RADIATION PROTECTION Presented by Rose Aehle RT (R,M) MS Program Coordinator, Montgomery College
REFERENCES Bushong Radiologic Science for Technologists, Eighth Edition Ehrlich, Patient Care in Radiography, Sixth Edition Callaway, Mosby’s Comprehensive Review of Radiography Saia, Lange Q & A Radiography Examination, 6 th Edition Sherer, Radiation Protection in Medical Radiography, Fifth Edition 2008 ARRT REGISTRATION HANDBOOK The College of St. Catherine, Development Testing Program for Radiography
WHAT THE REGISTRY WANTS YOU TO KNOW (2008 ARRT handbook)
BIOLOGIC ASPECTS OF RADIATION Dose response curves (Sherer) Line 1 No level of radiation can be considered safe. Response to exposure is directly proportional Diagnostic imaging Line 2 Threshold is assumed, response expected at lower doses Response to exposure is directly proportional Cataractogenesis Radiation Therapy
BIOLOGIC ASPECTS OF RADIATION Dose response curves (Sherer) Line 3 Non linear (sigmoid or hypothetical sigmoid) dose response DIAGRAM B Non linear, threshold dose response used in radiation therapy
BIOLOGIC ASPECTS OF RADIATION Damage/eradication of abnormal cells Repair Death/ Repair How to read a nonlinear threshold dose response curve FRACTIONATION A fraction of a dose of ionizing radiation given over a period of time PROTRACTED DOSE A low amount of ionizing radiation given continously
Linear quadratic nonthreshold dose response curve Risks associated with low dose levels of low LET radiations Stochastic somatic and genetic effects “Leukemia, breast cancer and heritiable damage assumed to follow this curve” Sherer
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LET – AMOUNT OF ENERGY DEPOSITED BY RADIATION PER UNIT LENGTH OF TISSUE TRAVERSED calloway RBE- QUANTITATIVE MEASUREMENT OF BIOLOGIC EFFECT QF – NUMERIC UNIT GIVEN TO RADIATION BASED ON RBE TO DETERMINE REM
Facts about LET SPARSELY IONIZING RADIATION GAMMA AND X-RAY LOW LET OF 3 KEV per micrometer OR LESS –ARE PENETRATING –INTERACT RANDOMLY ALONG ITS TRACK (STOCHASTIC) AS LET INCREASES SO DOES RBE HIGH LET –LOW PENETRATION –SLOW MOVING –Direct Effect
Effective dose (E)=Wr X Wt x absorbed dose Wr -Radiation weighting factor Wt –Tissue weighting factor number assigned to different types of ionizing radiation. Dependent of the LET of particular radiation Tissue radiosensitivity of irradiated material
FACTS ABOUT RBE DOSE OF STANDARD RADIATION NECESSARY TO PRODUCE A GENETIC EFFECT -------------------------------------------------------------------- DOSE OF TEST RADATION NECESSARY TO PRODUCE THE SAME EFFECT STANDARD RADIATION IS TYPICALLY 250 kVp (Bushong has a range of 200 – 250 kVp) Test radiation can range for x-rays to other types of ionizing radiation RBE for x-rays is one Higher LET’s have Higher RBE = Higher QF
WT factors -which is more radiosensitive? What is more radiosensitive? Stomach or bladder? Gonads or red bone marrow? Colon or breast? Thyroid or skin?
