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

## TL;DR

This study compares ultrasound patterns of liver lesions in a rare parasitic disease with PET scan results to assess disease activity.

## Contribution

The study identifies distinct correlations between ultrasound lesion patterns and PET SUVmax values in hepatic alveolar echinococcosis.

## Key findings

- Pseudocystic lesions showed the highest SUVmax and SUVTLR, while metastasis-like lesions had the lowest.
- SUVmax values varied significantly across different ultrasound subtypes of AE lesions.
- B-scan ultrasound can be a useful tool for lesion assessment, while PET/CT remains best for evaluating inflammatory activity.

## 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.