Incidental Findings of Gallbladder and Bile Ducts-Management Strategies: General Aspects, Gallbladder Polyps and Gallbladder Wall Thickening-A World Federation of Ultrasound in Medicine and Biology (WFUMB) Position Paper

The World Federation of Ultrasound in Medicine and Biology (WFUMB) is addressing the issue of incidental findings with a series of position papers to give advice on characterization and management. The biliary system (gallbladder and biliary tree) is the third most frequent site for incidental findings. This first part of the position paper on incidental findings of the biliary system is related to general aspects, gallbladder polyps and other incidental findings of the gallbladder wall. Available evidence on prevalence, diagnostic work-up, malignancy risk, follow-up and treatment is summarized with a special focus on ultrasound techniques. Multiparametric ultrasound features of gallbladder polyps and other incidentally detected gallbladder wall pathologies are described, and their inclusion in assessment of malignancy risk and decision- making on further management is suggested.

Gelation Dynamics upon Pressure-Induced Liquid-Liquid Phase Separation in a Water-Lysozyme Solution

Employing X-ray photon correlation spectroscopy, we measure the kinetics and dynamics of a pressure-induced liquid-liquid phase separation (LLPS) in a water-lysozyme solution. Scattering invariants and kinetic information provide evidence that the system reaches the phase boundary upon pressure-induced LLPS with no sign of arrest. The coarsening slows down with increasing quench depths. The g₂ functions display a two-step decay with a gradually increasing nonergodicity parameter typical for gelation. We observe fast superdiffusive (γ ≥ 3/2) and slow subdiffusive (γ < 0.6) motion associated with fast viscoelastic fluctuations of the network and a slow viscous coarsening process, respectively. The dynamics age linearly with time τ ∝ t_w, and we observe the onset of viscoelastic relaxation for deeper quenches. Our results suggest that the protein solution gels upon reaching the phase boundary.

[Cholecystectomy in acute cholecystitis-a surgical emergency or elective in the next day's program?]

BACKGROUND

The treatment of acute cholecystitis is based on the German S3 guidelines on "Prophylaxis, diagnosis and treatment of gallstones", which was updated in 2018. If the patient has no contraindications for surgery, early laparoscopic cholecystectomy is the treatment of choice.

OBJECTIVE

Current meta-analyses and studies confirm that for most patients the optimal period of time for surgical treatment is the first 24 h after hospitalization; however, there is an ongoing controversial discussion on how strictly the 24 h rule should be adhered to and under which circumstances it may be valid to deviate from it.

MATERIAL AND METHOD

A systematic analysis of the current literature and a clinical evaluation were carried out.

RESULTS

For the diagnosis of an acute cholecystitis, laparoscopic cholecystectomy should be carried out within the first 24 h after hospitalization regardless of the age and comorbidities of the patient as well as the severity of inflammation. If there is no special emergency situation, under certain circumstances surgery can be performed in the next day's program.

DISCUSSION

This recommendation for early surgery for high-risk patients has so far been controversially discussed; however, current studies confirm that the advantages of early surgery outweigh the disadvantages also for this group of patients. The surgical risk should be individually assessed and be included in the treatment decision.

The Treatment of Gallstone Disease

BACKGROUND

Gallstone disease affects up to 20% of the European population, and cholelithiasis is the most common reason for hospitalization in gastroenterology.

METHODS

This review is based on pertinent publications retrieved by a selective search of the literature, including the German clinical practice guidelines on the diagnosis and treatment of gallstones and corresponding guidelines from abroad.

RESULTS

Regular physical activity and an appropriate diet are the most important measures for the prevention of gallstone disease. Transcutaneous ultrasonography is the paramount method of diagnosing gallstones. Endoscopic retrograde cholangiography should only be carried out as part of a planned therapeutic intervention; endosonography beforehand lessens the number of endoscopic retrograde cholangiographies that need to be performed. Cholecystectomy is indicated for patients with symptomatic gallstones or sludge. This should be performed laparoscopically with a four-trocar technique, if possible. Routine perioperative antibiotic prophylaxis is not necessary. Cholecystectomy can be performed in any trimester of pregnancy, if urgently indicated. Acute cholecystitis is an indication for early laparoscopic cholecystectomy within 24 hours of admission to hospital. After successful endoscopic clearance of the biliary pathway, patients who also have cholelithiasis should undergo laparoscopic cholecystectomy within 72 hours.

CONCLUSION

The timing of treatment for gallstone disease is an essential determinant of therapeutic success.

Wave-Vector Dependence of the Dynamics in Supercooled Metallic Liquids

We present a detailed investigation of the wave-vector dependence of collective atomic motion in Au_{49}Cu_{26.9}Si_{16.3}Ag_{5.5}Pd_{2.3} and Pd_{42.5}Cu_{27}Ni_{9.5}P_{21} supercooled liquids close to the glass transition temperature. Using x-ray photon correlation spectroscopy in a previously uncovered spatial range of only a few interatomic distances, we show that the microscopic structural relaxation process mimics the structure and presents a marked slowing down at the main average interparticle distance. This behavior is accompanied by dramatic changes in the shape of the intermediate scattering functions, which suggest the presence of large dynamical heterogeneities at length scales corresponding to a few particle diameters. A ballisticlike mechanism of particle motion seems to govern the structural relaxation of the two systems in the highly viscous phase, likely associated with hopping of caged particles in agreement with theoretical studies.

