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Radiation ProtectionRadiation Protection
Review of Units of Review of Units of MeasurementsMeasurements
Protection for Patient and Protection for Patient and PersonnelPersonnel
Review of RadiobiologyReview of Radiobiology
Follows the ARRT Content Follows the ARRT Content SpecificationsSpecifications
Sources of Radiation Sources of Radiation ExposureExposure
Natural or background Natural or background - ground, - ground, cosmic, cosmic, naturally naturally occurring isotopes, etc.occurring isotopes, etc.
Artificial or man-made - Artificial or man-made - Medical Medical and and dental largest contributor to population dosedental largest contributor to population dose
Units of MeasurementUnits of Measurement - - Know traditional andKnow traditional and Standard International Standard International UnitsUnits
Roentgen (R) - Roentgen (R) - traditional unit of traditional unit of exposureexposure in air - in air - equipment equipment related [x and gamma rays] related [x and gamma rays]
Coulomb/Kg or C/KgCoulomb/Kg or C/Kg
rad (r) rad (r) - traditional unit of absorbed - traditional unit of absorbed dosedose [all] [all]
• Gray (Gy)Gray (Gy) rem - rem - traditional unit of dose equivalent [x, beta, traditional unit of dose equivalent [x, beta,
gamma]gamma]– Seivert (Sv)Seivert (Sv)
Curie (Ci) Curie (Ci) - - measure ofmeasure of radioactivityradioactivity • Becquerel (Bq) = in Nuc MedBecquerel (Bq) = in Nuc Med
Detection MethodsDetection MethodsPersonnelPersonnel Field Field InstrumentsInstruments
Film Badges - monthFilm Badges - month• photographic filmphotographic film
TLD - 3 monthsTLD - 3 months• Sensitive to 5 mremSensitive to 5 mrem• ExpensiveExpensive
Ionization chamberIonization chamber• pocket dosimeterpocket dosimeter• drifts / not accuratedrifts / not accurate• Larger one for NM or Larger one for NM or
more industrialmore industrial
Ionization CounterIonization Counter• Cutie Pie,Geiger Cutie Pie,Geiger
CounterCounter• spills, more spills, more
industrialindustrial
Scintillation Scintillation detectordetector• more technical usemore technical use• used in CT,NMused in CT,NM
OSLOSL
Aluminum OxideAluminum Oxide Laser beam releases lightLaser beam releases light Sensitive to exposures as low as 1 Sensitive to exposures as low as 1
mremmrem 3 months at a time3 months at a time Can be reanalizedCan be reanalized
Monitoring AgenciesMonitoring Agencies NCRP -NCRP -National Council on Rad ProtectionNational Council on Rad Protection
– dose limitations controldose limitations control
DRH - Devices for Radiological HealthDRH - Devices for Radiological Health– radiation control (more equipment related)radiation control (more equipment related)
NRC NRC - Nuclear Regulatory Commission - Nuclear Regulatory Commission - - radiation protection standards radiation protection standards (formerly- Atomic Energy Comm)(formerly- Atomic Energy Comm)
Maryland State Dept. Health & HygieneMaryland State Dept. Health & Hygiene EPA - Environmental Protection AgencyEPA - Environmental Protection Agency
– more industrial application related mattersmore industrial application related matters
Recommendations for Recommendations for DoseDose
ALARA - As Low As Reasonably Achievable for patient ALARA - As Low As Reasonably Achievable for patient and occupational workerand occupational worker
Cumulative Dose Limit for Occupational Worker - Cumulative Dose Limit for Occupational Worker - simply your age x 1 remsimply your age x 1 rem• ie. 47yo male RT, 47 remie. 47yo male RT, 47 rem
Embyro or fetus -- 50mrem/month or 500 mrem totalEmbyro or fetus -- 50mrem/month or 500 mrem total
Member of public frequently, exposed 100mremMember of public frequently, exposed 100mrem
Interactions with MatterInteractions with Matter Coherent ( Classicial or Thompson) Coherent ( Classicial or Thompson)
scattering: < 30kVpscattering: < 30kVp Photoelectric Effect 30-150 kVpPhotoelectric Effect 30-150 kVp Compton’s Scatter: 30-150 kVpCompton’s Scatter: 30-150 kVp
• ie. 70kVp 40% PE and 60% Comptonie. 70kVp 40% PE and 60% Compton• vs 100kVp 10% PE and 90 % Comptonvs 100kVp 10% PE and 90 % Compton
Pair Production and Photodisintegration : Pair Production and Photodisintegration : MeV as in Rad TherapyMeV as in Rad Therapy
Estimated Patient DosesEstimated Patient Doses
Skin - TLD 15, 000mrem and Skin - TLD 15, 000mrem and extremities 30,000 mremextremities 30,000 mrem
Gonad -- genetic responses at Gonad -- genetic responses at 20rads/yr20rads/yr
Bone Marrow (mean) - rad induced Bone Marrow (mean) - rad induced leukemia 100 rad/yrleukemia 100 rad/yr
Gonadal and bone doses are estimatesGonadal and bone doses are estimates!!
