Tortuous Shape Research Articles

Confocal endomicroscopy diagnostic criteria for early signet-ring cell carcinoma in hereditary diffuse gastric cancer

BackgroundRecognition of early signet-ring cell carcinoma (SRCC) in patients with hereditary diffuse gastric cancer (HDGC) undergoing endoscopic surveillance is challenging. We hypothesized that probe-based confocal laser endomicroscopy (pCLE) might help diagnose early cancerous lesions in the context of HDGC. The aim of this study was to identify pCLE diagnostic criteria for early SRCC.MethodsPatients with HDGC syndrome were prospectively recruited and pCLE assessment was performed on areas suspicious for early SRCC and control regions during an endoscopic surveillance procedure. Targeted biopsies were taken for gold standard histologic assessment. In Phase I two investigators assessed video sequences off-line to identify pCLE features related to SRCC. In Phase II pCLE diagnostic criteria were evaluated in an independent video set by the investigators blinded to the histologic diagnosis. Sensitivity, specificity, accuracy, and interobserver agreement were calculated.ResultsForty-two video sequences from 16 HDGC patients were included in Phase I. Four pCLE patterns associated to SRCC histologic features were identified: (A) glands with attenuated margins, (B) glands with spiculated or irregular shape, (C) heterogenous granular stroma with sparse glands, (D) enlarged vessels with tortuous shape. In Phase II, 38 video sequences from 15 patients were assessed. Criteria A and B and C had the highest diagnostic accuracy, with a κ for interobserver agreement ranging from 0.153 to 0.565. A panel comprising these 3 criteria with a cut-off of at least one positive criterion had a sensitivity of 80.9% (95%CI:58.1—94.5%) and a specificity of 70.6% (95%CI:44.0—89.7%) for a diagnosis of SRCC.ConclusionsWe have generated and validated off-line pCLE criteria for early SRCC. Future real-time validation of these criteria is required.

Predicting hydrogen microporosity in long solidification range ternary Al-Cu-Li alloys by coupling CALPHAD and cellular automata model

Aluminum-lithium alloys have wide applications in aerospace industries in the 21st century but their manufacturing is extremely difficult due to the 10 times more equilibrium hydrogen concentration in the liquid than the solubility limit in traditional Al alloys (0.036 mL/100gSTP). The reduction of solubility from liquid to solid by 95% leads to hydrogen porosity being hard to control. In this work, a three-dimensional multicomponent cellular automaton (CA) model is coupled with CALPHAD calculations to simulate the nucleation and growth of hydrogen porosity and its interaction with surrounding dendritic structures during the solidification of Al-Cu-Li alloys. By quantifying the effects of hydrogen concentration, cooling rate, and Li content, it was found the solidification conditions can effectively reduce porosity size. To validate the model, X-ray computed tomography (XCT) has been used to obtain not only the size but also the morphology of porosity as a function of cooling conditions. It was found that porosity grows elongated and tortuous shape at slow cooling rates between columnar dendrites, filling up the empty spaces of secondary arms, while it tends to be dispersed spherical shape when its surrounding grains are refined to equiaxed structures at high cooling rates.

INTERPRETATION OF MORPHOLOGICAL PICTURE OBSERVED IN HISTOLOGICAL PREPARATIONS FROM THE POINT THE VIEW OF STEREOLOGY

The study of a biological microobject from the standpoint of three-dimensionality gives more correct and realistic vision. The study material included 8 preparations of the palatine and labial salivary glands of adult human individuals fixed in 4% glutaraldehyde solution in phosphate buffer (pH 7.4). Following pre-fixation, the object was cut into individual slices and fixed in a freshly prepared similar fixator adding 1% calcium chloride solution at 4 °C for 12 hours. The tissue was washed after the fixation and then processed according to the requirements for electron microscopy. Tissues enclosed in epoxy resin were used to obtain semi-thin series of histological sections for further graphic and plastic reconstruction of epithelial components (including tubular) glands. Semi-thin sections were stained with 0.1% toluidine blue in phosphate buffer with different pH (from 5.5 to 8.5). Spiral, corkscrew, tortuous, arched and other forms of biological tubular structures at the microscopic level are no exception and, as our study shows, are natural phenomena along with their rectilinear shape. It can be assumed that the interdependence between the shape of the tubular transport microchannels and the laminar motion of the fluid naturally reflects the elements of curvilinear symmetry and, in particular, its spiral property. Conclusion. Thus, we could assume that the tortuous shape of transport channels of human and animal tissues is a useful stereomorphological device, and their study and three-dimensional modelling is of great scientific interest, in particular, for understanding the mechanism of laminar fluid movement through biological tubes.