[Prophylaxis, Diagnosis and Treatment of Gallstones - The Most Important Facts of the Updated S3-Guideline of the DGVS and DGAV]

This short version of the guideline summarizes the evidence-based key recommendations for the prevention, diagnosis and therapy of gallstones and upgrades the 2007 version. The guideline used structural S3 consensus-based methodology and includes statements on clinical management and prevention, medical education, and quality assurance.

[Updated S3-Guideline for Prophylaxis, Diagnosis and Treatment of Gallstones. German Society for Digestive and Metabolic Diseases (DGVS) and German Society for Surgery of the Alimentary Tract (DGAV) - AWMF Registry 021/008]

This guideline provides evidence-based key recommendations for the prevention, diagnosis and therapy of gallstones and upgrades the 2007 version. The guideline was developed by an interdisciplinary team of gastroenterologists and surgeons, and patient support groups under the auspice of the German Society for Gastroenterology and Metabolic Diseases and the German Society for General Surgery and Surgery of the Alimentary Tract. The guideline used structural S3 consensus-based methodology and includes statements on clinical practice, medical education, prevention, quality assurance, outcome analysis, and integration of outpatient and inpatient care for patients with gallstone diseases.

Probing ultrafast changes of spin and charge density profiles with resonant XUV magnetic reflectivity at the free-electron laser FERMI

We report the results of resonant magnetic XUV reflectivity experiments performed at the XUV free-electron laser FERMI. Circularly polarized XUV light with the photon energy tuned to the Fe M_2,3 edge is used to measure resonant magnetic reflectivities and the corresponding Q-resolved asymmetry of a Permalloy/Ta/Permalloy trilayer film. The asymmetry exhibits ultrafast changes on 240 fs time scales upon pumping with ultrashort IR laser pulses. Depending on the value of the wavevector transfer Q_z , we observe both decreasing and increasing values of the asymmetry parameter, which is attributed to ultrafast changes in the vertical spin and charge density profiles of the trilayer film.

Model-independent particle species disentanglement by X-ray cross-correlation scattering

Mixtures of different particle species are often investigated using the angular averages of the scattered X-ray intensity. The number of species is deduced by singular value decomposition methods. The full disentanglement of the data into per-species contributions requires additional knowledge about the system under investigation. We propose to exploit higher-order angular X-ray intensity correlations with a new computational protocol, which we apply to synchrotron data from two-species mixtures of two-dimensional static test nanoparticles. Without any other information besides the correlations, we demonstrate the assessment of particle species concentrations in the measured data sets, as well as the full ab initio reconstruction of both particle structures. The concept extends straightforwardly to more species and to the three-dimensional case, whereby the practical application will require the measurements to be performed at an X-ray free electron laser.

Colloidal crystallite suspensions studied by high pressure small angle x-ray scattering

We report on high pressure small angle x-ray scattering on suspensions of colloidal crystallites in water. The crystallites made out of charge-stabilized poly-acrylate particles exhibit a complex pressure dependence which is based on the specific pressure properties of the suspending medium water. The dominant effect is a compression of the crystallites caused by the compression of the water. In addition, we find indications that also the electrostatic properties of the system, i.e. the particle charge and the dissociation of ions, might play a role for the pressure dependence of the samples. The data further suggest that crystallites in a metastable state induced by shear-induced melting can relax to a similar structural state upon the application of pressure and dilution with water. X-ray cross correlation analysis of the two-dimensional scattering patterns indicates a pressure-dependent increase of the orientational order of the crystallites correlated with growth of these in the suspension. This study underlines the potential of pressure as a very relevant parameter to understand colloidal crystallite systems in aqueous suspension.

Correlated heterogeneous dynamics in glass-forming polymers

We report x-ray photon correlation spectroscopy experiments on the dynamics of the glass-former polypropylene glycol covering a temperature range from room temperature to the glass transition at T(g)=205 K using silica tracer particles. Three temperature regimes are identified: At high temperatures, Brownian motion of the tracer particles is observed. Near T(g), the dynamics is hyperdiffusive and ballistic. Around 1.12T(g), we observe an intermediate regime. Here the stretching exponent of the Kohlrausch-Williams-Watts function becomes q dependent. By analyzing higher-order correlations in the scattering data, we find that dynamical heterogeneities dramatically increase in this intermediate-temperature regime. This leads to two effects: increasing heterogeneous dynamics and correlated motion at temperatures close to and below 1.12T(g).

