Comparison between the two quantitative tumour response measurements when two different Intra = Tx ROI methods were used. Plot (a) is a scatter plot of the two methods. The solid line in this graph is the unity line where . For most tumours. An outlier is identified by the oblique arrow above the unity line where . In plot (b), the tumour response on -axis is plotted for all 26 tumours on -axis. Thresholds of ±30% as defined by PERCIST were applied to separate individual tumours to different categories using either (red) or (blue). 19% of the tumours (5 out of 26) were ambiguously classified as shown by vertical arrows.