Reply to the comments on "comparative study with new accuracy metrics for target volume contouring in PET image...

This communication is submitted in response to the letter of van den Hoff and Hofheinz (2013). Based on findings in their earlier study (Hofheinz , 2010) the letter criticizes the use of a physical positron emission tomography (PET) phantom with "cold wall" volumes of interest, in part of the evaluation of PET segmentation tools in our experiment reported in this issue (Shepherd , 2012). In addition, the letter raises concerns about the low number of independent expert (manual) delineations used in Shepherd , (2012) to assess accuracy of tumor segmentation in patient images, and disambiguates the details of one of the segmentation methods involved in Shepherd , (2012).