Library

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
    Springer
    European radiology 8 (1998), S. 834-838 
    ISSN: 1432-1084
    Keywords: Key words: Magnetic resonance imaging ; Brain hemorrhage ; FSE ; GRASE ; Susceptibility artefact
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. The aim of this study was to evaluate the sensitivity of gradient-and-spin-echo (GRASE) sequences to susceptibility effects. GRASE sequences with 21 and 33 echoes per echo train were compared with a T2-weighted FSE sequence with an echo train length of 5 by means of MRI in phantoms, volunteers (n = 10), and patients (n = 19) with old hemorrhagic brain lesions. All experiments were performed on a 1.0-T clinical MR system (Impact Expert, Siemens AG, Erlangen, Germany) with constant imaging parameters. Contrast-to-noise ratios (CNRs) of tubes doped with iron oxides at different concentrations, of brain areas with physiological iron deposition (red nucleus, substantia nigra), and of areas of old brain hemorrhage were calculated for FSE and GRASE pulse sequences. Areas of old brain hemorrhage were also qualitatively analyzed for the degree of visible susceptibility effects by blinded reading. The CNR of iron oxide tubes and iron-containing brain areas decreased with increasing echo trains of GRASE sequences. The CNR of GRASE sequences decreased when compared with CNR of their FSE counterparts (GRASE 21 echo trains 23.8 ± 0.8, FSE 5 echo trains 26.7 ± 0.9; p≤ 0.01). Qualitative analysis confirmed these measurements. FSE with an ETL of 5 demonstrated significantly stronger susceptibility effects than their GRASE counterpart with an ETL of 21. The results demonstrate that GRASE sequences do not necessarily compensate for the reduced sensitivity of FSE to susceptibility effects. The complex signal behavior of GRASE makes conventional SE, gradient echo, or FSE sequences containing shorter echo trains preferable when patients with intracranial hemorrhage are clinically evaluated.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 2
    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
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...