Foam Pellets Research Articles

Development and Characterization of Polyethylenimine-Infiltrated Mesoporous Silica Foam Pellets for CO2 Capture.

Polyethylenimine (PEI) has been shown to be promising for direct air capture (DAC) of carbon dioxide and has potential for commercial scale-up globally. Laboratory scale processes include multiple steps, such as mixing, solvent extraction, vacuum application, sonication, and various flushes and activation steps. It is critical to properly control these operating parameters to achieve higher capture capacity as a result of the optimized material configuration. This study adopts previously published pelletization processes for PEI-infiltrated mesoporous foam silica (mesoporous silica foam) to uncover the adsorption mechanisms and optimize the associated fabrication steps, such as sonication, to achieve higher sorbent productivity. A high capture capacity was achieved at 46 °C for 75 wt % PEI loading (2.27 mmol/g) followed by PEI_MSF 70 (1.81 mmol/g) and PEI_MSF 80 (1.44 mmol/g). As part of the optimization, sonication parameters of frequency, amplitude, and time were modified for PEI_MSF 75 sorbent, which resulted in the highest uptake capacity of 3.04 mmol/g (sonicated at 40 kHz and a wave amplitude of 50% for 30 s). These preliminary results would tend to prove that sonication energy affects carbon capture capacity, although there is still a lack of understanding regarding the exact underlying mechanism, suggesting the need for further investigation. It is important to note that the present work is focused on the adsorption mechanisms and not desorption or durability of the capture performance. Ongoing research addresses these factors. This paper is intended to establish baseline DAC behavior of a promising capture medium and begins probing the optimization spectrum by considering the effects of sonication energy on adsorption. Ongoing work intends to address potential abbreviations of the full range of process steps and furthers the understanding of kinetics by considering the desorption and resorption attributes.

Optimization of metal foam pellet shape in packed beds for improved radial heat transfer using particle-resolved computational fluid dynamics

Process intensification in tubular reforming reactors has always been a topic of interest, particularly for improving the radial heat transfer. The innovation of open-cell metallic foam pellets is the latest in this category, as they bear unique transport properties. This work presents the optimization of metal foam pellet shapes for improved radial heat transport, using a virtual design platform based on a modified version of particle-resolved computational fluid dynamics. To optimize the pellet geometry, different configurations such as pellet with inner holes, external grooves, and varied aspect ratios, as well as different foam morphologies (cell size ϕ and porosity ε) are considered, and the influence of each pellet configuration on flow and energy transport in a randomly packed bed setup has been investigated. Based on the desirable properties of the packed bed, such as low pressure drop, high heat transfer coefficient, increased surface area, and high catalyst inventory, the overall performance of the investigated pellet shapes is analyzed. The foam ring with the aspect ratio of 2.5 and ϕ = 0.45 mm, ε = 0.82 has been identified as optimal under the investigated operating conditions 250 < ReP < 2250, which is confirmed by pressure drop and heat transfer experiments.

Oxidation behavior and decomposition kinetics of mixed-waste biomass material

In Taiwan, approximately 379,000 automobiles and 588,000 motorcycles were recycled in 2019. Rigid polyurethane foam is one of the principal components of auto shredder residue. The amount of rigid polyurethane foam from the recycling of waste vehicles is 8,000 to 10,000 tons/year. In this study, waste Cryptomeria wood was mixed with waste rigid polyurethane foam to form derived fuels. The oxidation behaviors of the wood mixed with waste rigid polyurethane foam-derived fuels were investigated. The characteristics of the derived fuel made from wood mixed with waste rigid polyurethane foam showed that the ash content was less than 2.5% and its calorific value reached 21.9 MJ/kg. According to the Friedman equation, the activation energies of the wood mixed with 5%, 15%, and 30% of waste rigid polyurethane foam pellets were 212, 220, and 188 kJ/mol, respectively. The thermal conversion efficiencies of the wood mixed with 5%, 15%, and 30% of waste rigid polyurethane foam pellets were 30.2% to 48.1% by a water boiling test. The results showed that waste Cryptomeria mixed with waste rigid polyurethane foam-derived fuels is suitable for use as an alternative renewable energy fuel.

