Severe dyslipidemia and the associated oxidative stress could accelerate the age-related decline in cerebrovascular endothelial function and cerebral blood flow (CBF), leading to neuronal loss and ...impaired learning abilities. We hypothesized that a chronic treatment with the polyphenol catechin would prevent endothelial dysfunction, maintain CBF responses, and protect learning abilities in atherosclerotic (ATX) mice. We treated ATX (C57Bl/6-LDLR(-/-)hApoB(+/+); 3 mo old) mice with catechin (30 mg · kg(-1) · day(-1)) for 3 mo, and C57Bl/6 wild type (WT), 3 and 6 mo old mice were used as controls. ACh- and flow-mediated dilations (FMD) were recorded in pressurized cerebral arteries. Basal CBF and increases in CBF induced by whisker stimulation were measured by optical coherence tomography and Doppler, respectively. Learning capacities were evaluated with the Morris water maze test. Compared with 6-mo-old WT mice, cerebral arteries from 6-mo-old ATX mice displayed a higher myogenic tone, lower responses to ACh and FMD, and were insensitive to NOS inhibition (P < 0.05), suggesting endothelial dysfunction. Basal and increases in CBF were lower in 6-mo-old ATX than WT mice (P < 0.05). A decline in the learning capabilities was also observed in ATX mice (P < 0.05). Catechin 1) reduced cerebral superoxide staining (P < 0.05) in ATX mice, 2) restored endothelial function by reducing myogenic tone, improving ACh- and FMD and restoring the sensitivity to nitric oxide synthase inhibition (P < 0.05), 3) increased the changes in CBF during stimulation but not basal CBF, and 4) prevented the decline in learning abilities (P < 0.05). In conclusion, catechin treatment of ATX mice prevents cerebrovascular dysfunctions and the associated decline in learning capacities.
Ultrasound (US) is a popular medical imaging technique in the clinic due to its low cost, high portability, and real-time diagnostic value. A special type of ultrasound technique, transcranial ...Doppler (TCD) ultrasound can be used to measure blood flows in cerebral blood vessels through acoustic bone windows of the intact human skull. Although TCD ultrasound is commonly used to diagnose and monitor a range of neurovascular conditions, such as stroke, interpretation of the image content in the TCD scans and quick localization of the targeted blood vessels with it can be difficult due to inherent challenges of its unique image contrasts, relatively low image quality, and 2D nature of the technique in relation to the 3D brain anatomy that is invisible to the clinician. These drawbacks may hinder the efficiency and even accuracy of the TCS examinations, especially for novel users. To render the procedure more efficient and intuitive, we developed a prototype of augmented-reality system to guide the procedure by fusing a population-averaged probabilistic blood vessel atlas with camera footages of the patient. The system prototype was demonstrated with healthy subjects, and is expected to facility the clinical TCD examination, as well as to help in the educational context for new clinicians and clinical technicians.
To identify genetic markers associated with late treatment-related skeletal morbidity in survivors of childhood acute lymphoblastic leukemia (ALL).
To this end, we measured the association between ...reduction in bone mineral density or vertebral fractures prevalence and variants from 1039 genes derived through whole exome sequencing in 242 childhood ALL survivors. Top-ranking variants were confirmed through genotyping, and further explored with stratified analyses and multivariable models.
The minor allele of rs1944294 in
gene was associated with bone geometrical parameter, trabecular cross-sectional area (p = 0.001). The association was modulated by radiation therapy (p = 0.001) and post-treatment time (p = 0.0002).
The variant in
gene is a potential novel risk factor of bone morbidity in survivors of childhood ALL.
Purpose
As an inexpensive, noninvasive, and portable clinical imaging modality, ultrasound (US) has been widely employed in many interventional procedures for monitoring potential tissue deformation, ...surgical tool placement, and locating surgical targets. The application requires the spatial mapping between 2D US images and 3D coordinates of the patient. Although positions of the devices (i.e., ultrasound transducer) and the patient can be easily recorded by a motion tracking system, the spatial relationship between the US image and the tracker attached to the US transducer needs to be estimated through an
US calibration
procedure. Previously, various calibration techniques have been proposed, where a spatial transformation is computed to match the coordinates of corresponding features in a physical phantom and those seen in the US scans. However, most of these methods are difficult to use for novel users.
Methods
We proposed an ultrasound calibration method by constructing a phantom from simple Lego bricks and applying an automated multi-slice 2D–3D registration scheme without volumetric reconstruction. The method was validated for its calibration accuracy and reproducibility.
