Pericystic metabolic activity in alveolar echinococcosis: assessment and follow-up by positron emission tomography

Value of intralesional and perilesional radiomics for predicting the bioactivity of hepatic alveolar echinococcosis

Objectives

To investigate the value of intralesional and perilesional radiomics based on computed tomography (CT) in predicting the bioactivity of hepatic alveolar echinococcosis (HAE).

Materials and methods

In this retrospective study, 131 patients who underwent surgical resection and diagnosed HAE in pathology were included (bioactive, n=69; bioinactive, n=62). All patients were randomly assigned to the training cohort (n=78) and validation cohort (n=53) in a 6:4 ratio. The gross lesion volume (GLV), perilesional volume (PLV), and gross combined perilesional volume (GPLV) radiomics features were extracted on CT images of portal vein phase. Feature selection was performed by intra-class correlation coefficient (ICC), univariate analysis, and least absolute shrinkage and selection operator (LASSO). Radiomics models were established by support vector machine (SVM). The Radscore of the best radiomics model and clinical independent predictors were combined to establish a clinical radiomics nomogram. Receiver operating characteristic curve (ROC) and decision curves were used to evaluate the predictive performance of the nomogram model.

Results

In the training cohort, the area under the ROC curve (AUC) of the GLV, PLV, and GPLV radiomic models was 0.774, 0.729, and 0.868, respectively. GPLV radiomic models performed best among the three models in training and validation cohort. Calcification type and fibrinogen were clinical independent predictors (p<0.05). The AUC of the nomogram-model-based clinical and GPLV radiomic signatures was 0.914 in the training cohort and 0.833 in the validation cohort. The decision curve analysis showed that the nomogram had greater benefits compared with the single radiomics model or clinical model.

Conclusion

The nomogram model based on clinical and GPLV radiomic signatures shows the best performance in prediction of the bioactivity of HAE. Radiomics including perilesional tissue can significantly improve the prediction efficacy of HAE bioactivity.

Management of biliary obstruction in patients with newly diagnosed alveolar echinococcosis: a Swiss retrospective cohort study

BACKGROUND AND STUDY AIMS

Alveolar echinococcosis, an orphan zoonosis affecting the liver, is of increasing concern worldwide. Most symptomatic cases present at an advanced and inoperable stage, sometimes with biliary obstruction prompting biliary tract interventions. These are, however, associated with a high risk of infectious complications. The aim of this retrospective study was to compare the effectiveness and safety of conservative and interventional treatment approaches in patients with newly diagnosed alveolar echinococcosis and biliary obstruction.

PATIENTS AND METHODS

Alveolar echinococcosis patients treated at two referral centres in Switzerland, presenting with hyperbilirubinaemia (total bilirubin >1.5 Upper Limit of Normal) at diagnosis were included, unless another underlying aetiology, i.e. common bile duct stones or decompensated cirrhosis, was identified. Patients were divided into two groups, according to whether they initially received a biliary tract intervention. The primary endpoint was normalisation of bilirubin levels within a 6-month period. Secondary endpoints included, among others, the occurrence of early and late biliary complications, the need for biliary tract interventions during follow-up and overall duration of hospital stays for treatment initiation and for biliary complications.

RESULTS

28 patients were included in this study, of whom 17 received benzimidazole therapy alone and 11 additionally received a biliary tract intervention. Baseline characteristics did not differ between groups. All but one patient in each group achieved the primary endpoint (p=0.747). Biliary tract intervention was associated with faster laboratory improvement (t1/2 1.3 vs 3.0 weeks), but also with more frequent early biliary complications (7/11 vs 1/17, p=0.002) and longer initial hospital stay (18 days vs 7 days, p=0.007).

CONCLUSION

Biliary obstruction in patients with newly diagnosed alveolar echinococcosis can be treated effectively with benzimidazole therapy alone. Biliary tract intervention, on the other hand, is associated with a high complication rate and should probably be reserved for patients with insufficient response to benzimidazole therapy.

18FDG-PET/CT-Scans and Biomarker Levels Predicting Clinical Outcome in Patients with Alveolar Echinococcosis-A Single-Center Cohort Study with 179 Patients

Background: Alveolar echinococcosis (AE) is a severe larval tapeworm infection with a variable clinical course of the disease. Reliable imaging techniques and biomarkers are needed to predict the course of the disease. Methods: 179 AE patients that received PET/CT scans between 2008 and 2012 were retrospectively included. From stored blood samples taken on the day of the scan, levels of IgE, parasite-specific serology, amyloid A, C-reactive protein, soluble interleukin 2 receptor, cytokeratin fragments, eosinophilic cell count, and eosinophil cationic protein were measured. Additionally, the current clinical outcome (cured, stable, or progressive disease) after a median duration of 8 years after baseline examination was assessed. Ultimately, an ordinal logistic regression was conducted to evaluate which imaging parameters and biomarkers independently influence the clinical outcome. Results: In general, patients in need of medical treatment or with progressive disease, advanced PNM stages, and positive PET/CT scans exhibited higher levels of the respective biomarkers. However, only the parasite-specific serological markers and total IgE levels differed significantly between clinical groups, WHO PNM stages, and the results of the PET/CT scan. In the multivariate analysis, PET/CT results were a strong predictor of the clinical outcome (OR 8.908, 95%CI 3.019-26.285; p < 0.001), and age at baseline was a moderate predictor (OR 1.031, 95%CI 1.003-1.060; p = 0.029). Conclusions: The PET/CT scan is, preferably in combination with parasite-specific serology and IgE levels, a valuable tool in the clinical management of AE and is able to predict the course of the disease.

18F-FDG-PET/MR in Alveolar Echinococcosis: Multiparametric Imaging in a Real-World Setting

Recent improvements in alveolar echinococcosis (AE) therapy can provide long-term disease control, and even allow structured treatment interruption in selected cases. Imaging has a pivotal role in monitoring disease activity, with 18-fluoro-deoxyglucose positron emission and computed tomography (18F-FDG-PET/CT) in particular having proven beneficial for assessing disease activity. Repetitive regular examinations to monitor therapy response, however, can lead to substantial radiation burden. Therefore, by combining metabolic information and excellent tissue contrast in magnetic resonance imaging (MRI), PET/MR appears ideally suited for this task. Here, we retrospectively analyzed 51 AE patients that underwent 18F-FDG-PET/MR. Patients had a ‘confirmed/probable’ diagnosis in 22/29 cases according to the WHO classification. FDG uptake, diffusion restriction, and MRI morphology were evaluated. We found significant differences in FDG uptake between responders to benzimidazole therapy and progressive manifestations (SUVavg 2.7 ± 1.3 vs. 5.4 ± 2.2, p < 0.001) as well as between Kodama Types 1 and 3 (F = 9.9, p < 0.003). No significant differences were detected for ADC values or MRI morphology concerning response and no correlations were present between FDG uptake and ADC values. The mean radiation dose was 5.9−6.5 mSv. We conclude that the combination of metabolic information and MRI morphology at a low radiation dose proposes PET/MR as a suitable imaging modality for AE assessment. Longitudinal studies are needed to define the role of this imaging modality.

