Modular architecture of metabolic brain network and its effects on the spread of perturbation impact

Publication date: Available online 5 November 2018

Source: NeuroImage

Author(s): Tianhao Zhang, Qi Huang, Chunxiang Jiao, Hua Liu, Binbin Nie, Shengxiang Liang, Panlong Li, Xi Sun, Ting Feng, Lin Xu, Baoci Shan

Abstract

Metabolic brain network, which is based on functional correlation patterns of ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET) images, has been widely applied in both basic and clinical neuroscience. Exploring the properties of the metabolic brain network can provide valuable insight to the physiologic and pathologic processes of the brain. Based on the network theory, modular architecture has the ability to limit the spread of local perturbation impact and therefore modular networks are more robust against external damage. However, whether the metabolic brain network has modular architecture remains unknown.

Methods

77 rats performed ¹⁸F-FDG PET brain imaging. The metabolic brain network was then constructed by measuring interregional metabolic correlation in inter-subject manner. Afterwards, modular architecture of the network was detected by a greedy algorithm. Further, we perturbed the metabolic brain network by inducing focal photothrombotic ischemia in the bilateral motor cortex and then measured the glucose metabolic change of each brain region using FDG-PET.

Results

A significant modular architecture was found in the metabolic brain network. The network could be divided into four modules which corresponding approximately to executive, learning/memory, visual/auditory and sensorimotor processing functional domains. After inducing the focal ischemia on the bilateral motor cortex, most of the significantly changed brain regions (13 of 17) belong to the sensorimotor module.

Conclusion

Our results revealed an inherent modular architecture in the metabolic brain network and gave an experimental evidence that the modularity of the metabolism brain network could limit the spread of local perturbation impact.

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Coarse-to-fine information integration in human vision

Publication date: Available online 4 November 2018

Source: NeuroImage

Author(s): Kirsten Petras, Sanne ten Oever, Christianne Jacobs, Valerie Goffaux

Abstract

Coarse-to-fine theories of vision propose that the coarse information carried by the low spatial frequencies (LSF) of visual input guides the integration of finer, high spatial frequency (HSF) detail. Whether and how LSF modulates HSF processing in naturalistic broad-band stimuli is still unclear. Here we used multivariate decoding of EEG signals to separate the respective contribution of LSF and HSF to the neural response evoked by broad-band images. Participants viewed images of human faces, monkey faces and phase-scrambled versions that were either broad-band or filtered to contain LSF or HSF. We trained classifiers on EEG scalp-patterns evoked by filtered scrambled stimuli and evaluated the derived models on broad-band scrambled and intact trials. We found reduced HSF contribution when LSF was informative towards image content, indicating that coarse information does guide the processing of fine detail, in line with coarse-to-fine theories. We discuss the potential cortical mechanisms underlying such coarse-to-fine feedback.

Graphical abstract

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Effect of temperature on the cyclic fatigue resistance of thermally treated reciprocating instruments

Abstract

Objectives

The aim of this study was to evaluate the impact of body temperature on the cyclic fatigue resistance of different NiTi alloys used for the manufacturing of Reciproc Blue R25 (RB 25.08; VDW, Munich, Germany), X1 Blue File 25 (X1 25.06; MK Life Medical and Dental Products, Porto Alegre, Brazil) and WaveOne Gold Primary (WOG 25.07; Dentsply Maillefer, Ballaigues, Switzerland).

Materials and methods

Sixty instruments of the RB 25.08, X1 25.06 and WOG 25.07 systems were used (n = 20). Cyclic fatigue tests were performed at room temperature (20° ± 1 °C) and at body temperature (37° ± 1 °C). The instruments were reciprocated until fracture occurred in an artificial stainless steel canal with a 60° angle and a 5-mm radius of curvature. The time to fracture (TTF) was recorded. Also, the number of cycles to fracture (NCF) was calculated. Data were analysed using one-way ANOVA and Tukey's tests for inter-group comparison at both temperatures and for the reduction of cyclic fatigue at body temperature. For intra-group comparison at the different temperatures, the unpaired t test was used.

