Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Accuracy of vertebral mineral determination by dual-energy quantitative computed tomography (1991)
    Springer
    Skeletal radiology 20 (1991), S. 25-29 
    Details
    ISSN: 1432-2161
    Keywords: Dual-energy quantitative computed tomography ; Basis material decomposition ; Accuracy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Quantitative computed tomography is an established method for the non-invasive assessment of bone mineral content. Scanning with two different X-ray energies allows material-selective image reconstruction and separation on the basis of differing atomic numbers. As proven by chemophysical analysis of 45 bone samples, dual-energy quantitative computed tomography with basis material decomposition allows highly accurate measurement of bone mineral density with an error of 1.4%, independent of fat and soft tissue content.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00243717
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Grundlagen und Technik der Spiral-CT (1999)
    Springer
    Der Radiologe 39 (1999), S. 809-819 
    Details
    ISSN: 1432-2102
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Die Spiral-CT wurde vor genau 10 Jahren in die klinische Praxis eingeführt, die ersten Berichte erfolgten zum RSNA 1989 [1]. Es dauerte nur wenige Jahre, bis die Spiral-CT allgemein akzeptiert wurde. Sie stellt inzwischen den universellen Aufnahmemodus bei den meisten CT-Untersuchungen dar. Alle neueren technischen Entwicklungen, wie z.B. Mehrzeilen-Detektoren, zielen darauf ab, Volumenuntersuchungen mit der Spiral-CT noch schneller und in höherer Qualität durchführen zu können. In diesem Beitrag sollen die Prinzipien der Methode dargestellt, bildqualitätsrelevante Details präsentiert und Dosisaspekte erörtert werden. Zu detaillierteren Darstellungen der Spiral-CT und zu den neuesten technischen Entwicklungen sei auf ein aktuelles Buch hingewiesen, dem auch Tabelle 2 und die Bilder zu diesem Beitrag entnommen wurden [2]. Die Spiral-CT stellt im zehnten Jahr ihres Bestehens aus technischer Sicht ein ausgereiftes Verfahren dar. Datenerfassung bei der Spiral-CT
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001170050581
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Letter (1996)
    Springer
    Osteoporosis international 6 (1996), S. 183-184 
    Details
    ISSN: 1433-2965
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01623945
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    A PC program for estimating organ dose and effective dose values in computed tomography (1999)
    Springer
    European radiology 9 (1999), S. 555-562 
    Details
    ISSN: 1432-1084
    Keywords: Key words: CT ; Spiral CT ; Dose ; Organ dose ; Effective dose
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. Dose values in CT are specified by the manufacturers for all CT systems and operating conditions in phantoms. It is not trivial, however, to derive dose values in patients from this information. Therefore, we have developed a PC-based program which calculates organ dose and effective dose values for arbitrary scan parameters and anatomical ranges. Values for primary radiation are derived from measurements or manufacturer specifications; values for scattered radiation are derived from Monte Carlo calculations tabulated for standard anthropomorphic phantoms. Based on these values, organ doses can be computed by the program for arbitrary scan protocols in conventional and in spiral CT. Effective dose values are also provided, both with ICRP 26 and ICRP 60 tissue-weighting coefficients. Results for several standard CT protocols are presented in tabular form in this paper. In addition, potential for dose reduction is demonstrated, for example, in spiral CT and in quantitative CT. Providing realistic patient dose estimates for arbitrary CT protocols is relevant both for the physician and the patient, and it is particularly useful for educational and training purposes. The program, called WinDose, is now in use at the Erlangen University hospitals (Germany) as an information tool for radiologists and patients. Further extensions are planned.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003300050709
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Dose reduction in computed tomography by attenuation-based on-line modulation of tube current: evaluation of six anatomical regions (2000)
    Springer
    European radiology 10 (2000), S. 391-394 
    Details
    ISSN: 1432-1084