Advances in the treatment, diagnosis, control and scientific understanding of taeniid cestode parasite infections over the past 50 years

In the past 50 years, enormous progress has been made in the diagnosis, treatment and control of taeniid cestode infections/diseases and in the scientific understanding thereof. Most interest in this group of parasites stems from the serious diseases that they cause in humans. It is through this lens that we summarize here the most important breakthroughs that have made a difference to the treatment of human diseases caused by these parasites, reduction in transmission of the taeniid species associated with human disease, or understanding of the parasites' biology likely to impact diagnosis or treatment in the foreseeable future. Key topics discussed are the introduction of anti-cestode drugs, including benzimidazoles and praziquantel, and the development of new imaging modalities that have transformed the diagnosis and post-treatment monitoring of human echinococcoses and neurocysticercosis. The availability of new anti-cestode drugs for use in dogs and a detailed understanding of the transmission dynamics of Echinococcus granulosus sensu lato have underpinned successful programs that have eliminated cystic echinococcosis in some areas of the world and greatly reduced the incidence of infection in others. Despite these successes, cystic and alveolar echinococcosis and neurocysticercosis continue to be prevalent in many parts of the world, requiring new or renewed efforts to prevent the associated taeniid infections. Major advances made in the development of practical vaccines against E. granulosus and Taenia solium will hopefully assist in this endeavour, as might the understanding of the parasites' biology that have come from an elucidation of the nuclear genomes of each of the most important taeniid species causing human diseases.

Hepatic Alveolar Echinococcosis

Hepatic alveolar echinococcosis (HAE) is a rare but severe zoonosis caused by the pseudotumoral intrahepatic development of the larval stage of the tapeworm Echinococcus multilocularis. HAE is present only in the Northern Hemisphere, predominantly in China. Currently, there is a significant resurgence of cases in historically endemic areas associated with emergence of HAE in countries not previously concerned. Today, in European countries, HAE is often discovered by chance; however, clinicians should be made aware of opportunistic infections that progressively emerged recently as a result of therapeutic or pathological immunosuppression. Ultrasonography is the key first-line diagnostic procedure, with specific serology providing confirmation in 95% of the cases. Albendazole, only parasitostatic, is the mainstay for treatment. Surgical resection, if feasible, is the gold standard for treatment, and more patients are currently eligible for this option because of an earlier diagnosis. The prognosis has considerably improved but remains poor in countries where access to care is less favorable.

Parasites of the liver - epidemiology, diagnosis and clinical management in the European context

Parasites in the liver cause significant global morbidity and mortality, as they can lead to recurrent cholangitis, cirrhosis, liver failure and cancer. Due to climate change and globalisation, their incidence is increasing, especially in Europe. The correct diagnosis of a hepatic parasite is often delayed because clinicians are unfamiliar with respective entities. Therefore, in this review, we aim to provide clinicians with a comprehensive clinical picture of hepatic parasites and to bring these neglected parasitic liver diseases to the wider attention of hepatology stakeholders in Europe and around the world.

Emerging human alveolar echinococcosis in Hungary (2003-2018): a retrospective case series analysis from a multi-centre study

Background

Human alveolar echinococcosis (AE) caused by Echinococcus multilocularis is an underreported, often misdiagnosed and mistreated parasitic disease mainly due to its low incidence. The aim of this study was to describe the epidemiological and clinical characteristics of human AE patients in Hungary for the first time.

Method

Between 2003 and 2018, epidemiological and clinical data of suspected AE patients were collected retrospectively from health database management systems.

Results

This case series included a total of 16 AE patients. The mean age of patients was 53 years (range: 24–78 years). The sex ratio was 1:1. Four patients (25%) revealed no recurrence after radical surgery and adjuvant albendazole (ABZ) therapy. For five patients (31.3%) with unresectable lesions, a stabilization of lesions with ABZ treatment was achieved. In seven patients (43.8%), progression of AE was documented. The mean diagnostic delay was 33 months (range: 1–122 months). Three AE related deaths (fatality rate 18.8%) were recorded.

Conclusions

AE is an emerging infectious disease in Hungary with a high fatality rate since based on our results, almost every fifth AE patient died in the study period. Differential diagnosis and appropriate surgical and medical therapy for AE is an urging challenge for clinicians in Hungary, as well as in some other European countries where E. multilocularis is prevalent.

Current Applications for Nuclear Medicine Imaging in Pulmonary Disease

Purpose of Review

The main goal of the article is to familiarize the reader with commonly and uncommonly used nuclear medicine procedures that can significantly contribute to improved patient care. The article presents examples of specific modality utilization in the chest including assessment of lung ventilation and perfusion, imaging options for broad range of infectious and inflammatory processes, and selected aspects of oncologic imaging. In addition, rapidly developing new techniques utilizing molecular imaging are discussed.

Recent Findings

The article describes nuclear medicine imaging modalities including gamma camera, SPECT, PET, and hybrid imaging (SPECT/CT, PET/CT, and PET/MR) in the context of established and emerging clinical applications. Areas of potential future development in nuclear medicine are discussed with emphasis on molecular imaging and implementation of new targeted tracers used in diagnostics and therapeutics (theranostics).

Summary

Nuclear medicine and molecular imaging provide many unique and novel options for the diagnosis and treatment of pulmonary diseases. This article reviews current applications for nuclear medicine and molecular imaging and selected future applications for radiopharmaceuticals and targeted molecular imaging techniques.

