Evaluation Of Flow Patterns Research Articles

Saturated/subcooled flow boiling heat transfer characteristics for R134a, HFE-7100 and Deionized water inside micro/mini-channels: Part I - Visualization of flow patterns and new diabatic two-phase flow pattern transition regimes

An experimental investigation on flow saturated/subcooled flow boiling heat transfer for R134a, HFE-7100 and Deionized water inside micro/mini-channels (L/dh = 40/53/70) was presented. Flow patterns and their transitions of three working fluids at various liquid subcoolings (0 ∼ 70 K) were visualized and analyzed. Experiments were carried out at a saturated pressure of 770 kPa for R134a and at atmospheric pressure for HFE-7100 and Deionized water. The mass flux varied from 400 to 800 kg/m2s, and heat fluxes up to 270.1 W/cm2 over the entire range of vapor quality (0 ∼ 1). The effects of mass flux, heat flux, liquid subcoolings and geometry parameters on flow pattern evaluation and transition were discussed. Bubble (isolated and confined bubbles), slug, churn, annular and dry-out flows were observed for the micro/mini-channels. The results indicated that the flow patterns have a significant difference on flow boiling under different liquid subcoolings. There is obvious flow pattern transition from slug flow to annular flow for nearly saturated boiling (ΔTsub ≤ 10 K). However, with the increase of inlet liquid subcooling, only obvious bubble flow and slug flow were observed during the entire boiling process, and the annular flow was not obvious before triggering the CHF. Besides, the flow pattern transition criterion is modified and the new flow pattern transition regimes including saturated/subcooled flow boiling for different working fluids are developed based on present experimental results.

Heat transfer characteristics and operational visualization of two-phase loop thermosyphon

The advantages of high-efficiency and pumpless long-distance heat transport make the two-phase loop thermosyphon (TPLT) a promising candidate for various energy- and thermal-related applications. In this work, the simultaneous temperature/pressure measurement and high-speed visualization observation were conducted to compare and evaluate the heat transfer performance and two-phase flow characteristics of a vertical-positioned TPLT having an inner diameter of 10 mm. R141b was used as the working fluid at volumetric filling ratios of 35–50 %. The TPLT functioned well and had high heat transfer capacity at relatively high filling ratios (⩾ 40 %), while it failed to operate at a low filling ratio of 35 % under the power inputs greater than 250 W due to the local dry-out. A maximum effective thermal conductivity of 2.0 × 105 W/(m·K) was achieved at the optimal filling ratio of 40 %. Further, a flow regime map was developed to identify the combination effect of filling ratio and heat power on the flow pattern evaluation and two-phase flow instability. The geyser boiling usually manifests itself as an alternation of two or even three flow patterns, and tends to occur at the combination conditions of relatively low filling ratios (35 % and 40 %) and low heat powers or a moderate filling ratio (50 %) and relatively high heat powers. Additionally, the white mist phenomena caused by the flash vaporization was observed in the riser at relatively higher power inputs. The liquid-vapor mixture flow in the riser would partially degrade the TPLT performance due to the inhibition of vapor condensation in the condenser region. This study provides new insight into the operation characteristics of TPLT and gives guidelines for proper design and applications.

Quantification of paravalvular leaks associated with TAVI implants using 4D MRI in an aortic root phantom made possible by the use of 3D printing.

Transcatheter aortic valve implantation (TAVI) has become an alternative to surgical replacement of the aortic valve elderly patients. However, TAVI patients may suffer from paravalvular leaks (PVL). Detecting and grading is usually done by echocardiography, but is limited by resolution, 2D visualization and operator dependency. 4D flow magnetic resonance imaging (MRI) is a promising alternative, which did not reach clinical application in TAVI patients. The aim of this study was applying 3D printing technologies in order to evaluate flow patterns and hemodynamics of PVLs following TAVI, exploiting 4D flow MRI and standard ultrasound. An MR-compatible, anatomically left ventricle, aortic root, and ascending aorta model was fabricated by combining 3D-printed parts and various soft silicone materials to match physiological characteristics. An Abbott Portico™ valve was used in continuous antegrade flow (12-22 l/min), retrograde flow with varying transvalvular pressures (60-110 mmHg), and physiological pulsatile hemodynamics (aortic pressure: 120/80 mmHg, cardiac output: 5 l/min) Time-resolved MR measurements were performed above and below the TAVI stent and compared with color Doppler ultrasound measurements in exactly the same setup. The continuous antegrade flow measurements from MRI largely agreed with the flowmeter measurements, and a maximum error of only 7% was observed. In the retrograde configuration, visualization of the paravalvular leaks was possible from the MR measurements, but flow was overestimated by up to 33%. The 4D MRI measurement in the pulsatile setup revealed a single main PVL, which was also confirmed by the color Doppler measurements, and velocities were similar (2.0 m/s vs. 1.7 m/s). 4D MRI techniques were used to qualitatively assess flow in a patient-specific, MR-compatible and flexible model, which only became possible through the use of 3D printing techniques. Flow patterns in the ascending aorta, identification and quantification of PVLs was possible and the location and extent of PVLs were confirmed by ultrasound measurements. The 4D MRI flow technique allowed evaluation of flow patterns in the ascending aorta and the left ventricle below the TAVI stent with good results in identifying PVLs, demonstrating its capabilities over ultrasound by providing the ability to visualize the paravalvular jets in three dimensions at however, additional expenditure of time and money.

