Your email was sent successfully. Check your inbox.

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

Proceed reservation?

Proceed order?

Export
  • 1
    Keywords: CONTAMINATION ; lipid ; cancer research ; NEURONS ; MAGNETIC-RESONANCE ; lipids ; PERFORMANCE ; QUANTIFICATION ; CANCER ; brain ; SIGNAL ; TIME
    Abstract: Despite its prominent peak in 1H-MRS of the brain and its near exclusivity to neurons, the absolute amount of N-Acetylaspartate (NAA) is difficult to obtain due to signal contamination from skull lipids. Here we report the performance of two methods that overcome this problem to yield the whole-brain NAA signal (WBNAA). WBNAA was obtained from twelve volunteers with both a lipid- and NAA-nulling scheme. Despite being twofold quicker, the lipid-nulling technique had a higher intrinsic (5.8%vs8.6%) and longitudinal (10.6%vs19.7%) coefficient of variation when compared with NAA-nulling. Therefore, when time is critical, lipid-nulling is viable, otherwise, however NAA-nulling is more precise.
    Type of Publication: Proceeding
    Signatur Availability
    BibTip Others were also interested in ...
  • 2
    Keywords: brain ; CELLS ; CELL ; imaging ; QUANTIFICATION ; DISEASE ; NEW-YORK ; NUCLEAR-MEDICINE ; TIME ; MARKER ; MR ; QUANTITATION ; SEQUENCE ; SEQUENCES ; SUPPRESSION ; DISORDER ; SIGNAL ; FIELD ; SPECTROSCOPY ; WATER ; PERFORMANCE ; ACQUISITION ; AGE ; WOMEN ; REPRODUCIBILITY ; MEN ; MAGNETIC-RESONANCE SPECTROSCOPY ; NMR ; HEAD ; lipids ; HEALTHY ; nuclear medicine ; MULTIPLE-SCLEROSIS ; PROTON MR SPECTROSCOPY ; radiology ; DISORDERS ; ADULT ; MS ; methods ; NUCLEAR ; CRITERIA ; USA ; SIGNALS ; COEFFICIENTS ; MEDICINE ; comparison ; cancel
    Abstract: BACKGROUND AND PURPOSE: Despite the prominent peak of N-acetylaspartate (NAA) in proton MR spectroscopy (H-1-MR spectroscopy) of the adult brain and its almost exclusive presence in neuronal cells, the total amount of NAA, regarded as their marker, is difficult to obtain due to signal contamination from the skull lipids. This article compares the performance of 2 methods that overcome this difficulty to yield the whole-brain NAA signal, important for the assessment of the total disease load in diffuse neurologic disorders. MATERIALS AND METHODS: The heads of 12 healthy volunteers, 3 women and 9 men, 31.0 +/- 7.1 years of age, were scanned at 3T by using 2 nonlocalizing H-1-MR spectroscopy sequences: One nulls the NAA (TI = 940 ms) every second acquisition by inversion-recovery to cancel the signals of the lipids (T1 〈〈 TI) in an add-subtract scheme. The other nulls the signal of the lipids (TI = 155 ms) directly after each acquisition, requiring half as many averages for the same signal-to-noise ratio. Each sequence was repeated 3 times back-to-back on 3 occasions, and the comparison criteria were intrasubject precision (reproducibility) and total measurement duration. RESULTS: NAA nulling is nearly twice as precise in its intrinsic back-to-back (5.8% versus 8.6%) as well as longitudinal (10.6% versus 19.7%) coefficients of variation compared with lipid nulling, but at the cost of double the acquisition time. CONCLUSION: When speed is a more stringent requirement than precision, the new lipid-nulling sequence is a viable alternative. For precision in cross-sectional or longitudinal global NAA quantification, however, NAA nulling is still the approach of choice despite its x2 (similar to 5 minutes) time penalty compared with the lipid-nulling approach
    Type of Publication: Journal article published
    PubMed ID: 18556356
    Signatur Availability
    BibTip Others were also interested in ...