An unusual cause of renovascular hypertension in a pediatric patient with chronic kidney disease

Background: Renovascular hypertension (RVH) accounts for 5–10% of arterial hypertension in children and is most commonly caused by fibromuscular dysplasia. Sporadically, renal artery stenosis in pediatric patients is caused by extrinsic compressive masses. Case report: A 12-year-old patient with complex urinary tract defect (dysplastic left kidney — nephrectomy at 11 months, right ectopic kidney in the midline, behind the urinary bladder), chronic kidney disease (CKD) stage 2, and arterial hypertension was admitted to the hospital due to worsening of kidney function during angiotensin-converting enzyme inhibitor (ACE-I) therapy. CT angiography revealed a right ectopic kidney located above the bladder, supplied by a single renal artery originating from the right common iliac artery. The renal artery had a tortuous shape with width in the ostium approx. 4.5 mm; then, the artery was bent and ran between the common iliac artery and the kidney. Ultrasound performed with a filled bladder showed bending and stenosis of the renal artery at the origin from the right common iliac — peak systolic velocity (PSV) 4.5–5.5 m/s and renal-aortic ratio (RAR) 3.1. With an empty bladder, no bending or stenosis was visible (PSV 1.7–1.9 m/s and RAR 1.0). Uroflowmetry revealed a dysfunctional micturition curve, large bladder capacity, and post-void urine retention. ACE-I was changed to beta-blocker and doxazosin, which led to blood pressure and kidney function normalization. Conclusions: Renal ectopia associated with bladder dysfunction may result in renal artery stenosis causing renovascular hypertension.

A new species of palaeosiphonocladal algae Kamaena gigantea from the Lower–lowermost Middle Mississippian sediments of the Donbas (Upper Tournaisian–Lower Visean)


 
 
 
 A new species of green paleosiphonocladаl algae Kamaena gigantea from the Lower–lowermost Middle Mississippian sediments of the Donbas has been described. This species was distinguished from other representatives of the genus Kamaena Antropov by its extremely large size, tortuous shape of the thallus and convex partitions. The species belongs to an artificial taxonomic unit of the Kamaenae Shuysky tribe, 1985 , of the family Palaeoberesellaceae Mamet et Roux , a systematic grouping which is still controversial. The attribution of this family to green siphonocladal algae is controversial and quite conditional, the opinions of different authors being based on personal vision, and varying in range from the plant to the animal kingdom. A characteristic feature of the family is the tubular shape , the segments of which are connected by partitions with a large central pore, sometimes with additional small pores. The thallus wall (fossilized remains of the body) is porous or non-porous and has simple or branched pores. It has been emphasized that study of Paleoberezellides in thin sections, the sometimes fuzzy images of the typical material in publications and ignorance of other researchers’ publications have caused confusion and led to the selection of an unreasonably large number of genera and species within the family. It has been noted that in previous works, representatives of this species were mistakenly identified as Anthracoporellopsis Maslov, a genus characteristic of the Lower–Middle Pennsylvanian sediments. This erroneous definition was based mainly on general external similarity, a poorly illustrated description of the type species, and did not take into account the morphological features that were characteristic for the genus. It has been found that representatives of the new species had a rather limited stratigraphic distribution: the Upper Tournaisian (Dokuchaevskian horizon) and the Lower Visean (Hlybokian–Sukhinskian horizons), and the most similar specimens found in the Ural region in underlying Tournaisian sediments were, unfortunately, poorly illustrated and smaller in size and had a narrower thallus. It has been noted that a characteristic feature of the tribe Kamaenae Shuysky, 1985 was the tubular shape, its inter-segmental partitions were perpendicular to the walls and were at the approximately same interval from each other. It has been pointed out that representatives of the new species were found mainly in grainstones, packstones, and wackstones − organogenic-detrital limestones along with such groups of microfauna as echinoderms and ostracods, isolated spicules of sponges and remains of worms. The material for illustrations was mainly taken from the borehole74 (near the village of Rodnikove, Starobeshiv district, Donetsk region) , which most fully revealed the Lower–Middle Pennsylvanian deposits of the southern part of the Donbas. The knowledge of the systematic composition of the Early Carboniferous algoflora has been expanded. This has helped us to conclude that the tribe Kamaeneae Shuysky, 1985 ,includes 6 genera and at least 22 species that were found in the layers from the Early Devonian to the Early Visean of the Lower Carboniferous.
 
