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Radiation Shielding Information And Guidance PowerPoint Presentation

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Description : Check out this medical PowerPoint presentation titled "Radiation Shielding Information and Guidance” by Don Parry, CHP.

This medical PowerPoint presentation is about radiation shielding, the use of materials and structures to protect people and equipment from the harmful effects of ionizing radiation. This can be achieved through various means, including absorption, reflection, and scattering of the radiation. Some common materials used for radiation shielding include concrete, lead, steel, and water.

Radiation shielding is important in many industries, including nuclear power, medical imaging, and space exploration. In nuclear power plants, shielding is used to protect workers from exposure to radioactive materials, while in medical imaging, it is used to protect patients from the radiation used to produce images. In space exploration, shielding is used to protect astronauts from the high levels of radiation found in space.

There are different types of radiation, including alpha, beta, gamma, and neutron radiation, and each type requires a specific type of shielding. For example, alpha particles can be stopped by a sheet of paper or a few centimeters of air, while gamma rays require thicker shields made of dense materials like lead or concrete.

The effectiveness of radiation shielding depends on various factors, such as the type and energy of the radiation, the thickness and composition of the shield, and the distance between the radiation source and the shield. Shielding can also be designed to minimize exposure to radiation by using different configurations or materials to achieve the desired level of protection.

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Published on : Jun 20, 2023 | Views : 1123 | Downloads : 1

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Slide 1-

June 21, 2023 1 Radiation Shielding Information and Guidance Don Parry, CHP District Health Physicist Michigan Department of Consumer & Industry Services Radiation Safety Section dparry@michigan.gov
Slide 2-

June 21, 2023 Radiation Safety Section 2 Regulations and Standards Regarding Plan Reviews Michigan’s first rules were published in February of 1958; Shielding requirements were listed in an appendix based on NBS Handbook 76 Rules were modified in 1965 and more clearly indicated that: Shielding shall be approved by the Michigan Department of Health Rule 331(2) of current Ionizing Radiation Rules (Promulgated in 1975) states that shielding is subject to design approval by the department Plan reviews have been done routinely by the State Radiation Control Program since 1958
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June 21, 2023 Radiation Safety Section 3 NCRP and SSRCR Recommendations Page 2 of NCRP report 49 states that it is highly desirable that final shielding plans be reviewed by the pertinent federal, state or local agency before construction is begun The Suggested State Regulations for the Control of Radiation published by the CRCPD also require that plans be submitted to the state for approval prior to construction
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June 21, 2023 Radiation Safety Section 4 Current Basis for Shielding Design Criteria Current NCRP reports including NCRP 49, 51, 79 and 116 New shielding reports will be reviewed when published Current criteria still uses NCRP 49’s leakage model and occupancy factors and NCRP 116’s dose limits
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June 21, 2023 Radiation Safety Section 5 NCRP 116 (page 47) the NCRP reaffirms its previous recommendations (NCRP, 1984b) that whenever the potential exists to exceed 25 percent of the annual effective dose limit as a result of irradiation attributable to a single site, the site operator should ensure that the annual exposure of the maximally exposed individual, from all man made exposures (excepting that individual’s medical exposure), does not exceed 1 mSv on a continuing basis. Alternatively, if such an assessment is not conducted, no single source or set of sources under one control should result in an individual being exposed to more than 0.25 mSv annually.
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June 21, 2023 Radiation Safety Section 6 Rule 201(2) In addition to occupational and general public dose limits, Rule 201(2) also requires that doses to uncontrolled areas be as as far below the limits as reasonably practicable.
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June 21, 2023 Radiation Safety Section 7 What changed? Public dose limit went down by a factor of five, and yet; Around 1998 we started finding more and more new facilities that failed to submit shielding plans and failed to shield secondary barriers.
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June 21, 2023 Radiation Safety Section 8 Example 1 of inadequate shielding for new diagnostic x-ray room Designer assumed: -100 mA-min/wk -Ignored leakage -Specified wood door and drywall No plan submitted -Facility had to add shielding after construction These walls and this door were not leaded
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June 21, 2023 Radiation Safety Section 9 Designer assumed: P = 0.2 mSv/wk T = 0.25 for hall - Used attenuation of the bucky Specified drywall for one wall and 1/16th behind bucky -Plan submitted and changes made prior to construction This wall not shielded Example 2 of inadequate shielding for new diagnostic x-ray room calculations were claimed to be based on AAPM TG-9, 1989, NCRP 116 and updated NCRP 49
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June 21, 2023 Radiation Safety Section 10 Example 3 of inadequate shielding for mobile CT scanner No shielding plan submitted No shielding information available at time of survey Maximum exposure rate at 4 feet above ground at surface of vehicle was 380 mR/hr, most areas were ~ 2 mR/hr Rate several yards away ~ 10 mR/hr
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June 21, 2023 Radiation Safety Section 11 Example 3 of inadequate shielding for mobile CT scanner ~ 10 mR/hr ~2 mR/hr ~380 mR/hr
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June 21, 2023 Radiation Safety Section 12 Policy on Submission of Plan Reviews and Delay of Equipment Registration All medical facilities should submit shielding plans for review for any new construction or shielding modifications that involve radiation producing machines Failure to do so can can cause expensive modifications after the project is completed Equipment that requires a Certificate of Need (CON) will not be registered until plans have been reviewed and approved by the Radiation Safety Section
Slide 13-

