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