Radial heat transport in a fixed-bed reactor made of metallic foam pellets: Experiment and particle-resolved computational fluid dynamics

Open-cell metallic foams in the shape of pelletized catalysts are regarded as potential catalyst substrates for the application in fixed-bed reactors. This work reports an experimental study and a detailed Computational Fluid Dynamics (CFD) model to investigate the heat transfer performance of a fixed-bed reactor made of open-cell metallic foam pellets. The steady-state heat transfer behavior of a hot gas flowing through such a packed bed under wall-cooled conditions was examined. The proposed CFD model is in line with the particle-resolved CFD (PRCFD) approach that accounts explicitly for the random packing structure, so that the transport processes in the interstitial regions are fully resolved. The momentum and energy transports inside the highly porous foam particles are considered by closure equations based on the porous-media model. The Rigid Body Dynamics (RBD) method is adopted to create the packing geometry. The axial temperature and the pressure drop obtained by the CFD simulations show good agreement with experimental data. To evaluate the thermal performance, effective heat transport parameters in a packed bed such as the effective radial thermal conductivity and the apparent wall-fluid heat transfer coefficient are determined, with the aid of a 2D pseudo-homogenous plug-flow reactor model. The correlations for heat transport characteristics as a function of particle Reynolds number for the metallic foam packed bed are also presented.

Influence of Foam Morphology on Flow and Heat Transport in a Random Packed Bed with Metallic Foam Pellets-An Investigation Using CFD.

Open-cell metallic foams used as catalyst supports exhibit excellent transport properties. In this work, a unique application of metallic foam, as pelletized catalyst in a packed bed reactor, is examined. By using a wall-segment Computational Fluid Dynamics (CFD) setup, parametric analyses are carried out to investigate the influence of foam morphologies (cell size and porosity ) and intrinsic conductivity on flow and heat transport characteristics in a slender packed bed made of cylindrical metallic foam pellets. The transport processes have been modeled using an extended version of conventional particle-resolved CFD, i.e., flow and energy in inter-particle spaces are fully resolved, whereas the porous-media model is used for the effective transport processes inside highly-porous foam pellets. Simulation inputs include the processing parameters relevant to Steam Methane Reforming (SMR), analyzed for low ( and high ( flow regimes. The effect of foam morphologies on packed beds has shown that the desired requirements contradict each other, i.e., an increase in cell size and porosity favors the reduction in pressure drop, but, it reduces the heat transfer efficiency. A design study is also conducted to find the optimum foam morphology of a cylindrical foam pellet at a higher , which yields = 0.45, = 0.8. Suitable correlations to predict the friction factor and the overall heat transfer coefficient in a foam-packed bed have been presented, which consider the effect of different foam morphologies over a range of particle Reynolds number, .

Fluidized ZnO@BCFPs Particle Electrodes for Efficient Degradation and Detoxification of Metronidazole in 3D Electro-Peroxone Process.

A novel material of self-shaped ZnO-embedded biomass carbon foam pellets (ZnO@BCFPs) was successfully synthesized and used as fluidized particle electrodes in three-dimensional (3D) electro-peroxone systems for metronidazole degradation. Compared with 3D and 2D + O3 systems, the energy consumption was greatly reduced and the removal efficiencies of metronidazole were improved in the 3D + O3 system. The degradation rate constants increased from 0.0369 min−1 and 0.0337 min−1 to 0.0553 min−1, respectively. The removal efficiencies of metronidazole and total organic carbon reached 100% and 50.5% within 60 min under optimal conditions. It indicated that adding ZnO@BCFPs particle electrodes was beneficial to simultaneous adsorption and degradation of metronidazole due to improving mass transfer of metronidazole and forming numerous tiny electrolytic cells. In addition, the process of metronidazole degradation in 3D electro-peroxone systems involved hydroxyethyl cleavage, hydroxylation, nitro-reduction, N-denitrification and ring-opening. The active species of ·OH and ·O2− played an important role. Furthermore, the acute toxicity LD50 and the bioconcentration factor of intermediate products decreased with the increasing reaction time.

