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1 حفاظت در برابر پرتو دانش محافظت پرتونگاران و مردم در برابر پرتوهای غیر لازم.

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Presentation on theme: "1 حفاظت در برابر پرتو دانش محافظت پرتونگاران و مردم در برابر پرتوهای غیر لازم."— Presentation transcript:

1 1 حفاظت در برابر پرتو دانش محافظت پرتونگاران و مردم در برابر پرتوهای غیر لازم

2 2 پرتوهای درون بدن عمدتاٌ K-40 منشاء خاک و مصالح ساختمانی 25 mr پرتوهای طبیعی یا زمینه ای پرتوهای کیهانی عمدتاٌ نوترون منشاء فضای بین ستارگان mr50 پرتوهای زمینی(وهوا) گاز رادون منشاء هوا پس از تاثیر رادیم mr50 پرتوهای پزشکی رونتگن تشخیصی برای 50 درصد افراد mr75 پرتوهای شغلی 1 mr آزمایشات هسته ای و منابع دیگر 5 mr جمع: 200 mr

3 3 روش های کاهش تشعشع به افراد آهنگ تشعشع (dose rate) کاهش یابد. 1- عامل زمانی 2- عامل فاصله اسکتر در یک متری تیوب 0.1 درصد تشعشع اولیه(لذا حداقل رعایت دو متر فاصله)

4 4 روش های کاهش تشعشع به افراد 3- حفاظ کردن 4- کنترل آلودگی پوشش سربی و دیوار سربی 1)workload 2) radiation exposure 3) use factor 4) Occupancy factor 5) distance to tube 5- تکنیک مناسب ضخامت بستگی دارد به:

5 5 workload

6 قانون عکس مجذور فاصله

7 پرتوهای اولیه پرتوهای ثانویه پرتوهای پراکندگی پرتوهای نشتی

8 8 حدود مجاز حد مجاز اکسپوژر برای مناطق کنترل شده 100 mSv/wk حد مجاز اکسپوژر برای مناطق کنترل نشده 10 mSv/wk

9 A controlled area any area in which specific protective measures is obtained for: (a) controlling normal exposures during normal working conditions (b) preventing or limiting the extent of potential exposures In a radiology facility, all X-ray rooms shall be controlled areas In a radiology facility, all X-ray rooms shall be controlled areas Supervised areas should include parts of the facility where mobile x-ray units are used, and all other parts other than public areas. Controlled and supervised area

10 10 Medical Exposure (The exposure of persons as part of their diagnostic or treatment) Occupational Exposure (exposure incurred at work, and practically as a result of work) Public Exposure (including all other exposures) Three types of exposure

11 11 –Exposure of persons as part of their diagnostic or treatment –Exposures incurred knowingly and willingly by individuals such as family and close friends helping either in hospital or at home in the support and comfort of patients –Exposures incurred by volunteers as part of a program of biomedical research Medical exposure

12 12 Justification Optimization The use of doses limits is NOT APPLICABLE Dose constraints and guidance (or reference) levels ARE RECOMMENDED Framework of radiological protection for medical exposure

13 13 The justification of a practice A review of benefits and disadvantages of the possible options The use of radiation in medicine is accepted as doing more good than harm E.g.: choosing between the use of X-rays or ultrasound Justification is made on the basis of experience, professional judgement, and common sense

14 14 The optimization of protection Optimization is usually applied at two levels : 1) The design and construction of equipment and installations 2) Day to day radiological practice (procedures) Reducing the patient dose may reduce the quantity as well as the quality of the information The optimization means that doses should be “as low as reasonably achievable (ALARA)

15 15 A value of dose, dose rate or activity selected by professional bodies to indicate a level above which there should be a review by medical practitioners Guidance level for medical exposure (as defined by the BSS)

16 16 for medical research purposes for individuals helping in care of patients, and visitors 5 mSv during the period of the examination 1 mSv for children visiting 1100 MBq activity in patients discharged from hospitals for Iodine 131 Dose constraints

17 Guidance levels for diagnostic radiography (typical adult patient) 10 Abdomen, IVU and cholecystography AP 40Lumbar spineLSJ 30Lumbar spineLAT 10Lumbar spineAP Entrance surface dose per radiograph (mGy) Examination

18 1.5Chest LAT 0.4Chest PA 10Hip jointAP 10Pelvis AP Entrance surface dose per radiograph (mGy) Examination Guidance levels for diagnostic radiography (typical adult patient)

19 Dose guidance levels in CT (typical adult patient) (a) Derived from measurements on the axis of rotation in water equivalent phantoms, 15 cm in length and 16 cm (head) and 30 cm (lumbar spine and abdomen) in diameter. 25 Abdomen 35Lumbar spine 50Head Multiple scan average dose (mGy) (a) Examination

20 Dose rate guidance levels for fluoroscopy (typical adult patient) (a) In air with backscatter (b) For fluoroscopes that have an optional 'high level' operational mode, such as those frequently used in interventional radiology 100High Level (b) 25Normal Entrance surface dose rate (mGy/min) (a) Operation Mode

21 Typical effective doses from diagnostic medical exposures From: Referral Criteria For Imaging. CE, 2000.

22 Typical effective doses from diagnostic medical exposures

23 From: Referral Criteria For Imaging. CE, Typical effective doses from diagnostic medical exposures

24 Approximate fetal doses from conventional x-ray examinations data from the UK 1998

25 Approximate fetal doses from fluoroscopic and computed tomography procedures data from the U.K. 1998

26 Radiation-Induced Malformations Malformations have a threshold of mGy or higher and are typically associated with central nervous system problems Fetal doses of 100 mGy are not reached even with 3 pelvic CT scans or 20 x-ray examinations These levels can be reached with fluoroscopically guided interventional procedures of the pelvis and with radiotherapy

27 Termination of pregnancy Termination of pregnancy at fetal doses of less than 100 mGy is NOT justified based upon radiation risk At fetal doses in excess of 100 mGy, there can be fetal damage High fetal doses ( mGy) during late pregnancy are not likely to result in malformations In these cases decisions should be based upon individual circumstances

28 28 All exposures of workers incurred in the course of their work Occupational exposure definition

29

30 30 Responsibilities (BSS I.10) Workers shall:  follow any applicable rules for protection  use properly the monitoring devices and the protective equipment and clothing provided  co-operate with the licensee with respect to protection

31 Personal protective equipment Workers should be provided with suitable and adequate personal protective equipment Protective equipment includes lead aprons, thyroid protectors, protective eye-wear and gloves.

32 Personal protective equipment Additional protective devices should be available in fluoroscopy and interventional radiology rooms which include:  Protective lead curtains mounted on the patient table. SCREEN AND GOGLES

33 Individual monitoring Individual external doses should be determined by using individual monitoring devices: –Thermoluminescent –Film badges –Electronic dosimeters Worn at breast level, between the shoulders and the waist The exchange of dosimeters and report receipt should not exceed three months

34 Personal dosimetry

35 Different types of personal dosemeters… ý film ý termoluminescence dosemeters (TLD) ý ”electronic” dosemeters

36 Film badge plastic filter metal filtersopen windows open window detects beta, gamma, X-ray

37 TLDs whole body extremity


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