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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

Radiation Protection

Bushong Ch. 37, 39 & 40

objectives
Units of Measurement

NCRP

ALARA

DOSE –

Cumulative

Annual

Patients

Fetus

Entrance Skin Exposure

Skin erythema dose

Genetically significant dose

Objectives
objectives1
Objectives
  • Radiation units of measurements
  • QF – Quality Factor
  • Cardinal Rules of Radiation Protection
  • Personal Dose Monitoring & Field Instruments
regulatory agencies
REGULATORY AGENCIES
  • NCRP – National Council on Radiation Protection and Measurement
  • Reviews recommendation for radiation protection & safety
  • NRC – Nuclear Regulatory Committee
  • Makes LAWS & enforces regulations
standard vs si units
STANDARD VS SI UNITS
  • R - C/kg
  • Rem - Sievert
  • Rad - Gray
measurement
measurement

100 R = 1 C/kg

1Rad = 1/100 Gray

1 Rem = .01 Sievert

(Rad + QF = REM)

1 REM = 10 mSv

1 Rem = 1000mRem

permissible occupational dose
Permissible Occupational Dose
  • Annual dose:
  • 5 Rem / year 50 mSv / year
  • Cumulative Dose
  • 1rem x age 10mSv X age
occupational dose annual limits
Occupational DoseANNUAL LIMITS
  • WHOLE BODY = 5 REMS / 5000mRem
  • LENS OF THE EYE = 15 REMS
  • EXTREMITIES = 50 REMS
public exposure
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
occupational exposures
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
two types of exposures
Two types of exposures
  • Radiation worker
  • Patient
effects of radiation in utero are time and dose related
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.
irradiation in utero
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
declared pregnant worker
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)

pregnancy embryo
Pregnancy & Embryo

Mother –

occupational worker (5 rem)

  • Baby – (500 mRem)
  • .5 rem/ year .05 rem/month
  • 5 mSv .5 mSv / month
pregnant patient
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?
pregnant patients
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
unsuspected pregnancy
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
pregnant patients1
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
patient dose
Patient dose
  • Is reported in Entrance Skin Exposure (ESE)
over radiation to skin too much time under beam
Over Radiation to SkinToo much time under beam

Skin burns from 30 min of beam on time

slide30
SED
  • SKIN ERYTHEMA DOSE
  • LINEAR – NONTHRESHOLD
  • DEPENDANT ON
  • DOSE RECEIVED
  • PERIOD OF TIME OVER IT WAS RECEIVED
  • AREA OF IRRADIATED TISSUE
  • SENSITIVITY
protective shielding
Protective shielding
  • Gonads
  • Breasts
  • Thyroid
  • Lenses of the eyes
  • Long bones

(bone marrow)

pediatric exposure
PEDIATRIC EXPOSURE
  • More sensitive to radiation than adults
  • Limit beam time
  • May remove grid (reduce exposure)
  • Collimation & shielding !!!!!!!!!!!!!!!
  • Gender differences
  • Immobilization
slide34
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
reducing repeats
REDUCING REPEATS
  • TECHNIQUE CHARTS
  • CAREFUL REVIEW OF TECHNICAL FACTORS
  • REFER TO TECHNIQUE BOOK AND
  • ASK WHEN YOU ARE NOT SURE!
filtration reduces patient exposures
Filtration REDUCES PATIENT EXPOSURES
  • REMOVES LOW ENERGY PHOTONS
in terms of patient dose what is the best combination to reduce exposure to your patent
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?
in terms of patient dose what is the best combination to reduce exposure to your patent1
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?
sheilding
SHEILDING

TECHNOLOGIST . 25 mm LEAD

  • LEAD APRON, GLOVES
  • THYROID SHIELD, GLASSES

PATIENT –

GONAD SHEILDING

. 5 mm LEAD

gonad shielding
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
lead protective aprons
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
types of sheilding
TYPES OF SHEILDING
  • FLAT /CONTACT
  • SHAPED
  • SHADOW
which shielding type is best for males females
Which shielding type is best for Males? Females?
  • Males = Shaped
  • Females = Flat contact
radiation protection the patient is the largest scattering object
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%
slide52