 
 

Electrostatics in a tortuous nanochannel in a newly developed curvilinear coordinate system

Although nanochannels in tortuous shape exhibit unusual transportational characteristics, the traditional theoretical analysis of nanofluidics in such kinds of systems remains challenging, partly due to their complicated boundary description. In this paper, by developing a curvilinear coordinate system for such tortuous nanochannels, we solve the electrostatic Poisson–Boltzmann equation analytically for a two-dimensional nanochannel, with its effectiveness confirmed through numerical calculation. The influences of the geometric profile on the distribution of electric potential, ionic concentration, and surface charge on channel walls are quantitatively evaluated in a facilitated way in terms of the curvilinear coordinates introduced. Such a technique can be widely applied to many nanofluidic systems in curved channels.

Molecular dynamics simulation of microstructure evolution during the fracture process of nano-twinned Ag

In this paper, the evolution of microstructure and the role of twin boundary during the fracture process of nano-twinned Ag are studied through molecular dynamics simulation. The fracture process of nano-twinned Ag with multiple twin boundaries is compared with both the fracture process of single crystal Ag and nano-twinned Ag with single twin boundary. Results demonstrate that multiple twin boundaries can significantly improve the strength of material by influence the propagation of crack and dislocation as observed by experiments. By comparing the stress–strain relationship and evolution of microstructure, we found that the elastoplastic transition in single crystal Ag is characterized by dislocation emission from the crack tip, while the elastoplastic transition in nano-twinned Ag is characterized by dislocation crossing the twin boundary. According to crack-resistance curves and observation results of microstructure evolution, multiple twin boundaries can significantly improve the fracture toughness of nano-twinned Ag compared to single twin boundary. The role of twin boundary in the fracture process is mainly to influence the propagation of crack and dislocation. The crack tip in single crystal Ag gradually gets blunt with the nucleation and emission of dislocations, while the crack in nano-twinned Ag propagates by cleavage. To explain this phenomenon, the generalized stacking fault energies and surface energies of both nano-twinned Ag and single crystal Ag are calculated and compared. It is shown that twin boundary can influence the energy barrier for atomic slip while have no influence on the generation of fracture surface. Twin boundary can also change the propagation direction of dislocations and stacking faults. Stacking faults propagate along (111) planes in matrix grain and propagate along (111¯) planes in twin grain, showing a tortuous shape. In this process, dislocations accumulate on the twin boundary, leading to high local dislocation density and high strength of nano-twinned material, which is agreement with experiments and simulations. Our study is helpful for understanding the relationship between microscopic deformation and macroscopic properties of nano-twinned crystal material.

Metal-Organic Frameworks for Highly Selective Separation of Xylene Isomers and Single-Crystal X-ray Study of Aromatic Guest-Host Inclusion Compounds.

Separation of hydrocarbon molecules, such as benzene/cyclohexane and o-xylene/m-xylene/p-xylene, is relevant due to their widespread application as chemical feedstock but challenging because of their similar boiling points and close molecular sizes. Physisorption separation could offer an energy-efficient solution to this problem, but the design and synthesis of sorbents that exhibit high selectivity for one of the hydrocarbons remain a largely unmet challenge. Herein, we report a new heterometallic MOF with a unique tortuous shape of channels decorated with aromatic sorption sites [Li2Zn2(bpy)(ndc)3] (NIIC-30(Ph), bpy = 4,4'-bipyridine, ndc2- = naphthalene-1,4-dicarboxylate) and study of its benzene/cyclohexane and xylene vapor and liquid separation. For an equimolar benzene/cyclohexane mixture, it is possible to achieve a 10-fold excess of benzene in the adsorbed phase. In the case of xylenes, microporous framework NIIC-30(Ph) demonstrates outstanding selective sorption properties and becomes a new benchmark for m-/o-xylene separation. In addition, NIIC-30(Ph) is stable enough to carry out at least three separation cycles of benzene/cyclohexane mixtures or ternary o-xylene/m-xylene/p-xylene mixtures both in the liquid and in the vapor phase. Insights into the performance of NIIC-30(Ph) are gained from X-ray structural studies of each aromatic guest inclusion compound.

