Interpreting Ice-Water Phantom Data for Prediction of Clinical ADC Measurement

The aim of this study was to investigate the extent to which measurements made in an ADC (apparent diffusion coefficient) calibration phantom could be shown to correlate with accuracies of measurements made in normal liver. Ideally, a strong correlation might be used in the future in order to perform an assessment of scanner performance based entirely on the phantom. Several metrics of image quality were automatically extracted from the phantom and ROI’s (regions of interest) were identified manually for human livers. Analysis was performed in two stages, firstly looking at correlations between metrics measured in the phantom in order to gain an understanding of reliability, and secondly looking at the reproducibility of human data. Correlations in phantom measurements help to identify which of the possible summary statistics are likely to be best measured and meaningful. This has allowed us to refine our definitions of the parameters which are most useful for summarising phantom data. It has also allowed us to identify phantom design weaknesses which might be improved. Repeatability in humans sets a limit for realistic clinical performance and also highlights potential problems in current methodology.