Closed-loop Circulation System Research Articles

A Larger Membrane Area Increases Cytokine Removal in Polymethyl Methacrylate Hemofilters.

Blood purification is performed to control cytokines in critically ill patients. The relationship between the clearance (CL) and the membrane area during adsorption is not clear. We hypothesized that the CL increases with the hydrophobic area when hydrophobic binding contributes to cytokine adsorption. We investigated the relationship between the hemofilter membrane area and the CL of the high mobility group box 1 protein (HMGB-1) and interleukin-6 (IL-6). We performed experimental hemofiltration in vitro using polymethyl methacrylate membranes CH-1.8W (1.8 m2) and CH-1.0N (1.0 m2), as well as polysulfone membrane NV-18X (1.8 m2). After adding 100 mg of HMGB1 or 10 μg of IL-6 into the test solution, experimental hemofiltration was conducted for 360 min in a closed-loop circulation system, and the same amount of HMGB1 and IL-6 was added after 180 min. With CH-1.8W and CH-1.0N, both HMGB-1 and IL-6 showed a rapid concentration decrease of more than 70% at 180 min and 360 min after the re-addition. At 15 min, the CL of HMGB-1 was CH-1.8W: 28.4 and CH-1.0N: 19.8, and that of IL-6 was CH-1.8W: 41.1 and CH-1.0N: 25.4. CH-1.8W and CH-1.0N removed HMGB1 and IL-6 by adsorption and CH-1.8W was superior in CL, which increased with a greater membrane area.

High-Density Drilling Fluids for Managed Pressure Drilling: Lab Development and Field Trial

Abstract Managed pressure drilling (MPD) offers a closed-loop circulation system in which formation fracture pressure, bottom hole pressure, and pore pressure are considered and managed at surface. The right choice of drilling fluid used during MPD operation facilitates proper mud management and treatment. Lab formulation and field trial of a high-density water-based drilling fluid comprising a mixture of barite (BaSO4) and manganese tetroxide (Mn3O4) as weighting agents have been described in this paper. Drilling fluids having a mixture of Mn3O4 and BaSO4 as weighting agents would have lower equivalent circulating density (ECD), better sag, better acid solubility, and lower fluid cost as compared to conventional BaSO4-based fluids. This paper describes the formulation of three different water-based drilling fluids viz. 100, 120, and 150 pcf drilling fluids having a mixture of Mn3O4 and BaSO4 and hot rolled at temperatures of 270, 250, and 300 °F, respectively. Rheological properties, sag resistance, and high pressure-high temperature (HPHT) filtration properties of the three fluids have been described in the paper. Data obtained from the field trial of 160 pcf high-density drilling fluids having a mixture of Mn3O4 and BaSO4 for wells with a 300 °F bottom hole static temperature have been described. HPHT operations across naturally fractured formations with 0.5–1.0 pcf drilling fluid window have been described in the paper. During the field trial, the fluid having a mixture of Mn3O4 and BaSO4 showed good rheological, filtration, and sag properties thereby resulting in successful drilling of the well with no issues. MPD operation became more successful and practical with high-density drilling fluids having a mixture of Mn3O4 and BaSO4 as it facilitated better drilling fluid management and treatment in comparison to conventional fluids.

Effect of the Polymer Structure Diversity on the Eddies Suppression of Basrah Light Crude Oil Turbulent Flow

Poly(pentaerythritol adipate), poly(pentaerythritol sebacate), and poly(pentaerythritol hexadecandioate) derivatives containing different length alkyl branches were synthesized by two subsequent steps; the reaction of pentaerythritol with (C8-C16) linear aliphatic monocarboxylic acids and then, polymerization of products with (C6-C16) linear aliphatic dicarboxylic acids, using 1% para toluene sulfonic acid as a catalyst. The products were purified and characterized by FTIR, 1H NMR, and 13C NMR spectroscopy. End group analysis was also used as a molecular weight determination technique. The drag-reducing properties of those polymers were investigated in the turbulent flow of Basrah light crude oil using a closed-loop circulation system. Some were found to perform very well DRA and drag reduction efficacy of polymer was further found to be dependent on flowrate, polymer concentration, medium-temperature, and its chemical structure. Also, the effect of the imposed mechanical shear on the polymer stability as a function of time has been investigated using a cylindrical rotator device. It was observed that distance between branch points plays a direct role in contributing to the polymer performance and its mechanical stability.