FLUOROSCOPY –

ABOVE AND BELOW THE TABLE TUBE EXPOSURE TO TECH

DURING FLUOROSCOPY THE TECHNOLOGIST SHOULD REMAIN AS FAR FROM THE PATIENT AS PRACTICLE

ALWAYS WEAR YOUR LEAD APRON & THYROID SHIELD DURING FLUOROSCOPY!

GOT A THYROID SHIELD?

mobile radiography
Mobile Radiography
  • Each portable machine should have at least one lead apron on it permanently.
  • More aprons are better! Thyroid shields are not as important
personnel monitoring devices
Personnel Monitoring Devices
  • Film Badges
  • Thermoluminescent Dosimeters (TLD)
  • Pocket Dosimeters
  • Optically Stimulated Luminescence (OSL Dosimeters)
  • Ring Dosimeter(Nuclear Medicine Techs)
personnel monitoring devices1
Personnel Monitoring Devices
  • Are not to be worn when you are the patient. The dose is recording your OCCUPATIONAL exposure
  • Monitoring is required when there is the probability that an individual will receive more than 1/10 or 10% of the maximum occupational dose limit.
  • What is the occupational dose limit?
  • Do monitoring devices protect from exposure?
film badges
Film Badges
  • General use in the 1940’s
  • Dental film sandwiched between metal filters (aluminum & copper) inside a plastic holder
  • OD on the film is related to technologist exposure
  • Exposures less than 10 mR are not measured
  • Should be never left in the car because fogging can occur with high temperatures
advantages disadvantages film badge
Inexpensive

Easy to handle

Easy to process

Accurate

Permanent record

Cannot be reused

Cannot be worn for more than 1 month because of potential film fog due to heat and himidity

Only records above 10 mR

Advantages DisadvantagesFilm badge
thermoluminescence dosimeters
Thermoluminescence Dosimeters
  • Lithium fluoride in power or a small chip (3mm square, 1mm thick)
  • When exposed to x-rays energy is absorbed in the form of excited e-
  • When heated the excited e- fall back to normal orbital state and emit visible light. The light is proportional to dose
advantages disadvantages tld
More sensitive and more accurate than film

Can measure as low as 5 mR

Is not sensitive to heat or humidity

Recorded quarterly (can be use for up to 1 year)

Crystals are reusable after heating

Cost (twice of the film badge)

Not a permanent record (except for dosimetry report)

Advantages DisadvantagesTLD
optically stimulated luminescence most commonly used today
Optically Stimulated LuminescenceMost commonly used today
  • Or Pulse Optically Stimulated Luminescence = OSL or POSL
  • Uses aluminum oxide as the detector
  • Laser light stimulates crystals to release traped e- in the form of visible light
  • Similar to TLD’s in use but more sensitive to radiation exposure (1mrad) and more accurate
measurement1
FILM BADGE

TLD

OSL

POCKET DOSIMETER

ABOVE 10 MREM

ABOVE 5 MREM

1 MREM

NOT ACCURATE

MEASUREMENT
maximum use period
FILM BADGE = MONTHLY

POCKET DOSIMETER= DAILY

TLD/ OSL = QUARTERLY

Maximum use period
field survey instruments
Field Survey Instruments
  • Detects the presence of radiation and the intensity of the source
  • Geiger-Mueller counter
questions
Units of Measurement

NCRP

ALARA

DOSE –

Cumulative

Annual

Patients

Fetus

Entrance Skin Exposure

Skin erythema dose

Genetically significant dose

Questions?
questions1
Questions?
  • Radiation units of measurements
  • QF – Quality Factor
  • Cardinal Rules of Radiation Protection
  • Personal Dose Monitoring & Field Instruments