Critical structure	CT dataset utilised	Approximate time required for segmentation	Comments
Liver body	Axial, portal venous phase image data	4 hours	Manual segmentation
			Error in manual segmentation was minimised by (I) selecting the portal venous phase dataset featuring normal enhancement of liver parenchyma; and (II) applying a median filter to better define liver boundaries
Tumour and associated arterial vascular supply	Axial, arterial phase image data	1 hour	Semi-automatic segmentation involving (I) rough manual segmentation to distinguish the region including the tumour and hepatic arteries; followed by (II) application of a suitable threshold to separate the enhancing structures from non-enhancing intrahepatic tissues
Portal and hepatic veins (and associated venous branches)	Axial, segmented liver body originating from the portal venous image data	1 hour	Combination of thresholding and object separator tools utilised
			Success of thresholding was dependent on the quality of contrast enhancement
			The segmented liver volume data was used as unwanted abdominal structures of similar attenuation were excluded, allowing for the thresholding to be more effective

CT, computed tomography.