Multiple Side Branches Research Articles

Preemptive Embolization of Abdominal Aortic Aneurysm Sac Side Branch Arteries Promotes Early Sac Shrinkage after Endovascular Aneurysm Repair 1

The association between the occlusion rate of the side branch arteries branching from the abdominal aortic aneurysm sac and aneurysm sac shrinkage is unclear. We aimed to evaluate the efficacy of preemptive embolization of multiple side branch arteries branching from the abdominal aortic aneurysm sac in early aneurysm sac shrinkage after endovascular aneurysm repair. Patients undergoing endovascular aneurysm repair of abdominal aortic aneurysms, with or without preemptive embolization of multiple side branch arteries, including the inferior mesenteric artery and lumbar arteries, between January 2016 and August 2021, were retrospectively evaluated. Preemptive embolization was introduced at our institution in January 2018 and has been performed in all patients who undergo endovascular aneurysm repair since then. We compared occlusion rates of the side branch arteries, frequency of type 2 endoleaks, changes in aneurysm sac size, percentage of aneurysm sac size decrease, and frequency of reduction in the aneurysm sac diameter by>5mm. The study included 43 patients in the embolization group and 20 in the nonembolization group. Preemptive embolization was successfully performed without any ischemic complications. The total occlusion rate of side branch arteries was significantly higher in the embolization group than in the nonembolization group (70.2% vs. 29.3%, P<0.05). At 24months of follow-up, the type 2 endoleak frequency was significantly lower in the embolization group than in the nonembolization group (6.9% vs. 31.6%, P<0.05). The frequency of reduction in the aneurysm sac diameter by>5mm was significantly higher in the embolization group than in the nonembolization group at 24months (62.1% vs. 31.6% P<0.05). The optimal cutoff value for the total occlusion rate of the side branch arteries to achieve reduction in the aneurysm sac diameter by>5mm at 24months, after endovascular aneurysm repair, was 66.7% in all patients (area under the curve=0.634; sensitivity=62.5%; specificity=70.8%). These findings suggest that occluding 66.7% or more of the side branch arteries may result in early aneurysmal shrinkage. Preemptive embolization of multiple side branch arteries, branching from the abdominal aortic aneurysm sac, may contribute to early aneurysm sac shrinkage; this may serve as a marker for fewer late complications after endovascular aneurysm repair.

Transient-based multiple branch detection in reservoir pipeline valve systems

Efficient management of pipeline assets is crucial for a reliable urban water supply. Unknown side branches in pipeline systems can hinder the prediction of hydraulic transients, owing to unexpected pressure responses. Herein, we developed a method for detecting multiple side branches in a simple reservoir pipeline valve system. A polynomial-based transient characterization scheme was proposed to address nonlinear valve manoeuvres, which substantially improved the transient simulations over conventional orifice-based approximations. A procedure for pressure signal manipulation via the superimposition of pressure signals with and without branches and isolation of the interference between various branched elements, which distorted the pressure response of multiple branches, was introduced. The model performance was evaluated by comparing the interference-isolated signals obtained from the conventional method, proposed scheme, and experimental datasets. Effective phase matching of the pressure responses obtained via the proposed scheme and experimental data indicated the potential of the former for detecting multiple branches.

Development of a compact device for duct noises

Noise radiated from ducts associated with air conditioning equipment is one of the most important noises that must be addressed to create a quiet space. While it is relatively easy to reduce this noise if the equipment works at a constant frequency, it is difficult to reduce noises of various frequencies being generated depending on changes in its output. Although a side branch is one of the solutions for duct noises, a single side branch can only be effective for a specific frequency. On the other hand, multiple side branches can broaden the effect, However, the space required for side branches becomes very large and is not practical for use. In this study, a compact duct noise reduction device based on the side branch concept is proposed. The side branches of multiple lengths filled with porous materials are considered to achieve both a wide-band reduction and space saving. The design process of the device which can be installed easily is illustrated and the reduction performance are estimated by numerical studies.

