<p>Accurate assessment of safety margins after percutaneous thermal ablation of liver tumours is critical to minimize local tumour progression (LTP). However, post-ablation margin assessment remains challenging, especially given that ablated tumours cannot be readily appreciated on standard post-ablation imaging. This pictorial essay illustrates the use of contrast-based tumour tagging during CT hepatic arteriography (CTHA)-guided ablation, which preserves tumour conspicuity on post-ablation imaging. By injecting contrast medium and starting energy delivery at the time of maximal tumour enhancement, the contrast agent depicts the tumour, rendering it hyperdense on post-ablation CT scans. This enables direct visualization of the ablated tumour and its margins on post-ablation scans, facilitating both visual and software-assisted margin evaluation. Eleven clinical cases are presented, demonstrating the versatility, reproducibility, and potential pitfalls of this technique. Prospective studies are warranted to validate its impact on local tumour control and to optimize integration into standard image-guided ablation protocols.</p> Graphical Abstract <p></p>