Results

The cyclic fatigue test at 20 °C showed that RB 25.08 and X1 25.06 presented significantly higher TTF and NCF than WOG 25.07 (P < 0.05). At 37 °C, all groups presented significant reduction of TTF and NCF (P < 0.05). RB 25.08 presented significant higher TTF than WOG 25.07 (P < 0.05). Regarding the NCF, there was no significant difference among the groups (P > 0.05). The WOG 25.07 presented the lowest percentage reduction of cyclic fatigue (P < 0.05).

Conclusion

The body temperature treatment caused a marked reduction of the cyclic fatigue resistance for all reciprocating instruments tested. The RB 25.08 and X1 25.06 systems presented similar results at both temperatures tested. However, WOG 25.07 presented the lowest percentage reduction in fatigue resistance at body temperature.

Clinical relevance

The cyclic fatigue resistance of NiTi reciprocating instruments has been evaluated at room temperature. However, the fatigue resistance significantly decreases upon exposure to body temperature, which could affect the mechanical behaviour of the NiTi instruments during root canal preparation.

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Impact of a modified motion on the fatigue life of NiTi reciprocating instruments: a Weibull analysis

Abstract

Objectives

To evaluate the impact of a modified motion on the fatigue life of four brands of nickel–titanium (NiTi) reciprocating instruments.

Materials and methods

Cyclic fatigue (CF) resistance of 160 instruments was evaluated in an artificial stainless-steel canal (90° angle, 5-mm radius of curvature). WaveOne and WaveOne Gold (Denstply Maillefer, Baillagues, Switzerland) and Reciproc and Reciproc Blue (VDW, Munich, Germany) were tested with two different motions: (1) X-Smart Plus (Denstply Maillefer) endodontic motor and (2) a 4:1 contra-angle with an experimental motion (EVO) with different rotation angles and based on a sinusoidal acceleration. Motions with X-Smart Plus and EVO were recorded and analyzed at a reduced speed with VLC Media Player software for a more accurate analysis. Mean half-life, beta, and eta Weibull parameters were determined and compared.

Results

Reciproc Blue resulted the most resistant instruments either with EVO or X-Smart. WaveOne Gold lasted significantly longer than WaveOne with EVO (probability of 91%) while no significant differences were found with X-Smart. Considering NCF, Reciproc, WaveOne Gold, and Reciproc Blue lasted significantly longer with EVO (probabilities of 66%, 80%, and 89% respectively). WaveOne Gold showed the highest beta parameter.

Conclusions

The experimental motion was found to have a positive impact on fatigue lifetime of reciprocating instruments.

Clinical relevance

Current findings provide insight for future improvements in the clinical use of reciprocating files. Experimental motions may be considered when searching for additional strategies in order to increase the safer use of NiTi files during endodontic procedures.

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The Impact of Different Magnetic Resonance Imaging Equipment and Scanning Parameters on Signal Intensity Ratio Measurements in Phantoms and Healthy Volunteers: Implications for Interpreting Gadolinium Signal Changes Within the Brain

