title: 18F-fluorocholine PET-guided target volume delineation techniques for partial prostate re-irradiation in local recurrent prostate cancer.
abstract: OBJECTIVE
  We evaluate the contribution of (18)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.
  
  
  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 of (18)F-fluorocholine, dynamic PET frames (3 min each) were reconstructed from the list-mode acquisition. Five PET image segmentation techniques were used to delineate the (18)F-choline-based GTVs. These included manual delineation of contours (GTV(man)) 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 (GTV(40%) and GTV(50%)), signal-to-background ratio-based adaptive thresholding (GTV(SBR)), and a region growing (GTV(RG)) 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 for (18)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.
authors.affiliation: Service of Radiation Oncology, Geneva University Hospital, Geneva, Switzerland.
authors.forename: Hui
authors.initials: H
authors.lastname: Wang
authors.forename: Hansjörg
authors.initials: H
authors.lastname: Vees
authors.forename: Raymond
authors.initials: R
authors.lastname: Miralbell
authors.forename: Michael
authors.initials: M
authors.lastname: Wissmeyer
authors.forename: Charles
authors.initials: C
authors.lastname: Steiner
authors.forename: Osman
authors.initials: O
authors.lastname: Ratib
authors.forename: Srinivasan
authors.initials: S
authors.lastname: Senthamizhchelvan
authors.forename: Habib
authors.initials: H
authors.lastname: Zaidi
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002794:Choline / Q000031:analogs & derivatives*; D005462:Fluorine Radioisotopes; D006801:Humans; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000532:radiotherapy*; D049268:Positron-Emission Tomography; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D019275:Radiopharmaceuticals; D011879:Radiotherapy Dosage; D014057:Tomography, X-Ray Computed
chemical_list: D005462:Fluorine Radioisotopes; D019275:Radiopharmaceuticals; C514960:fluorocholine; D002794:Choline