ABSTRACT
BACKGROUND: The aim of this study was to assess the effectiveness of fluorine-18 fluorodeoxyglucose (FDG) PET-CT and dynamic contrast-enhanced (DCE) MRI in differentiating tumor progression and radiation injury in patients with indeterminate enhancing lesions after radiation therapy (RT) for brain malignancies. METHODS: Patients with indeterminate enhancing brain lesions on conventional MRI after RT underwent brain DCE-MRI and PET-CT in a prospective trial. Informed consent was obtained. Lesion outcomes were determined by histopathology and/or clinical and imaging follow-up. Metrics obtained included plasma volume (Vp) and volume transfer coefficient (K(trans)) from DCE-MRI, and maximum standardized uptake value (SUVmax) from PET-CT; lesion-to-normal brain ratios of all metrics were calculated. The Wilcoxon rank sum test and receiver operating characteristic analysis were performed. RESULTS: The study included 53 patients (29 treated for 29 gliomas and 24 treated for 26 brain metastases). Progression was determined in 38/55 (69%) indeterminate lesions and radiation injury in 17 (31%). Vpratio (VP lesion/VP normal brain, P < .001), K(trans) ratio (P = .002), and SUVratio (P = .002) correlated significantly with diagnosis of progression versus radiation injury. Progressing lesions exhibited higher values of all 3 metrics compared with radiation injury. Vpratio had the highest accuracy in determining progression (area under the curve = 0.87), with 92% sensitivity and 77% specificity using the optimal, retrospectively determined threshold of 2.1. When Vpratio was combined with K(trans) ratio (optimal threshold 3.6), accuracy increased to 94%. CONCLUSIONS: Vpratio was the most effective metric for distinguishing progression from radiation injury. Adding K(trans) ratio to Vpratio further improved accuracy. DCE-MRI is an effective imaging technique for evaluating nonspecific enhancing intracranial lesions after RT.
Subject(s)
Brain Neoplasms/diagnostic imaging , Brain/pathology , Positron Emission Tomography Computed Tomography , Radiation Injuries/pathology , Adult , Aged , Brain Neoplasms/pathology , Female , Fluorodeoxyglucose F18 , Glioma/diagnostic imaging , Humans , Magnetic Resonance Imaging/methods , Male , Middle Aged , Multimodal Imaging/methods , Positron Emission Tomography Computed Tomography/methods , Prospective Studies , Radiation Injuries/diagnosisABSTRACT
Competitive (13)C and (18)O kinetic isotope effects (KIEs) on CO2 reduction catalyzed by Re(bpy)(CO)3Cl () under photocatalytic conditions and using Na(Hg) amalgam as a sacrificial reducing agent are reported. The analysis of the measured KIEs rules out the outer-sphere electron transfer mechanism and indicates that CO2 binding to the reduced rhenium complex is the rate determining step in the reduction of CO2 by under these conditions.
