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Rad Protection & Radiobiology review

Rad Protection & Radiobiology review. 244 09. STAT 8 & 9 Protecting Patients & Personnel. COMMUNICATE COLLIMATE SHIELD. Ch 1 – pg 1 RHB SYLLABUS 5% population have fluoro exams 53% GI tract (1996 ) 120 sec fluoro ~= ese 5 – 15 rads Comp to ABD ~= ese 100- 500 mrads

yoshio-zamora
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Rad Protection & Radiobiology review

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  1. Rad Protection & Radiobiologyreview 244 09

  2. STAT 8 & 9Protecting Patients & Personnel • COMMUNICATE • COLLIMATE • SHIELD

  3. Ch 1 – pg 1 RHB SYLLABUS • 5% population have fluoro exams • 53% GI tract (1996 ) • 120 sec fluoro ~= ese 5 – 15 rads • Comp to ABD ~= ese 100- 500 mrads • Fluoro used for dynamic studies • USING FLUORO TO POSTION PATIENTS PRIOR TO TAKING FILM IS PROHIBITED • Must have fluoro permit or Supervisor & Operators Certificate from state

  4. PATIENT PROTECTION • LIMIT SIZE OF BEAM • BEAM ON TIME • DISTANCE OF SOURCE TO SKIN • PBL • FILTRATION (2.5 mm Al eq) @ 70 • SHEILDING • SCREEN/FILM COMBO -OVERHEADS

  5. more 6 things that will reduce patient exposure: • Collimating to the area of interest • Using last frame hold • Keeping the pt. / detector distance to a minimum • Using high kv low mA • Pulsed Fluoro with low frame rates • Using the largest II mode

  6. MONITORED weekly (QC) RECORDED Daily DURING FLUORO EXAMS) Fluoroscopy – OUTPUTcheck with a LUCITE Phantom or Water Containerfor consistent exposure output

  7. DOSE REGULATIONS • BEFORE 1974 - AT TABLETOP • 5R/MIN (WITHOUT AEC) • 5R/MIN (WITHOUT AEC) – BOOST MODE • After 1974 with AEC • 10 R/MIN • 20R/MIN BOOST(Stat p198)

  8. Exposure Bushong – ch 39 DAP • Must not exceed 2.1 R/ma/min • 2.2 R/min in RHB • DAP – dose area product • Takes in account the volume of tissue irradiated

  9. CINE DOSE • CINE - 2mR per frame (30 OR 60f/sec) • 400 mr per “look” • WHAT WOULD BE THE PATIENT’S DOSE FOR A 5 MIN PROCEDURE • AT 60 F/SEC?

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

  11. OCCUPATIONAL EXPOSURES • 5 REMS / YEAR BUT NOT TO EXCEED 1.25 REM/QUARTER • OLD “MPD 5(Age – 18)”

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

  13. DOSE LIMIT (DL) • NCRP ? NCR ? (Stat Book) • BEIR ? • DL’S imply that if received annually, risk of death would be less than 1/10,000 • Based on Linear Non-Threshold • DL – Dose Limits • Occupation Exposure (rems)

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

  15. REGULATORY AGENCIES p143/5th BEIR - Biological Effect of Ionizing Radiation UNSCEAR – United Nations Scientific Committee on the Effects of Atomic Radiation

  16. ROOM SHIELDING • PRIMARY SHIELD – • PRIMARY BEAM DIRECTED AT WALL • 1/16 LEAD - 7 FEET HIGH

  17. ROOM SHIELDING • SECONDARY – NO PRIMARY BEAM • 1/32 LEAD • CONTROL BOOTH (SECONDARY) • BEAM SCATTERS 2X BEFORE HITTING • LEAD WINDOW – 1.5MM LEAD EQ

  18. Room SheildingCh. 9 • Workload Factor (W) -ma/sec/week – how much time during the week is the beam on (or ma/min/wk) • Occupancy Factor (T) - # of people in room - beyond the barrier • Use Factor (U) - % of time beam will strike a barrier (table pg 242) Primary vs Secondary • Leakage Radiation

  19. SHEILDING • HVL? • TVL? • 1 TVL = 3.3 HVL

  20. SHEILDING PG 72 RHB • HVL – expressed 2 ways • HOW MUCH IT REDUCES THE ORGINAL BEAM INTENSITY • HOW MUCH IS REQUIRED FOR BARRIER THICKNESS (amount needed to attenuated the beam

  21. HVL TVL • The amount of material required to reduce the energy of the beam by…….. • HVL _______________________ • TVL _____________________ • Examples 100 – 50 - 25 – 12.5 – 6.25 - 3.12 • ?How many to reduce to 1/2 ? 1/10th ?

