NobleBlocks

Toshiba (United States)

companyNew York, New York, United States

Research output, citation impact, and the most-cited recent papers from Toshiba (United States) (United States). Aggregated across the NobleBlocks index of 300M+ scholarly works.

Total works
2.1K
Citations
125.9K
h-index
152
i10-index
2.1K
Also known as
Toshiba (United States)Toshiba America

Top-cited papers from Toshiba (United States)

High WSS or Low WSS? Complex Interactions of Hemodynamics with Intracranial Aneurysm Initiation, Growth, and Rupture: Toward a Unifying Hypothesis
Hui Meng, Vincent M. Tutino, J. Xiang, Adnan H. Siddiqui
2013· American Journal of Neuroradiology942doi:10.3174/ajnr.a3558

SUMMARY: Increasing detection of unruptured intracranial aneurysms, catastrophic outcomes from subarachnoid hemorrhage, and risks and cost of treatment necessitate defining objective predictive parameters of aneurysm rupture risk. Image-based computational fluid dynamics models have suggested associations between hemodynamics and intracranial aneurysm rupture, albeit with conflicting findings regarding wall shear stress. We propose that the "high-versus-low wall shear stress" controversy is a manifestation of the complexity of aneurysm pathophysiology, and both high and low wall shear stress can drive intracranial aneurysm growth and rupture. Low wall shear stress and high oscillatory shear index trigger an inflammatory-cell-mediated pathway, which could be associated with the growth and rupture of large, atherosclerotic aneurysm phenotypes, while high wall shear stress combined with a positive wall shear stress gradient trigger a mural-cell-mediated pathway, which could be associated with the growth and rupture of small or secondary bleb aneurysm phenotypes. This hypothesis correlates disparate intracranial aneurysm pathophysiology with the results of computational fluid dynamics in search of more reliable risk predictors.

MORPHOLOGY PARAMETERS FOR INTRACRANIAL ANEURYSM RUPTURE RISK ASSESSMENT
Sujan Dhar, Markus Tremmel, J Mocco, Minsuok Kim +4 more
2008· Neurosurgery587doi:10.1227/01.neu.0000316847.64140.81

OBJECTIVE: The aim of this study is to identify image-based morphological parameters that correlate with human intracranial aneurysm (IA) rupture. METHODS: For 45 patients with terminal or sidewall saccular IAs (25 unruptured, 20 ruptured), three-dimensional geometries were evaluated for a range of morphological parameters. In addition to five previously studied parameters (aspect ratio, aneurysm size, ellipticity index, nonsphericity index, and undulation index), we defined three novel parameters incorporating the parent vessel geometry (vessel angle, aneurysm [inclination] angle, and [aneurysm-to-vessel] size ratio) and explored their correlation with aneurysm rupture. Parameters were analyzed with a two-tailed independent Student's t test for significance; significant parameters (P < 0.05) were further examined by multivariate logistic regression analysis. Additionally, receiver operating characteristic analyses were performed on each parameter. RESULTS: Statistically significant differences were found between mean values in ruptured and unruptured groups for size ratio, undulation index, nonsphericity index, ellipticity index, aneurysm angle, and aspect ratio. Logistic regression analysis further revealed that size ratio (odds ratio, 1.41; 95% confidence interval, 1.03-1.92) and undulation index (odds ratio, 1.51; 95% confidence interval, 1.08-2.11) had the strongest independent correlation with ruptured IA. From the receiver operating characteristic analysis, size ratio and aneurysm angle had the highest area under the curve values of 0.83 and 0.85, respectively. CONCLUSION: Size ratio and aneurysm angle are promising new morphological metrics for IA rupture risk assessment. Because these parameters account for vessel geometry, they may bridge the gap between morphological studies and more qualitative location-based studies.

