Fig. 7

Pulmonary metastases. A 77-year-old female, with a known melanoma, undergoes a PET/CT that shows a hypermetabolic nodule in the right upper lobe (not in our possession). The biopsy is non-conclusive. The therapeutic option is RF ablation. a Imaging is performed before (first column) and 24 h after (second column) RF ablation. The 70-keV lung window shows a focal nodule of 11 mm (white arrow) in proximity of a blood vessel. This nodule is hyperdense on the synthesised monochromatic 40-keV images and shows iodine content on the greyscale- and colour-coded iodine maps (circles). Destructive lung parenchyma is seen after the ablation as an irregular hyperdensity on the lung window (black arrows). The synthesised monochromatic 40-keV reconstructions show very heterogeneous densities in this region. The vessel on the anterior side is still intact (white arrowhead). On the iodine maps, we clearly observe the absence of iodine uptake (yellow arrowheads). PET/CT shows no activity in this region. b Imaging is performed before (first column) and 24 h after (second column) microwave ablation (MWA). After 6 months, a well-circumscribed consolidation is seen on the 70-keV lung window and synthesised monochromatic 40-keV image (arrows). The greyscale- and colour-coded iodine maps show no focal iodine uptake. This consolidation is hypermetabolic on PET/CT. As a result of the discrepancy between the morphologic and metabolic imaging methods, and the proximity of the blood vessel, which could lead to a heat-sink effect, the patient opts for further focal thermal treatment through microwave ablation. Twenty-four hours after ablation, a large heterogeneously shaped density is recognised on the lung window. The greyscale- and colour-coded iodine maps very clearly show the zone without internal contrast uptake (arrowheads) when compared to the 40-keV images. Again, a photopenic area is seen on the PET/CT image