Evaluation of flow patterns in vertical slot fishways with different slot positions based on a comparison passage experiment for juvenile grass carp

Flow patterns (FPs) are different due to different fishway structures and different boundary conditions in a river. FPs can greatly affect fish passage efficiency along the entire fishway. In this study, experimental hydraulic modelling is combined with the study of fish behavior in a physical model of a vertical slot fishway (VSF) with different slot positions and varying pool lateral baffle length (P) to width (B) ratios. A three-dimensional (3D) computational fluid dynamics (CFD) model is used to help understand the detailed hydraulic structures. Three distinct FPs are studied. When P/B < 0.2 and a short baffle was used, the principal flow was along the side wall with almost no curve to the next slot, and this was termed FP1. When 0.2 < P/B < 0.34 and a medium size baffle was used, the principal flow was in the center position. Hence, the principal flow leaving the slot entered the pools as a curved jet that dispersed into the pool center before converging again towards the next slot, and this was termed FP2. When P/B > 0.4 and a long baffle was used, the jet had a curved form along the opposite side wall, and this was termed FP3. Comparison experiments are conducted on the three FPs, and 82 to 90 trials are conducted to compare juvenile grass carp (Ctenopharyngodon idella) reactions to each FP. An analysis of the fish behavior in the model clearly demonstrated that the fish tended to need less time to pass in FP2 than in the other two FPs. FP2, with the principal flow in the center position, tended to be more suitable for fish migration. In addition, using an analysis of the less efficient FPs, it was found that the velocity gradient may act as an important migration behavior motivator, and that a recirculation zone too close to the downstream slot could increase the risk of downstream flush. It is suggested that further studies should investigate the behaviors of different fish species in the three typical FPs.

Friction stir welding of dissimilar stainless steels: evaluation of flow pattern, microstructure and mechanical properties

The friction stir welded joints of austenitic and ferritic stainless steels were implemented at different rotational speeds 700∼900 rpm. The results indicated that the heat input and the material flow in welded zone were improved with increasing rotational speed, and the nugget zone presented blocky, laminated and vortex structure of austenite and ferrite. The joining mechanism transformed from simple mechanical mixing to combination of mechanical and metallurgical connections, proved by the Ni element diffusion at the interface of austenite and ferrite matrix. A reliable joint with the maximum tensile strength was achieved by two-phase laminated structure performed at rotational speed 800 rpm. The fracture occurred in the thermo-mechanically affected zone on the advancing side. The grains of the stir zone were refined from 20 μm to 2 μm by dynamic recrystallization.

Evaluation of Flow Pattern in the Ascending Aorta in Patients with Repaired Tetralogy of Fallot Using Four-Dimensional Flow Magnetic Resonance Imaging.

