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  • 11
    Electronic Resource
    Electronic Resource
    Springer
    Neuroradiology 29 (1987), S. 585-587 
    ISSN: 1432-1920
    Keywords: Stereotaxic techniques ; Digital radiography ; Leksell instrument
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Special perspex adaptors with radiopaque reference structures have been constructed to fit to the Leksell stereotaxic instrument. These structures are visualized on X-ray film in a radiographic examination like angiography or encephalography. The films obtained in two projections at arbitrary angles and focus-film-distances are placed on a digitizing table for the determination of the stereotaxic coordinates of selected targets. The reference structures and the targets are marked with a cursor whereupon a desk top computer performs the calculation of the stereotaxic coordinates. The system allows a rapid, simple and accurate coordinate determination in stereotaxic radiography using the Leksell stereotaxic instrument.
    Type of Medium: Electronic Resource
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  • 12
    Electronic Resource
    Electronic Resource
    Springer
    Neuroradiology 17 (1978), S. 31-33 
    ISSN: 1432-1920
    Keywords: Computed tomography ; Contrast medium enhancement ; Acoustic neuroma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The changes of the enhancement of the lesion with time after intravenous administration of contrast medium were measured with computed tomography (CT) in 23 cases of acoustic neuroma. The pattern of high initial enhancement followed by a fairly rapid decrease is confirmed. A more rigorous study of the enhancement pattern using a mathematical description of the enhancement curve of the tumor as well as a measurement of the individual blood enhancement curve is discussed.
    Type of Medium: Electronic Resource
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  • 13
    ISSN: 1432-1920
    Keywords: Computed tomography, head ; Stereotaxic techniques ; Head fixation system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A head fixation system is described enabling exact transfer of positions between neuroradiological and therapeutic procedures. The key item of the system is a base plate that is rigidly attached to the patient's head, either by a plastic mould or screws onto the calvarium. The base plate may easily and accurately be attached to diagnostic or therapeutic units. Coordinates of target points in the various units are directly related through the exact application of the base plate. Procedures for the exact comparison of spatial information have been worked out. The system has been used for diagnostic procedures such as plain skull radiography, cerebral angiography, CT scanning, positron emission tomography, and gamma camera examinations, as well as for therapeutic procedures such as stereotaxic biopsy and radiation treatment.
    Type of Medium: Electronic Resource
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  • 14
    Electronic Resource
    Electronic Resource
    Springer
    Pflügers Archiv 418 (1991), S. 153-160 
    ISSN: 1432-2013
    Keywords: ATP ; Electrical stimulation ; Force ; Phosphate ; Phosphocreatine ; Relaxation ; Skeletal muscle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Force and relaxation were measured during electrical stimulation of the quadriceps muscle of 14 volunteers. Stimulation produced 51.2 s of intermittent ischaemic contractions either as 16 3.2-s tetani or as 64 0.8-s tetani. Changes during recovery were followed for 180 s. On 8 subjects muscle biopsies were taken during work and after the rest period for determination of ATP, phosphocreatine and intermediates in glucolysis. The stimulation using 0.8-s contractions gave more pronounced fatigue and slowing of relaxation. There was a good correlation between force and relaxation during work but this relation changed during recovery, indicating that no general relation exists between these two contraction characteristics. In the 0.8-s stimulation more ATP was utilized and there were more profound changes in metabolite levels. We found a correlation between estimated [H2PO 4 − ] and relaxation covering both work and recovery and hypothesize that inorganic phosphate and its removal by phosphocreatine resynthesis during recovery might be important. Since stimulation patterns differ in force and relaxation even after the recovery period we suggest that additional factors, such as pH, are of importance in this work model.
    Type of Medium: Electronic Resource
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  • 15
    Electronic Resource
    Electronic Resource
    Springer
    Pflügers Archiv 417 (1990), S. 136-141 
    ISSN: 1432-2013
    Keywords: Electrical stimulation ; Fatigue ; Force ; Frequency ; Skeletal muscle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Percutaneous electrical stimulation was used to study the force response of the quadriceps muscle. The normal frequency dependence of force was investigated in muscles at rest and after fatiguing contractions. A comparison between force response during fatigue induced by electrical stimulation at different frequencies and by voluntary work suggested equal changes in contractility, irrespective of the fatigue-inducing procedure. In fresh muscle we found a linear relation between stimulation period (10–100 ms) and force. At fatigue the relation changes with maximal deviation from linearity at a 50-ms period (20 Hz). There is a rapid recovery of high frequency force whereas the low frequency response remains low even after 30 min rest. At very low frequencies there is initially unexpectedly high force in fatigued muscle. This could be a result of increased fusion of twitches with initially prolonged relaxation time. To study the twitch summation we compared experimental results in a wide frequency range with computer-simulated twitch summations and present the frequency dependence of summation processes in human quadriceps muscle.
