissible dose and Cumulative stochastic effective dose for radiation worker Age for starting work as radiation worker age is 18 years. Cumulative effective dose for stochastic effect for radiation worker = 10 mSv x ( age - 18) . Ex: If aged 40 Yrs 10 mSv x (40- 18) = 10 * 22= 220 Maximum permissible dose for radiation worker = 20 mSv x (age - 18 ) Ex: If aged 40 Yrs 20 mSv x (40- 18) = 20 * 22= 440

II. Diagnostic Radiation exposure – Annual background: 3 mSv – Chest PA : 0.02 mSv – Screening Mammogram: 0.4 mSv. – CT » Chest: 8-18 mSv » Abdomen: 3.5- 25 mSv » Pelvis: 3.3-10 mSv

Diagnostic Radiation exposure Coakley et al. AJR:196, March 2011

Joint Commission Announces New and Revised Diagnostic Imaging Standards Changes to be implemented in two phases beginning in July 2014 These initial standards changes represent phase one, which focus on CT, NM, PET, and MRI services. Phase two, to be implemented in 2015 will focus on fluoroscopy, minimum qualifications for clinicians who perform imaging exams, and cone beam CT used in dental offices and oral-maxillary surgery practices.

Why measure cumulative dose? Medical radiation exposure can come from multiple modalities. Increase in individual stochastic risk. We already track the cumulative radiation exposure of staff, why not patients? Provides information to physician.

Risk of occupational exposure of Diagnostic Radiology Risk of cancer and leukemia: No evidence of cancer or leukemia in occupational worker with proper use of protection methods. Leukemia may follow exposure to radiation in utero if occupation female worker exposed to radiation during the first trimester. Repeated diagnostic fluoroscopy > 75 times or repeated mammography may be followed by breast cancer.

Risk of occupational exposure of Diagnostic Radiology Risk of life shortening: With modern radiation protection no significant difference from normal population. Impaired fertility or sterility: No evidence of impaired fertility or sterility within the MPD value will be produced. Induction of cataract: Higher incidence of cataract for workers working in cyclotron due to high QF for fast neutrons.

Risk of occupational exposure of Diagnostic Radiology Risk of genetic damage: Genetic risk is very small within the MPD level, there since: - Rapid repair (95% of cases) - Mostly on recessive genes. Genetic significant dose = 25rem. However, there is no threshold dose for radiation damage. (stochastic effect).

Risk of occupational exposure of Diagnostic Radiology Risks to embryo and fetus: Pregnancy should be excluded before diagnostic x-ray. Any diagnostic dose as < 0.10Gy is harmful in first 6 weeks of gestation. Chromosomal changes are seen in adults exposed > 1.2Gy of diagnostic x-ray and radiation workers exposed to average dose of 1.4rem/year.

Radiation Exposure of Diagnostic Radiology How to reduce risk of gonadal radiation: Reduce number of x-ray film per patient. Reduce time and intensity of exposure. Use the smallest possible field, proper filter, maximum Kev. Protect gonads from primary beam by shielding. Avoid fluoroscopy if possible.

Radiation Exposure of Diagnostic Radiology To reduce risk of gonadal radiation: Reduce number of x-ray film per patient. Reduce time and intensity of exposure. Use the smallest possible field, proper filter, maximum Kev. Protect gonads from primary beam by shielding. Avoid fluoroscopy if possible. Dental x-ray examination give 0.05Gy to the oral cavity, so dental x-ray especially in children should be discouraged.

III. Radiation exposure during pregnancy Exposure of female during reproductive capacity. Number of females getting exposed every week without knowing that they are pregnant. A missed period in a regularly menstruating woman should be considered due to pregnancy, until proven otherwise. Accidental exposure in pregnancy. Occupational exposures in pregnancy.

Dose limitation for Pregnant patient Lack of knowledge is responsible for great anxiety and probably unnecessary termination of pregnancies. For most patients, radiation exposure from diagnostic procedures present no measurably increased risk of prenatal death, malformation, mental impairment. Higher doses such as those from therapeutic procedures can result in significant fetal harm. Explanation or/and additional information Instructions for the lecturer/trainer

Exposure of radiation pregnant worker women Any pregnant lady working with radiation should tell immediately in writing both her supervisor and radiation safety officer. A pregnant worker should not exposed to radiation specially in the first three months (zero dose). In the remaining six months of pregnancy exposure should not exceed 0.1rem, (1mSv). Exposure of fetus to radiation in first trimester may lead to congenital abnormalities.

Irradiation of Breastfed Child Activity in milk. External radiation from the mother. Possible contamination.

IV. Radiation Effect on Developing Embryo Placental transfer distribution of activity in fetal organs not much data available I-131 as iodide or Tc-99m pertechnetate is passed through placenta . External radiation from activity present in the mothers organs and tissues radiopharmaceuticals eliminated via the kidneys

Radiation Effect on Developing Embryo Developing embryo is extremely sensitive to ionizing radiation. Stage of development, mode of radiation (single dose or fractionated) and period of implantation will affect radiation changes. Exposure of developing embryo to ionizing radiation before implantation may cause abortion, while after implantation lead to malformation, functional defect, and growth retardation or possibly to leukemia in the infant. Fetal structures particularly CNS, the eye, mesenchymal tissues, appear to be more radiosensitive than those it adults. This is probably due to more rapid growth rate and greater metabolic activity.  

How sensitive is early conceptus? Threshold dose deterministic effects 100 – 200 mSv Mental retardation 40 % /Sv Cancer and leukemia before 10 years of age 2 % /Sv lifetime Hereditary effects 1 % /Sv

Radiation Effect on Developing Embryo Radiation induced changes depend on time gestation and dose of irradiation. Dose > 2.5 – 10Gy: < 3 weeks of gestation lead to abortion. At 4 – 11 weeks of gestation lead to malformation in CNS and skeletal system. At 11 – 16 weeks of gestation produce mental retardation and micro cephalic. > 20th weeks of gestation, may result in functional defects.  

Radiation Effect on Developing Embryo Incidence of cancer in children exposed in utero Uterine dose Case / 103 person < 30 Rad 10 30 – 60 Rad 23