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  • 1
    Electronic Resource
    Electronic Resource
    Pulmonary circulation (1998)
    Springer
    European radiology 8 (1998), S. 698-706 
    Details
    ISSN: 1432-1084
    Keywords: Key words: CT pulmonary arteries ; MRI pulmonary arteries ; MRA ; CTA ; Pulmonary thromboembolism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. Evaluation of the pulmonary vasculature is mainly indicated in patients with suspected pulmonary thromboembolism. The routine procedure so far is ventilation-perfusion scintigraphy alone or in combination with diagnostic assessment of the legs to rule out deep venous thrombosis. The results are still not reliable for the majority of patients. In the case of equivocal diagnosis, invasive conventional angiography is considered the gold standard. With steady improvements in tomographic imaging techniques, such as computed tomography (CT) or magnetic resonance imaging (MRI), non-invasive alternatives to the routine diagnostic work-up are given. Helical CT and CTA techniques are already in clinical use and estimated to sufficiently serve the demands for detection/exclusion of pulmonary thromboembolism. The disadvantages mainly concern peripheral disease and reconstruction artifacts. MRI and MR angiography have been implemented in the diagnosis of pulmonary vascular disease since the introduction of contrast-enhanced MRA. In breath-hold techniques, the entire lung vascularization can be delineated and thromboemboli can be detected. The clinical experience in this field is limited, but MRI has the potential to demonstrate its superiority over CT due to its improved delineation of the vascular periphery and the more comprehensive three-dimensional reconstruction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003300050462
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  • 2
    Electronic Resource
    Electronic Resource
    Phase-contrast MR angiography of peripheral arteries: technique and clinical application (1999)
    Springer
    European radiology 9 (1999), S. 122-127 
    Details
    ISSN: 1432-1084
    Keywords: Key words: MR-Angiography (MRA) ; Phase-Contrast-MRA (PC-MRA) ; Peripheral Arterial Occlusive Disease (PAOD) ; Stenoses ; Occlusions ; Aneurysms ; Postsurgical follow-up
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. This articles describes Phase-Contrast-MRA (PC-MRA) techniques and their current clinical applications for peripheral arteries based on more than 250 clinical MRA studies performed at two institutions. PC-MRA depends on phase shifts caused by blood flow and thus this technique permits the use of coronal or sagittal slice orientations with large FOV's along the direction of the vessel of interest. Clinical applications focus on patients with peripheral arterial occlusive disease (PAOD) describing the role and limitations of PC-MRA for the work-up of stenoses, occlusions, aneurysms, and postsurgical follow-up. Recommendations for clinical routine are provided. A combined MR angiographic approach with various MRA techniques depending on the vessel segment to be imaged, PC-flow velocity measurements, and high-resolution scans of the vessel wall may turn out to be diagnostically effective and provide a comprehensive test for PAOD within the near future.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003300050642
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  • 3
    Electronic Resource
    Electronic Resource
    Clinical utility of contrast-enhanced MR angiography (1997)
    Springer
    European radiology 7 (1997), S. S178 
    Details
    ISSN: 1432-1084
    Keywords: Key words: Magnetic resonance angiography ; Contrast media ; Pulmonary arteries ; Carotid arteries ; Renal arteries
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. MR angiography (MRA) is a technique under ongoing discussion. Its non-invasiveness and sensitivity to flow irregularities make it an investigational technique which is easy to apply but which does not always lead to comprehensive results. It requires special skill to perform and also experience for correct interpretation of the results. The lengthiness of the procedure combined with certain physical properties tends to limit its use to mostly neurovascular applications. With the introduction of ultrafast MRA in conjunction with peripheral bolus-injection of extracellular contrast media, a new approach to the imaging of such regions as the thoracic and abdominal vasculature not to mention other vascular territories has become possible. In this paper, considerations of bolus and measurement optimization and timing protocols for dedicated indications are presented together with an overview on the experience acquired to date for CE-MRA of the carotid artery, mediastinal and pulmonary vessels, abdominal vasculature, and peripheral vessels. The main advantage of ultrafast CE-MRA is that patients are subjected to much more tolerable breath-hold investigations with the result that physiological motion such as peristalsis or major pulsation is minimised.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00006890