    Keywords: Key words: Computed tomographic Spiral – Dose reduction – Image quality – Technical aspects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. This study investigated the potential of attenuation-based on-line modulation of tube current to reduce the dose of computed tomography (in milliamperes) without loss in image quality. The dose can be reduced for non-circular patient cross-sections by reducing the tube current at the angular positions at which the diameter through the patient diameter is smallest. We investigated a new technical approach with attenuation-based on-line modulation of tube current. Computed tomographic projection data were analyzed to determine the optimal milliampere values for each projection angle in real time, instead of performing prior measurements with localizer radiographs. We compared image quality, noise pattern, and dose for standard scans and for scans with attenuation-based on-line modulation of tube current in a group of 30 radiation therapy patients. Six different anatomical regions were examined: head, shoulder, thorax, abdomen, pelvis, and extremities (knee). Image quality was evaluated by four radiologists in a blinded fashion. We found the dose to be reduced typically by 15–50 %. In general, no deterioration in image quality was observed. Thus the dose in computed tomography be reduced substantially by technical measures without sacrificing image quality. Attenuation-based on-line modulation of tube current is an efficient and practical means for this.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003300050062
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Mikro-CT Technologie und Applikationen zur Erfassung von Knochenarchitektur (1999)
    Springer
    Der Radiologe 39 (1999), S. 203-212 
    Details
    ISSN: 1432-2102
    Keywords: SchlüsselwörterµCT: Technologie ; µCT: Applikationen ; Knochenstruktur ; 3D Bildgebung ; Histomorphometrie ; Key wordsµCT: technology ; µCT: applications ; Bone structure ; 3D imaging ; Histomorphometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary The strength and fracture resistance of bone is determined by the structure of the trabecular network and the cortical shell. While standard 2D techniques like histomorphometry are inadequate to assess the 3D nature of the trabecular network, isotropic 3D datasets of this network can be acquired with the new imaging modality of µCT. However, so far the quantitative analysis of the generated datasets, in particular the extraction of appropriate parameters describing the bone structure, has not been finally solved. In this article we describe the technology and applications of µCT systems relevant in the field of osteology. The most important technical features of current µCT systems in this context are: 1. A spatial resolution down to 5–10 µm can be achieved. 2. The maximum sample size is related to the desired resolution by a factor of approximately 1000, that is, a resolution of 10 µm limits the maximum sample size to approximately 1 cm. 3. Scan times for µCT systems vary between minutes and hours. Currently five areas for the application of µCT systems in osteology can be identified: 1. The search of parameters characterizing the 3D trabecular structure. 2. The application of finite element models to determine the biochemical competence of the structural parameters. 3. The use of µCT in preclinical trials to study drug effects in small animals. 4. The validation of analysis methods used in high-resolution in-vivo imaging systems. 5. The 3D quantification of modeling and remodeling processes.
    Notes: Zusammenfassung Die Stärke und Bruchfestigkeit von Knochen wird durch seine trabekuläre und kortikale Struktur bestimmt. Mit zweidimensionalen Meßverfahren wie der Histomorphometrie kann die dreidimensionale Natur des Trabekelnetzwerkes nicht adäquat erfaßt werden. Isotrope 3D Datensätze können mit dem neuen bildgebenden Verfahren der µCT erzeugt werden. Die Frage nach geeigneten Strukturparametern zur Beschreibung des trabekulären Netzwerkes ist allerdings letztendlich noch nicht gelöst. In diesem Beitrag beschreiben wir Technologie und Anwendungen der µCT, welche für das Gebiet der Osteologie relevant sind. Als wichtigste technische Faktoren in diesem Kontext sind derzeit zu nennen: 1. Eine räumliche Auflösung von 5–10 µm kann erzielt werden. 2. Probengröße und Auflösung hängen ca. über einen Faktor 1000 zusammen: Bei einer zu erzielenden Auflösung von 10 µm ist die maximale Probengröße auf etwa 1 cm begrenzt. 3. Die Scanzeiten liegen im Bereich von Minuten bis Stunden. Im Bereich der Osteologie wird die µCT derzeit auf 5 Gebieten eingesetzt: 1. Zur Suche und Optimierung von Parametern, die die dreidimensionale Trabekelstruktur charakterisieren. 2. Die Anwendung von Finite-Elemente Methoden zur Bestimmung der biomechanischen Wertigkeit der stereologischen Parameter. 3. Der Einsatz in der präklinischen Forschung zu in-vivo Verlaufskontrollen in kleinen Labortieren. 4. Die Validierung von Analysemethoden, die in hochauflösenden in-vivo Verfahren zur Osteoporosediagnostik angewendet werden. 5. Die dreidimensionale Quantifizierung von Modeling- und Remodelingprozessen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001170050497