Hepatic alveolar echinococcosis: correlation between computed tomography morphology and inflammatory activity in positron emission tomography

Positron emission tomography-computed tomography (PET-CT) with 18F-fluorodesoxyglucose (FDG) is the imaging modality of choice for assessing inflammation surrounding hepatic alveolar echinococcosis (AE) lesions. This study is the first to evaluate FDG uptake in hepatic AE (n = 51) based on the standardized uptake value (SUV) and to correlate the SUVs with primary morphology and calcification patterns, based on the Echinococcus multilocularis Ulm Classification for Computed-Tomography (EMUC-CT). Our results show that the SUVs were increased for lesions with EMUC-CT types I-IV primary morphology, compared to the surrounding healthy liver tissue (SUV = 2.5 ± 0.4; p < 0.05). Type IV lesions included, by far, the highest number of PET-negative lesions. A comparison of lesions with different primary morphologies showed clear differences. The highest SUVs were found for types I and III, and the lowest was found for type IV. Type IV lesions (SUV, 3.8 ± 1.5) showed significantly lower uptake compared to type I (SUV, 6.9 ± 3.5; p = 0.030) and type III (SUV, 7.4 ± 3.9; p = 0.031) lesions. For type II lesions, the results showed only a statistical trend (SUV, 6.1 ± 3.1; p = 0.073). Due to the small number of cases, an evaluation of type V (n = 1) lesions was not possible. The different SUVs of lesions with different primary morphologies, particularly the lower FDG uptake observed in type IV lesions, suggested that these SUVs might reflect different stages of the disease.

Molecular Imaging of Pulmonary Inflammation and Infection

Infectious and inflammatory pulmonary diseases are a leading cause of morbidity and mortality worldwide. Although infrequently used in this setting, molecular imaging may significantly contribute to their diagnosis using techniques like single photon emission tomography (SPET), positron emission tomography (PET) with computed tomography (CT) or magnetic resonance imaging (MRI) with the support of specific or unspecific radiopharmaceutical agents. ¹⁸F-Fluorodeoxyglucose (¹⁸F-FDG), mostly applied in oncological imaging, can also detect cells actively involved in infectious and inflammatory conditions, even if with a low specificity. SPET with nonspecific (e.g., ⁶⁷Gallium-citrate (⁶⁷Ga citrate)) and specific tracers (e.g., white blood cells radiolabeled with ¹¹¹Indium-oxine (¹¹¹In) or ^99mTechnetium (^99mTc)) showed interesting results for many inflammatory lung diseases. However, ⁶⁷Ga citrate is unfavorable by a radioprotection point of view while radiolabeled white blood cells scan implies complex laboratory settings and labeling procedures. Radiolabeled antibiotics (e.g., ciprofloxacin) have been recently tested, although they seem to be quite unspecific and cause antibiotic resistance. New radiolabeled agents like antimicrobic peptides, binding to bacterial cell membranes, seem very promising. Thus, the aim of this narrative review is to provide a comprehensive overview about techniques, including PET/MRI, and tracers that can guide the clinicians in the appropriate diagnostic pathway of infectious and inflammatory pulmonary diseases.

Hepatic alveolar hydatid disease (Echinococcus multilocularis), a mimic of liver malignancy: a review for the radiologist in non-endemic areas

Alveolar hydatid disease or alveolar echinococcosis (AE) is caused by the parasite Echinococcus multilocularis and is increasingly seen as an imported disease in non-endemic areas such as the UK. It is rare compared to cystic echinococcosis (CE), but like CE commonly affects the liver. AE does have imaging features that can aid in diagnosis, but is often initially misdiagnosed as liver malignancy. It is usually fatal if untreated, underscoring the importance of early diagnosis. This review highlights the role of imaging in AE diagnosis with the broader objective of increasing radiologists' awareness of this unusual, but increasingly prevalent disease.

Could SUVmax be an auxiliary parameter in the clinical management of pulmonary hydatid disease?

OBJECTIVE

The aim of this study was to investigate the role of 18F-fluorodeoxyglucose positron emission tomography/computerized tomography (FDG-PET/CT) in the diagnosis and treatment of pulmonary hydatid disease and also compare the morphological characteristics of the lesions with SUVmax values and identify complicated disease.

METHODS

Thirty-six patients with a diagnosis of pulmonary hydatid disease who underwent 18F-FDG PET/CT imaging were included in this retrospective study. The size of the lesions, morphological characteristics, accompanying parenchymal and pleural findings, SUVmax and HUmean values and FDG uptake in mediastinal lymph nodes were noted. The relationship between morphologic properties, SUVmax of the lesions and lymphatic FDG uptake was analysed.

RESULTS

A total of 99 lesions of 36 patients were classified as solid (7.1%), cystic (53.5%), semisolid (20.2%) and cavitary (19.2%). Thirty-two of the lesions were encapsulated, 38 of the lesions had border irregularity. Accompanying consolidation was present in 10 cases, bronchial obstruction in 9, pleural thickening in 28 and effusion in 3. There was positive correlation between lesions HUmean and SUVmax values (r = 0.285). SUVmax values were significantly higher in lesions with irregular borders, solid or semisolid type and presence of consolidation, bronchial obstruction and pleural thickening. Also more lymphatic FDG uptake was detected in this group.

CONCLUSION

Higher SUVmax values may be a useful parameter in the diagnosis of complicated pulmonary hydatid disease. FDG-PET may provide guidance for determining the priority of lesion for surgery in cases with multiple lesions and may be helpful to evaluate the response to medical treatment.

Biological characteristics of 18F-FDG PET/CT imaging of cerebral alveolar echinococcosis

This study aims to analyze the characteristics of F-fluorodeoxyglucose positron emission tomography/computed tomography (F-FDG PET/CT) for cerebral alveolar echinococcosis (CAE).Twenty-five CAE patients underwent F-FDG PET/CT, and the diagnosis was confirmed by clinical and surgical pathology. The F-FDG PET/CT results were subject to visual and semiquantitative analysis, and the difference in F-FDG SUVmax for lesions among the 3 types of CAE was evaluated.In the 25 CAE patients, 62 lesions were detected by F-FDG PET/CT, and these lesions were classified into 3 types, according to the characteristics of the lesion's uptake of F-FDG on PET images: type I, 17 lesions, FDG was concentrated into a mass radioactive distribution in the CAE foci; type II, 28 lesions, FDG presented a annular concentrated radioactive distribution around the CAE foci; type III, 17 lesions, FDG in the CAE foci presented a radioactive distribution with defects and sparse areas. The difference in F-FDG SUVmax between type I and type II CAE was not statistically significant (P > .05), the difference in F-FDG SUVmax between type I and type III CAE was statistically significant (P < .001), and the difference in F-FDG SUVmax between type II and type III CAE was statistically significant (P < .001);The F-FDG PET manifestations of CAE are classified into 3 types. Both type I and type II may have invasive activity, while the lesions of type III CAE show that the focus is relatively stable or at a stationary phase. If there are no definite alveolar echinococcus focus in other sites, these patients can temporarily delay the treatment. It is recommended that the patient should undergo whole body PET/CT once a year to dynamically observe the bioactivity and size of type III CAE lesions and assess the presence of new echinococcus lesions in the rest of the body.