Contact of the Tumor with the Internal Mammary Perforator Vessels as Risk Factor for Internal Mammary Lymph Node Involvement Based on Dynamic Contrast Enhancing MRI Imaging in Breast Cancer Patients

Distant metastasis free and overall survival of high-risk breast cancer patients can be improved with irradiation of the lymphatic system. However, inclusion of internal mammary region (IMN) markedly increases the dose to the heart. Hence, an estimation of the individual risk of subclinical involvement is necessary in order to balance the oncological benefit versus the cardiac toxicity. In randomized studies the risk stratification for IMN involvement is mainly based on the tumor location (medial, central vs. lateral). The aim of this study was to evaluate whether the contact of the tumor with the internal mammary perforator vessels (IMPV) is an additional risk factor for IMN involvement. For this trial we retrospectively examined 104 sets of pre-treatment dynamic contrast enhanced magnetic resonance imaging (DE-MRI) scans of locally advanced breast cancer patients. All patients had ipsilateral clinical suspect lymph nodes in the axillary region and either positive (n = 52) or negative lymph nodes (n = 52) in the internal mammary region. Based on the DE-MRI we assessed the tumor location as well as contact to the internal mammary perforating vessels (IMPV). Contact between tumor and IMPV was classified into either predominant, minor or no contact. Criteria for a predominant IMPV contact was defined as: main vessel contact or contact to multiple (> = 5) side branches. The tumor location of IMN+ patients were medial in 19.2% (10/52), central in 26.9% (14/52), lateral in 28.8% (15/52) and multicentric in 25.0% (13/52) of. In IMN- patients, tumor location was medial in 9.6% (5/52), central in 26.9% (14/52), lateral in 42.3% (22/52) and multicentric in 21.2% (11/52) in IMN- patients. The tumor size ranged from T1-T4 with most patients staged as T2 (48.1% (IMN+) vs. 38.5% IMN-). Most patients had hormone receptor positive / Her2neu negative disease (36.5% (IMN+) vs. 46.2% (IMN-). 100 % of tumors in IMN+ patients had contact with IMPV: in 94.2% (49/52) criteria for predominant IMPV contact was fulfilled; in the remaining 3 cases (5.8%) the tumor had minor IMPV contact. In IMN- patients however, 36/52 of cases (69.2%) had direct IMPV contact. Predominant contact was found in only 23.1% (12/52), minor IMPV contact in 46.2% (24/52). Predominant contact of the tumor with IMPV appears to be a potential risk factor for IMN involvement in breast cancer patients and could be used for stratification for IMN-irradiation in future trials.

S1943 An Unusual Liver Tumor

Introduction: Intraductal papillary neoplasm of bile duct (IPNB) is an uncommon premalignant biliary precursor lesion to intrahepatic cholangiocarcinoma (ICC). IPNB can be associated with intraductal papillary mucinous neoplasm (IPMN) of the pancreas. Von Meyenburg complexes (VMCs) have a strong association with hepatic fibro-polycystic liver disease. The association of all these rare entities has not been described, thus lending to the singularity of this case. Case Description/Methods: A 69-year-old-male was referred for a 2-month history of right upper abdominal pain and 10-lb weight loss. CT showed left intrahepatic biliary ductal dilation and scattered small hepatic cysts. ERCP showed dilated left intrahepatic bile ducts with suboptimal brushings. MRI/CP (Figure A) revealed dilated left intrahepatic bile ducts with an abrupt cut off of the left hepatic duct and a subtle area of enhancement concerning for an obstructive malignancy. Multiple small side branch pancreatic IPMNs and many renal cysts were noted (Figure B). Due to concern for malignancy, a left hepatectomy was performed (Figure C). Intraoperatively, multiple cystic lesions were noted throughout the liver. Pathology revealed mucinous intestinal type IPNB with multiple VMCs. Tumor likely arose from a predisposing condition because of multiple VMCs, suggestive of fibro-polycystic liver disease in the non-involved liver. Patient did well post operatively. Discussion: Four histologic types of IPNB have been described including pancreatobiliary, intestinal, gastric foveolar and oncocytic. There are 2 general categories of IPNB based on histologic similarities to their pancreatic counterpart. Type 1 shares many features with pancreatic IPMN. It develops in the intrahepatic bile ducts and is characterized by villous architecture, thin fibrovascular cores and frequent mucin production. Type 2 develops in the extrahepatic bile ducts and has complex papillary, polypoid, tubular, solid or cribriform intraductal structures. IPNB is considered premalignant. VMCs are thought to be a part of embryonic ductal plate malformation. Though largely innocuous, there has been a strong association with hepatic fibro-polycystic liver disease and in rare instances histological transformation to ICC. Prior case reports have tied IPNB to pancreatic IPMN, but this is the first case that associates IPNB, pancreatic IPMN, VMCs and cystic lesions of the liver and kidneys all together. We speculate there could be an underlying common pathological pathway that all these entities share.Figure 1.: a. Dilated left intrahepatic bile ducts with an abrupt cut off of the left hepatic duct. b. IPMN pancreas. c. Left hepatectomy showing tumor.