Comparative Evaluation of Cotton PTFE Tape and Foam Pellets as Endodontic Spacer in Primary Teeth: An In Vivo Study.

Aim and objectiveThis study was conducted to microbiologically evaluate cotton, PTFE tape, and foam pellets as endodontic spacer in primary teeth.Materials and methodsThirty primary second molars indicated for pulpectomy were included in this study. Followed by the completion of pulpectomy in each teeth cotton, PTFE tape, and foam pellets were placed as endodontic spacers randomly in 10 teeth each. The samples were collected from the pulp chamber at baseline and after 7 days to evaluate for microbial contamination of the same. The data obtained was tabulated and subjected to appropriate statistical analysis.ResultsThere was a statistically significant increase in the colony forming unit after 7 days in cotton and foam pellet group. But PTFE tape group showed very minimal contamination of the pulp chamber after 7 days.ConclusionWithin the limitations of this study, it can be concluded that PTFE tape found to be the best alternative to cotton as an endodontic spacer.Clinical significanceIn case of multiple visit pulpectomy procedure, the state of sterility must be maintained in between the appointments until a definitive coronal restoration is placed following root-canal obturation. So it is mandatory to place an endodontic spacer under a provisional restoration to maintain the patency of the root canals and prevention of the microbial growth. The PTFE tape is inorganic, nonfibrous material which can be tightly packed without any voids under the provisional restoration. So PTFE tape is the best material to maintain the root canal patency and to provide a sterile environment by preventing the microbial growth under the provisional restoration as an endodontic spacer material in between the appointments.How to cite this articleSomani R, Arya MV, Singh DJ, et al. Comparative Evaluation of Cotton PTFE Tape and Foam Pellets as Endodontic Spacer in Primary Teeth: An In Vivo Study. Int J Clin Pediatr Dent 2022;15(1):74-78.

Workflow for computational fluid dynamics modeling of fixed‐bed reactors packed with metal foam pellets: Hydrodynamics

AbstractIn recent years, the catalyst pellets made of open‐cell metallic foams have been identified as a promising alternative in fixed‐bed reactors. A reliable modeling tool is necessary to investigate the suitability of different foam properties and the shapes of foam pellets. In this article, a workflow for a detailed computational fluid dynamics (CFD) model is presented, which aims to study the flow characteristics in the slender packed beds made of metal foam pellets. The CFD model accounts for the actual random packing structure and the fluid flow throughout the interstitial regions is fully resolved, whereas flow through the porous foam pellets is represented by the closure equations for the porous media model. The bed structure is generated using rigid body dynamics (RBD) and the influence of the catalyst loading method is also considered. The mean bed voidage and the pressure drop predicted by the simulations show good agreement with the experimental data.

A Novel Lightweight Polyurethane Composite for Application on Ultra-High-Voltage Insulator Core Filler.

This study aimed to prepare a new lightweight ultra-high-voltage insulator core filler composite, which can solve the problem of bulkiness. In this study, rigid polyurethane foam pellets with different densities are used as lightweight fillers and polyurethane resins to compound lightweight composite materials. On accounting for working conditions, the density, insulation, heat resistance, water absorption and mechanical properties are tested. The compressive properties of composites are determined by a foam skeleton and a process. Among three kinds of composites, in which the composites with the best comprehensive performance are materials filled with pellets to a density of 0.15g·cm−3. The density, surface resistance, volume resistance, leakage current, initial decomposition temperature, water absorption, force, rupture displacement and limiting oxygen index (LOI) of composites are 0.665 g·cm−3, 1.17 × 1014 Ω, 9.68 × 1014 Ω·cm, 0.079 mA, 208 °C, 0.047%, 2262 N, 2.54 mm, and 23.3%, respectively. The ultra-high-voltage insulator core filler in this study can reduce the weight of the solid core insulator crossarm for Ultra-High Voltage (UHV) by 50–75%.

