Design of a Viscometer Using Magnetostriction of Ferromagnetic Probes

On-line measurement of viscosity of process liquids at process temperature is difficult though industrially very important. A viscometer is designed which can do this up to about 300 °C almost on-line within about 1-8% accuracy except for very viscous liquids like glucose. It uses a ferromagnetic probe designed to mechanically vibrate in the ultrasonic frequency range. An excitation coil sends repeated excitation current pulses to induce mechanical vibration in the probe tip. When placed in a process fluid, the vibration amplitude is damped due to the viscosity of the fluid, and the damped vibration is sensed by Faraday\u27s principle by a sensing coil. The number of pulses per second needed to keep the probe vibrating above a threshold level is directly proportional to the viscosity of the fluid. Necessary calibration was done and the performance tested using several pure liquids as references with known viscosities in the range 0.1 - 2,000 cp at temperatures between -80 and +300°C

Effect of Low Refocusing Angle in T1-Weighted Spin Echo and Fast Spin Echo MRI on Low-Contrast Detectability: A Comparative Phantom Study at 1.5 and 3 Tesla

MRI tissue contrast is not well preserved at high field. In this work, we used a phantom with known, intrinsic contrast (3.6%) for model tissue pairs to test the effects of low angle refocusing pulses and magnetization transfer from adjacent slices on intrinsic contrast at 1.5 and 3 Tesla. Only T1-weighted spin echo sequences were tested since for such sequences the contrast loss, tissue heating, and image quality degradation at high fields seem to present significant diagnostic and quality issues. We hypothesized that the sources of contrast loss could be attributed to low refocusing angles that do not fulfill the Hahn spin echo conditions or to magnetization transfer effects from adjacent slices in multislice imaging. At 1.5 T the measured contrast was 3.6% for 180° refocusing pulses and 2% for 120° pulses, while at 3 T, it was 4% for 180° and only 1% for 120° refocusing pulses. There was no significant difference between single slice and multislice imaging suggesting little or no role played by magnetization transfer in the phantom chosen. Hence, one may conclude that low angle refocusing pulses not fulfilling the Hahn spin echo conditions are primarily responsible for significant deterioration of T1-weighted spin echo image contrast in high-field MRI

Brain arteriovenous malformations: The long way ahead in physics, chemistry and MR-Angiography practice before fully replacing digital subtraction angiography.

Typically, only high field systems are equipped with stronger gradients and short RF pulse designs, a must for high temporal resolution that are also responsible for high SAR, high susceptibility as well as neurostimulation. Gradient induced image noise tends to be high at 3T. Often vendors try to ameliorate such increased image noise with multi-channel head arrays and aggressive filter designs allowing an appearance of high SNR and CNR quality; however, the achievable SNR and CNR in the AVM remain limited as the analyzed articles by Zhuo et al seem to have in common. A short term solution to harvest advantages of high fields with acceptable T2* loss may be to use fast 3D shimming to generate a high degree of homogeneity in the operator selected AVM tissue. In addition, to avoid susceptibility increase at high fields by the contrast pooled into neovasculature, not only for AVM but also for other vascular imaging applications, improved CM design need to accompany any such robust shimming routines. Until that and more are achieved, DSA may retain its superiority in the follow-ups of treated AVMs

Utilizing Fast Spin Echo MRI to Reduce Image Artifacts and Improve Implant/Tissue Interface Detection in Refractory Parkinson's Patients with Deep Brain Stimulators

Introduction:. In medically refractory Parkinson's disease (PD) deep-brain stimulation (DBS) is an effective therapeutic tool. Postimplantation MRI is important in assessing tissue damage and DBS lead placement accuracy. We wanted to identify which MRI sequence can detect DBS leads with smallest artifactual signal void, allowing better tissue/electrode edge conspicuity. Methods:. Using an IRB approved protocol 8 advanced PD patients were imaged within MR conditional safety guidelines at low RF power (SAR ≤ 0.1 W/kg) in coronal plane at 1.5T by various sequences. The image slices were subjectively evaluated for diagnostic quality and the lead contact diameters were compared to identify a sequence least affected by metallic leads. Results and Discussion. Spin echo and fast spin echo based low SAR sequences provided acceptable image quality with comparable image blooming (enlargement) of stimulator leads. The mean lead diameters were 2.2 ± 0.1 mm for 2D, 2.1 ± 0.1 mm for 3D, and 4.0 ± 0.2 mm for 3D MPRAGE sequence. Conclusion:. Low RF power spin echo and fast spin echo based 2D and 3D FSE sequences provide acceptable image quality adjacent to DBS leads. The smallest artifactual blooming of stimulator leads is present on 3D FSE while the largest signal void appears in the 3D MPRAGE sequence

Constraints on background torsion field from K physics

We point out that a background torsion field will produce an effective potential to the $K$ and $\bar{K}$ with opposite signs. This allows us to constrain the background torsion field from the $K_L$ and $K_S$ mass difference, CPT violating $K^\circ$ and $\bar{K^\circ}$ mass difference and the CP violating quantities $\epsilon$ and $\eta_{+-}$. The most stringent bound on the cosmological background torsion $< 10^{-25}$ GeV comes from the direct measurement of the CPT violation.Comment: 12 pages latex fil

Quantifying Cerebellum Grey Matter and White Matter Perfusion Using Pulsed Arterial Spin Labeling

