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discovered 02_2012

FOCUS// The HZDR Research Magazine WWW.Hzdr.DE 20 21 inherent in proton therapy research and development, a new proton therapy facility is currently under construction at the University Hospital campus using as its platform a conventional circular accelerator (see info box, p. 23). Initially, this facility will be used to treat cancer patients who are subjects in clinical trials - all in the interest of furthering the research in this area. Later on, the plan is to also use protons generated by the accelerator as direct reference radiation for an innovative device designed right here in Dresden: a laser-particle accelerator, for application in proton therapy. If accelerating the protons along tracks that measure only a few short micrometers in length proves a success, the facility‘s overall size can be substantially decreased, which in turn helps keep associated costs at bay. To reach a given tumor in the body and unfold their destructive potential, the accelerated protons must give off an energy on the order of 200 megaelectron-volts (MeV) – which corresponds to something like two-thirds the speed of light. Until now, no laser has ever been able to do this; the energy of any laser anywhere maxes out at around 67 megaelectron-volts. But HZDR‘s Ulrich Schramm and his team are not stressing about international competition in the race to develop higher energy lasers, considering their track record already boasts a number of impressive research and developmental feats. HZDR‘s high-performance laser, DRACO, is capable of generating protons and accelerating them along an extremely short path of less than ten micrometers (by comparison, the thickness of a single human hair measures roughly ten times that value). At this point, following two rounds of experiments, DRACO has shown that cancer cell irradiation using a laser accelerator is definitely possible. What‘s more, for the first time ever, we are dealing with a highly controlled form of radiation that, in the future, could potentially be used to treat cancer patients. Although a number of international researchers are currently working on developing laser- accelerated particles for clinical application, so far only the Dresden research team is in a position to actually produce and monitor laser-generated proton beams that can be targeted to cancer cells at just the right dose – no more and no less. This is important because the new rays are highly precise and therefore make for a uniquely potent anti-cancer weapon. What is important is to ensure at all costs that they give off their energy only once inside the tumor and not as they are traveling through healthy tissue. The Dresden team of laser- based particle therapy developers around Jörg Pawelke and Ulrich Schramm are careful to make sure that this is the case, seeing as their long-term concern lies with the cancer patient. Jörg Pawelke, who heads one of the OncoRay Center‘s research teams, is in charge of supervising the applied proton radiation dose. Current experiments are performed on cells from the SKX cell line taken from a tumor of the head and neck region. These cells are highly sensitive to radiation. LASER SMARTIES: Using a model, PhD student Florian Kroll explains the principle of laser-based particle acceleration during the 2012 “Dresden Long Night of the Sciences“ event. Image credit: Stephan Floss