ABSTRACT
Electroencephalography (EEG) is often employed to measure electrical activity in the living human brain. Simulation studies can help unravel how the brain electrical activity pattern generates the EEG signal, still a widely unresolved question. This article describes a method to simulate brain electrical activity by using neuronal populations of a neural mass model. Implementing these populations in a finite element model of the head offers the opportunity to investigate the influence of each group of neurons to the scalp potential. This model is based on structural magnetic resonance imaging data to specify tissue composition, and diffusion tensor imaging data to model local anisotropy. We simulated the EEG signals of five neuronal populations generating α waves in the visual cortex. Our results indicate that radially oriented sources dominate over tangential sources in the generation of the scalp signal. Investigating the influence of anisotropic conductivity, we found small differences in topography and phase and larger ones for the potential amplitude compared with an isotropic conductivity distribution. The outcome of this article is a fast method based on superposition of sources for simulating time-dependent EEG signals, which can be used for further studies of neurodegenerative diseases.
Subject(s)
Alpha Rhythm/physiology , Brain Mapping/methods , Electroencephalography/methods , Evoked Potentials, Visual/physiology , Models, Neurological , Nerve Net/physiology , Visual Cortex/physiology , Computer Simulation , Diagnosis, Computer-Assisted/methods , Humans , Male , Middle Aged , Neural Conduction/physiology , Organ Size/physiology , Reproducibility of Results , Sensitivity and SpecificityABSTRACT
PURPOSE: In this study, the contrasting properties of human serum albumin nanoparticles (HSA-NPs) loaded with gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA) and coated with transferrin in MRI in mice are evaluated. PROCEDURES: HSA-NPs were conjugated with Gd-DTPA (Gd-HSA-NPs) and coupled with transferrin (Gd-HSA-NP-Tf). Mice underwent MRI before or after injection of Gd-DTPA, Gd-HSA-NP, or Gd-HSA-NP-Tf. RESULTS: All the studied contrast agents provided a contrast enhancement (CE) in the blood, heart muscle, and liver. Compared to Gd-DTPA, CE with HSA-NP was achieved at lower Gd doses. Gd-HSA-NP-Tf yielded significantly higher CE than Gd-HSA-NP in the skeletal muscle, blood, cardiac muscle, and liver (p < 0.05). Gd-HSA-NP-Tf achieved a significantly higher CE than Gd-HSA-NP and Gd-DTPA in the blood, cardiac muscle, and liver (p < 0.05). In the brain, only Gd-HSA-NP-Tf was found to cause a significant CE (p < 0.05). CONCLUSIONS: The Gd-HSA nanoparticles have potential as MRI contrast agents. In particular, Gd-HSA-NP-Tf has a potential as a specific contrast agent for the brain, while the blood-brain barrier is still intact, as well as in the heart, liver, and skeletal muscle.
Subject(s)
Albumins/pharmacokinetics , Contrast Media/chemistry , Contrast Media/pharmacokinetics , Gadolinium DTPA/pharmacokinetics , Magnetic Resonance Imaging/methods , Nanoparticles/chemistry , Transferrin/pharmacokinetics , Albumins/chemistry , Analysis of Variance , Animals , Gadolinium DTPA/chemistry , Humans , Male , Mice , Serum Albumin/chemistry , Serum Albumin/pharmacokinetics , Signal-To-Noise Ratio , Tissue Distribution , Transferrin/chemistryABSTRACT
Different from regular small molecule contrast agents, nanoparticle-based contrast agents have a longer circulation time and can be modified with ligands to confer tissue-specific contrasting properties. We evaluated the tissue distribution of polymeric nanoparticles (NPs) prepared from human serum albumin (HSA), loaded with gadolinium-diethylenetriaminepentaacetic acid (Gd-DTPA) (Gd-HSA-NP), and coated with folic acid (FA) (Gd-HSA-NP-FA) in mice by magnetic resonance imaging (MRI). FA increases the affinity of the Gd-HSA-NP to FA receptor-expressing cells. Clinical 3 T MRI was used to evaluate the signal intensities in the different organs of mice injected with Gd-DTPA, Gd-HSA-NP, or Gd-HSA-NP-FA. Signal intensities were measured and standardized by calculating the signal to noise ratios. In general, the NP-based contrast agents provided stronger contrasting than Gd-DTPA. Gd-HSA-NP-FA provided a significant contrast enhancement (CE) in the brain (p â=â .0032), whereas Gd-DTPA or Gd-HSA-NP did not. All studied MRI contrast agents showed significant CE in the blood, kidney, and liver (p < .05). Gd-HSA-NP-FA elicited significantly higher CE in the blood than Gd-HSA-NP (p â=â .0069); Gd-HSA-NP and Gd-HSA-NP-FA did not show CE in skeletal muscle and gallbladder; Gd-HSA-NP, but not Gd-HSA-NP-FA, showed CE in the cardiac muscle. Gd-HSA-NP-FA has potential as an MRI contrast agent in the brain.