To facilitate quantification of cerebellum cerebral blood flow (CBF), studies were performed to systematically optimize arterial spin labeling (ASL) parameters for measuring cerebellum perfusion, segment cerebellum to obtain separate CBF values for grey matter (GM) and white matter (WM), and compare FAIR ASST to PICORE. Cerebellum GM and WM CBF were measured with optimized ASL parameters using FAIR ASST and PICORE in five subjects. Influence of volume averaging in voxels on cerebellar grey and white matter boundaries was minimized by high-probability threshold masks. Cerebellar CBF values determined by FAIR ASST were 43.8 ± 5.1 mL/100 g/min for GM and 27.6 ± 4.5 mL/100 g/min for WM. Quantitative perfusion studies indicated that CBF in cerebellum GM is 1.6 times greater than that in cerebellum WM. Compared to PICORE, FAIR ASST produced similar CBF estimations but less subtraction error and lower temporal, spatial, and intersubject variability. These are important advantages for detecting group and/or condition differences in CBF values

Radiobiology & Radiation Benefits in Alzheimer’s from CT: a physics assessment

This work is a review and assessment of research literature on Alzheimer’s disease (AD) today which is an irreversible neurological disorder, that continuously decreases the individual’s memory and thinking skills and, suddenly, the ability to carry out the simplest functions of daily living. Although treatment can only help manage the symptoms of AD, there is no cure for the disease. CT imaging is proven to be somewhat helpful in the detection of AD disease similar to MRI, multiple repeat CT seems to show promise in part-reversing the loss (radiation Hormesis). Invivo exposure, spatial distribution, and quantitative characterization could be essential markers in diagnosing and assessing AD progression. Phase-Contrast X-ray microcomputed tomography (micro CT) is an emerging highly sensitive imaging technique capable of high resolution and impressive soft tissue discrimination. FDG and Pittsburgh compound B PET are functional tools to map affected brain with AD. There is a potential to extend it to imaging precise 3D information about the inner structures of the entire brain in future using clinical CT machines but with phase contrast software without requiring thin sections. However, we feel clinical scanners with phase contrast modes will not provide the plaque imaging exactly for 50 μm for individual plaques but plaque tangles and high tissue contrast resolution for hippocampus structures as in highfield MRI may be possible by phase contrast CT

Sleep-Wake Disturbances in Mild Traumatic Brain Injury: Meta analysis of Literature and Modeling of Cerebral Tissue Vulnerability

Sleep disturbance is a frequent complaint for patients with mild traumatic brain injury (mTBI), it can prolong recovery, and the oxidative stress from lack of sleep could worsen other secondary damages of mTBI. The common types of sleep disturbance of mTBI include insomnia, daytime sleepiness, and obstructive sleep apnea. Conventional imaging often fails to detect any abnormalities in mTBI, and the etiology of sleep disturbance is still unclear. Based on the analysis of current published neurobiological and imaging literature, multiple factors could play a role leading to sleep disturbance in mTBI, however, we have focused on the diencephalon, melatonin and serotonin. We constructed a hypothesis that sleep disturbance may be caused by increased tau protein and decreased serotonin consequent to the dynamic load to pineal gland and hypothalamus by cerebrospinal fluid (CSF) during and after mild head trauma. A geometric model supporting this is under preparation in analogy with Alzheimer’s progression in less actives and Parkinson’s cases with upper body rigidity. In both situations CSF dynamics is abnormal and tau protein increases while serotonin/melatonin levels drop. Our model of impaired circulation of CSF leading to inefficient transportation of sleep-related protein, and excessive encounter of vulnerable tissues (Pineal gland and Hypothalamus for example) with reactive oxygen species due to abnormal CSF dynamics may contribute to dysfunction of sleep governing neuron

Modeling Changes in Cellular Micro-Environment in Mild to Moderate Head Trauma

Our work aims to connect and model multiple small, inter-related tissue injuries as a consequence of mild traumatic brain injuries (mTBI). It has been shown that frontal and temporal lobes are vulnerable regions for brain traumatic injury. A brain injury from a blow or high-speed impact can cause undersurface of the frontal and temporal lobes to deform against the anterior and cranial fossae. This deformation can often trigger damage to the cerebral vasculature, which is ill-understood and can result in chronic damage to larger vessels over time. These physiological injuries can be manifested psychologically; such as patients’ sleep-wake disturbances. The connection between mTBI and the cause of sleep-issues is found to be associated with vascular epithelial injuries to the pineal gland that lies directly at the anterior to the tentorial ridge. In this research, we are modeling brain trauma with two injuries tissue gliding between temporal, frontal and parietal lobes. The frontal lobe may explain the psychological problem and parietal may explain the large venous injury, while the midbrain including pineal and hypothalamus injury may explain sleep issues. Although white matter connectivity is disturbed, the literature is not enough for us to include that within our cell injury model. Learning from these devastating symptoms of mTBI, it is critical to push for more scientific researches to understand the mTBI and offer psychosocial as well as neurobiological interventions

Texture of a Four-Neutrino Mass Matrix

We propose a simple texture of the neutrino mass matrix with one sterile neutrino along with the three standard ones. It gives maximal mixing angles for $\nu_e \to \nu_S$ and $\nu_\mu \to \nu_\tau$ oscillations or vice versa. Thus with only four parameters, this mass matrix can explain the solar neutrino anomaly, atmospheric neutrino anomaly, LSND result and the hot dark matter of the universe, while satisfying all other Laboratory constraints. Depending on the choice of parameters, one can get the vacuum oscillation or the large angle MSW solution of the solar neutrino anomaly.Comment: 11 pages latex file; Revised version (to be published in Phys. Lett. B