Automatic segmentation of tumour volume for non-small cell lung cancers with the 18F-FDG PET-CT for treatment by radiotherapy

Purpose. - Radiotherapy belongs to the treatment of certain stages of non-small cell lung cancer. It requires a preliminary delimitation of the tumour by the radiotherapist with a contouring of the tumour on the CT but this method does not take into account the biological characteristics of the target and remains dependent on the operator. To optimize the irradiation volume, several teams created methods of automatic segmentation on the PET-CT, still under evaluation. Material and methods. - We undertook a retrospective study on 17 patients to evaluate the difference between obtained volumes by CT delimitation with those deduced by three algorithms of automatic segmentation based on PET-CT (Black et al., Nestle et al. and Tylski et al.). A confrontation with histological tumoral volume has been carried on in case of surgery. Results. - On average, the three methods under evaluated tumoral volume compared to the CT of 8% for Nestle et al., 22% for Black et al. and 30% for Tylski et al., but these results hide disparities, which tended to decrease with a grouping of tumours by size. The most important differences were due to heterogeneous uptake of FDG (necrosis, spicules, atelectasis). Conclusion. - The method of Black et al. was the most discrepant one. For tumours less than 45 cm;, Nestle's et al. algorithm tends to overestimate the CT volume and thus makes it possible to integrate safety margins into final volume (microscopic extension). The method of Tylski et al. presents an interesting approach (correction of partial volume effect) but still requires developments because it under evaluates too much the target volume. (C) 2009 Elsevier Masson SAS. All rights reserved.