International Conference on Modern Radiotherapy: Advances and Challenges in Radiation Protection of Patients LESSONS FROM FRENCH ACCIDENTS S. Derreumaux, B. Aubert and P. Gourmelon Institut de Radioprotection et de Sûreté Nucléaire Versailles, France December 2 – 4, 2009 International Conference on Modern Radiotherapy: Advances and Challenges in Radiation Protection of Patients Accidents declared in France since 2005 Why? Because declaration to the national authorities is only mandatory since 2001 Where When Patients involved ASN/SFRO score* Case 1 2003 1 4 Case 2 2004 1 5 Case 3 2004 1 4 Case 4.1 May 2004 ‐ May 2005 24 6 Case 4.2 2001‐2006 397 3 Case 4.3 1987‐2000 312 n.d.** Case 5 April 2006 ‐ April 2007 145 n.d.** * After Common Terminology Criteria for Adverse Events (CTCAE V3.0) ** Not determined Versailles, France December 2 – 4, 2009 International Conference on Modern Radiotherapy: Advances and Challenges in Radiation Protection of Patients Expert investigations by IRSN Versailles, France December 2 – 4, 2009 International Conference on Modern Radiotherapy: Advances and Challenges in Radiation Protection of Patients IRSN Role: Public expert body in charge of the scientific assessment related to nuclear and radiological risks 3 major missions: Research Contribution to public policies and technical support to public authorities Services to industry and other organisations Versailles, France December 2 – 4, 2009 International Conference on Modern Radiotherapy: Advances and Challenges in Radiation Protection of Patients IRSN Radiological Protection and Human Health Division: Radiological protection studies and expertise Radiobiology and epidemiology External dosimetry Internal dosimetry Accidents in radiotherapy: Inspection with ASN after declaration of accident Analysis of causes and consequences (experts in medical physics, retrospective dosimetry and radiopathology) Care of patients: Estimation of risks of complications Innovative treatments Reports and recommendations (www.irsn.fr) Versailles, France December 2 – 4, 2009 International Conference on Modern Radiotherapy: Advances and Challenges in Radiation Protection of Patients Case 2 Treatment of intracranial AVM : New linac + additionnal cylindrical collimator RX 6 MV Fields : linac collimator: 40 mm x 40 mm additionnal collimator: Ø = 10 → 30 mm First part of the treatment : « Collimator aperture = 40 x 40 » Linac collimator : 40 cm x 40 cm Versailles, France December 2 – 4, 2009 International Conference on Modern Radiotherapy: Advances and Challenges in Radiation Protection of Patients Case 2 Lessons learned : Potential errors : Additional accelerator accessory without safety device Prevention: Safety of treatment machine (entire system) Versailles, France December 2 – 4, 2009 International Conference on Modern Radiotherapy: Advances and Challenges in Radiation Protection of Patients Case 4.1 Treatment of prostate cancer : RX 25 MV Fields: 5 MLC fields (4 wedged) Implementation of « dynamic wedge » Wedge factor (WF) = dose with wedge/dose without wedge MU calculation with static wedge but treatment with dynamic wedge : TPS WF_dynamic / WF_static = 1.3 (30°) → 1.5 (45°) ⇒ overdose = 20% → 35% Versailles, France December 2 – 4, 2009 International Conference on Modern Radiotherapy: Advances and Challenges in Radiation Protection of Patients Case 4.2 Treatment of prostate cancer : Conformal radiotherapy Control MV images: patients position: orthogonal fields field control: all fields Daily dose due to MV images : ≈ 0.15 ‐ 0.2 Gy Planned field Real field Everyday MV control images, not taken into account for dose calculation: Overexposure ≈ 8% Versailles, France December 2 – 4, 2009 International Conference on Modern Radiotherapy: Case 4.3 Advances and Challenges in Radiation Protection of Patients All isocentric treatments SAD = 100 cm Reference conditions for measurement of dose rate (cGy/MU): Source 100 cm 10 cm x 10 cm beam at SSD = 100 cm dmax dmax = 1.5 cm for 6 MV 2.7 cm for 12 MV 3.5 cm for 25 MV Reference point MU calculation using reference dose rate, without correction for distance : Overdose: Nb Nbof ofMU MU (isocentric) (isocentric) == x OF x TMR x Fw x Ftrans 6 MV : 3 % 12 MV : 5.5 % 25 MV : 7 % Versailles, France December 2 – 4, 2009 International Conference on Modern Radiotherapy: Advances and Challenges in Radiation Protection of Patients Cases 4.1 to 4.3 Lessons learned: Potential errors : Wrong use of TPS due to lack of training + unsafe screen display Dose due to control imaging (MV portal) not taken into account Calculation error due to in‐house software, not tested, not qualified Sole physicist Prevention: Time and organisation for continuous training Team of physicists (at least 2) QA for softwares Softwares with safe human‐computer interaction In vivo dosimetry and second independent calculation Versailles, France December 2 – 4, 2009 International Conference on Modern Radiotherapy: Advances and Challenges in Radiation Protection of Patients Case 5 Stereotactic radiosurgery with micro MLC: Calibration measurements (scatter factors) made with wrong detector: Sensitive volume of « Farmer » ionisation chamber 1,2 Scatter factor 1 0,8 Farmer Pinpoint 0,6 0,4 0,2 0 0 10 20 30 40 50 60 70 80 90 100 Square field size (mm) « Farmer » chamber: 0.65 cm3 « Pinpoint » chamber: ≤ 0.03 cm3 Overdose : up to ~200 % Versailles, France December 2 – 4, 2009 International Conference on Modern Radiotherapy: Advances and Challenges in Radiation Protection of Patients Case 5 Lessons learned: Potential errors: Lack of international protocol for dose determination in small beams Usual dosimetric material not adapted to special techniques Errors due to lack of expertise (special techniques) Sole