IntroductionA novel 3D volumetric segmentation tool allows the user to outline using a small number of points on a range of planes. Unique 3D volumetric “sculpting” tools enable editing of the resulting structures across multiple slices concurrently. This article reports the results of radiation oncologists' preclinical evaluation of the tool. MethodsThree clinicians outlined prostate and seminal vesicles on 14 data sets using the traditional slice-by-slice method and the new 3D tool. The project gathered focus-group feedback to gather rich data relating to clinician perceptions of the new 3D outlining paradigm. Emergent themes were identified and categorised for discussion. ResultsRadiation oncologists reported high levels of satisfaction with the outlines arising from both paradigms. The volumetric sculpting was a challenge, but participants enjoyed using points in orthogonal planes and felt that the paradigm had potential value in terms of speed and smooth volume creation. ConclusionThis study has demonstrated that a 3D volumetric outlining system is felt to have potential value by radiation oncologists for accelerating clinician-directed prostate and seminal vesicle segmentation. The new tool was well-received and reported to be capable of producing very rapid and smooth volumes. The novelty of the approach required significant training input and a radically different approach of minimal point placement. Further testing of this software with a less time-poor cohort may be indicated to gain reliable quantitative data relating to the impact on segmentation time.