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 Smell Deterministic effects
Threshold dose
Redness of skin
Stochastic 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)
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4. Radiation Horrors No Color, no Smell Deterministic effects
Threshold dose
Redness of skin
Stochastic 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)
CT perfusion Prolonged fluoroscopy sensitivity is proportional to dividing cells 50mSv starting

5. Radiation Horrors No Color, no Smell Deterministic effects
Threshold dose
Redness of skin
Stochastic 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. 2 months Background Radiation in Hong Kong
Public Awareness
CXR (0.1mSv)
2 months Background Radiation in Hong Kong

7. Educational Pamphlet

8. Educational Pamphlet Accuracy of dose information ?
Royal observatory
What is the examination dose level of your institute ?

9. Dose Measurement Quantity Unit Determination Exposure Absorbed Dose
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
Recap memory different radiation has different detrimental effects

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

11. Dose Area Product Meter
Reading includes SID variation
Reading includes Collimation factors
DAP do not measure backscatter
DAP do not measure wedge or added filters
mGy/cm2

12. Monte Carlo simulations
The 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 applied
Common 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 routinely
Entrance Skin Dose is commonly used
Too hard to be accurate, too many factors

13. Effective Dose Calculation
The geometry of patient exposure is less predictable and varies during the procedure
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)
X-ray
Fluoro CT
Verdun F R et al. Radiographics 2008;28:

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 ICRP
Dose level for typical exams for group of standard-sized patients
DRL are typically set at
the 3rd quartile of dose
distribution from a
survey

16. DRL for monitoring ESD = (DAP*BSF/FieldSize)*(SID/FSD)^2
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 = 3.376
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 data
Vendors have their own calculation of Exposure Index (EI) which give feedback about detector dose level
AAPM try to standardize the EI
Complicated by collimation detection and post processing

21. Freeware for CT dose
Image Server
PHP/mySQL
OCR

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

23. Fluoroscopy ?

24. DICOM Structure Report & IHE enhancement
Store Dose Information - Similar to Images Stored
Query Dose Information
Retrieve Dose Information
Submit 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 patient
eHR for recording or Radiation Passport
Access anywhere by digital signature
Data for monitoring public radiation level
Refine existing standard on dosimetry
Enhancement in DICOM & IHE-REM for dose report and dose information communication

28. Thanks www.pacs.hk wongthe@gmail.com