Implementation of dosimetry equipment and phantoms at the MedAustron light ion beam therapy facility

Abstract

Purpose: To describe the implementation of dosimetry equipment and phantoms into clinical practice of light ion beam therapy facilities. This work covers not only standard dosimetry equipment such as computerized water scanners, films, 2D-array, thimble, and plane parallel ionization chambers, but also dosimetry equipment specifically devoted to the pencil beam scanning delivery technique such as water columns, scintillating screens or multilayer ionization chambers. Method: Advanced acceptance testing procedures developed at MedAustron and complementary to the standard acceptance procedures proposed by the manufacturer are presented. Detailed commissioning plans have been implemented for each piece of dosimetry equipment and include an estimate of the overall uncertainty budget for the range of clinical use of each device. Some standard dosimetry equipment used in many facilities was evaluated in detail: for instance, the recombination of a 2D-array or the potential use of a microdiamond detector to measure reference transverse dose profiles in water in the core of the primary pencil beams and in the low-dose nuclear halo (over four orders of magnitude in dose). Results: The implementation of dosimetry equipment as described in this work allowed determining absolute spot sizes and spot positions with an uncertainty better than 0.3 mm. Absolute ranges are determined with an uncertainty comprised of 0.2-0.6 mm, depending on the measured range and were reproduced with a maximum difference of 0.3 mm over a period of 12 months using three different devices. Conclusion: The detailed evaluation procedures of dosimetry equipment and phantoms proposed in this work could serve as a guidance for other medical physicists in ion beam therapy facilities and also in conventional radiation therapy.

Evaluation of electromagnetic and nuclear scattering models in GATE/Geant4 for proton therapy

“…All measurements were carried out in the horizontal beam line of treatment room 3 (IR3) at the MedAustron synchrotron facility using a remotely controlled water phantom MP3‐PL (PTW, Freiburg, Germany). Further details and descriptions of the equipment and calibration procedures are provided in the supplementary materials and literature . The detectors were positioned at the effective point of measurement …”

“…Further details and descriptions of the equipment and calibration procedures are provided in the supplementary materials and literature. [20][21][22] The detectors were positioned at the effective point of measurement z ref . 23,24 Lateral dose (core) profiles were measured using the MicroDiamond (MD) detector due to its small sensitive area minimizing volume averaging effects.…”

Dose detectors, sensors, and their applications

“…Actually, pre‐clinical pencil beam characterization (acceptance and commissioning) and QA procedures require various relative dose measurements as summarized in a recent review on technologies and procedures of clinical dosimetry for scanned ion beam radiotherapy . Commissioning and QA is not only necessary for the beam parameters but also for the equipment itself and an overview of a comprehensive implementation addressing the specific demands of scanned beams is given by Grevillot et al …”

Beam monitor calibration in scanned light‐ion beams

“…21) A further complication arises when the response of the LAIC is not uniform over its sensitive area. 24 The relative response as a function of lateral offset can be expressed normalized to the average response over the entire area,…”