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Technical Parameters (technical + parameter)

Distribution by Scientific Domains

Medical Sciences	62%

Selected Abstracts

Lactate Detection by MRS in Mitochondrial Encephalopathy: Optimization of Technical Parameters

JOURNAL OF NEUROIMAGING, Issue 1 2008
Antônio José da Rocha MD
ABSTRACT Mitochondriopathies are a heterogeneous group of diseases with variable phenotypic presentation, which can range from subclinical to lethal forms. They are related either to DNA mutations or nuclear-encoded mitochondrial genes that affect the integrity and function of these organelles, compromising adenosine triphosphate (ATP) synthesis. Magnetic resonance (MR) is the most important imaging technique to detect structural and metabolic brain abnormalities in mitochondriopathies, although in some cases these studies may present normal results, or the identified brain abnormalities may be nonspecific. Magnetic resonance spectroscopy (MRS) enables the detection of high cerebral lactate levels, even when the brain has normal appearance by conventional MR scans. MRS is a useful tool for the diagnosis of mitochondriopathies, but must be correlated with clinical, neurophysiological, biochemical, histological, and molecular data to corroborate the diagnosis. Our aim is to clarify the most relevant issues related to the use of MRS in order to optimize its technical parameters, improving its use in the diagnosis of mitochondriopathies, which is often a challenge. [source]

Development, standardization, and testing of a lexicon for reporting contrast-enhanced breast magnetic resonance imaging studies

JOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 6 2001
Debra M. Ikeda MD
Abstract The purpose of this study was to develop, standardize, and test reproducibility of a lexicon for reporting contrast-enhanced breast magnetic resonance imaging (MRI) examinations. To standardize breast MRI lesion description and reporting, seven radiologists with extensive breast MRI experience developed consensus on technical detail, clinical history, and terminology reporting to describe kinetic and architectural features of lesions detected on contrast-enhanced breast MR images. This lexicon adapted American College of Radiology Breast Imaging and Data Reporting System terminology for breast MRI reporting, including recommendations for reporting clinical history, technical parameters for breast MRI, descriptions for general breast composition, morphologic and kinetic characteristics of mass lesions or regions of abnormal enhancement, and overall impression and management recommendations. To test morphology reproducibility, seven radiologists assessed morphology characteristics of 85 contrast-enhanced breast MRI studies. Data from each independent reader were used to compute weighted and unweighted kappa (,) statistics for interobserver agreement among readers. The MR lexicon differentiates two lesion types, mass and non-mass-like enhancement based on morphology and geographical distribution, with descriptors of shape, margin, and internal enhancement. Lexicon testing showed substantial agreement for breast density (, = 0.63) and moderate agreement for lesion type (, = 0.57), mass margins (, = 0.55), and mass shape (, = 0.42). Agreement was fair for internal enhancement characteristics. Unweighted kappa statistics showed highest agreement for the terms dense in the breast composition category, mass in lesion type, spiculated and smooth in mass margins, irregular in mass shape, and both dark septations and rim enhancement for internal enhancement characteristics within a mass. The newly developed breast MR lexicon demonstrated moderate interobserver agreement. While breast density and lesion type appear reproducible, other terms require further refinement and testing to lead to a uniform standard language and reporting system for breast MRI. J. Magn. Reson. Imaging 2001;13:889,895. © 2001 Wiley-Liss, Inc. [source]

Lactate Detection by MRS in Mitochondrial Encephalopathy: Optimization of Technical Parameters

Radiofrequency Neurotomy for Low Back Pain: Evidence-Based Procedural Guidelines

PAIN MEDICINE, Issue 2 2005
W. Michael Hooten MD
ABSTRACT Objective., This review was undertaken to outline the procedural limitations of the randomized controlled trials (RCTs) of radiofrequency (RF) neurotomy for low back pain. Second, the literature related to patient selection, diagnostic testing, and the technique of performing lumbar spine, RF neurotomy will be critically reviewed and analyzed. Based on these analyses, diagnostic and procedural guidelines will be proposed. Design., A Medline and EMBASE search identified three RCTs and two systematic reviews of RF neurotomy for low back pain. A similar search identified pertinent literature related to the method of patient selection for a diagnostic block, the medial branch and L5 dorsal ramus comparative block, and the anatomical and technical parameters of lumbar spine RF neurotomy. Results., Substantial procedural shortcomings were identified in all three RCTs. In the systematic reviews, these procedural limitations were not accounted for by the quality assessment of study design which resulted in an inaccurate estimate of clinical effectiveness. Analysis using likelihood ratios showed that screening criteria could increase the probability of zygapophysial joint pain before performing diagnostic blocks. Similar analysis showed that comparative medial branch blocks, rather than single blocks, must be used before RF neurotomy. Anatomical studies demonstrated that the shorter distal compared with the circumferential radius of the RF lesion necessitates placement of the electrode parallel to the course of the nerve along the base of the superior articular process. Conclusions., The evidence-based procedural guidelines provide consistent criteria for multisite studies that could enroll a sufficiently large homogenous study cohort. [source]

Technical decomposition approach of critical to quality characteristics for Product Design for Six Sigma

