An Overview of Radiation Monitoring An Overview of Radiation Monitoring Programs in RadiologyPrograms in Radiology

Edward Wong Edward Wong

Chief Radiographer, HKSHChief Radiographer, HKSH

16 April 2011

Nuclear Plant LeakageNuclear Plant Leakage

Radiation HorrorsRadiation Horrors

• No Color, no SmellNo Color, no Smell• Deterministic effectsDeterministic effects

– Threshold doseThreshold dose– Redness of skinRedness of skin

• Stochastic effectsStochastic effects– Younger affect mostYounger affect most– Exposure to Exposure to 1 S1 Sievert of rievert of r

adiation is estimated to inadiation is estimated to increase the lifetime risk of crease the lifetime risk of fatalfatal cancer by around 5cancer by around 5%% (Atomic Bomb Study)(Atomic Bomb Study)

Radiation HorrorsRadiation Horrors

• No Color, no SmellNo Color, no Smell• Deterministic effectsDeterministic effects

– Threshold doseThreshold dose– Redness of skinRedness of skin

• Stochastic effectsStochastic effects– Younger affect mostYounger affect most– Exposure to Exposure to 1 S1 Sievert of rievert of r

adiation is estimated to inadiation is estimated to increase the lifetime risk of crease the lifetime risk of fatalfatal cancer by around 5cancer by around 5%% (Atomic Bomb Study)(Atomic Bomb Study)

Radiation HorrorsRadiation Horrors

• No Color, no SmellNo Color, no Smell• Deterministic effectsDeterministic effects

– Threshold doseThreshold dose– Redness of skinRedness of skin

• Stochastic effectsStochastic effects– Younger affect mostYounger affect most– Exposure to Exposure to 1 S1 Sievert of rievert of r

adiation is estimated to inadiation is estimated to increase the lifetime risk of crease the lifetime risk of fatalfatal cancer by around 5cancer by around 5%% (Atomic Bomb Study)(Atomic Bomb Study)

Public AwarenessPublic Awareness

Working 200Working 200hours beforehours beforeCRT monitorCRT monitor

SmokingSmoking7 Cigarettes7 Cigarettes

Eat 130 Eat 130 BananasBananas

Travel 10 Travel 10 hourshours

by Planeby Plane

CXR (0.1mSv)CXR (0.1mSv)

2 months Background 2 months Background Radiation in Hong KongRadiation in Hong Kong

Educational PamphletEducational Pamphlet

Educational PamphletEducational Pamphlet

Accuracy of dose Accuracy of dose information ?information ?

What is the What is the examination dose examination dose level of your level of your institute ?institute ?

Dose MeasurementDose Measurement

QuantityQuantity UnitUnit DeterminationDetermination

ExposureExposure Coulombs (C) Coulombs (C) /Kg/Kg

Measure the amount of ionization produced in airMeasure the amount of ionization produced in air

Absorbed Absorbed DoseDose

Gray (Gy) or Gray (Gy) or J/KgJ/Kg

Measure the radiation energy absorbed by the patientMeasure the radiation energy absorbed by the patient

Equivalent Equivalent DoseDose

Sievert (Sv)Sievert (Sv) Multiply Multiply Absorbed DoseAbsorbed Dose by a quality factor (QF) to show by a quality factor (QF) to show harmful effects, e.g.harmful effects, e.g.

X-ray & Gamma: QF=1; Alpha particle: QF=20X-ray & Gamma: QF=1; Alpha particle: QF=20

Effective Effective DoseDose

SvSv Multiply Multiply Equivalent DoseEquivalent Dose by a tissue weighting (TW) by a tissue weighting (TW) factor, i.e. Colon: TW=0.12; Skin: TW=0.01; Whole factor, i.e. Colon: TW=0.12; Skin: TW=0.01; Whole Body: TW=1 (ICRP 2007)Body: TW=1 (ICRP 2007)

Example: 100mSv to skin = Effective dose of 1mSvExample: 100mSv to skin = Effective dose of 1mSv

Device for measurementDevice for measurement

TLD-100 TLD-100 chips chips (Harshaw)(Harshaw)

Film Film badge badge TLDTLD DAP and DAP and

printerprinter

Various detectors Various detectors and Phantomsand Phantoms

Dose Area Product MeterDose Area Product Meter

• Reading includes SID Reading includes SID variationvariation

• Reading includes Reading includes Collimation factorsCollimation factors

• DAP do not measure DAP do not measure backscatterbackscatter

• DAP do not measure DAP do not measure wedge or added filterswedge or added filters

• mGy/cm2mGy/cm2

Monte Carlo simulationsMonte Carlo simulations

• The assessment of conversion factors bThe assessment of conversion factors began more than 30 years agoegan more than 30 years ago

• UUse tissue-equivalent plastic body phanse tissue-equivalent plastic body phantoms containing organs into which dositoms containing organs into which dosimeters meters areare inserted inserted and and Monte Carlo si Monte Carlo simulations are appliedmulations are applied

• CCommon available standard includes aommon available standard includes an adult with a body mass of 70 kg; childn adult with a body mass of 70 kg; children aged 15, 10, 5ren aged 15, 10, 5,, 1 year and newborn 1 year and newbornss