The power of molten salt in methane dry reforming: Conceptual design with a CFD study

A numerical study of the dry reforming of methane is discussed by applying molten salt as the heat source. A tortuous array of reactors, a reactor with frustum shape and a change in the number of reformer beds immersed in the molten salt are studied. The first observation is that the temperature of the heat source does not drop significantly between the inlet and outlet. This property naturally leads to a methane conversion that is proportional to the length when the catalyst volume is fixed. For a tortuous shape with 12 reactors in series, 0.4 m long each, neither the molten salt temperature nor the methane conversion differed significantly between the first and last reactors. Compared to the gas-type heat source, the molten salt turns out to be a very powerful energy carrier. In addition, we briefly discuss the frustum reactor and the variation in the number of reformer beds immersed in molten salt keeping the amount of catalyst fixed. In general, for the frustum reactor the conversion increases as the radius of the feed input becomes smaller. Finally, the CH4 conversion decreases as the number of reformer bed increases for the variation of the number of reformer beds.

Sample Preparation of Optically Cleared Liver Tissue to Identify Liver Macrophages Using 3D Microscopy.

Histology, or the study of tissue microanatomy, is essential to understanding the in situ function of varying cell types within an organ. How cells are distributed throughout organs provides an indication of how they interact with other cells and structures within the organ microanatomy. The tortuous shape and large size of liver macrophages limits the value of standard tissue thickness of 5-10μm. As a result, imaging of specimens ideally thicker than 100μm is necessary to investigate the liver microanatomy and the how macrophages are distributed within this. Modern methods of microscopy, such as confocal and light sheet microscopy, allow for the analysis of tissue specimens of a thickness well beyond 100μm in the z-dimension. Liver tissue is an opaque tissue, and as a result, different techniques are needed to ameliorate light diffraction within the tissue. These techniques, in conjunction with antibody staining and refractive index matching of the tissue, have allowed researchers to image liver tissue specimens of more than 100μm thickness. Two of these techniques are modified versions of the clearing methods known as clearing-enhanced 3D (Ce3D) and fructose, urea, and glycerol for imaging (FUnGI). Here, we discuss the steps involved in preparing tissue specimens for optically clearing tissue using Ce3D and FUnGI for subsequent analysis of the distribution of macrophages in three dimensions using a confocal microscope.

Synthesis of Carbon Fibers in the Decomposition of Acetylene and Propane–Butane Mixture in a Plasma Jet

Carbon fibers are prepared during the conversion of acetylene and propane–butane mixture in a jet of the helium and argon plasma without using catalysts. The synthesis is carried out in a plasma jet reactor. The synthesis products are studied by electron microscopy, synchronous thermal analysis and energy dispersive X-ray spectroscopy. The effect of the synthesis parameters on the structure and properties of the carbon fibers prepared in the volume is established. When the propane–butane mixture is decomposed in an inert medium, conditions are found for the synthesis of cylindrical carbon nanofibers of a tortuous shape with a diameter of up to 20 nm and a length-to-diameter ratio of up to 1000. The decomposition of acetylene at 350 Torr produces nanofibers formed by a chain of straight cylinders with a diameter of up to 20 nm, and cylindrical fibers are synthesized in the form of spirals of up to 200 nm in diameter at 150 Torr.

Morpho-elastic model of the tortuous tumour vessels

Solid tumours have the ability to assemble their own vascular network for optimizing their access to the vital nutrients. These new capillaries are morphologically different from normal physiological vessels. In particular, they have a much higher spatial tortuosity forcing an impaired flow within the peritumoral area. This is a major obstacle for the efficient delivery of antitumoral drugs. This work proposes a morpho-elastic model of the tumour vessels. A tumour capillary is considered as a growing hyperelastic tube that is spatially constrained by a linear elastic environment, representing the interstitial matter. We assume that the capillary is an incompressible neo-Hookean material, whose growth is modelled using a multiplicative decomposition of the deformation gradient. We study the morphological stability of the capillary by means of the method of incremental deformations superposed on finite strains, solving the corresponding incremental problem using the Stroh formulation and the impedance matrix method. The incompatible axial growth of the straight capillary is found to control the onset of a bifurcation towards a tortuous shape. The post-buckling morphology is studied using a mixed finite element formulation in the fully nonlinear regime. The proposed model highlights how the geometrical and the elastic properties of the capillary and the surrounding medium concur to trigger the loss of marginal stability of the straight capillary and the nonlinear development of its spatial tortuosity.