Plasma IL-23 and IL-5 as surrogate markers of lesion metabolic activity in patients with hepatic alveolar echinococcosis

Fluorodeoxyglucose (FDG) uptake by alveolar echinococcosis (AE) liver lesions is a signal of their metabolic activity and of disease progression. In order to find a surrogate marker for this status, we investigated whether parameters of the peripheral and/or periparasitic immune responses were associated with metabolic activity in a prospective case-control study of 30 AE patients and 22 healthy controls. Levels of 18 cytokines and chemokines, representative of innate and adaptive immune responses, were assessed in plasma and peripheral cells of two groups of patients with (MAAE) and without (MIAE) metabolically active lesions, and in the liver of MAAE patients. Mixed cytokine profile was observed in the peripheral blood of AE patients, with a predominance of Th2, Th17 and Treg responses. Among the detected markers only plasma IL-5 and IL-23, more elevated in MAAE patients, were found discriminant. Discrimination between MAAE and MIAE patients obtained by using IL-23 was improved when IL-5 was used in combination. The combination of elevated levels of IL-5 and IL-23 is significantly associated with FDG uptake at PET scan. It offers a new tool for the follow-up of AE patients which could substitute to FDG-PET whenever non-available to assess disease progression.

Diffusion-Weighted MRI for the Initial Viability Evaluation of Parasites in Hepatic Alveolar Echinococcosis: Comparison with Positron Emission Tomography

Objective

More than 70% of hepatic alveolar echinococcosis (HAE) are inoperable. Thus, long-term, or even life-long, pharmacological treatment with benzimidazoles is necessary. For effective treatment, it is of great importance to employ imaging techniques to detect and monitor the non-resectable parasitic viability. Therefore, this study aimed to evaluate diffusion-weighted imaging (DWI) in assessing the viability of HAE in comparison to 18-fluoro-deoxyglucose (18F-FDG) positron emission tomography, combined with computed tomography (PET/CT).

Materials and Methods

Positron emission tomography, computed tomography and DWI (b-values: 0, 800 s/mm²) were retrospectively analysed in eight patients with clinically-verified HAE to, generate the apparent diffusion coefficient (ADC) map. The activity of HAE lesions in both techniques were determined independently by two radiologists according to the following standard: (+), marked focally or perilesionally increased FDG uptake/high signal intensity; (−), a hepatic defect without FDG uptake/no high signal intensity. Every lesion's maximum standardized uptake value (SUV_max) on the PET/CT images and mean ADC values on the parametric ADC maps were measured respectively. Results of PET/CT and DWI were compared on a per-lesion-basis. Pearson's correlation coefficient was assessed for statistical analysis.

Results

A total of 14 HAE lesions were detected. Eight lesions (diameter 3–15 cm) showed perilesional hyper-signal intensity on DWI. This was visualised on PET/CT as increased FDG uptake. They mainly existed in the lesion's border with normal liver parenchyma. Five lesions (diameter < 2 cm) were detected as nodular hyperintensity on DWI and a ‘hot spot’ on PET/CT in the same distribution. One patient, who had received oral drug therapy for three years showed significantly decreased perilesional hyperintensity on the DWI and a hepatic defect without any FDG uptake on PET/CT. Pearson's correlation coefficient indicated a significant inverse correlation of the ADC and the SUV_max (r = −0.67, p < 0.001).

Conclusion

Diffusion-weighted imaging is capable of offering information on visually detecting the HAE lesions' viability and may be useful for routine application in the initial diagnosis of HAE.

Multimodality imaging in diagnosis and management of alveolar echinococcosis: an update

Alveolar echinococcosis is a parasitic disease limited to the northern hemisphere. The disease occurs primarily in the liver and shows a profile mimicking slow-growing malignant tumors. Echinococcus multilocularis infection is fatal if left untreated. It can cause several complications by infiltrating the vascular structures, biliary tracts, and the hilum of the liver. As it can invade the adjacent organs or can spread to distant organs, alveolar echinococcosis can easily be confused with malignancies. We provide a brief review of epidemiologic and pathophysiologic profile of alveolar echinococcosis and clinical features of the disease. This article focuses primarily on the imaging features of alveolar echinococcosis on ultrasonogra-phy, computed tomography, magnetic resonance imaging, diffusion-weighted imaging and positron emission tomography-computed tomography. We also reviewed the role of radiology in diagnosis, management, and follow-up of the disease.

PET/CT in nononcological lung diseases: current applications and future perspectives

Positron emission tomography (PET) combined with computed tomography (CT) is an established diagnostic modality that has become an essential imaging tool in oncological practice. However, thanks to its noninvasive nature and its capability to provide physiological information, the main applications of this technique have significantly expanded.(18)F-labelled fluorodeoxyglucose (FDG) is the most commonly used radiopharmaceutical for PET scanning and demonstrates metabolic activity in various tissues. Since activated inflammatory cells, like malignant cells, predominantly metabolise glucose as a source of energy and increase expression of glucose transporters when activated, FDG-PET/CT can be successfully used to detect and monitor a variety of lung diseases, such as infections and several inflammatory conditions.The added value of FDG-PET/CT as a molecular imaging technique relies on its capability to identify disease in very early stages, long before the appearance of structural changes detectable by conventional imaging. Furthermore, by detecting the active phase of infectious or inflammatory processes, disease progression and treatment efficacy can be monitored.This review will focus on the clinical use of FDG-PET/CT in nonmalignant pulmonary diseases.

The Echinococcoses: Diagnosis, Clinical Management and Burden of Disease

The echinococcoses are chronic, parasitic diseases that are acquired after ingestion of infective taeniid tapeworm eggs from certain species of the genus Echinococcus. Cystic echinococcosis (CE) occurs worldwide, whereas, alveolar echinococcosis (AE) is restricted to the northern hemisphere, and neotropical echinococcosis (NE) has only been identified in Central and South America. Clinical manifestations and disease courses vary profoundly for the different species of Echinococcus. CE presents as small to large cysts, and has commonly been referred to as 'hydatid disease', or 'hydatidosis'. A structured stage-specific approach to CE management, based on the World Health Organization (WHO) ultrasound classification of liver cysts, is now recommended. Management options include percutaneous sterilization techniques, surgery, drug treatment, a 'watch-and-wait' approach or combinations thereof. In contrast, clinical manifestations associated with AE resemble those of a 'malignant', silently-progressing liver disease, with local tissue infiltration and metastases. Structured care is important for AE management and includes WHO staging, drug therapy and long-term follow-up for at least a decade. NE presents as polycystic or unicystic disease. Clinical characteristics resemble those of AE, and management needs to be structured accordingly. However, to date, only a few hundreds of cases have been reported in the literature. The echinococcoses are often expensive and complicated to treat, and prospective clinical studies are needed to better inform case management decisions.

