biological response and radiation safety practices
TRANSCRIPT
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Biological response and Biological response and radiation safety practicesradiation safety practices
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BIOLOGICAL RESPONSE BIOLOGICAL RESPONSE AND RADIATION SAFETY AND RADIATION SAFETY PRACTICESPRACTICES
X-ray interactions in the patientRadiation exposuresRadiation measurement unitsMethods of detecting radiationBiological effects of radiation exposureAcute Radiation SyndromeSub-syndromes-hemopoietic, GI, CNSRadiation ProtectionALARA
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TerminologyTerminology
NCRP R, roentgen,
coulombs/kg rad rem Gray Sievert Curie, Becquerel Effective does Quality factor Threshold ALARA
OSL Film badge TLD Pocket dosimeter Field survey instruments Geiger-Müller counter Cutie pie Somatic effect Genetic effect Acute Radiation
Syndrome(ARS)
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Radiation ExposureRadiation Exposure
Exposure Measurements Methods of Measuring
Units of measure International unitsBritish UnitsUnit conversions
Film badgeOSLTLDPocket dosimeterField Survey
Instruments
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What happens to our x-What happens to our x-ray?ray?
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PATIENT INTERACTIONSPATIENT INTERACTIONS
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Classical (Coherent) Scattering
Classical (Coherent) Scattering
Excitation of the total complement of atomic electrons occurs as a result of interaction with the incident photon
No ionization takes place
Electrons in shells “vibrate”
Small heat is released The photon is
scattered in different directions
Energies below 10kV
Patient Interactions
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COMPTON SCATTERING
1. Outer shell electron in body
2. Interacts with x-ray photon from the tube
3. Moderate energy electron
Patient Interactions
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Patient Interactions
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photoelectron
Incoming photon interacts with inner shell electron. The “knocked-out” electron is called a photoelectron. The energy of the incoming photon is absorbed.
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Patient Interactions
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Patient Interactions
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X-rays interact with Patient’s X-rays interact with Patient’s body to cause changes in cells. body to cause changes in cells.
Interaction in Interaction in the body beginthe body beginat the atomic at the atomic
levellevel
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Patient Interactions:Patient Interactions:Interactions of X-rays with matterInteractions of X-rays with matter
1. No interaction: X-ray passes completely and get to image receptor
2. Complete absorption: no x-rays get to image receptor
3. Partial absorption with scatter-some x-rays get to image receptor but some get scattered
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X-ray photons can change X-ray photons can change cellscells
Patient InteractionsPatient Interactions
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RADIATION RADIATION EXPOSURESEXPOSURES
To Keep Ourselves Safe:◦Measure exposure◦Determine levels at which damage occurs
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Measuring ExposureMeasuring ExposureUnits of Measure
◦ International Units C/kg3 Gray Sieverts Becquerel
◦ British Units Roentgen Rad Rem Curie
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Exposure: Measured in airExposure: Measured in air
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Absorbed DoseAbsorbed Dose
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Radiation EquivalentRadiation Equivalent
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RADS REMSRADS REMS
rads
Grays
Patient absorbed dose
rems
Sieverts
Employee(technologists) =
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In diagnostic radiology:
1 roentgen = 1 rad = 1 rem
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Comparison of UnitsComparison of UnitsExposure R C/kg 1R=2.58x
10-4 C/kg
Absorbed Dose
rad Gray 1rad=.01Gray1Gray=100rad
Dose Equivalent
rem Sievert 1rem=.01Sv1Sv=100rem
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In diagnostic radiology:
1 roentgen = 1 rad = 1 rem
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Unit Conversions:Unit Conversions:A normal chest x-ray exposes the patient to approximately 15mR. How many roentgens is that?
A CT examination results in a patient dose of 4000 mrad. How many gray is that?
Annual exposure dose for a technologist is 5 rems. What is that in Sieverts? mSv?
You Receive ~620 millirem per year. According to stats from the US Nuclear Regulatory Commission average yearly exposure is roughly 620 millirem--half of which comes from natural sources (cosmic radiation, from the soil, radon, etc) and half comes from manmade sources. Note that geography can play a big part in that. In Colorado, for example, natural radiation exposure can be 1000 mrem per year due to higher altitude.What is your exposure in mSv?What is your exposure in mSv if you live in Colorado?
A patient left a head of lettuce in the x-ray exam room. The lettuce received a dose of 10mrad. How many Gr is that?
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Permissible Permissible Occupational DoseOccupational Dose
Annual dose : 5 Rem/year 50mSv/year 5000 mrem
Cumulative Dose 1 rem x age or 10mSv x
age
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PUBLIC EXPOSUREPUBLIC EXPOSURE NON MEDICAL EXPOSURENON MEDICAL EXPOSURE
10 % of Occupational exposure0.5 rad or 500 mrad or 5mGray
Under age 18 and Students 0.1 rem
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Pregnancy & Embryo Pregnancy & Embryo
Mother occupational worker◦ 5 rem
Baby ◦ .5 rem/ year◦ .05 rem/month
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Methods of MeasuringMethods of Measuring
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Summary of Monitoring Summary of Monitoring DevicesDevices
monitoring device sensing material readability advantages disadvantages common usage
Film Badges filmchanged every month,
reading comes in a monthly report from company
least expensivenot instant reading, prone
to other factors such as heat, moisture, pressure
technologist, radiation personnel
Optically Stimulated Luminescence
Device
aluminum oxide crystals
changed 1-2 months, reading comes in a report from
company
more sensitve than film, not prone to damge from heat,
moisture, pressurenot reading immediately
technologist, radiation personnel
Thermolumuniescent Dosimeter
lithium floride crystals
can be worn up to 3 monthsonce crystals have been heated, can be re-used
no permanent recordtechnologist, radiation
personnel
Pocket Dosimeterionizes air in
chamberimmediate reading immediate reading
false readings common, no permanent record
technologist, radiation personnel
Field Survey Instruments
measures ionizations in air chamber
immediate readingnot used for personal
monitoringnot used for personal
monitoring
measures xray output of machines and areas known to
contain radioactivity
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Exam 2 Next Week:
ALARA- As Low As Reasonably Achievable