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Radiation Protection

Radiation Protection. Bushong Ch. 37, 39 & 40. Units of Measurement NCRP ALARA DOSE – Cumulative Annual Patients Fetus. Entrance Skin Exposure Skin erythema dose Genetically significant dose. Objectives. Objectives. Radiation units of measurements QF – Quality Factor

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Radiation Protection

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  1. Radiation Protection Bushong Ch. 37, 39 & 40

  2. Units of Measurement NCRP ALARA DOSE – Cumulative Annual Patients Fetus Entrance Skin Exposure Skin erythema dose Genetically significant dose Objectives

  3. Objectives • Radiation units of measurements • QF – Quality Factor • Cardinal Rules of Radiation Protection • Personal Dose Monitoring & Field Instruments

  4. REGULATORY AGENCIES • NCRP – National Council on Radiation Protection and Measurement • Reviews recommendation for radiation protection & safety • NRC – Nuclear Regulatory Committee • Makes LAWS & enforces regulations

  5. STANDARD VS SI UNITS • R - C/kg • Rem - Sievert • Rad - Gray

  6. measurement 100 R = 1 C/kg 1Rad = 1/100 Gray 1 Rem = .01 Sievert (Rad + QF = REM) 1 REM = 10 mSv 1 Rem = 1000mRem

  7. Pg 619

  8. Permissible Occupational Dose • Annual dose: • 5 Rem / year 50 mSv / year • Cumulative Dose • 1rem x age 10mSv X age

  9. Occupational DoseANNUAL LIMITS • WHOLE BODY = 5 REMS / 5000mRem • LENS OF THE EYE = 15 REMS • EXTREMITIES = 50 REMS

  10. PUBLIC EXPOSURE • 10 % OF OCCUPATIONAL • (MUST BE MONITORED IF ABOVE 10%) • NON MEDICAL EXPOSURE • .5 RAD OR 500 MRAD • UNDER AGE 18 AND STUDENT • .1 rem 1 mSv • Pg 98 RTA BOOK

  11. OCCUPATIONAL EXPOSURES • 5 REMS / YEAR BUT NOT TO EXCEED 1.25 REM/QUARTER • OLD “MPD 5(Age – 18)” • Technologist essentially receive all exposure during fluoroscopy exams

  12. Two types of exposures • Radiation worker • Patient

  13. Effects of radiation in utero are time and dose related • Effects include: • Prenatal death, neonatal death, congenital abnormalities, malignancy inductions, general impairments of growth, genetic effects, and mental retardation.

  14. Irradiation in Utero • The first trimester is the most radiosensitive period. After the 2 weeks of fertilization • The first 2 weeks of pregnancy may be of least concern because the response is all or nothing

  15. After 200 rads delivered at various times

  16. Declared Pregnant Worker • Must declare pregnancy – 2 badges provided • 1 worn at collar (Mother’s exposure) • 1 worn inside apron at waist level Under 5 rad – negligible risk Risk increases above 15 rad Recommend abortion (spontaneous) 25 rad (“Baby exposure” approx 1/1000 of ESE)

  17. Pregnancy & Embryo Mother – occupational worker (5 rem) • Baby – (500 mRem) • .5 rem/ year .05 rem/month • 5 mSv .5 mSv / month

  18. Pregnant patient • ALWAYS ASK LMP before exposure made • “10-day Rule” No longer used • “Grace period” of implantation • What is the State Law for gonadal shielding?

  19. Pregnant Patients • Should never knowingly expose a pregnant patient unless a documented decision to so has been made • If you must expose; use precise collimation & protective shields. Use a high kVp technique and only the minimal projections

  20. Unsuspected pregnancy • Always screen female patients for last LMP • don’t assume ages (patient privacy) • If unsure obtain a blood test or reschedule exam if possible

  21. PREGNANT PATIENTS • Ascertain LMP - if fetus is exposed • Medical Physicist will need information: • Which x-ray machine used (mr/mas) • # Of projections (including repeats) • Technique for each exposure • SID • Patient measurement at C/R • Fluoro time & technique used • Physicist will calculate fetal dose

  22. Patient dose • Is reported in Entrance Skin Exposure (ESE)

  23. Over Radiation to SkinToo much time under beam Skin burns from 30 min of beam on time

  24. SED • SKIN ERYTHEMA DOSE • LINEAR – NONTHRESHOLD • DEPENDANT ON • DOSE RECEIVED • PERIOD OF TIME OVER IT WAS RECEIVED • AREA OF IRRADIATED TISSUE • SENSITIVITY

  25. Protective shielding • Gonads • Breasts • Thyroid • Lenses of the eyes • Long bones (bone marrow)

  26. PEDIATRIC EXPOSURE • More sensitive to radiation than adults • Limit beam time • May remove grid (reduce exposure) • Collimation & shielding !!!!!!!!!!!!!!! • Gender differences • Immobilization

  27. GSD • GENETICALY SIGNIFICANT DOSE • Takes all of the population into account • Annual AVERAGE gonadal dose to population of childbearing age • 0. 20 mSv or 20 millirem

  28. REDUCING REPEATS • TECHNIQUE CHARTS • CAREFUL REVIEW OF TECHNICAL FACTORS • REFER TO TECHNIQUE BOOK AND • ASK WHEN YOU ARE NOT SURE!

  29. CARDINAL RULESOF RADIATION PROTECTION • TIME • DISTANCE • SHIELDING

  30. Filtration REDUCES PATIENT EXPOSURES • REMOVES LOW ENERGY PHOTONS

  31. In terms of patient dose…whatis the best combination to reduce exposure to your patent? • Beam filtration More or Less? • mAs High or Low? • kVp High or Low? • Grid or Not to Grid?

  32. In terms of patient dose…whatis the best combination to reduce exposure to your patent? • Beam filtration More or Less? • mAs High or Low? • kVp High or Low?

  33. SHEILDING TECHNOLOGIST . 25 mm LEAD • LEAD APRON, GLOVES • THYROID SHIELD, GLASSES PATIENT – GONAD SHEILDING . 5 mm LEAD

  34. GONAD SHIELDING • MUST BE . 5 MM OF LEAD • MUST BE USED WHEN GONADS WILL LIE WITHING 5 CM OF THE COLLIMATED AREA (RHB) • KUB. Lumbar Spine Pelvis • male vs female shielding

  35. Lead protective aprons • 0.5 mm lead equivalent. Provides approximately 90% attenuation at 75 kVp • 1.0 mm lead equivalent is available but not practical because of the weight and potential back problems

  36. TYPES OF SHEILDING • FLAT /CONTACT • SHAPED • SHADOW

  37. Which shielding type is best for Males? Females? • Males = Shaped • Females = Flat contact

  38. Breast ShieldShadow shields

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