The design and implementation of a first-generation CELL processor
D. Pham, S. Asano, M. Bolliger, Michael Day +4 more
2005547doi:10.1109/isscc.2005.1493930

A CELL processor is a multi-core chip consisting of a 64b power architecture processor, multiple streaming processors, a flexible IO interface, and a memory interface controller. This SoC is implemented in 90nm SOI technology. The chip is designed with a high degree of modularity and reuse to maximize the custom circuit content and achieve a high-frequency clock-rate.

Nonenhanced MR Angiography
Mitsue Miyazaki, Vivian S. Lee
2008· Radiology403doi:10.1148/radiol.2481071497

While nonenhanced magnetic resonance (MR) angiographic methods have been available since the earliest days of MR imaging, prolonged acquisition times and image artifacts have generally limited their use in favor of gadolinium-enhanced MR angiographic techniques. However, the combination of recent technical advances and new concerns about the safety of gadolinium-based contrast agents has spurred a resurgence of interest in methods that do not require exogenous contrast material. After a review of basic considerations in vascular imaging, the established methods for nonenhanced MR angiographic techniques, such as time of flight and phase contrast, are considered and their advantages and disadvantages are discussed. This article then focuses on new techniques that are becoming commercially available, such as electrocardiographically gated partial-Fourier fast spin-echo methods and balanced steady-state free precession imaging both with and without arterial spin labeling. Challenges facing these methods and possible solutions are considered. Since different imaging techniques rely on different mechanisms of image contrast, recommendations are offered for which strategies may work best for specific angiographic applications. Developments on the horizon include techniques that provide time-resolved imaging for assessment of flow dynamics by using nonenhanced approaches.

Quantitative imaging biomarkers: A review of statistical methods for technical performance assessment
David Raunig, Lisa M. McShane, Gene Pennello, Constantine Gatsonis +4 more
2014· Statistical Methods in Medical Research381doi:10.1177/0962280214537344

Technological developments and greater rigor in the quantitative measurement of biological features in medical images have given rise to an increased interest in using quantitative imaging biomarkers to measure changes in these features. Critical to the performance of a quantitative imaging biomarker in preclinical or clinical settings are three primary metrology areas of interest: measurement linearity and bias, repeatability, and the ability to consistently reproduce equivalent results when conditions change, as would be expected in any clinical trial. Unfortunately, performance studies to date differ greatly in designs, analysis method, and metrics used to assess a quantitative imaging biomarker for clinical use. It is therefore difficult or not possible to integrate results from different studies or to use reported results to design studies. The Radiological Society of North America and the Quantitative Imaging Biomarker Alliance with technical, radiological, and statistical experts developed a set of technical performance analysis methods, metrics, and study designs that provide terminology, metrics, and methods consistent with widely accepted metrological standards. This document provides a consistent framework for the conduct and evaluation of quantitative imaging biomarker performance studies so that results from multiple studies can be compared, contrasted, or combined.

Shunt Active-Power-Filter Topology Based on Parallel Interleaved Inverters
Lucian Asiminoaei, Eddy Aeloiza, Prasad Enjeti, Frede Blaabjerg
2008· IEEE Transactions on Industrial Electronics380doi:10.1109/tie.2007.907671

In this paper, an interleaved active-power-filter concept with reduced size of passive components is discussed. The topology is composed of two pulsewidth-modulation interleaved voltage-source inverters connected together on the ac line and sharing the same dc-link capacitor. The advantages of the proposed approach are as follows: 1. significant reduction in the linkage inductors' size by decreasing the line-current ripple due to the interleaving; 2. reduction of the switching stress in the dc-link capacitor, due to the shared connection; and 3. more accurate compensation for high-power applications, because the power sharing allows one to use a higher switching frequency in each inverter. This paper analyzes the design of the passive components and gives a practical and low-cost solution for the minimization of the circulation currents between the inverters, by using common-mode coils. Several simulation results are discussed, and experimental results with a three-phase 10-kVA 400-V unit are obtained to validate the theoretical analysis.

