1

Rad Protection & Radiobiologyreview244 09

2STAT 8 & 9

Protecting 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 Fluoroscopy – OUTPUTcheck with a LUCITE Phantom or Water Container

for consistent exposure output

• MONITORED

weekly (QC)

• RECORDED• Daily DURING

FLUORO EXAMS)

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)

8Exposure

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?

10Permissible

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)”

12Occupational DoseANNUAL LIMITS

• WHOLE BODY = 5 REMS / 5000mRem

• LENS OF THE EYE = 15 REMS

• EXTREMITIES = 50 REMS

13

14

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)

15

16

REGULATORY AGENCIES

• NCRP – National Council on Radiation Protection and Measurement

• Reviews recommendation for radiation protection & safety

• NRC – Nuclear Regulatory Committee

• Makes LAWS & enforces regulations

17

REGULATORY AGENCIES p143/5th

BEIR - Biological Effect of Ionizing Radiation

UNSCEAR – United Nations Scientific Committee on the Effects of Atomic Radiation

18

ROOM SHIELDING

• PRIMARY SHIELD – • PRIMARY BEAM DIRECTED AT

WALL• 1/16 LEAD - 7 FEET HIGH

19

ROOM SHIELDING

• SECONDARY – NO PRIMARY BEAM

• 1/32 LEAD

• CONTROL BOOTH (SECONDARY)

• BEAM SCATTERS 2X BEFORE HITTING

• LEAD WINDOW – 1.5MM LEAD EQ

20Room Sheilding

Ch. 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

21

SHEILDING

•HVL?

•TVL?

• 1 TVL = 3.3 HVL

22

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

23

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 ?

24

25LEAKAGE RADIATION

may not EXCEED

•TUBE HOUSING 100mR / HR

@ 1 meter

26

27

PERSONNEL PROTECTION

• SCATTER FROM THE PATIENT

• TABLE TOP, COLLIMATOR, TUBE HOUSING, BUCKY

• STRAY RADIATION – LEAKAGE OR SCATTER RADIATION

28

• 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)

29MONITORING

• CONTROLLED AREA – Used by occupationaly exposed personnel (monitored)

• 100mrem / WEEK

• UNCONTROLLED AREA – PUBLIC

• 2 mrem per week*

30

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

31Personnel Monitoring Devices

ACCURACY

• Film Badges

• TLD

• POSL

• Pocket Dosimeter

• Ring Badge

• 10 mrem

• 5 mrem

• 1 mrem

• ?

32Personnel Monitoring Devices

$$$$$$$$$$$

• Film Badges

• TLD

• POSL

• Least cost • $2.50 • ?most used

• $10

• ?

33

Q = t x ּת

CUTIE PIE

34RHB 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

35TYPES OF RADIATON

(ALL CAUSE IONIZATION)• PARTICULATE• (HIGH LET)• ALPHA• BETA• FAST NEUTRONS

• More destructive

• ELECTROMAGNETIC• (LOW LET)• XRAY • GAMMA• (damaged caused by

indirect action = free radicals – can be repaired)

36

measurement

(Rad + QF = REM)

37Quality 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

38

SOMATIC & GENETICSTOCHASTIC VS NON STOCHASTIC

• A = STOCHASTIC• “CHANCE” EFFECTS GENETIC, LEUKEMIA,

CANCERDIAGNOSTIC RADIOLOGY

B= NON-STOCHASTICTHRESHOLD EFFECTSDETERMINISTICSOMATIC EFFECTSSKIN ERYTHEMA,

CATARACTS, STERILITYRAD -MALIGNANCIES

39

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

40

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

41

42

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

43

• 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

44

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)

45

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

46

• 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

47

At 1 foot from a source the output intensity is 300 mR/hr and you

were there for 20 minutes. What is your dose?

48

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?

49

• 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?

50

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

51

• Pg 39 Integral Dose

• Total energy absorbed from the beam

• Unit is GRAM RAD (1 gm rad = 100 ergs)

52

• The NCRP states that: the risk (to the embryo/fetus) is considered to be negligible at 5 rads or less when compared to the other risks of pregnancy

• and the risk of malformation is significantly increased above control levels only at doses above 15 rads

53

10 – 25 RAD Rule and Pregnancy Bush p 545

• Below 10 RAD (100mgy) ther ab NOT indicated

• Above 25 RAD may justify TAB

• FETAL doses RARELY reach 5 RAD

54

• As shown in animal experiments, deleterious effects to the embryo may be produced with doses of as little as _____ delivered to the embryo.

• a. 5 rads • b. 15 mrads• c. 15 rads • d. 50 mrads • e. 50 rads

55

PERSONNEL PROTECTION

• PROTECTIVE APRONS –

• 0.25 PB = 97% ↓ TO SCATTER

• 0.5 PB = 99.9% ↓ TO SCATTER

• THYROID SHEILDS (0.25 & 0.5)

• GLOVES (0.25 & 0.5)

56Gonad shielding & dose

• ♀ receive 3x more dose than

• ♂ for pelvic x-rays

• 1 mm lead will reduce exposure

(primary) by about 50% ♀

• by about 90 – 95 % ♂

57

• HIGHLIGHTS RE FLUORO & RAD PROT

• PG 43- lymphocytes most depressed

• 300 rads ♀ OVARIES = TEMP STERILITY

• 30 rads ♂ TESTIES = TEMP STERILITY

• PG 45 – REPEAT INFO

58GERM CELLS in Females

(present at birth)• HIGHLY RADIOSENSITIVE = DEPENDS

OF STAGE OF DEVELOPMENT• Mature ovum do not divide frequently• (20-30 yrs old - least sensitive)• Immature very sensitive• If exposed ova meets sperm – may

contain damaged chromosomes – passing genetic damage to offspring =

• CONGENTIAL ABNORMALITIES

59

GONAD SHIELDING pg 87

• MUST BE . 5 MM OF LEAD

• MUST BE USED WHEN GONADS WILL LIE WITHING 5 CM OF THE COLLIMATED AREA (RHB)

• FLAT / CONTACT / SHADOW

60

Doses above 50 gy