Coadsorption of gaseous xylene, ethyl acetate and water onto porous biomass carbon foam pellets derived from liquefied Vallisneria natans waste

AbstractBACKGROUNDOnly a few studies have focused on the purification of waste gas containing a mixture of volatile organic compounds (VOCs) with engineered biochar. The adsorption behaviors of gaseous xylene and ethyl acetate (EA) individually and in binary mixture onto porous biomass carbon foam pellets (BCFPs) were studied by static headspace gas chromatography.RESULTSThe removal efficiency nearly reached 100% for 17.32 mg L−1 xylene and 18.02 mg L−1 EA within 120 min at a BCFP dosage of 0.2 g L−1, a temperature of 40 °C and a relative humidity of 30%. The adsorption behavior followed the pseudo‐second‐order kinetic model for single and binary mixtures of xylene and EA. The coexistence of xylene had considerable influence on the adsorption performance of EA, whereas the coexistence of EA exhibited minimal effect on the adsorption performance of xylene. The monolayer adsorption capacities of sole xylene and EA were 250.63 and 206.61 mg g−1 respectively. The total adsorption capacity reached 322.36 mg g−1 for the binary mixture, but the adsorption capacity for sole xylene and EA decreased because of competitive adsorption. The adsorption process was spontaneous and endothermic. Pore filling was involved in the adsorption of xylene and EA onto BCFPs. Meanwhile, xylene adsorption was involved in the hydrophobic interaction and π–π electron dispersion interaction.CONCLUSIONBCFPs are an effective adsorbent for VOC adsorptive removal from waste gas. Competitive adsorption between xylene and EA on BCFPs was determined. Results indicated that the physicochemical properties of VOCs had an effect on the adsorption performance. © 2019 Society of Chemical Industry

Acid and Thermal Treatment of Alkali-Activated Zeolite Foams

The foamed alkali-activated zeolite materials have been studied primarily in terms of mechanical and structural properties as potential substitutes for concrete and other building materials. However, they also have interesting textural and acid properties that make them much more useful, especially in the chemical industry. The aim of the study is to map in detail the influence of post-synthesis modifications of alkali-activated natural zeolite foams on their chemical, mechanical, and textural properties for possible use in catalytic and adsorption applications. Alkali-activated natural zeolite foam pellets were prepared by activation with mixed potassium hydroxide and sodium silicate activator and foamed using H2O2 solution. The foam pellets were post-synthetic modified by leaching with mineral and organic acids and calcination. The properties of the modified materials were characterised on the basis of XRF, XRD, N2 physisorption, DRIFT, SEM, NH3-TPD analyses, and the strength measurements. Our data showed that the basic clinoptilolite structure remains unchanged in the material which is stable up to 600 °C after acid leaching. In two-step leaching, the specific surface area increases to 350 m2/g and the leaching process allows the acid properties of the materials to be varied.

Modeling fixed-bed reactors from metal-foam pellets with detailed CFD

Open-cell metal foams are a promising alternative to conventional solid pellets for the application as structured catalyst support. Pellets made from metal foams can be used in fixed-bed reactors instead of ceramic pellets. In this contribution, a comprehensive and detailed computational fluid dynamics (CFD) model is presented for fixed-bed reactors consisting of metal foams. The inner structure of the foams, i.e. pores, struts, and nodes, is not resolved. Instead, a pseudo-homogeneous model is applied to describe pressure drop and heat transfer inside the foam pellets. The fixed-bed structure is particle-resolved. The bed is generated synthetically with the discrete element method (DEM) and the results are in great agreement with µCT data. The experimental pressure drop for two different porous pellet shapes can be reproduced reasonably with CFD simulations. In an illustrative heat-transfer study, the performance of a state-of-technology solid-pellet bed and a porous cube bed is compared. Whereas the heat transfer is similar in both cases, the pressure drop is lower in the bed of porous cubes. A residence-time distribution analysis reveals that the porous pellet shape should be optimized to obtain a better mixing behavior. The presented fixed-bed model can be applied for such tasks, since it is valid for almost any pellet shape.

