Diagnosis of hepatic alveolar echinococcosis:18F-FDG-PET activity compared to the Echinococcus multilocularis Ulm Ultrasound Classification.

Abstract

Alveolar echinococcosis (AE) is a rare, potentially fatal zoonosis with highly heterogeneous morphology. This study compares AE lesions in B-scan ultrasound, categorized according to the Echinococcus multilocularis Ulm Classification - Ultrasound (EMUC-US), with the maximum standardized uptake value (SUVmax) in 18F-Fluorodeoxyglucose Positron-Emission-Tomography (18F-FDG-PET/CT). 18F-FDG-PET/CT is the gold standard for evaluating disease activity, with SUVmax as the key parameter indirectly reflecting AE lesion activity.Retrospective analysis of data from the German National Echinococcosis Database. A total of 121 patients with 18F-FDG-PET/CT and B-scan ultrasound (US) between 2018-2019 were included. Based on EMUC-US, AE liver lesions were compared with the corresponding SUVmax in PET/CT. Additionally, SUV ratios (SUVTLR=tumor SUVmax/liver SUVmean) were calculated.The mean SUVmax, regardless of the EMUC-US subtype, was 6.0 ± 3.3 (range: 2.4-18.0). SUVmax comparison between subtypes shows significant differences (p<0.001). The highest SUVmax and SUVTLR were measured for the pseudocystic pattern with a mean of 9.2 ± 3.5 (range: 4.1-18.0). In contrast, the metastasis-like pattern yielded 3.7 ± 0.9 (range: 2.4-5.8) and the lowest SUVTLR. An SUVmax of 6.1 ± 3.3 (range: 2.6-16.8) was measured for the hailstorm pattern and 5.8 ± 2.2 (range: 3.6-10.4) for the hemangioma-like pattern.The results show significant differences between specific US patterns and the corresponding SUVmax. Lesions with very high or low SUV correlate with characteristic morphological patterns. Hence, in clinical practice B-scan can be a valuable bedside tool for assessing certain lesions. For evaluating inflammatory activity, 18F-FDG-PET/CT remains the method of choice.