LCA기법을 이용한 플라스틱 파렛트 풀링시스템에 대한 환경성 평가

The plastic pallet is a resource-circulating product that minimizes the production of new products through a closed-loop circulation system as a returnable logistics transport tool that recovers plastic pallets that have been used once in the logistics industry and uses them repeatedly through a pooling system. In this study, the environmental impacts of repetition and reuse of plastic pallet evaluated using LCA. And the results were used to compare with single used plastic pallet. The system boundary was set to raw material extraction stage, product manufacturing stage, use(distribution) stage, cleaning stage, and disposal and recycling stage. And use(distribution) stage was analyzed by subdividing into production plants, users, destinations, collection centers, and washing centers. As a result of the analysis of environmental improvement effects, the plastic pallet pooling system showed an average decrease of 73.3% based on the six impact categories compared to single use, and the impact category of resource depletion among the impact categories decreased by 91.5%, showing the greatest effect, and 72.8% environmental improvement effect on global warming.

Involvement of ionic interactions in cytokine adsorption of polyethyleneimine-coated polyacrylonitrile and polymethyl methacrylate membranes in vitro.

Polyethyleneimine-coated polyacrylonitrile (AN69ST) and polymethyl methacrylate (PMMA) membranes are effective cytokine-adsorbing hemofilters; however, the cytokine-adsorption mechanism remains elusive. This study investigated the involvement of ionic interactions in cytokine adsorption to a negatively charged AN69ST membrane and neutral-charged PMMA membrane. Experimental hemofiltration was performed for 30min in a closed-loop circulation system using AN69ST and PMMA hemofilters. Tumor necrosis factor (TNF)-α, interleukin (IL)-6, and IL-8 concentrations in the test solutions were measured at baseline and at 10min and 30min into hemofiltration. To investigate the involvement of ionic interactions in cytokine adsorption, cytokine clearance (CL) was calculated at 10min into hemofiltration and with three types of solutions at various pH levels (7.6, 7.2, and 6.8). During AN69ST hemofiltration, the CLs of TNF-α, IL-6, and IL-8 were 38 ± 6mL/min, 23 ± 7mL/min, and 78 ± 3mL/min, respectively, demonstrating a relationship with their respective isoelectric points. During PMMA hemofiltration, the CL of IL-6 peaked at 31 ± 76mL/min, with no relationship observed between the CL and isoelectric point. When the pH of the test solution shifted from 7.6 to 6.8, the CLs of TNF-α, IL6, and IL-8 increased in the AN69ST hemofilter; whereas, no such trend was observed in the PMMA hemofilter. These results indicated that Ionic interactions play a role in cytokine adsorption by the AN69ST membrane but not the PMMA membrane and highlight the clinical relevance of this finding, as well as the potential practical applications for further hemofilter design.

The Effect of Nano Materials on Lost Circulation Control of Azkand Formation in Khabaz Oil Field

Experimental tests were carried to control lost circulation in the Khabaz oil field using different types of LCMs including Nano-materials. A closed-loop circulation system was built to simulate the process of lost circulation into formations. Two dolomite plugs were used from different depths of the formation of Azkand in Khabaz oil field. The experimentations were carried out to study the effect of different types of LCMs, cross-linked copolymer (FLOSORB CE 300 S), SiO2 NP, and Fe2O3 NP, on mud volume losses as a function of time.
 The rheological measurements of the nanoparticles-reference mud system showed that both of the SiO2 NP and Fe2O3 NP worked best at 1.2 g/l. and the closed-loop circulation system showed that SiO2 NP cured losses by 48.3% and 37.5% for core plugs 5C1 and 1C2 respectively which is better than Fe2O3 NP loss curing which was 37.9% and 31.3% for core plugs 5C1 and 1C2 respectively.
 On the other hand, FLOSORB CE 300 S- Fe2O3 NP-reference mud systems cured losses up to 69% with 0.25g/l FLOSORB CE 300 S and 79.3% with 0.5 g/l FLOSORB CE 300 S which is better than the FLOSORB CE 300 S- SiO2 NP-reference mud systems results.

