BELdART-2: Moving towards safer radiotherapy. Steven Lelie 1,2, Wouter Schroeyers 1, Brigitte Reniers 1, Sonja Schreurs 1

Transcription

1 BELdART-2: Moving towards safer radiotherapy Steven Lelie 1,2, Wouter Schroeyers 1, Brigitte Reniers 1, Sonja Schreurs 1 1 Nucleair Technologisch Centrum (XIOS/Uhasselt), Wetenschapspark 27, 3590 Diepenbeek 2 BEFY (Vrije Universiteit Brussel), Laarbeeklaan 101, 1090 Jette International Symposium 50 years BVS-ABR, April 10 th, Brussels

2 TOC Introduction BELdART-1 BELdART-2 The future Conclusions

3 Introduction Succes/Failure absorbed doses Centers do QA What if: Wrong calibration Faulty equipment Need for an external audit

4 Introduction (2) What was/is available? (not free of charge) IAEA & WHO: TLD audit (since 1969) World wide TLD audits Postal audit for photon beams Focus on developing countries ESTRO-QUALity assurance network (since 1998) European postal audit with TLD Photon & Electron beams RPC-MD Anderson (1968) World wide TLD audits Moving towards OSL

5 Introduction (3) Starting from 2009 FANC asked for a national audit program for reference and non reference conditions via public tender NuTeC was selected to perform a national audit BELdART was born (feb 2009) No cost for center A total of 34 centers 91 clinical machines

6 BELdART-1 Visited audit of all centers (+ satellites) Auditing of Basic mechanical parameters Photon beams Electron beams Equipment independent of hospital

7 BELdART-1 (2) BELdART was unique: Visited national audit including all centers All centers participated with at least 1 accelerator Used the L-α-alanine dosimetry system

8 The alanine system ) ( 1 0 T T c k T T t c f t e k b sleeve sleeve b f f b T T Q Q M j j M j j b b m D k k k k k k k k with k D m m A 0, ) (7.0 d c t ) (1.8 K c T D w expressed as Dose Normalized Amplitude D w calculated with calibration Curve b ad w b D Q Co b D c w k D D 60 0 Base function using reference dosimeters of 0 Gy and 20 Gy Calibration using dosimeters in the range 2 Gy 25 Gy

9 The alanine system Measurement uncertainties Part of continuous internal QA procedure 5 measurements of calibration set over several months

10 The alanine system Uncertainty budget (4 Harwell detectors; 5 rotations, 4 Gy): Base function detectors (20 Gy): Dose (primary standard) 0.20% Amplitude: (A b D) 0.15% Mass: ( 50mg) 0.04% Field detector (4 Gy): Amplitude: (A D ; 30 mgy = worst case) 0.75% Mass:( 50mg) 0.04% Experimental conditions: Fading: 0.02% Irr temp: 0.03% Beam quality: 0.27% Positioning 0.05% Combined standard uncertainty 0.84%

11 Audit protocol Mechanical parameters Position of the isocenter Optical distance indicator Position of the laser lines Correspondence light-radiation field

12 Audit protocol (2) Dosimetrical tests (reference and non-reference) Exp Experiment Depth (cm) Irradiation distance Field size accessory Det. Dose ref 1 Ref. field d ref ssd or sad 10cm x 10cm no 1 4 Gy Tray factor D ref ssd or sad 10cm x 10cm tray 2 4 Gy Energy open beam 4 Energy beam with wedge 10&20 ssd or sad 10cm x 10cm no 3,4 4 Gy &20 ssd or sad 10cm x 10cm wedge 5,6 4 Gy Output factor1 8 ssd or sad 6cm x 6cm no 7 4 Gy Output factor2 8 ssd or sad 8cm x 20cm no 8 4 Gy Output factor3 8 ssd or sad 20cm x 8cm no 9 4 Gy Output factor4 8 sad or ssd 20cm x 20cm no 10 4 Gy MLC 1 Circular 8 ssd or sad 5.6cm circular no 11 4 Gy MLC 2 inverted Y 11 MLC 3 irreg.+ wedge 8 ssd or sad 15cm x 12cm no 12 4 Gy ssd or sad 12cm x 8 cm wedge 13 4 Gy 3.11

13 Audit protocol (3) Exp Experiment Depth (cm) Irradiation distance Field size accessory Nr det Delivered dose ref 12 Ref. field_ MeV1 d ref ssd or clinical practice 10cm x 10cm no 15 4 Gy Ref. field_ MeV2 (R 50 > 7 cm) d ref ssd or clinical practice 10cm x 10cm no 16 4 Gy 4.14 The relative deviation is classified in 4 levels: The relative deviation d º D measured - D center D center is classified into 4 levels: "within optimal level": d 3% "out of optimal level but within tolerance": 3% < d 5% "out of tolerance level": 5% < d 10% "alarm level": d > 10%

14 BELdART-1 results All centers were audited for at least 1 unit A total of 61 out of 91 machines Total number of 212 beams Not audited: Tomotherapy Cyberknife Gammeknife Mobetron