Resolving high-speed colloidal dynamics beyond detector response time via two pulse speckle contrast correlation

We report an alternate light scattering approach to measure intermediate scattering function and structures of colloidal suspension by using two-pulse speckle contrast correlation analysis. By systematically controlling time-delays between two laser pulses incident on the sample, we are able to monitor transient evolution of coherent diffraction pattern, from which particle dynamics at different length and time scales are obtained simultaneously. Our result demonstrates the feasibility of utilizing a megapixel detector to achieve sufficient data statistics in a short amount of time while enabling microsecond time-resolution. Ultimately, this method provides means to measure high-speed dynamics well beyond the time response limit of a large area two-dimensional (2D) detector.

Characteristics of angular cross correlations studied by light scattering from two-dimensional microsphere films

Recently the analysis of scattering patterns by angular cross-correlation analysis (CCA) was introduced to reveal the orientational order in disordered samples with special focus to future applications on x-ray free-electron laser facilities. We apply this CCA approach to ultra-small-angle light-scattering data obtained from two-dimensional monolayers of microspheres. The films were studied in addition by optical microscopy. This combined approach allows to calculate the cross-correlations of the scattering patterns, characterized by the orientational correlation function Ψ(l)(q), as well as to obtain the real-space structure of the monolayers. We show that CCA is sensitive to the orientational order of monolayers formed by the microspheres which are not directly visible from the scattering patterns. By mixing microspheres of different radii the sizes of ordered monolayer domains is reduced. For these samples it is shown that Ψ(l)(q) quantitatively describes the degree of hexagonal order of the two-dimensional films. The experimental CCA results are compared with calculations based on the microscopy images. Both techniques show qualitatively similar features. Differences can be attributed to the wave-front distortion of the laser beam in the experiment. This effect is discussed by investigating the effect of different wave fronts on the cross-correlation analysis results. The so-determined characteristics of the cross-correlation analysis will be also relevant for future x-ray-based studies.

Single shot speckle and coherence analysis of the hard X-ray free electron laser LCLS

The single shot based coherence properties of hard x-ray pulses from the Linac Coherent Light Source (LCLS) were measured by analyzing coherent diffraction patterns from nano-particles and gold nanopowder. The intensity histogram of the small angle x-ray scattering ring from nano-particles reveals the fully transversely coherent nature of the LCLS beam with a number of transverse mode 〈Ms〉 = 1.1. On the other hand, the speckle contrasts measured at a large wavevector yields information about the longitudinal coherence of the LCLS radiation after a silicon (111) monochromator. The quantitative agreement between our data and the simulation confirms a mean coherence time of 2.2 fs and a x-ray pulse duration of 29 fs. Finally the observed reduction of the speckle contrast generated by x-rays with pulse duration longer than 30 fs indicates ultrafast dynamics taking place at an atomic length scale prior to the permanent sample damage.

Breakdown of the x-ray resonant magnetic scattering signal during intense pulses of extreme ultraviolet free-electron-laser radiation

We present results of single-shot resonant magnetic scattering experiments of Co/Pt multilayer systems using 100 fs long ultraintense pulses from an extreme ultraviolet (XUV) free-electron laser. An x-ray-induced breakdown of the resonant magnetic scattering channel during the pulse duration is observed at fluences of 5  J/cm(2). Simultaneously, the speckle contrast of the high-fluence scattering pattern is significantly reduced. We performed simulations of the nonequilibrium evolution of the Co/Pt multilayer system during the XUV pulse duration. We find that the electronic state of the sample is strongly perturbed during the first few femtoseconds of exposure leading to an ultrafast quenching of the resonant magnetic scattering mechanism.

Invited article: Coherent imaging using seeded free-electron laser pulses with variable polarization: first results and research opportunities

FERMI@Elettra, the first vacuum ultraviolet and soft X-ray free-electron laser (FEL) using by default a "seeded" scheme, became operational in 2011 and has been opened to users since December 2012. The parameters of the seeded FERMI FEL pulses and, in particular, the superior control of emitted radiation in terms of spectral purity and stability meet the stringent requirements for single-shot and resonant coherent diffraction imaging (CDI) experiments. The advantages of the intense seeded FERMI pulses with variable polarization have been demonstrated with the first experiments performed using the multipurpose experimental station operated at the diffraction and projection imaging (DiProI) beamline. The results reported here were obtained with fixed non-periodic targets during the commissioning period in 2012 using 20-32 nm wavelength range. They demonstrate that the performance of the FERMI FEL source and the experimental station meets the requirements of CDI, holography, and resonant magnetic scattering in both multi- and single-shot modes. Moreover, we present the first magnetic scattering experiments employing the fully circularly polarized FERMI pulses. The ongoing developments aim at pushing the lateral resolution by using shorter wavelengths provided by double-stage cascaded FERMI FEL-2 and probing ultrafast dynamic processes using different pump-probe schemes, including jitter-free seed laser pump or FEL-pump∕FEL-probe with two color FEL pulses generated by the same electron bunch.

