In radiation therapy, proton beams may provide higher dose conformity and better sparing of healthy tissue compared to the conventional photon beams, especially by using active beam delivery. But high costs and huge size hinder the wide spread of proton therapy facilities. This limitation can be overcome using proton acceleration by ultra-intense laser pulses. Laser-accelerated beams are characterized by pulses with low repetition rate and peak dose rates exceeding conventional values by several orders of magnitude. Furthermore, these beams have a broad energy spread and large beam divergence. The development of new, optimized techniques for beam transport and dose delivery is required for clinical use. Additionally, animal studies should be performed to continue biological studies, which found no radiobiological difference between laser-accelerated and conventional protons in vitro. Results of an ongoing joint translational research project of several institutions aiming to establish laser-driven proton therapy will be presented.
For translation towards clinical application, an increase of proton energy from 20 to 30 MeV for animal experiments and further to 230 MeV for patient irradiation by increasing the laser power from 150 TW to about 1000 TW is performed in stages. For realization of a compact gantry design supporting active beam delivery the necessary different types of light-weight iron-less high-field pulsed magnets are being developed and tested.
A laser power increase to 500 TW has been successfully demonstrated resulting in proton energies high enough to allow mice studies with laser-accelerated protons, which are currently being prepared. The new gantry design supporting active beam delivery is about 2.5 times smaller than conventional proton gantries. For the realization of the individual beamline elements, the prototypes of a pulsed solenoid and a 45° sector magnet and their combination have been successfully developed and tested. These magnets will also be used in the mice studies with laser-driven protons and for experimental gantry design studies at conventional therapy beamlines.
Substantial progress has been made towards clinical application of promising laser-driven proton therapy although further development is required.
Legal entity responsible for the study
Technical University Dresden
German Government: BMBF, nos. 03ZIK445, 03Z1N511, 03Z1O511 and 03Z1H531.
All authors have declared no conflicts of interest.