Abstract
<h3>Objectives</h3> Image-based data mining (IBDM) is a novel technique to identify dose-response relationships (DRRs) in radiotherapy. IBDM comprises two steps: spatial normalisation of patient data to a reference anatomy using deformable image registration, and ‘per-voxel' dose comparison. The main advantage of IBDM is the possibility of identifying DRRs at the sub-organ level and in structures that are not routinely contoured, depending on the image registration accuracy. Computed Tomography (CT)-based IBDM has been successfully applied in adults; however, for children with brain tumours, Magnetic Resonance (MR) imaging is indicated due to superior anatomical definition. We evaluate the accuracy of spatial normalisation using MR images to determine the feasibility of MR-based IBDM in children with brain tumours. <h3>Methods</h3> We used MR images and radiotherapy contours from 129 children previously treated on the SJMB03 protocol for medulloblastoma. The patient with the median brain volume was selected as the reference anatomy for deformable image registration (NiftyReg software). We analysed registration accuracy, comparing each patient's deformed contours to the reference contours, in 5 brain structures (Table 1) via 95%-Hausdorff (HD95%), average-contour (MeanDTA) and centre-of-mass (CoM) distances. Based on previous results in CT data, meanDTA accuracy <3mm was considered acceptable. <h3>Results</h3> 16/129 cases required manual adjustments to fix registration errors, commonly arising due to enlarged ventricles or large rotations compared to the reference anatomy. MeanDTA for all structures was <2.1mm and all metrics <6mm (Table 1). <h3>Conclusion</h3> Accurate spatial normalisation was achieved using MR images from paediatric brain tumour patients, suggesting that MR-based IBDM is feasible in this patient group.
Published Version
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