High Geometric Fidelity Research Articles

Achieving high geometric fidelity in vat photopolymerization additive manufacturing through liquid surface support

The top-down vat photopolymerization (VPP) printing process, known for its extensive material adaptability and elimination of the release step between the printed object and the separation film, is widely used in 3D printing of advanced functional materials. However, for slurries that cannot achieve rapid self-leveling, edge morphology distortion in printed objects reduces geometric precision. This study investigated the issue of edge morphology distortion in the top-down VPP printing process, and proposes a liquid surface support (LSS) printing method that can be applied to general VPP printers. The results show that the protective slurry fence printed simultaneously with the object can provide excellent liquid surface support for the uncured layer above the printed object, which shifts the edge morphology distortion issue from the target object to the fence. The gap distance between the fence and the target sample is identified as the primary factor affecting edge morphology fidelity, which is influenced by surface tension. Finally, we successfully validated the application of the LSS printing method in the printing of ceramic dental prostheses and slender rod structures. This novel method significantly enhances the geometric precision of printed samples and is expected to promote the advancement of VPP printing applications for advanced functional materials.

Evolution of Self‐Assembled Lignin Nanostructure into Dendritic Fiber in Aqueous Biphasic Photocurable Resin for DLP‐Printing

AbstractThe design of lignin nanostructures where interfacial interactions enable enhanced entanglement of colloidal networks can broaden their applications in hydrogel‐based materials and light‐based 3D printing. Herein, an approach for fabricating surface‐active dendritic colloidal microparticles (DCMs) characterized by fibrous structures using nanostructured allylated lignin is proposed for the development of lignin‐based photocurable resins. With allyl‐terminated surface functionality of 0.61 mmol g−1, the entanglement between lignin‐DCM fibrils with a size of 1.4 µm successfully produces only lignin‐based hydrogels with structural integrity through photo‐crosslinking. The colloidal network of lignin dendricolloids reinforces the poly(ethylene glycol) (PEG) hydrogels during a digital light processing (DLP) 3D printing process by generating bicontinuous morphologies, resulting in six‐fold increases in toughness values with respect to the neat PEG hydrogel. The dual effectiveness of photoabsorption and free‐radical reactivity of lignin‐DCMs allow the light‐patterning of rather dilute PEG hydrogels (5–10%) with high geometric fidelity and structural complexity via DLP 3D printing. This study demonstrates a green and effective strategy for the design of 1D lignin‐DCMs that increases the versatility of the nanostructured biopolymer, opening up numerous opportunities for formulating functional hydrogels with robust structure‐property correlations.

High geometric fidelity through closed-loop control of the weld pool size in gas metal arc welding based direct energy deposition

Arc based direct energy deposition combines the flexibility of additive manufacturing with high build rates and low investment costs. However, high geometric fidelity of manufactured components is not possible with state-of-the-art methods. Highly varying and geometry-dependent boundary conditions, e.g. heat dissipation and the interpass temperature, are quasi-random influences with a strong impact on the geometric fidelity and the manufactured microstructure. Without adjusting for these variations, process stability decreases, geometric deviations become more likely and defects accumulate from layer to layer. A high geometric fidelity of the manufactured components can therefore not be guaranteed with the state of the art. Due to the large number of influencing variables in the arc-based manufacturing process, this problem cannot be solved by the definition of simple setpoints. Closed-loop control, however, offers the opportunity to flexibly counteract any deviations that occur by adjusting the process parameters in real time. Since the manufactured part is created by solidification from the weld pool, a closed-loop control of the weld pool size is being developed. The developed controller uses the weld pool properties and the interpass temperature as feedback variables and takes into account the non-linear system behaviour as well as the process noise and the parameter uncertainties. The subordinate control of the welding power source is further used for improved process stability. To the best of our knowledge, this solution provides a level of robustness, steady-state accuracy and geometric fidelity that has not been achieved by previous approaches reported in the literature. To illustrate the performance of this closed-loop control for components with low heat dissipation, we demonstrate the fabrication of thin-walled components with high geometric accuracy for a fast 3D printing process and investigate the influence of the welding process variables on the microstructure, the evaluation of the geometric fidelity is based on EN ISO 1101.