ObjectiveTo evaluate flow pattern characteristics in the ascending aorta (AA) with four-dimensional (4D)-flow MRI and to determine predictors of aortic dilatation late after tetralogy of Fallot (TOF) repair.Materials and MethodsThis study included 44 patients with repaired TOF (25 males and 19 females; mean age, 28.9 ± 8.4 years) and 11 volunteers (10 males and 1 female, mean age, 33.7 ± 8.8 years) who had undergone 4D-flow MRI. The aortic diameters, velocity, wall shear stress (WSS), flow jet angle (FJA), and flow displacement (FD) at the level of the sinotubular junction (STJ) and mid-AA were compared between the repaired TOF and volunteer groups. The hemodynamic and clinical parameters were also compared between the aortic dilatation and non-dilatation subgroups in the repaired TOF group.ResultsThe diameters of the sinus of Valsalva, STJ, and AA were significantly higher in the repaired TOF group than in the volunteer group (p = 0.002, p < 0.001, and p = 0.013, respectively). The FJAs at the STJ and AA were significantly greater in the repaired TOF group (p < 0.001 and p = 0.003, respectively), while velocities and WSS parameters were significantly lower. FD showed no statistically significant difference (p = 0.817). In subgroup analysis, age at TOF repair was significantly higher (p = 0.039) and FJA at the level of the AA significantly greater (p = 0.003) and mean WSS were significantly lower (p = 0.039) in the aortic dilatation group. FD were higher in the aortic dilatation group without statistical significance (p = 0.217).ConclusionPatients with repaired TOF have an increased FJA, dilated AA, and secondarily decreased WSS. In addition to known risk factors, flow eccentricity may affect aortic dilatation in patients with repaired TOF.

Fluidumok, áramlási rendszerek és ásványtani lenyomataik összefüggései a Budai Termálkarszton

A Budai Termálkarszt (BTK) fluidum-fejlődéstörténetét az ásványparagenezisek tükrében a késő-miocén fedett karbonátos állapottól vizsgáltuk. Ekkor a termikus felhajtóerő vezérelte a felszínalatti vízáramlást. Később, a Budai-hegység kiemelkedésével és a csapadékvíz beszivárgásával megkezdődött a vízszint különbségek által vezérelt vízáramlási rendszerek kialakulása. További változást okozott a Gödöllői-dombság kiemelkedése, mely a Budai-hegység kiemelt területei mellett a keleti medencerész felől is domborzati hajtóerőt biztosított. A meginduló beszivárgás lehetővé tette a fedő sziliciklasztos képződmények nátrium-kloridos vizeinek karbonátos víztartóba történő lejutását. Jelenleg a Budai-hegység és tágabb környezete a BTK áramlási rendszerének nyugati félig fedett részét, míg a Gödöllői-dombságtól a Dunáig tartó terület a rendszer keleti, fedett részét képezi. A BTK összefüggő áramlási rendszerében hidrosztatikus közeli nyomásviszonyok uralkodnak. A rendszer regionális és köztes megcsapolódási területei a Duna mentén húzódnak. A helyi, köztes és regionális áramlási rendszerek különbségeit a nyugati, félig fedett terület forrásai jelzik. A jelenkori vízáramlás domináns hajtóereje a vízszintkülönbségekből fakad, asszimmetrikus jellege a hidrosztratigráfiai helyzet, valamint a keleti és nyugati medencerészek közötti beszivárgáskülönbség következménye. A Duna alatt Ny­–K irányú regionális átáramlás zajlik. A regionális feláramlás hidrotermális komponense NaCl-os medenceeredetű vízzel egészül ki. A meteorikus eredetű, langyos köztes, ill. a hideg helyi vízáramlásokban Mg2+ és SO42- gazdag vizek jellemzőek, a medenceeredtű fluidomok jelenléte itt nem bizonyított. Az eredmények rámutatnak a rendszer hőmérsékleti eloszlását meghatározó folyamatokra, valamint a fedőüledékek hő felhalmozódásában betöltött szerepére. A rózsadombi és a Gellért-hegy előterében található források fizikai-kémiai tulajdonságok szerinti elkülönülését szerkezeti és a két áramlási rendszer különbségei okozhatják. A Gellért-hegynél csak termálvíz lép felszínre, míg a Rózsadombnál langyos és termálvíz megcsapolódás egyaránt zajlik. A különbség a hidrotermális vizek összetételében, eltérő forrásterületre és vízkémiai folyamatokra utal. A déli rendszer szulfát-többlete az evaporit összletekkel, a központi rendszer szulfátja medenceeredetű kén-hidrogénnel hozható összefüggésbe. A rózsadombi langyos meteorikus vizek szulfát forrása a fedő képződménybek piritje lehet. A fluidum-fejlődéstörténeti tanulmány eredményei hozzájárulnak a barlangképződési folyamatok értelmezéséhez.