FACTS ABOUT QF REM IS CALCULATED BY MULTIPLYING THE QF OF A PARTICULAR TYPE OF RADIATION X RAD QF FOR X-RAYS IS 1 THEREFORE ONE RAD OF EXPOSURE TO X-RAY = ONE REM QF FOR ALPA IS 20 –HIGH LET –SLOW MOVING –LOW PENETRATION THEREFORE ONE RAD OF EXPOSURE TO ALPHA = 20 REMS
LD 50 LD 50/60 THE AMOUNT OF RADIATIONTHAT WILL CAUSE 50% OF EXPOSED INDIVIDUALS TO DIE WITHIN 60 DAYS
WHAT DOES THE LAW OF BERGONIE AND TRIBONDEAU SAY Re RADIOSENSITIVITY? Stem cells are_____________ Mature cells are ____________ Cells with _________metabolic and ___________mitotic activity are radiosensitive Cells which are differentiated are _____________ Radiosensitive Radioresistent High/high Radioresistent
SOMATIC Short Term ARS –Hemopoietic (BONE MARROW SYNDROME) 100-1000 RAD –25 RADS CAN DEPRESS BLOOD COUNT –Gastointestinal (600- 1000 RADS) –CNS (5000 RADS Locally Erythema 300-1000 RADS Epilation Delay/suppress menstruation 10 RADS Temporary sterility (both sexes – 200 RADS LONG TERM THOSE EFFECTS THAT CAN BE DIRECTLY RELATED TO HIGH DOSE OF RADIATION ARE CLASSIFIED AS NONSTOCHASTIC Cataract Reduced fertility Fibrosis Organ atrophy Sterility LONG TERM STOCHASTIC CANCER EMBRYOLOGIC EFFECTS
CARCINOGENESIS The cancer that can be ALMOST classified as radiounique is leukemia Has a short latency period Has a linear nonthreshold dose response curve Epidemiologic studies indicate a higher incidences in leukemia after large exposures Radium watch dial workers –bone ca Uranium miners – lung ca Early medical radiation workers – leukemia Thymus gland treatment – thyroid ca Children of Marshal Island – thyroid ca Atomic bomb survivors – leukemia/breast, lung and bone
WHAT CAN HAPPEN WHEN IONIZING RADIATION HITS THE CELL? a) Nothing b) Direct effect c) Indirect effect d) All of the above
HIGH LET is associated with which effect? a)No effect b)Direct effect c)Indirect effect d)Radiolysis of water
The following is true regarding indirect effect I) DNA is impacted by free radicals II) Some free radicals may chemically combine to form hydrogen peroxide III) DNA is directly struck by radiation IV)The minority of the damage to body is caused by indirect effect a)I only b)I and II only c)I, II and III only d)All of the above
TARGET THEORY A)THE DNA IS DIRECTLY HIT B)ONLY SOME CELLS HAVE MASTER MOLECULES THAT DIRECT CELL ACTIVITY C)ONE CANNOT DETERMINE IN ANY CELL DEATH IF THE DEATH WAS RESULT OF DIRECT OR INDIRECT EFFECT
Spontaneous abortions during first 2 weeks of pregnancy-- 25 RAD or higher 2 nd week to 10 th week – major organogenesis –IF radiation is high enough can cause congenital abnormalities Principle response after that may be malignant disease in childhood
PREVENTING ACCIDENTAL IRRADITATION TO PATIENT FIRST TWO MONTHS, CRITICAL 10 DAY RULE ELECTIVE BOOKING QUESTIONAIRE POSTING
IF A PREGNANT PATIENT MUST BE X-RAYED TIGHT COLLIMATION HIGH KVP SHIELDING REDUCED # OF IMAGES MAKE SURE TO CHECK WITH YOUR SUPERVISOR AND BE AWARE OF THE SITE’S PROTOCOL
GSD GENETICALLY SIGNIFICANT DOSE 20 mrem estimated dose Equivalent dose to the reproductive organs received by every human would cause the same genetic injury as the actual dose received by individual population members
The pregnant radiographer WHICH OF THE FOLLOWING IS (ARE) TRUE? 5 mSv for the period of pregnancy 500 mrem for the period of pregnancy 0.5 mSv per month 0.05 rem per month Two badges TRUE
LET’S PICK UP THE PACE NOW! KEEP THE PATIENTS SAFE!!!
WHAT KIND OF EXPOSURE FACTORS ARE BEST FOR PATIENTS? NAME FACTORS TO KEEP PT DOSE DOWN AS SID increases, what happens to the intensity? What do we adjust and do we increase or decrease this adjustment? Which of the following impacts PT dose? –Inherent filtration? –Added filtration? –SID? –Focal spot size? –Screen speed?