• Effective dose: can’t measure routinelyEffective dose: can’t measure routinely• Entrance Skin Dose is commonly usedEntrance Skin Dose is commonly used

Effective Dose CalculationEffective Dose Calculation

Verdun F R et al. Radiographics 2008;28:1807-1816Verdun F R et al. Radiographics 2008;28:1807-1816

TThe geometry of patient exposure is lhe geometry of patient exposure is less predictable and varies during the ess predictable and varies during the procedureprocedure

X-rayX-ray

FluoroFluoro

CTCT

The fundamental radiation dose parameter in CThe fundamental radiation dose parameter in CT is the CT dose index (CTDI T is the CT dose index (CTDI & & CTDIvol).CTDIvol). ToTo aassess patient dose exposure after scanning a cssess patient dose exposure after scanning a certain distanceertain distance use dose-length product (CTDIuse dose-length product (CTDIvol × scan lengthvol × scan length))

Use ESD & DAP to calculate the Use ESD & DAP to calculate the Effective DoseEffective Dose

HartD, Jones DG, Wall BF. Estimation of effective dose in diagnostic radiology from entrance dose and doHartD, Jones DG, Wall BF. Estimation of effective dose in diagnostic radiology from entrance dose and do

se-area product measurement (NRPB-R262). Chilton, England: se-area product measurement (NRPB-R262). Chilton, England: NRPBNRPB, 1994., 1994.

Dose Reference Levels (DRL)Dose Reference Levels (DRL)

• Introduced by ICRPIntroduced by ICRP

• Dose level for typical exams for group of Dose level for typical exams for group of standard-sized patientsstandard-sized patients

• DRL are typically set at DRL are typically set at

the 3rd quartile of dosethe 3rd quartile of dose

distribution from a distribution from a

surveysurvey

DRL for monitoringDRL for monitoring

Calculation of Entrance Skin Dose (ESD) for SuCalculation of Entrance Skin Dose (ESD) for Supine and Erect Abdomenpine and Erect Abdomen in in DDigital Radiographigital Radiography for HA hospitalsy for HA hospitals

ESD = (DAP*BSF/FieldSize)*(SID/FSD)^2ESD = (DAP*BSF/FieldSize)*(SID/FSD)^2

FSD, focus-to-skin distance = SID - 25 cmFSD, focus-to-skin distance = SID - 25 cm

BSF, backscatter factor estimated fromBSF, backscatter factor estimated from

NRPB SR262 (e.g. 80kVp = 1.458)NRPB SR262 (e.g. 80kVp = 1.458)

Information from DICOM HeaderInformation from DICOM Header

kVp = 110kVp = 110

Protocol = ChestProtocol = Chest

SID = 1800mmSID = 1800mm

FSD = 1750mmFSD = 1750mm

FOV (collimation) = FOV (collimation) =

35.1cm x 37.1cm35.1cm x 37.1cm

mAs = 3.376mAs = 3.376

DAP = 1.5766 mGy/cm2DAP = 1.5766 mGy/cm2

Position = PAPosition = PA

Mapping to PACS Mapping to PACS database is requireddatabase is required

Results of DRLResults of DRL

A B C D E F G

Hospitals

Usage of DRLComplied by ACR for Appropriateness Criteria

CR vs DRCR vs DR

• CR: no kVp and mAs CR: no kVp and mAs datadata

• Vendors have their own Vendors have their own calculation of Exposure calculation of Exposure Index (EI) which give Index (EI) which give feedback about detector feedback about detector dose leveldose level

• AAPM try to standardize AAPM try to standardize the EIthe EI

• Complicated by Complicated by collimation detection and collimation detection and post processingpost processing

Freeware for CT dose Freeware for CT dose

• Image ServerImage Server

• PHP/mySQLPHP/mySQL

• OCROCR

Move dose info to DatabaseMove dose info to Database

• Difficult to handle more than one scannerDifficult to handle more than one scanner

• Need mappingNeed mapping ? ?

Fluoroscopy ?Fluoroscopy ?

DICOM Structure Report DICOM Structure Report & IHE enhancement& IHE enhancement

• Store Dose InformationStore Dose Information - Similar to - Similar to Images StoredImages Stored

• Query Dose InformationQuery Dose Information

• Retrieve Dose InformationRetrieve Dose Information

• Submit Dose ReportSubmit Dose Report

Dedicated Dose MonitoringDedicated Dose Monitoring

Reports and AlertsReports and AlertsLA Law: 5 Gy collective dose over 18 LA Law: 5 Gy collective dose over 18 months or 4 Gy single examination !!!months or 4 Gy single examination !!!

IAEA Smart Card Project 2009IAEA Smart Card Project 2009

• Tracking life time dose record for patientTracking life time dose record for patient

• eHR for recording or Radiation PassporteHR for recording or Radiation Passport

• Access anywhere by digital signatureAccess anywhere by digital signature

• Data for monitoring public radiation levelData for monitoring public radiation level

• Refine existing standard on dosimetryRefine existing standard on dosimetry

• Enhancement in DICOM & IHE-REM for Enhancement in DICOM & IHE-REM for dose report and dose information dose report and dose information communicationcommunication

ThanksThanks

www.pacs.hkwww.pacs.hkwongthe@gmail.com