Estimated DosesEstimated Doses
Fluoroscopic are harder to measureFluoroscopic are harder to measure• 2rad/mA/minute2rad/mA/minute• remember patient becomes the hazard since the remember patient becomes the hazard since the
scatter is what gets the radiographerscatter is what gets the radiographer
Exams with higher patient doses are:Exams with higher patient doses are:• FluoroFluoro• AngioAngio• PortablesPortables• General - around pelvic region, hip femur, General - around pelvic region, hip femur,
lumbar, coccyx, sacrumlumbar, coccyx, sacrum
Cardinal PrinciplesCardinal Principles
Time : Time : time, time, dose dose OROR time, time, dosedose
Distance: Distance: distance, distance, dose dose OR OR if you if you conversely conversely distance, distance, dose dose (don’t forget the (don’t forget the inverse square law or direct square law)inverse square law or direct square law)
Shielding: Shielding: reduces dose as much as reduces dose as much as 95% in male patients95% in male patients
Patient ProtectionPatient Protection
Cardinal PrinciplesCardinal Principles• time, distance, shieldingtime, distance, shielding
Exposure FactorsExposure Factors• kVp, mA, time, distancekVp, mA, time, distance• directly relateddirectly related kVp - kVp - interactions interactions time - time - dose dose
– fluoro time -keep it shortfluoro time -keep it short
mA and mA and (fast) time(fast) time
Filtration - inherentFiltration - inherent• 0.5mm al <50kVp0.5mm al <50kVp• 1.5mm al 50-70kVp1.5mm al 50-70kVp• 2.5mm al >70kVp2.5mm al >70kVp
Film Screen ComboFilm Screen Combo Beam limitationBeam limitation
• PBL - PBL - automatic collimationautomatic collimation
• ConesCones• CylindersCylinders• aperture diaphragmsaperture diaphragms field, scatter, dosefield, scatter, dose
Avoid RepeatsAvoid Repeats• techniques chartstechniques charts• good communicationgood communication• restraining devicesrestraining devices• good QA programgood QA program
Patient ProtectionPatient Protection - - continuedcontinued Shielding - Shielding - not not
< 0.25mm Pb< 0.25mm Pb
• long bones in pedslong bones in peds• all eyesall eyes• gonadal - gonadal - 5cm primary5cm primary
– flat rubber lead stripsflat rubber lead strips– shadow shieldshadow shield– shaped or cupshaped or cup– eye shieldseye shields
• If patient holds If patient holds cassette, Pb glove cassette, Pb glove needs to be 0.5 mm to needs to be 0.5 mm to protect handprotect hand
Air Gap techniqueAir Gap technique High Dose toHigh Dose to GonadsGonads
• hiphip upper femur upper femur
• pelvispelvis lumbar lumbar
• lumbo-scarallumbo-scaral
• abdomenabdomen
• sacrumsacrum coccyx coccyx
• S-I JointsS-I Joints
• BE, IVP, Cysto, HysteroBE, IVP, Cysto, Hystero
Personnel ProtectionPersonnel Protection
Cardinal PrinciplesCardinal Principles• Time, Distance, Time, Distance,
ShieldingShielding Protective wearProtective wear
• Pb aprons 0.5mm =Pb aprons 0.5mm =• Pb gloves 0.25mm =Pb gloves 0.25mm =• thyroid - thyroid - dose 10% & dose 10% &
6mrad per exam6mrad per exam
• Pb glasses 0.75mmPb glasses 0.75mm dose 98%dose 98%
• Pb sterile glovesPb sterile gloves
Barriers - 7” highBarriers - 7” high• primary 1/16th primary 1/16th
inchinch• secondary 1/32 secondary 1/32
inchinch• Pb glass portPb glass port• mobile in ORmobile in OR
Mobile exposure Mobile exposure cord length cord length - - no no less 6’less 6’
Personnel ProtectionPersonnel Protection ContinuedContinued
Never hold Never hold Patients - Patients - use use immobilization devicesimmobilization devices
Wear monitoring Wear monitoring devicesdevices• film badgefilm badge• TLDTLD• Pocket dosimeterPocket dosimeter