Observation on the drag reducing effect of low concentration chitosan solution in turbulent pipe flow

Polymer-based drag reducing agent (DRA) is used widely in various industries due to its ability to enhance fluid flow as well as economically beneficial to various sectors. This study is conducted to observe the drag reducing effect of chitosan as DRA and observed its effect on the turbulent flow inside the pipe. The experiment is conducted in a closed loop circulation system where water is the transport medium. The pipe system consist of acrylic pipes with 0.013 m, 0.025 m and 0.038 m diameter. The chitosan was extracted from shrimp shells and five different concentration of chitosan were tested. The degree of deacetylation of the chitosan shows 97% which indicates its solubility in water. It was found that the highest drag reduction percentage were obtained from 0.038 m pipe of 33 ppm concentration which is 28%. The flow pattern inside the pipe is also analysed and discussed in this study

Applying Selected Lost Circulation Materials to Study Lost Circulation of Azkand Formation in Khabaz Oil Field

Managing lost circulation during drilling is a great challenge issue in naturally fractured or vugy formations. This situation becomes further complicated if there are gas or oil returns at the same formation or at a formation above it. The lost circulation problem happens in some of the northern Iraqi oil fields such as Khabaz oil field. Particulate lost circulation materials (LCM) have been used for many years to control lost circulation. However, these traditional LCMs are not efficiently applicable to cure sever to total losses, such as highly fractured formations and formation with large vugs. In this work, an experimental attempt was done to solve such problem in Khabaz oil field. The experiments were carried out using a closed loop circulation system that simulates the drilling fluid loss into formations. Five core plugs from Azkand formation of Khabaz oil field from different depths were used. The experiments were grouped into three, the first was done with the fresh-water-based drilling fluid to measure the severity of losses. The second, fresh-water-based drilling fluid was treated with traditional LCM (cotton seeds) to investigate how the severity of losses is affected by these materials. Adding polymer lost circulation material were the last sets to modify the drilling fluid rheological properties which prepare a medium within the lost circulation zone that increases the friction inside the losses paths to increase the LCMs (the polymer itself) sealing efficiency.

Technology Update: Lowering Adoption Barriers to MPD - Land and Sea

Technology Update In the past, most wells have been drilled using conventional methods, but the landscape is changing as economic pressures have forced the drilling industry to refocus. Attention is at an all-time high on technologies that deliver operational efficiency and improve safety. Operators, drilling contractors, and service companies have gone through exhaustive measures to reduce cost, refine efficiency, optimize asset performance, and maximize returns. The recently introduced Schlumberger Managed-Pressure Drilling Integrated Solution offers a significant impact in all of these areas. Managed-pressure drilling (MPD) is an adaptive drilling process used to precisely control the annular pressure profile throughout the wellbore. In conventional drilling, the system is open to the atmosphere. However, with MPD, a closed-loop circulation system is created. The closed-loop system is the key element, as it enables control of the annular pressure profile through the application of surface pressure. MPD can dramatically improve operational efficiency through the reduction of nonproductive time associated with influxes, mud losses, and stuck-pipe events. The closed-loop system improves safety by providing an increased awareness of pressure state in the well and facilitates a much higher level of control with quicker response. The MPD drilling technique has been around for many years on land but is relatively new to deep water, as the needed technologies have only become available in the past 5 to 7 years. While manual chokes have been the principal form of control of MPD operations since the technique was introduced, it has been noted that the consistency and repeatability of manual methods is only as good as the choke operator’s skill and the level of experience and teamwork between the driller and the choke operator. For this reason, automated MPD was introduced, and a solution now exists that addresses the many challenges associated with MPD operations. A Shifting Business Case Historically, MPD components have been owned and leased through various service companies. Operators have called out multiple providers to deliver the kit and execute the service. Deepwater MPD requires substantial planning and financial investment, which has typically recurred with each call-out. On top of that has been the need to coordinate multiple service providers to work with the drilling contractor so that the system is properly integrated. Given these requirements, operators have tended not to use the technique unless the well or hole section they are planning cannot be drilled without it. For the most part, MPD in deep water has been a contingency solution rather than a standard practice. It is difficult to build a reasonable business case around a contingency solution or a call-out service that requires such significant investment and has multiple variables at stake. Additionally, service companies must charge a premium to ensure a sufficient return on their investment.

