The Hybrid System for the Magnetic Characterization of Superparamagnetic Nanoparticles.

The characterization of nanoparticles is crucial in several medical applications, such as hyperthermic therapy, which heats superparamagnetic nanoparticles with an external electromagnetic field. The knowledge of heating ability (magnetic losses) in AC magnetic field frequency function allows for selecting the optimal excitation. A hybrid system for the characterization of superparamagnetic nanoparticles was designed and tested. The proposed setup consists of an excitation coil and two sensing probes: calorimetric and magnetic. The measurements of the imaginary part of the complex magnetic susceptibility of superparamagnetic nanoparticles are possible in the kilohertz range. The system was verified using a set of nanoparticles with different diameters. The measurement procedure was described and verified. The results confirmed that an elaborated sensor system and measuring procedures could properly characterize the magnetic characteristics of nanoparticles. The main advantage of this system is the ability to compare both characteristics and confirm the selection of optimal excitation parameters.

Cine dyscontractility index: A novel marker of mechanical dyssynchrony that predicts response to cardiac resynchronization therapy.

PURPOSE: To investigate whether magnetic resonance imaging (MRI) cine-derived dyssynchrony indices provide additional information compared to conventional tagged MRI (tMRI) acquisitions in heart failure patients undergoing cardiac resynchronization therapy (CRT). MATERIALS AND METHODS: Patients scheduled for CRT (n = 52) underwent preprocedure MRI including cine and tMRI acquisitions. Segmental strain curves were calculated for both cine and tMRI to produce a range of standard indices for direct comparison between modalities. We also proposed and evaluated a novel index of "dyscontractility," which detects the presence of focal areas with paradoxically positive circumferential strain. RESULTS: Across conventional strain indices, there was only moderate-to-poor (R = 0.3-0.6) correlation between modalities; eight cine-derived indices showed statistically significant (P < 0.05) relations to CRT outcome compared to just two tMRI-based counterparts. The novel dyscontractility index calculated on basal slice cine images (cine dyscontractility index, "CDI") was the single best predictor of clinical response to CRT (area under the curve AUC = 0.81, P < 0.001). While poorly correlated to its tMRI counterpart (R = 0.33), CDI performed significantly better in predicting response to CRT (P < 0.005), and was also numerically better than all other tMRI indices (AUC 0.53-0.76, all P for AUC comparisons <0.17). CONCLUSION: Cine-derived strain indices offer potentially new information compared to tMRI. Specifically, the novel CDI is most strongly linked to response to cardiac resynchronization therapy in a contemporary patient cohort. It utilizes readily available MRI data, is relatively straightforward to process, and compares favorably with any conventional tagging index. J. Magn. Reson. Imaging 2016;44:1483-1492.

Towards neural correlates of auditory stimulus processing: a simultaneous auditory evoked potentials and functional magnetic resonance study using an odd-ball paradigm.

BACKGROUND: The neural underpinnings of auditory information processing have often been investigated using the odd-ball paradigm, in which infrequent sounds (deviants) are presented within a regular train of frequent stimuli (standards). Traditionally, this paradigm has been applied using either high temporal resolution (EEG) or high spatial resolution (fMRI, PET). However, used separately, these techniques cannot provide information on both the location and time course of particular neural processes. The goal of this study was to investigate the neural correlates of auditory processes with a fine spatio-temporal resolution. A simultaneous auditory evoked potentials (AEP) and functional magnetic resonance imaging (fMRI) technique (AEP-fMRI), together with an odd-ball paradigm, were used. MATERIAL AND METHODS: Six healthy volunteers, aged 20-35 years, participated in an odd-ball simultaneous AEP-fMRI experiment. AEP in response to acoustic stimuli were used to model bioelectric intracerebral generators, and electrophysiological results were integrated with fMRI data. RESULTS: fMRI activation evoked by standard stimuli was found to occur mainly in the primary auditory cortex. Activity in these regions overlapped with intracerebral bioelectric sources (dipoles) of the N1 component. Dipoles of the N1/P2 complex in response to standard stimuli were also found in the auditory pathway between the thalamus and the auditory cortex. Deviant stimuli induced fMRI activity in the anterior cingulate gyrus, insula, and parietal lobes. CONCLUSIONS: The present study showed that neural processes evoked by standard stimuli occur predominantly in subcortical and cortical structures of the auditory pathway. Deviants activate areas non-specific for auditory information processing.

