title: Histopathological correlation of (11)C-choline PET scans for target volume definition in radical prostate radiotherapy.
abstract: OBJECTIVE
  To evaluate the accuracy of (11)C-choline PET scans in defining dominant intraprostatic lesions (DILs) for radiotherapy target volume definition.
  
  
  METHODS
  Eight men with prostate cancer who had (11)C-choline PET scans prior to radical prostatectomy were studied. Several methods were used to contour the DIL on the PET scans: visual, PET Edge, Region Grow, absolute standardised uptake value (SUV) thresholds and percentage of maximum SUV thresholds. Prostatectomy specimens were sliced in the transverse plane and DILs were delineated on these by a pathologist. These were then compared with the PET scans. The accuracy of correlation was assessed by the Dice similarity coefficient (DSC) and the Youden index.
  
  
  RESULTS
  The contouring method resulting in both the highest DSC and the highest Youden index was 60% of the maximum SUV (SUV(60%)), with values of 0.64 and 0.51, respectively. However SUV(60%) was not statistically significantly better than all of the other methods by either measure.
  
  
  CONCLUSIONS
  Although not statistically significant, SUV(60%) resulted in the best correlation between (11)C-choline PET and pathology amongst all the methods studied. The degree of correlation shown here is consistent with previous studies that have justified using imaging for DIL radiotherapy target volume definition.
authors: Radiation Oncology Centre, Austin Health, Victoria, Australia.
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