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An Overview of Radiation Monitoring Programs in Radiology Edward Wong Chief Radiographer, HKSH 16 April 2011.

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Presentation on theme: "An Overview of Radiation Monitoring Programs in Radiology Edward Wong Chief Radiographer, HKSH 16 April 2011."— Presentation transcript:

1 An Overview of Radiation Monitoring Programs in Radiology Edward Wong Chief Radiographer, HKSH 16 April 2011

2 Nuclear Plant Leakage

3 Radiation Horrors No Color, no SmellNo Color, no Smell Deterministic effectsDeterministic effects –Threshold dose –Redness of skin Stochastic effectsStochastic effects –Younger affect most –Exposure to 1 Sievert of radiation is estimated to increase the lifetime risk of fatal cancer by around 5% (Atomic Bomb Study)

4 Radiation Horrors No Color, no SmellNo Color, no Smell Deterministic effectsDeterministic effects –Threshold dose –Redness of skin Stochastic effectsStochastic effects –Younger affect most –Exposure to 1 Sievert of radiation is estimated to increase the lifetime risk of fatal cancer by around 5% (Atomic Bomb Study)

5 Radiation Horrors No Color, no SmellNo Color, no Smell Deterministic effectsDeterministic effects –Threshold dose –Redness of skin Stochastic effectsStochastic effects –Younger affect most –Exposure to 1 Sievert of radiation is estimated to increase the lifetime risk of fatal cancer by around 5% (Atomic Bomb Study)

6 Public Awareness Working 200 hours before CRT monitor Travel 10 hours by Plane Smoking 7 Cigarettes Eat 130 Bananas CXR (0.1mSv) 2 months Background Radiation in Hong Kong

7 Educational Pamphlet

8 Accuracy of dose information ? What is the examination dose level of your institute ?

9 Dose Measurement QuantityUnit Determination Determination Exposure Coulombs (C) /Kg Measure the amount of ionization produced in air Absorbed Dose Gray (Gy) or J/Kg Measure the radiation energy absorbed by the patient Equivalent Dose Sievert (Sv) Multiply Absorbed Dose by a quality factor (QF) to show harmful effects, e.g. X-ray & Gamma: QF=1; Alpha particle: QF=20 Effective Dose Sv Multiply Equivalent Dose by a tissue weighting (TW) factor, i.e. Colon: TW=0.12; Skin: TW=0.01; Whole Body: TW=1 (ICRP 2007) Example: 100mSv to skin = Effective dose of 1mSv

10 Device for measurement TLD-100 chips (Harshaw) Film badge TLD DAP and printer Various detectors and Phantoms

11 Dose Area Product Meter Reading includes SID variationReading includes SID variation Reading includes Collimation factorsReading includes Collimation factors DAP do not measure backscatterDAP do not measure backscatter DAP do not measure wedge or added filtersDAP do not measure wedge or added filters mGy/cm2mGy/cm2

12 Monte Carlo simulations The assessment of conversion factors began more than 30 years agoThe assessment of conversion factors began more than 30 years ago Use tissue-equivalent plastic body phantoms containing organs into which dosimeters are inserted and Monte Carlo simulations are appliedUse tissue-equivalent plastic body phantoms containing organs into which dosimeters are inserted and Monte Carlo simulations are applied Common available standard includes an adult with a body mass of 70 kg; children aged 15, 10, 5, 1 year and newbornsCommon available standard includes an adult with a body mass of 70 kg; children aged 15, 10, 5, 1 year and newborns Effective dose: can’t measure routinelyEffective dose: can’t measure routinely Entrance Skin Dose is commonly usedEntrance Skin Dose is commonly used

13 Effective Dose Calculation Verdun F R et al. Radiographics 2008;28: The geometry of patient exposure is less predictable and varies during the procedure X-rayFluoroCT The fundamental radiation dose parameter in CT is the CT dose index (CTDI & CTDIvol). To assess patient dose exposure after scanning a certain distance use dose-length product (CTDIvol × scan length) The fundamental radiation dose parameter in CT is the CT dose index (CTDI & CTDIvol). To assess patient dose exposure after scanning a certain distance use dose-length product (CTDIvol × scan length)

14 Use ESD & DAP to calculate the Effective Dose HartD, Jones DG, Wall BF. Estimation of effective dose in diagnostic radiology from entrance dose and dose-area product measurement (NRPB-R262). Chilton, England: NRPB, 1994.

15 Dose Reference Levels (DRL) Introduced by ICRPIntroduced by ICRP Dose level for typical exams for group of standard-sized patientsDose level for typical exams for group of standard-sized patients DRL are typically set atDRL are typically set at the 3rd quartile of dose distribution from a survey

16 DRL for monitoring Calculation of Entrance Skin Dose (ESD) for Supine and Erect Abdomen in Digital Radiography for HA hospitals ESD = (DAP*BSF/FieldSize)*(SID/FSD)^2 FSD, focus-to-skin distance = SID - 25 cm BSF, backscatter factor estimated from NRPB SR262 (e.g. 80kVp = 1.458)

17 Information from DICOM Header kVp = 110 Protocol = Chest SID = 1800mm FSD = 1750mm FOV (collimation) = 35.1cm x 37.1cm mAs = DAP = mGy/cm2 Position = PA Mapping to PACS database is required

18 Results of DRL A B C D E F G Hospitals

19 Usage of DRL Complied by ACR for Appropriateness Criteria

20 CR vs DR CR: no kVp and mAs dataCR: no kVp and mAs data Vendors have their own calculation of Exposure Index (EI) which give feedback about detector dose levelVendors have their own calculation of Exposure Index (EI) which give feedback about detector dose level AAPM try to standardize the EIAAPM try to standardize the EI Complicated by collimation detection and post processingComplicated by collimation detection and post processing

21 Freeware for CT dose Image ServerImage Server PHP/mySQLPHP/mySQL OCROCR

22 Move dose info to Database Difficult to handle more than one scannerDifficult to handle more than one scanner Need mapping ?Need mapping ?

23 Fluoroscopy ?

24 DICOM Structure Report & IHE enhancement Store Dose Information - Similar to Images StoredStore Dose Information - Similar to Images Stored Query Dose InformationQuery Dose Information Retrieve Dose InformationRetrieve Dose Information Submit Dose ReportSubmit Dose Report

25 Dedicated Dose Monitoring

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

27 IAEA 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 dose report and dose information communicationEnhancement in DICOM & IHE-REM for dose report and dose information communication

28 Thanks Thanks


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