QUALITY AND RELIABILITY ENGINEERING INTERNATIONAL, Issue 4 2010
Yihai He
Abstract Product Design for Six Sigma (DFSS) approach is a structural and disciplined methodology driven by critical to quality characteristics (CTQs). How to identify and decompose the CTQs is the kernel part in the DFSS process. Traditional method only depends on the quality function deployment (QFD) matrix to flow down CTQs roughly. The paper puts forward a novel technical approach for CTQs decomposition from customer requirements into critical technical parameters based on the relational tree. Specifically, this approach emphasizes the systematic process and quantitative computation on quality relation weight. In order to specify the object of product DFSS, the connotation and evolution model of CTQs are created first. Then along the product development process, a decomposition measure for relational tree of CTQs is studied based on the functional and physical trees in Axiomatic Design (AD). And the quality relation weight computation of its nodes by means of Rough Set and fuzzy Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) is explored. Finally, an application on a car body noise vibration harshness (NVH) improvement, as an example, is given, and the decomposition process of NVH related with the functional and physical trees as well as its node weights computation algorithm are expounded in detail. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Evaluation of a Navigation System for ENT with Surgical Efficiency Criteria,

THE LARYNGOSCOPE, Issue 4 2006
Gero Strau MD
Abstract The aim of this study is the evaluation of a navigation system (NaviBase) for ENT surgery. For this purpose, a new methodology for the evaluation of surgical and ergonomic system properties has been developed. The practicability of the evaluation instruments will be examined using the example of the overall assessment of the system in comparison with the current surgical standard and with other systems using clinical efficiency criteria. The evaluation is based on 102 ENT surgical applications; of these, 89 were functional endoscopic sinus surgeries (FESS). The evaluation of surgical and ergonomic performance factors was performed by seven ENT surgeons. To evaluate surgical system properties, the Level of Quality (LOQ) in 89 cases of the FESS was determined. It compares the existing information of the surgeon with that of the navigation system on a scale of 0 to 100 and with a mean value of 50 and places it in a relationship to the clinical impact. The intraoperative change of the planned surgical strategy (Change of Surgical Strategy) was documented. The ergonomic factors of the system with the categories of Overall Confidence (Trust), awareness of the situation (Situation Awareness), influence on the operating team, requirements for specific skills (Skill Set Requirement), and cognitive load (Workload Shift) were recorded for all surgical procedures as Level of Reliance (LOR). In the evaluation of the surgical system properties, an average evaluation of the quality of the information, as an LOQ of 63.59, resulted. Every second application of the navigation system (47.9%), on average, led to a change in the surgical strategy. An extension/enhancement of the indication of the endonasal approach through the use of the navigation system was shown in 7 of 102 (6.8%) cases. The completion of the resection in the FESS was rated by 74% of group I and 11% of group II as better in comparison with the standard approach. Total confidence shows a positive evaluation of 3.35 in the LOR. To supplement the evaluation of the navigation system, the technical parameters were included. The maximum deviation, Amax, of the displayed position of the reference value amounted to 1.93 mm. The average deviation was at 1.29 mm with an SD above all values, sd, of 0.29. The subsequent economic evaluation resulted in an effective average extra expenditure of time of 1.35 minutes per case. The overall evaluation of the system imparts application-relevant information beyond the technical details and permits comparability between different assistance systems. [source]

CLAY RESOURCES AND TECHNICAL CHOICES FOR NEOLITHIC POTTERY (CHALAIN, JURA, FRANCE): CHEMICAL, MINERALOGICAL AND GRAIN-SIZE ANALYSES*

ARCHAEOMETRY, Issue 1 2007
R. MARTINEAU
Many authors have considered pottery manufacturing constraints and sociocultural elements as factors in change in past civilizations over time. The main issue of this research is to better understand the reasons for changes, or choices, in pottery raw materials. The very precise and detailed stratigraphy and cultural succession of occupations is based on dendrochronological data from the lake-dwelling sites of Chalain (Jura, France). Petrographic, palaeontological and chemical analyses were used to determine the nature and origins of the raw materials used by the Neolithic potters. Stratigraphy and dendrochronological data were used to reconstruct in detail the evolution dynamics of fabric changes. Several raw material sources were identified for many of the pottery groups. Each of them was sampled for qualitative experimental tests of pottery forming. The experimental results show a high variability between the sediments tested. This variability was quantitatively estimated by XRF, XRD, the Rietveld method, calcium carbonate quantification and laser grain-size analyses of matrices, indirect measures of plasticity. These analytical results allow a better understanding of the differences observed in the experimental tests. On the basis of these experimental and analytical results, changing parameters such as pottery manufacturing constraints, mineralogical characteristics of raw materials and sociocultural factors are considered. In conclusion, all the social and technical parameters, in each archaeological context, must be taken into account for a better understanding of the changes occurring throughout the chronological sequence. [source]

Design and Characterization of a Rotating Bed System Bioreactor for Tissue Engineering Applications

BIOTECHNOLOGY PROGRESS, Issue 1 2008
Fabienne Anton
The main challenge in the development of bioreactors for tissue engineering is the delivery of a sufficient nutrient and oxygen supply for cell growth in a 3D environment. Thus, a new rotating bed system bioreactor for tissue engineering applications was developed. The system consists of a culture vessel as well as an integrated rotating bed of special porous ceramic discs and a process control unit connected with the reactor to ensure optimal culturing conditions. The aim of the project was the design and construction of a fully equipped rotating bed reactor, and in particular, the characterization and optimization of the system with regard to technical parameters such as mixing time and pH-control to guarantee optimal conditions for cell growth and differentiation. Furthermore, the applicability of the developed system was demonstrated by cultivation of osteoblast precursor cells. The porous structure of the ceramic discs and the external medium circulation loop provide an optimal environment for tissue generation in long-term cultivations. Mass transfer limitations were minimized by the slow rotation, which also provides the cells with sufficient nutrients and oxygen through alternate contact to air and medium. An osteoblast precursor cell line was successfully cultivated in this bioreactor for 28 days. [source]