Important consideration must be done in the analysis of the selected papers: with the exception of the 1st generation radioligand (R)-11C-PK11195, the affinity with which the 2nd generation radioligands bind to the TSPO protein is strongly affected by the rs6971 SNP since all the studies examined showed that the uptake in both PD patients and healthy subjects is significantly higher in HABs in respect to MABs and LABs. The gene discussed is TSPO; the disease is Parkinson disease.