Breast cancers originating from the major lactiferous ducts and the process of neoductgenesis: Ductal Adenocarcinoma of the Breast, DAB

PurposeTo call attention to a highly fatal breast cancer subtype arising from the major lactiferous ducts that is currently underdiagnosed as ductal carcinoma in situ (DCIS) with or without microinvasion. MethodAll breast cancers diagnosed at the Department of Mammography, Falun Central Hospital, Sweden, since 1977 have been classified according to their mammographic tumour features (imaging biomarkers) and followed up at regular intervals for the past four decades. The imaging biomarkers characteristic of breast cancers apparently arising from the major lactiferous ducts have been correlated with large format thin and thick section histopathology and long-term patient outcome. ResultsBreast cancers arising within the major lactiferous ducts propagate intraductally and produce continuously branching neoducts through epithelial-mesenchymal transformation (EMT), an invasive process termed neoductgenesis, which eventually forms a massive tumour burden. The high fatality of this breast cancer subtype indicates its truly invasive nature, although it is conventionally termed ductal carcinoma in situ, DCIS, terminology which is at odds with its poor long-term patient outcome. The neoducts are filled with multiple layers of malignant cells, have no attached lobules, and propagate by forming multiple invasive side branches. These newly formed duct-like structures are surrounded by a desmoplastic reaction (cancer associated fibroblasts, CAFs) and periductal lymphocytic infiltration. The neoducts are tightly packed together in irregular formations bearing no resemblance to the paniculate branching structure of normal lactiferous ducts. Cancers originating from the major ducts have six imaging biomarkers which can be easily recognized at breast imaging. These are described in detail in an accompanying article. ConclusionsNeoductgenesis in the breast, DAB, is similar in appearance and prognosis to ductal adenocarcinoma of the prostate, DAP. We propose the term ductal adenocarcinoma of the breast, DAB, to facilitate its recognition as a distinct invasive breast cancer subtype. The high fatality rates associated with neoductgenesis reflect the failure of current histopathologic diagnostic criteria to effectively guide therapeutic practice. When the neoducts are associated with small stellate/spiculated or spherical/oval-shaped invasive cancers arising from the terminal ductal lobular units (TDLUs), the prognosis and management are erroneously estimated according to the smaller invasive tumour(s), giving a false sense of security often resulting in undertreatment. Recognition that neoductgenesis is an invasive malignancy is a prerequisite for preventing treatment failure.

Superficial Temporal Artery True Fusiform Aneurysm With Several Lateral Feeding Vessels

A 49-year-old man flight attendant with a past medical history of Roux-en-Y bypass and massive weight loss 18 months prior was referred for surgical management of a superficial temporal artery aneurysm. Imaging confirmed the diagnosis. Intraoperatively a 1 cm fusiform aneurysm was identified with numerous feeding side branch vessels. The aneurysm was suture ligated and excised in toto with pathologic analysis showing involvement of all vessel layers. This case highlights a rare true aneurysm of the superficial temporal artery and aberrant anatomy of multiple side branches feeding the aneurysm and complicating dissection and excision.

Long-term outcomes of wide-necked intracranial bifurcation aneurysms treated with T-stent-assisted coiling.