Comprehensive diagnosis and treatment of alveolar echinococcosis: A single-center, long-term observational study of 312 patients in Germany

Alveolar echinococcosis (AE) is the most Iethal human helminthic infection. The malignancy-like disease is rare, but morbidity and treatment costs are high. Objective of the study was to identify factors at baseline and during specific AE therapy influencing the long-term outcome of the disease.

All patients with AE seen at the specialized treatment unit in Ulm between January 1992 and December 2011 were included in the analysis.

The data of 312 patients were analyzed; 108 were diagnosed before 2000 (series A), 204 since 2000 (series B); 290 received specific AE treatment. Patients of series B were more often symptom-free at diagnosis (44.1% vs. 21.3%), had lower disease stages (50.0% vs. 34.2%) and more complete resections (57.7% vs. 20.0%), but higher rates of side effects and drug toxicity (54.1% vs. 40.8%). In series B, more patients remained relapse- or progression-free after 5 years (90.5% vs. 82.8%); after 10 years, the ratio of relapses converged (70.3% vs. 66.9%, p=0.0507). Relapses or progression occurred more often after incomplete surgery or long treatment pauses. The 5-year and 10-year survival rates were 96.9% and 90.6%, respectively, and 17% of the patients were cured.

We observed a shift towards early diagnosis, earlier initiation of specific therapy and more complete resections after 2000. Although diagnosis and treatment of AE pose a challenge, with an individual interdisciplinary management 88.8% of the patients have a favorable outcome.

Proposal of a computed tomography classification for hepatic alveolar echinococcosis

AIM: To establish a computed tomography (CT)-morphological classification for hepatic alveolar echinococcosis was the aim of the study.

METHODS: The CT morphology of hepatic lesions in 228 patients with confirmed alveolar echinococcosis (AE) drawn from the Echinococcus Databank of the University Hospital of Ulm was reviewed retrospectively. For this reason, CT datasets of combined positron emission tomography (PET)-CT examinations were evaluated. The diagnosis of AE was made in patients with unequivocal seropositivity; positive histological findings following diagnostic puncture or partial resection of the liver; and/or findings typical for AE at either ultrasonography, CT, magnetic resonance imaging or PET-CT. The CT-morphological findings were grouped into the new classification scheme.

RESULTS: Within the classification a lesion was dedicated to one out of five “primary morphologies” as well as to one out of six “patterns of calcification”. “primary morphology” and “pattern of calcification” are primarily focussed on separately from each other and combined, whereas the “primary morphology” V is not further characterized by a “pattern of calcification”. Based on the five primary morphologies, further descriptive sub-criteria were appended to types I-III. An analysis of the calcification pattern in relation to the primary morphology revealed the exclusive association of the central calcification with type IV primary morphology. Similarly, certain calcification patterns exhibited a clear predominance for other primary morphologies, which underscores the delimitation of the individual primary morphological types from each other. These relationships in terms of calcification patterns extend into the primary morphological sub-criteria, demonstrating the clear subordination of those criteria.

CONCLUSION: The proposed CT-morphological classification (EMUC-CT) is intended to facilitate the recognition and interpretation of lesions in hepatic alveolar echinococcosis. This could help to interpret different clinical courses better and shall assist in the context of scientific studies to improve the comparability of CT findings.

Evaluation of the Metabolic Activity of Echinococcus multilocularis in Rodents Using Positron Emission Tomography Tracers

PURPOSE

2-Deoxy-2-[(18)F]fluoro-D-glucose ([(18)F]FDG) has been used as a standard clinical positron emission tomography (PET) tracer for the follow-up of the rare but life-threatening parasitic disease alveolar echinococcosis (AE). Given that the disease is endemic in many countries in the northern hemisphere and the diagnosis is still challenging, the aim of our study was to evaluate further clinically relevant PET tracers as possible diagnostic tools for AE in vitro and in vivo.

PROCEDURES

Various clinically used PET tracers were evaluated in vitro and assessed in an in vivo AE animal model based on PET/magnetic resonance (MR) measurements.

RESULTS

In vitro binding assays displayed high uptake of [(18)F]FDG in a cell suspension of E. multilocularis tissue, whereas 3'-deoxy-3'-[(18)F]fluorothymidine ([(18)F]FLT) and [(11)C]choline were found to be taken up strongly by E. multilocularis vesicles. [(18)F]FDG and [(18)F]FLT displayed an elevated uptake in vivo, which appeared as several foci throughout the parasite tissue as opposed to [(18)F]fluoro-azomycinarabinofuranoside ([(18)F]FAZA) and [(11)C]choline.

CONCLUSIONS

Our data clearly demonstrate that the clinically applied PET tracer [(18)F]FDG is useful for the diagnosis and disease staging of AE but also has drawbacks in the assessment of currently inactive or metabolically weak parasitic lesions. The different tested PET tracers do not show the potential for the replacement or supplementation of current diagnostic strategies. Hence, there is still the need for novel diagnostic tools.

Imaging for infection: from visualization of inflammation to visualization of microbes

BACKGROUND

With the development of high-resolution cross-sectional imaging, anatomic identification of most areas of infection has become routine. Imaging a site of infection allows for diagnosis and treatment. In the past, molecular imaging for infection involved mainly the use of radiolabeled leukocytes for functional targeting at infection sites. With the recent development of functional nuclear imaging, bacterial and viral metabolism can also be imaged directly for potential identification of early infection.

METHODS

Review of pertinent English-language literature.

RESULTS

Cross-sectional imaging is used routinely to identify and treat sources of infection in patients with fever, leukocytosis, or unexplained hemodynamic instability. Although ultrasound is preferred for the identification of biliary or hepatic sepsis, computed tomography (CT) has proved to be accurate for the identification and treatment of intra-abdominal fluid collections and abscesses. Biologic imaging is a non-invasive technique that identifies sites of infection in cases in which no definite abnormality is identified via cross-sectional imaging. This is made possible by imaging the accumulation of radioisotopes that have been attached to white blood cells or glucose. Biologic imaging is useful for the identification of anatomic sites where there is inflammation or high metabolic demand. However, a drawback of biologic imaging is that it is not specific for infection. Techniques that image microbes directly increase the specificity of imaging results significantly and can be used to quantify and track infectious processes. For example, radiolabeling of antimicrobial proteins and antibiotics is one technique that has been demonstrated to identify areas of infection accurately in animals but is not currently being used clinically in humans. With the advent of gene therapy, many researchers are inserting the herpes viral thymidine kinase gene into both viruses and bacteria. This allows for tracking of the infectious process by imaging the accumulation of radiolabeled thymidine analogues.

