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1

NOVEL DOSIMETRY AUDIT BASED ON END-TO-END TESTING WITH ALANINE

DETECTORS IN PROTON BEAM THERAPY

1

A. Carlino1, H. Palmans1,2, C. Gouldstone2, P. Trnkova3, G. Bosmans4, G. Vilches Freixas4 , I. Rinaldi4, O. Noerrevang5, H. Nyström5, A. Vestergaard5, S. Lorentini6, C.

Algranati6, M. Schwarz6, S. Vatnitsky1, M. Stock1

1 MedAustron Ion Therapy Center, Marie Curie-Straße 5, Wiener Neustadt, Austria.2 National Physical Laboratory, Hampton Road, TW11 0LW Teddington, United Kingdom.

3 HollandPTC, Huismansingel 4, Delft, The Netherlands4 Zuid-Oost Protonen Therapie Centrum (ZON-PTC), Maastricht, The Netherlands

5 Dansk Center for Partikelterapi (DCPT), Aarhus Universitetshospital, Palle Juul-Jensens Boulevard 99, Aarhus, Denmark 6 Centro di Protonterapia , APSS, Via al Desert 14, Trento, Italy

➢ Light Ion Beam Therapy (LIBT) facilities audited

➢ Phantoms & Detectors

➢ End-to-end test procedures

➢ Results

➢ Conclusion

Outline

“GEOGRAPHY” OF AUDIT

MedAustron

APSS Trento

ZON-PTC

Holland-PTC

DCPT

*S/C/SC = Synchrotron (S) or Cyclotron (C) or SynchroCyclotron (SC)**HBL = fixed Horizontal Beam Line***VBL = fixed Vertical Beam Line

LIBT FACILITIES AUDITED

Phantoms & detectors (1) Homogeneous phantom

➢ Homogenous Polystyrene phantom (1.06g/cm3)

➢ Seven plates, each with a size of 20x20x3 cm3

➢ Customized to allocate different detectors:

✓Farmer chamber (PTW 30013)

✓ 20 Alanine pellets

✓ 2 EBT3 Films

Ableitinger, A. et al. “Dosimetry auditing procedure with alanine dosimeters for light ion beam therapy.”, Radiotherapy and Oncology, 2013.

Phantoms & detectors (2) Head phantom

➢ Customization of head phantom in collaboration with CIRS (Tissue Simulation & Phantom Technology) :

- 3 EBT3 films in the head-neck region

- 2 Ionization chambers (Farmer PTW 30013)

- 22 Alanine pellets

Carlino, A. et al. “End-to-end tests using alanine dosimetry in scanned proton beams.”, Physics in Medicine and Biology, 2018.

Mevion – ZON-PTC (NL)

Alanine EPR dosimetry – quenching correction

Implementation in the Monte Carlo of RayStation TPS.

Collaboration with RaySearch Laboratories (Sweden)

3D RE distribution

Carlino, A. et al. “End-to-end tests using alanine dosimetry in scanned proton beams.”, Physics in Medicine and Biology, 2018.

3D dose distribution

M. Bolsa Ferruz et al GATE/Geant4 as a Monte Carlo simulation toolkit for light ion beam dosimetry (Abstract ID 185) Session Title: Protons and Beyond, Wednesday 19.06

End-to-end test procedures

End-to-end test of the entire logistic chain of radiation treatment starting from CTscanning, treatment planning, monitor calibration, patient positioning and beamdelivery. The whole clinical workflow was reproduced as during patient treatment.

CTdata

TPSOIS data data

Head phantom

Pelvis phantom

RVS AcceleratorOIS

In roomImaging

Image registration

End-to-end test procedures

IBA Gantry 2 (Trento, IT)

RVS AcceleratorOIS

Head phantom – Loaded with alanine

In room Positioning(HBL, MedAustron)

Pelvis phantom – Loaded with Farmer ionization chamber

End-to-end test procedures

➢ Box shaped target (8x8x12 cm3 - 768 cc)

➢ Beam arrangement: Gantry 90⁰, Couch 270⁰

➢ 20 alanine pellets in the target volume – Farmer chamber at center of the target

➢ Prescribed dose 11 Gy(RBE)

Homogeneous phantom – One Beam

Results for all facilities – Homogeneous phantom

➢ Average deviation over 20 alanine pellets at each beam line

➢ Average deviation of alanine overall beam lines -0.1 ± 1.0 % (k=2 is 2.0%)

Head phantom – one beam

➢ Cylinder shaped target (230 cc)

➢ Beam arrangement: Gantry 90⁰, Couch 0⁰

➢ 22 alanine pellets in the target volume – Farmer chamber at center of the target

➢ Prescribed dose 11 Gy(RBE)

Results for all facilities – Head phantom

➢ Average deviation over 22 alanine pellets at each beam line

➢ Average deviation of alanine overall beam lines -0.2 ± 1.2 % (k=2 is 2.4%)

Results for all facilities – Alanine vs Farmer chamber

➢ Alanine and Farmer chamber agrees on average -0.5 ± 0.6% in the homogenous phantom

➢ Alanine and Farmer chamber agrees on average -0.4 ± 0.5% in the head phantom

➢ Largest deviation -1.2% in both phantoms

➢ An innovative dosimetry audit service (MedAustron&NPL) has been offered

to the proton therapy community based on the experience gained at

MedAustron.

➢ TPS planned dose is in agreement with Farmer chamber and alanine

measurements within ± 3% at all 5 LIBT facilities included in the study.

➢ Internal dosimetry consistency between alanine and Farmer chamber

measurements was within ± 1.2% in all the phantoms.

➢ Development of dosimetry audit based end-to-end testing for carbon ion

beams is on going at MedAustron.

Take home message

➢ MedAustron medical physics team

Thank you!

Acknowledgments:

➢ Colleagues from NPL (UK):Ana LourencoRussell ThomasCatharine Clark

Contact email : antonio.carlino@medaustron.at