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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 25 (1978), S. 197-201 
    ISSN: 1432-0827
    Keywords: Metacarpals ; Bone morphometry ; Twins ; Osteoporosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary The relative importance of genetic factors in the pathogenesis of age related bone loss has been investigated in a study involving 17 monozygotic (MZ) and 8 dizygotic (DZ) pairs of twins aged 64 to 75 years. Radiographic morphometry was performed at the midpoints of the 2nd, 3rd and 4th metacarpals of both hands and the mean total and cortical widths were evaluated. The heritability, h2, was calculated as the difference between the intrapair variances in same sexed DZ and MZ pairs divided by the intrapair variance in DZ pairs. The mean intrapair variance of both total and cortical width was found to be four to five times higher in DZ than in MZ pairs. The differences are highly significant with an h2 value between 0.7 and 0.8, indicating a predominant genetic influence. It is stressed that this result applies only to the population from which the twin sample was drawn.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 35 (1983), S. 135-144 
    ISSN: 1432-0827
    Keywords: Total body calcium ; Neutron activation analysis ; Femur ; Radius ; Ulna ; Densitometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary In a heterogeneous group of 12 male and 30 female patients, total body calcium (TBCa) was measured by neutron activation analysis, and bone mineral content of the distal femur and six regions of the distal radius and ulna were measured by photon absorptiometry. TBCa was an average of 71 g (9%) lower than normal in the females and 119 g (11%) lower than normal in the males. Of the forearm measurements, those of the radial shaft provided the best estimate of TBCa with a standard error of estimation (SEE) of 88 g (14% of the mean value) for female patients alone, and 113 g (16%) for the whole group. The measurement on the femur provided a better estimate with SEE 80 g (13%) for female patients and 90 g (13%) for the whole group. These SEE are comparable with the variability in TBCa between normal subjects, which has a coefficient of variation of the order of 20% in both sexes. A slightly better estimate of TBCa can be obtained by using a multiple regression equation involving both the femur and radial shaft measurements with a SEE of 74 g (12%) for female patients and 81 g (11%) for the whole group. The correlation between the estimated deficit of TBCa and the estimated deficit of bone mineral from the forearm and the femur has been calculated.
    Type of Medium: Electronic Resource
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  • 3
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    Oxford : Periodicals Archive Online (PAO)
    Cambridge journal of economics. 3:2 (1979:June) 165 
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 10 (1972), S. 289-301 
    ISSN: 1432-0827
    Keywords: Metacarpal ; Morphometry ; Density ; Bone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé Les longueurs, les volumes extérieurs et les poids de 45 seconds métacarpes, déssèchés et nettoyés, sont déterminés. Les largeurs totales et médullaires de la diaphyse sont mesurées sur des radiographies antéro-postérieurs. le volume cortical, le volume externe et le poids de cendres de la diaphyse, d'une longueur de 1 cm, sont aussi déterminés. A partir des mesures morphométriques, les estimations des propriétés géométriques et densitométriques de la diaphyse et de l'os total sont analysées. Quelques estimations des propriétés géométriques ont pu être étudiées en estiamnt que la diaphyse du métacarpe est un cylindre. Les rapports entre les estimations et les propriétés géométriques et densitométriques sont envisagés et l'exactitude d'un modèle cylindrique est évaluée.
    Abstract: Zusammenfassung Länge, äußerer Umfang und Gewicht von 45 sauberen, trockenen zweiten Metacarpalknochen wurden bestimmt. Die totale Breite und die Markhöhlenbreite des mittleren Schaftes wurden mit posterior-anterioren Röntgenaufnahmen gemessen. Corticaler und äußerer Umfang und Aschgewicht eines 1 cm langen Stückes vom Schaft jedes Knochens wurden ebenfalls gemessen. Mittels morphometrischer Messungen wurden Schätzungen der geometrischen und densitometrischen Eigenschaften der Mittelschaftregion und des ganzen Knochens berechnet. Einige Schätzungen der geometrischen Eigenschaften wurden abgeleitet unter der Annahme, daß der metacarpale Schaft ein Zylinder ist. Die Beziehungen zwischen den Schätzungen und den geometrischen und densitometrischen Eigenschaften selbst wurden untersucht, und die Gültigkeit des Zylindermodelles wurde geprüft.
    Notes: Abstract The lengths, external volumes and weights of 45 clean, dry, second metacarpals were determined. The midshaft total and medullary widths were measured on postero-anterior radiographs. The cortical volume, external volume and ash weight of a 1 cm length of the shaft of each bone were also measured. From the morphometric measurements estimators of the geometric and densitometric properties of the midshaft section and of the whole bone were computed. Some estimators of the geometric properties were derived on the assumption that the metacarpal shaft is a cylinder. The relationships between the estimators and the geometric and densitometric properties themselves were examined and the validity of the cylinder model was explored.