Results
Our method yields a calibration accuracy of
1.23
±
0.26
mm and a calibration reproducibility of 1.29 mm.
Conclusion
We have proposed a robust, inexpensive, and easy-to-use ultrasound calibration method.
In order to investigate the role of clay minerals in organic matter preservation, the fixation of pure organic compounds on two synthetic low charge and high charge saponites was investigated in ...laboratory experiments simulating marine water conditions. The clays were exposed to four carboxylic acids: pentadecanoic, docosanoic, 5β-cholanic acid and ursolic, dissolved in treated natural sea water. Characterization of the resulting organo-clay association indicates that, under marine water column conditions, the organic fixation is only a sorption process, no intercalation being observed. The surface coverage, similar for the two clays (ca. 0.04
mg organic carbon m
−2), demonstrates that the sorption is controlled by the surface properties of clays rather than their cation exchange capacity. The weaker sorption of docosanoic acid underlines the major role of the molecular properties, but the lack of selectivity among the three others does not corroborate the influence of molecular size on the sorption process. The general failure of a chemolysis treatment performed on the organo-clay associations demonstrates the high stability of these complexes. Results suggest that the bonding mechanisms are dominated by ligand exchange and not by hydrophobic effects, cation bridges or cation exchange. The minor extractable organic fraction consists of acid molecules connected to clay surfaces by van der Waals interactions.
The high stability of the bonds formed in this environment, close to that observed in previous studies of marine sediments, could explain in part organic matter preservation during transfer across marine water columns, especially metabolisable material.
In a mixed reality visualization, physical and virtual environments are merged to produce new visualizations where both real and virtual objects are displayed together. In image guided surgery (IGS), ...surgical tools and data sets are fused into a mixed reality visualization providing the surgeon with a view beyond the visible anatomical surface of the patient, thereby reducing patient trauma, and potentially improving clinical outcomes. To date few mixed reality systems are used on a regular basis for surgery. One possible reason for this is that little research on which visualization methods and techniques are best and how they should be incorporated into the surgical workflow has been done. There is a strong need for evaluation of different visualization methods that may show the clinical usefulness of such systems. In this work we present a test and development environment for augmented reality visualization techniques and provide an example of the system use for image guided neurovascular surgery. The system was developed using open source software and off-the-shelf hardware.
Background: Research in healthy young adults shows that characteristic patterns of brain activity define individual “brain-fingerprints” that are unique to each person. However, variability in these ...brain-fingerprints increases in individuals with neurological conditions, challenging the clinical relevance and potential impact of the approach. Our study shows that brain-fingerprints derived from neurophysiological brain activity are associated with pathophysiological and clinical traits of individual patients with Parkinson’s disease (PD). Methods: We created brain-fingerprints from task-free brain activity recorded through magnetoencephalography in 79 PD patients and compared them with those from two independent samples of age-matched healthy controls (N = 424 total). We decomposed brain activity into arrhythmic and rhythmic components, defining distinct brain-fingerprints for each type from recording durations of up to 4 min and as short as 30 s. Findings: The arrhythmic spectral components of cortical activity in patients with Parkinson’s disease are more variable over short periods, challenging the definition of a reliable brain-fingerprint. However, by isolating the rhythmic components of cortical activity, we derived brain-fingerprints that distinguished between patients and healthy controls with about 90% accuracy. The most prominent cortical features of the resulting Parkinson’s brain-fingerprint are mapped to polyrhythmic activity in unimodal sensorimotor regions. Leveraging these features, we also demonstrate that Parkinson’s symptom laterality can be decoded directly from cortical neurophysiological activity. Furthermore, our study reveals that the cortical topography of the Parkinson’s brain-fingerprint aligns with that of neurotransmitter systems affected by the disease’s pathophysiology. Interpretation: The increased moment-to-moment variability of arrhythmic brain-fingerprints challenges patient differentiation and explains previously published results. We outline patient-specific rhythmic brain signaling features that provide insights into both the neurophysiological signature and symptom laterality of Parkinson’s disease. Thus, the proposed definition of a rhythmic brain-fingerprint of Parkinson’s disease may contribute to novel, refined approaches to patient stratification. Symmetrically, we discuss how rhythmic brain-fingerprints may contribute to the improved identification and testing of therapeutic neurostimulation targets. Funding: Data collection and sharing for this project was provided by the Quebec Parkinson Network (QPN), the Pre-symptomatic Evaluation of Novel or Experimental Treatments for Alzheimer’s Disease (PREVENT-AD; release 6.0) program, the Cambridge Centre for Aging Neuroscience (Cam-CAN), and the Open MEG Archives (OMEGA). The QPN is funded by a grant from Fonds de Recherche du Québec - Santé (FRQS). PREVENT-AD was launched in 2011 as a $13.5 million, 7-year public-private partnership using funds provided by McGill University, the FRQS, an unrestricted research grant from Pfizer Canada, the Levesque Foundation, the Douglas Hospital Research Centre and Foundation, the Government of Canada, and the Canada Fund for Innovation. The Brainstorm project is supported by funding to SB from the NIH (R01-EB026299-05). Further funding to SB for this study included a Discovery grant from the Natural Sciences and Engineering Research Council of Canada of Canada (436355-13), and the CIHR Canada research Chair in Neural Dynamics of Brain Systems (CRC-2017-00311).