The endovascular treatment of complex bifurcation aneurysms possessing a neck that incorporates multiple side branches remains a surgical challenge. Double-stent-assisted coiling techniques, such as those with stents in an X and Y configuration, enable the endovascular treatment of wide-necked complex intracranial bifurcation aneurysms. However, the intraluminal struts at the intersection point in X- and Y-stents are not amenable to endothelialization, which may lead to thromboembolic complications. Stenting in the T configuration is a relatively new double-stent coiling technique. T-stenting differs from X- or Y-stenting in that there are no overlapping or intersecting stent segments. Promising short-term results of T-stent-assisted coiling were recently reported. However, the long-term results have not yet been demonstrated. This retrospective study investigated the long-term angiographic and clinical results in patients with wide-necked complex intracranial bifurcation aneurysms treated with T-stent-assisted coiling. A retrospective review was performed to identify patients with wide-necked complex intracranial bifurcation aneurysms treated with T-stent-assisted coiling at 4 institutions. The technical success and the initial and follow-up clinical and angiographic outcomes were assessed. Aneurysm filling status was assessed according to the Raymond classification. Periprocedural and delayed complications were reviewed. The neurological status of the patients was evaluated using the modified Rankin Scale (mRS). One hundred two aneurysms in 102 patients (54 females), whose mean age was 57.9 ± 13.0 years, were included in the study. T-stenting was performed successfully in all patients. Immediate postprocedural angiography revealed complete occlusion in 83.3% of patients. Periprocedural complications developed in 13.7%, resulting in permanent morbidity in 1.9% and death in 1%. Eighty patients (78.4%) had at least one follow-up DSA examination performed at 6 months or later following the endovascular procedure. The mean duration of angiographic follow-up was 30.0 ± 16.3 months. The last follow-up examinations showed complete occlusion in 90.0% of patients. During the follow-up period, only 1 patient (1.3%) required retreatment. Delayed thromboembolic complications were observed in 4 patients (3.9%) without permanent morbidity. The mRS scores of all patients at the last clinical follow-up were between 0 and 2. The short-term angiographic findings showed that T-stent-assisted coiling is a feasible and effective endovascular method to treat wide-necked complex bifurcation aneurysms. The long-term angiographic follow-up results suggest that T-stent-assisted coiling provides a durable treatment for wide-necked complex bifurcation aneurysms with favorable clinical outcomes, demonstrating the long-term safety of T-stent-assisted coiling.

Information theory to tachycardia therapy: electrogram entropy predicts diastolic microstructure of reentrant ventricular tachycardia.

There is no known strategy to differentiate which multicomponent electrograms in sinus rhythm maintain reentrant ventricular tachycardia (VT). Low entropy in the voltage breakdown of a multicomponent electrogram can localize conditions suitable for reentry but has not been validated against the classic VT activation mapping. We examined whether low entropy in a late and diversely activated ventricular scar region characterizes and differentiates the diastolic path of VT and represents protected tissue channels devoid of side branches. Intraoperative bipolar electrogram (BiEGM) activation and entropy maps were obtained during sinus rhythm in 17 patients with ischemic cardiomyopathy and compared with diastolic activation paths of VT (total of 39 VTs). Mathematical modeling of a zigzag main channel with side branches was also used to further validate structural representation of low entropy in the ventricular scar. A median of one region per patient (range: 1-2 regions) was identified in sinus rhythm, in which BiEGM with the latest mean activation time and adjacent minimum entropy were assembled together in a high-activation dispersion region. These regions accurately recognized diastolic paths of 34 VTs, often to multiple inducible VTs within a single individual arrhythmogenic region. In mathematical modeling, side branching from the main channel had a strong influence on the BiEGM composition along the main channel. The BiEGM obtained from a long unbranched channel had the lowest entropy compared with those with multiple side branches. In conclusion, among a population of multicomponent sinus electrograms, those that demonstrate low entropy and are delayed colocalize to critical long-protected channels of VT. This information is pertinent for planning VT ablation in sinus rhythm. NEW & NOTEWORTHY Entropy is a measure to quantify breakdown in information. Electrograms from a protected tissue channel can only possess a few states in their voltage and thus less information. In contrast, current-load interactions from side branches in unprotected channels introduce a number of dissimilar voltage deflections and thus high information. We compare here a mapping approach based on entropy against a rigorous reference standard of activation mapping during VT and entropy was assessed in sinus rhythm.

