On the feasibility of automatic detection of range deviations from in-beam PET data

In-beam PET is a clinically proven method for monitoring ion beam cancer treatment. The objective is predominantly the verication of the range of the primary particles. Due to dierent processes leading to dose and activity, evaluation is done by comparing measured data to simulated. Up to now, the comparison is performed by well trained observers (clinicians, physicists). This process is very time consuming and low in reproducibility. However, an automatic method is desirable. A one dimensional algorithm for range comparison has been enhanced and extended to three dimensions. System inherent uncertainties are handled by means of a statistical approach. To test the method a set of data was prepared. Distributions of +-activity calculated from treatment plans were compared to measurements performed in the framework of the German Heavy Ion Tumor Therapy Project at GSI Helmholtz Centre for Heavy Ion Research Darmstadt, Germany. Articial range deviations in the simulations served as test objects for the algorithm. Range modications of dierent depth (4 mm, 6mm and 10mm water equivalent path length) can be detected. Even though sensitivity and specicity of a visual evaluation is higher, the method is feasible as basis for the selection of patients from the data pool for retrospective evaluation of treatment and treatment plans and correlation with follow up data. Furthermore, it can be used for the development of an assistance tool for a clinical application.