End-of-life policies are hotly debated in many countries, with international evidence frequently used to support or oppose legal reforms. Existing reviews are limited by their focus on specific ...practices or selected jurisdictions. The objective is to review international time trends in end-of-life practices.
We conducted a systematic review of empirical studies on medical end-of-life practices, including treatment withdrawal, the use of drugs for symptom management, and the intentional use of lethal drugs. A search strategy was conducted in MEDLINE, EMBASE, Web of Science, Sociological Abstracts, PAIS International, Worldwide Political Science Abstracts, International Bibliography of the Social Sciences and CINAHL. We included studies that described physicians' actual practices and estimated annual frequency at the jurisdictional level. End-of-life practice frequencies were analyzed for variations over time, using logit regression.
Among 8183 references, 39 jurisdiction-wide surveys conducted between 1990 and 2010 were identified. Of those, 22 surveys used sufficiently similar research methods to allow further statistical analysis. Significant differences were found across surveys in the frequency of treatment withdrawal, use of opiates or sedatives and the intentional use of lethal drugs (X
> 1000, p < 0.001 for all). Regression analyses showed increased use of opiates and sedatives over time (p < 0.001), which could reflect more intense symptom management at the end of life, or increase in these drugs to intentionally cause patients' death.
The use of opiates and sedatives appears to have significantly increased over time between 1990 and 2010. Better distinction between practices with different legal status is required to properly interpret the policy significance of these changes. Research on the effects of public policies should take a comprehensive look at trends in end-of-life practice patterns and their associations with policy changes.
Celotno besedilo
Dostopno za:
CEKLJ, DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
In neurovascular surgery, and in particular surgery for arteriovenous malformations (AVMs), the surgeon maps pre-operative images to the patient on the operating table to aid in vessel localization ...and resection. This type of spatial mapping is not trivial, is time consuming, and may be prone to error. Using augmented reality (AR) we can register the microscope/camera image of the patient to pre-operative data in order to help the surgeon better understand the topology and locations of vessels that lie below the visible surface of the cortex. In this work we describe a prototype system, developed using open source software and built with off-the-shelf hardware, for AR visualization for AVM neurosurgery. Furthermore, we consider two visualization techniques, colour-coding and chromadepth, to enhance the depth perception of vessels.
Purpose
The aim of this report is to present IBIS (Interactive Brain Imaging System) NeuroNav, a new prototype neuronavigation system that has been developed in our research laboratory over the past ...decade that uses tracked intraoperative ultrasound to address surgical navigation issues related to brain shift. The unique feature of the system is its ability, when needed, to improve the initial patient-to-preoperative image alignment based on the intraoperative ultrasound data. Parts of IBIS Neuronav source code are now publicly available on-line.
Methods
Four aspects of the system are characterized in this paper: the ultrasound probe calibration, the temporal calibration, the patient-to-image registration and the MRI-ultrasound registration. In order to characterize its real clinical precision and accuracy, the system was tested in a series of adult brain tumor cases.
Results
Three metrics were computed to evaluate the precision and accuracy of the ultrasound calibration. 1) Reproducibility: 1.77 mm and 1.65 mm for the bottom corners of the ultrasound image, 2) point reconstruction precision 0.62–0.90 mm: and 3) point reconstruction accuracy: 0.49–0.74 mm. The temporal calibration error was estimated to be 0.82 ms. The mean fiducial registration error (FRE) of the homologous-point-based patient-to-MRI registration for our clinical data is 4.9 ± 1.1 mm. After the skin landmark-based registration, the mean misalignment between the ultrasound and MR images in the tumor region is 6.1 ± 3.4 mm.
Conclusions
The components and functionality of a new prototype system are described and its precision and accuracy evaluated. It was found to have an accuracy similar to other comparable systems in the literature.
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