New x-ray tube performance in computed tomography by introducing the rotating envelope tube technology

The future demands of computed tomography imaging regarding the x-ray source can be summarized with higher scan power, shorter rotation times, shorter cool down times and smaller focal spots. We report on a new tube technology satisfying all these demands by making use of a novel cooling principle on one hand and of a novel beam control system on the other hand. Nowadays tubes use a rotating anode disk mainly cooled via radiation. The Straton x-ray tube is the first tube available for clinical routine utilizing convective cooling exclusively. It is demonstrated that this cooling principle makes large heat storage capacities of the anode disk obsolete. The unprecedented cooling rate of 4.8 MHU/min eliminates the need for waiting times due to anode cooling in clinical workflow. Moreover, an electronic beam deflection system for focal spot position and size control opens the door to advanced applications. The physical backgrounds are discussed and the technical realization is presented. From this discussion the superior suitability of this tube to withstand g-forces well above 20 g created by fast rotating gantries will become evident. Experience from a large clinical trial is reported and possible ways for future developments are discussed.     

Cytologische Kriterien der Wirkung von Sanamycin

Zusammenfassung Die cytostatische Wirkung des Sanamycin auf Milz, Thymus und Nebennieren des Kaninchens wurde mit Hilfe einer vergleichenden cyto-histologischen Untersuchungtechnik geprüft, um einen näheren Einblick in die zellspezifischen Angriffspunkte des Medikamentes zu gewinnen. Der Effekt auf die normale Lymphopoese besteht in einer zeitlich begrenzten Abnahme der reifen Lymphocyten zugunsten einer Vermehrung der Lymphoblasten, wobei histologisch eine allgemeine Reduktion der lymphatischen Gewebsanteile in Erscheinung tritt. Das RHS bleibt in diesem Zusammenhang unberührt. Die Nebennieren zeigen nach hohen Sanamycindosen Veränderungen, die einer beträchtlichen Stresswirkung oder einer reversiblen toxischen Schäidgung entsprechen können. Das durch kurzfristige Sensibilisierung stimulierte Zellsubstrat der Antikörperbildung erfährt durch Sanamycingaben eine nachhaltige Depression, während dieser Effekt bei chronisch sensibilisierten Tieren wesentlich geringer ausgeprägt ist. Die tierexperimentell erhobenen Befunde werden im Hinblick auf die therapeutische Sanamycinwirkung bei lymphatischen Systemkrankheiten und die Möglichkeiteiner Beeinflussungakuter Antigen-Antikörperreaktionen diskutiert.Herrn Professor Dr.R. Schoen zum 65. Geburtstag.     

Failure of oocyte maturation: possible mechanisms for oocyte maturation arrest

For human IVF, the patient's ovaries are hormonally stimulated to ensure the collection of fully matured oocytes that are at the metaphase II stage. Only these oocytes can be successfully fertilized either when mixed with sperm or after ICSI. Nevertheless, in some cases immature or maturing oocytes are recovered from follicles. Surprisingly, sometimes these oocytes do not complete maturation when cultured in vitro, for unknown reasons. In this article we discuss some possible mechanisms that may be responsible for those atypical arrests.     

In situ X-ray absorption spectroscopy at the K-edge of red phosphorus in polyamide 6,6 during a thermo-oxidative degradation

We present a new method for studying the influence of flame retardants as a function of time and temperature by measuring the X-ray absorption spectra of the corresponding additive. Here, red phosphorus in polyamide 6,6 was investigated at the phosphorus K-edge using synchrotron radiation. The thermo-oxidative degradation of the polymer was simulated by heating the sample up to 300°C. XANES

1 XANES, EXAFS: X-ray absorption spectroscopy investigating the near edge structure or the fine structure of the extended region, respectively.

spectra were monitored during the degradation process at different temperatures and at a constant reaction temperature as a function of time. The degradation reaction was analyzed by comparing the XANES spectra of red phosphorus and orthophosphoric acid, and the reaction was identified as an oxidation of red phosphorus to H₃PO₄. The results so obtained are confirmed by the EXAFS spectra of the additive in the polymer sample recorded before and after the thermo-oxidative degradation process, and by the EXAFS spectra of suitable reference compounds.     

