Dosimetry Audit in Radiotherapy, in Greece

1. Dosimetry Audit in Radiotherapy, in Greece Costas J. Hourdakis, A. Boziari & V. Kamenopoulou Greek Atomic Energy Commission, EEAE Athens, 12 September 2014

2. Tools for Quality Regulatory Inspections (Greek Atomic Energy Commission) Clinical Audits Quality Control Quality Assurance (QC-QA) Internal Audits Dosimetry Audits (Greek Atomic Energy Commission) Management System Audits – Accreditation Audits

3. Greek Atomic Energy Commission (ΕΕΑΕ) Competent national regulatory authority in the fields of radiological protection and nuclear safety. It is an independent public service, supervised by the General Secretariat for Research and Technology under the Ministry of Education & Religious Affairs. • Regulatory and legal duties • Inspection duties • Services (personnel dos., calibrations, environmental controls, etc) • Education and research duties • Radiological emergency Integrated Management System : ISO 9001(TUV Hellas) Quality Management Systems : ISO 17020 and ISO 17025 (Hellenic Accreditation System - ESYD)

4. RT & BT in Greece 31 : Hospitals – Clinics (Aug 2014)

5. RT & BT in Greece 4 linacs / 1 M population - 250,000 inhabitants / Linac ≈60 photon beams (6–23 MV) 7 60Co beams ≈ 130 electron beams (4-21 MeV) IMRT at 5 RT centers for ≈ 12 systems Tendency to growth : Replacement of old systems & new centers

6. EEAE inspections and dosimetry audits in RT and BT, in Greece • Scope : • Assessment of radiation protection of workers – patients – public • Assessment of safe performance of radiological equipment • Assessment of applied patient dosimetry • Assessment of applied clinical and dosimetry procedures and practices • Identification of errors and mal-practices / Investigation / Recommendations • Harmonization of dosimetry protocols at national level • Comparison of dosimetry results with other studies worldwide

7. Dosimetry Audits, ΕΕΑΕ • On site visits • Ionization chambers - detectors • EEAE dosimetry & QC equipment (independent from users’) • Calibration in IRCL/EEAE-EIMSSDL • QC-QA and dosimetry protocols (IAEATRS 398) Applied to allRT & BT centers and systems Rounds 1st round : 2002 -2006 2nd round : 2006 -2011 3rd round : 2011 - ...

8. Dosimetry Audits, EEAE • Dosimetry equipment • ABSOLUTE DOSIMETRY • Photons in water : Waterproof Farmer type 0.6 cc - IBAFC65 P IC-69 • Photons in Solid Water Phantom : Flexible IC 0.3 cc - PTW 31003 • Electrons in water : Parallel plate - PTW MARCUS (since 2011) • Electrons in water : Parallel plate - PTW ADVANCE (after 2011) • Electrometer : PTWUNIDOS 10001 • RELATIVE DOSIMETRY • IBA solid state / diodes for photons and electrons

9. Dosimetry Audits, EEAE Basic Phantoms • IBA • RFA 200, 2Dwater phantom • OmniPro-Accept software • Solid state diodes • Farmer IC • P-P electron IC • Solid Water Phantom • Insert for PTW flexible IC

10. Dosimetry Audits, EEAE Dosimetry Audit performed in 4 levels [ performed in sequence : from basic to complex ] Assessment of Mechanical and Functional equipment performance Relative (PDD, profiles, etc) and Absolute dosimetry in water (Gy/MU) Assessment of TPS output Assessment of the overall radiotherapy procedure, for dosimetry

11. Basic parameters : Field size Accuracy of gantry and collimator rotation Accuracy of table movement and rotation Stability of the isocentre (ISO) during rotations Laser accuracy 1. Assessment of Mechanical and Functional equipment performance

12. 1. Assessment of Mechanical and Functional equipment performance Deviations |δ|classified in three categories : |δ|< 2 mm : Accepted 2 <|δ|< 4 mm : Investigation |δ|>4 mm: Non-accepted

13. 1. Assessment of Mechanical and Functional equipment performance 235 tests for Linacs & 81 for Co-60 > 4 mm > 4 mm

14. 2. Relative and Absolute dosimetry

15. 2. Relative and Absolute dosimetry • EEAE measures in water phantom • TPR20,10, for photons • R50 for electrons • percent depth dose, PDD • beam profiles • Dose at reference point, Dw ΕΕΑΕ measurements, DM, are compared with the center’s stated values, DS r = DS/DM relative deviation, dr = [(DS/DM ) – 1] ×100%