Objectives The aim of this study was to examine the variation in signal intensity ratio (SIR) values in Eurospin gel phantoms and healthy volunteer (HV) brain images in response to different magnetic resonance imaging hardware and software settings. Materials and Methods Gel phantoms with T1 relaxation times similar to the dentate nucleus (DN), pons (P), globus palladus (GP), and thalamus (Th) were scanned using a T1-weighted 2-dimensional spin-echo sequence on 2 magnetic resonance imaging scanners (3 T and 1.5 T). Imaging was performed by sequentially altering selected magnetic resonance (MR) parameters relative to a default pulse sequence, and the protocol was implemented repeatedly over 3 months. The experiment was also repeated on a cohort of 15 young HVs. Calculations of DN/P and GP/Th SIR values were derived for the images of the gels (GelDN/P and GelGP/Th) and the HVs (HVDN/P and HVGP/Th). Results For the default sequence, the mean SIR values of GelDN/P and GelGP/Th varied by ±2.20% and ±0.75%, respectively, when measured over multiple imaging sessions (3 T). Within a single imaging session, these variations were smaller (±0.17% for GelDN/P and ±0.15% for GelGP/Th). At 1.5 T, the equivalent SIR variations for GelDN/P were ± 1.41% (multiple sessions) and ±0.41% (single session), and that for GelGP/Th were ±0.47% (multiple sessions) and ±0.33% (single session). Sequential changes to the MR sequence parameters resulted in gel SIR variations as follows: 14.07% ± 2.43% (with/without normalization filters), −7.80% ± 0.28% (different echo times, TE), and −5.06% ± 0.59% (selective activation of RF coil elements). The largest variations were noted when the gels were positioned below the scanner isocenter, where SIR measurements were different by 22%. For the HVs, the SIR values were found to be consistently within 0.64% (single session) for the default sequence. Sequential changes to the MR sequence parameters resulted in SIR variations of −24.47% ± 2.47% (with/without normalization filters), −15.32% ± 7.71% (different echo times, TE), and −2.90% ± 0.78% (selective activation of RF coil elements). Conclusions This study has demonstrated that SIR percentage changes from baseline of a similar magnitude to brain gadolinium contrast agent signal hyperintensities can be replicated in phantom models and HVs by altering common MR acquisition parameters and hardware. Received for publication August 8, 2018; and accepted for publication, after revision, September 12, 2018. Conflicts of interest and sources of funding: Financial support for the study was provided via the Renal Dialysis for Venous Access (ReDVA) project (a European Union's Seventh Framework Program grant agreement no. 324487). The authors would like to state that we have received funding from Guerbet. L.Y. is currently receiving PhD sponsorship, while S.M. and G.H. have previously received research and educational support grants. Guerbet, however, were not involved in the study or publication processes. Correspondence to: J. Graeme Houston, MD, FRCR, Division of Molecular and Clinical Medicine, School of Medicine, University of Dundee, Ninewells Hospital and Medical School, James Arrnott Drive Dundee DD1 9SY, United Kingdom. E-mail: j.g.houston@dundee.ac.uk. Copyright © 2018 Wolters Kluwer Health, Inc. All rights reserved.

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Does Age Interfere With Gadolinium Toxicity and Presence in Brain and Bone Tissues?: A Comparative Gadoterate Versus Gadodiamide Study in Juvenile and Adult Rats