Flow Structure on Nonslender Delta Wing: Reynolds Number Dependence and Flow Control

The flow structure over a 35 deg swept delta wing is characterized in a low-speed wind tunnel using techniques of laser-illuminated smoke visualization, laser Doppler anemometry, and surface-pressure measurements. The effects of Reynolds numbers and attack angles on the evaluation of flow patterns are addressed within the broad range of Reynolds number and attack angle . In addition, the effect of steady blowing through the leading edges of the wing on flow structure is studied to delay three-dimensional surface separation. A comparison of two different blowing patterns, uniform blowing and decreasing blowing, is used to identify the effective regions on leading edges considering the ultimate influence of flow control. The results indicate that the effect of Reynolds number on flow structure is limited, such that beyond a certain Reynolds number, the flow structure demonstrates minimal variations with further increase in Reynolds number. Considering the results of the flow-control study, steady blowing through leading edge significantly alters the flow structure, and is quite effective in the eradication of three-dimensional surface separation. The decreasing-blowing pattern compared to uniform blowing seems to be more efficient on the overall flow structure, indicating that control through leading edge near the apex region is more effective.

In vitro evaluation of flow patterns and turbulent kinetic energy in trans-catheter aortic valve prostheses

In vitro evaluation of flow patterns and turbulent kinetic energy in trans-catheter aortic valve prostheses

Analysis of Flow Field for Link Rod Butterfly Valve

The link rod butterfly valve relies on the link mechanism inside the flow channel to realize opening. The flow within flow channel is complex and the flow state is uncertain, so that pressure load of the flow part can't be determined in the butterfly valve designing, and strength of the parts can’t be calculated accurately and the thrust of the hydraulic cylinder can't be determined accurately. Therefore, it is necessary to carry out flow field analysis. In this paper, by adopting the plug-in COSMOSMotion of Solidworks software, the link rod butterfly valve with DN1800 is carried on motion simulation, determining the specific opening. And then the butterfly valve at different opening is carried out the finite element analysis of the flow field, adopting the plug-in COSMOSFloworks of Solidworks of software. The result shows that: the force is the largest when the valve plate is in just opening, it is 230731N, the strength analysis of the flow part and selection of the hydraulic cylinder should be based on the working condition; When full opening, the upward force on the valve plate is 18504N, this force is the power source when the valve plate is over opening. The above mentioned work provides a reliable theoretical basis for the strength calculation and the force and energy parameters calculation of the link rod butterfly valve and the theoretical reference for flow pattern evaluation of the link rod butterfly valve.

Bead-flow pattern: Quantitation of fluid movement during torsional and longitudinal phacoemulsification

To develop a bead-flow pattern for visualizing and comparatively quantifying fluid movement using a torsional or longitudinal ultrasound (US) phaco handpiece. Magill Laser Center, Medical University of South Carolina, Charleston, South Carolina, USA. Visualization and quantification of intraocular fluid dynamics were evaluated by injecting neutrally buoyant, collagen-coated polystyrene beads (diameter, 125 to 212 microm) into the phacoemulsification irrigation flow. Using the anterior chamber of a cadaver or porcine eye or a laboratory test chamber, the bead-flow pattern was video recorded. Qualitative comparisons between longitudinal and torsional phacoemulsification were made using video-processing software to track the beads frame by frame. The time (quantitative) required to aspirate a bolus of beads from the anterior chamber (clearance time) was measured and compared between the 2 modalities. Aspiration efficiency was calculated to compare operating conditions in a test chamber using high-speed videography; conditions included irrigation/aspiration (I/A) only (0% power) and clinically relevant fluidic parameters and power modulations with torsional, longitudinal, or a combination of powers applied. Qualitative and quantitative analyses of the fluidic patterns of bead flow in the peripheral anterior chamber and near the aspirating tip opening indicated that torsional fluidics behave closer to the I/A-only configuration than longitudinal phacoemulsification, with the latter repelling more bead material in front of the aspiration tip. Bead clearance time was approximately 50% faster with torsional than with longitudinal US, regardless of the power setting. Bead flow-pattern evaluation is a feasible approach to future studies of fluid movement in the anterior chamber.

Evaluation of flow patterns and elongated bubble characteristics during the flow boiling of halocarbon refrigerants in a micro-scale channel