[Application of simultaneous auditory evoked potentials and functional magnetic resonance recordings for examination of central auditory system--preliminary results]. / Wykorzystanie jednoczesnych rejestracji sluchowych potencjalów korowych i funkcjonalnego rezonansu magnetycznego do badania procesów osrodkowej czesci ukladu sluchowego--wyniki wstepne.

INTRODUCTION: Processing of auditory information in central nervous system bases on the series of quickly occurring neural processes that cannot be separately monitored using only the fMRI registration. Simultaneous recording of the auditory evoked potentials, characterized by good temporal resolution, and the functional magnetic resonance imaging with excellent spatial resolution allows studying higher auditory functions with precision both in time and space. THE AIM OF THE STUDY: was to implement the simultaneous AEP-fMRI recordings method for the investigation of information processing at different levels of central auditory system. MATERIAL AND METHODS: Five healthy volunteers, aged 22-35 years, participated in the experiment. The study was performed using high-field (3T) MR scanner from Siemens and 64-channel electrophysiological system Neuroscan from Compumedics. Auditory evoked potentials generated by acoustic stimuli (standard and deviant tones) were registered using modified odd-ball procedure. Functional magnetic resonance recordings were performed using sparse acquisition paradigm. The results of electrophysiological registrations have been worked out by determining voltage distributions of AEP on skull and modeling their bioelectrical intracerebral generators (dipoles). FMRI activations were determined on the basis of deviant to standard and standard to deviant functional contrasts. Results obtained from electrophysiological studies have been integrated with functional outcomes. RESULTS: Morphology, amplitude, latency and voltage distribution of auditory evoked potentials (P1, N1, P2) to standard stimuli presented during simultaneous AEP-fMRI registrations were very similar to the responses obtained outside scanner room. Significant fMRI activations to standard stimuli were found mainly in the auditory cortex. Activations in these regions corresponded with N1 wave dipoles modeled based on auditory potentials generated by standard tones. Auditory evoked potentials to deviant stimuli were recorded only outside the MRI scanner. However, deviant stimuli induced significant fMRI activations. They were observed mainly in the anterior cingulate gyrus, insula and parietal lobes. These regions of the brain are related to attention and decision-making processes. CONCLUSIONS: The results showed that applied paradigm is suitable for investigation of acoustic processing on the level of auditory cortex. Technique of the simultaneous AEP-fMRI registrations seems to be promising for investigation of more complex nervous processes in central auditory system with good temporo-spatial resolution.

Functional imaging with MR T1 contrast: a feasibility study with blood-pool contrast agent.

The aim of this study was to prove the concept of using a long intravenous half-life blood-pool T1 contrast agent as a new functional imaging method. For each of ten healthy subjects, two dynamic magnetic resonance (MR) protocols were carried out: (1) a reference run with a typical T2* echo-planar imaging (EPI) sequence based on the blood oxygenation level-dependent (BOLD) effect and (2) a run with a T1-sensitive three-dimensional (3D) gradient-echo (GRE) sequence using cerebral blood volume (CBV) contrast after intravenous administration of a contrast agent containing a chelate of gadolinium diethylene-triamine-pentaacetate with a phosphono-oxymethyl substituent. All sequences were performed during the execution of a block-type finger-tapping paradigm. SPM5 software was used for statistical analysis. For both runs maximum activations (peak Z-score = 5.5, cluster size 3,449 voxels) were localized in the left postcentral gyrus. Visual inspection of respective signal amplitudes suggests the T1 contrast to be substantially smaller than EPI (0.5% vs 1%). A new functional imaging method with potentially smaller image artefacts due to the nature of CBV contrast and characteristics of the T1 sequence was proposed and verified.

Omega-3 fatty acid supplementation may prevent loss of gray matter thickness in the left parieto-occipital cortex in first episode schizophrenia: A secondary outcome analysis of the OFFER randomized controlled study.

The aim of the study was to assess changes in cortical thickness related to the use of n-3 polyunsaturated fatty acids (PUFA) as add-on therapy in patients with first episode schizophrenia. A double-blind randomized controlled study was conducted using a 26-week intervention composed of concentrated fish oil containing 2.2g/d of eicosapentaenoic (EPA) and docosahexaenoic acid (DHA) or placebo (olive oil). Participants underwent MRI scanning twice to assess changes in cortical thickness: at the beginning and at the end of intervention. Data of suitable quality was obtained from 29 participants. The T1-weighted images for each participant were analyzed using FreeSurfer methodology for longitudinal pipeline. Significant differences in cortical thickness loss were observed between the groups in the parieto-occipital regions of Brodmann areas 7 and 19 of the left hemisphere, dysfunctions in which may be involved in schizophrenia symptomatology. The results of the study support the previous observations carried out in older individuals and patients with mild cognitive impairment, indicating that n-3 PUFA may have neuroprotective properties, especially at early stages of neurodegenerative diseases, such as schizophrenia. If replicated, the results of the present study may encourage clinicians to consider n-3 PUFA as a promising addition to antipsychotics for long-term treatment of schizophrenia.

