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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Neurosurgical review 8 (1985), S. 141-150 
    ISSN: 1437-2320
    Keywords: Magnetic resonance ; neoplasms ; perisellar lesions ; pituitary
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Nuclear magnetic resonance (NMR) imaging is a versatile technique which has proved more sensitive in the detection of perisellar lesions than CT. A multiplanar facility, the demonstration of blood flow, and the lack of bone artefacts are its main advantages in this respect. Limitations are seen in its inability to identify small calcifications and to distinguish clearly perifocal oedema and tumour especially in malignant lesions. Relatively thick slices of 5–10 mm make the detection of microadenomas very difficult, mainly because of partial volume effects. T1 and T2 values alone are not sufficient to provide specific diagnosis. No reliable criteria have been determined yet, which would indicate the quality of pathological involvement of peritumorous structures by tumours of the sella region. At present NMR still plays a more complementary role to CT in the evaluation of this complex anatomical area. We are confident that with future technical refinements NMR will be able to replace ionizing radiation for the diagnostic imaging of the sella.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1437-2320
    Keywords: CNS ; imaging techniques ; MRI ; tissue contrast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Magnetic resonance imaging (MRI) has undergone a rapid development which is still continuing. In this article a survey is given of the present status of this new diagnostic tool in the evaluation of diseases of the central nervous system. When atoms with uneven numbers of protons or neutrons in a homogeneous magnetic field are tilted against the main vector of this field by a radiofrequency pulse, nuclear magnetic resonance can be observed. During the relaxation of the little dipoles back to the direction of the underlying magnetic field, a resonance signal is generated. The superposition of variable field gradients enables the scanning of sectional images in the axial, frontal and sagittal plane. The variables of H+-magnetic resonance which can be utilized for imaging are: the proton density, the relaxation times T1 (spin-lattice) and T2 (spin-spin) and flow effects. While the proton density in organic tissue fluctuates only by some 10%, the relaxation times may vary by several hundred per cent. Tissue contrast, therefore, is mainly based on relaxation times differences. The image character can also be influenced by variations of imaging parameters (i.e. repetition rate, interpulse delay, read out or echo delay) in different imaging sequences, such as the spin-echo and the inversion recovery technique. Depending on these imaging parameters T1 and T2 will contribute to the signal to a varying degree. This fact is most important for the diagnostic information of MRI. In initial clinical experiences in the diagnosis of diseases of the central nervous system, MRI has demonstrated high sensitivity in the detection of lesions (such as oedema, neoplasms, demyelinating disease), but less significance in lesion discrimination. In spinal disease the direct sagittal imaging of MRI enables MRI-myelography without contrast medium, superior to conventional myelography in many cases. For detailed evaluation of disc disease, however, the spatial resolution still has to be improved. Promising results have been obtained from flow effects. Depending on the flow velocity of blood, vessels appear white with intensive signals (slow flow) or black due to low signal intensities (rapid flow). MRI-angiography including measurement of blood flow seems possible. MRI-contrast media are not yet available for routine clinical use. Promising results have been reported on the basis of rare-earth elements, such as gadolinium Gd3+. These substances decrease T1 and T2 with subsequent increase in signal intensity. Concerning harmful side-effects of MRI, three possible sources have to be considered: the static magnetic field, the changing magnetic field, and radiofrequency heating. No permanent damage to organisms has been described up to the present time, in relation to the magnetic field strength used in MRI. However, there is known risk for patients who carry cardiac pace makers or metal implants such as aneurysm clips.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1439-099X