June 21, 2023 Radiation Safety Section 13 Actions taken to communicate need to submit shielding plans Letters sent with registration applications starting April 2001 indicate the need to submit shielding plans Certificate of need letters to CON applicants state that plans need to be submitted to the Radiation Safety Section (RSS) Letters from the Health Facilities Evaluation Section state that radiation shielding plans need to be submitted to RSS Additional letters are sent by RSS for all equipment requiring a CON and now include the statement: Review and approval of the proposed shielding should be obtained from RSS prior to registration and prior to placing the equipment into use. Copies of the CON letters are now sent to the facility’s RPS in addition to the CON contact
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June 21, 2023 Radiation Safety Section 14 Communication of Plan Review Requirements CON letters state The applicant is required to contact the Michigan Department of Consumer and Industry Services, Bureau of Health Systems, Division of Health Facilities and Services at (517) 241-1989 to obtain radiation shielding approval when constructing new radiation facilities or installing new or replacement x-ray equipment ........" Engineering Plan Review Section letter states Provisions for radiation shielding protection of x-ray and gamma ray installations are subject to review by the Division of Health Facilities and Services, Radiation Safety Section.."
Slide 15-

June 21, 2023 Radiation Safety Section 15 Additional Shielding Information Form BHS/HFS 852 – Information Required for a Radiation Shielding Plan Review Available on Web site at: www.michigan.gov/bhs (click on Mammography and X-ray Machines – Radiation Shielding Guidance) Web Site includes guidance on shielding: Radiographic or RF rooms Mammography Rooms Computed Tomography Rooms Linear Accelerator Vaults Additional Guidance
Slide 16-

June 21, 2023 Radiation Safety Section 16 Table of Recommended Shielding(Rad /Fluoro Rooms)
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June 21, 2023 Radiation Safety Section 17 Recommended Shielding(CT Rooms) Computed tomography rooms typically have high workloads and high kilovoltage technique settings. As a result, at least 1/16 inch lead shielding or equivalent is required for the walls, doors, floors, ceilings, and operator's barrier. CT rooms with high workloads and with fully occupied uncontrolled space directly adjacent to the scanner may need shielding that is thicker than 1/16 inch lead to meet the 25 millirem per year dose constraint for uncontrolled areas. Facilities with CT x-ray equipment may also want to enlist the services of a qualified medical physicist for shielding advice.
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June 21, 2023 Radiation Safety Section 18 Guidance on Concrete Floor Thickness Floors Need to use minimum thickness of concrete floor in shielding calculations Need to know density of concrete (147 lbs/ft3 standard)
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June 21, 2023 Radiation Safety Section 19 Radiation Shielding Implications of CT Scatter Exposure to the Floor (Langer and Gray)(Health Physics Vol 75, Number 2, August 1998 ) “Care may be needed to assure adequate shielding for floor areas near CT scanners specializing in either head or body work. Also, while increased throughput with helical scanners is currently x-ray tube limited, shielding plans should allow for enhanced heat capacity (and generator throughput) in future generation scanners.”
Slide 20-

June 21, 2023 Radiation Safety Section 20 CT Shielding Methodologies AAPM Report number 39 Uses isodose contour lines and one set of coefficients for the Archer Equation to determine transmission curve BIR/IPEM(British Institute of Radiology) uses similar method with a slightly different set of coefficients NCRP 49 re-write Uses scatter fraction determined by CTDI; 9x10-5 for head and 3x10-4 for body Uses slightly different set of coefficients
Slide 21-

June 21, 2023 Radiation Safety Section 21 CT Shielding Coefficients for the Archer Equation
Slide 22-

June 21, 2023 Radiation Safety Section 22 Operator Booth Shielding Guidance(Suggested State Regulations) The lead glass viewing window should have an area of at least 1 square foot At least 1 square foot of the viewing window should be centered no less than 2 feet from the open edge of the booth and be centered 5 feet from the floor. The operator should be allotted not less than 7.5 square feet of unobstructed floor space in the booth
Slide 23-

June 21, 2023 Radiation Safety Section 23 Radiation Shielding Plan ReviewsSummary Plans should be submitted prior to construction Rule 331(2) of the Ionizing Radiation Rules states that shielding is subject to design approval by the department Most medical x-ray rooms should normally be provided with 1/8 inch thick lead for primary barriers (including floors) and 1/16 inch thick lead for secondary barriers (including doors) Construction of an x-ray room without an approved plan may cause shielding modifications to be done after the room is constructed
Slide 24-

June 21, 2023 Radiation Safety Section 24 GLAAPM Shielding Statement and Various Shielding Assumptions The Qualified Medical Physicist Design Dose Constraints Models for Tube Housing Leakage Workload Assumptions Occupancy Factors Use Factors Shielding Credit for Imaging Hardware
Slide 25-

