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

2. Project goal A short summary Absolute dose measurement
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 80 ionization chambers, 3.5mm pitch 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.
Signal (normalized)
Time (s)
Example: two 60Co irradiations (detector biased at 100V).
Current ~ 10pA
Signal (normalized)
Time (s)
Signal about 8pA
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.)
-20 40 60

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
EBT3
Varian Trilogy,
Millennium MLC,
VMAT delivery technique

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 czech s.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
-0.04%
1.7%
-0.9%
0.8%
-0.1%
-0.05%
0.01%
PPC05 signal (nC)
IC array signal (pC)
Ref detector: PPC05

18. Characterization at PTC czech s.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 Upcoming:
Klinikum rechts der Isar, Munich ( )
UCSF RadOnc dep., S.Francisco ( )
Upcoming:
B&A secondment at STMicroelectronics (Catania, July 2015 tentative)
UCSF (early 2015 tentative)

22. Conferences, trainings…
AAPM, Austin (TX),
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