15 BELdART-1 results Mechanical parameters

16 optimal, within tolerance, out of tolerance and alarm for all high-energy photon beams as BELdART-1 results registered in the 1 st runs measurement campaign. The deviation in emergency level was connected to test D2 but appeared to be non significant, as the second run check of this beam was within Dosimetric parameters Fig. 3.7: tolerance level. No explanation could be found a posteriori. Relative and absolute frequencies for the four levels in deviation for the dosimetrical tests as a result of 2 nd run measurements in high-energy photon beams. 0% 0% 6% δ > 10% Eighty second run measurements (6%) were completed versus 1375 first run measurements. After 10% δ > 5% completing the 2nd run measuring campaign, 5% all test δ > 3% measurements δ are within # tolerance % level or 94% δ 3% δ > 10% 1 0,1 better (Fig. 3.7) that is: 96.7% of all measurements in high-energy photon beams are within optimal 10% δ > 5% 4 0,3 level and only 3.3% of the measurements remain in the tolerance 5% δ > 3% level. For 80 the latter, 5,9the local physicist was asked to take a close look at these measurements. δ 3% ,7 Fig. 3.6: Relative and absolute frequencies for the four levels in deviation for the dosimetrical tests as a result of 1 st run measurements in high-energy photon beams. 1% 4% 13% 82% δ > 10% 10% δ > 5% 5% δ > 3% δ 3% δ # % δ > 10% 1 1,0 10% δ > 5% 4 4,1 5% δ > 3% 13 13,3 δ 3% 80 81,6 Fig. 3.8: Percentages and absolute values of 1 st run measurements in electron beams regarding to their deviations.

17 BELdART-1 results Belgian Dosimetry Audits in Radiotherapy (BELdART) : final report. 50 Dosimetric parameters 0% 0% 3% Fig. 3.7: δ > 10% 10% δ > 5% 5% δ > 3% δ # % 97% δ 3% δ > 10% 0 0,0 10% δ > 5% 0 0,0 5% δ > 3% 44 3,3 δ 3% ,7 Belgian Dosimetry Audits in Radiotherapy (BELdART) : final report. 51 Relative and absolute frequencies for the four levels in deviation for the dosimetrical tests as a result of 2 nd run measurements in high-energy photon beams. 0% 0% 13% Eighty second run measurements (6%) were completed versus 1375 first run measurements. After δ > 10% completing the 2nd run measuring campaign, all test measurements are within tolerance level or 10% δ > 5% better (Fig. 3.7) that is: 96.7% of all measurements in high-energy photon beams are within optimal 5% δ > 3% δ # % level and 87% only 3.3% of the measurements δ remain 3% in the tolerance level. For the latter, the local δ > 10% 0 0,0 physicist was asked to take a close look at these measurements. 10% δ > 5% 0 0,0 5% δ > 3% 14 12,7 δ 3% 96 87,3 Fig. 3.9: Percentage and absolute values after the 2 nd run measurements in electron beams regarding to their deviations. Regarding measurements in high-energy electron beams, we can make an analogous analysis. Fig. 3.8

18 Audited centers

19 BELdART-2 Courtesy of Varian Medical Systems

20 BELdART-2 Advanced and dynamic radiotherapy IMRT RapidARC Tomotherapy Cyberknife

21 Protocol A combination of L-α-alanine dosimetry 2 pellets per point instead of 4 Both in high and low dose points Used for absolute dosimetry EBT-3 film dosimetry 3-channel algorithm 2D dose distributions In plane of alanine pellets (relating to absolute dose)

22 3-channel

23 BELdART-2 planning Devided in 2 phases Phase 1 (6 months) Getting some feeling with EBT3 What could we expect in Belgium Homogeneous phantom with selected centers Phase 2 Open for all radiotherapy centers Heterogeneous phantom

24 Phase 1: what did we check? Delivery of the modulation Beam configuration

25 BELdART-2: Phase 1 Use of easy-cube phantom Because of the shape: Prostate case with Prostate Rectum Bladder Film through all 3 structures (sagittal plane)

26 BELdART-2: Phase 1

27 Phase 2: Delivery of the modulation heterogeneities

28 Phase 2: Heterogeneous phantom: Lung or head & neck phantom Including Heterogeneities Imaging Tumor definition (using a description provided) Radiotherapy planning Image guided positioning (if applicable) Treatment

29 Dosimeters For both phases: Dosimeters are inserted by the BELdART-2 team Phantom delivered including dosimeters No visit of the auditor in the center during treatment/planning Phantom has to be treated as if a patient Audit is free of charge for all Belgian radiotherapy centers!

30 What is checked by the end?

31 BELdART-3? New technologies are being implemented

32 Conclusion Radiotherapy is in constant movement A rigid, independent auditing system is necessary to ensure safe radiotherapy BELdART-1 showed that all radiotherapy center work within tolerance levels BELdART-2 is the first national audit investigating the implementation of advanced radiotherapy techniques Within 3 years we will know how good we work in Belgium

33 A word of thanks to The scientific IMRT committee Michael Duchateau, UZBrussel Wouter Crijns, UZLeuven Yassine Boucours, Centre Hospitalier Peltzer-La Tourelle Antoine Delor, UCL Michel Mathot, University of Liege The steering committee François Sergent; Clinique et Maternité Ste-Elisabeth Stefaan Vynckier; UCL Dirk Verellen; UZBrussel Alex Rijnders; Cliniques de l Europe Karen Feyen; AZ St. Maarten

34 Thank you Symposium: Radiation protection for medical doctors Date: Saterday April 27 th 2013 Location: Klein Auditorium, Uhasselt campus Oude gevangenis, Hasselt Target audience: Surgeons, intervention cardiologists, reumatologists, dentists, More info?