Efficacy and current limitations of intravascular stents for intracranial internal carotid, vertebral, and basilar artery aneurysms
Giuseppe Lanzino, Ajay K. Wakhloo, Richard D. Fessler, Mary L. Hartney +2 more
1999· Journal of neurosurgery301doi:10.3171/jns.1999.91.4.0538

OBJECT: Results of previous in vitro and in vivo experimental studies have suggested that placement of a porous stent within the parent artery across the aneurysm neck may hemodynamically uncouple the aneurysm from the parent vessel, leading to thrombosis of the aneurysm. For complex wide-necked aneurysms, a stent may also aid packing of the aneurysm with Guglielmi detachable coils (GDCs) by acting as a rigid scaffold that prevents coil herniation into the parent vessel. Recently, improved stent system delivery technology has allowed access to the tortuous vascular segments of the intracranial system. The authors report here on the use of intracranial stents to treat aneurysms involving different segments of the internal carotid artery (ICA), the vertebral artery (VA), and the basilar artery (BA). METHODS: Ten patients with intracranial aneurysms located at ICA segments (one petrous, two cavernous, and three paraclinoid aneurysms), the VA proximal to the posterior inferior cerebellar artery origin (one aneurysm), or the BA trunk (three aneurysms) were treated since January 1998. In eight patients, stent placement across the aneurysm neck was followed (immediately in four patients and at a separate procedure in the remaining four) by coil placement in the aneurysm, accomplished via a microcatheter through the stent mesh. In two patients, wide-necked aneurysms (one partially thrombosed BA trunk aneurysm and one paraclinoid segment aneurysm) were treated solely by stent placement; coil placement may follow later if necessary. No permanent periprocedural complications occurred and, at follow-up examination, no patient was found to have suffered symptoms referable to aneurysm growth or thromboembolic complications. Greater than 90% aneurysm occlusion was achieved in the eight patients treated by stent and coil placement as demonstrated on immediate postprocedural angiograms. Follow-up angiographic studies performed in six patients at least 3 months later (range 3-14 months) revealed only one incident of in-stent stenosis. In the four patients originally treated solely by stent placement, no evidence of aneurysm thrombosis was observed either immediately postprocedure or on follow-up angiographic studies performed 24 hours (two patients), 48 hours, and 3 months later, respectively. CONCLUSIONS: A new generation of flexible stents can be used to treat complex aneurysms in difficult-to-access areas such as the proximal intracranial segments of the ICA, the VA, or the BA trunk. The stent allows tight coil packing even in the presence of a wide-necked, irregularly shaped aneurysm and may provide an endoluminal matrix for endothelial growth. Although convincing experimental evidence suggests that stent placement across the aneurysm neck may by itself promote intraluminal thrombosis, the role of this phenomenon in clinical practice may be limited at present by the high porosity of currently available stents.

Multiview Stereo via Volumetric Graph-Cuts and Occlusion Robust Photo-Consistency
George Vogiatzis, Carlos Hernández Esteban, Philip H. S. Torr, Roberto Cipolla
2007· IEEE Transactions on Pattern Analysis and Machine Intelligence286doi:10.1109/tpami.2007.70712

This paper presents a volumetric formulation for the multi-view stereo problem which is amenable to a computationally tractable global optimisation using Graph-cuts. Our approach is to seek the optimal partitioning of 3D space into two regions labelled as "object" and "empty" under a cost functional consisting of the following two terms: (1) A term that forces the boundary between the two regions to pass through photo-consistent locations and (2) a ballooning term that inflates the "object" region. To take account of the effect of occlusion on the first term we use an occlusion robust photo-consistency metric based on Normalised Cross Correlation, which does not assume any geometric knowledge about the reconstructed object. The globally optimal 3D partitioning can be obtained as the minimum cut solution of a weighted graph.

