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Introduction: Paediatric patients (individuals below 18 years of age) requiring cranial-spinal irradiation (CSI) at our institution are commonly planned and treated using a three isocentre (3-ISO) volumetric modulated arc therapy (VMAT) technique. A modified two isocentre (2-ISO) VMAT technique was investigated with the aim to improve workflow and reduce planning and treatment time. Methods: Five CSI paediatric patients previously treated with a 3-ISO VMAT technique were retrospectively replanned using a 2-ISO VMAT technique. The 2-ISO VMAT plans were reviewed and approved by a radiation oncologist (RO) before undergoing patient-specific quality assurance (QA) procedures, performed by a radiation oncology medical physicist (ROMP). Planning target volume (PTV) coverage, organ-at-risk (OAR) dose as well as planning and treatment durations of the first five patients utilising 2-ISO technique were compared with 3-ISO technique. Results: The average percentage difference in PTV coverage by 95% reference dose between the 2-ISO and 3-ISO is 0.14%, and the average difference in OAR median dose is 0.68 Gy. Conformity and homogeneity indices have the same averages at 1.18 and 0.4 respectively. Patient-specific physics QA results were all comparable with the 3-ISO averages at 98.84% and the 2-ISO at 98.71%. Planning duration for the 2-ISO was reduced by up to 75%, and daily treatment duration was reduced by up to 50%. Of all the previously treated CSI patients using a 3-ISO technique, 45% were suitable for the 2-ISO technique. Conclusion: The 2-ISO VMAT technique provided comparable dose distribution based on PTV coverage, OAR dose and plan metric indices. Reduced planning and treatment duration with the 2-ISO technique facilitated improved workflow with decreased sedation time for paediatric patients requiring a general anaesthesia.

A novel radiotherapy outlining application uses a small number of user-assigned points across orthogonal planes to generate a mesh which is then edited across multiple slices using innovative three-dimensional (3D) sculpting tools. This paper presents the results of a bladder outlining study that compared times and volumes for the new tool with those of a conventional manual outlining tool. All students undertaking their first University radiotherapy planning module were invited to participate. Following training, they performed a timed outlining of the same male bladder dataset and provided feedback on their preferred method. Comparison of times from the resulting ten datasets demonstrated that the 3D segmentation tool was significantly faster than conventional software with a mean time of 11·9 minutes compared with 19·2 minutes (p=0·03). The users expressed a preference for the new tool (eight users) over the conventional outlining software (two users). A minimal point 3D volumetric manual outlining tool utilising orthogonal computed tomography planes demonstrated significant time saving for bladder segmentation compared with axial-based outlining within a group of novice outliners. Future work aims to establish the role of the 3D multi-slice sculpting tools in editing of auto-segmentation derived contour sets.

Introduction A 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. Methods Three 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. Results Radiation 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. Conclusion This 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.

Many papers have identified concerns about intraobserver variability of repeat outlining by the same clinician. These variations in individual performance in turn make it challenging to determine values for interobserver variability since these depend largely on the assumption that each observer's outline is accurate. Aside from the concerns about inaccuracy, variability is a potential component of the planning target volume margin and thus minimization of this has the potential to reduce normal tissue dose and morbidity. One accepted measure of intraobserver agreement since 1960 has been the Kappa (k) correlation coefficient, which varies from 0 (agreement by chance) to 1 (full agreement). The accepted subdivisions of kappa are “excellent” (0.81–1.00), “good” (0.61–0.80), “moderate” (0.41–0.60), “fair” (0.21–0.40), and “poor” (0–0.20). It is clear from the evidence base that kappa is common to many aspects of medical practice. Despite the kappa assumptions concerning observer independence , it has been used extensively to report both intraobserver and interobserver variability in the interpretation of CT imaging data. Table 1 summarizes the results of these studies from the last 10 years.

The novel three-dimensional (3D) radiotherapy interactive outlining tool allows volumes to be created from a handful of points within axial, sagittal and coronal planes. 3D volumetric visualisation allows users to directly manipulate the resulting volume using innovative-sculpting tools. This paper discusses the development and initial evaluation of the software ahead of formal clinical testing. User feedback was collated as part of the software development phase to ensure clinical suitability, define user training strategies and identify best practice. A loosely structured format was adopted with leading descriptive questions aiming to generate suggestions for improvements and initiate further discussion. The four participants reported great satisfaction and value in being able to use all three planes for outlining, although orientation in 3D was evidently a problem. All participants felt that the software was capable of producing acceptable outlines rapidly and that the multi-planar capability allowed for improved outlining of the prostate apex. Mesh generation from a small number of points placed on a range of planes is a rapid and effective means of target delineation. Multi-slice volume sculpting and 3D orientation is challenging and may indicate a need for a paradigm shift in anatomy and computed tomography training.