Initial clinical evaluation of PET-based ion beam therapy monitoring under consideration of organ motion.

Purpose: Intrafractional organ motion imposes considerable challenges to scanned ion beam therapy and demands for a thorough verification of the applied treatment. At the Heidelberg Ion-Beam Therapy Center (HIT), the scanned ion beam delivery is verified by means of postirradiation positron-emission-tomography (PET) imaging. This work presents a first clinical evaluation of PET-based treatment monitoring in ion beam therapy under consideration of target motion.

4D offline PET-based treatment verification in scanned ion beam therapy: a phantom study.

At the Heidelberg Ion-Beam Therapy Center, patient irradiation with scanned proton and carbon ion beams is verified by offline positron emission tomography (PET) imaging: the β+-activity measured within the patient is compared to a prediction calculated on the basis of the treatment planning data in order to identify potential delivery errors. Currently, this monitoring technique is limited to the treatment of static target structures. However, intra-fractional organ motion imposes considerable additional challenges to scanned ion beam radiotherapy.

Comparing the biological washout of β+-activity induced in mice brain after 12C-ion and proton irradiation.

In clinical ion beam therapy, protons as well as heavier ions such as carbon are used for treatment. For protons, β(+)-emitters are only induced by fragmentation reactions in the target (target fragmentation), whereas for heavy ions, they are additionally induced by fragmentations of the projectile (further referred to as autoactivation). An approach utilizing these processes for treatment verification, by comparing measured Positron Emission Tomography (PET) data to predictions from Monte Carlo simulations, has already been clinically implemented.

Automation and uncertainty analysis of a method for in-vivo range verification in particle therapy.

We introduce the automation of the range difference calculation deduced from particle-irradiation induced β(+)-activity distributions with the so-called most-likely-shift approach, and evaluate its reliability via the monitoring of algorithm- and patient-specific uncertainty factors. The calculation of the range deviation is based on the minimization of the absolute profile differences in the distal part of two activity depth profiles shifted against each other. Depending on the workflow of positron emission tomography (PET)-based range verification, the two profiles under evaluation can correspond to measured and simulated distributions, or only measured data from different treatment sessions.

Integration and evaluation of automated Monte Carlo simulations in the clinical practice of scanned proton and carbon ion beam therapy.

Monte Carlo (MC) simulations of beam interaction and transport in matter are increasingly considered as essential tools to support several aspects of radiation therapy. Despite the vast application of MC to photon therapy and scattered proton therapy, clinical experience in scanned ion beam therapy is still scarce. This is especially the case for ions heavier than protons, which pose additional issues like nuclear fragmentation and varying biological effectiveness.