Quantifying 18kDa TSPO Expression in the Lung in Pulmonary Artery Hypertension (PAH)

Inclusion Criteria: Able to provide written informed consent prior to any study mandated procedures. Able to lie comfortably on back for up to 90 minutes at a time. Fertile females (women of childbearing potential) are eligible to participate after a negative highly sensitive pregnancy test, if they are taking a highly effective method of contraception other than the oral contraceptive pill until the end of relevant systemic exposure. Male participants who are fertile are eligible to participate if they are willing to comply with the contraceptive requirements Exclusion Criteria: Unable to provide informed consent and/or are non-fluent speakers of the English language TT Genotype at the rs6971 locus Clinically-significant renal disease (confirmed by creatinine clearance \<30 ml/min per 1.73m2) Clinically-significant liver disease (confirmed by serum transaminases \>2 times than upper normal limit) Anaemia confirmed by haemoglobin concentration \<10 g/dl Sickle cell disease or thalassaemia History of uncontrolled systemic hypertension Acute infection (including eye, dental, and skin infections) Chronic inflammatory disease including HIV, and Hepatitis B Women of childbearing potential who are pregnant or breastfeeding Patients who have received an Investigational Medicinal Product (IMP) within 5 half-lives of the last dose of the IMP or 1 month (which ever is greater) before the baseline visit Participation in a research study involving significant ionisation radiation within the last 3 years Significant radiation exposure other than dental X-rays in last 1 year Positive Allen's test. \-