Molecular Imaging of Pituitary Adenomas

Background: Pituitary adenomas affect 10% of the population. Surgery offers the most cost-effective treatment modality but cure rates are only 40-70%, in part due to the limitations of Magnetic Resonance Imaging (MRI) in visualising small tumours (up to 40% are undetected) and discriminating adenomatous tissue from healthy pituitary or post-surgical change. Positron emission tomography (PET) imaging may improve localisation but current tracers have short half-lives and are unsuitable for routine use. The dopaminergic system regulates pituitary growth and function, as evidenced by the use of dopamine D2 receptor agonists as medical therapy. Dopaminergic PET tracers, including 18F-FDOPA (6-\[18F\]-L-fluoro-L-3,4-dihydroxyphenylalanine) and 18F (fluorine 18)-Fallypride (which binds to D2/D3 receptors), might thus improve management by enhancing tumour discrimination and quantifying D2 receptor expression. Aim: To establish whether imaging changes in dopaminergic transmission and receptor function has the potential to improve localisation of pituitary adenomas. Methods: Subjects with pituitary adenomas will undergo 18F-FDOPA and 18F-Fallypride PET scans in addition to standard pituitary MRI. Quantification of binding potential combined with MRI co-registration to provide enhanced anatomical definition will be applied. In vivo D2 receptor binding will be correlated with ex vivo D2 receptor mRNA (messenger ribonucleic acid) and protein expression from tumour samples removed at surgery.

Sex

All

Minimum age

16 Years

Inclusion Criteria:

* Confirmed pituitary adenoma for whom pituitary imaging is indicated as part of standard clinical management

Exclusion Criteria:

* Pregnancy, breastfeeding and any contraindications to MRI or intravenous contrast administration