Wolfgang Enghardt

Research Facility for Radiobiological Studies at the University Proton Therapy Dresden

Purpose In order to take full advantage of proton radiotherapy, the biological effect of protons in normal and tumor tissue should be investigated and understood in detail. The ongoing discussion on variable relative biological effectiveness along the proton depth dose distribution (eg, Paganetti 2015), and also the administration of concomitant treatments, demands dedicated in vitro trials that prepare the translation into the clinics. Therefore, a setup for radiobiological studies and the corresponding dosimetry should be established that enables in vitro experiments at a horizontal proton beam and a clinical 6 MV photon linear accelerator (Linac) as reference. Methods The experimental proton beam at the University Proton Therapy Dresden is characterized by high beam availability and reliability throughout the day in parallel to patient treatment. For cell irradiation, a homogeneous 10 × 10 cm2 proton field with an optional spread-out Bragg-peak can be formed. A water-filled phantom was installed that allows for precise positioning of different sample geometries along the proton path. Results Depth-dose profiles within the phantom and dose homogeneity over different cell samples were characterized for the proton beam and the photon reference source. A daily quality assurance protocol was implemented that provides absolute dose information required for significant and reproducible in vitro experiments. Cell survival test experiments were performed to demonstrate the feasibility of such experiments. Conclusion In the experimental room of the University Proton Therapy Dresden, clinically relevant conditions for proton in vitro experiments have been realized. The established cell phantom and dosimetry facilitate irradiation in an aqueous environment and are transferable to other proton, photon and ion beam facilities. Precise positioning and easy exchange of cell samples, monitor unit-based dose delivery, and high beam availability allow for systematic in vitro experiments. The close vicinity to the radiotherapy and radiobiology departments provides access to clinical linacs and the interdisciplinary basis for further translational steps.

Novel Approach to Utilize Proton Beams from High Power Laser Accelerators for Therapy

Protons provide superior radiotherapy benefits to patients, but immense size and cost of the system limits it to only few centers worldwide. Proton acceleration on μm scale via high intensity laser is promising to reduce size and costs of proton therapy, but associated beamlines are still big and massive. Also, in contrast to conventionally accelerated quasi-continuous mono-energetic pencil beams, laser-driven beams have distinct beam properties, i.e. ultra-intense pico-sec bunches with large energy spread and large divergences, and with low repetition rate. With new lasers with petawatt power, protons with therapy related energies could be achieved, however, the beam properties make it challenging to adapt them directly for medical applications. We will present our compact beamline solution including energy selection and divergence control, and a new beam scanning and dose delivery system with specialized 3D treatment planning system for laser-driven proton beams. The beamline is based on high field iron-less pulsed magnets and about three times smaller than the conventional systems, and can provide high quality clinical treatment plans.