Clinoptilolite foams prepared by alkali activation of natural zeolite and their post-synthesis modifications

Abstract Alkaline activated aluminosilicate materials have been studied mainly in the building industry as a substitute for concretes, ceramic materials and thermal insulations, but their properties predispose them to much greater use in the chemical industry. The aim of this study is to determine whether the alkaline activated natural zeolites can be modified to obtain a suitable chemical and textural properties for catalyst supports or sorbents. The alkaline activated natural zeolites with the clinoptilolite structure were foamed using Al powder and H2O2 solution. The prepared foam pellets were post-synthetically modified by HCl leaching and analyzed to compare their properties by XRF, XRD, N2 physisorption, Hg porosimetry, DRIFT, TGA, SEM and the cutting-edge strength methods. The analysis showed that the clinoptilolite structure of the basic raw zeolite was partially preserved and porous materials had sufficient strength, a density of about 0.8 g/cm3 and a specific surface area up to 160 m2/g making them suitable as catalyst supports or sorbents.

Adsorption of nitroimidazole antibiotics from aqueous solutions on self-shaping porous biomass carbon foam pellets derived from Vallisneria natans waste as a new adsorbent

Powdered biomass adsorbents can potentially remove antibiotics from wastewater. However, recovering or separating the adsorbents after use is difficult. The preparation of mold-assisted shaping of biomass carbon foam pellets (BCFPs) without compaction and addition of binder instead of powdered adsorbent, is rarely reported. Therefore, the study explored the formation mechanism of BCFPs by using Vallisneria natans (V. natans) waste as precursor and investigated the adsorption performance and mechanisms of metronidazole (MNZ) and dimetridazole (DMZ) onto BCFPs. The optimal preparation conditions were V. natans-and-ZnCl2 mass ratio of 1:2.4, carbonization temperature of 600 °C, and time of 90 min. BCFPs exhibited uniform size, excellent floatability, and abundant micropores. The Brunauer–Emmett–Teller specific surface area, total pore volume, and micropore volume of BCFPs were 922.56 m2 g−1, 0.421 cm3 g−1, and 0.386 cm3 g−1, respectively. The adsorption process of MNZ and DMZ was both described well by pseudo-first-order kinetic model. However, the isotherm data fitted well with Langmuir for MNZ and Dubinin–Radushkevic model for DMZ, with a maximum monolayer adsorption capacity of 64.23 and 82.58 mg g−1, respectively. The nature of the adsorption process is endothermic and spontaneous. The adsorption mechanisms of MNZ and DMZ onto BCFPs were mainly hydrogen bonding, π-π interactions, and micropore filling. Preparation of BCFPs with high mechanical strength and excellent adsorption capacity from V. natans waste without compaction and any binder is feasible. Furthermore, BCFPs are easily separated and recyclable adsorbents, and their average recovery rate was 99.6%.

Dual-mechanism gastroretentive drug delivery system loaded with an amorphous solid dispersion prepared by hot-melt extrusion

