RT 123
INTRODUCTION & Review of
Radiation Protection
(Merrills Ch. 2)
WK #3
MARIE & PIERRE CURIE
•
•
•
•
1898
“NAMED RADIOACTIVITY”
DEVELOPED A RADIATION DETECTOR
1914 (WW1) DEVELOPED A MOBILE
RADIOGRAPHY X-RAY “CAR” TO TAKE
XRAY IN THE BATTLE FRONTS
• TRAINED 150 “TECHNICIANS” TO
OPERATED CARS
Early measurement of Radiation
• Skin dryness & erythema
– AKA radiodermatitis
• Ulcers formed
• Cataracts
• Cancers
DIAGNOSTIC
RADIOLOGY
• STATIC – STILL SHOTS
• DYNAMIC
• XRAYS IN MOTION
• FLUOROSCOPY
STANDARD VS SI UNITS
• R - C/kg
•Rem - Sievert
• Rad - Gray
measurement
100 R = 1 C/kg
1Rad = 1/100 Gray
1 Rem = .01 Sievert
(Rad + QF = REM)
1 REM = 10 mSv
1 Rem = 1000mRem
Quality Factor
• How dangerous the type of
radiation is
• Alpha + fast neutrons = 20
• X-ray, Beta, Gamma . = 1
REM
• IS A PRODUCT OF THE
• QF x RAD
Why did the bunny die??
BUNNY A
• Received 200 rads
BUNNY B
• Received 200 rads
Why did the bunny die??
BUNNY A
200 rads of X-RAY =
200 RADS
BUNNY B
200 rads of alpha =
4000 rads
Permissible
Occupational Dose
• Annual dose:
• 5 Rem / year 50 mSv / year
• Cumulative Dose
• 1rem x age 10mSv X age
Occupational Dose
ANNUAL LIMITS
• WHOLE BODY = 5 REMS
/ 5000mRem
• LENS OF THE EYE = 15
REMS
• EXTREMITIES = 50 REMS
OCCUPATIONAL EXPOSURES
• 5 REMS / YEAR
BUT NOT TO EXCEED 1.25
REM/QUARTER
AVERAGE ACTUAL EXPOUSRE IS
APPROXIMATELY 50 mrem/year
• OLD “MPD 5(Age – 18)”
PUBLIC EXPOSURE
•
•
•
•
10 % OF OCCUPATIONAL
NON MEDICAL EXPOSURE
.5 RAD OR 500 MRAD
UNDER AGE 18 AND
STUDENT
• .1 rem 1 mSv
• Pg 98 RTA BOOK
CARDINAL RULES
OF RADIATION PROTECTION
• TIME
• DISTANCE
• SHIELDING
ROOM SHIELDING
• PRIMARY SHIELD –
• PRIMARY BEAM DIRECTED AT
WALL
• 1/16 LEAD - 7 FEET HIGH
ROOM SHIELDING
•
•
•
•
SECONDARY – NO PRIMARY BEAM
1/32 LEAD
CONTROL BOOTH (SECONDARY)
BEAM SCATTERS 2X BEFORE
HITTING
• LEAD WINDOW – 1.5MM LEAD EQ
MONITORING
• CONTROLLED AREA – Used by
occupationally exposed personnel
(monitored)
• 100mrem / WEEK
• UNCONTROLLED AREA – PUBLIC
• 2 mrem per week*
SHEILDING
TECHNOLOGIST . 25 mm
LEAD
• LEAD APRON, GLOVES
• THYROID SHIELD, GLASSES
PATIENT –
GONAD SHEILDING
. 5 mm LEAD
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
TYPES OF SHEILDING
• FLAT /CONTACT
• SHAPED
• SHADOW
Personnel Monitoring Devices
•Film Badges
•TLD / POSL
•Pocket Dosimeter
•Ring Badge
MEASUREMENT
• FILM
BADGE
• TLD
• POSL
• POCKET
DOSIMETER
• ABOVE 10 MREM
• ABOVE 5 MREM
•
1 MREM
• NOT ACCURATE
REM
• IS A PRODUCT OF THE
• QF x RAD
Pregnancy & Embryo
Mother –
occupational worker (5 rem)
• Baby – (500 mRem)
• .5 rem/ year .05 rem/month
• 5 mSv
.5 mSv / month
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)
•
www.ntc.gov/NRC/RG/08/08-013.html
Pregnant patient
• ALWAYS ASK LMP before exposure made
• “10-day Rule” No longer used
• “Grace period” of implantation
• STATE – Beam 5 cm within gonads
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
RADIATION DOSE TO
PATIENTS
• ESE - ENTRACE SKIN EXPOSURE
(MEASURED BY A TLD)
•
•
•
•
SKIN DOSE
GONADAL DOSE
BONE MARROW DOSE
(MEAN GLADULAR DOSE- MAMMO)
AP VS PA EXPOSURE/ESE
SOMATIC & GENETIC
STOCHASTIC VS NON STOCHASTIC
• A = STOCHASTIC
• “CHANCE” EFFECTS
GENETIC, LEUKEMIA,
CANCER
DIAGNOSTIC RADIOLOGY
B= NON-STOCHASTIC
THRESHOLD EFFECTS
DETERMINISTIC
SOMATIC EFFECTS
SKIN ERYTHEMA,
CATARACTS, STERILITY
RAD -MALIGNANCIES
GSD
• GENETICALY SIGNIFICANT DOSE
• Takes all of the population into account
• Annual AVERAGE gonadal dose to
population of childbearing age
• 0. 20 mSv
• rem or rad???
or 20 millirem
REDUCING REPEATS
• TECHNIQUE CHARTS
• CAREFUL REVIEW OF TECHNICAL
FACTORS
• REFER TO TECHNIQUE BOOK AND
• ASK WHEN YOU ARE NOT SURE!
Carlton Ch 13 - p. 208 & 210 & 214
•
•
•
•
“AVE” CHEST EXPOSURE - 2 IMAGES
(Ave – Pt meas 23cm pa 40cm lat)
PA 110 KVP 5 MAS 16:1 GRID 400RS 72”
LAT 110 KVP 20 MAS 16:1 GRID 400 RS 72”
• WHAT IS THE PATIENT’S DOSE??
PEDIATRIC EXPOSURE
• MORE SENSITIVE TO RADIATION
THAN ADULTS
• LIMIT BEAM TIME
• MAY REMOVE GRID (REDUCE
EXPOSURE)
• AP VS PA
• COLLIMATION & SHIELDING
!!!!!!!!!!!!!!!
• GENDER DIFFERENCES
• IMMOBILATION