Delaunay meshes simplification with multi‐objective optimisation and fine tuning

Abstract3D meshes simplification plays an important role in many industrial domains. The two goals of Delaunay mesh simplification are maintaining high geometric fidelity and reducing mesh complexity. However, they are conflicting and cannot solved by gradient. Such limitation prevents existing Delaunay mesh simplification to obtain a small enough number of vertices and promising fidelity at the same time. To address these issues, this paper proposes an evolutionary multi‐objective approach for Delaunay mesh simplification. Firstly, the authors replace the previous fixed error‐bound threshold by the designed adaptive segment‐specific thresholds. Secondly, a constrained simplification is performed through a series of edge collapses that satisfy both Delaunay and error constraints. Next, the non‐dominated sorting genetic algorithm II (NSGA‐II) is employed to solve the multi‐objective problem to search for the optimal trade‐off threshold sequences. Finally, a fine‐tuning method is designed to further enhance the geometric fidelity of the simplified mesh. Experimental results demonstrate that the authors’ method consistently achieves a satisfactory balance between the approximation error and number of vertices, outperforming existing state‐of‐the‐art methods.

Repair of complex ovine segmental mandibulectomy utilizing customized tissue engineered bony flaps.

Craniofacial defects require a treatment approach that provides both robust tissues to withstand the forces of mastication and high geometric fidelity that allows restoration of facial architecture. When the surrounding soft tissue is compromised either through lack of quantity (insufficient soft tissue to enclose a graft) or quality (insufficient vascularity or inducible cells), a vascularized construct is needed for reconstruction. Tissue engineering using customized 3D printed bioreactors enables the generation of mechanically robust, vascularized bony tissues of the desired geometry. While this approach has been shown to be effective when utilized for reconstruction of non-load bearing ovine angular defects and partial segmental defects, the two-stage approach to mandibular reconstruction requires testing in a large, load-bearing defect. In this study, 5 sheep underwent bioreactor implantation and the creation of a load-bearing mandibular defect. Two bioreactor geometries were tested: a larger complex bioreactor with a central groove, and a smaller rectangular bioreactor that were filled with a mix of xenograft and autograft (initial bone volume/total volume BV/TV of 31.8 ± 1.6%). At transfer, the tissues generated within large and small bioreactors were composed of a mix of lamellar and woven bone and had BV/TV of 55.3 ± 2.6% and 59.2 ± 6.3%, respectively. After transfer of the large bioreactors to the mandibular defect, the bioreactor tissues continued to remodel, reaching a final BV/TV of 64.5 ± 6.2%. Despite recalcitrant infections, viable osteoblasts were seen within the transferred tissues to the mandibular site at the end of the study, suggesting that a vascularized customized bony flap is a potentially effective reconstructive strategy when combined with an optimal stabilization strategy and local antibiotic delivery prior to development of a deep-seated infection.

Data-driven conservation actions of heritage places curated with HBIM

Digital surveying tools provide a highly accurate geometric representation of cultural heritage sites in the form of point cloud data. With the recent advances in interoperability between point cloud data and Building Information Modelling (BIM), digital heritage researchers have introduced the Heritage/Historic Information Modelling (HBIM) notion to the field. As heritage data require safeguarding strategies to ensure their sustainability, the process is closely tied to conservation actions in the architectural conservation field. Focusing on the intersection of the ongoing trends in HBIM research and the global needs for heritage conservation actions, this paper tackles methodological pipelines for the data-driven management of archaeological heritage places. It illustrates how HBIM discourse could be beneficial for easing value-based decision-making in the conservation process. It introduces digital data-driven conservation actions by implementing a novel methodology for ancient building remains in Erythrae archaeological site (Turkey). The research ranges from a) surveying the in-situ remains and surrounding stones of the Heroon remains with digital photogrammetry and terrestrial laser scanning to b) designing a database system for building archaeology. The workflow offers high geometric fidelity and management of non-geometric heritage data by testing out the suitability and feasibility for the study of material culture and the physical assessment of archaeological building remains. This methodology is a fully data-enriched NURBS-based (non-uniform rational basis spline) three-dimensional (3D) model—which is integrated and operational in the BIM environment— for the holistic conservation process. Using a state-of-the-art digital heritage approach can be applied from raw data (initial stages) to decision-making about an archaeological heritage site (final stages). In conclusion, the paper offers a method for data-driven conservation actions, and given its methodological framework, it lends itself particularly well to HBIM-related solutions for building archaeology.

Blip up-down acquisition for spin- and gradient-echo imaging (BUDA-SAGE) with self-supervised denoising enables efficient T2 , T2 *, para- and dia-magnetic susceptibility mapping.

