Investigation of time-activity curve behavior in dynamic [11C]-(R)-PK11195 PET in cortical brain regions: Preliminary results

Abstract

Dynamic Positron Emission Tomography (PET) allows quantification of underlying physiological processes in a tissue or organ of interest by modeling the radioactivity concentration measured in time (time-activity curve, i.e. TAC). Although the [11C]-(R)-PK11195 PET radiotracer binds to activated microglia and therefore images neuroinflammation, its quantification is still challenging. The aim of this study was to investigate a novel method for analyzing [11C]-(R)-PK11195 TAC behavior from dynamic PET. Seven healthy subjects underwent dynamic 60, min [11C]-(R)-PK11195 PET scans, and TACs were generated for 30 brain cortical regions using the AAL-Merged atlas. The proposed method supposes healthy subjects have similar TACs, which allows the construction of a “healthy template”. Then, TACs of patients can be compared to the healthy template to determine the likelihood that their behavior is abnormal. To evaluate the differences between a healthy region and an inflamed region, a cut-off value for abnormality was created. The method was then tested on a multiple sclerosis (MS) patient. The proposed method was able to identify a number of brain cortical regions with distinct behavior in one MS patient as compared to the healthy template. Further studies are required to evaluate the applicability of the proposed method with additional MS patients, and with data acquired in different scanners and reconstructed with other algorithms.