Avaliação de métodos de quantificação de imagens PET com [11C]-(R)-PK11195 na investigação da esclerose múltipla

Abstract

The activation of microglia is an important response to inflammatory processes in the central nervous system (CNS). There has been an increase in the number of researches in positron emission tomography (PET) using the radiotracer [11C]-(R)-PK11195, a selective ligand for TSPO, present at low levels in the healthy CNS. Although the literature brings many quantitative methods to analyze [11C]-(R)-PK11195 PET brain images, there is no standardized method of analysis applicable in clinical practice. Limitations involve the need for arterial blood sampling for the input function acquisition, aiming absolute quantification of kinetic parameters, such as the binding potential. When the arterial input function is not acquired, the use of models based on a reference region has quantification errors, since there is no brain region free of [11C]-(R)-PK11195 specific binding. The aim of this study is to investigate methods of quantitative and semiquantitative analysis of [11C]-(R)-PK11195 PET brain images, identifying limitations and capabilities. This work is inserted into a clinical study of patients with relapsing-remitting multiple sclerosis (MS) in treatment with fingolimod. There will be used [11C]-(R)-PK11195 PET brain images and structural T1-weighted magnetic resonance images. Methods of quantitative and semiquantitative analyzes will be compared, taking into consideration the specific aspects of MS. In the cross-sectional analysis, the use of SUVRWM in juxtacortical and periventricular regions presented the best results in differentiate between groups of patients with MS and the healthy control group. In the longitudinal analysis, the use of SUVRWM and SUVRCB may indicate the [11C]-(R)-PK11195 uptake behavior over time, and such measurements may be potential indicators of MS evolution when applied in the juxtacortical and periventricular regions. In conclusion, among the methods analyzed, SUVRWM method shows promising and satisfactory results, especially when applied to juxtacortical and periventricular regions.