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

The aim of this study is to determine whether there is an increase in the TSPO PET signal (measured with the radioligand \[11C\]PBR28) in the lungs of patients living with PAH relative to age matched controls. If so, TSPO PET may be a useful technique to non-invasively monitor response to therapy. To do this, we will perform 2 \[11C\]PBR28 PET scans. The first will quantify the total \[11C\]PBR28 PET signal. This signal is a combination of the specific signal (VS) and the nonspecific signal (VND). The second scan will be performed following dosing with an unlabelled TSPO ligand. By directly measuring the total \[11C\]PBR28 signal (scan 1) and the nonspecific \[11C\]PBR28 signal (scan 2) we can therefore calculate the specific \[11C\]PBR28 signal, and hence the amount of TSPO in the lung.