Hepatocellular carcinoma (HCC) is a major global health challenge, ranking as the sixth most common cancer and the fourth leading cause of cancer-related death worldwide. Early detection and precise monitoring are crucial for improving patient outcomes, especially in high-risk individuals with liver cirrhosis or chronic hepatitis infections.
Diagnostic imaging plays a central role in HCC management, with magnetic resonance imaging (MRI) commonly used for both initial detection and post-treatment follow-up. However, limitations exist with MRI, particularly in cases where enhancement patterns are atypical or where image quality is compromised by motion artefacts. To address these challenges, a dual imaging strategy combining CT liver perfusion (CTLP) with MRI has shown promise. This approach enhances sensitivity without sacrificing the high specificity necessary for confident clinical decision-making.
CT Perfusion and MRI: Complementary Strengths
MRI is a widely accepted tool for HCC diagnosis due to its ability to identify tumour vascular patterns non-invasively. It provides high specificity, especially when applying the Liver Imaging Reporting and Data System (LI-RADS) criteria that categorise observations based on enhancement and washout patterns. However, MRI can be limited in certain scenarios, particularly when lesions do not exhibit typical arterial phase hyperenhancement or when technical issues, such as motion artefacts or native high T1 signal, obscure imaging clarity.
CTLP, by contrast, focuses on tissue microcirculation, offering a more detailed assessment of liver perfusion. It uses advanced parametric maps to measure perfusion metrics like Mean Slope of Increase (MSI), Time to Peak (TTP) and Hepatic Arterial Blood Flow (HaBF). These metrics help quantify the vascular supply and perfusion dynamics within the liver, enabling better distinction between viable tumour tissue and benign changes after treatment. While CTLP alone has comparable sensitivity to MRI, its combination with MRI significantly increases sensitivity by capturing lesions that MRI may miss.
The combined use of CTLP and MRI offers a broader diagnostic picture. MRI provides morphological and vascular insights, while CTLP adds functional data on blood flow and tissue perfusion. When used together, this dual approach improves the detection of both untreated and post-treatment lesions, reducing the risk of missing viable tumours.
Enhancing Post-Treatment Monitoring
Accurate follow-up imaging is critical for patients undergoing locoregional treatments such as transarterial chemoembolisation (TACE) or microwave ablation (MWA). These therapies aim to target and destroy tumour tissue while preserving healthy liver function. However, incomplete tumour destruction or early recurrence is possible, making precise imaging essential for assessing treatment success.
While effective, MRI can sometimes struggle with post-treatment changes that mimic residual disease, such as treatment-related enhancement or benign post-ablation changes. The LI-RADS Treatment Response Algorithm (LR-TRA) helps standardise MRI assessments of tumour viability but may fall short in cases where enhancement patterns are subtle or non-specific.
By introducing CTLP alongside MRI, the sensitivity of post-treatment monitoring improves significantly. CTLP provides perfusion data that can distinguish between viable tumour tissue and treatment-related changes by highlighting areas with active blood supply indicative of residual cancer. For instance, in cases where MRI categorises a lesion as equivocal, CTLP can clarify the diagnosis, guiding clinical decisions such as whether to pursue further intervention or continue observation.
A study involving patients with both treated and untreated HCC lesions demonstrated the combined approach's effectiveness. When MRI and CTLP were used together, sensitivity improved from 72.2% with MRI alone to 85.2%, while specificity remained high at 97.5%. This enhanced diagnostic accuracy led to management changes in multiple cases, reinforcing the value of a combined imaging strategy.
Clinical Impact and Considerations
The integration of CTLP with MRI has important implications for HCC management. Improved sensitivity in tumour detection allows for earlier intervention, which can be crucial for maintaining eligibility for curative treatments such as liver transplantation or surgical resection. Furthermore, the combined approach reduces the likelihood of false-negative results, ensuring that patients receive appropriate follow-up care based on a clearer assessment of their disease status.
However, this dual-modality approach is not without limitations. CTLP exposes patients to ionising radiation, making it less suitable for routine use in all follow-up scenarios, especially in patients requiring long-term monitoring. Additionally, the complexity and cost of performing both CTLP and MRI may limit widespread adoption in resource-constrained healthcare settings. Effective use of this strategy requires careful patient selection, with a focus on high-risk cases or situations where MRI findings are inconclusive.
Expert interpretation is also essential, as the combined analysis requires proficiency in both MRI and CTLP techniques. The use of standardised protocols, such as LI-RADS and mRECIST, helps ensure consistent reporting and decision-making, but further training and collaboration among radiology teams may be necessary to optimise the benefits of this approach.
The combination of CT liver perfusion and MRI represents a promising advancement in the diagnosis and post-treatment monitoring of hepatocellular carcinoma. By leveraging the complementary strengths of both modalities, clinicians can achieve greater sensitivity in detecting viable tumour tissue without compromising specificity. This approach is particularly valuable in patients undergoing locoregional therapies, where accurate assessment of residual disease is essential for guiding further treatment. While challenges such as radiation exposure and cost remain, selective use of CTLP alongside MRI could significantly improve patient outcomes and help refine modern HCC management strategies.
Source: European Journal of Radiology
Image Credit: iStock