Improved recognition of sustained ventricular tachycardia from SAECG by support vector machine.

OBJECTIVE: We present the improved method of recognition of sustained ventricular tachycardia (SVT) based on new filtering technique (FIR), extended signal-averaged electrocardiography (SAECG) description by 9 parameters and the application of support vector machine (SVM) classifier. METHODS: The dataset consisted of 376 patients (100 patients with sustained ventricular tachycardia after myocardial infarction (MI) labelled as class SVT+, 176 patients without sustained ventricular tachycardia after MI and 77 healthy persons, 50% of data were left for validation. The analysis of SAECG was performed by 2 types of filtration: low pass four-pole IIR Butterworth filter and FIR filter with Kaiser window. We calculated 3 commonly used SAECG parameters: hfQRS (ms), RMS40 (microV), LAS<40 microV(ms) and 6 new parameters: LAS<25 microV(ms) - duration of the low amplitude <25 microV signals at the end of QRS complex; RMS QRS(microV) - root mean square voltage of the filtered QRS complex; pRMS(microV) - root mean square voltage of the first 40 ms of filtered QRS complex; pLAS(ms) - duration of the low amplitude <40 microV signals in front of QRS complex; RMS t1(microV) - root mean square voltage of the last 10 ms the filtered QRS complex; RMS t2(microV) - root mean square voltage of the last 20 ms the filtered QRS complex. For the recognition of SVT+ class patients we used the SVM with the Gaussian kernel. RESULTS: The results confirmed good generalization of obtained models. The recognition score (calculated as correct classification/total number of patients) of SVT+patients on data set containing 3 standard parameters (Butterworth filter) is 92.55%. The same score was obtained for data set containing 9 parameters (Butterworth filter). The best score (95.21%) was obtained for data set based on 9 parameters and FIR filter. CONCLUSION: Our approach improved risk stratification up to 95% based on SAECG due to the application of FIR filter, 6 new parameters and efficient statistical classifier, the support vector machine.

Mapping cortical thickness of the patients with unilateral end-stage open angle glaucoma on planar cerebral cortex maps.

PURPOSE: To estimate and compare cerebral cortex thickness in patients with unilateral end-stage glaucoma with that of age-matched individuals with unaffected vision. METHODS: 14 patients with unilateral end-stage primary open angle glaucoma (POAG) and 12 age-matched control individuals with no problems with vision were selected for the study based on detailed ophthalmic examination. For each participant 3D high-resolution structural brain T1-weighted magnetization prepared MR images were acquired on a 3.0 T scanner. Brain cortex thickness was estimated using the FreeSurfer image analysis environment. After warping of subjects' cortical surfaces to FreeSurfer common space, differences between POAG and control groups were inferred at the group analysis level with the General Linear Model. RESULTS: The analysis performed revealed local thinning in the visual cortex areas in the POAG group. Statistically significant differences form 600 mm2 clusters located in the Brodmann area BA19 in the left and right hemisphere. CONCLUSION: Unilateral vision loss due to end-stage neuropathy from POAG is associated with significant thinning of cortical areas employed in vision.

The neural correlates of specific executive dysfunctions in Parkinson's disease.

Several functional neuroimaging studies in patients with Parkinson's disease (PD) have suggested that changes in the fronto-parietal-striatal networks are associated with deficits in executive functioning. However, executive functions (EF) are multifaceted and include three dissociable components: working memory, response inhibition, and task-switching. This study investigated which component of executive functioning is most strongly associated with fronto-parietal-striatal efficiency in PD. PD patients (with and without executive dysfunction), and age-matched healthy subjects, completed a battery of cognitive tests previously shown to discriminate among the three EF components. Principal component analysis conducted on the selected cognitive test variables yielded three expected EF components. The component scores were used in regression analysis to assess the relationship between the EF efficiency and blood oxygenation level-dependent (BOLD) signal related to performing the n-back, an experimental task that draws upon multiple components of executive functioning: working memory, response inhibition, and task-switching. We found distinct neural correlates of specific executive dysfunctions in patients with PD. However, all of them seem to be associated with fronto-parietal-striatal efficiency.