A blood-free modeling approach for the quantification of the blood-to-brain tracer exchange in TSPO PET imaging

Introduction: Recent evidence suggests the blood-to-brain influx rate (K1) in TSPO PET imaging as a promising biomarker of blood–brain barrier (BBB) permeability alterations commonly associated with peripheral inflammation and heightened immune activity in the brain. However, standard compartmental modeling quantification is limited by the requirement of invasive and laborious procedures for extracting an arterial blood input function. In this study, we validate a simplified blood-free methodologic framework for K1 estimation by fitting the early phase tracer dynamics using a single irreversible compartment model and an image-derived input function (1T1K-IDIF). Methods: The method is tested on a multi-site dataset containing 177 PET studies from two TSPO tracers ([11C]PBR28 and [18F]DPA714). Firstly, 1T1K-IDIF K1 estimates were compared in terms of both bias and correlation with standard kinetic methodology. Then, the method was tested on an independent sample of [11C]PBR28 scans before and after inflammatory interferon-α challenge, and on test–retest dataset of [18F]DPA714 scans. Results: Comparison with standard kinetic methodology showed good-to-excellent intra-subject correlation for regional 1T1K-IDIF-K1 (ρintra = 0.93 ± 0.08), although the bias was variable depending on IDIF ability to approximate blood input functions (0.03–0.39 mL/cm3/min). 1T1K-IDIF-K1 unveiled a significant reduction of BBB permeability after inflammatory interferon-α challenge, replicating results from standard quantification. High intra-subject correlation (ρ = 0.97 ± 0.01) was reported between K1 estimates of test and retest scans. Discussion: This evidence supports 1T1K-IDIF as blood-free alternative to assess TSPO tracers’ unidirectional blood brain clearance. K1 investigation could complement more traditional measures in TSPO studies, and even allow further mechanistic insight in the interpretation of TSPO signal

The relationship of personal resources with symptom severity and psychosocial functioning in persons with schizophrenia: results from the Italian network for Research on Psychoses study

The relationships of personal resources with symptom severity and psychosocial functioning have never been tested systematically in a large sample of people with schizophrenia. We applied structural equation models to a sample of 921 patients with schizophrenia collected in a nationwide Italian study, with the aim to identify, among a large set of personal resources, those that may have an association with symptom severity or psychosocial functioning. Several relevant demographic and clinical variables were considered concurrently. Poor service engagement and poor recovery style, as well as older age and younger age at onset, were related to greater symptom severity and poorer social functioning. Higher resilience and higher education were related to better social functioning only. Poor problem-focused coping and internalized stigma, as well as male gender and depression, were related to symptom severity only. The explored variables showed distinctive and partially independent associations with symptom severity and psychosocial functioning. A deeper understanding of these relationships may inform treatment decisions