Design Studies for Laser-Driven Ion Beam Radiotherapy Units

The majority of radiation treatments for tumors in humans is currently done by high-energy x-ray beams generated by clinical linear electron accelerators. Within the last decade, the clinical interest in high-energy proton or ion beams as a promising alternative has risen clearly. Compared to the standard x-ray treatment, particle therapy can deliver better dose distributions with less dose burden in normal, healthy tissue. However, the required technology for particle acceleration and beam lines is complex and costly. As a consequence, this type of therapy is limited to a few centers worldwide only. Employing compact laser-based particle sources could change this dramatically, and provide particle therapy to a broader range of patients.

The greatest advantage of laser-driven ion beam radiation therapy (L-IBRT) units compared to conventional technology could be a compact gantry that does not need large and heavy bending magnets to deflect the particle beam. Instead, the laser beam would be guided by mirrors through a compact gantry structure to hit the target in the treatment head relatively close to the patient. Between the laser target and the patient a short particle beam line including magnetic components will still be necessary to focus the beam, to remove unwanted particle species or energies, and to provide patient safety and treatment monitoring features. Depending on the generated energy spectrum, it might be necessary to use a full energy selection system, which requires considerable space and careful shielding of secondary radiation. If, on the other hand, a (nearly) monoenergetic spectrum with controllable fluence and energy is initially produced, a more compact device could be envisaged. In this case it might be possible to build a treatment unit that is not much larger than the machines currently used clinically in radiotherapy with photon beams. Today, there are not even prototypes of L-IBRT systems available. In this project within the MAP cluster, we are working on preliminary design studies for such novel treatment units, which in turn define the clinical requirements for the application of laser based particle acceleration in medicine. Another important aspect is the integration of advanced imaging modalities (e.g. phase contrast imaging using laser-generated brilliant x-rays) into a treatment unit that combines diagnostic and therapeutic components.