16. 2. Relative and Absolute dosimetry Uncertainties of EEAE measurements

17. 2. Absolute dosimetry at reference point (Gy/MU) : Photons Standard uncertainty of DM : ~ 1.5 % Comparison - Acceptance d ≤ 3 % : Accepted 3% < d < 5%: Investigation d ≥ 5% : Non-accepted

18. 2. Absolute dosimetry at reference point (Gy/MU) : Electrons Standard uncertainty ~ 2.0 %

19. 2. Absolute dosimetry : BT Reference Air Kerma Rate (Gy h-1 @ 1m) Standard uncertainty ~ 0.8 %

20. 3. TPS output • Various clinical irradiation conditions are predefined in random, e.g. 18MV, field 12 x 7, depth 8.5 cm, SAD/SSD, Wedge 45o, etc. [Gantry=0o] • TPS calculates the MU (or min), in order to deliver 1 Gyat the predefined depth and irradiation conditions • The irradiation conditions are reproduced at Linac (or Cο60) in a water phantom & the irradiation performed for the calculated MU (or min) • EEAE measures the Dw & deviations from 1 Gy are derived • Tests are performed for many & different irradiation conditions (> 15).

21. 3. TPS output d ≤ 3 % : Accepted 3% < d < 5%: Investigation d ≥ 5% : Non-accepted Standard uncertainty of DM : ~ 1.5 % data > 2011

22. 3. TPS output “We do not complete the audit until we investigate & resolve all deviations (d > 3%)” d ≤ 3 % : Accepted 3% < d < 5%: Investigation d ≥ 5% : Non-accepted Standard uncertainty of DM : ~ 1.5 % data > 2011

23. 4. Assessment of overall RT procedure Simulation of all RT steps, with a solid water phantom : CT scan Simulation Treatment Planning Positioning - Verification Irradiation Hospital’s procedures are followed All steps are performed by the hospital’s staff

24. 4. Assessment of overall RT procedure Flexible IC IC’s reference point is at the geometrical center of the phantom (cross marking).

25. Initial preparation Marking, with bee-bees, a hypothetical original (anatomical) isocentre (ISO)

26. CT scan Images are transfered to TPS

27. Treatment Isocenter determination Anatomical ISO defined by the bee-bees Treatment ISO is determined from the respective CT slice & it corresponds to the geometrical centre of phantom

28. Therapy simulation – Offset determination Followed TPS data : Offset from Original – Anatomical Isocentre to Treatment Isocentre (should be at the phantom center) Deviation of treatment isocentre from phantom geometrical centre d ≤ 2 mm

29. Treatment planning MU calculation, in order to deliver total dose to treatment isocentre (from all fields) 2 Gy CUBE : BOX technique (4 diametrically fields) OBLIQUE : 1 vertical (0o) with wedge and 2 lateral (sideways, e.g. 105o and 255o)

30. Phantom irradiation • Phantom positioning : Cards from TPS are followed • EEAE measures the dose from each field, DM,i and the total dose, DM,T • Comparison of DM,I and DM,T with the dose values as stated by the RT staff, according to TPS output data.

31. 4. Assessment of overall RT procedure Standard uncertainty ~ 3.0 % d ≤ 5 % 5 % < d <7 % d ≥ 7 % data > 2011

32. 4. Assessment of overall RT procedure “We do not complete the audit until we investigate & resolve all deviations (d > 3%)” Standard uncertainty ~ 3.0 % d ≤ 5 % 5 % < d <7 % d ≥ 7 % data > 2011

33. CONCLUSION • Patient Dosimetry and Radiation Protection is at high level in Greece. • EEAE applies system inspections and dosimetry audits in RT and BT (and elsewhere) over 14 years, continuously and systematically. The experience gained is important. • Benefits: Improved dosimetry - harmonization - dissemination of information - strengthening the confidence of hospitals’ staff. • Hospitals welcome and seek inspections and audits of EEAE.

34. Challenges and Future work • Small field dosimetry • Dosimetry in “New technologies” (Tomotherapy, Cyber-Knife Gamma-Knife) • Reporting of accidents • Clinical Audit • Enhancement of “Safety culture” and “Security culture” • “Quantity” vs “Quality” to be balanced in a few cases

35. I thank you for your attention