In the present study, we aimed to prepare a gastroretentive drug delivery system that would be both highly resistant to gastric emptying via multiple mechanisms and would also potentially induce in situ supersaturation. The bioadhesive floating pellets, loaded with an amorphous solid dispersion, were prepared in a single step of hot-melt extrusion technology. Hydroxypropyl cellulose (Klucel™ MF) and hypromellose (Benecel™ K15M) were used as matrix-forming polymers, and felodipine was used as the model drug. The foam pellets were fabricated based on the expansion of CO2, which was generated from sodium bicarbonate during the melt-extrusion process. A 2n full factorial experimental design was utilized to investigate the effects of formulation compositions to the pellet properties. The melt-extrusion process transformed the crystalline felodipine into an amorphous state that was dispersed and “frozen” in the polymer matrix. All formulations showed high porosity and were able to float immediately, without lag time, on top of gastric fluid, and maintained their buoyancy over 12h. The pellet-specific floating force, which could be as high as 4800μN/g, increased significantly during the first hour, and was relatively stable until 9h. The sodium bicarbonate percentage was found to be most significantly effect to the floating force. The ex vivo bioadhesion force of the pellets to porcine stomach mucosa was approximately 5mN/pellet, which was more than five times higher than the gravitation force of the pellet saturated with water. Drug release was well controlled up to 12h in the sink condition of 0.5% sodium lauryl sulphate in 0.1N HCl. The dissolution at 1, 3, 5, and 8h were 5–12%, 25–45%, 55–80%, and ≥75% respectively for all 11 formulations. In biorelevant dissolution medium, a supersaturated solution was formed, and the concentration was maintained at around 2μg/mL, approximately 10-folds higher than that of the pure felodipine. All input factors significantly affected dissolution in the first 3h, but afterwards, only drug load and hypromellose (HPMC) content had significant effects. The prepared drug delivery system has great potential in overcoming low and fluctuating bioavailability of poorly soluble drugs. ChemicalFelodipine (PubChem CID: 3333); hypromellose (PubChem CID: 57503849), hydroxypropyl cellulose (PubChem CID: 71306830), sodium bicarbonate (PubChem CID: 516892); sodium carbonate (PubChem CID: 10340).

A Biosurfactant/Polystyrene Polymer Partition System for Remediating Coal Tar-Contaminated Sediment

ABSTRACTA sustainable, green chemistry process is proposed for the cleanup of coal tar impacted sediment in under 2 hr. A mixture of proteins and polypeptides, extracted from corn gluten meal and hemp, when mixed with sediment and polystyrene foam pellets (PFPs), serves to mobilize tar, which sorbs onto PFP. Since the sorbent floats, coal tar is easily extracted from the agitation vessel. An empirically derived 4-dimensional surface response model accurately predicts removal rates of the tar and operational costs of the system under various experimental conditions. At optimum relative to cost, 81% of the two to six ring polycyclic aromatic hydrocarbons (PAHs) and 73% of the total tar mass are removed despite high sediment organic carbon content (16.4%) and silty fines (∼85%). Multiple PFP extractions (n = 2) of the same sediment/biosurfactant mixture yielded 94% extraction of PAH. Scanning electron microscope images illustrate free-phase tar (globule) sorption onto the foam. A field pilot was conducted in which 25 kg of sediment was processed. Results were in excellent agreement with both lab (10 g) experiments and model predictions. The process is considered sustainable and green because the active ingredients are derived from renewable crop materials, recycled polystyrene is used, and the biosurfactant is recyclable which reduces water demand and treatment costs, with the recovered tar used as fuel and sediment as beneficial reuse material.

Potential for metal foams to act as structured catalyst supports in fixed-bed reactors

Experiments were performed in which the benefits of flow through the large interconnecting cavities in structured metal foams (acting as catalyst supports) could be better understood. For example, using tablet shaped (8mm×8mm×3mm) metal foam pellets (1200μm cavity size), at a pressure drop of 0.5bar across a 2m long packed bed (i.d.=71.7mm, flow=0.039kg/s), the forced convective bulk flow through the foam pellets was found to represent 38% of the total flow, thereby demonstrating the ease with which reactants could access the internal cavities of the metal foam pellet and hence the catalyst layer.In another example it is shown how a metal foam structure could be exploited in a high temperature fixed bed application (e.g. for endothermic reactions). Experiments were performed in a 74mm i.d. column, which contained different forms of catalyst supports, such that the depth of the fixed bed was 600mm. To represent a gaseous mixture in a process application, compressed air (e.g. 0.008kg/s) was electrically pre-heated (e.g. up to 500°C), and then fed into the fixed-bed which was surrounded by an electrical furnace (e.g. tube surface 650–950°C). From these experiments it was shown that, depending on the application, the metal foam structure could: (a) completely fill the channel as a continuous structure; (b) be used in the form of catalyst foam pellets; and (c) be installed with gaps between segments to exploit heat transfer by radiation (from the walls of the channel).

Organic chemistry. A rhodium catalyst for single-step styrene production from benzene and ethylene.

