Ernesto Roldan-Valadez

In vivo 3T spectroscopic quantification of liver fat content in nonalcoholic fatty liver disease: Correlation with biochemical method and morphometry

BACKGROUND & AIMS The clinical application of liver fat quantification has increased in recent years, paralleling the epidemic increase in nonalcoholic fatty liver disease. The aim of this study was to perform a diagnostic evaluation of spectroscopy by comparing its measurement of total lipid content with that from liver biopsies and morphometry in normal subjects and patients with nonalcoholic fatty liver disease. METHODS Patients with symptomatic cholelithiasis underwent 3T MR cholangiography with spectroscopic quantification of TLC. A laparoscopic cholecystectomy was performed on the day of admission, with liver samples taken during surgery. Microcolorimetric assessment quantified lipid content in liver samples and morphometric evaluation in stained slides. Statistical analysis included bivariate correlation, regression, and ROC analysis. RESULTS The study was conducted in 18 patients, 5 men (mean age, 35.2+/-11.03 years; range, 27-54 years) and 13 women (mean age, 46.77+/-11.77 years; range, 21-61 years). Using a cut-off value >5% for fat content, 8 patients presented with steatosis and 10 patients presented with normal liver fat content. A significant correlation was observed between fat spectroscopy and lipid content (r=0.876, p<0.001). A lower and non-significant correlation was observed between lipid content and morphometry (r=0.190, p>0.05). CONCLUSIONS The accuracy of spectroscopy in assessing fat concentration with a cut-off level of 7.48% was 100%. Spectroscopy showed a strong and significant correlation with lipid content. It may reliably replace liver biopsy for the assessment of liver fat content.

Diagnostic performance of regional DTI-derived tensor metrics in glioblastoma multiforme: simultaneous evaluation of p, q, L, Cl, Cp, Cs, RA, RD, AD, mean diffusivity and fractional anisotropy

AbstractObjectivesAlmost a dozen diffusion tensor-imaging (DTI) variables have been used to evaluate brain tumours with scarce information about their diagnostic ability. We aimed to perform a comprehensive evaluation of tensor metrics reported in the last decade.MethodsRetrospective case control study performed in 14 patients with glioblastoma multiforme (GBM) and 28 controls. Conventional brain MR sequences and image postprocessing of DTI allowed the calculation of: MD, FA, p, q, L, Cl, Cp, Cs, RA, RD and AD, classified into five regions: normal appearance white matter (NAWM), immediate and distant oedema, enhancing rim and cystic cavity. ANOVA and AUROC analyses were performed.ResultsANOVA depicted a significant difference among all metrics (p < 0.05). RA had the highest performance in the NAWM and cystic cavity; immediate and distant zones of oedema were best diagnosed by RD and Cp respectively; q was the best biomarker of the enhancing rim zone; p < 0.001 for all metrics.ConclusionsFA and MD, accepted biomarkers of brain injury, were surpassed by other metrics. RA, together with Cs, Cl and CP, might be the new leaders in the evaluation of brain tumours. DTI tensor metrics depict different clinical applicability at each tumour region.Key Points• DTI-derived tensor metrics can characterise the regional impairment of intraaxial brain tumours. • A performance evaluation of new diagnostic tests should follow the STARD initiative. • Each tumour region in GBM is detected by a different tensor metric. • FA and MD are not the best biomarkers of tumour infiltration. • The diagnostic performance of some tensor metrics allows them to be used interchangeably.

Neuroanatomy of episodic and semantic memory in humans: A brief review of neuroimaging studies

One of the most basic functions in every individual and species is memory. Memory is the process by which information is saved as knowledge and retained for further use as needed. Learning is a neurobiological phenomenon by which we acquire certain information from the outside world and is a precursor to memory. Memory consists of the capacity to encode, store, consolidate, and retrieve information. Recently, memory has been defined as a network of connections whose function is primarily to facilitate the long-lasting persistence of learned environmental cues. In this review, we present a brief description of the current classifications of memory networks with a focus on episodic memory and its anatomical substrate. We also present a brief review of the anatomical basis of memory systems and the most commonly used neuroimaging methods to assess memory, illustrated with magnetic resonance imaging images depicting the hippocampus, temporal lobe, and hippocampal formation, which are the main brain structures participating in memory networks.

Feasibility of in vivo quantitative magnetic resonance imaging with diffusion weighted imaging, T2-weighted relaxometry, and diffusion tensor imaging in a clinical 3 tesla magnetic resonance scanner for the acute traumatic spinal cord injury of rats: technical note.