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  • 5
    ISSN: 1432-0827
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Magnetic resonance materials in physics, biology and medicine 2 (1994), S. 361-363 
    ISSN: 1352-8661
    Keywords: proton MRS ; quantitation ; choline ; T 2 relaxation ; meningioma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics
    Notes: Abstract Quantitative proton spectroscopy was performed on 26 volunteers and 9 patients using STEAM. Voxels (8 ml) were localized within white matter or meningioma and water-suppressed spectra acquired with TR=2 s at three echo times. Concentrations were calculated using individual relaxation parameter values with tissue water as an internal reference. Compared to white matter, meningiomas were characterized by an increased choline/creatine ratio, the absence ofN-acetylasparate, and the presence of alanine. Further, theT 2 of choline and its concentration were both significantly greater in meningiomas than white matter (p〈0.01). Thus, the high choline/creatine ratio seen in meningioma spectra is the consequence of a greater concentration and a longerT 2. The longerT 2 may reflect differences in the relative proportions of choline-containing compounds. Our data demonstrate that individual measurements of relaxation parameters are important for long echo spectra and may reveal important metabolic information.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Magnetic resonance materials in physics, biology and medicine 2 (1994), S. 413-416 
    ISSN: 1352-8661
    Keywords: dynamic MRI ; simplex minimization ; nonlinear least squares ; breast neoplasm
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics
    Notes: Abstract The introduction of fast clinical imaging techniques enables the dynamic sampling of contrast agent kinetics. The quantity of data generated by such techniques demands the application of automated analysis tools to provide objective assessments of contrast washin/washout characteristics across an entire image. Using a simple compartmental model, the washin/washout characteristics may be defined in terms of a biexponential function. Curve fitting to this nonlinear function may be approached using a nonlinear least squares technique. We demonstrate an alternative technique, simplex minimization, to be more robust in a comparative study using Monte Carlo simulation. The application of the technique is illustrated by pixel-by-pixel analysis of dynamic data obtained from a patient with primary carcinoma of the breast.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Magnetic resonance materials in physics, biology and medicine 2 (1994), S. 357-359 
    ISSN: 1352-8661
    Keywords: proton MRS ; N-acetylaspartate ; Huntington's disease
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics
    Notes: Abstract We studied six patients in the early stage of Huntington's disease, together with six unaffected normal subjects. Localized spectra were acquired from 4-ml voxels encompassing the combined putamen and caudate head using STEAM with TR=1 s and TE=40 ms. Metabolite concentrations were calculated using tissue water as an internal reference. Although MRI showed minor degenerative changes in the basal ganglia, we were unable to detect any differences in the neuronal marker,N-acetylaspartate, between the two groups (patient mean ± SD, 10.7±2.1 µmol g wet wt−1; controls 11.4±1.3). Similarly, we were unable to detect differences in either choline or creatine. In contrast to other studies, we were unable to detect any increase in lactate content of the basal ganglia in these patients with early stage disease. We conclude that proton MR spectroscopy will not be a suitable technique to detect the very early changes in asymptomatic patients identified as having the mutation.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Magnetic resonance materials in physics, biology and medicine 2 (1994), S. 461-465 
    ISSN: 1352-8661
    Keywords: angiography ; finger ; high resolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics
    Notes: Abstract The limits of the spatial resolution achievable on a standard GE Signa 1.5-T imaging machine have been explored by interfacing a 12-cm-diameter local gradient set to such a system. Using a range of purpose-built radio-frequency (RF) coils, 3D gradient echo images with a spatial resolution of 100×100×500 µ have been routinely obtained on the finger. Also produced were 100×200×500 µ, resolution angiograms of the finger detailing submillimeter vessels, with a velocity encoding of 6 cm s−1. High-resolution fat/water suppressed images and isotropic data sets with a resolution of 170 µ are also demonstrated. With regard to the investigation of the mechanics of the human finger, isotropic data sets are desirable if accurate segmentation is to be implemented. A preliminary study illustrating the potential for producing a magnetic-resonance-based computer simulation of the mechanics of the human finger shows the distal interphalangeal joint extended and then in flexion.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Magnetic resonance materials in physics, biology and medicine 2 (1994), S. 483-485 
    ISSN: 1352-8661
    Keywords: proton MRS ; quantitation ; citrate ; prostate ; heterogeneity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics
    Notes: Abstract Water-suppressed proton spectra of the two major anatomical regions of the normal prostate were acquired with a commercial phased-array multicoil. The spectra demonstrated excellent signal-to-noise ratio and spectral resolution allowing identification of peaks from choline, creatine, and amino acids, as well as a major peak from citrate. Quantification of the citrate peak using tissue water as an internal concentration reference revealed a marked variability among different volunteers. In each case, citrate was consistently twofold to threefold greater in the peripheral zone than in the central gland. The results demonstrate heterogeneity of citrate within the prostate and suggest significant differences in the cytology and hormonal control of citrate synthesis among individuals.
    Type of Medium: Electronic Resource
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