18 F-fluorocholine PET-guided target volume delineation techniques for partial prostate re-irradiation in local recurrent prostate cancer

• Published in: Radiotherapy and oncology 2009, Vol.93 (2), p.220-225
• Main Authors: Wang, Hui, Vees, Hansjörg, Miralbell, Raymond, Wissmeyer, Michael, Steiner, Charles, Ratib, Osman, Senthamizhchelvan, Srinivasan, Zaidi, Habib
• Format: Article
• Language: English
• Subjects: Hematology, Oncology and Palliative Medicine
• ISSN: 0167-8140
• DOI: 10.1016/j.radonc.2009.08.037

Abstract Background and purpose We evaluate the contribution of18 F-choline PET/CT in the delineation of gross tumour volume (GTV) in local recurrent prostate cancer after initial irradiation using various PET image segmentation techniques. Materials and methods Seventeen patients with local-only recurrent prostate cancer (median = 5.7 years) after initial irradiation were included in the study. Rebiopsies were performed in 10 patients that confirmed the local recurrence. Following injection of 300 MBq of18 F-fluorocholine, dynamic PET frames (3 min each) were reconstructed from the list-mode acquisition. Five PET image segmentation techniques were used to delineate the18 F-choline-based GTVs. These included manual delineation of contours (GTVman ) by two teams consisting of a radiation oncologist and a nuclear medicine physician each, a fixed threshold of 40% and 50% of the maximum signal intensity (GTV40% and GTV50% ), signal-to-background ratio-based adaptive thresholding (GTVSBR ), and a region growing (GTVRG ) algorithm. Geographic mismatches between the GTVs were also assessed using overlap analysis. Results Inter-observer variability for manual delineation of GTVs was high but not statistically significant ( p = 0.459). In addition, the volumes and shapes of GTVs delineated using semi-automated techniques were significantly higher than those of GTVs defined manually. Conclusions Semi-automated segmentation techniques for18 F-choline PET-guided GTV delineation resulted in substantially higher GTVs compared to manual delineation and might replace the latter for determination of recurrent prostate cancer for partial prostate re-irradiation. The selection of the most appropriate segmentation algorithm still needs to be determined.