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Konstruktion und Einsatz eines virtuellen anthropomorphen Phantoms des Bronchialbaums (2000)
    Springer
    Der Radiologe 40 (2000), S. 240-245 
    Details
    ISSN: 1432-2102
    Keywords: Schlüsselwörter Spiral-CT ; Bronchialsystem ; Phantom ; Fraktale ; Key words Spiral CT ; Bronchial system ; Phantom ; Fractals
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Motivation: Usually, phantoms are used to quantify properties of computer algorithms working on spiral CT data. The high complexity of the human bronchial tree, however, complicates the construction of a physical phantom enormously; hence, a virtual phantom must be employed. Methods: Because the human bronchial tree is fractal, Lindenmayer systems were utilized to generate its structure. Applying the correct diameter and length ratios and branching angles, a virtual anthropomorphic phantom could be generated by a three-dimensional turtle graphic. The simulation of a spiral CT measurement on the virtual phantom delivered synthetic spiral CT data. Results: The computer-controlled growing process supplies exact morphologic and morphometric data. The spiral CT simulation saves the time-consuming and complicated generation of a physical phantom. Perspective: The virtual phantom can be completed by the introduction of blood vessels and lung parenchyma partitioned into lobes and segments. The field of application can thus be extended.
    Notes: Zusammenfassung Motivation: Um Eigenschaften von Nachverarbeitungsalgorithmen, die auf Spiral-CT-Daten arbeiten, quantifizierbar zu machen, werden normalerweise Phantome verwendet. Im Fall des Bronchialsystems jedoch erschwert die sehr hohe Komplexität den Bau eines realen Phantoms. Eine Lösung für dieses Problem bietet ein virtuelles Bronchialsystemphantom, dessen dreidimensionales Abbild ein synthetischer Spiral-CT-Datensatz ist. Methode: Da das Bronchialsystem eine fraktale Struktur aufweist, wurde zu seiner Generierung ein Lindenmayer-System benutzt, das unter der Einhaltung von Längen- und Durchmesserverhältnissen sowie Verzweigungswinkeln mit einer dreidimensionalen Turtle-Graphik zu einem anthropomorphen Abbild umgesetzt wurde. Die Simulation einer Spiral-CT-Messung erzeugt die synthetischen Spiral-CT-Daten für beliebige Scanparameter. Ergebnisse: Der computergesteuerte Wachstumsprozess des virtuellen Phantoms liefert exakte morphologische und morphometrische Daten und damit eine Bewertungsgrundlage. Die Spiral-CT-Simulation erspart den zeitaufwendigen und komplizierten Bau des Phantoms. Ausblick: Das virtuelle Bronchialsystemphantom lässt sich durch das Einbringen von Blutgefäßen und Lungenparenchym, aufgeteilt in Lappen und Segmente, zu einem virtuellen Lungenphantom ergänzen, wodurch sich sein Anwendungsgebiet erweitert.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001170050663
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Reduction of dose in pelvic examinations of infants using modern X-ray techniques (1979)
    Springer
    Pediatric radiology 8 (1979), S. 233-235 
    Details
    ISSN: 1432-1998
    Keywords: Radiography ; Fluorography ; Hip dysplasia ; Diaphragm ; Dose reduction ; Infants ; Phantom
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A simple dose-saving procedure for the diagnosis of congenital hip dysplasia employing a diaphragm in near-focus position is presented. Doses to the skin and the gonads are measured with a phantom, comparing the new and other techniques. With optimal techniques the skin dose is smaller than 2 mR and the gonadal doses lie around 0.1 mR for both male and female patients.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00974041
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Effective dose values in bone mineral measurements by photon absorptiometry and computed tomography (1992)
    Springer
    Osteoporosis international 2 (1992), S. 82-87 
    Details
    ISSN: 1433-2965