physicist without experience in RT Prevention: Special techniques only accessible to expert teams Verification of the dose delivered in treatment conditions External audit also for special techniques Team of physicists (at least 2) Versailles, France December 2 – 4, 2009 International Conference on Modern Radiotherapy: Advances and Challenges in Radiation Protection of Patients National inquiry for small beams Scatter factors measured following manufacturers instructions: RX 6 MV; BrainLAB m3 microMLC; SSD = 1000 mm; z = 50 mm 1 Spread of values: 0,95 0,9 Scattered factors 0,85 0,8 0,75 Pi nPoi nt PTW 31006 (Ce ntre 1 ‐ MLC i nté gré ) Di ode SFD (Centre 1 ‐ MLC i nté gré) 0,7 ~ 5‐10% for fields ≥ 12 mm x 12 mm Pi nPoi nt PTW 31006 (Ce ntre 2) 0,65 Pi nPoi nt PTW 31006 (Ce ntre 3 DSP~1000) 0,6 PP 31006 // a xe (Ce ntre 8) Pi nPoi nt PTW 31006 (Ce ntre 11) 0,55 ~ 30% for smallest field (6 mm x 6 mm) Wel l höfe r CC01 (Centre 11) Pi nPoi nt PTW 31006 (Ce ntre 15) 0,5 0,45 Bra i nLAB WOI 10‐26 0,4 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 Side of square field (mm) Often: only one detector used in a RT centre Versailles, France December 2 – 4, 2009 International Conference on Modern Radiotherapy: Advances and Challenges in Radiation Protection of Patients Small beams: other sources of errors Uncertainty on jaws aperture and centering (~ 1‐2 mm): Possible large error (‐20%) on measured scattered factors if jaws are inside the MLC field (Novalis, miniMLC: 6x6 mm2) Limits of usual algorithms for calculation of absorbed dose in highly heterogeneous medium: Possible large error (+10%) in case of lung heterogeneity (Raytrace, CyberKnife, 20 mm diameter beams)* Error increases when field size decreases ** *C.‐M. Ma et al., Third McGill International Workshop, Journal of Physics: Conference Series 102, 2008. **E. W Wilcox & G. M. Daskalov, Med. Phys. 35 (6), 2008. Versailles, France December 2 – 4, 2009 International Conference on Modern Radiotherapy: Advances and Challenges in Radiation Protection of Patients Main IRSN recommandations To improve control of delivered dose: In vivo dosimetry and independent MU calculation Commissioning and quality controls, including external audits, need to be done for all clinically relevant irradiating conditions Experimental validation of new techniques before clinical use New technologies or special techniques: research to improve knowledge (detectors and protocols) Dose due to control imaging: evaluation, taking into account if significant, optimization of controls Versailles, France December 2 – 4, 2009 International Conference on Modern Radiotherapy: Advances and Challenges in Radiation Protection of Patients Main IRSN recommandations To improve human management: Organization of medical physics in hospitals: structure independent from medical hierarchy Complex techniques only used by expert teams Human resources: need to increase professionals, especially medical physicists the number of Education and training: medical physics as a scientific branch in University (Master + 2 years); continuous training for all RT professionals Training program on risk management for professionals Versailles, France December 2 – 4, 2009 International Conference on Modern Radiotherapy: Advances and Challenges in Radiation Protection of Patients Physicists demography in France Versailles, France December 2 – 4, 2009 International Conference on Modern Radiotherapy: Advances and Challenges in Radiation Protection of Patients Main IRSN recommandations To improve computer safety: Only use of qualified, tested and locked softwares Quality assurance procedures for the whole computer network (connections between softwares) Design of machines and softwares: taking into account human– computer interaction Integrated systems (accelerator + TPS): manufacturer’s dosimetric data in TPS Versailles, France December 2 – 4, 2009 International Conference on Modern Radiotherapy: Advances and Challenges in Radiation Protection of Patients Main IRSN recommandations To improve practices: Clinical audits Harmonization of medical practices New technologies or special techniques: agreement of patients if no expert consensus or recommendation (dose) National register for cancer: global follow‐up of patients treated by radiotherapy (remission, morbidity, complications) Medical physicists: critical approach of new technologies and manufacturer’s instructions Versailles, France December 2 – 4, 2009 International Conference on Modern Radiotherapy: Advances and Challenges in Radiation Protection of Patients Main IRSN recommandations To improve management of adverse reactions: Side effects with new technologies and irradiation techniques: fundamental research to better evaluate risk Complications: epidemiological and molecular studies to better evaluate occurrence rates Severe complications: development of therapeutic strategies To improve safety culture: Update of publications on lessons learned from accidents: Risks of new technologies and special techniques Criteria to define and classify accidental exposures Versailles, France December 2 – 4, 2009 International Conference on Modern Radiotherapy: Advances and Challenges in Radiation Protection of Patients Work in progress in IRSN Research and expertise development for the management of accidents: Retrospective dosimetry Radiopathology (diagnosis, prognosis, treatment) Studies and research management): on adverse reactions (knowledge, Side effects: ROSIRIS, Cardiorisk Complications: EPOPA Severe complications: autologous transplantation of adult stem cells R & D on dose measurement in small beams Research on human and organizational factors (safety experts) Versailles, France December 2 – 4, 2009
