ABSTRACT
OBJECTIVES: To determine the feasibility and role of parametric response mapping (PRM) for quantitative assessment of regional contrast-enhancement patterns in hepatocellular carcinoma (HCC). METHODS: Biphasic CT of 19 patients receiving repetitive conventional transarterial chemoembolisation (cTACE) for intermediate stage HCC were retrospectively analysed at baseline and follow-up at 3, 6, and 9 months. Voxel-based registration of arterial and porto-venous phases, with segmentation of the largest target lesion was performed. Frequency distribution plots of density-pairs of segmented voxels were generated. To differentiate necrotic, hypervascular and non-hypervascular tumour, and lipiodol/calcification, thresholds of 30, 100, and 300 HU were applied. Changes in density frequency plots over time were analysed and compared to response and assessment criteria (WHO, RECIST, EASL, mRECIST) and survival. RESULTS: PRM was feasible in all cases. Tumour volumes and hypervascular/non-hypervascular volume ratio showed significant longitudinal decrease (p < 0.05). Hypervascular volume at baseline was inversely correlated to survival (R = -0.57, p = 0.005). The only predictive parameter following cTACE to show significant survival difference was the change of the viable/non-viable ratio (p = 0.044), whereas common response assessment criteria showed no significant difference in survival. CONCLUSIONS: PRM allows a quantitative and more precise assessment of regional tumour vascularisation patterns and may be helpful for TACE treatment planning and response assessment. KEY POINTS: ⢠PRM allows more precise assessment of tumour vascularisation compared to conventional evaluation ⢠PRM is beneficial for cTACE treatment planning and response assessment ⢠PRM allows a quantitative assessment of regional contrast enhancement patterns.
Subject(s)
Carcinoma, Hepatocellular/diagnostic imaging , Chemoembolization, Therapeutic/methods , Contrast Media , Liver Neoplasms/diagnostic imaging , Radiographic Image Enhancement/methods , Tomography, X-Ray Computed/methods , Carcinoma, Hepatocellular/pathology , Carcinoma, Hepatocellular/therapy , Feasibility Studies , Female , Follow-Up Studies , Humans , Liver/diagnostic imaging , Liver Neoplasms/pathology , Liver Neoplasms/therapy , Male , Middle Aged , Retrospective Studies , Treatment OutcomeABSTRACT
PURPOSE: To demonstrate and quantify the heat sink effect in hepatic microwave ablation (MWA) in a standardized ex vivo model, and to analyze the influence of vessel distance and blood flow on lesion volume and shape. MATERIALS AND METHODS: 108 ex vivo MWA procedures were performed in freshly harvested pig livers. Antennas were inserted parallel to non-perfused and perfused (700,1400 ml/min) glass tubes (diameter 5mm) at different distances (10, 15, 20mm). Ablation zones (radius, area) were analyzed and compared (Kruskal-Wallis Test, Dunn's multiple comparison Test). Temperature changes adjacent to the tubes were measured throughout the ablation cycle. RESULTS: Maximum temperature decreased significantly with increasing flow and distance (p<0.05). Compared to non-perfused tubes, ablation zones were significantly deformed by perfused tubes within 15 mm distance to the antenna (p<0.05). At a flow rate of 700 ml/min ablation zone radius was reduced to 37.2% and 80.1% at 10 and 15 mm tube distance, respectively; ablation zone area was reduced to 50.5% and 89.7%, respectively. CONCLUSION: Significant changes of ablation zones were demonstrated in a pig liver model. Considerable heat sink effect was observed within a diameter of 15 mm around simulated vessels, dependent on flow rate. This has to be taken into account when ablating liver lesions close to vessels.