PC102. Side Branch Ligation Improves Function of Arteriovenous Fistula

Arteriovenous fistulae (AVF) for hemodialysis are plagued by a high rate of initial functional failure. Although thrombosis is a common etiology, some AVF may fail owing to flow diversion into side branches. We hypothesized that eliminating these side branches would improve flow in nonmaturing AVF and increase functional patency. Nonmaturing AVF were reviewed retrospectively; thrombosed AVF were excluded. AVF were initially assessed at 6 weeks by duplex ultrasound imaging and those with large (>3 mm) or multiple (1-6) side branch(es) were identified for ligation/coiling. Duplex ultrasound imaging assessed vein diameters, outflow, inflow, patency, and flow volumes. Duplex ultrasound imaging compared immediate patency before and after this intervention. Between 2010 and 2017, we identified 34 patients; 79% were male with ages ranging from 26 to 81 years. Complete hemodynamic data were available for 27 subjects. Average time from fistula construction to side branch ligation was 111 days. Branch flow was controlled by ligation in 30 of the 34 (88%) or coil embolization 4 of the 34 (12%). Diameter increased by an average of 0.85 mm from 5.5 to 6.4 mm (P < .001). Average flow increased 516 mL/min. Flow volumes increased 96% from 646 to 1162 mL/min (P < .01; Table). Of the 34 AVF, 31 (91%) achieved functional patency. Three did not attain functional patency owing to expiration before use, anastomotic stenosis, and thrombosis. Side branch ligation improves functional patency in nonmaturing AVF. This may be due to increased AVF vein diameter and/or flow volume.TableChanges in diameter and flow volumeNumberPreligationPostligationChangePDiameter (mm)255.56.40.85<.001Flow volume (mL/min)276461162516<.01 Open table in a new tab

Development of Time- and Voltage-Domain Mapping (V-T-Mapping) to Localize Ventricular Tachycardia Channels During Sinus Rhythm.

In ventricular scar, impulse spread is slow because it traverses split and zigzag channels of surviving muscle. We aimed to evaluate scar electrograms to determine their local delay (activation time) and inequality in voltage splitting (entropy), and their relationship to channels. We reasoned that unlike innocuous channels, which are often short with multiple side branches, ventricular tachycardia (VT) supporting channels have very slow impulse spread and possess low entropy because of their longer protected length and relative lack of side-branching. Patients with ischemic cardiomyopathy and multiple VT were studied. In initial mapping stage (16 patients and 58 VTs), left ventricular endocardial mapping was performed in sinus rhythm. Detailed pace mapping was used to identify VT channels and confirmed, when feasible, by entrainment. Scar electrograms were analyzed in time and voltage domains to determine mean activation time, dispersion in activation time, and entropy. Predictive performances of these properties to detect VT channels were tested. In the application stage (7 patients and 20 VTs), these properties were prospectively tested to guide catheter ablation. A mean number of 763±203 sampling points were taken. From 1770 pace maps, 47 channels corresponded to VTs. A combination of scar electrograms with the latest mean activation time and minimum entropy, in a high activation dispersion region, accurately recognized regions containing VT channels (κ=0.89, sensitivity=86%, specificity=100%, positive predictive value=93%, and negative predictive value=100%). Finally, focused ablation within 5-mm rim of the prospective channel regions eliminated 18 of 20 inducible VTs. Activation time and entropy mapping in the scar accurately identify VT channels during sinus rhythm. The method integrates principles of reentry formation to recognize VT channels without pace mapping or mapping during VT.