  • 3
    ISSN: 1433-0407
    Keywords: Schlüsselwörter Multiple Sklerose ; Magnetresonanztomographie ; Protonenspektroskopie ; Magnetisation-Transfer ; Demyelinisierung ; Key words Magnetic resonance imaging ; Multiple sclerosis ; Proton spectroscopy ; Magnetisation transfer ; Demyelination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary We investigated a patient with secondary progressive Multiple Sclerosis during an acute relapse and after 6 months using several Magnetic Resonance methods. Conventional Magnetic Resonance images demonstrated at the time of relapse a large gadolinium enhancing lesion. Using proton spectroscopy and Magnetisation Transfer images heterogeneous changes suggestive of oedematous swelling peripherally, and active myelin destruction centrally were demonstrated in the acute phase. After clinical recovery there was marked resolution of acute inflammatory Magnetic Resonance abnormalities and recovery of MR tissue parameters. In comparison with conventional Magnetic Resonance Imaging Magnetisation Transfer Imaging and Proton Spectroscopy provide improved characterisation of pathological changes in MS.
    Notes: Zusammenfassung Wir untersuchten eine Patientin mit sekundär progressiver multipler Sklerose während eines akuten Schubes und im Verlauf nach 6 Monaten mit verschiedenen Magnetresonanztechniken. In der konventionellen Bildgebung fand sich zeitgleich zur klinischen Verschlechterung eine ausgedehnte kontrastmittelanreichernde Läsion. Mittels der Protonenspektroskopie und Magnetisation-Transfer-Bildern konnten heterogene pathologische Veränderungen mit wahrscheinlich ödematösen Gewebeveränderungen in der Peripherie und Demyelinisierung im Zentrum der Läsion in der akuten Phase dargestellt werden. Mit dem Abklingen der akuten Symptomatik zeigte sich eine Rückbildung der akut entzündlichen Aktivität und eine Erholung der MR-Gewebeparameter. Im Vergleich zur konventionellen Magnetresonanztomographie bieten Magnetisation Transfer Bildgebung und Protonen Spektroskopie spezifischere Informationen bei der Darstellung pathologischer Gewebeveränderungen der multiplen Sklerose.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 4
    ISSN: 1432-1459
    Keywords: Key words Multiple sclerosis ; Magnetisation transfer ; Gadolinium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The magnetisation transfer (MT) ratio of eight multiple sclerosis lesions has been studied serially. Initially, when the lesions showed gadolinium enhancement, there was a marked reduction in their MT ratio compared with normal white matter. Follow-up a mean of 11 months later (range 3–23 months), when the lesions no longer enhanced, revealed a consistent and usually marked recovery of the MT ratios towards normal. The MT ratio is thought to reflect the structural integrity of tissues with an important contribution from myelin and axons. MT imaging is a promising tool for elucidating pathophysiology and monitoring treatment in multiple sclerosis.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 5
    ISSN: 1432-2102
    Keywords: Schlüsselwörter Echoplanare Magnetresonanztomographie ; Schlaganfall ; Diffusion ; Bildartefakte ; Key words Echo-planar magnetic resonance imaging ; Stroke ; Diffusion ; Artifact
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Introduction: An accurate diagnosis is frequently difficult in early stroke. Diffusion-weighted (DW) magnetic resonance imaging (MRI) allows visualization of ischemic parenchyma and quantitative assessment of tissue changes before unequivocal abnormalities appear on T2-weighted MRI. Methods: We analyzed 105 MRI examinations of patients with acute stroke (〈24 h) with regard to patterns of abnormalities in T2-weighted and DW MRI. Furthermore we assessed the influence of artifacts related to DW echo-planar single-shot MRI on image interpretation. Results: Depending on the time of patient assessment there were three partly overlapping T2/DW patterns: (1) in the very early phase (≤1.5 h after symptom onset) there was no T2 abnormality and no definite abnormality of diffusion; (2) no T2 abnormality and restricted diffusion (1.5–4 h); (3) T2 hyperintensity and restricted diffusion (≥3 h). Typical artifacts (susceptibility distortions, N/2 artifact, chemical shift artifact and eddy currents artifact) had to be considered when interpreting images. Conclusions: Provided typical artifacts are taken into consideration, echo-planar DW MRI allows a more precise diagnostic assessment in acute stroke.