Treatment of intracranial aneurysms with the Enterprise stent: a multicenter registry
J Mocco, Kenneth V. Snyder, Felipe C Albuquerque, Bernard R. Bendok +4 more
2008· Journal of neurosurgery272doi:10.3171/2008.7.jns08322

OBJECT: The development of self-expanding stents dedicated to intracranial use has significantly widened the applicability of endovascular therapy to many intracranial aneurysms that would otherwise have been untreatable by endovascular techniques. Recent Food and Drug Administration approval of the Enterprise Vascular Reconstruction Device and Delivery System (Cordis) has added a new option for self-expanding stent-assisted intracranial aneurysm coiling. METHODS: The authors established a collaborative registry across multiple institutions to rapidly provide largevolume results regarding initial experience in using the Enterprise in real-world practice. Ten institutions (University at Buffalo, Thomas Jefferson University, University of Florida, Cleveland Clinic, Northwestern University, West Virginia University, University of Puerto Rico, Albany Medical Center Hospital, the Neurological Institute of Savannah, and the Barrow Neurological Institute) have provided consecutive data regarding their initial experience with the Enterprise. RESULTS: In total, 141 patients (119 women) with 142 aneurysms underwent 143 attempted stent deployments. The use of Enterprise assistance with aneurysm coiling was associated with a 76% rate of > or = 90% occlusion. An inability to navigate or deploy the stent was experienced in 3% of cases, as well as a 2% occurrence of inaccurate deployment. Procedural data demonstrated a 6% temporary morbidity, 2.8% permanent morbidity, and 2% mortality (0.8% unruptured, 12% ruptured). CONCLUSIONS: The authors report initial results of the largest series to date in using the Enterprise for intracranial aneurysm treatment. The Enterprise is associated with a high rate of successful navigation and low occurrence of inaccurate stent deployment. The overall morbidity and mortality rates were low; however, caution should be exercised when considering Enterprise deployment in patients with subarachnoid hemorrhage as the authors' experience demonstrated a high rate of associated hemorrhagic complications leading to death.

Use of Water Equivalent Diameter for Calculating Patient Size and Size-Specific Dose Estimates (SSDE) in CT: The Report of AAPM Task Group 220.
Cynthia H. McCollough, Donovan Bakalyar, Maryam Bostani, Samuel L. Brady +4 more
2014· PubMed270

