Development of atlas-based auto-segmentation and knowledge-based treatment planning for radiotherapeutic palliation of spine metastases

Abstract

Purpose: Uncomplicated spine metastases are routinely treated with conventional external beam radiotherapy (cEBRT). In cEBRT, there is no delineation of target volumes or organs at risk (OAR), and no attempt to optimise the dose distribution. An automated solution for conformal radiotherapy treatment planning through the development, validation and evaluation of atlas-based auto-segmentation (ABAS) for delineation of target volumes and OAR and volumetric-modulated arc therapy (VMAT) knowledge-based planning (KBP) for conformal radiotherapy is described here. Materials and Methods: A SmartSegmentation atlas has been developed and evaluated to provide ABAS of the thoracic and lumbar vertebral spine and OAR. A RapidPlan model has been developed and validated for VMAT KBP. The application of both for conformal radiotherapy treatment planning has been compared with the equivalent dose distributions for cEBRT. Results: Planning target volume (PTV) coverage for VMAT KBP was superior to cEBRT. With PTV Dmean=7.86+/-0.16Gy, Dmin=3.46+/-1.79Gy, Dmax=8.56+/-0.05Gy for RapidPlan generated plans compared to Dmean=7.78+/-0.24Gy, Dmin=1.83+/-1.08Gy, Dmax=10.46+/-0.41Gy for cEBRT. Homogeneity index and conformity index were 0.236+/-0.215 and 1.201+/-0.121 respectively for RapidPlan generated plans compared to 0.508+/-0.137 and 1.789+/-0.437 for cEBRT. Dose to spinal cord and cauda equina was reduced for RapidPlan generated plans, with Dmax of 7.91+/-0.16Gy and 7.94+/-0.13Gy respectively compared to 8.67+/-0.13Gy and 8.90+/-0.16Gy for cEBRT. Discussion: ABAS of the vertebral spine and OAR had varying degrees of success, but was sufficient for application of VMAT KBP to provide conformal treatment plans for uncomplicated spine metastases. RapidPlan generated plans were superior to cEBRT in terms of target coverage, homogeneity and conformity and was achievable in a clinically acceptable time, with improved sparing of the spinal cord and cauda equina. Conclusion: Implementation of ABAS and VMAT KBP is feasible in the clinical environment. Further work is required to establish a truly automated conformal radiotherapy treatment planning solution for uncomplicated spine metastases.

Date of Award	31 Dec 2022
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Julia-Claire Handley (Supervisor) & Chris Golby (Supervisor)