Dandelion-Like Microspherical MCM-22 Zeolite Using BP 2000 as a Hard Template.

The chemistry between layered MWW zeolite and carbon black pearls (BP 2000) as an inexpensive hard template was investigated to develop a rational one-pot synthesis of MCM-22 microspheres. The characterization results showed that the insertion of BP 2000 in the gel synthesis did not substantially compromise the crystallinity and microporosity, and the microscopic analyses showed that BP 2000 played a key role in controlling the final morphology of the MCM-22 zeolite, creating beautiful dandelion-like microspherical particles. The morphology obtained is due to the tortuous shape of the hard template, the particular MWW particle crystals, the interaction with the external surface of the MWW zeolitic precursor, and the synthesis conditions. The stacking of MWW crystals with edge-to-face orientations generates meso-/macrovoids, allowing access to the interiors of the microspheres. The microspheres were homogeneous with sizes ranging from 6 to 8 μm with an increase of the external surface and a macroporous size distribution centered at 200 nm, which is two times that of the traditional MCM-22 zeolite.

Homogenized and pore-scale analyses of forced convection through open cell foams

Open cell foams have desirable geometrical characteristics that make them a suitable choice in various heat exchanger applications. The objective of this study is to determine such volume-averaged key parameters that can characterize the complex thermal transportation process through open cell foams. These key parameters are represented by effective thermal conductivity, ke, volumetric heat transfer coefficient, hv, and dispersion conductivity, kd. In order to determine these parameters, detailed pore-scale simulations through the representative element volumes (REVs) of the actual foam structures are performed. Moreover, knowing the fact that the successful implementation of simplified foam structures as a suitable representative of the actual foam structures can simplify the complexity of the problem, it is also investigated. In the presented work, various microscopic pore-scale models are implemented for both simplified and actual foam structures to determine the key parameters. Subsequently, these key parameters are implemented into two different homogenized macroscopic models to predict the temperature fields of large-scale steady-state and transient forced convection processes. The numerical outcomes of homogenized macroscopic models are validated with the experimental data, which is available for a set of ceramic foams having different pore size (10–30 PPI) and porosity (79–87%). As a consequence of the validation process, the findings of this study reveal that the proposed methodology successfully predicts the values of the concerned key parameters. Further, it is observed that simplified foam structures cannot represent the actual foam structures, as the tortuous shape of open cell foams bound to enhance the advection and dissipation of heat due to recirculation and eddy formation.

Синтез углеродных волокон при разложении ацетилена и пропан-бутановой смеси в струе плазмы

AbstractCarbon fibers are prepared during the conversion of acetylene and propane–butane mixture in a jet of the helium and argon plasma without using catalysts. The synthesis is carried out in a plasma jet reactor. The synthesis products are studied by electron microscopy, synchronous thermal analysis and energy dispersive X-ray spectroscopy. The effect of the synthesis parameters on the structure and properties of the carbon fibers prepared in the volume is established. When the propane–butane mixture is decomposed in an inert medium, conditions are found for the synthesis of cylindrical carbon nanofibers of a tortuous shape with a diameter of up to 20 nm and a length-to-diameter ratio of up to 1000. The decomposition of acetylene at 350 Torr produces nanofibers formed by a chain of straight cylinders with a diameter of up to 20 nm, and cylindrical fibers are synthesized in the form of spirals of up to 200 nm in diameter at 150 Torr.