    Type of Medium: Electronic Resource
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  • 16
    Electronic Resource
    Electronic Resource
    Springer
    Neuroradiology 15 (1978), S. 165-166 
    ISSN: 1432-1920
    Keywords: Computed tomography ; Cerebrospinal fluid ; Attenuation value
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The attenuation value of CSF, obtained by lumbar puncture, was determined with computed tomography in 25 patients. Measurement of the protein content in the same samples showed no correlation with the attenuation value. It is concluded that in the normal range of protein concentrations, the effect on the attenuation is insignificant and that the attenuation value of the CSF might be used to check large deviations in the CT numbers due to artifacts.
    Type of Medium: Electronic Resource
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  • 17
    Electronic Resource
    Electronic Resource
    Springer
    Neuroradiology 18 (1979), S. 249-258 
    ISSN: 1432-1920
    Keywords: Computed tomography, head ; Pituitary gland, neoplasms ; Sella turcica, anatomy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Suspected lesions in and around the sella were examined by CT in 129 cases. The diagnostic accuracy and various technical aspects of the method are described. The mean attenuation and enhancement after administration of contrast material are evaluated in craniopharyngiomas, chromophobe adenomas, meningiomas, aneurysms, dermoid cysts, an arachnoid cyst and a glioma. The choice of collimator and its use in relation to sellar dimensions, particularly the sellar depths, are emphasized.
    Type of Medium: Electronic Resource
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  • 18
    ISSN: 1432-1920
    Keywords: Computed tomography, brain ; Contrast material ; Cerebrospinal fluid ; Cerebral ventricles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The CT attenuation change of the intraventricular CSF after i. v. administration of contrast material has been studied in 20 patients. A very small increase of attenuation was observed in the entire material. The method does not seem to be appropriate at present for the study of small attenuation changes in the CSF reflecting the passage of contrast material.
    Type of Medium: Electronic Resource
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  • 19
    Electronic Resource
    Electronic Resource
    Springer
    Neuroradiology 19 (1980), S. 123-129 
    ISSN: 1432-1920
    Keywords: Computed tomography ; Acoustic neuroma ; Internal auditory meatus ; Attenuation profiles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Attenuation profiles across the petrous bone covering the whole internal auditory meatus (IAM) were constructed from the printouts obtained by computed tomography (CT) with narrow collimation performed on 12 patients with 13 acoustic neuromas. In healthy patients the attenuation profiles of right and left petrous bone were very similar in shape. The attenuation values of the individual pixels in the pixel columns of the printout located at the site of the porus and the IAM reflected the demineralization of the petrous bone and the widening of the porus and the IAM caused by the acoustic neuroma. A widening deep in the meatus was demonstrated in a patient with an intracanalicular tumor, and therefore it seems possible to make this diagnosis by CT scanning combined with the construction of attenuation profiles across the petrous bone. In the presence of unilateral acoustic neuroma there was a significant and characteristic difference in shape between the attenuation profiles of the two sides with generally lower attenuation values on the tumor side together with signs of widening of the porus and the IAM. In cases of bilateral acoustic neuroma comparison of the attenuation profiles can be made with mean attenuation curves obtained from scanning normal petrous bones. The prevailing physical limitations for demonstrating a narrow bony canal like the IAM with CT was experimentally analyzed using bone-simulating plastic material.
    Type of Medium: Electronic Resource
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  • 20
    Electronic Resource
    Electronic Resource
    Springer
    Neuroradiology 19 (1980), S. 7-12 
    ISSN: 1432-1920
    Keywords: Computed tomography ; Stereotactic techniques
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Two head-fixation systems, one using Thermoplast and the other Lightcast were tested as to reproducibility by comparing stereotactic coordinates before and after CT scan and after removal and reapplication of the helmets. Helmets constructed of Lightcast were more consistently stable than those constructed of Thermoplast probably due in part to the dental fixation used with the former. With Lightcast the change in position of coordinates was consistently less than 3 mm, i.e. 2 pixels, which is within the tolerance of the system as a whole.
    Type of Medium: Electronic Resource
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