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Radiation ProtectionRoom Shielding beginRadiobiology & RHB regs

Stat Ch 3,4, 9, 10, 11 & 12BUSH: Ch. 38 & 39+ beginning someRHB – Rad Prot Syllabus

RTEC 244 – 2011 WEEK 3 DAY 1 & 2

What type of RADIATION are you providing PROTECTIONfor THE TECHNOLOGIST ? & THE PATIENT ???

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• The average person in the United States receives about 360 mrem every year whole body equivalent dose. This is mostly from natural sources of radiation, such as radon

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Artificial, radiation. Sources of artificial ionizing radiation include the following: •Consumer products containing radioactive material•Air travel•Nuclear fuel for generation of power•Atmospheric fallout from nuclear weapons testing•Nuclear power plant accidents•Medical radiation

BERT

• BERT is based on an annual U.S. population exposure of approximately 3 millisieverts per year (300 millirems per year)

• AKA - GSD – gonadal significant dose

• What does this mean• What does it compare?

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• An analysis of available data on ionizing radiation effects suggests that 64-slice coronary CT angiography scans

• put young women at a greater risk of developing cancer later in life than any other patient,

• according to a study in the July 18 issue of the Journal of the American Medical Association.

• More on this later……

Which type of radiation is predominant above 80 kvp ?

WHAT ARE THE 2 MAJOR INTERACTIONS IN THE BODY?

How much of the radiation received by the patient?

• PHOTOELECTRIC(in the body = absorption)

• COMPTON(in the body – scatter radiation)

9 RADIATION PROTECTION

AT 1 METER DISTANCE -• 1/1000 OF INTENSITY

PRIMARY XRAY or 0.1%• LEAKAGELEAKAGE

RADIATION RADIATION

• TUBE HOUSING 100MR / HR @ 1 METER

What determines the type of shielding needed?10

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ROOM SHIELDING

• PRIMARY SHIELD – • PRIMARY BEAM DIRECTED AT

WALL• 1/16 LEAD - 7 FEET HIGH

12 ROOM SHIELDING• SECONDARY – NO PRIMARY BEAM

• 1/32 LEAD

• CONTROL BOOTH (SECONDARY)

• BEAM SCATTERS 2X BEFORE HITTING

• LEAD WINDOW – 1.5MM LEAD EQ

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Primary & Secondary Barriers

What type of barrier is the control booth?Why?

What would this be used for?Which type of equipment?

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PERSONNEL PROTECTION

• STANDING BEHIND A PROTECTIVE PRIMARY (1/16TH pb) BARRIER:

• PRIMARY RADIATION EXPOSURE – 99.87% REDUCED

• PORTABLE BARRIER = 99 % REDUCTION

15 Room Shielding

• 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 during workweek - beyond the barrier

• Use Factor (U) - % of time beam will strike a barrier (table pg 301) Primary vs Secondary

• (given in fractions• Leakage RadiationFor each wall, door, and other barrier in an x-ray room that is to provide protection

against radiation, the product of W × U × T must be determined. The workload is generally fixed by the overall use of the x-ray unit, whereas the use and occupancy factors are usually different among various barriers.

Use Factor Primary Barrier

Full use (U = 1)

Floors of radiation rooms except dental installations, doors, walls, and ceilings of radiation rooms exposed routinely to the primary beam

Partial use (U = )Doors and walls of radiation rooms not exposed routinely to the primary beam; also, floors of dental installations

Occasional use (U = )

Ceilings of radiation rooms not exposed routinely to the primary beam; because of the low use factor, shielding requirements for a ceiling are usually determined by secondary rather than primary beam considerations

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17Location Occupancy Factor (T)

Administrative or clerical offices; laboratories, pharmacies, and other work areas fully occupied by an individual; receptionist areas, attended waiting rooms, children's indoor play areas, adjacent x-ray rooms, film reading areas, nurses’ stations, x-ray control rooms

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Rooms used for patient examinations and treatments 1/2

Corridors, patient rooms, employee lounges, and staff rest rooms

1/5

Corridor doors‡

Public toilets, unattended vending areas, storage rooms, outdoor areas with seating, unattended waiting rooms, patient holding areas

1/20

Outdoor areas with only transient pedestrians or vehicular traffic, unattended parking lots, vehicular drop-off areas (unattended), attics, stairways, unattended elevators, janitors’ closets

1/40

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Measurements Report No. 147 New Shielding Guidelines

Item New Approach

WorkloadMore realistic use of contemporary survey data

Leakage and scatter Explicit barrier calculations

Use factorAdjusted for beam direction data reflecting actual usage patterns

Occupancy factorRealistic assumptions of occupancy of low-occupancy areas (e.g., stairwells)

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• Units of mA-minutes/week are used to determine what for a specific room?

• a. Workload

• b. Use factor

• c. Occupancy factor

• d. Distance

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SHEILDING

•HVL?

•TVL?