Study Design. Prospective longitudinal study. Objective. To verify the feasibility of performing in vivo quantitative magnetic resonance imaging evaluation of moderate traumatic spinal cord injury (SCI) in rats using a clinical 3T scanner. Summary of Background Data. Animal models of human diseases are essential for translational medicine. Potential treatments of SCI are evaluated in 2 ways: anatomical and functional. Advanced magnetic resonance sequences allow a noninvasive assessment of the spinal cord depicting both. This study describes and validates a very reproducible, feasible, affordable, and reliable method, designed to be applied in commercial 3T equipment, using a novel stereotactic device for spinal cord, leading to a readily available assessment of the progression of damage generated after traumatic SCI in rats. Methods. Four Long-Evans female rats were injured with a New York University weight-drop device to produce the SCI by contusion at thoracic level 10. All animals were placed in a fixation system, using a commercial wrist antenna to obtain magnetic resonance imaging data of the relaxometry time, apparent diffusion coefficient, and fractional anisotropy. Three sets of data obtained before SCI and 1 and 4 weeks after injury were compared. Results. The data showed a progressive decline in fractional anisotropy measurements after SCI comparing baseline versus the 1-week period (P < 0.001) and baseline versus the 4-week period (P < 0.019), with a significant progressive increase in apparent diffusion coefficient values and T2 after SCI only in the baseline versus the 4-week period (P < 0.045 and P < 0.024, respectively). Conclusion. Our results helped us to validate a novel method to acquire highly reproducible and reliable quantitative biomarkers of traumatic SCI in vivo by using a 3T clinical MR scanner coupled with a novel stereotactic device for rats. Level of Evidence: N/A

3D volumetry comparison using 3T magnetic resonance imaging between normal and adenoma-containing pituitary glands.

BACKGROUND Computed-assisted three-dimensional data (3D) allows for an accurate evaluation of volumes compared with traditional measurements. AIMS An in vitro method comparison between geometric volume and 3D volumetry to obtain reference data for pituitary volumes in normal pituitary glands (PGs) and PGs containing adenomas. DESIGN Prospective, transverse, analytical study. MATERIALS AND METHODS Forty-eight subjects underwent brain magnetic resonance imaging (MRI) with 3D sequencing for computer-aided volumetry. PG phantom volumes by both methods were compared. Using the best volumetric method, volumes of normal PGs and PGs with adenoma were compared. Statistical analysis used the Bland-Altman method, t-statistics, effect size and linear regression analysis. RESULTS Method comparison between 3D volumetry and geometric volume revealed a lower bias and precision for 3D volumetry. A total of 27 patients exhibited normal PGs (mean age, 42.07 ± 16.17 years), although length, height, width, geometric volume and 3D volumetry were greater in women than in men. A total of 21 patients exhibited adenomas (mean age 39.62 ± 10.79 years), and length, height, width, geometric volume and 3D volumetry were greater in men than in women, with significant volumetric differences. Age did not influence pituitary volumes on linear regression analysis. CONCLUSIONS Results from the present study showed that 3D volumetry was more accurate than the geometric method. In addition, the upper normal limits of PGs overlapped with lower volume limits during early stage microadenomas.

Global diffusion tensor imaging derived metrics differentiate glioblastoma multiforme vs. normal brains by using discriminant analysis: introduction of a novel whole-brain approach

Abstract Background. Histological behavior of glioblastoma multiforme suggests it would benefit more from a global rather than regional evaluation. A global (whole-brain) calculation of diffusion tensor imaging (DTI) derived tensor metrics offers a valid method to detect the integrity of white matter structures without missing infiltrated brain areas not seen in conventional sequences. In this study we calculated a predictive model of brain infiltration in patients with glioblastoma using global tensor metrics. Methods. Retrospective, case and control study; 11 global DTI-derived tensor metrics were calculated in 27 patients with glioblastoma multiforme and 34 controls: mean diffusivity, fractional anisotropy, pure isotropic diffusion, pure anisotropic diffusion, the total magnitude of the diffusion tensor, linear tensor, planar tensor, spherical tensor, relative anisotropy, axial diffusivity and radial diffusivity. The multivariate discriminant analysis of these variables (including age) with a diagnostic test evaluation was performed. Results. The simultaneous analysis of 732 measures from 12 continuous variables in 61 subjects revealed one discriminant model that significantly differentiated normal brains and brains with glioblastoma: Wilks’ λ = 0.324, χ2 (3) = 38.907, p < .001. The overall predictive accuracy was 92.7%. Conclusions. We present a phase II study introducing a novel global approach using DTI-derived biomarkers of brain impairment. The final predictive model selected only three metrics: axial diffusivity, spherical tensor and linear tensor. These metrics might be clinically applied for diagnosis, follow-up, and the study of other neurological diseases.

Alternative bibliometrics from impact factor improved the esteem of a journal in a 2-year-ahead annual-citation calculation: multivariate analysis of gastroenterology and hepatology journals.

Introduction A deeper understanding of supplementary bibliometrics beyond the impact factor might provide researchers with a better understanding of the citation process. This study presents a multivariate analysis of gastroenterology and hepatology journals to evaluate the predictive ability of seven bibliometrics in the Web of Science to calculate total cites over a 2-year period. Methods Coincidentally, bibliometrics appearing during 2008, 2009, and 2010, with their corresponding cites in 2010, 2011, and 2012, were recorded from the Journal Citation Reports Science Edition. A linear mixed-effects design using random slopes and intercepts was performed on 51 out of 74 journals in the Gastroenterology and Hepatology category. Result There was a significant global effect size (R2=0.992; P<0.001), which yielded a total variance of 99.2%. The strongest predictors in the model were the Eigenfactor Score and Cited Half-life (P<0.001), followed by the Number of Articles (P=0.011) and the Immediacy Index (P=0.021). The impact factor was not a significant predictor. Conclusion The Eigenfactor Score and Cited Half-life predictors might be the new standards to assess the influence and importance of scientific journals; this approach may help researchers select journals in which to publish their work.

