Towards laser driven proton therapy of cancer: Status of the Dresden program

Proton beams by their well-confined energy-loss in matter are a promising tool for the improvement of radiotherapy of cancer and are currently under intense medical investigation. Wider clinical use, however, is limited by the complexity and expense of current proton and ion accelerators. Compact laser driven proton therapy accelerators are discussed as a promising alternative, yet require substantial development in reliable beam generation and transport, but also in dosimetric protocols as well as validation in radiobiological studies.
In our talk, we will present the first direct and dose controlled comparison of the radiobiological effectiveness (RBE) of intense proton pulses from a laser driven accelerator with conventionally generated continuous proton beams, showing no dependence of the RBE on the different beam properties [1]. Controlled dose delivery, precisely online and offline monitored for each of the ~ 4000 proton pulses, resulted in an unprecedented relative dose uncertainty of below 10%, using approaches scalable to radiotherapy applications.
In parallel to the development of laser driven proton therapy accelerators, an advancement in instrumentation for laser driven protons is essential. Most importantly, these new diagnostic tools need to speedwise match the repetition rates of state-of-the-art high power laser systems and need to be adapted to the harsh plasma environment of laser based accelerators, not neglecting their fitment to the properties of laser accelerated proton pulses such as the high flux and the broad energy spectrum.
We will present three types of scintillator-based detectors, all being optimized for specific stages of the experimental chain: a one-dimensional space- and energy-resolved detector for online spectral stability control of the acceleration performance [2], a two-dimensional space- and energy-resolved detector for source characterization measurements, and a three-dimensional detector for precise dose verification in a water-equivalent medium with regards to medical quality assurance [3].

[1] K. Zeil, et al.: Dose-controlled irradiation of cancer cells with laser-accelerated proton pulses, Appl. Phys. B (2012)
[2] J. Metzkes, et al.: A scintillator-based online detector for the angularly resolved measurement of laser-accelerated proton spectra, Review of Scientific Instruments, Rev. Sci. Instrum. 83, 123301 (2012)
[3] F. Kroll, et al.: Preliminary investigations on the determination of three-dimensional dose distributions using scintillator blocks and optical tomography, Med. Phys. 40, 082104 (2013)