Impregnated Ni/ZrO2 and Pt/ZrO2 catalysts in dry reforming of methane: Activity tests in excess methane and mechanistic studies with labeled 13CO2

In the present work, 1%Ni/ZrO2, 3%Ni/ZrO2 and 1%Pt/ZrO2 catalysts prepared by impregnation with the concomitant addition of NaHCO3 were investigated and compared by structural investigations such as TEM, XRD, TPR, XPS and DRIFTS methods. Temperature programmed dry reforming (DRM) experiments were done (i) at atmospheric pressure in plug flow reactor and an in situ DRIFTS cell or (ii) under sub atmospheric pressure (∼50mbar) in a closed loop circulation system using labelled 13CO2 to trace the fate of carbon compounds. The calcined and reduced fresh catalysts contained nanoparticles in the range of 2–18nm. According to the TPR results, in 3%Ni/ZrO2 catalyst most of Ni is in strong interaction with the support. The presence of sodium was suggested to induce the appearance of strongly bound bridged CO sites during CO chemisorption in DRIFTS measurements for all samples and to cause BE shift in XPS spectrum of the highly dispersed Pt/ZrO2 only. In the catalytic tests in plug flow reactor the 3wt%Ni/ZrO2 sample turned to be the most active catalyst, but coke was deposited on its surface measured by the subsequent temperature programmed oxidation (TPO) measurements. In situ low temperature DRIFTS-DRM measurements suggested that stability of surface carbonates is less when dispersed electron-rich Pt nanoparticles are on the ZrO2 support, while more carbonates accumulate on Ni/ZrO2 samples. Based on our isotope labeled 13CO2+12CH4 experiments in circulation system, the same initial reaction pathways could be suggested for the Ni and Pt catalysts. The reactive surface carbon species from the two different sources (CH4 and CO2) were completely scrambled on 3wt%Ni/ZrO2 at 600°C, suggesting that common reaction intermediates do exist.

Drag Reducing Flow of water in forced closed loop circulation system by using Sodium dodecyl sulfate additive

The turbulent flow friction of a water solution with a small amount of surfactant additive is dramatically reduced when compared to that of pure water. This effect offers a significant reduction in pumping power and energy consumption. Commercial implementation of drag reducing fluids have proved successful for oil pipeline transportation, district heating and cooling systems, fire fighting, sewer throughput, jet cutting, etc. The investigation was carried out on a facility with a forced closed loop for pressure drop measurements. A type of anionic surfactant (Sodium dodecyl sulfate) mixed with same weight of counter ion material (Sodium nitrate) was used as a drag reducing additive to tap water at a mass concentration ranged from 50 to 2000 ppm. Pressure drop data was collected over a 1668 mm flow pipe of carbon steel with 15.8 and 26.6 mm internal diameter and different solution flow rate (up to 8 m3/h) at constant temperature of 30 ̊C (ambient temperature). The paper focused on calculation of friction factor from experimental data. It was found that the friction factor values lies near Blasuis asymptote for pure solvent, while they positioned towards maximum drag reduction asymptotes when surfactant is added. A maximum drag reduction percent of about 66% was obtained by using 2000 ppm surfactant – counter ion aqueous solution. Also, it was concluded that there is a critical Reynolds number equals to about 96000 not to be exceeded because any further increasing leads to decrease in drag reduction. In addition, a correlation equation was found to correlate wall shear stress as a function of bulk mean fluid velocity. This correlation equation is of value in scale up of results obtained in small laboratory equipments to larger diameter pipes and different operating conditions. Another objective was to investigate the mechanism behind a possible drag reduction.

Micro bubble formation and bubble dissolution in domestic wet central heating systems

16 % of the carbon dioxide emissions in the UK are known to originate from wet domestic central heating systems. Contemporary systems make use of very efficient boilers known as condensing boilers that could result in efficiencies in the 90-100% range. However, research and development into the phenomenon of micro bubbles in such systems has been practically non-existent. In fact, such systems normally incorporate a passive deaerator that is installed as a ‘default’ feature with no real knowledge as to the micro bubble characteristics and their effect on such systems. High saturation ratios are known to occur due to the widespread use of untreated tap water in such systems and due to the inevitable leakage of air into the closed loop circulation system during the daily thermal cycling. The high temperatures at the boiler wall result in super saturation conditions which consequently lead to micro bubble nucleation and detachment, leading to bubbly two phase flow. Experiments have been done on a test rig incorporating a typical 19 kW domestic gas fired boiler to determine the expected saturation ratios and bubble production and dissolution rates in such systems.

