Example of density measurement in the cystoid portions of AE lesions on CT. Left and below: in each case, two enlarged ROIs within the cystoid portions of AE lesions of different primary morphological types: (1) Type I “diffuse infiltrating with cystoid portion”; (2) Type II “primarily circumscribed tumour-like with cystoid portion”; (3) Type IIIa “primarily cystoid intermediate without solid portion at the edge”; (4) Type IIIb “primarily cystoid widespread with solid portion at the edge”; (5) Type IV “small cystoid/metastatic”. Above right: two ROIs with surface data and HU values (max, min, mean and standard deviation) within the cystoid portion of an AE lesion involving both lobes of the liver. (AE = alveolar echinococcosis; CT = computed tomography; HU = Hounsfield unit; ROI = region of interest).