Attenuation of pathological tremors by functional electrical stimulation II: Clinical evaluation

In this study we evaluated a technique for tremor suppression with functional electrical stimulation (FES), the technical details of which were described in the previous paper. Three groups of patients were investigated: those with essential tremor, parkinsonian tremor, and cerebellar tremor associated with multiple sclerosis. In each group, tremor was attenuated by significant amounts (essential tremor: 73%; parkinsonian tremor: 62%; cerebellar tremor: 38%). These attenuations were in good accord with predictions based on the dynamic analyses and filter designs derived in the previous paper. With filters “tuned” to the lower mean tremor frequency encountered in the cerebellar patients, more attenuation was possible in this group as well. We identified some practical limitations in the clinical application of the technique in its present form. The most important was that in daily use, only one antagonist pair of muscles can realistically be controlled. At first sight, this restricts the usefulness of the system to patients with single-joint tremors. However, the concomitant use of mechanical orthoses may broaden the scope of application.     

Über die jahreszeitlich bedingten änderungen der Empfindlichkeit der Froschlunge gegenüber Acetylcholin

Zusammenfassung Die Empfindlichkeit des Froschlungenpräparates, das im Winter auf Acetylcholinkonzentrationen von 110¹⁶ und darunter anspricht, nimmt in den Sommermonaten um mehrere Zehnerpotenzen ab. Da für die Verwertung des Präparates zur Bestimmung derartig kleiner A.Ch.-Konzentrationen die genaue Kenntnis dieser Empfindlichkeitsänderung notwendig ist, wurde die Umstellung des Präparates während der Monate September und Oktober durch tägliche Versuche verfolgt. Es zeigte sich, daß die Umstellung im September beginnt, besonders rasch in der zweiten Oktoberhälfte fortschreitet und Ende Oktober bereits beendet ist. Dabei steigt die Kontraktionshöhe bei der A.Ch.-Konzentration 110⁴ auf das Doppelte, bei 110¹² auf das Zehnfache. Die Konzentration 110¹⁶, die im Sommer keine sichtbare Wirkung hatte, bewirkt noch eine Verkürzung der Lungen um fast 10%. Auch die Verhältniszahlen, d. h. das Verhältnis der Kontraktionshöhe einer A.Ch.-Konzentration 110^x zur Kontraktionshöhe auf einen Prüfreiz 110⁴, die im Sommer recht niedrig lagen, wuchsen stetig an. Die ursprüngliche Größe und Konstanz der Verhältniszahlen ist im letzten Drittel des Oktober wieder erreicht.     

Die Kultur von Tuberkelbacillen aus Larynxabstrichen

Ohne Zusammenfassung     

Fast implementation of the single scatter simulation algorithm and its use in iterative image reconstruction of PET data

In positron emission tomography (PET), scatter correction is usually performed prior to image reconstruction using a more or less exact model of the scatter processes. These models require estimates of the true activity and object density distributions of the imaged object. The problem is that these estimates are computed from measured data and, therefore, already contain scattered events. The purpose of this work was to overcome this problem by incorporating scatter characteristics directly into the process of iterative image reconstruction. This could be achieved by an optimized implementation of the single scatter simulation (SSS) algorithm, which results in a significant speed-up of the scatter estimation procedure. The scatter simulation was then included in the forward projection step of maximum likelihood image reconstruction. The results demonstrate that this approach leads to a more exact estimation of the scatter component which cannot be obtained by a simple sequential data processing strategy.     

Inactivation of the peroxisomal ABCD2 transporter in the mouse leads to late-onset ataxia involving mitochondria, Golgi and endoplasmic reticulum damage

ATP-binding cassette (ABC) transporters facilitate unidirectional translocation of chemically diverse substances, ranging from peptides to lipids, across cell or organelle membranes. In peroxisomes, a subfamily of four ABC transporters (ABCD1 to ABCD4) has been related to fatty acid transport, because patients with mutations in ABCD1 (ALD gene) suffer from X-linked adrenoleukodystrophy (X-ALD), a disease characterized by an accumulation of very-long-chain fatty acids (VLCFAs). Inactivation in the mouse of the abcd1 gene leads to a late-onset neurodegenerative condition, comparable to the late-onset form of X-ALD [Pujol, A., Hindelang, C., Callizot, N., Bartsch, U., Schachner, M. and Mandel, J.L. (2002) Late onset neurological phenotype of the X-ALD gene inactivation in mice: a mouse model for adrenomyeloneuropathy. Hum. Mol. Genet., 11, 499-505.]. In the present work, we have generated and characterized a mouse deficient for abcd2, the closest paralog to abcd1. The main pathological feature in abcd2-/- mice is a late-onset cerebellar and sensory ataxia, with loss of cerebellar Purkinje cells and dorsal root ganglia cell degeneration, correlating with accumulation of VLCFAs in the latter cellular population. Axonal degeneration was present in dorsal and ventral columns in spinal cord. We have identified mitochondrial, Golgi and endoplasmic reticulum damage as the underlying pathological mechanism, thus providing evidence of a disturbed organelle cross-talk, which may be at the origin of the pathological cascade.