Volume computed tomography dose index (CTDIvol) and dose length product (DLP) values are frequently used to represent radiation doses from a CT scan. The limitation of CTDIvol and DLP is that they are surrogates for patient dose, providing information about the scanner output for only a very specific standardized condition [1]. The dose received by a patient depends on both patient size and scanner output. Turner et al. showed that using CTDIvol as a normalization factor, organ dose estimates can be obtained for a specific patient size [2], and that the relationship to patient size was consistent across scanner models [3]. Their results showed a promising approach to estimating size-dependent, scanner-specific, and exam-specific organ doses based on patient size and the CTDIvol reported by the scanner. Hence, obtaining accurate information about patient size is crucial to estimating patient dose in CT. Report 204 from the American Association of Physicists in Medicine (AAPM) described the use of a size metric that involved the physical dimensions of the patient (anteroposterior [AP], lateral, AP+lateral, or effective diameter), in combination with scanner output (CTDIvol), to determine size-specific dose estimates (SSDE) from CT scanning [4]. Patient dimension can be determined using physical or electronic tools. Physical devices, such as the calipers that were frequently used in radiography before the routine use of phototiming, may be used to measure patient thickness in the AP or lateral directions. Alternatively, electronic measurement tools can be used to measure physical dimensions from either the CT localizer radiograph or an axial CT image. The conversion factors used to calculate SSDE from CTDIvol reported in AAPM Report 204 were derived from experimental and Monte Carlo data and normalized to patient size in terms of water- or tissue-equivalent materials. For the task of calculating SSDE, geometric size was used as a surrogate for a patient's x-ray attenuation. However, x-ray attenuation is the fundamental physical parameter affecting the absorption of x-rays and is thus more relevant than geometric patient size in determining the radiation dose absorbed by the patient. For example, regions of the thorax and abdomen could have the same external physical dimensions. However, because the lungs are less dense and of different composition than abdominal tissue, the thorax would attenuate fewer x-ray photons than would the abdomen. For the same scanner output (CTDIvol), the thorax region would experience a higher radiation fluence and, hence, have a higher absorbed dose than an abdominal region having the same geometric dimensions. While CT operators can measure a patient's AP or lateral width, they currently have no practical way to measure attenuation. Both a CT localizer radiograph and CT projection data are measurements of the integrated x-ray attenuation along a ray path, and a CT image is a cross-sectional map of the linear attenuation coefficients of the materials in the image, normalized to the linear attenuation of water. Therefore, the CT localizer radiograph, the CT projection data, and the CT image all contain information that can be used to estimate patient attenuation. The charge of AAPM Task Group 220 was to develop a robust and scientifically sound metric for automatically estimating patient size in CT that would account for patient attenuation and allow routine determination of SSDE for all patients, with little or no user intervention. This task group had a specific goal of developing a practical, standardized approach to estimating patient size that could be implemented by CT scanner manufacturers and others using CT localizer radiographs, axial CT images, or other data derived from the scanning process (e.g., projection data). Advantages and limitations of different methods were considered during task group deliberations and are summarized in this report. This includes comparing the SSDE calculated using various geometric size metrics, such as AP or lateral dimensions and effective diameter, and attenuation metrics, such as water equivalent diameter. Finally, recommendations are presented on the adoption and implementation of a standardized approach to estimating patient size. This report is organized as follows. First, the concept of water equivalent diameter (Dw) is presented, and the methodology of calculating it from either a CT image or a CT localizer radiograph image is described. Second, data are provided comparing the accuracy of Monte Carlo dose estimates made using geometrical-based versus attenuation-based metrics for a series of virtual abdomen and thorax phantoms and their respective virtual CT images, and for patient images. Third, data are provided comparing Dw calculations from CT image and CT localizer radiograph phantom measurements. Fourth, practical considerations involved in implementing either approach are discussed, and recommendations for users and for manufacturers are provided. Finally, a road map for commercial adoption is suggested such that both patient size and SSDE can be calculated in a robust and consistent fashion across CT scanner manufacturers, and the resultant values stored in either the DICOM image header or the DICOM-structured dose report.

Intracranial aneurysms: links among inflammation, hemodynamics and vascular remodeling
Tomoki Hashimoto, Hui Meng, William L. Young
2006· Neurological Research265doi:10.1179/016164106x14973

Abnormal vascular remodeling mediated by inflammatory cells has been identified as a key pathologic component of various vascular diseases, including abdominal aortic aneurysms, brain arteriovenous malformations and atherosclerosis. Based on findings from observational studies that analysed human intracranial aneurysms and experimental studies that utilized animal models, an emerging concept suggests that a key component of the pathophysiology of intracranial aneurysms is sustained abnormal vascular remodeling coupled with inflammation. This concept may provide a new treatment strategy to utilize agents to inhibit inflammation or cytokines produced by inflammatory cells such as matrix metalloproteinases. Such an approach would aim to stabilize these vascular lesions and prevent future expansion or rupture.

Prevention and Treatment of Thromboembolic and Ischemic Complications Associated with Endovascular Procedures: Part II???Clinical Aspects and Recommendations
Adnan I. Qureshi, Andreas R. Luft, Mudit Sharma, Lee R. Guterman +1 more
2000· Neurosurgery261doi:10.1097/00006123-200006000-00014

