Functional target volume delineation for radiation therapy on the basis of positron emission tomography and the correlation with histopathology

Accurate target volume delineation becomes more and more important for modern high-precision radiotherapy. During the last years, molecular imaging using positron emission tomography (PET) has been shown to be of high clinical impact on diagnosis, staging and/or restaging of many malignancies. Therefore, the integration of PET-data into the radiotherapy planning process is of high interest in radio-oncology. During the last years a number of automatic and semi-automatic PET-based volume delineation methods have been developed which will be presented in this review. We will not only describe those algorithms currently used in clinical settings, but also present some of the latest developments in this highly dynamic field of research. Furthermore, validation of different segmentation approaches against histopathology is discussed.