49-05: Defining arrhythmogenic ventricular scar using time- and voltage-domain mapping (V-T-mapping): a new approach to ventricular tachycardia channel localization during sinus rhythm

Aims: In ventricular scar, the impulse spread is slow as it traverses multiple split and zigzag channels of surviving muscle. We aimed to evaluate electrograms in the scar to determine their local delay in relation to the onset of ventricular activation (activation time) and inequality in voltage splitting (entropy), and their relationship to channels. We reasoned that unlike innocuous bystander channels, which are often short with multiple side branches, ventricular tachycardia (VT) supporting channels have very slow impulse spread and possess low entropy due to their longer protected length and relative lack of side branching. Methods: Patients with ischemic cardiomyopathy and multiple inducible VT were studied. In the initial mapping stage (16 patients, 58 VTs), left ventricular endocardial mapping was performed in sinus rhythm. Detailed pace mapping was used to identify VT channels, and confirmed, when feasible, by entrainment. The scar electrograms were analyzed in time- and voltage-domains to determine mean activation time, dispersion in activation time and entropy. The predictive performances of these properties to detect VT channels were tested. In the application stage (7 patients, 20 VTs), these properties were prospectively tested to guide catheter ablation. Results: A mean of 763 ± 203 sampling points per-patient were taken, 451 ± 145 points in dense scar. From 1770 pace maps, 174 channels were identified, and 47 corresponded to inducible VTs. A combination of scar electrograms with the latest mean activation time and minimum entropy, in a high activation dispersion region, accurately recognized regions containing VT channels (kappa = 0.89, sensitivity = 86%, specificity = 100%, positive predictive value = 93%, and negative predictive value = 100%). Finally, focused ablation within the prospective channel regions eliminated 18/20 inducible VTs. Conclusion: Activation time and entropy mapping in the scar accurately identifies VT channels during sinus rhythm. This can expedite recognition of VT channels without pace mapping or mapping during VT and minimize extensive ablation.

An assessment of intra-patient variability on observed relationships between wall shear stress and plaque progression in coronary arteries.

BackgroundWall shear stress (WSS) has been associated with sites of plaque localization and with changes in plaque composition in human coronary arteries. Different values have been suggested for categorizing WSS as low, physiologic or high; however, uncertainties in flow rates, both across subjects and within a given individual, can affect the classification of WSS and thus influence the observed relationships between local hemodynamics and plaque changes over time. This study examines the effects of uncertainties in flow rate boundary conditions upon WSS values and investigates the influence of this variability on the observed associations of WSS with changes in VH-IVUS derived plaque components.MethodsThree patients with coronary artery disease underwent baseline and 12 month follow-up angiography and virtual histology-intravascular ultrasound (VH-IVUS) measurements. Coronary artery models were reconstructed from the data and models with and without side-branches were created. Patient-specific Doppler ultrasound (DUS) data were employed as inflow boundary conditions and computational fluid dynamics was used to calculate the WSS in each model. Further, the influence of representative coronary artery flow waveforms upon WSS values was investigated and the concept of treating WSS using relative, rather than actual, values was explored.ResultsModels that included side-branch outflows and subject-specific DUS velocities were considered to be the reference cases. Hemodynamic differences were caused by the exclusion of side-branches and by imposing alternative velocity waveforms. One patient with fewer side-branches and a scaled generic waveform had little deviation from the reference case, while another patient with several side-branches excluded showed much larger departures from the reference situation. Differences between models and the respective reference cases were reduced when data were analyzed using relative, rather than actual, WSS.ConclusionsWhen considering individual subjects, large variations in patient-specific flow rates and exclusion of multiple side-branches in computational models can cause significant differences in observed associations between plaque evolution and ranges of computed WSS. These differences may contribute to the large variability typically found among subjects in pooled populations. Relative WSS may be more useful than actual WSS as a correlative variable when there is a large degree of uncertainty in flow rate data.

Designing Cell Walls for Improved Bioenergy Production

Dwindling supply and unpredictable price fluctuations of fossil fuels have necessitated a renewed worldwide search for alternative fuels. Plant cell walls, rich in cellulose and hemicellulose, are actively pursued for their use in production of second-generation biofuels. It has been envisioned that degradation of these carbohydrate polymers to their sugar monomer subunits (saccharification) will provide necessary substrates for their yeast-mediated fermentation to ethanol. But the major component of plant cell walls, cellulose, is not easily amenable to this type of deconstruction and is tightly interlinked with hemicelluloses and lignin, making cell walls highly recalcitrant to saccharification.