Main Effect and Interactions of Brain Regions and Gender in the Calculation of Volumetric Asymmetry Indices in Healthy Human Brains: Ancova Analyses of In Vivo 3T MRI Data

Introduction: Macroanatomical right‐left hemispheric differences in the brain are termed asymmetries, although there is no clear information on the global influence of gender and brain‐regions. The aim of this study was to evaluate the main effects and interactions of these variables on the measurement of volumetric asymmetry indices (VAIs). Materials and methods: Forty‐seven healthy young‐adult volunteers (23 males, 24 females) agreed to undergo brain magnetic resonance imaging in a 3T scanner. Image post processing using voxel‐based volumetry allowed the calculation of 54 VAIs from the frontal, temporal, parietal and occipital lobes, limbic system, basal ganglia, and cerebellum for each cerebral hemisphere. Multivariate ANCOVA analysis calculated the main effects and interactions on VAIs of gender and brain regions controlling the effect of age. Results: The only significant finding was the main effect of brain regions (F (6, 9373.605) 44.369, P < .001; partial η2 = .101, and power of 1.0), with no significant interaction between gender and brain regions (F (6, 50.517) .239, P = .964). Conclusion: Volumetric asymmetries are present across all brain regions, with larger values found in the limbic system and parietal lobe. The absence of a significant influence of gender and age in the evaluation of the numerous measurements generated by multivariate analyses in this study should not discourage researchers to report and interpret similar results, as this topic still deserves further assessment. Anat Rec, 296:1913–1922, 2013.

Alternative bibliometrics from the web of knowledge surpasses the impact factor in a 2-year ahead annual citation calculation: Linear mixed-design models' analysis of neuroscience journals

Context: The decision about which journal to choose for the publication of research deserves further investigation. Aims: In this study, we evaluate the predictive ability of seven bibliometrics in the Web of Knowledge to calculate total cites over a 7-year period in neuroscience journals. Settings and Design: Coincidental bibliometrics appearing during 2007, 2008, 2009, 2010, and 2011, along with their corresponding cites in 2009, 2010, 2011, 2012, and 2013, were recorded from the journal citation reports (JCR) Science Edition. This was a retrospective study. Materials and Methods: This was a bibliographic research using data from the Web of Knowledge in the neuroscience category. Statistical Analysis Used: A linear-mixed effects design using random slopes and intercepts was performed on 275 journals in the neuroscience category. Results: We found that Eigenfactor score, cited half-life, immediacy index, and number of articles are significant predictors of 2-year-ahead total cites (P ≤ 0.010 for all variables). The impact factor, 5-year impact factor, and article influence score were not significant predictors; the global effect size was significant (R2= 0.999; P < 0.001) with a total variance of 99.9%. Conclusions: An integrative model using a set of several metrics could represent a new standard to assess the influence and importance of scientific journals, and may simultaneously help researchers to rank journals in their decision-making during the manuscript submission phase.

Delayed injection of polypyrrole doped with iodine particle suspension after spinal cord injury in rats improves functional recovery and decreased tissue damage evaluated by 3.0 Tesla in vivo magnetic resonance imaging

BACKGROUND CONTEXT Traumatic spinal cord injury (SCI) causes irreversible damage with loss of motor, sensory, and autonomic functions. Currently, there is not an effective treatment to restore the lost neurologic functions. PURPOSE Injection of polypyrrole-iodine(PPy-I) particle suspension is proposed as a therapeutic strategy. STUDY DESIGN This is an in vivo animal study. METHODS This study evaluates the use of such particles in rats after SCI by examining spared nervous tissue and the Basso, Beattie, and Bresnahan (BBB) scale to evaluate the functional outcome. Diffusive magnetic resonance imaging (MRI) was employed to measure the apparent diffusion coefficient (ADC) and fractional anisotropy (FA) as non-invasive biomarkers of damage after SCI. RESULTS Fractional anisotropy decreased, whereas ADC increased in all groups after the lesion. There were significant differences in FA when compared with the SCI-PPy-I group versus the SCI group (p<.05). Significant positive correlations between BBB and FA (r2=0.449, p<.05) and between FA and preserved tissue (r2=0.395, p<.05) were observed, whereas significant negative associations between BBB and ADC (r2=0.367, p<.05) and between ADC and preserved tissue (r2=0.421, p<.05) were observed. CONCLUSIONS The results suggested that PPy-I is neuroprotective as it decreased the amount of damaged tissue while improving the motor function. Non-invasive MRI proved to be useful in the characterization of SCI and recovery.