## 5 Conclusions  
This study compared the clinical performances between RaySearch Laboratories AB RayStation DL auto-contouring model, RSL Head and Neck CT 2.0.0.47 and its atlas-based auto-contouring software, ANACONDA for 16 OARs segmentation in the head and neck RT with the manual contouring as the reference. Its results show that the DL auto-contouring model was more accurate and required less contouring time when compared with the atlas-based auto-contouring tool. The DL auto-contouring approach could achieve more consistent performance in the OARs segmentation than the atlas-based approach, resulting in statistically significant reduction of the time required for the whole segmentation process by 40%. Additionally, the DL auto-contouring had statistically significantly higher mean DSC and lower HD and HD95 values for 10 out of 16 OARs, namely brain stem, left and right eyes, left and right lens, left and right optic nerves, left and right parotid glands, and pituitary. These outcomes are particularly important for addressing the major issues of the manual contouring, namely inter- and intra-operator variabilities and labor-intensiveness in head and neck RT. However, for future studies, more radiation oncologists and head and neck cancer datasets with greater varieties should be used to evaluate the performances (in terms of contouring time, geometric accuracy and associated dosimetric impact) of multiple atlas-based, pre-trained and trained DL auto-contouring tools in contouring a great number of OARs. Comparison of performances of RaySearch Laboratories DL and atlas-based auto-contouring tools in contouring both CTVs and OARs for other cancer types such as breast cancer should be conducted as well.  
Conceptualization, C.K.C.N., V.W.S.L. and R.H.M.H.; methodology, C.K.C.N., V.W.S.L. and R.H.M.H.; software, V.W.S.L.; validation, C.K.C.N., V.W.S.L. and R.H.M.H.; formal analysis, C.K.C.N., V.W.S.L. and R.H.M.H.; investigation, C.K.C.N., V.W.S.L. and R.H.M.H.; resources, C.K.C.N., V.W.S.L. and R.H.M.H.; data curation, R.H.M.H.; writing--original draft preparation, C.K.C.N., V.W.S.L. and R.H.M.H.; writing--review and editing, C.K.C.N., V.W.S.L. and R.H.M.H.; visualization, C.K.C.N., V.W.S.L. and R.H.M.H.; project administration, C.K.C.N.; funding acquisition, C.K.C.N. and V.W.S.L. All authors have read and agreed to the published version of the manuscript.  
This research was funded by The Hong Kong Polytechnic University Large Equipment Fund for Teaching 2020/21, grant number HTI-4.  
The study was conducted in accordance with the Declaration of Helsinki, and approved by the Human Research Ethics Committee of Curtin University (approval number: HRE2022-0582 and date of approval: 18 October 2022), Institutional Review Board of The Hong Kong Polytechnic University (approval number: HSEARS20220815001 and date of approval: 7 October 2022), and Research Ethics Committee of Hong Kong East Cluster of Hospital Authority of Government of Hong Kong Special Administrative Region (approval number: HKECREC-2022-054 and date of approval: 6 October 2022).  
Patient consent was waived due to the retrospective nature.  
The datasets used in this study are not publicly available due to strict requirements set out by the Research Ethics Committee of Hong Kong East Cluster of Hospital Authority of Government of Hong Kong Special Administrative Region.  
The authors would like to thank [PERSON] for her assistance with the collection of data from Department of Clinical Oncology, Pamela Youde Nethersole Eastern Hospital, Hong Kong Special Administrative Region.  
The authors declare no conflict of interest. The funder had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.