Our History: Who We Are and How We Started
MedAustron is a light-ion beam therapy and research facility in Wiener Neustadt in the county of Lower Austria (Austria). The facility is equipped with a synchrotron accelerator able to deliver protons with energies from of 62.4 to 252.7 MeV range in water (from 3 cm to 38 cm) and carbon ions with energies per nucleon ranging from 120 to 402.8 MeV/n (range in water from 3 cm to 27 cm). All four irradiation rooms have been supplied with pencil beam scanning (PBS) delivery systems. The first patient with protons has been treated in December 2016, while the treatment with carbon ions started in July 2019. Prior to the first patient treatment with protons at the fixed Horizontal Beam Line (HBL) in Irradiation Room IR3, abbreviated as IR3HBL, an effective internal dosimetry auditing procedure based on end-to-end testing was implemented as the last step of the medical commissioning.
This innovative methodology using alanine Electron Paramagnetic Resonance (EPR) dosimetry was developed in collaboration with the National Physical Laboratory (NPL). The same collaboration between MA and NPL has previously resulted in a pilot study for alanine dosimetry audit in scanned proton and carbon ion beams that was published by Ableitinger et al. (2013). In 2017 and 2018, end-to-end testing procedures were performed before starting patient treatments at the IR2HBL and at the Vertical Beam Line (VBL) installed in IR2, abbreviated as IR2VBL. More than 500 alanine detectors have been irradiated over three years at MA and most of the results are reported by Carlino et al. (2018). Since September 2018, based on the successful experience over the last 6 years, MedAustron in collaboration with NPL started offering an external dosimetry audit based on end-to-end testing to proton PBS facilities. In the first months of activity four European centers have been audited and several other centers are in planning. Dosimetry audit service based on end-to-end testing for carbon ion beams will be offered in the near future.
Motivation of Dosimetric Audit for Proton Therapy Facilities
Technological developments in radiation therapy enabled the implementation of pencil beam scanning (PBS) delivery and the next generation of proton beam therapy facilities in Europe will employ only PBS delivery. The increased complexity related to implementation of PBS technology places new demands on a comprehensive quality assurance (QA) programme that should be established to cover all steps of the treatment process and to confirm the dosimetric integrity of the PBS delivery. An important part of this QA program that should be performed before beginning patient treatments, is a full simulation of the workflow and verification of the delivered dose for different tumor sites. To implement this step, PBS facilities can either use their internal resources and perform internal integrity checks or apply to external independent auditing resources. However, there was no audit provider in Europe that can perform independent external auditing for proton therapy facilities.
To fill this gap, MedAustron, in collaboration with NPL (UK), is offering dosimetry auditing based on end-to-end tests. Our dosimetry audit aims to assess the complete PBS radiotherapy procedure. Pre-treatment imaging, treatment planning including TPS dose calculation and radiotherapy delivery are applied to homogeneous or anthropomorphic phantoms, and reviewed following a pathway similar to that of a typical patient. To perform the audit our dosimetry group visits the proton center, performs measurements using ionization chambers, alanine detectors and films using appropriate phantoms and auxiliary instrumentation, and provides a final audit report.