Fluoro equipment - Fluoro equipment - apron on tower, bucky slot apron on tower, bucky slot cover, fluoro timercover, fluoro timer
Clear room when Clear room when doing portables or doing portables or provide with Pb provide with Pb apronapron
Stand 2 m from Stand 2 m from tabletable
PregnancyPregnancy
RadiographerRadiographer• self disclosure self disclosure
voluntaryvoluntary• fetus 50mrem per fetus 50mrem per
month or 500 mrem month or 500 mrem or 5mSv over termor 5mSv over term
• Baby badge at Baby badge at waistwaist
• 0.5mm Pb aprons 0.5mm Pb aprons are 88% effective > are 88% effective > 70 kVp70 kVp
PatientPatient• ask about LMPask about LMP• ALARAALARA• double shield or double shield or
limit exam viewslimit exam views• 10 day rule for 10 day rule for
high dose examshigh dose exams
Rad Protection - Rad Protection - EquipmentEquipment
General RadiographicGeneral Radiographic• Control panel: light, meters and soundControl panel: light, meters and sound• SID: within SID: within 2% variance 2% variance• PBL: within PBL: within 2% of SID 2% of SID• Beam alignmentBeam alignment• Filtration: 2.5mm Al equivalent totalFiltration: 2.5mm Al equivalent total• Reproducibility: Reproducibility: output = , not to exceed 5%output = , not to exceed 5%
• Linearity: Linearity: intensity = across mA stations, not be intensity = across mA stations, not be exceed 10%exceed 10%
• Personnel shield: short cords so exposures are made Personnel shield: short cords so exposures are made behind 7” barriersbehind 7” barriers
Rad ProtectionRad Protection - - EquipmentEquipment
Fluoro and MobileFluoro and Mobile Mobile C-ArmMobile C-Arm: : not < 12” (30cm) source to tabletop not < 12” (30cm) source to tabletop
distancedistance
Stationary Fluoro:Stationary Fluoro:not < 15” (38cm) source to tabletop not < 15” (38cm) source to tabletop
distancedistance Primary Barrier: Primary Barrier: IA assembly 2mm Pb equivalent when IA assembly 2mm Pb equivalent when
>125kVp (usually 80-120 kVp fluoro)>125kVp (usually 80-120 kVp fluoro)
Filtration: Filtration: 2.5mmAl total just in overhead tube; <100mR/Hr 2.5mmAl total just in overhead tube; <100mR/Hr leakage at 1 meterleakage at 1 meter
PBL on Fluoro tower: PBL on Fluoro tower: borders on monitor when IA is 14” borders on monitor when IA is 14”
from tabletopfrom tabletop Exposure switch:Exposure switch: “Dead man” - intermittent “Dead man” - intermittent dose dose
Rad Protection - Rad Protection - EquipmentEquipment
Fluoro and MobileFluoro and Mobile Bucky Slot Cover: Bucky Slot Cover: 5cm wide at gonadal level and 0.25mm 5cm wide at gonadal level and 0.25mm
Pb thickPb thick
Protective Apron on Tower: Protective Apron on Tower: 0.150.15- - 0.25mm Pb between 0.25mm Pb between patient & operatorpatient & operator
Cumulative Timer for Fluoro:Cumulative Timer for Fluoro: 5 min/audible 5 min/audible
X-Ray Intensity: X-Ray Intensity: should not >2.1R/min at tabletop per mA should not >2.1R/min at tabletop per mA at 80 kVpat 80 kVp
Dose Rate: Dose Rate: mustmust not > 10R/min maximum, should not 5 not > 10R/min maximum, should not 5
Front loaded cassette vs back load: Front loaded cassette vs back load: front less dosefront less dose
Spot cassette vs spot film camera -- dose to patient 3x Spot cassette vs spot film camera -- dose to patient 3x more for cassette over cameramore for cassette over camera
RADIOBIOLOGYRADIOBIOLOGY
In addition to the technical In addition to the technical side, we must understand the side, we must understand the biological effects!biological effects!
