Fig. 1

Hypovascular liver metastasis. A 53-year-old female undergoes surgery for rectal carcinoma and then receives RF ablation in a focal liver lesion. Eight months later, a local tumour progression (first column) at the cranial side of the ablation zone (large arrow) can be seen as an intermediate density (small arrow). In this straightforward case, the tumoral tissue is equally well depicted on the 40- and 70-keV images as on the greyscale iodine images. Noise is more prominent on the 40-keV image however. Iodine maps are encoded using a rainbow template with a colour coding from high to low iodine concentration, being from red (through yellow) to blue respectively. The intermediate colour represents a tumour (small arrow). On PET/CT a vivid FDG uptake is seen (arrowhead). Twenty-four hours after a second RF ablation (second column), a sharp delineated ablation zone is found. On all reconstructions, the avascular nature of the ablation zone is well demonstrated. The contrast with the surrounding liver parenchyma appears highest on the colour-coded iodine map. No FDG uptake is seen on the PET/CT image. The PET/CT 3 months later (not shown) does not show signs of tumoral activity