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  • 4
    Electronic Resource
    Electronic Resource
    Home traction in the management of congenital dislocation of the hip (1984)
    Springer
    Archives of orthopaedic and trauma surgery 102 (1984), S. 135-140 
    Details
    ISSN: 1434-3916
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Eine retrospektive Studie wurde an 60 Kindern mit einer congenitalen Hüftluxation an 78 Hüftgelenken durchgeführt, bei denen die Extensions-Einrenkungsbehandlung zu Hause durchgeführt wurde. Die Wirksamkeit der Extension und die Häufigkeit schwerer Komplikationen sollte ermittelt werden, insbesondere die Häufigkeit und die Ausdehnung avaskulärer Nekrosen. 30 andere Kinder mit 42 congenital luxierten Hüftgelenken, bei denen die Extensions-Einrenkungsbehandlung im Krankenhaus durchgeführt wurde, dienten als Kontrollgruppe. Bei jeweils 2 Hüftgelenken in jeder Gruppe gelang es mit der Extension nicht, die Stellung des Hüftkopfes gegenüber dem Acetabulum zu verbessern. Die Häufigkeit der avasculären Nekrosen betrug bei den zu Hause behandelten Hüften 17,9% und bei den im Krankenhaus behandelten 23,8%. Bei der letztgenannten Gruppe waren auch die schweren Nekroseformen häufiger. Es hat sich herausgestellt, daß die Extensionsbehandlung zu Hause eine vorteilhafte Alternative zu der Behandlung im Krankenhaus darstellt, weil sie sicher, wirksam und kostensparend ist. Es muß jedoch betont werden, daß eine richtige Auswahl der Patienten und eine sorgfältige Überwachung des Behandlungsprogramms erforderlich sind.
    Notes: Summary A retrospective review of sixty children with seventy-eight congenitally dislocated hips who had pre-reduction traction at home was undertaken to assess the effectiveness of the traction and the incidence of severe complications, with specific reference to the incidence and severity of avascular necrosis. Thirty other children with forty-two congenitally dislocated hips who had pre-reduction traction while in the hospital were used as controls. Traction failed to radiologically improve the position of the head in relation to the acetabulum in two hips in each group. The incidence of avascular necrosis was 17.9 percent in hips treated at home and 23.8 percent in hips treated in the hospital. The hospital control group demonstrated higher incidences of the more severe types of necrosis. Traction at home was found to be an advantageous alternative to traction in the hospital, in that it is safe, effective, and less costly; however, it must be stressed that proper patient selection and careful monitoring of the program are required.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00575221
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  • 5
    Electronic Resource
    Electronic Resource
    MR angiography of the thoracic vessels (1997)
    Springer
    Der Radiologe 37 (1997), S. 529-538 
    Details
    ISSN: 1432-2102
    Keywords: Key words Magnetic resonance angiography (MRA) • MRA-contrast media • MRA-aorta • MRA-pulmonary vessels ; Schlüsselwörter Magnetresonanzangiographie (MRA) • MRA-Kontrastmittel • MRA-Aorta • MRA-Pulmonalgefäße
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Mit der Einführung schneller Gradientensysteme, die eine echoplanare Bildgebung (EPI) erlauben, wurden auch in der Magnetresonanzangiographie (MRA) neuartige Techniken möglich, die jetzt durch ultraschnelle Meßzeiten große Gefäßregionen in einem einzigen Atemstillstandszyklus untersuchen. Hierdurch lassen sich die bewegungsinduzierten Bildunschärfen reduzieren oder aufheben, darüber hinaus sind auch physikalische Störphänomene wie Signalsättigung oder Dephasierung durch die extrem kurzen Echozeiten minimalisiert. Die bei der kurzen Akquisition insgesamt reduzierte Signalausbeute wird in der vorgestellten Technik durch die Applikation eines intravenös verabreichten Gadoliniumpräparates aufgehoben. Die Koordination des Meßvorganges mit der ersten Passage des Kontrastmittels („first pass“) durch die Untersuchungsregion ist analog zu einer Computertomographieangiographie (CTA) essentiell. Die Kontrastmittel-MRA (KM-MRA) eröffnet durch die Geschwindigkeit und den hohen Kontrast neue Indikationsbereiche: so werden erstmals diagnostisch verwertbare Angiogramme der pulmonalen Gefäßstrombahn möglich. In der vorliegenden Arbeit werden Berechnung und Versuche zur Optimierung der KM-MRA der thorakalen Gefäße vorgestellt. Vorschläge zur Parameterkonstellation der MRA-Sequenz und zur Optimierung der Kontrastmittelapplikation werden anhand von Probandenmessungen erarbeitet und physikalisch erläutert. Die KM-MRA der pulmonalen Strombahn wird als Single-dose-Technik in einem Zeitrahmen von ca. 30 s empfohlen. Erste Erfahrungen an Patienten und Korrelationen zu alternativen Untersuchungstechniken werden angeboten. Bei dem noch frühen Entwicklungsstand der Technik kann noch keine letztliche Einschätzung der klinischen Relevanz gegeben werden.