Covered self-expanding metal stent use in the pancreatic duct: a case series

Plastic stents have been used in the pancreatic duct for a variety of indications. However, unlike in the bile duct, the use of covered self-expanding metal stents (CSEMSs) has been discouraged because multiple side branches drain into main pancreatic duct (MPD) and the ductal diameter is relatively small. This report aims to describe our experience using CSEMSs in the pancreatic duct in a series of nine patients, with special focus on adverse events. Indications were strictures (n = 5), intraductal mucinous neoplasm (IMPN; n = 1), pancreatic duct leak (n = 1), disconnected duct syndrome (n = 1), and severe acute pancreatitis/necrosis with disrupted duct (n = 1). Eight patients had symptomatic improvement, or radiological resolution of or improvement in their strictures, leaks, perforation, and necrosis. Two of these have indwelling CSEMSs for ongoing treatment. One patient (disconnected duct syndrome) was considered a treatment failure as the stent migrated and the patient underwent distal pancreatectomy for refractory pain. Two patients underwent pancreaticoduodenectomy for their malignancies after their CSEMSs had been in place for 43 and 49 days, respectively. Importantly no patients, including those with indwelling CSEMSs, developed stent-related acute pancreatitis with a median follow-up of 4 months. One patient developed post-procedure pain requiring hospitalization for 1 day. Median stent duration was 77 days. These observations suggest there is a potential role for the use of CSEMSs in the MPD in selected patients with pancreatic pathology.

Flow-induced acoustic resonance at the mouth of one or two side branches

► We investigated the effect of the geometrical and flow parameters on the flow-induced acoustic resonance. ► In the case of a single branch, the dimensionless acoustic pressure amplitude at resonance increases as the cross-sectional ratio of the main and branch pipes is decreased. ► In the case of coaxial branches, the pressure amplitude shows a counter tendency to that in the case of a single branch. ► In the case of tandem branches, peak pressure and frequency change cyclically as the distance between tandem branches changes. In the case of flow-induced acoustic resonance with multiple side branches, the pulsation amplitude may be significantly enhanced compared to the case of a single branch. However, few studies have been presented on the effects of the distance between tandem branches or side branches on fluctuating pressure amplitude. In this study, we carried out several air flow experiments at ordinary temperatures and pressures to investigate the effect of the geometrical and flow parameters on the general acoustic resonance. In the case of a single branch, the dimensionless acoustic pressure amplitude at resonance increases as the cross-sectional ratio of the main and branch pipes is decreased. This is attributed to the acoustic radiation loss from the branch pipe to the main pipe increasing at higher values of the cross-sectional ratio. In the case of coaxial branches, the pressure amplitude shows a counter tendency to that in the case of a single branch. This is because the two branches strongly couple and form a standing wave with negligible radiation losses. In the case of tandem branches, peak pressure and frequency change cyclically as the distance between tandem branches changes.

Self-sustained oscillations in pipe systems with multiple deep side branches: Prediction and reduction by detuning

Flow-induced pulsations are frequently observed in pipe networks. In the present work we focus on the case of flow-induced pulsations in a pipe system composed of six equally spaced deep closed side branches. These pulsations are self-sustained aeroacoustic oscillations driven by the instability of the flow along the closed branches. The prediction of pulsations in such complex systems has not yet been proved to be possible, indeed the methods proposed in the literature have only been applied to relatively simple geometries, mainly single or double side branch systems. We propose a prediction model of the self-sustained oscillations in multiple deep side branch systems. This has been established by means of an analytical model for the acoustic wave propagation in which a semi-analytical source model is included. Detuning of the acoustic resonator is often considered as a possible remedial measure to suppress pulsations. Although this countermeasure appears to be very effective for double side branch systems in cross configuration, its effectiveness has never been assessed for different geometries. The effectiveness of the length-detuning on the six side branch system appear to be limited and depends on the upstream and downstream acoustic boundary conditions of the main pipe.

