Radiation Protection for Patients and Personnel - PDF

Chapter 10: Radiation Protection Procedures for Patients and Personnel Objectives Differentiate between the various advisory groups and regulatory agencies involved in developing radiation protection standards Explain the concept of d...

Chapter 10: Radiation Protection Procedures for Patients and Personnel Objectives Differentiate between the various advisory groups and regulatory agencies involved in developing radiation protection standards Explain the concept of dose limits related to the use of radiation Describe the ALARA concept Explain the basic principles of reducing exposure to radiation Describe techniques used to minimize radiation exposure to patients and personnel Discuss the precautions that should be taken to minimize potential fetal exposures  Advisory vs. Regulatory Groups Several agencies Advisory groups help Regulatory agencies are involved in ESTABLISH radiation ENFORCE those protection standards standards the development of standards and ICRP regulations for NCRP NRC radiation NAS-BIER FDA protection UNSCEAR  Advisory Groups International National Committee on Commission on Radiation Protection Radiological Protection and Measurements (ICRP) (NCRP)* Formed in 1929 Formed in 1928 Chartered by Congress in 1964 Provides perspectives on Non-profit organization that radiologic health issues. collects, analyzes, develops, and Non-governmental disseminates information in this organization that sets publics interest acceptable limits of MAKES RECOMMENDATIONS about exposure radiation protection, radiation Created the NCRP -> measurements, quantities, and units. Effective Dose Limit recommendations (Table 10-1)  Advisory Groups National Academy of Sciences United Nations Scientific Advisory Committee on the Committee on the Effects of Biological Effects of Ionizing Atomic Radiation (UNSCEAR) Radiation (NAS-BIER) Committee on the Biological Formed in 1955 Effects of lonizing Radiation To undertake broad assessments of publishes a series of reports the sources of exposure to ionizing informing the US government on radiation and the effects on human the effects of ionizing radiation. health and the environment.  Regulatory Groups Nuclear Regulatory U.S. Food and Commission (NCR) Drug Administration Authority for special nuclear materials and by-products Regulates(FDA) Federal Agency radiopharmaceuticals Regulations are recognized Regulates performance as law in US. and radiation safety Most critical regulation= requirements of whole body exposure commercial x-ray regulation equipment limits exposure to 500 mSv/year to any organ, or 50 mSv/year to the whole body.  State Regulatory Agency Responsible for protecting both the public and occupationally exposed individuals from the effects of ionizing radiation Created in 1980 and assumed the responsibilities of the Arizona Atomic Energy Commission. 2018 the Arizona Department of Health Services (ADHS) assumed the authority, powers, duties and responsibilities of ARRA Risk Groups Radiation workers ⚬ Occupational Risk ￭ Significant Exposure potential during course of employment ⚬ Occasional Risk ￭ Duties occasionally bring them into areas where exposure may occur. General Public Occupational Dose Limits Exposure limits pertinent to the protection of the radiation worker Effective dose limits ⚬ Annual- 50 mSv ⚬ Cumulative- 10 mSv x Age Dose equivalent annual limits for tissue/organs ⚬ Eye- 150 mSv ⚬ Skin, hands, feet- 500 mSv  General Public Dose Limits Infrequent Exposure ⚬ One-tenth of effective dose limit for radiation workers ￭ 5 mSv Continuous exposure ⚬ One-fiftieth of effective dose limit for radiation worker ￭ 1 mSv  ALARA As Low As Reasonably Achievable Radiologic personnel responsible for minimizing radiation exposure to: ⚬ Patients ⚬ Occupational staff Achieved through thoughtful approach and application of radiation protection practices  Protection of Personnel Should not hold!!! ⚬ absolute last resort Instead, the technologist should use: ⚬ immobilizers ⚬ positioning tools ⚬ family members Scatter radiation leads to increase in occupational exposure cardinals rules of radiation protection Time Distance Shielding  time X-rays= very short exposure time Fluoro= several minutes- an hour ⚬ Radiation dose is directly related to time ⚬ Have all tools present- thorough planning ⚬ Work swiftly and efficiently  distance Dose follows the Inverse Square Law Doubling distance, dose rate falls to ¼  shielding Used when neither time or distance