X-rays can provide much more than radiography for diagnosing bone fractures or internal disease. In the form of high-energy photon beams, cancer can be treated by exposing tumors to a strong dose of targeted radiation. This type of radiation therapy is currently one of the most important treatment methods for cancer; about half of all tumor patients are now treated with photon or particle beams. The novel, interdisciplinary SPARTA project commenced on April 1, 2013 to improve this method by using modern software technology to support tumor radiation in a more effective and patient-friendly fashion than existing methods.
When a clinician treats a tumor near a sensitive tissue structure such as nerves or organs, special 'intensity-modulated' radiation therapy is applied. Instead of exposing a tumor to several relatively wide and strong photon beams, many individually dosed partial beams from different directions coincide. Because these beams are targeted to overlap in the tumor, the highest dose is only attained at this location. Ideally, the surrounding healthy tissue remains only marginally affected.
In practice, however, this method is somewhat limited because a single application of such radiation has very little effect. Over a series of weeks, patients undergo about 30 treatments. During this time, the patient's body can change because of differences in tumor size or loss or gain in body weight. These changes affect the position of the tumor and thus the target of the radiation. This increases the risk that beams partially miss the tumor and instead damage healthy tissue.
In addition, breast and abdominal tumors present a further problem. Because the patient breathes during radiation, the tumor inevitably shifts. To reach the tumor despite this motion, the clinician must select a relatively large target area, thereby damaging more healthy surrounding tissue than necessary.
This is where SPARTA comes into play. In this research project, scientists from ten different fields develop novel, adaptive, expandable software systems to support clinicians during planning and application of radiation therapy. The overarching aim of SPARTA is to make radiation therapy more efficient, safe, and effective using these novel systems. The project goals include:
Computer-supported imaging and sensor systems should precisely measure when and how the anatomy of the patient changes both over the weeks of the treatment and during the radiation. The systems should determine the patient's precise position and monitor patient movements such as breathing. Exact measurement of the individual variations is a requisite for optimally adapting the radiation therapy to each patient.
The software should compare the original radiation plan to variations that arise between or during treatment sessions, allowing clinicians to determine whether radiation has indeed reached the planned target. In addition, the program should reliably estimate the cumulative dose that the tumor has received after a certain number of treatments, allowing better judgment of sufficient tumor radiation.
SPARTA is developing a program that can judiciously adapt a radiation plan to measured changes or even to expected variations between and during each patient's treatments. How pronounced and regular are the breathing movements, and do these impact the movement of the target region? This information should be incorporated into each radiation plan before each treatment and provide increased accuracy. In addition, planning should become 'adaptive', capable of simple and flexible adjustment during the course of therapy in case the tumor shifts due to patient weight loss or small changes in body position. This provides increased assurance that the planned radiation dose reaches the tumor and damages as little surrounding tissue as possible.
To plan the complete radiation, patients currently undergo computer tomography. This allows doctors to determine the position of a tumor accurately, but its structure only to a limited extent. Which parts are still active and which are already necrotic? This information is important because only the active region of a tumor must be radiated, not the inactive. These details can be determined through special procedures such as magnetic resonance imaging (MRI) or positron emission tomography (PET). SPARTA researchers aim for a systematic investigation of the uses of such procedures for more precise multimodal radiation planning.
About the SPARTA Project:
SPARTA stands for "Software Platform for Adaptive Multimodal Radio and Particle Therapy with Autarkic Extendibility." The project is funded by the German Federal Ministry of Education and Research with a contribution of almost eight million euro. It commences on April 1, 2013 and will run for three years. The consortium consists of ten partners, including research institutes, medical technology companies, and university hospitals.