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  • Stereotaxic techniques  (3)
  • Electrical stimulation  (2)
  • 21.10.−K  (1)
  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Neuroradiology 28 (1986), S. 100-104 
    ISSN: 1432-1920
    Schlagwort(e): Stereotaxic techniques ; Brain imaging ; Angiography ; Radiography
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary A method for the determination of stereotaxic coordinates in radiography, e.g. angiography, pneumoencephalography or digital vascular radiography, is described. A special localization frame containing radiopaque structures and scales defines a diagnostic coordinate system. This frame is fixed to the X-ray-table prior to the radiographic procedure and two projections are obtained at arbitrary angles to each other. The focus-film distances do not how to be fixed. The target coordinates are then determined either by a simple graphical procedure or with the use of a digitizing x-y-table, by a computer. With the computer method the films are placed on the digitizing table and the target and a few reference points are marked using a cursor. From the relative positions the computer calculates the coordinates. With the special head fixation system, coordinates of structures visualized in radiographic examinations can be transferred to various therapeutic or diagnostic stereotaxic devices.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    ISSN: 1432-1920
    Schlagwort(e): Computed tomography, head ; Stereotaxic techniques ; Head fixation system
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Neuroradiology 29 (1987), S. 585-587 
    ISSN: 1432-1920
    Schlagwort(e): Stereotaxic techniques ; Digital radiography ; Leksell instrument
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    Pflügers Archiv 417 (1990), S. 136-141 
    ISSN: 1432-2013
    Schlagwort(e): Electrical stimulation ; Fatigue ; Force ; Frequency ; Skeletal muscle
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Pflügers Archiv 418 (1991), S. 153-160 
    ISSN: 1432-2013
    Schlagwort(e): ATP ; Electrical stimulation ; Force ; Phosphate ; Phosphocreatine ; Relaxation ; Skeletal muscle
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 6
    ISSN: 1434-601X
    Schlagwort(e): 21.10.−K ; 21.60.−n ; 25.70.−z ; 27.70.+q
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The strongly shape driving πh9/2[541]l/2− configuration with α=+1/2 exhibits some anomalous, and so far unexplained, features concerning the crossing frequency, ħωc, the aligned angular momentum, ix, and interaction strength, at the alignment of the first pair of i13/2 quasineutrons in several odd-Z rare earth-nuclei. The h9/2[541]1/2− and h11/2[523]7/2− bands have been studied in the stably deformed rare-earth nucleus163Tm to investigate these features. A difference in band crossing frequency of ∼ 80 keV between the two bands is found. Rotational bands built on these two configurations have been found to cross in the spin range I=25/2–29/2 ħ. Theγ-decay pattern between the two bands is established in the crossing region and analysed in terms of a moderate shape difference between them. A theoretical estimate of the size of the interaction strength between the two bands is presented and compared to the experimental value. The observed band structure in163Tm is very similar to that of167Lu which has 2 protons and 2 neutrons in addition. This observation is discussed in relation to the similarity of the yrast bands of the two even-even “core” nuclei162Er and166Yb, for which theγ-transition energies are identical within ∼0.2 keV below the vi13/2 crossing.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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