We reviewed the incidence, risk factors, and clinical features of thromboembolic and ischemic events associated with diagnostic cerebral angiography, endovascular treatment of aneurysms using coils or balloons, angioplasty and stent placement to treat extracranial carotid artery stenosis, and embolization of arteriovenous malformations using glue or other embolic agents. We performed a cumulative analysis to determine the frequency and characteristics of these events and a subset analysis (whenever possible) to determine the benefits of various strategies for complication avoidance. Of the 1,547 patients who underwent Guglielmi detachable coil treatment, thromboembolic events were observed for 127 (8.2%), consisting of asymptomatic events for 12 patients, transient ischemic attacks for 29, and strokes for 86. The outcomes for the 86 patients with strokes were categorized as full recovery for 15, good recovery for 27, partial recovery for 19, no recovery for 11, death for 12, and undetermined outcome for 2. Of the 834 patients who underwent carotid angioplasty and stent placement, thromboembolic events were observed for 73 (8.8%), consisting of transient ischemic attacks for 26 patients and strokes for 47. The outcomes for the patients with strokes were categorized as full recovery for 20, good recovery for 15, partial recovery for 6, no recovery for 2, and death for 4. High rates of thromboembolic events were also observed with balloon occlusion of aneurysms (11%) or parent arteries (19%) and carotid angioplasty alone (5.9%). Arteriovenous malformation embolization was associated with an ischemic event/procedure rate of 9.4%. High rates of thromboembolic and ischemic complications, with subsequent morbidity and death, are associated with most endovascular procedures. Further research and the formulation of standard preventive guidelines may help to reduce these risks and improve the overall success of these procedures.

Competitors' responses to easily imitated new products—exploring commercial banking product introductions
Ian C. MacMillan, Mary Lynn McCaffery, Gilles van Wijk
1985· Strategic Management Journal249doi:10.1002/smj.4250060106

Abstract The article describes an applied research project in which existing theory from the policy and organization theory literature was used to develop a rationale for estimating response times of competitors to easily imitated new products. A specific study of commercial banking product introductions is reported.

IEEE 802.21: Media independent handover: Features, applicability, and realization
Kenichi Taniuchi, Yoshihiro Ohba, Victor Fajardo, Samir R. Das +4 more
2009· IEEE Communications Magazine247doi:10.1109/mcom.2009.4752687

Providing users of multi-interface devices the ability to roam between different access networks is becoming a key requirement for service providers. The availability of multiple mobile broadband access technologies, together with the increasing use of real-time multimedia applications, is creating strong demand for handover solutions that can seamlessly and securely transition user sessions across different access technologies. A key challenge to meeting this growing demand is to ensure handover performance, measured in terms of latency and loss. In addition, handover solutions must allow service providers, application providers, and other entities to implement handover policies based on a variety of operational and business requirements. Therefore, standards are required that can facilitate seamless handover between such heterogeneous access networks and that can work with multiple mobility management mechanisms. The IEEE 802.21 standard addresses this problem space by providing a media-independent framework and associated services to enable seamless handover between heterogeneous access technologies. In this article, we discuss how the IEEE 802.21 standard framework and services are addressing the challenges of seamless mobility for multi-interface devices. In addition, we describe and discuss design considerations for a proof-of-concept IEEE 802.21 implementation and share practical insights into how this standard can optimize handover performance.

Prognostic Significance of Hypernatremia and Hyponatremia among Patients with Aneurysmal Subarachnoid Hemorrhage
Adnan I. Qureshi, M. Fareed K. Suri, Gene Sung, Robert N. Straw +4 more
2002· Neurosurgery247doi:10.1097/00006123-200204000-00012

OBJECTIVE: Abnormal serum sodium levels (hyponatremia and hypernatremia) are frequently observed during the acute period after aneurysmal subarachnoid hemorrhage (SAH) and may worsen cerebral edema and mass effect. We performed this study to determine the prognostic significance of serum sodium concentration abnormalities. METHODS: We analyzed prospectively collected data for the placebo treatment group in a clinical trial conducted at 54 neurosurgical centers in North America. The presence of hypernatremia (serum sodium concentration of >145 mmol/L) and hyponatremia (serum sodium concentration of <135 mmol/L) was determined with serum sodium measurements obtained at admission and 3, 6, and 9 days after SAH. The effects of hypernatremia and hyponatremia on the risk of symptomatic vasospasm and on 3-month outcomes were analyzed after adjustment for the following potential confounding factors: age, sex, preexisting hypertension, admission Glasgow Coma Scale score, initial mean arterial pressure, subarachnoid clot thickness, intraventricular blood or intraparenchymal hematoma, ventricular dilation, and aneurysm size and location. RESULTS: Of 298 patients in the analysis, 58 (19%) developed hypernatremia and 88 (30%) developed hyponatremia. Hypernatremia was significantly associated with poor outcomes (odds ratio, 2.7; 95% confidence interval, 1.2-6.1). A positive correlation was observed between the highest sodium values recorded and Glasgow Outcome Scale scores at 3 months (P < 0.0001 by analysis of variance). Hyponatremia was not associated with 3-month outcomes (odds ratio, 1.9; 95% confidence interval, 0.9-4.3). Neither hypernatremia nor hyponatremia was associated with the risk of symptomatic vasospasm. CONCLUSION: Hyponatremia seems to be more common than hypernatremia after SAH. However, hypernatremia after SAH is independently associated with poor outcomes, and this association is independent of previously identified outcome predictors, including age and admission Glasgow Coma Scale scores. Further studies are needed to define the underlying mechanism of this association.