• 1 TVL – 3.3 HVL

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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

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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 LEAKAGE RADIATIONmay not EXCEED

• TUBE HOUSING

• 100mR / hour

• @ 1 meter

25 RADIATION PROTECTION

AT 1 METER DISTANCE -• 1/1000 OF INTENSITY

PRIMARY XRAY or 0.1%

PERSONNEL PROTECTION

• SCATTER FROM THE PATIENT

• TABLE TOP, COLLIMATOR, TUBE HOUSING, BUCKY

• STRAY RADIATION – LEAKAGE OR SCATTER RADIATION

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27 PERSONNEL PROTECTION• SCATTER FROM THE PATIENT

• TABLE TOP, COLLIMATOR, TUBE HOUSING, BUCKY

• STRAY RADIATION –

• LEAKAGE OR

• SCATTER RADIATION

28 OFF FOCUSRADIATION

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SHADOW OF

SOMEONE’S HEAD =

OFF FOCUS FROM TUBE

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• 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)

32 MONITORING

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

• 100mrem / WEEK

• UNCONTROLLED AREA – PUBLIC

• 2 mrem per week*

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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

34 CARDINAL RULESOF RADIATION PROTECTION

•TIME

•DISTANCE

•SHIELDING

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Protecting Patients & Personnel

1. COMMUNICATE

2. COLLIMATE

3. SHIELD

4. ↑ kVp ↓ mAs

Limit motion / repeat exams• Communication, Collimate,

Shield,

• Immobilization

• Reduce exposure time

• Faster Image receptors (F/S)

Review

• At a 90-degree angle to the primary x-ray beam, at a distance of 1 m (3.3 feet), the scattered radiation is what fraction of the intensity of the primary beam?

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• If a radiographer stands 6 m away from an x-ray tube and receives an exposure rate of 4 mR/hr, what will the exposure rate be if the same radiographer moves to stand at a position located 12 m from the x-ray tube?

• A.1 mR/hr

• B.2 mR/hr

• C.3 mR/hr

• D.4 mR/hr

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• Which of the following are methods that can be used by a C-arm operator to reduce occupational exposure for himself or herself and other personnel?

• 1. Collimate the x-ray beam to include only the anatomy of interest.

• 2. Use the foot pedal or the hand-held exposure switch with their cables extended away from the machine as far as possible whenever making an exposure.

• 3. Use magnification whenever possible to better visualize body parts.

• A. 1 and 2 only • B. 1 and 3 only • C. 2 and 3 only • D. 1, 2, and 3

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• Of the following factors, which is considered when determining thickness requirements for protective barriers?

• 1. Occupancy factor (T)

• 2. Workload (W)

• 3. Use factor (U)

• A. 1 only

• B. 2 only

• C. 3 only

• D. 1, 2, and 3

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41 According to your California syllabus, list 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

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The greatest contribution of unnecessary radiation exposure to the patient comes

from the x-ray operator’s failure to ?

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The greatest contribution of unnecessary radiation exposure to the patient comes

from the x-ray operator’s failure to

COMMUNICATE

COLLIMATE

SHIELD

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Radiation Hormesis p158 Stat

• Suggest that

• There is a beneifcial consequence of radiation for populations continuously exposed to moderately high levels of radiation

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What is the difference betweenX-ray & Gamma?

BEGIN RADIOBIOLOGY

46 TYPES 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)

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Quality Factor• How dangerous the type of radiation

is - the biological effect on tissue

• Alpha + fast neutrons = 20

• X-ray, Beta, Gamma . = 1

• (Rad + QF = REM)

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Why did the bunny die??

BUNNY A

• Received 200 rads

BUNNY B

• Received 200 rads

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Why did the bunny die??

BUNNY A

200 rads of X-RAY = 200 RADS

BUNNY B

200 rads of alpha =

4000 rads

51 Quality Factor“weighting factor for tissue”

• See ch 9 pg 197 6th Ed

• Organ tissue weighting factor

• “ratio of risk of stochastic effects – rads to type of tissue

52SOMATIC & GENETIC

STOCHASTIC VS NON STOCHASTIC

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

CANCERDIAGNOSTIC RADIOLOGY

B= NON-STOCHASTICTHRESHOLD EFFECTSDETERMINISTICSOMATIC EFFECTSSKIN ERYTHEMA,

CATARACTS, STERILITYRAD -MALIGNANCIES

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54 LET linear energy transfer• The amount of energy that may be

deposited in tissue as radiation passes

• Factor in assessing potential damage to organs/tissues

• LET to RBE (pg 114 Stat)

LOW LET –

•X-RAY / GAMMA

HIGH LET

•ALPHA

•FAST NEUTRONS

55SED = SKIN ERYTHEMA DOSE

• LINEAR – NONTHRESHOLD• DEPENDANT ON• DOSE RECEIVED• PERIOD OF TIME OVER IT WAS

RECEIVED• AREA OF IRRADIATED TISSUE• SENSITIVITY

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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 11 Stat • CH 40 BUSHONG

57 Time to start some dose calculations…….

Mr/mas

• A room uses TUBE OUTPUT

• 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

58• 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

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EXPOSURE RATES FLUORO

• MA IS 0.5 MA TO 5 MA PER MIN

• AVE DOSE IS 4 R / MIN

• IF MACHINE OUTPUT IS 2 R/MA/MIN = WHAT IS PT DOSE AT 1.5 MA FOR 5 MIN STUDY?

