ESTRO 2022 - Abstract Book

S699

Abstract book

ESTRO 2022

OC-0780 Parametrization of artery delineation and nationwide implementation in the DBCG RT Nation cohort

E.R. Skarsø 1 , L. Hindhede Refsgaard 1 , T. Ravkilde 2 , H. Dahl Nissen 3 , M. Berg 3 , K. Boye 4 , C. Kamby 5 , K. Jakobsen 6 , M. Olesen 6 , B. Vrou Offersen 1,2,7 , S.S. Korreman 1,2,7 1 Aarhus University Hospital, Department of Experimental Clinical Oncology, Aarhus N, Denmark; 2 Aarhus University Hospital, Department of Oncology, Aarhus N, Denmark; 3 Vejle Hospital, University Hospital of Southern Denmark, Department of Oncology, Vejle, Denmark; 4 Copenhagen University Hospital, Rigshospitalet, Department of Oncology, Copenhagen, Denmark; 5 Copenhagen University Hospital - Rigshospitalet, Department of Oncology, Copenhagen, Denmark; 6 Zealand University Hospital, Department of Clinical Oncology and Palliative Care, Næstved, Denmark; 7 Aarhus University Hospital, Danish Center for Particle Therapy, Aarhus N, Denmark Purpose or Objective Delineation of structures of limited visibility and small size is prone to large uncertainties. With adaptive treatment planning and automatic delineation making its entry in clinical routine, it is desirable to have a framework for quality assurance (QA) of delineation of such structures. In this study we develop a parameterization of left anterior descending coronary artery (LADCA) delineation. We test the method in a national dataset. Materials and Methods We included structure delineations from 4598 danish high-risk breast cancer patients treated with adjuvant radiotherapy across the nation during 2008-2017. A national LADCA delineation guideline was published in 2013. The coordinate sets of the individual delineations were exported and analysed in python (v 3.9.6). LADCA was parameterized using metrics describing volume, cranial-caudal (CC) length, the cumulative length, width, anterior-posterior and lateral-medial consistency between slices, missing structure slices and number of patients with delineations. The cumulative length was determined by summing the vector-distance between consecutive centroid points in all CT slices. The x and y centroid values were calculated by averaging all x- and y-coordinates respectively. If the distance between two adjacent centroid points was > 80 mm, the point was removed from the calculation as an outlier. The width was determined by scaling the horizontal width by cos( ), where is the angle between the horizontal and scaled width, Figure 1. Results were stratified by year and treating center. Significance was tested with the Mann-Whitney U-test. Results The automatic method was successfully used in all patients included in the Danish Breast Cancer Group (DBCG) RT Nation cohort. In total 2018 (44%) of patients had LADCA delineated. Distribution per center including number of missing slices is shown below. # patients included (% of total # patients) # patients with LADCA delineations (% of total # LADCA delineations) Total # missing slices Center 1 1132 (25%) 579 (29%) 31 Center 2 922 (20%) 320 (16%) 5 Center 3 1802 (39%) 676 (33%) 20 Center 4 742 (16%) 443 (22%) 54 In the period around the implementation of national delineation guidelines (2012-2014), the differences between the centers were smallest, Figure 2. For mean width there was a significant difference between centers in the periods 2008- 2012 and 2014-2017 (p<0.001). For CC length, no significant differences were found between center 2 and 3 (2011-2016). Center 4 differed significantly from the other centers in CC length in the periods 2010-2011 and 2015-2017 (p<0.001).