WHAT GIVES HIGHEST CONTRAST BUT INCREASES PATIENT DOSE? COMPTON? CHARACTERITIC? BREMSSTRAHLUNG? PHOTOELECTRIC?
MINIMIZING PATIENT EXPOSUER SHIELDING –Gonadal shielding females reduces gonad dose by 50% –Gonadal shielding males reduces gonad dose by 95% –Flat, shadow shields COLLIMATION –DID YOU KNOW THAT THERE ARE A HIGHER SET OF LEAD SHUTTERS PLACED NEAR THE X-RAY TUBE WINDOW TO ABSORB OFF-FOCUS RADIATION?
FILTRATION –INCREASED FILTRATION (HVL) INCREASES THE AVERAGE BEAM ENERGY –No filtration on a 70 kVp tube (0-70) would produce an average energy of 35 kVp –However, if you filter out the lower energies (30-70 kVp) is 50 kVp –Inherent –Added –_________is required for machines operating at 70 kVp
HVL How many HVL’s are required to reduce the intensity of the beam to less that 15% of its original value A) 2 B)3 C)4 D)5
READING NOMOGRAMS What kind of info do you need? From Appleton and Lange What is the approximate patient ESE from an AP projection of the abd. made at 105 cm, 70 kVp, 300 mA, 0.2 sec (60 mAs)and 2.5 mm AL total filtration
SCATTER STATS Each time the x-ray beam scatters, its intensity at 1 meter from the scattering object is one thousandth of its original intensity or it decreases 1000 times!!!! Or 1/1000 or 0.1%
FLUOROSCOPY PULSED (DF) X-RAY TUBE OPERATES IN RADIOGRAPHIC MODE WHICH MEANS USING TECHNICAL FACTORS THAT ARE USED FOR OVERHEAD EXAMS HOWEVER THE TIME REQUIRED TO REACH THE SELECTED MA AND KV (INTERROGATION TIME) AND THE TIME FOR THE X-RAY TUBE TO BE SWITCHED OFF (EXTINCTION TIME) IS LESS THAN 1 MS THEREFORE IN DR FLUORO A 5 MINUTE STUDY WILL RESULT IN A PATIENT DOSE OF 10 RAD VS 20 RAD FOR A CONVENTIONAL FLUOROSCOPY STUDY
Conventional fluoroscopy mA less than 5 Use of magnification mode increases patient exposure
All types of fluoro Intermittent fluoro Field size Focus to table distance (15” stationary, 12” mobile
THE ENVIRONMENT CONTROLLED AREA OCCUPANCY FACTOR UNCONTROLLED AREA USE FACTOR WORKLOAD Badged personnel Who,what is where Everyone else! % of time primary beam is directed at a particular wall # of x-ray exams per week
Primary barrier 7 feet, 1/16 inch of lead Secondary barrier Extend to ceiling 1/32 inch of lead
Which of these regulations are accurate? DL for eye is 50 mSv? Cumulative whole body is 10mSv x age? Leakage radiation – 100 mR/hr at 2 meters? Lead aprons at 0.25 mm pB equivalent? ESE in 10R/min in fluoro? Exposure cord on portable must be 1 meter long? Pregnant radiographer DL for fetus is 500 mrem for period of pregnancy? The public exposure DL is 100 mrem per year? Bucky slot cover and protective curtain, minimum of 0.5 pB equivalent?
ALARA CARDINAL RULES OF PROTECTION PERSONNEL MONITORS –TLD’S VS OSL VS. FILM BADGES VS DOSIMETERS –Lithium fluoride vs aluminum oxide vs x-ray film vs.gas INVERSE SQUARE LAW WITH EXPOSURE RATE
If a radiographer receives 25 mR standing 3 feet from the source for one hour how much would he receive if he stands 2 feet from the source at 20 minutes? 25mR2 feet squared X3 feet squared 25 mR 4 feet x 9 feet 4 x = 225 X = 56 mR per hour 20 minutes/60 minutes =.33 56 mR x.33 = 18.48 mR at two feet for 20 minutes
SEE YA!!! GOOD LUCK TO ALL THE GRADUATES OF 2012!!!!!