Rising global demand for fossil resources has prompted a renewed interest in catalyst technologies that increase the efficiency of conversion of hydrocarbons from petroleum and natural gas to higher-value materials. Styrene is currently produced from benzene and ethylene through the intermediacy of ethylbenzene, which must be dehydrogenated in a separate step. The direct oxidative conversion of benzene and ethylene to styrene could provide a more efficient route, but achieving high selectivity and yield for this reaction has been challenging. Here, we report that the Rh catalyst ((Fl)DAB)Rh(TFA)(η(2)-C2H4) [(Fl)DAB is N,N'-bis(pentafluorophenyl)-2,3-dimethyl-1,4-diaza-1,3-butadiene; TFA is trifluoroacetate] converts benzene, ethylene, and Cu(II) acetate to styrene, Cu(I) acetate, and acetic acid with 100% selectivity and yields ≥95%. Turnover numbers >800 have been demonstrated, with catalyst stability up to 96 hours.

A more direct way to synthesize styrene

Polymer Chemistry![Figure][1] Polystyrene pellets PHOTO: © BLICKWINKEL/ALAMY Foam cups, foam pellets, plastic cutlery: All are made of polystyrene, which in turn is made of styrene. The massive manufacturing scale of this commodity chemical places a premium on the efficiency of its synthesis. The current industrial route requires three steps to make styrene from benzene and ethylene. Vaughan et al. present a rhodium catalyst that achieves the coupling in a single step by using a recyclable copper salt as an oxidant. Although the catalyst is slow for industrial application, it demonstrates the viability of a more direct process. Science , this issue p. [421][2] [1]: pending:yes [2]: /lookup/doi/10.1126/science.aaa2260

SU‐C‐141‐04: Robustness of 4DCT and 4DCBCT Object Volume Measurement with a Motion‐Capable Lung Phantom That Mimics Realistic Patient Tumor Trajectories

Purpose: Accurate volume estimation for time‐resolved fan‐beam CT (4DCT) and cone‐beam CT (4DCBCT) is critical to planning and verification of many motion‐sensitive radiotherapy applications, including stereotactic lung radiotherapy. We used a 4D torso phantom to acquire realistic respiratory images with 4DCT and 4DCBCT, and compared object size estimation of the two modalities. Methods: A torso phantom consisting of a water‐filled sphere surrounded by foam pellets was driven by a motion device capable of reproducing patient respiratory traces. Ten typical respiratory traces were imaged along with static and sinusoidal cases with clinically‐relevant 4DCT and 4DCBCT techniques. 4DCT images were reconstructed in ten phases at 512×512×104 voxels and 0.977×0.977×2.50 mm3/voxel (GE Advantage). 4DCBCT images were reconstructed in ten phases at 128×205×205 voxels and 2.00×2.00×2.00 mm3/voxel (Elekta XVI). Objects were contoured in MIM 5.6.3 using threshold segmentation and volumes compared between image phases. Results: Reference object size was 7.03 mL and 7.01 mL for the static CT and CBCT acquisitions, respectively. When averaged over all phases, 4DCT volume was 6.78+/−0.72 mL; however, variation between phases was large and significant in Kruskal‐Wallis rank‐sum tests (2.68‐‐10.96 mL, p&lt;0.001). 4DCBCT showed reduced accuracy of object volume estimation relative to the static case and 4DCT in paired sign‐rank tests (μ =9.08+/−0.07 mL, p&lt;0.001); however, 4DCBCT greatly improved consistency of estimation, as no significant differences were detected between phases (8.47‐‐9.10 mL, p=0.4). Conclusion: Variation in object volume between respiratory phases was dramatically inferior for 4DCT versus 4DCBCT, possibly due to fan‐beam CT interplay effects or superiority of diaphragm sorting versus a linear surrogate. Consequently, radiotherapy planning or gating on individual phases of 4DCT datasets has potential to cause significant error. 4DCBCT did overestimate object size relative to 4DCT due to partial volume effects. As such, higher‐resolution 4DCBCT presets should be investigated for patient verification imaging.