CONCLUSION

This review summarizes standard imaging for infection as it is currently practiced clinically. We will also explore the promising new methods of microbial imaging that are likely to become standards in clinical care in the near future.

Alveolar echinococcosis: correlation between hepatic MRI findings and FDG-PET/CT metabolic activity

OBJECTIVE

To correlate the appearance of alveolar echinococcosis (AE) hepatic lesions in magnetic resonance imaging (MRI) as defined by Kodama, to the metabolic activity visualized in 18-fluoro-deoxyglucose positron emission tomography combined with computed tomography (PET/CT).

MATERIALS AND METHODS

Forty-two patients diagnosed with AE and who underwent both MRI and PET/CT were included. The forty-two hepatic lesions were divided into five types according to Kodama's classification by three independent readers blinded with regard to the PET/CT information. Concerning PET/CT, two independent readers, unaware of the MRI information, considered the results as positive when an increased FDG-uptake was observed at 1 or 3 h after FDG-injection, and as negative when no increased uptake was noted. Inter-observer agreement was assessed by using κ statistics.

RESULTS

Forty-two lesions were counted and the mean diameter of overall evaluated lesions was 6.3 cm. One lesion (2.4%) was categorized as type 1, 11 (26.2%) as type 2, 24 (57.1%) as type 3, 3 (7.1%) as type 4, and 3 (7.1%) as type 5. The inter-observer analysis found a κ coefficient of 0.96. All type-1, 90.9% of type-2 and 87.5% of type-3 lesions showed an increased FDG-uptake on PET/CT images. All non-microcystic AE liver lesions (types 4 and 5) showed no abnormal increased FDG-uptake on PET/CT images. The inter-observer analysis at 1 and 3 h found a κ coefficient of 0.95 and 0.92, respectively.

CONCLUSIONS

In patients with AE liver lesions, the absence of microcysts on MRI is strongly correlated to a metabolically inactive disease.

Development of a specific tracer for metabolic imaging of alveolar echinococcosis: A preclinical study

Positron emission tomography (PET)-computed tomography (CT) using [18F]-fluorodeoxyglucose (FDG) (FDG-PET/CT) is a valuable method for initial staging and follow up of patients with alveolar echinococcosis (AE). However, the cells responsible for FDG uptake have not been clearly identified. The main goal of our study was to evaluate the uptake of PET tracers by the cells involved in the host-parasite reaction around AE lesions as the first step to develop a specific PET tracer that would allow direct assessment of parasite viability in AE. Candidate molecules ([18F]-fluorotyrosine (FET), [18F]-fluorothymidine (FLT), and [18F]-fluorometylcholine (FMC), were compared to FDG by in vitro studies on human leukocytes and parasite vesicles. Our results confirmed that FDG was mainly consumed by immune cells and showed that FLT was the best candidate tracer for parasite metabolism. Indeed, parasite cells exhibited high uptake of FLT. We also performed PET/CT scans in mice infected intraperitoneally with E. multilocularis metacestodes. PET images showed no FDG or FLT uptake in parasitic lesions. This preliminary study assessed the metabolic activity of human leukocytes and AE cells using radiolabeling. Future studies could develop a specific PET tracer for AE lesions to improve lesion detection and echinococcosis treatment in patients. Our results demonstrated that a new animal model is needed for preclinical PET imaging to better mimic human hepatic and/or periparasitic metabolism.

Outcome after Discontinuing Long-Term Benzimidazole Treatment in 11 Patients with Non-resectable Alveolar Echinococcosis with Negative FDG-PET/CT and Anti-EmII/3-10 Serology

Background/Aims

Benzimidazoles are efficacious for treating non-resectable alveolar echinococcosis (AE), but their long-term parasitocidal (curative) effect is disputed. In this study, we prospectively analyzed the potential parasitocidal effect of benzimidazoles and whether normalization of FDG-PET/CT scans and anti-Emll/3-10-antibody levels could act as reliable "in vivo" parameters of AE-inactivation permitting to abrogate chemotherapy with a low risk for AE-recurrence.

Method

This prospective study included 34 patients with non-resectable AE subdivided into group A (n = 11), followed-up after diagnosis and begin of chemotherapy at months 6, 12 and 24, and group B (n = 23) with a medium duration of chemotherapy of 10 (range 2–25) years. All patients were assessed by FDG-PET/CT examinations and anti-EmII/3-10 serology. Chemotherapy was abrogated in patients with normalization of FDG-PET/CT and serum anti-EmII/3-10 levels. These patients were closely followed-up for AE recurrence. Endpoint (parasitocidal efficacy) was defined by the absence of AE-recurrence >24 months after stopping treatment.

Results

Normalization of FDG-PET/CT scan and anti-EmII/3-10 levels occurred in 11 of 34 patients (32%). After abrogation of chemotherapy in these 11 patients, there was no evidence of AE-recurrence within a median of 70.5 (range 16–82) months. However, the patients’ immunocompetence appears pivotal for the described long-term parasitocidal effect of benzimidazoles.

Conclusions

The combination of negative FDG-PET/CT-scans and anti-EmII/3-10 antibody levels seem to be reliable parameters for assessing in vivo AE-larval inactivity after long-term benzimidazole chemotherapy.

Trial Registration

clinicaltrials.gov: NCT00658294

Alveolar echinococcosis is one of the mostly deadly human parasitic diseases if left untreated. The treatment of choice is surgical resection, followed by two years of benzimidazole treatment. Unfortunately, only about 30–40% of patients have a resectable disease, while the others require medical treatment with benzimidazoles. As this therapy is only considered to be parasitostatic and as there are not yet reliable tools to assess parasite viability, the treatment usually is life-long. In this study, we evaluated FDG-PET/CT and antibody levels against the recombinant Emll/3-10 antigen as markers for parasite viability, allowing to select patients in whom chemotherapy could be stopped with low risk of AE-recurrence. Eleven 11 patients were identified with negative FDG-PET/CT-scans and anti-EmII/3-10 antibody levels in whom benzimidazole treatment was stopped with no evidence of AE-recurrence within a median follow-up of 70.5 (range 16–82) months. Therefore, this study provides evidence that benzimidazole treatment is parasitocidal in a subset of patients.