    Keywords: Bone mineral density ; Dual-energy X-ray absorptiometry ; Computed tomography ; Radiation dose
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A high degree of uncertainty and irritation predominates in the assessment and comparison of radiation dose values resulting from measurements of bone mineral density of the lumbar spine by photon absorptiometry and X-ray computed tomography. The skin dose values which are usually given in the literature are of limited relevance because the size of the irradiated volumes, the relative sensitivity of the affected organs and the radiation energies are not taken into account. The concept of effective dose, sometimes called whole-body equivalent dose, has to be applied. A detailed analysis results in an effective dose value of about 1 µSv for absorptiometry and about 30 µSv for computed tomography when low kV and mAs values are used. Lateral localizer radiographs, which are necessary for slice selection in CT, mean an additional dose of 30 µSv. Lateral X-ray films of the spine which are frequently taken in combination with absorptiometry result in a dose of 700 µSv or more. The concept of effective dose, the basic data and assumptions used in its assessment and a comparison with other dose burdens (for example the natural background radiation, of typically 2400 µSv per year) are discussed in detail.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01623841
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    European semi-anthropomorphic spine phantom for the calibration of bone densitometers: Assessment of precision, stability and accuracy the European quantitation of osteoporosis study group (1995)
    Springer
    Osteoporosis international 5 (1995), S. 174-184 
    Details
    ISSN: 1433-2965
    Keywords: Cross-calibration ; Dual X-ray absorptiometry (DXA) ; European Spine Phantom (ESP) ; Osteoporosis ; Quantitative computed tomography (QCT)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Up to now it has not been possible to reliably cross-calibrate dual-energy X-ray absorptiometry (DXA) densitometry equipment made by different manufacturers so that a measurement made on an individual subject can be expressed in the units used with a different type of machine. Manufacturers have adopted various procedures for edge detection and calibration, producing various normal ranges which are specific to each individual manufacturer's brand of machine. In this study we have used the recently described European Spine Phantom (ESP, prototype version), which contains three semi-anthropomorphic “vertebrae” of different densities made of simulated cortical and trabecular bone, to calibrate a range of DXA densitometers and quantitative computed tomography (QCT) equipment used in the measurement of trabecular bone density of the lumbar vertebrae. Three brands of QCT equipment and three brands of DXA equipment were assessed. Repeat measurements were made to assess machine stability. With the large majority of machines which proved stable, mean values were obtained for the measured low, medium and high density vertebrae respectively. In the case of the QCT equipment these means were for the trabecular bone density, and in the case of the DXA equipment for vertebral body bone density in the posteroanterior projection. All DXA machines overestimated the projected area of the vertebral bodies by incorporating variable amounts of transverse process. In general, the QCT equipment gave measured values which were close to the specified values for trabecular density, but there were substantial differences from the specified values in the results provided by the three DXA brands. For the QCT and Norland DXA machines (posteroanterior view), the relationships between specified densities and observed densities were found to be linear, whereas for the other DXA equipment (posteroanterior view), slightly curvilinear, exponential fits were found to be necessary to fit the plots of observed versus specified densities. From these plots, individual calibration equations were derived for each machine studied. For optimal cross-calibration, it was found to be necessary to use an individual calibration equation for each machine. This study has shown that it is possible to cross-calibrate DXA as well as QCT equipment for the measurement of axial bone density. This will be of considerable benefit for large-scale epidemiological studies as well as for multi-site clinical studies depending on bone densitometry.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02106097
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...