Dual-energy CT after radiofrequency ablation of liver, kidney, and lung lesions: a review of features

Abstract

Early detection of residual tumour and local tumour progression (LTP) after radiofrequency (RF) ablation is crucial in the decision whether or not to re-ablate. In general, standard contrast-enhanced computed tomography (CT) is used to evaluate the technique effectiveness; however, it is difficult to differentiate post-treatment changes from residual tumour. Dual-energy CT (DECT) is a relatively new technique that enables more specific tissue characterisation of iodine-enhanced structures because of the isolation of iodine in the imaging data. Necrotic post-ablation zones can be depicted as avascular regions by DECT on greyscale- and colour-coded iodine images. Synthesised monochromatic images from dual-energy CT with spectral analysis can be used to select the optimal keV to achieve the highest contrast-to-noise ratio between tissues. This facilitates outlining the interface between the ablation zone and surrounding tissue. Post-processing of DECT data can lead to an improved characterisation and delineation of benign post-ablation changes from LTP. Radiologists need to be familiar with typical post-ablation image interpretations when using DECT techniques. Here, we review the spectrum of changes after RF ablation of liver, kidney, and lung lesions using single-source DECT imaging, with the emphasis on the additional information obtained and pitfalls encountered with this relatively new technique.Teaching Points•Technical success of RF ablation means complete destruction of the tumour.•Assessment of residual tumour on contrast-enhanced CT is hindered by post-ablative changes.•DECT improves material differentiation and may improve focal lesion characterisation.•Iodine maps delineate the treated area from the surrounding parenchyma well.

Virtual non-contrast for evaluation of liver parenchyma and vessels: results from 25 patients using multi-phase spectral-detector CT

“…Further, VNC offers great potential to replace TNC images of the liver for the characterization of liver lesions, e.g. in primary diagnosis of hepatocellular carcinoma or after radiofrequency ablation of liver lesions, VNC can be used to identify real hyperenhancing lesions and separate them from hyperdense structures without contrast agent enhancement (4,28). Similarly, abdominal bleeding could be identified with higher diagnostic certainty if VNC images are used as an addition to arterial and venous phase acquisitions.…”

Imaging review of hepatocellular carcinoma after thermal ablation: The good, the bad, and the ugly

“…Portal venous and delayed phases are acquired with the same delay as MR. Recently, spectral CT has recently been shown to result in better tumor visualization and detection rate but further evaluation is needed in this clinical setting …”

Virtual Noncontrast Imaging of the Liver Using Photon-Counting Detector Computed Tomography

“…Among other applications, 1,2 their use has been demonstrated for liver fat quantification, 3 characterization of adrenal adenomas, 4 and detection of stones and calcifications in the hepatobiliary or urogenital system 5 . Furthermore, VNC was shown useful in determining if a hyperdense liver lesion exhibited true contrast enhancement 6 . Former studies were performed on DECT systems that were equipped with conventional energy-integrating detectors (EIDs).…”