Susceptibility versus resistance in alveolar echinococcosis (larval infection with Echinococcus multilocularis)

Epidemiological studies have demonstrated that the majority of human individuals exposed to infection with Echinococcus spp. eggs exhibit resistance to disease as shown by either seroconversion to parasite--specific antigens, and/or the presence of 'dying out' or 'aborted' metacestodes, not including hereby those individuals who putatively got infected but did not seroconvert and who subsequently allowed no development of the pathogen. For those individuals where infection leads to disease, the developing parasite is partially controlled by host immunity. In infected humans, the type of immune response developed by the host accounts for the subsequent trichotomy concerning the parasite development: (i) seroconversion proving infection, but lack of any hepatic lesion indicating the failure of the parasite to establish and further develop within the liver; or resistance as shown by the presence of fully calcified lesions; (ii) controlled susceptibility as found in the "conventional" alveolar echinococcosis (AE) patients who experience clinical signs and symptoms approximately 5-15 years after infection, and (iii) uncontrolled hyperproliferation of the metacestode due to an impaired immune response (AIDS or other immunodeficiencies). Immunomodulation of host immunity toward anergy seems to be triggered by parasite metabolites. Beside immunomodulating IL-10, TGFβ-driven regulatory T cells have been shown to play a crucial role in the parasite-modulated progressive course of AE. A novel CD4+CD25+ Treg effector molecule FGL2 recently yielded new insight into the tolerance process in Echinococcus multilocularis infection.

Innovation in hepatic alveolar echinococcosis imaging: best use of old tools, and necessary evaluation of new ones

Hepatic Alveolar Echinococcosis (HAE), caused by larvae of Echinococcus multilocularis, is a rare but potentially lethal parasitic disease. The first diagnostic suspicion is usually based on hepatic ultrasound exam performed because of abdominal symptoms or in the context of a general checkup; HAE diagnosis may thus also be an incidental finding on imaging. The next step should be Computed Tomography (CT) or Magnetic Resonance Imaging (MRI). They play an important role in the initial assessment of the disease; with chest and brain imaging, they are necessary to assess the PNM stage (parasite lesion, neighboring organ invasion, metastases) of a patient with AE. Performed at least yearly, they also represent key exams for long-term follow-up after therapeutic interventions. Familiarity of radiologists with HAE imaging findings, especially in the endemic regions, will enable earlier diagnosis and more effective treatment. Fluorodeoxyglucose Positron Emission Tomography (FDG-PET) is currently considered to be the only noninvasive, albeit indirect, tool for the detection of metabolic activity in AE. Delayed acquisition of images (3 hrs after FDG injection) enhances its sensitivity for the assessment of lesion metabolism and its reliability for the continuation/withdrawal of anti-parasite treatment. However, sophisticated equipment and high cost widely limit PET/CT use for routine evaluation. Preliminary studies show that new techniques, such as contrast-enhanced ultrasound (US), Dual Energy CT or Spectral CT, and Diffusion-Weighted MRI, might also be useful in detecting the blood supply and metabolism of lesions. However, they cannot be recommended before further evaluation of their reliability in a larger number of patients with a variety of locations and stages of AE lesions.

Echinococcus metacestode: in search of viability markers

Epidemiological studies have demonstrated that most humans infected with Echinococcus spp. exhibit resistance to disease. When infection leads to disease, the parasite is partially controlled by host immunity: in case of immunocompetence, the normal alveolar echinococcosis (AE) or cystic echinococcosis (CE) situation, the metacestode grows slowly, and first clinical signs appear years after infection; in case of impaired immunity (AIDS; other immunodeficiencies), uncontrolled proliferation of the metacestode leads to rapidly progressing disease. Assessing Echinococcus multilocularis viability in vivo following therapeutic interventions in AE patients may be of tremendous benefit when compared with the invasive procedures used to perform biopsies. Current options are F18-fluorodeoxyglucose-positron emission tomography (FDG-PET), which visualizes periparasitic inflammation due to the metabolic activity of the metacestode, and measurement of antibodies against recEm18, a viability-associated protein, that rapidly regresses upon metacestode inactivation. For Echinococcus granulosus, similar prognosis-associated follow-up parameters are still lacking but a few candidates may be listed. Other possible markers include functional and diffusion-weighted Magnetic Resonance Imaging (MRI), and measurement of products from the parasite (circulating antigens or DNA), and from the host (inflammation markers, cytokines, or chemokines). Even though some of them have been promising in pilot studies, none has been properly validated in an appropriate number of patients until now to be recommended for further use in clinical settings. There is therefore still a need to develop reliable tools for improved viability assessment to provide the sufficient information needed to reliably withdraw anti-parasite benzimidazole chemotherapy, and a basis for the development of new alternative therapeutic tools.

Acoustic structure quantification (ASQ): a new tool in sonographic examination of liver lesions in hepatic alveolar echinococcosis

PURPOSE

Qualitative and quantitative acoustic structure quantification (ASQ) is a new, noninvasive sonographic imaging method based on B-mode. This prospective clinical pilot study aims to answer the question whether delineation and measurement of liver lesions in hepatic alveolar echinococcosis (HAE) can be improved by ASQ. Furthermore, this is the first pilot study to explore how ASQ parameters in HAE lesions develop.

METHODS

A total of 24 patients (male = 13/female = 11, mean age = 52 years (16-85), mean disease duration = 68 months (1-334)) with HAE were examined with ASQ using a Toshiba Aplio 500 unit. ASQ parameters were measured in HAE liver lesions and in adjacent non-tumor parenchyma. Quantitative analysis was performed offline using ASQ quantification software.

RESULTS

Subjectively parasitic tumors in HAE appear more prominent in color-coded ASQ imaging, but the size of lesions measured in ASQ mode does not differ from size measurements in B-mode. Median focal disturbance ratio (FD ratio) in lesions was 3 (0.1-3), compared with 0.5 (0.1-1.8) in surrounding liver parenchyma (p < 0.0001). Statistical comparison of other ASQ parameters (mode, average, standard deviation) shows results that are similarly significant with p values between p < 0.0001 and p < 0.0018.

CONCLUSION

ASQ is a promising sonographic method for examination and quantification of structural changes of liver parenchyma in HAE lesions.

The first locally acquired human infection of Echinococcus multilocularis in The Netherlands

In the northern part of Western Europe, Echinococcus multilocularis is primarily detected in and spreading among foxes. The present case marks E. multilocularis as an emerging pathogen for humans, as it describes the first human case of probably locally acquired E. multilocularis in The Netherlands, with various interesting clinical aspects.

