Fig. 4

Renal cell carcinoma. An ultrasound reveals a renal mass in a 72-year-old male. a Venous phase DECT confirms a lesion in the left kidney. On the water map images, the lesion is exophytic and isodense compared to the kidney parenchyma (arrows). The synthesised monochromatic 40-keV greyscale-coded and colour-coded iodine images show a hypovascular lesion compared to the kidney parenchyma. A biopsy demonstrates a renal clear cell carcinoma. b On the iodine-coded image (left), three ROIs are selected: L1 (red) in the RCC; L2 (blue) in the renal vein; L3 (yellow) in the unaffected kidney parenchyma. The estimated amounts of iodine in the ROIs are presented in the right lower corner (mean value and standard deviation in 100 μg/cm³). On the spectral HU curve (right), the renal vein (L2) and RCC (L1) represent overlapping curves, suggesting similar iodine content. The normal kidney parenchyma (L3) has a markedly higher curve in the lower keV range, confirming a higher iodine uptake. c Axial (left column) and coronal (right column) reconstructions from a contrast-enhanced venous phase DECT, 24 h post-RF ablation. The water map images show very poor hyperattenuation in the ablated zone (arrowheads). The contrast difference between the ablation zone and the kidney parenchyma is well demonstrated on the synthesised monochromatic 40- and 70-keV images. The colour-coded iodine images show well-depicted areas of intermediate density on the axial reconstructions (black arrows) surrounding the ablation zone. The axial images of the synthesised monochromatic reconstructions less clearly visualise these regions. The multiplicity suggests a benign post-ablative finding, probably corresponding to transient thermal damage to the bordering kidney parenchyma. No definitive conclusion can be made concerning residual tumour solely relying on these images. However, compared to the pre-ablation imaging, we can assume that the tissue in question is a normal kidney parenchyma. At the outer margin of the ablation zone, a region of intermediate density is depicted. The coronal reconstructions are essential to prove the continuity with regard to the kidney parenchyma (white arrows). d On the follow-up CECT 15 months later, the focally enhanced tissue at the lateral side shows no signs of growth (arrow), thus confirming the absence of residual tumour