Hydatid disease is a major healthcare problem worldwide caused by infection that commonly affects the liver. Treatments for hydatid disease depend on how advanced the disease is and if the infection is active or not. Currently, doctors decide what stage the disease is at by looking at the appearance of liver on scans and by performing blood tests. It is however still very difficult to be certain if a treatment is working and when is the right moment to start and stop medication. Magnetic Resonance Imaging (MRI) scanning is a safe and non-invasive way of imaging the liver that can provide detailed information not just about what the liver looks like but also other information about the chemical composition of normal and diseased liver tissue. MRI is already widely used in the NHS for many liver conditions but it is unknown whether analysing the chemical composition will help decide on the stage and activity of hydatid liver disease. This study will allow comparison between MRI information about liver structure and composition with existing methods of assessing disease stage. If fluid is later obtained from the liver as part of usual clinical care (either using a needle with ultrasound or at the time of surgery), this study will also compare information about the fluid composition obtained from MRI scanning, with the results obtained when analysing the fluid in the lab. This will help to develop a more accurate way of non-invasively assessing hydatid disease in the liver, in the future.

Cystic echincoccosis (CE), caused by infection with the dog tapeworm, is a major worldwide healthcare problem with increasing prevalence in the developed world. Approximately 75% of CE involves the liver, with treatments incurring significant cost and patient morbidity.

The key to CE treatment is correct identification of active infection but differentiation from sterile disease is highly problematic. Current treatment guidelines base activity assessment on morphological assessment with ultrasound (US), serology and light-microscopy of samples obtained at aspiration/surgery when available. Serology however can take many years to become negative even following successful treatment and US evaluation is subjective. Assessment of disease 'activity' is therefore a major challenge, particularly once patients are undergoing treatment. The lack of accurate tools to assess treatment response has undermined the development of management guidelines, particularly concerning the optimum length of chemotherapy treatment and indications for surgical/image-guided intervention.

Quantitative MR methods present a potential solution to this challenge. Magnetic Resonance Spectroscopy (MRS) has shown promising ex vivo results in detecting the biochemical "signature" of active infection in cyst fluid, but has yet to be applied clinically. Alternative approaches including T1 mapping, susceptibility mapping and Diffusion Weighted Imaging/Intra-voxel Incoherent Motion are also potentially useful, but have little supportive data to date.

Non-invasive biomarkers of CE activity are therefore essential to defining specific treatment endpoints, particularly in the context of chemotherapy. Multiple quantitative MR methods could be used to develop composite biomarkers for disease activity. Identifying a new quantitative radiological 'fingerprint' for each stage of the natural life-cycle of hepatic CE will enable improved diagnosis and therapeutic triage.

To date, in vivo liver quantitative MRI has not yet been applied to this cohort of patients, thus representing a novel application of this technology to address an important clinical question.

With this pilot study, the investigators aim to demonstrate the potential of quantitative MRI methods in the assessment of active/inactive hepatic CE.

Inclusion Criteria for Control group:

• All patients must have cystic lesions which must exceed 30 mm in diameter.
• All patients must be fasted and avoid caffeinated fluids for at least 4 hours prior to the scan.
• All patients must be aged 16 or over and able to provide informed consent.

Inclusion Criteria for the CE group:

• All patients must have hepatic CE, as confirmed by positive serology, with lesions identified on teh standard of care MRI/CT scan, one or more of which must exceed 20 mm in diameter.
• All patients must be fasted and avoid caffeinated fluids for at least 4 hours prior to the scan.
• All patients must be aged 16 or over and able to provide informed consent.

Exclusion Criteria:

• Pregnancy
• Any contraindication to MRI (pacemakers, metallic implants, claustrophobia ect.)
• Inability to give consent

Recruitment will take place at the hydatid liver disease multidisciplinary team meetings where patients are discussed and considered for inclusion. These patients can be recruited via outpatient consultation clinics.