  22. LEAKAGE RADIATIONmay not EXCEED • TUBE HOUSING 100mR / HR @ 1 meter

  23. SCATTER FROM THE PATIENT TABLE TOP, COLLIMATOR, TUBE HOUSING, BUCKY STRAY RADIATION – LEAKAGE OR SCATTER RADIATION PERSONNEL PROTECTION

  24. HIGH RADIATION AREA – • 100 mRem ( 0.1 rem / (1 msV) • @ 30 cm from the source of radiaton • RADIATION AREA – • RHB: 5 mRem ( 0.005 rem / (.05 msV) • @ 30 cm from the source of radiation • PUBLIC 2 mrem per week* (STAT)

  25. MONITORING • CONTROLLED AREA – Used by occupationaly exposed personnel (monitored) • 100mrem / WEEK • UNCONTROLLED AREA – PUBLIC • 2 mrem per week*

  26. A “controlled area” is defined as one • that is occupied by people trained in radiologic safety • that is occupied by people who wear radiation monitors • whose occupancy factor is 1

  27. Film Badges TLD POSL Pocket Dosimeter Ring Badge 10 mrem 5 mrem 1 mrem ? Personnel Monitoring DevicesACCURACY

  28. Film Badges TLD POSL Least cost $2.50 ?most used $10 ? Personnel Monitoring Devices$$$$$$$$$$$

  29. Q = t x תּ CUTIE PIE

  30. RHB NOTIFICATION (EXP IN 24 HOURS) (RP Syllabus – pg 68) IMMEDIATE reporting – WITHIN 24 HOURS • TOTAL DOSE OF 25 rems • Eye dose – 75 rem • Extremity – 250 RADS OVEREXPOSURE – received w/in 24 hrs Must be Reported WITHIN 30 DAYS • TOTAL DOSE OF 5 rems • Eye dose – 15 rem • Extremity - 50 REMS

  31. PARTICULATE (HIGH LET) ALPHA BETA FAST NEUTRONS More destructive ELECTROMAGNETIC (LOW LET) XRAY GAMMA (damaged caused by indirect action = free radicals – can be repaired) TYPES OF RADIATON(ALL CAUSE IONIZATION)

  32. measurement (Rad + QF = REM)

  33. Quality Factor“weighting factor for tissue” • See ch 7 - pg 155 5th ED • Organ tissue weighting factor • “ratio of risk of stochastic effects – rads to type of tissue

  34. A = STOCHASTIC “CHANCE” EFFECTS GENETIC, LEUKEMIA, CANCER DIAGNOSTIC RADIOLOGY B= NON-STOCHASTIC THRESHOLD EFFECTS DETERMINISTIC SOMATIC EFFECTS SKIN ERYTHEMA, CATARACTS, STERILITY RAD -MALIGNANCIES SOMATIC & GENETICSTOCHASTIC VS NON STOCHASTIC

  35. RHB – Rad Prot – CH. IX p 51 • ALARA (no minimum threshold) • STOCHASTIC EFFECTS – NON TRESHOLD (CA + GENETIC) • NON STHOCAHSTIC (DETERMINISTIC) SEVERITY OF EFFECTS VARIES WITH RADIATION DOSE (THRESHOLD) (CATARACTS, SKIN, BONE MARROW, STERILITY

  36. Linear vs non linear • Linear – direct response to the dose and the effects seen (proportionally) • Non linear – effects are not proportional to the dose received • S curve – rad therapy & skin erythema

  37. Direct & InDirect • Direct - DNA hit or with high LET • InDirect – most frequently occuring • Does not hit DNA directly – but can effect DNA through radiolysis • 90% of cell damage is repairable

  38. Ch 4 – pg 37 Fluoro Exam ↑ ↑ directly proportional to dose (pt & Rt) • Operator dose & pt dose • Image brightness & rad dose • mA, kvp, collimation, filtration, time, TPD ↑ ↓indirectly proportional to dose (pt & Rt) • Poor image quality • Room lighting • Tabletop absorption

  39. PATIENT DOSE • RAD • MR/MAS PER EXPOSURE - At each kVp level – there is a determined output for each radiographic room • EX 70 kvp = 2.5 mr/mas • ABD done 70 kVp, 20 mas • 2.5 x 20 = 50 mR for that one exposure. • LOOK AT formula: mr/mas Ch 8 Stat • CH 40 BUSHONG ( for 9/17)

  40. Mr/mas • A room uses • 3.5 mR @ 80 kVp • 2.5 mR @ 70 kVp • 4.5 mR @ 90 kVp • 5.6 mR @ 100 kVp • Find the patient’s exposure (ESE) for • KUB ( 40 mAs 70 kvp) = ___ mRad

  41. A room uses • 3.5 mR @ 80 kVp • 2.5 mR @ 70 kVp • 4.5 mR @ 90 kVp • 5.6 mR @ 100 kVp • 2 views Chest • (PA) 5 mas 90 kVp • (LAT) 10 mas 100 kVp _ • TOTAL = __________ mRad

  42. At 1 foot from a source the output intensity is 300 mR/hr and you were there for 20 minutes. What is your dose?

  43. At 1 foot from a source the output intensity is 300 mR/hr and you were there for 20 minutes. What is your dose?NOW - What is the intensity total if you moved 2 feet away and remained for additional 40 minutes?

  44. During a Fluoroscopy Procedure….. • Tube output was 1.5 R/min @ 2.2 ma • If at 2 feet from the radiation source the intensity of exposure is 240 mR per hour and the RT remains at this location for 10 minutes, then moved 4 feet away from the radiation source and remained there for 20 minutes? • What is your dose (RT) when you moved? • What is your (RT) total exposure? • What did the patient receive?

  45. ESE FOR FLUORO • TLD PLACED AT SKIN ENTRACE POINT • 1 – 5 R/MINUTE AVE IS 4 R/MIN • INTERGRAL DOSE – • 100 ERGS OF TISSUE = 1 RAD EXPOSURE • OR 1 GM RAD = 100 ERGS

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