On the whistling of corrugated pipes: effect of pipe length and flow profile

Whistling behaviour of two geometrically periodic systems, namely corrugated pipes and multiple side branch systems, is investigated both experimentally and numerically. Tests are performed on corrugated pipes with various lengths and cavity geometries. Experiments show that the peak-whistling Strouhal number, where the maximum amplitude in pressure fluctuations is registered, is independent of the pipe length. Experimentally, a decrease of the peak-whistling Strouhal number by a factor of two is observed with increasing confinement ratio, i.e. the ratio of pipe diameter to cavity width. A numerical methodology that combines incompressible flow simulations with vortex sound theory is proposed to estimate the acoustic source power in periodic systems. The methodology successfully predicts the Strouhal number ranges of acoustic energy production/absorption and the nonlinear saturation mechanism responsible for the stabilization of the limit cycle oscillation. The methodology predicts peak-whistling Strouhal numbers in agreement with experiments and explains the dependence of the peak-whistling Strouhal number on the confinement ratio. Combined with an energy balance, the proposed methodology is used to estimate the acoustic fluctuation amplitudes.

Whistling behavior of periodic systems: Corrugated pipes and multiple side branch system

Whistling behavior of two geometrically periodic systems are investigated: corrugated pipes and a multiple side branch system. In both systems frequency (Helmholtz number) is a non-decreasing piecewise constant function of the Mach number, whose increase on average is approximately linear. The plateaus, lock-in frequencies, of this piecewise constant function correspond to the longitudinal acoustic pipe modes. In both systems pressure fluctuation amplitude changes non-monotonically with Mach number with local maxima that correspond to the lock-in frequencies. A characteristic length, equal to cavity width plus upstream edge radius, yields the smallest discrepancy in the measured peak whistling Strouhal number for both corrugated pipes and multiple side branch system. For both systems the upstream edge radius of the cavity has a strong effect on pressure fluctuation amplitudes. Whistling amplitudes increase by a factor of 3–5 upon rounding off the upstream cavity edges. The radius of the downstream edge has a less pronounced effect on the sound amplitude and frequency. The geometric parameters of the multiple side branch system can easily be modified. This makes the multiple side branch system a convenient tool for making experiments on the effects of various geometric parameters. A number of aspects are addressed with the multiple side branch system such as the effect of pipe termination geometry, source localization, side branch depth to diameter ratio, a gradient in depth along the pipe and hysteresis upon change in the acceleration or deceleration of the flow.

Whistling of a pipe system with multiple side branches: Comparison with corrugated pipes

Corrugated pipes are widely used because they combine local rigidity with global flexibility. Whistling induced by flow through such pipes can lead to serious environmental and structural problems. The whistling of a multiple side branch system is compared to the whistling behavior of corrugated pipes. The study has been restricted to cavities with sharp edges which are convenient for theoretical modeling. The side branch depth is chosen to be equal to the side branch diameter, which corresponds to cavity geometries in typical corrugated pipes. The low frequency resonance modes of the multiple side branch system have been predicted by means of acoustic models, of which the validity has been tested experimentally. Several experiments have been carried out for characterizing the whistling behavior of the system. While the behavior of a multiple side branch system is interesting on its own it can be compared to that of corrugated pipes. These experiments show that the multiple side branch system is in many aspects a reasonable model for corrugated pipes. Advantage of the multiple side branch system is that it is an experimental setup allowing easy modification of cavity depth. We used this feature to identify the pressure nodes of the acoustic standing wave along the main pipe as the regions where sound is produced. This contradicts recent publications on corrugated pipes. Another interesting aspects is that the system appears to whistle at the second hydrodynamic mode of the cavities rather than at the first hydrodynamic mode. A prediction model for the whistling behavior is proposed, consisting of an energy balance, based on the vortex sound theory. The model predicts the observed Strouhal number but overestimates the acoustic fluctuation amplitude by a factor four. © 2009 Elsevier Ltd. All rights reserved.