Proton magnetic resonance spectroscopy of brain in obstructive sleep apnea in Egyptian subjects

AbstractObjectiveThe overall objective of this work is to study the cerebral metabolic changes in patients with OSA and to determine the usefulness of MRS as an objective method for evaluation of CNS impairment in these patients.Materials and methodsThis study included two groups; group1 fifteen (15) patients diagnosed with obstructive sleep apnea hypopnea syndrome, and group 2 ten (10) healthy volunteers of comparable age.Magnetic resonance spectra were obtained from frontal periventricular white matter.For all subjects, height, body weight, and BMI were assessed. Waist and hip circumference were measured and waist/hip ratio (W/H ratio) was calculated.Overnight polysomnography (PSG) to identify sleep apnea was done. Daytime sleepiness was evaluated by the Epworth Sleepiness Scale. Symptoms of anxiety and depression were measured with the Hospital Anxiety and Depression Scale (HADS).ResultsN-acetylaspartate-to-creatine (NAA/Cr) and choline-to-creatine (Cho/Cr) ratios were significantly lower in the frontal white matter of obstructive sleep apnea patients when compared to controls. Absolute concentrations of N-acetylaspartate (NAA) and choline (Cho) were also significantly reduced in the frontal white matter of patients with sleep apnea. Statistically significant negative correlations existed between AHI and metabolites concentrations and ratios in patients with OSAHS. Significant positive correlations existed in patients with OSAHS between Hospital and depression scale for depression (HAD-D) and AHI (r=0.764, p=0.001), ODI (r=0.571, p=0.026), and ESS (r=0.644, p=0.010), respectively. Significant positive correlations existed in patients with OSAHS between Hospital and depression scale for anxiety (HAD-A) and AHI (r=0.753, p=0.001), and ESS (r=0.537, p=0.039), respectively. Multivariate Linear regression model of factors predictive showed AHI as the main predictor factor for choline to creatine ratio in patients with OSAHS with t=5.180, at p<0.001.ConclusionOSA patients show abnormal brain metabolites related to neuronal damage due to intermittent chronic hypoxemia. Anxious and depressive symptoms are highly prevalent in patients with severe untreated OSAS. The severity of depressive and anxious symptoms may be related to excessive daytime sleepiness and to nocturnal hypoxemia both of which are strongly correlated to brain metabolites. AHI seems to be the main predictor factor for choline to creatine ratio in patients with OSAHS

NREL Pyrheliometer Comparison: September 16 to 27, 2013 (NPC-2013)

Accurate measurements of direct normal (beam) solar irradiance from pyrheliometers are important for the development and deployment of solar energy conversion systems, improving our understanding of the Earth's energy budget for climate change studies, and for other science and technology applications involving solar flux. Providing these measurements places many demands on the quality system used by the operator of commercially available radiometers. Maintaining accurate radiometer calibrations traceable to an international standard is the first step in producing research-quality solar irradiance measurements. As with all measurement systems, absolute cavity radiometers and other types of pyrheliometers are subject to performance changes over time. NREL has developed and maintained a group of absolute cavity radiometers with direct calibration traceability to the World Radiometric Reference (WRR). These reference instruments are used by NREL to calibrate pyrheliometers and pyranometers using the ISO 17025 accredited Broadband Outdoor Radiometer Calibration (BORCAL) process (Reda et al. 2008). NPCs are held annually at the Solar Radiation Research Laboratory (SRRL) in Golden, Colorado. Open to all pyrheliometer owners/operators, e.g. NREL, NASA, NIST, NOAA, USA industry and academia, USA-DOE and other national laboratories, and national and international organizations. Each NPC provides an opportunity to determine the unique World Radiometric Reference (WRR) transfer factor (WRR-TF) for each participating pyrheliometer. By adjusting all subsequent pyrheliometer measurements by the appropriate WRR-TF, the solar irradiance data are traceable to the International System of Units through WRR