Ultrafast optical demagnetization manipulates nanoscale spin structure in domain walls

During ultrafast demagnetization of a magnetically ordered solid, angular momentum has to be transferred between the spins, electrons, and phonons in the system on femto- and picosecond timescales. Although the intrinsic spin-transfer mechanisms are intensely debated, additional extrinsic mechanisms arising due to nanoscale heterogeneity have only recently entered the discussion. Here we use femtosecond X-ray pulses from a free-electron laser to study thin film samples with magnetic domain patterns. We observe an infrared-pump-induced change of the spin structure within the domain walls on the sub-picosecond timescale. This domain-topography-dependent contribution connects the intrinsic demagnetization process in each domain with spin-transport processes across the domain walls, demonstrating the importance of spin-dependent electron transport between differently magnetized regions as an ultrafast demagnetization channel. This pathway exists independent from structural inhomogeneities such as chemical interfaces, and gives rise to an ultrafast spatially varying response to optical pump pulses.

Endstation for ultrafast magnetic scattering experiments at the free-electron laser in Hamburg

An endstation for pump-probe small-angle X-ray scattering (SAXS) experiments at the free-electron laser in Hamburg (FLASH) is presented. The endstation houses a solid-state absorber, optical incoupling for pump-probe experiments, time zero measurement, sample chamber, and detection unit. It can be used at all FLASH beamlines in the whole photon energy range offered by FLASH. The capabilities of the setup are demonstrated by showing the results of resonant magnetic SAXS measurements on cobalt-platinum multilayer samples grown on freestanding Si(3)N(4) membranes and pump-laser-induced grid structures in multilayer samples.

High contrast x-ray speckle from atomic-scale order in liquids and glasses

The availability of ultrafast pulses of coherent hard x rays from the Linac Coherent Light Source opens new opportunities for studies of atomic-scale dynamics in amorphous materials. Here, we show that single ultrafast coherent x-ray pulses can be used to observe the speckle contrast in the high-angle diffraction from liquid Ga and glassy Ni(2)Pd(2)P and B(2)O(3). We determine the thresholds above which the x-ray pulses disturb the atomic arrangements. Furthermore, high contrast speckle is observed in scattering patterns from the glasses integrated over many pulses, demonstrating that the source and optics are sufficiently stable for x-ray photon correlation spectroscopy studies of dynamics over a wide range of time scales.

Single shot spatial and temporal coherence properties of the SLAC Linac Coherent Light Source in the hard x-ray regime

We measured the transverse and longitudinal coherence properties of the Linac Coherent Light Source (LCLS) at SLAC in the hard x-ray regime at 9 keV photon energy on a single shot basis. Speckle patterns recorded in the forward direction from colloidal nanoparticles yielded the transverse coherence properties of the focused LCLS beam. Speckle patterns from a gold nanopowder recorded with atomic resolution allowed us to measure the shot-to-shot variations of the spectral properties of the x-ray beam. The focused beam is in the transverse direction fully coherent with a mode number close to 1. The average number of longitudinal modes behind the Si(111) monochromator is about 14.5 and the average coherence time τ(c)=(2.0±1.0) fc. The data suggest a mean x-ray pulse duration of (29±14)  fs behind the monochromator for (100±14) fc electron pulses.

Slow aging dynamics and avalanches in a gold-cadmium alloy investigated by x-ray photon correlation spectroscopy

Results of a x-ray photon correlation spectroscopy experiment on the very weakly first order martensitic transformation of a Au50.5Cd49.5 single crystal are presented. Slow non-equilibrium-dynamics are observed in a narrow temperature interval in the direct vicinity of the otherwise athermal phase transformation. These dynamics are associated with the martensite-aging effect. The dynamical aging is accompanied by an avalanchelike behavior which is identified with an incubation-time phenomenon.

X-ray holographic microscopy with zone plates applied to biological samples in the water window using 3rd harmonic radiation from the free-electron laser FLASH

The imaging of hydrated biological samples - especially in the energy window of 284-540 eV, where water does not obscure the signal of soft organic matter and biologically relevant elements - is of tremendous interest for life sciences. Free-electron lasers can provide highly intense and coherent pulses, which allow single pulse imaging to overcome resolution limits set by radiation damage. One current challenge is to match both the desired energy and the intensity of the light source. We present the first images of dehydrated biological material acquired with 3rd harmonic radiation from FLASH by digital in-line zone plate holography as one step towards the vision of imaging hydrated biological material with photons in the water window. We also demonstrate the first application of ultrathin molecular sheets as suitable substrates for future free-electron laser experiments with biological samples in the form of a rat fibroblast cell and marine biofouling bacteria Cobetia marina.

Imaging the in-plane magnetization in a Co microstructure by Fourier transform holography

We report on experiments using Fourier transform holography to image the in-plane magnetization of a magnetic microstructure. Magnetic sensitivity is achieved via the x-ray magnetic circular dichroism effect by recording holograms in transmission at off-normal incidence. The reference beam is defined by a narrow hole milled at an inclined angle into the opaque mask. We present magnetic domain images of an in-plane magnetized cobalt element with a size of 2 μm × 2 μm× 20 nm. The domain pattern shows a multi-vortex state that deviates from the simple Landau ground state.