June 21, 2023 Radiation Safety Section 25 The Qualified Medical Physicist Currently only ~20 % of the submitted plans involve a AAPM QMP Others include HPs, CHPs, Architects, Engineers, RSOs, Physicians, X-ray Equipment installers Current NCRP and Current draft do not list QMP requirements similar to GLAAPM
Slide 26-

June 21, 2023 Radiation Safety Section 26 Design Dose Constraints NCRP 116 - if such an assessment is not conducted, no single source or set of sources under one control should result in an individual being exposed to more than 0.25 mSv annually. GLAAPM - If such an assessment is not conducted… no single source(of radiation)…should result in an individual being exposed to more than 0.25 mSv annually. The GLAAPM declares that if shielding designs are performed by a Qualified Radiation Physicist they are ensuring the exposure of a maximally exposed individual from a single source of radiation, will not be greater than 1 mSv annually and therefore the lower dose limit is not required.
Slide 27-

June 21, 2023 Radiation Safety Section 27 Tube Housing Leakage 150 kVp is the LEAST conservative leakage kVp to assume Many MDs and DCs use lower rated tube housings Amount of leakage calculated is a strong function of assumed kVp spectrum
Slide 28-

June 21, 2023 Radiation Safety Section 28 Leakage Technique Factors
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June 21, 2023 Radiation Safety Section 29 Workload Assumptions NCRP 49 philosophy was to assume a fixed kVp and busy workload for design purposes (e.g. 100kVp,1000 mAmin/wk) The draft of the NCRP re-write of Report 49 uses mean workloads based on survey of hospital facilities Since workloads change over time (and have increased with digital) we advocate using conservative workload assumptions
Slide 30-

June 21, 2023 Radiation Safety Section 30 Workload Assumptions From Simpkin, Med. Phys. 23(4), April 1996 Given the broad distributions of the workload per patient, a reasonable concern arises as to the use of the mean normalized workload per patient for estimating room workloads…. A more conservative approach would be to assume an upper percentile workload as the per patient value, since this would only be exceeded in a minority of cases…. The 90th percentile workload would be especially conservative. From the PEMNET data, the 90th percentile workload is 2 to 3 times the mean.
Slide 31-

June 21, 2023 Radiation Safety Section 31 Workload AssumptionsUse of kVp spectrums The use of kVp distributions are advocated based on the premise that “The relative distribution of the workload over kVps is set by the radiographic contrast required for imaging” However, we find kVp varies considerably by facility, even for the same sized patient
Slide 32-

June 21, 2023 Radiation Safety Section 32 Occupancy factors The occupancy factor for radiation workers should be unity (1) throughout controlled areas (NCRP49 page 6) The occupancy factor in generally accessible areas for non radiation workers should not be less than the ratio of the uncontrolled design dose limit to the controlled area design dose limit
Slide 33-

June 21, 2023 Radiation Safety Section 33 Radiation Shielding for Diagnostic X-rays – (Copyright 2000, The British Institute of Radiology, ISBN 0-905749-44-8) IRR99 explicitly states that areas in which exposure can be greater than 6mSv per year should be controlled. Any design criteria and associated assumptions on occupancy must reflect this fact. Therefore consequent to the design criterion of 0.3 mSv per annum must be the adoption of 5% as the lowest occupancy factor. Use of a lower occupancy factor with a dose constraint of 0.3 mSv implies that the area outside of the room would have to be designated as a controlled area.
Slide 34-

June 21, 2023 Radiation Safety Section 34 Use factors NCRP 49 assumes walls are ¼ and floor is 1 and ceiling 0. New draft uses new model (NT/Pd2) which “hardwires” in uses factors for walls that sum to unity We believe barrier use factor should be selected as the reasonable maximum percentage of the time that the barrier might intercept primary radiation.
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June 21, 2023 Radiation Safety Section 35 Shielding credit for image receptor Should not be counted unless; The primary beam is permanently and positively restricted to the image receptor The image receptor is designed to fully intercept the primary beam regardless of collimator settings, image receptor size, SID, user controlled alignment, alignment overrides, etc. X-ray room will not be used in the future with conventional general purpose x-ray equipment unless shielding is redesigned
Slide 36-

June 21, 2023 Radiation Safety Section 36 Conclusion Submit plans for approval prior to construction We recommend utilizing the shielding guidance on our web site at: www.michigan.gov/bhs (click on Mammography and X-ray Machines – Radiation Shielding Guidance) The new NCRP shielding report will be reviewed once the report is made final and we may revise some policies and guidance after the review
Slide 37-

June 21, 2023 Radiation Safety Section 37 Contact Information Headquarters:Radiation Safety SectionMichigan Department of Consumer & Industry ServicesP.O. Box 30664Lansing, Michigan 48909 Phone: (517) 241-1989Fax: (517) 241-1981 Visitor/delivery address:5th Floor, G. Mennen Williams Building525 W. Ottawa StreetLansing, Michigan 48933 District Office:Our district office, formerly in Pontiac, has moved to: Radiation Safety SectionMichigan Department of Consumer & Industry Services38600 Van Dyke, Suite 375Sterling Heights, Michigan 48312 Phone: (586) 446-0200Fax: (586) 446-0227