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

were there for 20 minutes. What is your dose?

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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?

62• During a Fluoroscopy Procedure…..

• Tube output was 1.5 R/min @ 2.2 ma

• If at 1 foot from the radiation source the intensity of exposure is 240 mR per hour and you remain at this location for 10 minutes, you then moved 2 feet away from the radiation source and remained there for 20 minutes?

• What is your dose when you moved?

• What is your total exposure?

• What did the patient receive?

Pregnancy & ExposureTech & Patient Safety

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64Declared 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)

• www.ntc.gov/NRC/RG/08/08-013.html

65 Pregnancy & Embryo

Mother –

occupational worker (5 rem)

• Baby – (500 mRem)

• .5 rem/ year .05 rem/month

• 5 mSv .5 mSv / month

66DOSE TO FETUS VS ESE

67 “Embryo approx 1/50 mother ESE dose”

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• 10 day rule• No threshold for exposure• Leukemia , congential abnormailies cancer

induction, reasbortion or death of the embryo and genetic effects

• Therapetuic Abortion “not justified”• 25 rads or less – no injury seen• ABSORBED DOSES – 50 RADS – could

result in a spontaneous abortion

69 FETAL EFFECTS

• Most sensitive in first trimester - large number or stem cells

• First two weeks – death by spontaneous abortion

• A dose of 10 rad (.10 gy) - expected death rate occurs at 10% higher than that would normally exist

7010 – 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

71• 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

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PREGNANT PATIENTS

• ASCERTAIN LMP - IF FETUS IS EXPOSED• PHYSICSTS WILL NEED INFORMATION:• WHICH XRAY MACHINE USED (MR/MAS)• # OF PROJECTIONS (INC REPEATS)• TECHNIQUE FOR EACH EXPOSURE• SID • PATIENT MEASUREMENT AT C/R• FLUORO TIME & TECHNIQUE USED• PHYSICIST WILL CALCULATE FETAL DOSE

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What is affected – 1st trimester

• SKELETAL SENSITIVE WK 2 – 10• CNS Wk 8 – 15• & organs

• CNS MOST PREVALENT• TUMORS / METAL RETARDATION

• MORE ON FETAL EFFECTS LATER THIS SEMESTER IN RADIOBIOLOGY SECTION…

ADVISORY AGENCIES –Ch9

• NCRP• NCR• BEIR• BERT• ICRP

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REGULATORY AGENCIES

• NCRP – National Council on Radiation Protection and Measurement

• Reviews recommendation for radiation protection & safety

• NRC – Nuclear Regulatory Committee

• Makes LAWS & enforces regulations

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REGULATORY AGENCIES p143/5th

–BEIR - Biological Effect of Ionizing Radiation

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

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NCRP

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• During Fluoro, for an under the table tube, the maximum intensity of scatter from the patient is received at a scatter angle of:

• A. 90 B 45 C.135 D. 30 degrees

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• During Fluoro, for an over the table tube, the maximum intensity of scatter from the patient is received at a scatter angle of:

• A. 90 B 45 C.135 D. 30 degrees

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• If you convert 12 millisieverts (mSv) to Rems you will obtain

• A 1.2 Rem

• B 120 Rem

• C 0.012 Rem

• D 12 Rem

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• Units of mA-minutes/week are used to determine what for a specific room?

• a. Workload

• b. Use factor

• c. Occupancy factor

• d. Distance

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• Each time an x-ray beam scatters, its intensity at 1 meter from the scattering object is what fraction of its original intensity?

• A. 1/10

• B. 1/100

• C. 1/500

• D. 1/1000

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List one RECORDING method that HAS LOWERPATIENT DOSE:

______________________

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Between spot film cassettes and photospot films,

the_____will increase patient dose. However, between the two the ______will produce

better image quality.

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The x-ray tube current automatically increases to

________level of mA when a spot film is taken.

88 Gonad shielding & dose

• ♀ receive 3x more dose than

• ♂ for pelvic x-rays

• 1 mm lead will reduce exposure

(primary) by about _______♀

• by about ______ for ♂

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RADIATION PROTECTIONThe Patient is the largest

scattering object

• Lower at a _____ DEGREE ANGLE from the patient + PRIMARY BEAM

AT 1 METER DISTANCE -• ________ OF INTENSITY

PRIMARY XRAY or _____

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RADIATION PROTECTIONThe Patient is the largest

scattering object

• Lower at a 90 DEGREE ANGLE from the patient + PRIMARY BEAM

AT 1 METER DISTANCE -• 1/1000 OF INTENSITY

PRIMARY XRAY or 0.1%

91 Radiographic Exposure- Bushong

• At worst – you will have a life span shortening of 10 days/ 1 RAD

• RT is a SAFE profession

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The END – Be Careful !!!