Neuroinflammation PET Imaging: Current Opinion and Future Directions

Abstract

Neuroinflammation is a key pathologic hallmark of numerous neurologic diseases, however, its exact role in vivo is yet to be fully understood. PET imaging enables investigation, quantification, and tracking of different neuroinflammation biomarkers in living subjects longitudinally. One such biomarker that has been imaged extensively using PET is translocator protein 18 kDa (TSPO). Although imaging TSPO has yielded valuable clinical data linking neuroinflammation to various neurodegenerative diseases, considerable limitations of TSPO PET have prompted identification of other more cell-specific and functionally relevant biomarkers. This review analyzes the clinical potential of available and emerging PET biomarkers of innate and adaptive immune responses, with mention of exciting future directions for the field.

Keywords: biomarker validation; clinical imaging; molecular imaging; neuroinflammation; positron emission tomography.

FIGURE 1.

TSPO PET imaging shows response to immunomodulatory therapy, myeloperoxidase inhibitor AZD3241, in representative PD patient. (Modified from (10).)

FIGURE 2.

Human cellular expression of neuroimmune imaging biomarkers. Single arrowhead indicates basal expression in healthy humans whereas double arrowhead indicates altered expression in the context of neuroinflammation.

FIGURE 3.

In vitro autoradiography examining postmortem human AD brain tissue vs. control using ¹¹C-CPPC. 1 Ci = 37 GBq. (Modified from (25).)