In Vitro Evaluation of High Mobility Group Box 1 Protein Removal with Various Membranes for Continuous Hemofiltration

The high mobility group box 1 protein (HMGB1) is an alarmin that plays an important role in sepsis and has been recognized as a promising target with a wide therapeutic window; however, no drugs and devices are currently in practical use. We hypothesized that hemofilters composed of porous membranes or cytokine-adsorbing membranes could remove HMGB1 from the blood. We performed experimental hemofiltration in vitro using four types of hemofilters composed of different membranes specifically designed for continuous hemofiltration. The test solution was a 1000-mL substitution fluid containing 100 µg of HMGB1 and 35 g of bovine serum albumin. Experimental hemofiltration was conducted for 360 min in a closed loop circulation system. Among the four membranes, surface-treated polyacrylonitrile (AN69ST) showed the highest capacity to adsorb HMGB1; it adsorbed nearly 100 µg of HMGB1 in the initial 60 min and showed a markedly high clearance rate (60.8 ± 5.0 mL/min) at 15 min. The polymethylmethacrylate membrane had half of the adsorption capacity of the AN69ST membrane. Although the highest sieving coefficient for HMGB1 was obtained with the high cut-off polyarylethersulfone membrane, which correlated with a constant filtrate clearance rate, albumin loss was observed. However, no such removal of both HMGB1 and albumin was observed with the polysulfone membrane and tubing. We conclude that continuous hemofiltration using the AN69ST membrane is a promising approach for HMGB1-related sepsis.

The Study of Glycolic Acid Ethoxylate 4-nonylphenyl Ether on Drag Reduction

Power saving is the major reason to study the problem of drag in transporting system. The performance of glycolic acid ethoxylate 4-nonylphenyl ether as drag reducing anionic surfactant was studied experimentally in closed loop circulation system at room temperature. The major investigated variables is operation flow rate which from 11235 to 78645 Re and the solution concentration (ppm), which 200, 300, 400, 500 and 600, respectively. The selected ratio of testing pipe length to diameter (L/D) is equal to 59. The specific conductivity test was conducted to find the CMC of anionic surfactant. It was found that the CMC occurred within the range of 100 to 200 ppm of solution. The maximum drag reduction can be achieved up to 14%. The critical Re was found at 33705 to 56175. The alignment of micelle with the eddies in turbulent flow was identified as the source of drag reduction in pipes.

Drag Reduction of Crude Oil Flow in Pipelines Using Sodium Dodecyl Benzene Sulfonate Surfactant

In the present work, a closed loop circulation system consist of three testing sections was designed and constructed. The testing sections made from (3m) of commercial carbon steel pipe of diameters(5.08, 2.54 and 1.91 cm) . Anionic surfactant (SDBS )with concentrations of (50, 100, 150, 200 and 250 ppm) was tested as a drag reducing agent. The additive(SDBS)studied using crude oil from south of Iraq. The flow rates of crude oil were used in 5.08 and 2.54 cm I.D. pipes are (1 - 12) m3/hr while (1-6) m3/hr were used in 1.91 cm J .D. pipe . Percentage drag reduction (%Dr) was found to increase by increasing solution velocity, pipe diameter and additives concentration (i.e. increasing Renolds number). Also it was found that there is no change in apparent physical properties (viscosity) of crude oil after the addition of SDBS. The higher value of drag reduction of 54% in 5.08 cm I.D. was observed using 250 ppm SDBS surfactant dissolved in the used crude oil at flow rate of 12 m3/hr. Friction factor was calculated from experimental data. The friction factors values for pure solvent lies near or at Blasius asymptote suggested for flow of Newtonian fluids. After the addition of small amount of SDBS, the friction factor values were positioned below Blasius asymptote toward Virk maximum drag reduction asymptote, which was never reached.

Fast wet anisotropic etching of silicon utilizing microwave treatment of KOH etchant

The properties of modified remote microwave-activated etching of silicon (the E2MSi method), utilizing the ‘microwave memory effect’, are presented. In the method, prior to the etching process, the etchant was repeatedly microwave-treated in a closed-loop circulation system. It has been found that the etch rate of the (1 0 0) plane was higher than in standard procedures. The etchant continued the microwave activation for longer and the increase in the etch rate was greater than with a single-time activated etchant. The results of a simple and repeatable experiment (growth of NaCl crystals) confirmed the influence of the ‘microwave memory effect’ on aqueous solutions. The nature of the phenomena described is also discussed.