    Notes: Zusammenfassung In den ersten Stunden nach zerebraler Ischämie ist eine exakte Diagnosestellung häufig schwierig. Die diffusionsgewichtete (DW) Magnetresonanztomographie (MRT) ermöglicht die bildliche Darstellung betroffener Parenchymanteile und quantitative Erfassung der Gewebeveränderungen, noch bevor eindeutige Auffälligkeiten im T2-gewichteten Bild nachweisbar sind. Wir analysierten 105 MRT-Untersuchungen akuter Schlaganfälle (〈24 h) in Hinblick auf typische Befundkonstellationen in der T2- und DW MRT. Weiterhin wurde der Einfluß der bei DW echoplanarer (EP) Einzelpuls („single shot”) Meßtechniken häufig auftretenden Bildartefakte auf die Bildbefundung ausgewertet. In Abhängigkeit vom Untersuchungszeitpunkt zeigten sich drei z.T. zeitlich überlappende T2/DW Konstellationen: a) In der sehr frühen Infarktphase (≤1,5 Stunden) fehlende T2-Auffälligkeiten, bei gleichzeitig ebenfalls noch nicht nachweisbarer Diffusionsstörung; b) fehlende T2-Veränderung bei gleichzeitigen Zeichen einer reduzierten Diffusion (1,5–4 h); c) eindeutige T2-Hyperintensität bei gleichzeitig eingeschränkter Diffusion (≥3 h). Es fanden sich typische Artefakte in Form von Suszeptibilitätsverzerrungen, N/2 Artefakten, Fettsignal-(„chemical shift”)Artefakten und Wirbelstromverzerrungen, die bei der Befundinterpretation berücksichtigt werden müssen. Die Kenntnis der typischen Bildartefakte vorausgesetzt, ermöglicht EP DW-Bildgebung eine exaktere Diagnose akuter Schlaganfälle.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 6
    ISSN: 1432-1920
    Keywords: Key words Magnetic resonance imaging ; Fast spin-echo ; STIR ; Fat suppression ; Optic neuritis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Fast spin-echo (FSE) is a new sequence with acquisition times currently down to one-sixteenth of those obtained with conventional spin-echo sequences, which allows high-resolution (512 × 512 matrix) images to be acquired in an acceptable time. We compared the higher resolution of FSE with the medium resolution of a short inversion-time inversion-recovery (STIR) sequence in depicting the optic nerves of healthy controls and patients with optic neuritis. Optic nerve MRI examinations were performed in 18 patients with optic neuritis and 10 normal controls. Two sequences were obtained coronally: fat-suppressed FSE (FSE TR 3250 ms/TEef 68 ms, echo-train length 16, 4 excitations, 24 cm rectangular field of view, 3 mm interleaved contiguous slices, in-plane resolution 0.5 × 0.5 mm) and STIR (TR 2000 ms/TE 50 ms/TI 175 ms, in-plane resolution 0.8 × 0.8 mm, slice thickness 5 mm). FSE demonstrated much more anatomical detail than STIR, e. g. distinction of optic nerve and sheath. Lesions were seen in 20 of 21 symptomatic nerves using FSE and in 18 of 21 using STIR. Nerve swelling or partial cross-sectional lesions of the optic nerve were each seen only on FSE in 3 cases. Fat-suppressed FSE imaging of the optic nerve improves anatomical definition and increases lesion detection in optic neuritis.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 7
    ISSN: 1432-1920
    Keywords: Magnetic resonance imaging ; Fast spin-echo ; STIR ; Fat suppression ; Optic neuritis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Fast spin-echo (FSE) is a new sequence with acquisition times currently down to one-sixteenth of those obtained with conventional spin-echo sequences, which allows high-resolution (512×512 matrix) images to be acquired in an acceptable time. We compared the higher resolution of FSE with the medium resolution of a short inversion-time inversion-recovery (STIR) sequence in depicting the optic nerves of healthy controls and patients with optic neuritis. Optic nerve MRI examinations were performed in 18 patients with optic neuritis and 10 normal controls. Two sequences were obtained coronally: fat-suppressed FSE (FSE TR 3250 ms/TEef 68 ms, echo-train length 16, 4 excitations, 24 cm rectangular field of view, 3 mm interleaved contiguous slices, in-plane resolution 0.5×0.5 mm) and STIR (TR 2000 ms/TE 50 ms/TI 175 ms, inplane resolution 0.8×0.8 mm, slice thickness 5 mm). FSE demonstrated much more anatomical detail than STIR, e. g. distinction of optic nerve and sheath. Lesions were seen in 20 of 21 symptomatic nerves using FSE and in 18 of 21 using STIR. Nerve swelling or partial cross-sectional lesions of the optic nerve were each seen only on FSE in 3 cases. Fatsuppressed FSE imaging of the optic nerve improves anatomical definition and increases lesion detection in optic neuritis.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 8