Dynamics at the liquid-vapor interface of a supercooled organic glass former

We investigated the dynamics near the liquid-vapor interface of the supercooled model organic glass former dibutyl phthalate by using surface-sensitive x-ray scattering techniques. Our results reveal significant enhancement of the relaxation rate over a wide length-scales range. The analysis of the dispersion relation of long-wavelength surface fluctuations yields a nonzero value of the share modulus near the free surface. At the molecular level, the dynamics in the near surface region (10-15 nm) is inhomogeneous. The mobility is decreasing with increasing distance from the free surface. Below the bulk glass transition, two distinct relaxation times were observed differing by 1 order of magnitude. The observed fast relaxation proves the existence of a high mobility liquidlike surface layer of 10 nm thickness on top of a frozen in bulk system.

Tissue penetration of moxifloxacin into human gallbladder wall in patients with biliary tract infections

OBJECTIVES

Moxifloxacin, the newest fourth-generation fluoroquinolone, has a broad spectrum of antibacterial activity covering both Gram-positive and Gram-negative aerobic and anaerobic bacteria and is therefore very well suited for the treatment of biliary tract infections. The present study aimed to determine the penetration of moxifloxacin into gallbladder tissue to evaluate its antibiotic potential in this indication.

PATIENTS AND METHODS

Hospitalized patients with acute cholecystitis received a single, 1 h infusion of 400 mg of moxifloxacin before cholecystectomy. Serum and gallbladder wall tissue samples were collected during surgery, and the moxifloxacin concentrations were measured by HPLC.

RESULTS

Sixteen patients (eight men and eight women) were included between January 2007 and April 2008. The time between start of infusion and gallbladder removal ranged from 50 min to 21 h 10 min. The serum concentration at the time of cholecystectomy was between 0.39 and 4.37 mg/L, and the tissue concentration between 1.73 and 17.08 mg/kg. The tissue-to-serum concentration ratio ranged from 1.72 to 6.33.

CONCLUSIONS

The results show that moxifloxacin penetrates well into gallbladder tissue and is therefore a therapeutic option for biliary tract infection. The highest concentrations in serum and gallbladder tissue were measured shortly after the end of a 1 h infusion. As perioperative prophylaxis, moxifloxacin should therefore be administered 30-60 min before the first surgical incision.

Two-dimensional heterogeneous dynamics at the surface of a colloidal suspension

We report on an x-ray photon correlation spectroscopy experiment investigating the surface structure and dynamics of colloidal particles suspended in a supercooled viscous liquid. The static structure factor in the direction parallel and perpendicular to the surface reveals a more disordered structure at the surface as compared to the bulk. The particles display heterogeneous ballistic dynamics parallel to the surface. The particle dynamics in the direction perpendicular to the surface is much slower and does not show the hallmarks of ballistic motion.

Coherent-pulse 2D crystallography using a free-electron laser x-ray source

Coherent diffractive imaging for the reconstruction of a two-dimensional (2D) finite crystal structure with a single pulse train of free-electron laser radiation at 7.97 nm wavelength is demonstrated. This measurement shows an advance on traditional coherent imaging techniques by applying it to a periodic structure. It is also significant that this approach paves the way for the imaging of the class of specimens which readily form 2D, but not three-dimensional crystals. We show that the structure is reconstructed to the detected resolution, given an adequate signal-to-noise ratio.

Measuring temporal speckle correlations at ultrafast x-ray sources

We present a new method to extract the intermediate scattering function from series of coherent diffraction patterns taken with 2D detectors. Our approach is based on analyzing speckle patterns in terms of photon statistics. We show that the information obtained is equivalent to the conventional technique of calculating the intensity autocorrelation function. Our approach represents a route for correlation spectroscopy on ultrafast timescales at X-ray free-electron laser sources.

Partially wetting thin liquid films: structure and dynamics studied with coherent x rays

We studied the surface structure of thin liquid films vapor deposited on solid substrates in a partial wetting situation by means of coherent x-ray scattering. No dynamics has been observed showing the absence of capillary waves on liquid films partially wetting a substrate. Instead an exponential form of the height-height correlation function has been found pointing toward a solidlike behavior of the thin liquid films at large length scales. The exact surface structure and degree of replication with the substrate depend on the deposition rate of the molecules.

Fast track--different implications in pancreatic surgery

Concepts in "fast-track" surgery, which provide optimal perioperative care, have been proven to significantly reduce complication rates and decrease hospital stay. This study explores whether fast-track concepts can also be safely applied and improve the outcomes of major pancreatic resections. Perioperative data from 255 consecutive patients, who underwent pancreatic resection by means of fast-track surgery in a high-volume medical center, were analyzed using univariate and multivariate models. Of the 255 patients, 180 received a pancreatic head resection and 51 received distal, 15 received total, and 9 received segmental pancreatectomies. The patients were discharged on median day 10 with a 30-day readmission rate of 3.5%. The in-hospital mortality was 2%, whereas medical and surgical morbidities were 17 and 25%, respectively. Fast-track parameters, such as first stools, normal food, complete mobilization, and return to normal ward, correlated significantly with early discharge (p < 0.05). Patients' age, operation time, and early extubation proved to be independent factors of early discharge, shown through multivariate analysis (odds ratio: 4.0, 2.0, and 2.8, respectively; p < 0.05). Low readmission, mortality, and morbidity rates demonstrate that fast-track surgery is in fact feasible and safe and promotes earlier discharge without compromising patient outcomes.

