Treating tumours

Appl. Phys. B http://dx.doi.org/10.1007/s00340-013-5747-0 (2013)

Maria Nicolai and a team from Germany claim to have conducted the first in vivo irradiation of tumours in mice using laser-accelerated particles. The experiments used the JETI laser system in Jena, Germany. The 40 TW Ti:sapphire laser system was used to generate 30 fs pulses, which provided an energy of ∼700 mJ at the target. Focusing produced a 13-μm-diameter spot that had a very high average intensity of 8 × 10¹⁸ W cm⁻². The target was a 2.4-mm-long supersonic hydrogen gas jet, which was ionized by the laser pulses to produce a plasma with an electron density of ∼10¹⁹ cm⁻³. The electrons were subsequently accelerated and directed to cancerous mice. During a four-week campaign, human tumours grown onto the ears of over 50 mice were treated by bombarding them with a stream of electrons equivalent to prescribed doses of 3 Gy and 6 Gy. The team was able to maintain the threshold dose rate of 1 Gy min⁻¹ for tumour irradiation by increasing the repetition rate of the electron bunches from 0.5 Hz to 1 Hz over the campaign duration. The demonstration shows the feasibility of using laser-accelerated particles for treating tumours.