**3.5 Measurement of neuroinflammation in PD**

As discussed above in the context of AD, microglial activation is the body's natural response to brain injury and associated neuroinflammation. Reflecting this, [11C]PK11195 and [11C]PBR28 have been developed to image microglial activation, and recent studies have explored the use of [11C]PK11195 PET in PD patients. Such studies report significant increases in [11C]PK11195 uptake in striatal and extrastriatal regions of PD patients when compared to healthy control subjects (Gerhard, et al., 2006; Ouchi, et al., 2005; Pavese and Brooks, 2009). These findings, which have been correlated with reduced striatal DAT binding (Ouchi, et al., 2005), suggest that significant microglial activation (and associated neuroinflammation) could contribute to dopaminergic neuron loss in PD. This represents an avenue of research that has yet to be extensively explored.