Characteristics of Characteristics of RadiationRadiation
PhysicalPhysical• LET - LET - efficiency of radiation to produce excitation efficiency of radiation to produce excitation
and ionization ( energy deposit per unit path length)and ionization ( energy deposit per unit path length)
• LET of dx is 3 keV/LET of dx is 3 keV/mm
• RBE - Relative Biological EffectivenessRBE - Relative Biological Effectiveness
Biological AspectsBiological Aspects
Review the mitosis and meiosis Review the mitosis and meiosis cyclescycles
The most sensitive time for DNS is The most sensitive time for DNS is G2 and rest of mitotic stages G2 and rest of mitotic stages (least (least during G1 and Synthesis)during G1 and Synthesis)
Keep in mind that in meiosis, DNS replicates Keep in mind that in meiosis, DNS replicates only onceonly once
What about other factor affecting What about other factor affecting cellular response?cellular response?
Laws of SensitivityLaws of Sensitivity
High mitotic activity -- High mitotic activity -- more sensitivemore sensitive
Cell differentiation -- Cell differentiation -- less, more sensitiveless, more sensitive
Long dividing future -- Long dividing future -- more sensitivemore sensitive• All these Bergonie and TribondeauAll these Bergonie and Tribondeau
Biological StressBiological Stress Pre/post irradiation conditions Pre/post irradiation conditions Chemicals -- enhancers, protectorsChemicals -- enhancers, protectors
• Ancel and Vitemberger -- more environment relatedAncel and Vitemberger -- more environment related
Effects---Effects---
Direct - photon strikes DNA --Direct - photon strikes DNA --breaks in breaks in ladder either rungs or side railsladder either rungs or side rails
Indirect - photon strikes water -- Indirect - photon strikes water -- most most abundant so most likely to happen more frequentlyabundant so most likely to happen more frequently
Target Theory -- variations, but striking a critical Target Theory -- variations, but striking a critical DNA area where lethality occurs immediately or DNA area where lethality occurs immediately or may take two hits to achieve deathmay take two hits to achieve death
Cell survival curves - curve representing the dose Cell survival curves - curve representing the dose and proportion of cells survivingand proportion of cells surviving
Mean Survival CurvesMean Survival Curves
Relationship between the dose and Relationship between the dose and number of cells that survivenumber of cells that survive
Lethal DoseLethal Dose• human LD 50/60 -- 350 radhuman LD 50/60 -- 350 rad
– previously 50/30 - Chernobyl changed previously 50/30 - Chernobyl changed figuresfigures
Dose Response Dose Response RelationshipsRelationships
Linear, non-linear Linear, non-linear
Threshold or non-thresholdThreshold or non-threshold (non-stochastic)(non-stochastic) (stochastic, random)(stochastic, random)
We practice by Linear, non-thresholdWe practice by Linear, non-threshold
Cellular ResponsesCellular Responses
Interphase deathInterphase death Division DelayDivision Delay Reproductive failureReproductive failure
Stages of ResponseStages of ResponseDose DependentDose Dependent
Prodromal -- NVDProdromal -- NVD LatentLatent ManifestManifest
• hematologic --hematologic --dose between 100-1000dose between 100-1000– 200-600/200-1000200-600/200-1000
• GI syndrome - GI syndrome - dose between 1000-5000dose between 1000-5000– 600-1000 600-1000
• CNS - CNS - dose > 5000dose > 5000
Recovery or DeathRecovery or Death
Radiation Reduced Radiation Reduced MalignancyMalignancy
Historical populationsHistorical populations Dose relatedDose related Risks associatedRisks associated 20% population USA will die of Ca20% population USA will die of Ca
• how do you tell if rad caused?how do you tell if rad caused? Children? Leukemia is commonChildren? Leukemia is common
In Utero -- Fetal IrradiationIn Utero -- Fetal Irradiation neonatal death - neonatal death - 2-3 week of gestation2-3 week of gestation malformations malformations growth stunting growth stunting congenital defects - congenital defects - functional defects after functional defects after
week 20week 20 cancer inductioncancer induction
Week 4-11 severe abnormalities, especially CNS and Week 4-11 severe abnormalities, especially CNS and skeletal, while 11- 16 mental retardation & microcephalyskeletal, while 11- 16 mental retardation & microcephaly
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