ESTRO 2021 Abstract Book

S1175

ESTRO 2021

PO-1431 An atlas to measure craniofacial growth and facial asymmetry in childhood cancer suvivors M. Aznar 1 , S. Monaghan 2 , A. Bryce-Atkinson 1 1 University of Manchester, Division of Cancer Sciences, Manchester, United Kingdom; 2 Univiersity of Manchester, School of Medical Sciences, Manchester, United Kingdom Purpose or Objective Radiotherapy can affect bone and tissue growth and may lead to disfigurement in childhood cancer survivors (CCS). However, the exact link between radiation dose and facial asymmetry can be difficult to quantify, partly due to lack of defined standardised measures of internal anatomy. We propose to investigate the use of follow-up MR images in order to better understand the link between 3D dose deposition and subsequent growth / asymmetry. As a first step, this work develops and validates an atlas (descriptive guide) of craniofacial measures to monitor growth and development in CCS using CT and MR images. Materials and Methods A literature search was conducted to establish common anatomical measures of facial asymmetry. Only measures relevant to craniofacial growth that could be clearly defined in 3D imaging were included. Each measure was illustrated in the atlas using CT and T1-weighted MR images of children (see figure). Intra- observer variation was evaluated on 2 paediatric cancer patients (MR and CT) cases. In addition, the atlas was validated by 7 observers, assessing inter-observer agreement for all measures in 3 healthy children (MR images only) as well as the same 2 paediatric cancer patients as for intra-observer assessment (7 scans from 5 cases in total, aged 8 to 10). Standard deviation (SD) of observer measurements was calculated to assess the reproducibility of each measure described in the atlas.

Results 13 papers were found detailing measures considered useful or applicable for this atlas and 21/37 measurements in those 13 papers were selected for evaluation. Reasons for exclusion included poorly defined measures with indeterminate start and end points, similarities to other measures used more frequently in the