    Notes: Summary Through the introduction of newly invented high-performance gradient systems to MRI, which enable for echoplanar imaging (EPI), also magnetic resonance angiography (MRA) has gained an entirely new field of applications and techniques. Ultrafast imaging techniques in MRA allow the investigation of larger vascular areas within a single breathhold-period. Artifacts like motion induced signal misregistrations, dephasing or saturation of the vascular signal are minimized by extremely short echo times. The technique thus requires the intravenous application of a contrast media bolus, usually a gadolinium compound, which is in standard clinical use. Coordination of the bolus injection and the timing of the data acquisition is crucial for optimal results. The first pass evaluation of the contrast media resembles CTA to a certain extend. Due to the fast measurement and the high contrast in contrast-enhanced MRA (CE-MRA) new applications and indications are developed like MRA of the pulmonary vessels. The paper offers considerations and trials for optimization of thoracical CE-MRA. Besides parameter constellation also bolus-optimization is described with respect to the dedicated anatomical premises. Investigations on volunteers and on patients build a basis for suggestions on optimized CE-MRA procedures. To date, a final estimation of the clinical value of the new technique cannot be given since ongoing improvements change the optimal protocol frequently and the potential of further developments is high.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001170050250
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  • 6
    Electronic Resource
    Electronic Resource
    Phase-contrast MR angiography of the lower extremity. Comparison of methods and clinical application (1997)
    Springer
    Der Radiologe 37 (1997), S. 572-578 
    Details
    ISSN: 1432-2102
    Keywords: Key words MR angiography • Time of flight • Phase contrast • Peripheral arteries ; Schlüsselwörter MR-Angiographie • Time-of-Flight • Phasenkontrast • Periphere Gefäße
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Ziel der Studie war die Entwicklung einer praktikablen Untersuchungsstrategie für die MRA der unteren Extremität. Im Probandenteil der Studie wurden 3 MRA-Techniken (2D-TOF mit venöser Sättigung, 3D-Magnitude-Kontrast und 2D-Phasenkontrast mit EKG-Triggerung) intraindividuell prospektiv verglichen. Im Patiententeil der Studie wurden bei n = 45 klinischen MRA-Untersuchungen mittels EKG-getriggerter 2D-PCA 230 Gefäßsegmente intraindividuell mit der arteriellen DSA nach einem fünfstufigen Scoresystem verglichen. EKG-getriggerte PCA-Techniken zeigten die beste Bildqualität in allen Gefäßabschnitten. Dabei betrug der mittlere Rang des Friedman-Testes der PCA-Technik in der Beckenetage 1,2 und an der Oberschenkel- bzw. Knie-/Unterschenkeletage 1,0. Die Patientenuntersuchungen zeigten eine gute Übereinstimmung von DSA und MRA mit einem signifikanten Spearman-Korrelationskoeffizient für die Becken-, Oberschenkel- und Knieetage. MRA-Untersuchungen der unteren Extremität sind unter Einsatz der EKG-getriggerten 2D-PCA-Technik mit vertretbarem Zeitaufwand möglich. Die Abbildungmöglichkeiten der untersuchten Gefäßetagen entsprechen den Bildeinstellungen der DSA und die klinische Auswertung ergab eine gute (Kappa 〉 0,61) bis sehr gute (Kappa 〉 0,81) Übereinstimmung in der Beurteilung pathologischer Gefäßveränderungen.
