Accurately evaluating treatment response in patients with abdominal cancer is vital for guiding therapy and improving outcomes. Conventional imaging approaches, which rely primarily on tumour size reduction as a marker of therapeutic efficacy, often fall short when applied to newer systemic or locoregional treatments. Therapies that induce necrosis or alter vascularity may not result in immediate or significant size changes, leading to misinterpretation of tumour behaviour. Dual-energy CT (DECT), an advanced imaging technology, offers new possibilities in this context. By providing functional and anatomical insights through iodine quantification and material-specific imaging, DECT can better capture therapeutic effects, improve lesion detection and support more informed clinical decisions.
Addressing the Shortcomings of Traditional Imaging Criteria
Historically, imaging criteria such as RECIST have been instrumental in standardising response assessment. However, these criteria are largely morphology-based and may not reflect the biological response induced by modern treatments. Immunotherapies and targeted agents often lead to tumour necrosis or immune-related pseudoprogression, phenomena that may not translate into measurable size reductions. Similarly, locoregional therapies like radiofrequency ablation or transarterial chemoembolisation aim to destroy tumour tissue directly, often without producing immediate structural shrinkage. In such cases, relying solely on size as a marker of efficacy can be misleading.
To improve diagnostic accuracy, newer criteria focusing on tumour viability and functional changes have been introduced. Modified RECIST and Choi criteria incorporate arterial enhancement and attenuation values, offering a more refined assessment. DECT complements these efforts by enabling quantitative evaluation of tumour vascularity using iodine concentration. This functional approach aligns better with treatment mechanisms and provides earlier indications of response, often before visible structural changes appear.
Advantages and Technical Capabilities of DECT
DECT operates by capturing two energy spectra during scanning, allowing for superior material differentiation. This technology generates several types of images, including virtual monoenergetic images (VMI), iodine maps and virtual noncontrast (VNC) images. Each offers distinct diagnostic advantages. VMI improves contrast resolution, helping differentiate tumours from surrounding tissue, especially in low-contrast scenarios or when iodinated contrast media is limited. These images are particularly useful in identifying arterial phase hyperenhancement, a key feature in assessing viable tumour tissue.
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Iodine maps provide quantitative data on tissue perfusion by measuring iodine content within lesions. This enables clinicians to monitor changes in vascularity during and after treatment, offering insights into tumour viability. For instance, increased iodine uptake may suggest active disease, while a reduction may reflect a positive treatment response. VNC images simulate noncontrast scans by subtracting iodine signal from contrast-enhanced images, thus reducing the need for additional scans and limiting radiation exposure.
These features make DECT particularly valuable in abdominal oncology, where multiple organs and vascular structures complicate interpretation. By reducing beam-hardening artefacts and improving contrast-to-noise ratios, DECT enhances visualisation even in the presence of metal implants or high-density materials. The technology’s ability to fine-tune image parameters according to tumour type and location supports a more individualised and effective diagnostic process.
Applications in Treatment Monitoring
DECT has shown promising results across various abdominal malignancies and treatment modalities. In hepatocellular carcinoma, DECT-based iodine quantification correlates well with clinical response, outperforming standard size-based criteria. Similarly, in renal cell carcinoma, iodine overlay images and VNC scans assist in detecting residual disease after ablation with high sensitivity and specificity. Gastrointestinal stromal tumours also benefit from DECT, as changes in iodine-related attenuation have been linked to treatment response and prognosis.
In rectal and pancreatic cancers, studies have demonstrated that changes in iodine concentration can mirror histopathological findings, suggesting that DECT may serve as a viable alternative to more invasive or expensive imaging methods. DECT is also being explored in cervical cancer, where pre- and post-treatment iodine values may help predict and monitor response.
Locoregional therapies particularly benefit from DECT’s capabilities. After procedures such as microwave or radiofrequency ablation, DECT helps differentiate post-treatment inflammation from residual tumour. Iodine maps clearly delineate ablation zones and highlight areas of viable tumour, aiding in early detection of recurrence. VMI improves lesion visibility, while VNC images reduce artefacts and help identify complications like haemorrhage.
In intra-arterial therapies such as transarterial chemoembolisation, DECT supports evaluation by identifying areas of residual enhancement and quantifying iodine uptake. This helps distinguish viable tumour tissue from coagulative necrosis, providing clinicians with actionable insights for follow-up care.
Dual-energy CT represents a significant advancement in the imaging of abdominal malignancies. By moving beyond the limitations of traditional size-based criteria, DECT offers a more comprehensive approach to treatment monitoring. Its ability to assess tumour vascularity, generate high-contrast images and reduce artefacts makes it a valuable tool in both systemic and locoregional therapy evaluation. While challenges such as scanner variability and standardisation persist, the growing body of evidence supports DECT’s integration into routine oncologic practice. In the future, DECT is set to play a central role in precision cancer care.
Source: Radiology: Imaging Cancer
Image Credit: iStock