In the present study, quasi-diabatic two-phase flow pattern visualizations and measurements of elongated bubble velocity, frequency and length were performed. The tests were run for R134a and R245fa evaporating in a stainless steel tube with diameter of 2.32 mm, mass velocities ranging from 50 to 600 kg/m 2 s and saturation temperatures of 22 °C, 31 °C and 41 °C. The tube was heated by applying a direct DC current to its surface. Images from a high-speed video-camera (8000 frames/s) obtained through a transparent tube just downstream the heated sections were used to identify the following flow patterns: bubbly, elongated bubbles, churn and annular flows. The visualized flow patterns were compared against the predictions provided by Barnea et al. (1983) [1], Felcar et al. (2007) [10], Revellin and Thome (2007) [3] and Ong and Thome (2009) [11]. From this comparison, it was found that the methods proposed by Felcar et al. (2007) [10] and Ong and Thome (2009) [1] predicted relatively well the present database. Additionally, elongated bubble velocities, frequencies and lengths were determined based on the analysis of high-speed videos. Results suggested that the elongated bubble velocity depends on mass velocity, vapor quality and saturation temperature. The bubble velocity increases with increasing mass velocity and vapor quality and decreases with increasing saturation temperature. Additionally, bubble velocity was correlated as linear functions of the two-phase superficial velocity.

Pulsatility index variations using two different transit-time flowmeters in coronary artery bypass surgery☆

Transit-time flow measurement is widely accepted as an intra-operative assessment in coronary artery bypass grafting (CABG). However, the two most commonly applied flowmeters, manufactured by MediStim ASA and Transonic Inc., have different default filter settings of 20 and 10 Hz, respectively. This may cause different flow measurements, which will influence the reported results. The aim was to compare pulsatility index (PI) values recorded by the MediStim and Transonic flowmeters in two different clinical settings: (1) analysis of the flow patterns recorded simultaneously by both flowmeters in the same CABGs; and (2) evaluation of flow patterns under different levels of filter settings in the same grafts. Graft flow and PI were measured using the two different flowmeters simultaneously in 19 bypass grafts. Finally, eight grafts were assessed under different digital filter settings at 5, 10, 20, 30, 50 and 100 Hz. The Transonic flowmeter provided substantially lower PI as compared with the MediStim flowmeter. By increasing the filter setting in the flowmeter, PI increased considerably. The Transonic flowmeter displayed a lower PI than the MediStim, due to a lower filter setting. In the Transonic,flow signals are filtered at a lower level, rendering a 'smoother' pattern of flow curves. Because different filter settings determine different PIs, caution must be taken when flow values and flowmeters are compared. The type of flowmeter should be indicated whenever graft flow measurements and derived indexes are provided [corrected].

Overview: EOR/IOR (January 2006)

Papers in this feature discuss the incremental oil production from three field projects that use three different enhancement technologies: biotechnology, or microbial enhanced oil recovery (MEOR); miscible gas; and mobility-control polymer. Petro-Tech Peruana S.A. reported an impressive improvement after inoculating two pair of production wells in different offshore fields. Both fields contained a paraffinic crude oil that, when treated by conventional wellbore-cleanup technologies, simply maintained oil-production rates. Biotreating the producers resulted in improved oil rates, and subsequent radial inoculation further enhanced oil rates, approximately doubling the pre-MEOR rates. A peripheral, downdip, high-pressure gas-injection project in the RKF field in Algeria also is impressive. The paper discusses the discovery, development, and operation of a miscible-gas-cycling project in a fluvial complex of carboniferous reservoirs of low-permeability, high-clay-content formation containing asphaltic crude oil and salt-saturated water. During 8 of the 9 years of operation, production was maintained at approximately 20,000 B/D. A tracer study to quantify well conductivity and help identify preferential flow was implemented early in the gas-injection phase. Additional laboratory studies to support continued numerical simulation were performed, with the objective of continued studies being to define and select options that would improve oil recovery as gas injection continues. Three mobility-control pilot projects in Brazil complete the trio of papers. Four polymer pilot projects were started in 1997, 1999, and 2001 in the Carmopolis, Buracica, and Canto do Amaro fields, respectively. Mobility ratios ranging from 2 to 12 for water displacing crude oil provide a motive to implement the different mobility-control-polymer pilot floods. Injectivity changes and differences in interwell tracer studies are reported. Oil production increased, and declining water/oil ratios are discussed for each pilot and for well patterns within each pilot. These projects emphasize the importance of an ongoing evaluation and study of an EOR flood to maintain oil production and maximize oil recovery. Continual monitoring of project performance and reaction to what is happening in the field, making adjustments as necessary, and learning from performance are essential for successful expansion as well as for continued operation. EOR/IOR additional reading available at the SPE eLibrary: www.spe.org SPE 94139 "Application of Tracer Technology for Optimizing RKF Miscible-Gas-Injection Recovery—Field Case," by H. Cubillos, SPE, Cepsa, et al. SPE 94808 "Twenty Years of Steam Injection in Heavy-Oil Fields" by J.C. de Souza, Petrobras, et al. SPE 93100 "Sorption of Surfactant Used in CO2 Flooding Onto Five Minerals and Three Porous Media," by R.B. Grigg, SPE, New Mexico Recovery Research Center, et al. SPE 93241 "Gasflood Flow-Pattern Evaluation: Mesozoic Chiapas-Tabasco Basin Field Revisited," by M. Mercado, Pemex, et al.