Performance of a natural convection circulation system for supercritical fluids

A closed-loop circulation system for supercritical fluids that operates on the principle of density differences induced by a heating and a cooling source has been developed. Performance of the system was determined by measuring average flow velocities for CO 2 over a range of conditions from 7.8 to 15 MPa and from 15 to 55 °C for the given initial loading densities, ρ ini, of 550–800 kg/m 3 and density differences, Δ ρ eff, between heating and cooling sources of the loop of 62–121 kg/m 3. One-dimensional finite-difference simulation could predict the velocities at most conditions to within 35%. The flow rates achieved in the system could be correlated in terms of Grashof and Prandtl numbers and a dimensionless effective density difference between heating and cooling sources to within 25% and by an empirical equation in terms of the system pressure, loaded density and heating and cooling source average density difference to within 10%. Average flow velocities as high as 4 m/min could be obtained with heating and cooling source (wall) temperature differences of 3–8 °C. The system should find use in applications such as extended-time extractions, sample preparation and enrichment for analytical applications, catalytic reactions and for transporting slurry suspensions and solutions.

In vitro hemocompatibility studies of drug-loaded poly-( l-lactic acid) fibers

Our objective was to evaluate the hemocompatibility of biodegradable stent fibers, employing a closed-loop circulation system filled with human blood. We also investigated the effects of the anti-inflammatory and anti-proliferative drugs curcumin and paclitaxel, incorporated into stent fibers. Fresh whole blood was circulated in four parallel closed-loop systems: the empty tube circuit (control) and tubes containing either a PLLA fiber coil (PLLA), a curcumin-loaded PLLA coil (C-PLLA) or a paclitaxel-loaded PLLA coil (P-PLLA). The influence of PLLA fiber, alone or loaded with drug incorporated during melt-extrusion, on leukocyte and platelet adhesion and activation was determined by flow cytometry. The effects of blood flow and fiber properties on cell deposition were assessed by scanning electron microscopy (SEM). The flow cytometry results clearly demonstrated that PLLA triggers blood cell activation at the site of deployment, as shown by increases in CD11b, CD62P and leukocyte–platelet aggregates, compared to controls. Curcumin and paclitaxel treatments both significantly reduced leukocyte and platelet activation and adhesion to PLLA fibers, as shown by flow cytometry and SEM. Activated leukocytes and platelets revealed significantly lower CD11b and CD62P receptor binding for C-PLLA compared with PLLA alone, and slightly lower for P-PLLA. Reductions in platelet–leukocyte aggregates were observed as well. In addition, there was less leukocyte and platelet adhesion to C-PLLA, compared with PLLA fiber controls, as shown by SEM. A continuous linear thrombus, composed of platelets, leukocytes, red blood cells and fibrin was occasionally detected along the line of tangency between the coil and the tube wall. Flow separation and eddying, proximal and distal to the line of tangency of coil and tube, is thought to contribute to this deposit. Curcumin was more effective than paclitaxel in reducing leukocyte and platelet activation and adhesion to PLLA stent fibers in this setting. However there was evidence of paclitaxel degeneration during melt extrusion that may have inhibited its effectiveness. Incorporation of the anti-inflammatory and anti-proliferative drug curcumin into bioresorbable stent fibers is proposed to prevent thrombosis and in-stent restenosis.

Anatomic distribution of metastases in the vertebral body and modes of hematogenous spread.

A retrospective review of the magnetic resonance spine examinations of 49 patients with metastatic bone disease to the spine was performed. To determine whether the pattern of metastatic distribution in the spine correlates with the type of primary tumor and theoretical mode of hematogenous spread by arterial or venous routes. In 1940, Batson theorized a venous plexus route by which tumors spread to the spine from pelvic tumors such as prostatic carcinoma. It this theory is true, the venous vascular anatomy of the spine would result in metastases being deposited in the central or posterior vertebral body, whereas arterial deposits would occur near the end-plates. Each vertebral body was divided into 27 equal cells in the magnetic resonance images; the central and posterior cells in the midsagittal view were defined as central, and the other cells were defined as peripheral. The primary tumor was assigned to either the arterial or venous group based on Batson's proposed mode of spread. The average number of lesions per involved vertebral body in the central and peripheral regions was calculated. There was no statistically significant correlation between tumors with proposed arterial/venous routes of metastasis and central/peripheral location of metastatic deposits. The mechanism by which tumors spread to the vertebral body may not be via a pure arterial or venous route. Other mechanisms such as tissue specificity, cascade system, and closed loop circulation system may be involved.