Study on the giant magnetoimpedance effect in micro-patterned Co-based amorphous ribbons with single strip structure and tortuous shape

Field-annealed Co-based commercial amorphous ribbons (Metglas® 2714A) with single strip structure and tortuous shape are fabricated by MEMS technology. The influence of the size, magnetic field and frequency on the giant magnetoimpedance (GMI) ratio of the ribbons with single strip structure and tortuous shape is investigated. The results show that the GMI ratio of micro-patterned Co-based amorphous ribbons with single strip structure increases with increasing in length and decreases with the increasing in width. The ribbons (length = 10 mm, width = 250 μm) with single strip can get higher GMI ratio at lower frequency (<40 MHz). The GMI ratio of micro-patterned tortuous-shaped Co-based amorphous ribbon with six turns is biggest with 82 %, obtained at a frequency of 40 MHz and a field of 20 Oe, and the GMI ratio increases with the increasing in turn number from two turns to six turns. All mechanisms (line width and tortuous shape) that influence the inductance and resistance will result in changes in the impedance and the GMI effect. The anisotropy field HK (15---20 Oe) of tortuous shape ribbon that the peak GMI ratio is larger than that (5---10 Oe) of the ribbon with single strip structure. The effect of the frequency on the GMI ratio of the ribbons with tortuous shape is more complex. This can be explanation by complex inductance of tortuous shape ribbons.

Optical transmission of nematic liquid crystal 5CB doped by single-walled and multi-walled carbon nanotubes.

Comparative studies of optical transmission of single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs), dispersed in nematic liquid crystal matrix 5CB, were carried out. The data evidence violations of Beer-Lambert-Bouguer (BLB) law both in cell thickness and concentration dependencies. The most striking is the fact that optical transmission dependencies for SWCNTs and MWCNTs were quite different in the nematic phase, but they were practically indistinguishable in the isotropic phase. Monte Carlo simulations of the impact of aggregation on direct transmission and violation of BLB law were also done. The results were discussed accounting for the tortuous shape of CNTs, their physical properties and aggregation, as well as strong impact of perturbations of the nematic 5CB structure inside coils and in the vicinity of CNT aggregates.

Assessing the effect of food and light on Calanus sinicus swimming behavior through video-recording experiments

The copepod Calanus sinicus is a common and abundant species in the shelf waters of the western North Pacific from Japan to Vietnam, and is a main food source for crucial fish species. This study examined the effect of food and light on the swimming behavior of this species. The swimming activity was assessed by using 2 approaches that focused on the dynamics of swimming states and the statistical properties of their trajectories. We discovered that the complexity of swimming paths was reduced under illuminated conditions, and intensified in the absence of food. The swimming activity in such conditions was characterized by a less tortuous shape of trajectories, a lower instantaneous swimming velocity, and a lower recurrence of extreme events. In addition, the entropy of swimming paths decreased when food was included, and the minimal entropy was reached in dark conditions and presence of food, indicating predictable behavior. A general increase in swimming activity was dominated by the slow swimming state. The variations in the swimming activity of adult females exhibited an adaptive pattern that allowed maximizing the exploitation of the three-dimensional, and generally diluted environment that the copepods inhabit, as well as limiting the risk of the predation.

Mechanical buckling of artery under pulsatile pressure

Tortuosity that often occurs in carotid and other arteries has been shown to be associated with high blood pressure, atherosclerosis, and other diseases. However the mechanisms of tortuosity development are not clear. Our previous studies have suggested that arteries buckling could be a possible mechanism for the initiation of tortuous shape but artery buckling under pulsatile flow condition has not been fully studied. The objectives of this study were to determine the artery critical buckling pressure under pulsatile pressure both experimentally and theoretically, and to elucidate the relationship of critical pressures under pulsatile flow, steady flow, and static pressure. We first tested the buckling pressures of porcine carotid arteries under these loading conditions, and then proposed a nonlinear elastic artery model to examine the buckling pressures under pulsatile pressure conditions. Experimental results showed that under pulsatile pressure arteries buckled when the peak pressures were approximately equal to the critical buckling pressures under static pressure. This was also confirmed by model simulations at low pulse frequencies. Our results provide an effective tool to predict artery buckling pressure under pulsatile pressure.

Use of a pre-positioned guide wire to aid in the removal of a pancreatic duct stent that had migrated further into the duct

Migration of a pancreatic duct stent further into the duct (proximal migration) after implantation is a relatively rare complication [1]. Various pieces of equipment such as a small balloon, snare, forceps, and grasping tripod have been used successfully to extract such stents [2] [3] [4]. However, their removal has proved technically challenging because of the narrow and tortuous shape of the pancreatic duct [2] [4]. This report describes a new method for extraction of a proximally migrated pancreatic duct stent with the help of a pre-positioned guide wire.