Overview of the Architecture, Circuit Design, and Physical Implementation of a First-Generation Cell Processor
D. Pham, T. Aipperspach, D. Boerstler, M. Bolliger +4 more
2005· IEEE Journal of Solid-State Circuits236doi:10.1109/jssc.2005.859896

This paper reviews the design challenges that current and future processors must face, with stringent power limits, high-frequency targets, and the continuing system integration trends. This paper then describes the architecture, circuit design, and physical implementation of a first-generation Cell processor and the design techniques used to overcome the above challenges. A Cell processor consists of a 64-bit Power Architecture processor coupled with multiple synergistic processors, a flexible IO interface, and a memory interface controller that supports multiple operating systems including Linux. This multi-core SoC, implemented in 90-nm SOI technology, achieved a high clock rate by maximizing custom circuit design while maintaining reasonable complexity through design modularity and reuse.

Bluetooth
J.C. Haartsen, M. Naghshineh, Jon Inouye, O.J. Joeressen +1 more
1998· ACM SIGMOBILE Mobile Computing and Communications Review229doi:10.1145/1321400.1321402

A few years ago it was recognized that the vision of a truly low-cost, low-power radio-based cable replacement was feasible. Such a ubiquitous link would provide the basis for portable devices to communicate together in an ad hoc fashion by creating personal area networks which have similar advantages to their office environment counterpart - the local area network (LAN). Bluetooth is an effort by a consortium of companies to design a royalty free technology specification enabling this vision. This article describes the vision and goals of the Bluetooth program and introduces the radio-based technology.

In vivo detection of GABA and glutamate with MEGA‐PRESS: Reproducibility and gender effects
Ruth Tuura, Lars Michels, Richard A.E. Edden, James B. Murdoch +1 more
2011· Journal of Magnetic Resonance Imaging226doi:10.1002/jmri.22520

PURPOSE: To evaluate the reproducibility of γ-amino-butyric acid (GABA) and glutamate concentrations derived using three different spectral fitting methods, and to investigate gender-related differences in neurotransmitter levels. MATERIALS AND METHODS: Single voxel MEGA-edited PRESS MR spectra were acquired from a 30-mL voxel in the dorso-lateral prefrontal cortex in 14 adult volunteers (7 female) at 3 Tesla (3T). For each participant, four consecutive resting spectra were acquired within the same scanning session. Metabolite concentrations were derived using LCModel, jMRUI, and locally written peak fitting software. The within-session reproducibility for each analysis method was calculated as the average coefficient of variation (CV) of the GABA and Glx (glutamate+glutamine) concentrations. Gender differences in GABA and Glx were evaluated using a two-tailed unpaired t-test. RESULTS: LCModel provided the best reproducibility for both GABA (CV 7%) and Glx (CV 6%). GABA, Glx, and glutamate concentrations were significantly higher in the male participants, (P = 0.02, P = 0.001, and P < 0.001, respectively). CONCLUSION: GABA and glutamate can be quantified in vivo with high reproducibility (CV 6-7%) using frequency-domain spectral fitting methods like LCModel. However, the GABA and glutamate concentrations vary significantly between men and women, emphasizing the importance of gender-matching for studies investigating differences in neurotransmitter concentrations between mixed-cohort groups.

