Parameter based 4D dose calculations for proton therapy

Franciska Lebbink; Silvia Stocchiero; Piero Fossati; Erik Engwall; Dietmar Georg; Markus Stock; Barbara Knäusl

doi:10.1016/j.phro.2023.100473

Parameter based 4D dose calculations for proton therapy

Phys Imaging Radiat Oncol. 2023 Jul 20:27:100473. doi: 10.1016/j.phro.2023.100473. eCollection 2023 Jul.

Authors

Franciska Lebbink^{1

2}, Silvia Stocchiero^{1

2}, Piero Fossati^{2

3}, Erik Engwall⁴, Dietmar Georg^{1

2}, Markus Stock^{2

3}, Barbara Knäusl^{1

2}

Affiliations

¹ Medical University of Vienna, Department of Radiation Oncology, Vienna, Austria.
² MedAustron Ion Therapy Centre, Wiener Neustadt, Austria.
³ Karl Landsteiner University of Health Sciences, Wiener Neustadt, Austria.
⁴ RaySearch Laboratories, Stockholm, Sweden.

Abstract

Background and purpose Retrospective log file-based analysis provides the actual dose delivered based on the patient's breathing and the daily beam-delivery dynamics. To predict the motion sensitivity of the treatment plan on a patient-specific basis before treatment start a prospective tool is required. Such a parameter-based tool has been investigated with the aim to be used in clinical routine. Materials and Methods 4D dose calculations (4DDC) were performed for seven cancer patients with small breathing motion treated with scanned pulsed proton beams. Validation of the parameter-based 4DDC (p-4DDC) method was performed with an anthropomorphic phantom and patient data employing measurements and a log file-based 4DDC tool. The dose volume histogram parameters ( $D_{x %}$ ) were investigated for the target and the organs at risk, compared to static and the file-based approach. Results The difference between the measured and the p-4DDC dose was within the deviation of the measurements. The maximum deviation was 0.4Gy. For the planning target volume $D_{98 %}$ varied up to 15% compared to the static scenario, while the results from the log file and p-4DDC agreed within 2%. For the liver patients, $D_{33 % liver}$ deviated up to 35% compared to static and 10% comparing the two 4DDC tools, while for the pancreas patients the $D_{1 % stomach}$ varied up to 45% and 11%, respectively. Conclusion The results showed that p-4DDC could be used prospectively. The next step will be the clinical implementation of the p-4DDC tool, which can support a decision to either adapt the treatment plan or apply motion mitigation strategies.

Keywords: 4D; Dose calculations; Interplay; Liver and pancreatic cancer; Measurements; Pencil beam scanning; Proton therapy.