Peculiar Labial Duct in the Camel Philtrum: Structure and Feasible Functions

The philtrum is well known as a median groove within the upper lip of mammalian species. However, a peculiar serpentine duct was identified within the mucosal surface of the camel philtrum. To the best of the author’s knowledge, the available literature did not mention any information regarding the presence of a complete duct in such location. For these, this study was aimed to reveal the gross and microscopic structure as well as to discuss the possible functions of this labial duct in dromedary. Twenty snouts from 20 camel heads were used. The labial duct had unique morphological and microscopic structure. It was a median highly tortuous duct with proximal and distal segments connected to each other through a capillary portion. The latter revealed only at the microscopic level. The duct had two entrances, the proximal and distal papillae. Importantly, the microscopic studies revealed that it also had an olfactory portion. In conclusion, the labial duct in camels is a peculiar anatomical structure, which may function as an organ of alarm

Improving the Accuracy of Using Pyranometers to Measure the Clear Sky Global Solar Irradiance

Pyranometer users have customarily applied one responsivity value when calculating the global solar irradiance. Usually, the responsivity value is reported by either the manufacturer or a calibration facility. Many pyranometer calibrations, made both at NREL and elsewhere, have shown that the responsivity of a pyranometer changes with the change in solar zenith and azimuth angles. Depending on how well the pyranometer sensor is radiometrically leveled, these changes can exceed +/-5% of the reported responsivity, which means that errors in the calculated global solar irradiance can exceed +/-5% from the nominal values. This paper describes a method to decrease the errors resulting from the change of the solar zenith angle under clear sky conditions. Two responsivity functions, morning and afternoon, were used instead of one responsivity value. The two functions have been chosen because of asymmetry of the morning and afternoon cosine responses demonstrated by some pyranometers

Approximate logic synthesis: a survey

Approximate computing is an emerging paradigm that, by relaxing the requirement for full accuracy, offers benefits in terms of design area and power consumption. This paradigm is particularly attractive in applications where the underlying computation has inherent resilience to small errors. Such applications are abundant in many domains, including machine learning, computer vision, and signal processing. In circuit design, a major challenge is the capability to synthesize the approximate circuits automatically without manually relying on the expertise of designers. In this work, we review methods devised to synthesize approximate circuits, given their exact functionality and an approximability threshold. We summarize strategies for evaluating the error that circuit simplification can induce on the output, which guides synthesis techniques in choosing the circuit transformations that lead to the largest benefit for a given amount of induced error. We then review circuit simplification methods that operate at the gate or Boolean level, including those that leverage classical Boolean synthesis techniques to realize the approximations. We also summarize strategies that take high-level descriptions, such as C or behavioral Verilog, and synthesize approximate circuits from these descriptions

Comparison between the calculated and measured dose distributions for four beams of 6 MeV linac in a human-equivalent phantom

Radiation dose distributions in various parts of the body are of importance in radiotherapy. Also, the percent depth dose at different body depths is an important parameter in radiation therapy applications. Monte Carlo simulation techniques are the most accurate methods for such purposes. Monte Carlo computer calculations of photon spectra and the dose ratios at surfaces and in some internal organs of a human equivalent phantom were performed. In the present paper, dose distributions in different organs during bladder radiotherapy by 6 MeV X-rays were measured using thermoluminescence dosimetry placed at different points in the human-phantom. The phantom was irradiated in exactly the same manner as in actual bladder radiotherapy. Four treatment fields were considered to maximize the dose at the center of the target and minimize it at non-target healthy organs. All experimental setup information was fed to the MCNP-4b code to calculate dose distributions at selected points inside the proposed phantom. Percent depth dose distribution was performed. Also, the absorbed dose as ratios relative to the original beam in the surrounding organs was calculated by MCNP-4b and measured by thermoluminescence dosimetry. Both measured and calculated data were compared. Results indicate good agreement between calculated and measured data inside the phantom. Comparison between MCNP-4b calculations and measurements of depth dose distribution indicated good agreement between both

Introducing an Absolute Cavity Pyrgeometer (ACP) for Improving the Atmospheric Longwave Irradiance Measurement (Poster)

Advancing climate change research requires accurate and traceable measurement of the atmospheric longwave irradiance. Current measurement capabilities are limited to an estimated uncertainty of larger than +/- 4 W/m2 using the interim World Infrared Standard Group (WISG). WISG is traceable to the Systeme international d'unites (SI) through blackbody calibrations. An Absolute Cavity Pyrgeometer (ACP) is being developed to measure absolute outdoor longwave irradiance with traceability to SI using the temperature scale (ITS-90) and the sky as the reference source, instead of a blackbody. The ACP was designed by NREL and optically characterized by the National Institute of Standards and Technology (NIST). Under clear-sky and stable conditions, the responsivity of the ACP is determined by lowering the temperature of the cavity and calculating the rate of change of the thermopile output voltage versus the changing net irradiance. The absolute atmospheric longwave irradiance is then calculated with an uncertainty of +/- 3.96 W/m2 with traceability to SI. The measured irradiance by the ACP was compared with the irradiance measured by two pyrgeometers calibrated by the World Radiation Center with traceability to the WISG