The molecular imaging approach to image infections and inflammation by nuclear medicine techniques

Inflammatory and infectious diseases are a heterogeneous class of diseases that may be divided into infections, acute inflammation and chronic inflammation. Radiological imaging techniques have, with the exception of functional MRI, high sensitivity but lack in specificity. Nuclear medicine techniques, by contrast, allow the in vivo detection in humans of different physiologic and pathologic phenomena and offer noninvasive tools to detect early pathophysiological changes before anatomical changes occur. In this review, we highlight the role of nuclear medicine in inflammation/infection with emphasis on molecular imaging for in vivo histological characterization of affected tissues for diagnostic purposes and follow-up of therapies. We also describe the clinical indications of all available radiopharmaceuticals in the light of the newly available guidelines.

Should possible recurrence of disease contraindicate liver transplantation in patients with end-stage alveolar echinococcosis? A 20-year follow-up study

Liver transplantation (LT) is currently contraindicated in patients with residual or metastatic alveolar echinococcosis (AE) lesions. We evaluated the long-term course of such patients who underwent LT and were subsequently treated with benzimidazoles. Clinical, imaging, serological, and therapeutic data were collected from 5 patients with residual/recurrent AE lesions who survived for more than 15 years. Since 2004, [(18) F]-2-fluoro-2-deoxyglucose (FDG)-positron emission tomography (PET) images were available, and the levels of serum antibodies (Abs) against Echinococcus multilocularis-recombinant antigens were evaluated. Median survival time after LT was 21 years. These patients were from a prospective cohort of 23 patients with AE who underwent LT: 5 of 8 patients with residual/recurrent AE and 4 of 9 patients without residual/recurrent AE were alive in September 2009. High doses of immunosuppressive drugs, the late introduction of therapy with benzimidazoles, its withdrawal due to side effects, and nonadherence to this therapy adversely affected the prognosis. Anti-Em2(plus) and anti-rEm18 Ab levels and standard FDG-PET enabled the efficacy of therapy on the growth of EA lesions to be assessed. However, meaningful variations in Ab levels were observed below diagnostic cutoff values; and in monitoring AE lesions, images of FDG uptake taken 3 hours after its injection were more sensitive than images obtained 1 hour after its injection. In conclusion, benzimidazoles can control residual/recurrent AE lesions after LT. Using anti-rEm18 or anti-Em2(plus) Ab levels and the delayed acquisition of FDG-PET images can improve the functional assessment of disease activity. The potential recurrence of disease, especially in patients with residual or metastatic AE lesions, should not be regarded as a contraindication to LT when AE is considered to be lethal in the short term.

Long-term results of hepatectomy for patients with alveolar echinococcosis: a single-center experience

BACKGROUND

Hepatectomy is the first-line treatment for alveolar echinococcosis (AE) if complete resection is feasible. However, a strategy for the treatment of patients with AE in whom the tumor cannot be resected completely remains to be defined.

STUDY DESIGN

Data were retrospectively collected from 188 consecutive patients between 1984 and 2009. Overall survival (OS), progression-free survival (PFS), and risk factors were analyzed in patients classified into 3 groups (group A: complete resection, group B: reduction surgery, and group C: drainage or exploratory laparotomy).

RESULTS

In group A (n = 119), the 10-, 15-, and 20-year OS was 98.9%. In group B (n = 63), the 10-, 15-, and 20-year OS was 97.1%, 92.8%, and 61.9%. In group C (n = 6), the 10- and 15-year OS was 50.0% and 33.3%. Patients in groups A and B had better prognoses than those in group C (p < 0.001). In group A, the 10-, 15-, and 20-year PFS was 96.5%, 94.4%, and 94.4%. In group B, the 10-, 15-, and 20-year PFS was 87.1%, 71.6%, and 61.4%. In group C, the 10- and 15-year PFS was 50.0% and 33.3%. Patients in group A had better PFS than those in groups B and C (p < 0.001). Curability was the only independent factor for both OS and PFS by multivariate analysis.

CONCLUSIONS

Although the most effective therapy for AE is complete resection, a better prognosis can be achieved by reduction surgery and/or adjuvant albendazole therapy for patients with AE that cannot be completely resected.

Personalized management of patients with inoperable alveolar echinococcosis undergoing treatment with albendazole: usefulness of positron-emission-tomography combined with serological and computed tomography follow-up

The present study aimed to identify a sub-group of inoperable alveolar echinococcosis (AE) patients undergoing long-term treatment with benzimidazole (BZM) who presented with an evolution suggestive of a parasitocidal effect. An evolution compatible with parasite death was observed in five patients.

Brain and lung metastasis of alveolar echinococcosis in a refugee from a hyperendemic area

Alveolar echinococcosis (AE) of the liver with cerebral and pulmonary metastasis was diagnosed in a Tibetan monk who initially presented with severe headache to an emergency department in Germany. Multiple lesions with perifocal oedema and severe compression of the third ventricle were seen with computed tomography (CT) of the brain. Glioma or cerebral metastasis of a hitherto undiagnosed abdominal or pulmonary malignancy was suspected. CT scans of the lung and liver demonstrated further tumorous masses. Magnetic resonance imaging of the brain revealed the cystic nature of the cerebral lesions and the patient had a highly positive serology for AE. The echinococcal aetiology of the brain lesions was confirmed by PCR for this refugee from an area where two disease entities, AE and cystic echinococcosis, are hyperendemic.

Role of modern imaging techniques for diagnosis of infection in the era of 18F-fluorodeoxyglucose positron emission tomography

During the past several years, it has become quite evident that positron emission tomography (PET) with 18F-fluorodeoxyglucose (FDG) imaging can play a major role in the management of patients with suspected infection. Particularly, several groups have demonstrated that this powerful imaging methodology is very effective in the evaluation of osteomyelitis, infected prostheses, fever of unknown origin, and AIDS. In view of its extraordinary sensitivity in detecting disease activity and the ability to quantitate the degree of FDG uptake, PET might prove to be an appropriate modality for monitoring disease activity and evaluating response to therapy. FDG-PET has many advantages over existing imaging techniques for the diagnosis of infectious diseases. These include feasibility of securing diagnostic results within 1.5 to 2 h, excellent spatial resolution, and accurate anatomical localization of sites of abnormality. The availability of PET/computed tomography as a practical tool has further enhanced the role of metabolic imaging in many settings. In the future, this modality is very likely to be employed on a routine basis for detecting, characterizing, and monitoring patients with suspected and proven infection.