    Keywords: Key Words: Low-grade glioma ; Radiotherapy ; Prognostic factors ; Schlüsselwörter: Niedriggradige Gliome ; Radiotherapie ; Prognosefaktoren
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Hintergrund: Es sollten Ergebnisse und Prognosefaktoren nach postoperativer Radiotherapie bei 77 Patienten mit Low-grade-Gliomen evaluiert werden. Patienten und Methoden: Zwischen 1977 und 1996 wurden 45 Patienten mit einem Low-grade-Astrozytom, 14 mit einem Oligodendrogliom und 18 mit einem gemischten Gliom postoperativ bis zu einer medianen Gesamtdosis von 52 Gy bestrahlt (Spanne zwischen 45 und 61 Gy). 67 Patienten wurden unmittelbar postoperativ, zehn Patienten erst nach computertomographischer Progression bestrahlt. Der Einfluss verschiedener Faktoren einschließlich Histologie, Geschlecht, Alter, Anfallsleiden, Dauer der Symptome vor Therapiebeginn (≤ 6 Wochen gegenüber 〉 6 Wochen), CT-Befunde (Kontrastmittelaufnahme vs. keine Aufnahme), Art der Operation, Gesamtdosis der Radiotherapie und Zeitpunkt der Radiotherapie für die Endpunkte progressions- oder rezidivfreies Überleben und Gesamtüberleben wurde untersucht. Ergebnisse: Das mediane Gesamtüberleben betrug 81 Monate, die Fünf- und Zehn-Jahres-Überlebensraten waren 54 und 31%. Die mediane Zeit bis zur Progression betrug 56 Monate, während die progressionsfreien Fünf- und Zehn-Jahres-Überlebensraten bei 45 und 27% lagen. In univariaten Analysen wurden die Gesamtdosis der Radiotherapie (p = 0,01), die Dauer der Symptome (p = 0,05), das Vorhandensein von Anfällen (p = 0,04) und die Kontrastmittelaufnahme im prätherapeutischen CT (p = 0,005) als signifikante Prognosefaktoren für das Gesamtüberleben identifiziert. Die progressionsfreie Überlebensrate wurde durch die Gesamtdosis der Radiotherapie (p = 0,04), die Dauer der Symtpomatik (p = 0,01) und die Kontrastmittelaufnahme im CT (p = 0,006) beeinflusst. In der multivariaten Analyse blieb lediglich das Kontrastmittelverhalten im CT (Aufnahme vs. keine Aufnahme) als unabhängige Prognosefaktoren für das Gesamtüberleben und das rezidivfreie Überleben übrig. Schlussfolgerung: Eine minimale Gesamtdosis von 52 Gy ist im Rahmen der postoperativen Radiotherapie von Low-grade-Gliomen empfohlen. Tumoren mit einer Kontrastmittelaufnahme im CT scheinen eine weitere Intensivierung der Therapie zu benötigen.
    Notes: Background and Purpose: To assess treatment outcome and prognostic factors following postoperative external radiotherapy in 77 patients with low-grade glioma. Patients and Methods: Between 1977 and 1996, 45 patients with astrocytoma, 14 with oligodendroglioma and 18 with mixed glioma received postoperative radiotherapy with a median total dose of 52 Gy (range, 45 to 61 Gy). Sixty-seven patients were treated immediately following surgery, 10 patients with tumor progression. The influence of various factors including histology, gender, age, seizures, duration of symptoms (≤ 6 weeks vs 〉 6 weeks), CT pattern (enhancement vs no enhancement), type of surgery, total radiotherapy dose and timing of radiotherapy on relapse-free survival and overall survival was investigated. Results: The median overall survival time was 81 month, the 5- and 10-year survival rates were 54% and 31%, respectively. The median time to progression was 56 months, while the 5- and 10-year progression-free survival rates were 45% and 24%. Univariate analyses identified the total radiotherapy dose (p = 0.01), duration of symptoms (p = 0.05), the presence of seizures (p = 0.04), and the CT pattern following intravenous contrast (p = 0.005) as significant prognostic factors for overall survival. Progression-free survival rates were influenced by the total dose (p = 0.04), the duration of symptoms (p = 0.01) and CT pattern (p = 0.006). On multivariate analysis, only the CT pattern (enhancement vs no enhancement) remained as independent prognostic factors for both progression-free survival and overall survival. Conclusion: A minimum total dose of 52 Gy is recommended for the postoperative radiotherapy in low-grade glioma. Tumors with CT enhancement seem to need further intensification of treatment.
    Type of Medium: Electronic Resource
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