Objectives The main objective of the study was to assess the effect of age on target tissue total gadolinium (Gd) retention after repeated administration of gadodiamide (linear) or gadoterate (macrocyclic) Gd-based contrast agent (GBCA) in rats. The secondary objective was to assess the potential developmental and long-term consequences of GBCA administration during neonatal and juvenile periods. Materials and Methods A total of 20 equivalent human clinical doses (cumulated dose, 12 mmol Gd/kg) of either gadoterate or gadodiamide were administered concurrently by the intravenous route to healthy adult and juvenile rats. Saline was administered to juvenile rats forming the control group. In juvenile rats, the doses were administered from postnatal day 12, that is, once the blood-brain barrier is functional as in humans after birth. The tests were conducted on 5 juvenile rats per sex and per group and on 3 adult animals per sex and per group. T1-weighted magnetic resonance imaging of the cerebellum was performed at 4.7 T during both the treatment and treatment-free periods. Behavioral tests were performed in juvenile rats. Rats were euthanatized at 11 to 12 weeks (ie, approximately 3 months) after the last administration. Total Gd concentrations were measured in plasma, skin, bone, and brain by inductively coupled plasma mass spectrometry. Cerebellum samples from the juvenile rats were characterized by histopathological examination (including immunohistochemistry for glial fibrillary acidic protein or GFAP, and CD68). Lipofuscin pigments were also studied by fluorescence microscopy. All tests were performed blindly on randomized animals. Results Transient skin lesions were observed in juvenile rats (5/5 females and 2/4 males) and not in adult rats having received gadodiamide. Persisting (up to completion of the study) T1 hyperintensity in the deep cerebellar nuclei (DCNs) was observed only in gadodiamide-treated rats. Quantitatively, a slightly higher progressive increase in the DCN/brain stem ratio was observed in adult rats compared with juvenile rats, whereas no difference was noted visually. In all tissues, total Gd concentrations were higher (10- to 30-fold higher) in the gadodiamide-treated groups than in the gadoterate groups. No age-related differences were observed except in bone marrow where total Gd concentrations in gadodiamide-treated juvenile rats were higher than those measured in adults and similar to those measured in cortical bone tissue. No significant treatment-related effects were observed in histopathological findings or in development, behavior, and biochemistry parameters. However, in the elevated plus maze test, a trend toward an anxiogenic effect was observed in the gadodiamide group compared with other groups (nonsignificant). Moreover, in the balance beam test, a high number of trials were excluded in the gadodiamide group because rats (mainly males) did not completely cross the beam, which may also reflect an anxiogenic effect. Conclusions No T1 hyperintensity was observed in the DCN after administration of the macrocyclic GBCA gadoterate regardless of age as opposed to administration of the linear GBCA gadodiamide. Repeated administration of gadodiamide in neonatal and juvenile rats resulted in similar total Gd retention in the skin, brain, and bone to that in adult rats with sex having no effect, whereas Gd distribution in bone marrow was influenced by age. Further studies are required to assess the form of the retained Gd and to investigate the potential risks associated with Gd retention in bone marrow in juvenile animals treated with gadodiamide. Regardless of age, total Gd concentration in the brain and bone was 10- to 30-fold higher after administration of gadodiamide compared with gadoterate. This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives License 4.0 (CCBY-NC-ND), where it is permissible to download and share the work provided it is properly cited. The work cannot be changed in any way or used commercially without permission from the journal. Received for publication July 13, 2018; and accepted for publication, August 10, 2018, after revision, August 10, 2018. Conflicts of interest and sources of funding: All authors (except F.B.) were Guebert employees at the time of the study. This study was funded by Guebert through the Atlantic Bone Screen funding within the common research project. Supplemental digital contents are available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal's Web site (https://ift.tt/2kq7jVD). Correspondence to: Nathalie Fretellier, PhD, Research and Innovation Department, Guerbet Group, BP57400, 95943 Roissy CDG Cedex, France. E-mail: nathalie.fretellier@guerbet.com. Copyright © 2018 Wolters Kluwer Health, Inc. All rights reserved.

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T2 Mapping in Prostate Cancer

Objectives The aim of the study was to determine the quantitative T2 values in prostate tissue and evaluate them for detection and grading of prostate cancer. Materials and Methods After approval from the local ethics committee, morphological T2-weighted (T2w) images, apparent diffusion coefficient (ADC) maps from diffusion-weighted images, quantitative T2 maps, and calculated T2w images from 75 men (median age, 66.3 years; median PSA, 8.2 ng/mL) were acquired at 3 T magnetic resonance imaging (MRI). Data were retrospectively evaluated for their distinction between prostate pathologies.  Eight hundred fifty-seven areas of normal gland (n = 378), prostate cancer (54x Gleason score 6, 98x Gleason score 7, 25x Gleason score 8), benign prostatic hyperplasia (BPH) nodes (n = 150), prostatitis (n = 119), and precancerous lesions (n = 33) were determined on calculated and morphological T2w images. Histological criterion standards were whole gland sections (16 patients), MRI-guided in-bore biopsies (32 patients), MRI/transrectal ultrasound-fusion biopsies (15 patients), and systematic 12-core transrectal ultrasound-guided biopsies (12 patients). Significance was assumed to be P

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