    ISSN: 1432-1920
    Keywords: Key words Vascular dementia ; Subcortical arteriosclerotic encephalopathy ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Previous cross-sectional studies in patients with subcortical vascular encephalopathy (SVE) have shown little or no correlation between brain lesion load and clinical disability, which could be due to the low specificity of T2-weighted MRI. Recent studies have indicated that T1-weighted MRI may be more specific than T2-weighted MRI for severe tissue destruction. We studied 37 patients with a diagnosis of SVE and 11 normal controls with standardised T1- and T2-weighted MRI. All patients underwent detailed clinical assessment including a neuropsychological test battery and computerised gait analysis. Both the T2- and T1-weighted total MRI lesion loads different between patients and controls different, particularly T1. The ratio of T2-/T1-weighted lesion load was lower in controls than in patients. There was no overall correlation of T1- or T2-weighted lesion load with clinical disability, but group comparison of patients with severe and mild clinical deficits showed different lesion loads. We suggest that T1- and T2-weighted MRI lesion loads demonstrate relevant structural abnormality in patients with SVE.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 9
    ISSN: 1432-1920
    Keywords: Key words Magnetic resonance imaging ; Benign intracranial hypertension ; Papilloedema ; Optic nerve
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We investigated the MRI appearance of the optic nerve and its cerebrospinal-fluid-containing sheath in 17 patients with benign intracranial hypertension (BIH) and 15 normal controls. Using phased-array local coils, 3-mm coronal T2-weighted fat-suppressed fast spin-echo images were obtained with an in-plane resolution of 〈 0.39 mm. The optic nerve and its sheath were clearly differentiated. An enlarged, elongated subarachnoid space around the optic nerve was demonstrated in patients with BIH. High-resolution MRI of the optic nerve offers additional information which may be of value for diagnosis and in planning and monitoring treatment.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 10
    ISSN: 1432-1459
    Keywords: Key words Multiple sclerosis ; Magnetic resonance imaging ; Axonal loss ; Disability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The characteristics of transverse magnetisation decay of 120 longstanding lesions and 40 regions of normal-appearing white matter have been analysed in 40 patients with multiple sclerosis (MS) and 10 normal controls. Fifty lesions showed a biexponential decay in which two water compartments – one probably intracellular, the other extracellular – could be defined. There was a higher frequency of biexponential lesions in patients with a primary progressive course but no significant difference between benign and secondary progressive groups. Seventy lesions showed a monoexponential decay, of which 31 showed a T2 of greater than 200 ms, implying that these lesions were predominantly composed of extracellular rather than intracellular water. The results imply that an expanded extracellular space within chronic MS brain lesions is a common finding at all levels of disability and disease course. In so far as an expanded extracellular space implies axonal loss, the results suggest that the latter occurs commonly in longstanding MS lesions. The lack of correlation with disability suggests a limited role for the technique in therapeutic monitoring.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...