Two-dimensional dynamics of metal nanoparticles on the surface of thin polymer films studied with coherent X rays

X-ray photon-correlation spectroscopy is used to measure the dynamic structure factor f(q,tau) of gold particles moving on the surface of thin polymer films. Above the glass transition of the polymer the peculiar form f(q,tau) approximately exp[-(Gamma tau)(alpha)] is found with 0.7 < alpha < 1.5, depending on sample age and temperature. The relaxation rates Gamma scale linearly with q, excluding a simple Brownian diffusive motion. This type of behavior, already observed in aging bulk soft matter systems, is explained by a power law distribution of particle velocities due to ballistic motion.

Anharmonic motions of Kr in the clathrate hydrate

The anomalous glass-like thermal conductivity of crystalline clathrates has been suggested to be the result of the scattering of thermal phonons of the framework by 'rattling' motions of the guests in the clathrate cages. Using the site-specific (83)Kr nuclear resonant inelastic scattering spectroscopy in combination with conventional incoherent inelastic neutron scattering and molecular-dynamics simulations, we provide unambiguous evidence and characterization of the effects on these guest-host interactions in a structure-II Kr clathrate hydrate. The resonant scattering of phonons led to unprecedented large anharmonic motions of the guest atoms. The anharmonic interaction underlies the anomalous thermal transport in this system. Clathrates are prototypical models for a class of crystalline framework materials with glass-like thermal conductivity. The explanation of the unusual molecular dynamics has a wide implication for the understanding of the thermal properties of disordered solids and structural glasses.

Surface roughness and adsorption isotherms of molecularly thin liquid films: an x-ray reflectivity study

We present an x-ray reflectivity study of molecularly thin films of liquid isobutane adsorbed on liquid glycerol. The glycerol-isobutane interface serves as a model system to investigate the influence of the substrate adsorbate interactions on both adsorption isotherms and capillary wave fluctuations. The measured surface roughness is smaller than expected from the harmonic approximation of the interaction potential. Expressions for the surface roughness in slightly anharmonic potentials are given and compared to the experimental data. A good agreement between data and theory is achieved.

Surface roughness of supercooled polymer melts

We report on in situ x-ray reflectivity measurements of the surface roughness of supercooled glass forming polymers in a temperature range from 190 to 330 K. The experimentally determined rms roughness has been found to obey the capillary wave model of a single liquid/vapor interface over the entire temperature range. An expression for the surface roughness below the bulk glass transition (T(G) approximately equal to 200 K) is deduced from the viscoelastic theory of surface fluctuations; however, no indication of a frozen-in surface roughness has been observed in the experiment. Additionally, it is shown that precise values of the surface tension of highly viscous liquids in the supercooled state can be determined by x-ray reflectivity.

Phase behaviour of n-hexane/perfluoro-n-hexane binary thin wetting films

We present X-ray reflectivity investigations of the concentration distribution in binary liquid thin films on silicon substrates. The liquid-vapor coexistence of the binary mixture investigated, hexane and perfluorohexane, is far from criticality. Therefore, a sharp interface separates the liquid film from the vapor. The data reveal a separation of the film in layers parallel to the substrate. A phase diagram is constructed as a projection to the (composition difference, temperature) space, covering a temperature range corresponding to the one-phase and the two-phase regime of the bulk liquid. Although the composition data indicate a mixing gap similar to that of the bulk system, there are two major differences: i) only the near-surface phase changes its composition significantly, and ii) a composition gradient in the film exists also at higher temperatures where in the bulk system the one-phase regime exists.

New aspects on reperfusion injury to liver--impact of organ harvest

The aetiology of primary graft non-function and dysfunction is unknown but most likely involves Kupffer cell-dependent reperfusion injury; however, reasons for transplant failure are complex and involve organ retrieval, preservation and transplantation. Important factors include the donor's condition, cold and warm ischaemic times, operative complications in the recipient, the immune status of the recipient and surgical experience. The donor operation and surgical technique also have an effect on outcome after transplantation. This is important, since surgical organ manipulation of the liver during harvest cannot be prevented completely with standard procedures. This is especially true during organ harvest for living-donor liver transplantation and split-liver transplantation in general. Most recently, an experimental setting has conclusively demonstrated that gentle in situ organ manipulation by touching, retracting and moving liver lobes gently during harvest dramatically reduces survival after transplantation via Kupffer cell-dependent mechanisms. These mechanisms involve disturbances of hepatic microcirculation, a hypermetabolic state of the liver, hypoxia and almost complete denudation of endothelial lining cells. Glycine, a non-essential, non-toxic amino acid, which prevents activation of Kupffer cells, prevented all effects of harvest-related injury to the liver when given before transplantation. Based on these data, intravenous glycine has been administered to patients before reperfusion of their liver transplant. Both serum transaminases and the rate of primary non-function have been dramatically reduced, compared with historic controls. These preliminary clinical results with glycine before reperfusion are promising for further improvement of the overall outcome after liver transplantation.

