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Ionization Chamber Array for External Beam Radiotherapy

Ionization Chamber Array for External Beam Radiotherapy. Michele Togno - III ARDENT Annual Meeting, Schwarzenbruck - Septem ber, 30 th 2014. Project goal. A short summary. MV X-Rays. ~100÷230MeV protons. Absolute dose measurement Machine quality assurance Patient quality assurance.

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Ionization Chamber Array for External Beam Radiotherapy

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  1. Ionization Chamber Array for External Beam Radiotherapy Michele Togno - III ARDENT Annual Meeting, Schwarzenbruck - September, 30th 2014

  2. Project goal A short summary MV X-Rays ~100÷230MeV protons • Absolute dose measurement • Machine quality assurance • Patient quality assurance

  3. Outline • Experimental Activity • Characterization at IBA DosLab • Characterization at Klinikum rechts der Isar & University of California (San Francisco)-Radiation Oncology dep. • Characterization at Proton Therapy Center Czech s.r.o. • Ongoing activities and future work • ARDENT project: trainings, conferences, secondments

  4. Experimental Activity Michele Togno - III ARDENT Annual Meeting, Schwarzenbruck - September, 30th 2014

  5. Detector evolution First Prototype Measurement setup • 80 ionization chambers, 3.5mm pitch Second Prototype

  6. Characterization at IBA DosLab Prototype optimization Main debug issue: time stability of the chamber current. Example: two 60Co irradiations (detector biased at 100V). Current ~ 10pA Signal (normalized) 0.92 0.96 1.00 1.04 Signal about 8pA (@2.2Gy/min) 0 50 100 150 200 250 300 Time (s) Signal (normalized) -0.2 0 0.2 0.4 0.6 0.8 1 1.2 • Optimization of signal routing led to a better time stability of the sensor: • Pretty good stability in time of the signal • Prompt rise and fall time 60Co, 150V bias, Tint=0.8s Sensitivity  200pC/Gy Fluctuation  0.3% (st.dev.) 0 20 40 60 80 90 100 120 40 0 -20 60 Time (s)

  7. Characterization at IBA DosLab Charge collection efficiency • Charge collection efficiency higher than 99% already at 150V (99.5% ± 0.3% at 250V)

  8. Characterization at IBA DosLab Sensitivity dependence on dose per pulse • ± 0.8% sensitivity change on dose per pulse in the range 0.09÷2.67mGy/pulse

  9. Characterization at IBA DosLab Tissue to phantom ratio measurement • Very good agreement with PPC05 (better than 0.5%) at every depth of measurement

  10. Characterization at IBA DosLab Elekta Agility Output Factors • Good agreement with reference for small fields, reduced sensitivity with large fields -3.7% -2.4% a:Si flat panel, a prototype optimized for dosimetry

  11. Characterization at IBA DosLab Beam profiles (photons)

  12. Characterization at MRI Machine QA: virtual wedges, MLC QA, dose in depth (see pics) MapCheck2 (SunNuclear) diode array Varian Clinac DHX • Secondment, 22nd April - 3rd May, Klinikum rechts der Isar (Munich)

  13. Characterization at MRI Example of patient QA Varian Trilogy, Millennium MLC, VMAT delivery technique EBT3

  14. Characterization at UCSF Clinical tests & clinical training • Secondment, 28th July - 8th August, UCSF department of Radiation Oncology; • Detector characterization through clinical test; • Clinical training: • Machine QA; • Introductory training to Pinnacle TPS; • Use of gafchromic films; • Joined the daily activity of medical physicists.

  15. Characterization at UCSF Example of small field dosimetry and linac commissioning 1x1cm2 Varian TrueBeam Virtual wedge 45°

  16. Characterization at UCSF Example of linac commissioning measurement Water phantom as reference

  17. Characterization at PTC czechs.r.o. Dose linearity PBS mode only 1ms pulse duration, 10ms pulse period, 3.5mm spot  at 226MeV 0.02-2MU/spot 33x17 spot map Output norm. to 1MU/spot 0.01% -0.04% -0.05% -0.1% Ref detector: PPC05 0.8% -0.9% IC array signal (pC) 1.7% PPC05 signal (nC)

  18. Characterization at PTC czechs.r.o. Beam profiles (protons) Lynx: a scintillator based detector for PBS mode machine QA

  19. Ongoing activities/Future work • Long term stability measurements with 60Co • Further test with PBS proton beams; • Paper about the characterization of the 1D IC array prototype; • Extend the technology to a 2D detector - components drawing already started, first prototype assembling foreseen for the end of the year.

  20. Trainings, conferences, secondments… Michele Togno - III ARDENT Annual Meeting, Schwarzenbruck - September, 30th 2014

  21. Secondments UCSF RadOnc dep., S.Francisco (28.07 - 08.09.2014) Klinikum rechts der Isar, Munich (22.04 - 03.05.2014) • Upcoming: • B&A secondment at STMicroelectronics (Catania, July 2015 tentative) • UCSF (early 2015 tentative)

  22. Conferences, trainings… • AAPM, Austin (TX), 20.07 - 25.07.2014 • Poster presentation: “An Ionization Chamber Array with High Spatial Resolution for External Beam Radiotherapy”, M.Togno, D.Menichelli, J.J.Wilkens. • Upcoming: AAPM 2015, … • Trainings: • Clinical trainings at MRI & UCSF (already mentioned); • Radiation protection training (IBA Dosimetry); • Training on SBRT radiotherapy technique (Klinikum rechts der Isar); • ARDENT B&A training (CERN): Technology Transfer, Management, Entrepreneurship. • PhD activities:already spent more than 2 weeks at the University to teach students at physics labs.

  23. Thank you! Michele Togno - III ARDENT Annual Meeting, Schwarzenbruck - September, 30th 2014

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