The ability to label specific cells and image their natural movements in vivo would allow researchers to investigate the mechanisms of disease progression. In addition, cell-based therapy, especially stem cell therapy, requires non-invasive monitoring of transplanted cells to follow their bio-distribution and biological function. Because of recent interest in stem cell treatment, several methods have been investigated for in vivo cell tracking. The investigators propose to assess whether the magnetic resonance imaging (MRI) contrast agent Endorem (superparamagnetic particles of iron oxide) can be used to label cells for in vivo tracking using MRI. The investigators will use 20 healthy human volunteers to:

1. Assess the feasibility of imaging Endorem-labelled cells in vivo
2. Compare the distribution of Endorem-labelled cells with that of intravenous injection of Endorem

Inclusion Criteria:

• Healthy volunteers
• Age >18 years

Exclusion Criteria:

• Pregnancy
• Contraindication to MRI scanning (detected by safety questionnaire) including severe claustrophobia
• Inability or refusal to give informed consent
• Renal or hepatic dysfunction
• HIV/hepatitis B/ hepatitis C/ HTLV/ syphilis
• Intercurrent illness
• Blood dyscrasias