The structure of methane hydrate under geological conditions a combined Rietveld and maximum entropy analysis

We present a study of the structure of a fully deuterated methane hydrate under the geological conditions found in the world's oceans. In situ high-resolution neutron diffraction experiments have been performed at temperatures of 220, 275, and 280 K and a pressure of 100 bar, corresponding to the conditions at 1000 m water depth. The data were analyzed with a combination of Rietveld refinement and maximum entropy methods. From the Rietveld refinement, precise atomic parameters of the host lattice could be determined, indicating increasing distortions of the structure of the cages at elevated temperatures and pressures. Debye-Waller factors of the encaged CD(4) molecules have been found to exceed the values of the Debye-Waller factors of the D(2)O molecules considerably. In the large cage of structure type I the thermal center-of-mass displacements of the guests are 5-10 times larger than those of the water molecules. From the maximum entropy analysis maps of the scattering length density have been obtained, showing details of the vibrational amplitudes of the atoms in methane hydrate. The Debye-Waller factors of all molecules have been found to deviate considerably from a simple spherical geometry.

Capillary waves at the transition from propagating to overdamped behavior

We measure the dispersion relation of capillary waves on a liquid surface by heterodyne x-ray photon correlation spectroscopy near the transition from propagating to overdamped dynamic behavior. A strong deviation of the propagation frequency from the small-damping result omega(p) proportional, variant k(3/2) is observed long before the actual transition where ( partial differential omega(p)/ partial differential k)<0 and omega(p) tends to zero. This behavior is successfully described by expressions derived within linear response theory.

Risk of gas embolism in hand-assisted versus total laparoscopic hepatic resection

Laparoscopic hepatic resection represents an alternative to open surgery in patients with advanced underlying hepatic disease. Management of haemorrhage and the risk of gas embolism are the major problems in laparoscopic liver surgery. In this study, safety and efficacy of liver dissection using ultrasonic energy was investigated in hand-assisted versus total laparoscopic surgery. The study had a special emphasis on evaluating the risk of gas embolism during both procedures. Female pigs were divided into two groups for A) total laparoscopic (n=7), and B) hand-assisted laparoscopic (n=7) hepatic resection. For tissue dissection, an ultrasound aspirator (CUSA) was used in both groups. Laparoscopic procedure was performed under a CO2 pneumoperitoneum (intraperitoneal pressure: 12 mmHg). Before dissection, a Pringle manoeuver was carried out. The anaesthetized pigs were monitored haemodynamically by an arterial line and Swan-Ganz catheter. Transoesophageal echocardiography (TEE) was performed with special attention to the right atrium and ventricle. Gas emboli were graded according to size and correlated with haemodynamic and blood-gas data. In both groups, the ultrasound-aspirator enabled an effective tissue dissection. In total laparoscopic hepatic resection, TEE monitoring disclosed gas embolism in 5/7 (71%) animals. In 3/7 (42%) animals, gas embolism was accompanied by a sequence of cardiac arrhythmia. No direct correlation was noted between episodes of embolism and blood-gas variables. None of the pigs died after episodes of embolization. In hand-assisted liver resection, no air embolism was noted. The internal hand impressively facilitated organ exposure and provided an immediate and efficient haemorrhage control. The use of an ultrasound aspirator system enables an effective laparoscopic hepatic dissection. Total laparoscopic liver dissection is at increased risk for gas embolism, whereas hand-assisted laparoscopic procedure appears to reduce this risk. Due to tactile response and facilitated retraction of the liver parenchyma, the hand-assisted procedure shows impressive advantages in laparoscopic liver surgery.

Observation of heterodyne mixing in surface x-ray photon correlation spectroscopy experiments

We report measurements of propagating capillary waves on a liquid water surface at T=5 degrees C with x-ray photon correlation spectroscopy. The experiment has been performed under grazing incidence conditions with an incoming x-ray beam below the critical angle of total external reflection. In the q region investigated the measured intensity-intensity autocorrelation functions of the liquid water surface were found to be heterodyne signals, i.e., a combination of first- and second-order correlation functions g(1)(tau) and g(2)(tau).

Technical complications of continuous intra-arterial chemotherapy with 5-fluorodeoxyuridine and 5-fluorouracil for colorectal liver metastases

BACKGROUND

Intra-arterial chemotherapy is an effective modality to treat unresectable hepatic metastases from colorectal primaries if systemic chemotherapy has failed. Response rates of more than 40% and a median survival of 15 to 25 months have been reported from randomized trials. In this retrospective study, we analyzed specific technical complications associated with continuous intra-arterial chemotherapy for colorectal liver metastases.