    Notes: Summary Purpose: To investigate whether phase-contrast MRA is a clinically suited approach to examine arteries of the pelvis and lower extremities. Methods: The study was divided into two parts, a volunteer study and patient study. Three MRA techniques – 2D TOF with venous saturation, 3D magnitude contrast and 2D phase contrast with ECG triggering – were intraindividually compared in 15 volunteers and evaluated by three blinded readers. Subsequently, a total of 230 vessel segments of 45 MRA studies using ECG-triggered phase contrast were compared with intraarterial DSA. All vessel segments were scored by three blinded readers using a five-point scale with DSA serving as the gold standard. Results: ECG-triggered phase contrast provided better image quality than the other MRA techniques as assessed by the Friedman test. Clinical studies demonstrated a significant correlation of DSA and MRA as assessed by the Spearman correlation and kappa statistics for individual readers. Conclusion: MRA of the pelvis and lower extremities may be performed with 2D ECG-triggered phase-contrast MRA within a reasonable time frame ( 〈 30 min). MRA slabs provide orientation similar to that with DSA projections and good to very good correlation of vessel pathology as shown by kappa statistics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001170050255
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  • 7
    Electronic Resource
    Electronic Resource
    Conventional MRA and contrast- enhanced MRA of extracranial vessel segments (1997)
    Springer
    Der Radiologe 37 (1997), S. 515-528 
    Details
    ISSN: 1432-2102
    Keywords: Key words Magnetic resonance angiography (MRA) • Contrast-enhanced MRA (CE-MRA) • MRA carotids • Contrast agent dosage • Time-of-flight MRA (TOF MRA) ; Schlüsselwörter Magnetresonanzangiographie (MRA) • MRA-Kontrastmittel • MRA-A. carotis • Time-of-flight-MRA • Kontrastmitteldosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Die Einführung schneller Gradientensysteme erlaubt eine qualitativ sehr gute Darstellung der extrakraniellen Karotisstrombahn in der Magnetresonanzangiographie (MRA) und findet Anwendung in der klinischen Routine. Mit der bevorzugt angewandten Time-of-flight-(TOF-)Technik können Gefäße ohne Kontrastmittel dargestellt werden. Die Anwendung ultraschneller Gradientenechosequenzen (GES) ermöglicht bei intravenöser Bolusinjektion von Gadolinium eine First-pass-Darstellung der Karotiden vom Aortenbogen bis zur Schädelbasis in weniger als 30 s Meßzeit. In der vorliegenden Arbeit werden die Vor- und Nachteile beider Techniken diskutiert. Für eine qualitativ optimale kontrastmittelunterstützte MRA (CE-MRA) sind der richtige Zeitpunkt der Menge und Flußrate Kontrastmittel-(KM-) Injektion und die Abstimmung der Sequenzparameter auf den relativ schnellen Blutrückflusses aus den venösen Sinus in die Vv. jugulares zu berücksichtigen. Zunächst wurden an einem Modell und in einer Computersimulation der optimale Zeitpunkt der Datenakquisition bezüglich der Anwesenheit von KM in den Arterien bestimmt. Dabei zeigte sich, daß 90 % des Kontrastes in den mittleren 16 % der symetrisch akquirierten k-Raumzeilen definiert werden. Durch schrittweise Variation von Ortsauflösung, Meßzeit und KM-Injektionsparameter wurde ein Meßprotokoll an Probanden und einigen Patienten erarbeitet, welches den klinischen Einsatz der CE-MRA im Bereich der extrakraniellen Karotisstrombahn ermöglicht. Voraussetzung ist die genaue Bestimmung der Bolusankunftszeit mittels Testbolusinjektion. Die besten qualitativen Ergebnisse wurden mit einer Double-dose-Technik bei 2 ml/s Injektionsgeschwindigkeit erreicht. Die zeitlichen Reserven ultraschneller Sequenzen sollten in die Verbesserung der Auflösung investiert werden. Weitere Untersuchungen über die optimale KM-Applikation beim noch sehr frühen Stand der Technik stehen noch aus.
    Notes: Summary The introduction of fast gradient systems allows a reliable visualization of the extracranial carotid vessels by the magnetic resonance angiography (MRA) which meanwhile is implemented into clinical routine. By the mainly applied time-of-flight (TOF) technique, vessels can be imaged without contrast agent (CA). Due to the application of ultra-fast gradient-echo-sequences, the first-pass evaluation of an intravenous bolus-injection of Gadolinium in the carotids from the aortic arch up to the skull base can be performed in less than 30 s. In this study, advantages and disadvantages of both techniques are discussed. For a qualitatively optimal contrast enhanced MRA (CE-MRA) timing parameters like injection delay, flow rate and the adjustment of sequence parameters have to be considered in relation to the fast venous return from the sinus to the jugular veins. First, the optimal time point of the data acquisition have been determined at a model and with a computer simulation in reference to the presence of CA in the arteries. As a result, 90 % of the contrast contribution is defined by 16 % of the symmetrically acquired central k-space lines. A measuring protocol for clinical use was obtained by a gradual variation of spacial resolution, measuring time and CA-injection parameters and was proved in normal volunteers and patients. An exact determination of the bolus-arrival-time by means of a test-bolus injection was acquired. The best qualitative results were achieved by a double-dose injection at 2 ml/s injection rate. The temporal reserves of ultra-fast sequences should be invested in the improvement of the spatial resolution. To date, further investigations related to the problem of optimal CA-application may improve the potentials of CE-MRA procedures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001170050249
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