is effective Fixed Structural Barriers ⚬ Lead and Concrete most common materials Additional lead devices (Lead Equivalent): ⚬ Lead aprons/ thyroid shield ⚬ Lead gloves ⚬ Lead glasses ￭ 0.25-1.0 mm Pb Eq  protective barriers Primary barrier ⚬ may be struck by primary beam (image intensifier) Secondary barrier ⚬ may not be struck by primary beam, only scatter and leakage Room shielding designed with input from radiologic medical physicist  Protecting the Patient Professional Beam limitation radiography involves Technique selection a balance between Filtration Grids optimizing image Gonadal shielding quality and Image receptors minimizing patient Repeat radiographs Projection dose Patient exposure estimates Equipment beam limitation Field size should never be larger than the IR Should always be restricted to the area of clinical interest Collimation: ⚬ reduces patient dose ⚬ improves image quality ⚬ should be seen on all 4 sides  Technique Increasing Selection distance for routine BEST method to minimize procedures 44"-48" SID recommended patient dose Increased SID reduces High kVp, low mAs patient skin exposure ⚬ minimizes time Improves image quality ⚬ minimizes possibility of places more anatomy on a repeats due to motion digital receptor  Filtration Removes low energy photons ⚬ Absorbed by the filters Aluminum is most common filter material ⚬ Copper gaining popularity ⚬ 2.5-mm Al Eq required when operating above 70 kVp Increased filtration requires increased technique ⚬ Needed to maintain exposure to IR and image quality ⚬ Patient dose still reduced as skin exposure is reduced  Grids Improved image quality but at the expense of patient exposure Use lower grid ratio to effectively remove scatter, without jeopardizing image quality. ALARA compliant  Gonadal shielding Used when the gonads lie within 4-5 cm of primary beam. ⚬ Used in conjunction with collimation Children and adults of childbearing age Three types: ⚬ Flat contact ⚬ Shaped contact ⚬ Shadow shield Image receptor Image receptor speed ⚬ Fastest possible image receptor system will minimize patient dose ⚬ Response or speed influenced by sensitivity of materials that make up IR Department system speed determined by department leaders with radiologists’ input ⚬ Balance between exposure and image quality * Some of this is going away as DR becomes more prevalent projection Part specific ⚬ Lens of eye greater exposure during AP projections opposed to PA projections. ⚬ PA chest lowers exposure to breast tissue ⚬ Contrast filled bladder shields bladder on AP projection REPEATS! Repeat images occasionally required by all radiographers ⚬ Inadequate exposure ⚬ Patient motion/poor patient instructions ⚬ Equipment malfunction/improper post-processing ⚬ Poor positioning Must be minimized to reduce patient dose Communication with patient a critical element to reduce repeat images  exposure estimates Should be developed and available for routine procedures on average patients (See Chapter 14)  equipment Should be surveyed periodically by medical physicist Schedule PMIs regularly Correct equipment issues before reusing equipment  Exposure & Pregnancy Fetus during early stages of pregnancy is especially sensitive to radiation ⚬ BEIR V Report: ￭ 8-15 weeks post conception most sensitive ⚬ NCRP recommends dose limit for the embryo not to exceed 5 mSv once the pregnancy becomes known. ⚬ Monthly= 0.5 mSv Declaration of pregnancy is voluntary ⚬ Must be in writing ⚬ Must be dated ⚬ Must include estimated date of conception  Current Recommendations ⚬ Do not support assignment of pregnant workers to areas of lower ALARA AND exposure ⚬ Violates application of ALARA for PREGNANCY other workers Choices regarding occupational exposure and pregnancy require informed decision-making  10 Day Rule Women of child bearing age: protection of a possible fetus when radiating diaphragm to knees. ⚬ Asks pregnancy status, last menstrual cycle. which means that whenever possible, one should confine the radiological examination of the lower abdomen and pelvis to the 10-day interval following the onset of menstruation NOW OBSOLETE pregnant patients Current recommendation: ⚬ Ordering physician must consider patient’s entire clinical status, including possibility of pregnancy and rescheduling ⚬ Medical physicist should be consulted if exposure is necessary ⚬ Reschedule if possible ⚬ Optional imaging studies ￭ Ultrasound ￭ MRI  References Carlton, R. (2017) Principles of radiographic imaging: An art and a science. (6th Ed.). Cengage.