METHODS

From 1982 to 1995, single-center clinical data from 180 patients with colorectal liver metastases were evaluated. Continuous intra-arterial chemotherapy was administered using either an implanted infusion pump or an intra-arterial port with an external infusion pump. The intra-arterial catheter was implanted according to the Watkins' technique. The treatment protocols consisted of 5-fluorouracil- or 5-fluorodeoxyuridine-based regimens.

RESULTS

A total of 70 patients (39%) received an intra-arterial infusion pump and 110 patients (61%) an intra-arterial port. Sixty-eight technical complications affected port systems (62%), whereas 29 patients with pumps (41%) were affected by technical complications. Therapy-relevant complications were observed in 47% of the ports and 30% of the infusion pumps. The median complication-free survival was 12.2 months for infusion pumps and 7.3 months for ports (P =.0016).

CONCLUSIONS

Our data demonstrate that pumps are superior to ports in terms of complication rate and complication-free survival. On the basis of our results, pumps have a potential for a longer treatment, which may result in a prolonged median survival.

Use of the robot system Da Vinci for laparoscopic repair of gastro-oesophageal reflux in children

In adult patients, laparoscopic surgery, using a robot system (Da Vinci, Intuitive Surgical, Mountain View, California), has been recently introduced into surgical practice. To investigate the feasibility of the system in paediatric surgery, laparoscopic fundoplications as well as cholecystectomies have been performed. In July 2000 we used the robot system for the first time on an 11-year-old girl with gastro-oesophageal reflux, and since that time on 7 other children. Altogether 5 Thal and 3 Nissen procedures have been carried out. The average age was 12 years, with a range of 7 to 16 years. All operations were performed without complications and without conversion to open surgery. The medium operating time was 146 min with a range of 105 to 180 minutes. Compared to conventional laparoscopy, the 3-dimensional high-quality vision, the advanced instrument movements and the ergonomic position of the surgeon seems to enhance surgical precision. In our opinion, the use of the robot system is feasible and safe in paediatric surgery. The technique is limited due to the fact that instruments adapted to the size of small children are not yet available.

Transoesophageal echocardiography shows high risk of gas embolism during laparoscopic hepatic resection under carbon dioxide pneumoperitoneum

BACKGROUND

The ultrasonically activated scalpel (UAS) enables safe and effective laparoscopic tissue dissection, making hepatic resection feasible. This study compared blood loss and risk of gas embolism using the UAS during open hepatic resection and laparoscopic hepatic resection.

METHODS

Female pigs were divided into two groups for laparoscopic (n = 7) and open (n = 5) left hepatic lobectomy. The UAS was used for both tissue cutting and coagulation. Laparoscopic liver resection was performed under carbon dioxide pneumoperitoneum (intraperitoneal pressure 12 mmHg). During surgery animals were monitored haemodynamically by an arterial line and Swan-Ganz catheter. Two-dimensional transoesophageal echocardiography (2D-TEE) was used to detect gas emboli with special attention to the right atrium and ventricle. Gas emboli were graded according to size, and correlated with haemodynamic and blood gas data.

RESULTS

During open and laparoscopic hepatic resection the UAS resulted in minimal blood loss and effective tissue dissection. No air embolism was seen during open surgery. With laparoscopic hepatic resection 2D-TEE revealed gas embolism in all animals. Gas embolism was accompanied by cardiac arrhythmia in four of seven animals. No direct correlation was observed between embolism episodes and blood gas variables. There were no deaths after episodes of embolization. A significant decrease in arterial partial pressure of oxygen was seen at the end of the laparoscopic procedure in all animals.

CONCLUSION

The UAS causes minimal blood loss during both open and laparoscopic hepatic resection. Laparoscopic liver dissection under carbon dioxide pneumoperitoneum carries a high risk of gas embolism.

Oncologic implications of laparoscopic and open surgery

Although instrumental manipulation and mechanical tumor cell spillage seem to play the major role in port-site metastases from laparoscopic cancer surgery, minimally invasive procedures are used more and more in the resection of malignancies. However, port-site metastases also have been reported after resection of colon cancer in International Union Against Cancer (UICC) stage I [2, 14]. Therefore, changes in the peritoneal environment during laparoscopy also might influence intra- and extraperitoneal tumor growth during laparoscopy and pneumoperitoneum. Different results of experimental studies presented at the Third International Conference for Laparoscopic Surgery are analyzed and discussed.

[Robot-assisted laparoscopic cholecystectomy and fundoplication--initial experiences with the Da Vinci system]

We report on our first five robot-assisted laparoscopic cholecystectomies and one fundoplication (Da Vinci system). No postoperative complications were observed. For the cholecystectomies (three elective and two acute cases) mean operation time was 1 h 35 min, and mean hospital stay was 5 days; for fundoplication the operation time was 2 h 15 min. The main advantages seem to be improved visualization by using a stereo camera und ease of precise dissection by micromechanical instruments directed by masterslaves from a distant console. The main disadvantage is the high cost. To fully evaluate the benefit for the patient, prospective clinical trials are warranted.