Abstract
Abstract BACKGROUND Accurate and repeatable imaging segmentation of glioblastomas is important for effective radiomics modelling of clinical endpoints such as survival and treatment response. Manual and even automated segmentation are prone to variability. The primary objective of this study is to evaluate the repeatability of manually segmented glioblastomas on MRI which will serve as quality assurance for a quantitative MRI radiomics repeatability study. METHODS MRI datasets from n=19 patients with recurrent glioblastoma extracted from The Cancer Imaging Archive (RIDER Neuro MRI dataset) comprised of test-retest scans (time-point 1 and 2) acquired on average 2 days apart. The MRI protocol consisted of dynamic contrast-enhanced 3D FLASH using 0.1mmol/kg Magnevist intravenous injection at 3cc/second (TR 3.8ms, TE 1.8ms, 5mm slices, flip angle 25°), contrast-enhanced 3D FLASH (TR 8.6ms, TE 4.1ms, 1mm slices, flip angle 20°) and contrast-enhanced 3D FLAIR (TR 6000ms, TE 353ms, TI 2200ms, 1mm slices, flip angle 180°) on a 1.5T magnet. Contrast enhancing tumour from n=38 MRI scans were manually segmented by a radiologist slice by slice using contrast-enhanced 3D FLASH T1-weighted images on MIM software (v6.9.5). All cases at time-point 1 were contoured before contouring commenced for time-point 2 in the same order. Repeatability and spatial overlap was assessed by Dice similarity coefficient (DSC), Hausdorff distance (HD) and centroid shift. RESULTS A comparison of time-point 1 and 2 demonstrated the median DSC for n=19 cases was 0.84 (interquartile range 0.07), mean HD was only 0.1cm and mean centroid shift was 0.2cm. CONCLUSION High repeatability and spatial overlap of manually segmented contrast enhancing regions of recurrent glioblastoma were achieved on serial MRI. This substantiates a high level of repeatability which forms a core component of an MRI radiomics platform under development.
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