NREL Pyrheliometer Comparisons: 22 September - 3 October 2008

NREL Pyrheliometer Comparisons (NPCs) are held annually at the Solar Radiation Research Laboratory (SRRL) in Golden, Colorado. Open to all pyrheliometer owner/operators, the NPC provides an opportunity to determine the unique WRR transfer factor for each participating pyrheliometer. This paper reports on the results of NPC-2008, which was scheduled from September 22 to October 3, 2008

A radiation free alternative to CBCT volumetric rendering for soft tissue evaluation

Objective: The aim of the present study is to evaluate whether a “radiation free” method using 3D facial scan can replace Cone Beam Computed Tomography (CBCT) volumetric rendering of soft tissue of the patient to assess maxillofacial surgery outcomes and compare the reference points and angular measurements of patient facial soft tissue. Material and Methods: Facial soft tissue scan of the patient’s face, before and after orthognathic surgery and a CBCT of the skull for volumetric rendering of soft tissues were carried out. The 3D acquisitions were processed using Planmeca ProMax 3D ProFace® software (Planmeca USA, Inc.; Roselle, Illinois, USA). The participant were positioned in a natural position during the skull scannering. Three sagittal angular measurements were performed (Tr-NA, Tr-N-Pg, Ss-N-Pg) and two verticals (Go-N-Me, Tr-Or-Pg) on facial soft tissue scan and on the patient’s 3D soft tissue CBCT volumetric rendering. Results: A certain correspondence has been demonstrated between the measurements obtained on the Proface and those on the CBCT. Conclusion: A radiation free method was to be considered an important diagnostic tool that works in conditions of not subjecting the patient to harmful ionizing radiation and it was therefore particularly suitable for growing subjects. The soft tissue analysis based on the realistic facial scan has shown sufficient reliability and reproducibility even if further studies are needed to confirm the research result

Effect of energy window width on planer and SPECT image uniformity

AbstractTo detect radiopharmaceutical distribution in patient organs and avoid interpretation mistakes, due to the protocol errors, a gamma camera must work in optimum conditions. One such error is camera non-uniformity. Baron and Chouraqui[Baron, J.M., Chouraqui, P., 1996. Myocardial single-photon emission computed tomographic quality assurance. J. Nucl. Cordial. 3(2), 157–166] have reported the need to ensure consistently high image quality and accuracy using an optimally chosen standardized protocol. It has been reported that single photon emission computed tomography (SPECT) significantly improved contrast over the planer image and has the ability to separate overlapping structures[Critchly, M., 1993. Nuclear Medicine Pocket Handbook, Amersham International Plc, pp. 6–7]. Window width of energy is considered as one of the most important physical parameters affecting the quality of planer and SPECT images. Thus, the effect of widow widths of energy 5%, 10%, 15%, 20% and 25% on planer and SPECT images were investigated using a Tc-99m source at 140keV. Tc-99m is the most common isotope in nuclear medicine and has one well-defined peakT in comparison with thallium, which has three peaks. In the present study, it was evident that energy window width played a prominent role in flood images uniformity using the Tc-99m source. The calculated integral uniformity percentage (IU%) and differential uniformity percentage (DU%) values of center field of view (CFOV) and useful field of view (UFOV) were markedly changed with a change of energy window width. The optimum energy window width was in the range from 15% to 20%. Moreover, the effect of window widths of energy 5%, 10%, 15%, 20% and 25% on SPECT image on a heart phantom with an artificial defect performed at the anterior wall of the heart was investigated. The SPECT images were clinically examined by a physician who reported a different diagnosis for each energy window width due to vertical long axis cuts, which, in turn, were due to the change in the collected counts. We concluded that the optimum energy window width was also in the range 15–20% for the Tc-99m isotope, which confirmed previous planer results