In the middle of the human body, for a split second, a flash of light strikes. Not a rough beam from a distance, but a precise, lightning-fast spark that strikes only where it is supposed to. No thunder, no visible spectacle. Just a minimally invasive procedure and a tumor that is hit directly while the surrounding tissue remains unharmed. This image visualizes one of the great hopes of modern radiotherapy: a treatment applied directly to the tumor, as precise and brief as a lightning bolt, instead of a series of external irradiations. This is exactly what researchers at KIT together with the German Cancer Research Center (DKFZ) are working on. In the project “Ultracompact Electron Accelerators for Internal Radiotherapy” (UCART), they are developing hair-fine electron accelerators that generate endoscopic ultra-short pulses right next to the tumor.
Radiotherapy is indispensable for most cancer patients, but it has its limits. Two-thirds of all patients receive radiation at some point during the course of their cancer treatment, and the trend is rising. Today´s devices are large, heavy, expensive and cannot be used everywhere. A linear accelerator, as found in hospitals, requires significant concrete shielding, a stable power supply, specially trained staff and several million euros of investment. Even considering the most widespread of those instruments of treatment, there are only around 15,000 such installations worldwide, but roughly 80,000 would be needed to provide adequate treatment for all patients. Added to this is the fundamental problem of the classic treatment method: the radiation must travel from the outside through healthy tissue to reach the tumor. Each session therefore puts unnecessary stress on the body, causes side effects and lengthens treatment. This burden follows many patients not only physically but also psychologically for weeks. It quickly becomes clear that conventional methods are reaching their limits.
Rather than developing a technical concept first and then looking for an application, the project team led by Prof. Dr. Anke-Susanne Müller from the Institute for Beam Physics and Technology (IBPT) at KIT chose a different approach. The institute director recalls: “The collaboration with the German Cancer Research Center and the Heidelberg Ion Beam Therapy Center came about through a joint application. We asked ourselves where and how we could make a difference with our knowledge. Above all, it was important to us not to do this separately, but to work together with the medical community from the outset in order to achieve an impact later on.” Already during the planning stage, they are considering which types of tumors are reachable, how an endoscope would have to be guided and how patients can benefit. No laboratory bubble, but co-creation from day one – physics and medicine in direct exchange, not as successive disciplines. The research partners´ goal: an ultra-compact electron accelerator that does not irradiate from the outside, but acts directly inside the body.
The idea is astonishingly simple yet highly complex: An accelerator system measuring just a few millimeters is guided directly to the tumor via an endoscope. There it generates an ultra-short electron pulse – a tiny, controlled flash that hits only the tumor and spares the surrounding tissue. No continuous beam, but a selective energy input in the millisecond range. The underlying technology sounds like science fiction: A gas is ionized, forming a plasma that creates extremely strong electric fi elds. In this temporary structure, the electrons are accelerated within a microscopically short distance. Where conventional systems require meters, a fraction of a millimeter suffi ces here. The energy source? A laser pulse – millions of times more effi cient than large devices. The result: high-tech that is more accessible, fl exible and patientcentred. UCART operates without permanent radioactive sources and the system can be switched on and off. No shielded chambers, no specialized staff. The patient themselves essentially become the shielding and the treatment could take place in an ordinary practice. This also has psychological advantages: no enclosed room, no endless waiting, no feeling of isolation.
The researchers have already reached important milestones: the electron distribution for the ultrashort pulses can be generated precisely and fi rst irradiation profi les have been simulated and tested in treatment plans. A proof of principle shows that the system works theoretically and practically in simulation. Next steps are miniaturization and practical implementation. This includes designing the tiny accelerators so that they can be reliably integrated into an endoscope, incorporating all necessary components and making them manageable for clinical staff. In parallel, researchers are evaluating which tumors are particularly suitable for safe, targeted treatment.
UCART is not only intended to work in simulations, but later to be used in clinical practice. The goal is a scalable, energy-efficient and patient-friendly system – a precision tool that makes radiotherapy more accessible, gentler and more flexible, without reliance on large infrastructure. To achieve this, researchers are working closely with the medical and industrial sectors. “Surprisingly, the watch making industry is also helping us,” says Müller. Precision engineering that is normally used for the micromechanics of high-quality timepieces, is applied here in an extremely small space. Radiotherapy has long been an uncontrolled natural pheno menon, a continuous bombardment that affects both tumors and healthy tissue. UCART wants to reverse that storm. A tiny, precise lightning strike directly at the tumor as the start of a new era of cancer therapy: gentler, more patientcentred and accessible to more people.
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Development of ultra-compact, light-driven electron accelerators for more efficient radiotherapy of cancer patients
In-situ applications for endoscopic ultra-short electron pulses delivered directly at the tumor to spare healthy tissue and reduce side effects
Institute for Beam Physics and Technology (IBPT) at KIT,German Cancer Research Center (DKFZ), funded by the Carl Zeiss Foundation