Quantitative evaluation of flow patterns in perfusion cannulae by a new magnetic resonance imaging method.

The arterial cannula is a critical part of any extracorporeal circulation system due to the high flow rates which must pass a small cross-sectional area, resulting in high blood velocities. The aim of this study was to examine whether high-field magnetic resonance scanning is applicable for detailed mapping of velocity fields around the tip of such arterial cannulae in vitro. The investigated cannula was an angled, open-tip traditional design aortic cannula with an internal tip diameter of 5.5 mm. The velocity fields were measured at two different flow rates (2 and 4 l/min) at various positions in the lumen and outside the cannula using magnetic resonance imaging (MRI). All three components of the velocity vectors were measured. The study showed that MRI can provide a clear quantitative visualization of the velocity field around the tip of arterial cannulae at lower flow rates. At higher flow rates it can provide information about localization of regions with turbulent or disturbed flow.

Application of streamfunction vorticity approach in design of an axisymmetric radial inflow geometry with free liquid surface

This paper is concerned with the evaluation of flow patterns in steady-state, incompressible, axisymmetric flows using the streamfunction-vorticity approach. To extend the significance of the method in engineering applications, potential usefulness dealing with flow domains containing curvilinear and nonrectangular oriented boundaries is demonstrated. Using upwind-noncentred approximations for the convective terms in the vorticity transport equation the solutions are stable for Reynolds numbers in the order of 1000. The solution method provides quick information about flow patterns in the plane. The method is applied to the evaluation of flow fields in funnel geometries with an upward directed feeding stream and a free liquid surface. The flow in such devices is of interest, among others, in construction of flotation equipment. The magnitude of the circulation region was realized to influence the performance of the apparatus. Design suggestions to reduce the amount of circulation and the influence of the Reynolds number variation on the flow pattern are discussed. The results of numerical calculations show reasonable agreement with measured data obtained by hot-film anemometry.

Mechanical assisted circulation: In vitro evaluation of flow patterns in percutaneous arterial and venous cannulas

Mechanical assisted circulation: In vitro evaluation of flow patterns in percutaneous arterial and venous cannulas

Quantification of blood flow with dynamic MR imaging and presaturation bolus tracking.

A technique is described for rapid imaging of blood flow and dynamic measurement of its velocity. The method is a combination of bolus tracking and low-flip-angle gradient-echo cine angiography. This method provides precise determination of velocity with high temporal resolution in a single measurement. Unlike what occurs in phase imaging techniques, flow is displayed directly, eliminating potential errors that result from non-flow-related sources of phase shifts. Manipulation of raw data sets is avoided. Results obtained from a flow phantom, healthy volunteers, and a patient with an aortic aneurysm demonstrate the capability of the technique to track flow at low and high velocities and to differentiate flowing blood from thrombus. Because of its conceptual simplicity, rapidity, and lack of susceptibility to extraneous phase shifts, this technique may prove ideal for in vivo flow measurement and evaluation of flow patterns.

A new technique for evaluating cutaneous vascularity in complicated conjoined twins

Ischiopagus tripus conjoined twins were recently encountered. All organ systems were thoroughly evaluated using radiographic, angiographic, radionuclide, and CT imaging techniques. None of these studies were capable of accurately assessing the vascular territories of the skin at the level of the pelvis, the most critical area in terms of separation. Qualitative visual assessment of tissue fluorescein delivery under ultraviolet illumination is subject to subjective errors. Perfusion fluorometry is a recently developed technique whereby tissue fluorescence can be quantitated over time in very small amounts, even with repeated injections. In these conjoined twins, using sequential fluorescein injections in each twin, it was possible to accurately determine which portions of the pelvis and the shared leg belonged to which twin and exactly where the skin incisions should be made. Additionally, during operation it was possible to accurately predict the viability of skin flaps used for closure. Both twins survived. This is the first time it has been possible to accurately assess vascular territories of the skin in a complicated form of conjoined twinning. The technique is also useful in the evaluation of flow patterns in various other parts of the body.