ESTRO 2024 - Abstract Book

S3845

Physics - Image acquisition and processing

ESTRO 2024

[4] Zegers CML, Hoebers FJP, van Elmpt W, Bons JA, Öllers MC, Troost EGC, et al. Evaluation of tumour hypoxia during radiotherapy using [18F]HX4 PET imaging and blood biomarkers in patients with head and neck cancer. Eur J Nucl Med Mol Imaging 2016;43:2139–46. https://doi.org/10.1007/S00259-016-3429-Y.

1563

Poster Discussion

Towards real-time range verification for head and neck treatments based on in-beam PET imaging

Brian Zapien Campos 1 , Zahra Ahmadi Ganjeh 1 , Giuliano Perotti Bernardini 2 , Jeffrey Free 2 , Stefan Both 2 , Peter Dendooven 1 1 Particle Therapy Research Center, University Medical Center Groningen, Radiation Oncology, Groningen, Netherlands. 2 University Medical Center Groningen, Radiation Oncology, Groningen, Netherlands

Purpose/Objective:

A current challenge in proton therapy is addressing clinical complications in organs at risk resulting from dose delivery errors. These errors are caused by range uncertainties whose main sources are: beam, patient, and treatment planning system setup [1], [2]. This is the main reason why range monitoring during treatment delivery is important to improve the treatment's effectiveness. In this study, we aim to establish an accurate method for real-time monitoring of proton range using positron emission tomography (PET). We measured range deviations produced by controlled clinical scenarios in clinically realistic irradiations of a head-and-neck (HN) phantom.

Material/Methods:

Irradiation setup : A dual-head Siemens Biograph mCT PET scanner [3] was installed in a proton therapy treatment room to image the activity induced on an upright placed CIRS-731 HN phantom during proton irradiations, The treatment delivery was carried out at 90° gantry angle, using a Proteus Plus, IBA unit (fig.1). Treatment plan : The plans consisted of clinically realistic irradiations in two different sites, which were generated in RayStation v11b TPS using pencil beam scanning (PBS). Clinical target volumes (CTVs) were defined as spheres (Ø=4 cm) located at the lower part of the brain (Plan 1) and at the C2 level in the neck (Plan 2). Both treatments were optimized to meet objective functions: uniform dose of 400 cGy, minimum dose of 392 cGy, and maximum dose of 408 cGy within the CTV. The dose delivered represents twice that delivered in a conventional fraction; this was done to compensate for the non-maximized efficiency of the PET scanner. Plan 1 and Plan 2 comprised 987 and 737 spots; and a minimum-maximum energy of 102.7-146.5 MeV and 70-109.3 MeV, respectively. Setup modifications . To assess the precision of this approach, each treatment was delivered five times, one nominal irradiation and four under setup modifications of clinical relevance. The modifications included range shifts using 2 and 5-mm solid water slabs, and treatment couch movements of 3 mm in both downward and leftward (in beam-eye view) directions.