Principles and applications of multienergy CT: Report of AAPM Task Group 291
Cynthia H. McCollough, Kirsten Boedeker, Dianna D. Cody, Xinhui Duan +4 more
2020· Medical Physics223doi:10.1002/mp.14157

In x-ray computed tomography (CT), materials with different elemental compositions can have identical CT number values, depending on the mass density of each material and the energy of the detected x-ray beam. Differentiating and classifying different tissue types and contrast agents can thus be extremely challenging. In multienergy CT, one or more additional attenuation measurements are obtained at a second, third or more energy. This allows the differentiation of at least two materials. Commercial dual-energy CT systems (only two energy measurements) are now available either using sequential acquisitions of low- and high-tube potential scans, fast tube-potential switching, beam filtration combined with spiral scanning, dual-source, or dual-layer detector approaches. The use of energy-resolving, photon-counting detectors is now being evaluated on research systems. Irrespective of the technological approach to data acquisition, all commercial multienergy CT systems circa 2020 provide dual-energy data. Material decomposition algorithms are then used to identify specific materials according to their effective atomic number and/or to quantitate mass density. These algorithms are applied to either projection or image data. Since 2006, a number of clinical applications have been developed for commercial release, including those that automatically (a) remove the calcium signal from bony anatomy and/or calcified plaque; (b) create iodine concentration maps from contrast-enhanced CT data and/or quantify absolute iodine concentration; (c) create virtual non-contrast-enhanced images from contrast-enhanced scans; (d) identify perfused blood volume in lung parenchyma or the myocardium; and (e) characterize materials according to their elemental compositions, which can allow in vivo differentiation between uric acid and non-uric acid urinary stones or uric acid (gout) or non-uric acid (calcium pyrophosphate) deposits in articulating joints and surrounding tissues. In this report, the underlying physical principles of multienergy CT are reviewed and each of the current technical approaches are described. In addition, current and evolving clinical applications are introduced. Finally, the impact of multienergy CT technology on patient radiation dose is summarized.

Influence of respiration on cerebrospinal fluid movement using magnetic resonance spin labeling
Shinya Yamada, Mitsue Miyazaki, Yuichi Yamashita, Cheng Ouyang +4 more
2013· Fluids and Barriers of the CNS213doi:10.1186/2045-8118-10-36

BACKGROUND: Magnetic resonance imaging (MRI) cardiac gated phase contrast (PC) cine techniques have non-invasively shown the effect of the cardiac pulse on cerebrospinal fluid (CSF) movement. Echo planar imaging (EPI) has shown CSF movement as influenced by both cardiac pulsation and respiration. Previously, it has not been possible to visualize CSF movement in response to respiration non-invasively. The present study was undertaken to do so. METHODS: The effect of respiration on CSF movement was investigated using a non-contrast time-spatial labeling inversion pulse (Time-SLIP) with balanced steady-state free precession (bSSFP) readout. CSF movement was observed in the intracranial compartment in response to respirations in ten normal volunteers. To elucidate the respiration effect, the acquisition was triggered at the beginning of deep inhalation, deep exhalation and breath holding. RESULTS: By employing this respiration-induced spin labeling bSSFP cine method, we were able to visualize CSF movement induced by respiratory excursions. CSF moved cephalad (16.4 ± 7.7 mm) during deep inhalation and caudad (11.6 ± 3.0 mm) during deep exhalation in the prepontine cisternal area. Small but rapid cephalad (3.0 ± 0.4 mm) and caudad (3.0 ± 0.5 mm) movement was observed in the same region during breath holding and is thought to reflect cardiac pulsations. CONCLUSIONS: The Time-SLIP bSSFP cine technique allows for non-invasive visualization of CSF movement associated with respiration to a degree not previously reported.