To rapidly obtain high resolution T2 , T2 *, and quantitative susceptibility mapping (QSM) source separation maps with whole-brain coverage and high geometric fidelity. We propose Blip Up-Down Acquisition for Spin And Gradient Echo imaging (BUDA-SAGE), an efficient EPI sequence for quantitative mapping. The acquisition includes multiple T2 *-, T2 '-, and T2 -weighted contrasts. We alternate the phase-encoding polarities across the interleaved shots in this multi-shot navigator-free acquisition. A field map estimated from interim reconstructions was incorporated into the joint multi-shot EPI reconstruction with a structured low rank constraint to eliminate distortion. A self-supervised neural network (NN), MR-Self2Self (MR-S2S), was used to perform denoising to boost SNR. Using Slider encoding allowed us to reach 1 mm isotropic resolution by performing super-resolution reconstruction on volumes acquired with 2 mm slice thickness. Quantitative T2 (=1/R2 ) and T2 * (=1/R2 *) maps were obtained using Bloch dictionary matching on the reconstructed echoes. QSM was estimated using nonlinear dipole inversion on the gradient echoes. Starting from the estimated R2 /R2 * maps, R2 ' information was derived and used in source separation QSM reconstruction, which provided additional para- and dia-magnetic susceptibility maps. In vivo results demonstrate the ability of BUDA-SAGE to provide whole-brain, distortion-free, high-resolution, multi-contrast images and quantitative T2 /T2 * maps, as well as yielding para- and dia-magnetic susceptibility maps. Estimated quantitative maps showed comparable values to conventional mapping methods in phantom and in vivo measurements. BUDA-SAGE acquisition with self-supervised denoising and Slider encoding enables rapid, distortion-free, whole-brain T2 /T2 * mapping at 1 mm isotropic resolution under 90 s.

Imaging Sensors and Systems 2022 Conference Overview and Papers Program

Solid state optical sensors and solid state cameras have established themselves as the imaging systems of choice for many demanding professional applications such as automotive, space, medical, scientific and industrial applications. The advantages of low-power, low-noise, high-resolution, high-geometric fidelity, broad spectral sensitivity, and extremely high quantum efficiency have led to a number of revolutionary uses. The conference will focus on image sensing topics as listed below, bringing together researchers, scientists, and engineers working in these fields, offering the opportunity for quick publication of their work.

On Orbital Determination of the Lunar-Based SAR Under Apsidal Precession

The signal propagation of the lunar-based synthetic aperture radar (LBSAR) is affected by perturbations of the lunar orbit, wherein the apsidal precession that exerts a significant impact on the LBSAR imaging performance of the LBSAR deserves special care. Accordingly, the orbital determination used to maintain well-focused quality and high geometric fidelity in the existing SAR system becomes critical for the LBSAR. In this article, through establishing criteria for the orbital determination of LBSAR based on its imaging performance under the influence of apsidal precession, we investigate the accuracy requirements for the LBSAR orbital determination in terms of the position and velocity determinations. Analysis results show that the required accuracy for the LBSAR position determination depends on the geometric fidelity in the range direction, while the accuracy requirement for the velocity determination is dominated by the azimuth positioning accuracy. The focusing quality is not a primary issue for the LBSAR orbital determination. In addition, the far look angle of LBSAR accounts for the highest accuracy requirement in the position and velocity determinations; thus, it can be treated as the optimum look angle for the LBSAR orbital determination. It is also found that both velocity and position determinations are challenging in the <inline-formula> <tex-math notation="LaTeX">${z}$ </tex-math></inline-formula>-direction for the LBSAR.

Numerical Simulation of the Fused Deposition Modeling for the Manufacturing of Parts with both High Geometric Fidelity and Mechanical Quality

With increasing usage of additive manufacturing methods for mechanical parts the need for precise and reliable simulations of the manufacturing process increases as well. In this paper various com- putations suited for simulating the fused deposition modeling process are considered in two dimensions. In fused deposition modeling a molten polymer is laid down on a prescribed path before the cooling of the melt begins. The occuring flows are treated as multiphase flows. To model the deposition of the filament, methods of computational fluid dynamics are used in ANSYS-Fluent, namely the volume of fluid method (VOF). Different numerical experiments are simulated

Efficient T2 mapping with blip-up/down EPI and gSlider-SMS (T2 -BUDA-gSlider).

To rapidly obtain high isotropic-resolution T2 maps with whole-brain coverage and high geometric fidelity. A T2 blip-up/down EPI acquisition with generalized slice-dithered enhanced resolution (T2 -BUDA-gSlider) is proposed. A RF-encoded multi-slab spin-echo (SE) EPI acquisition with multiple TEs was developed to obtain high SNR efficiency with reduced TR. This was combined with an interleaved 2-shot EPI acquisition using blip-up/down phase encoding. An estimated field map was incorporated into the joint multi-shot EPI reconstruction with a structured low rank constraint to achieve distortion-free and robust reconstruction for each slab without navigation. A Bloch simulated subspace model was integrated into gSlider reconstruction and used for T2 quantification. In vivo results demonstrated that the T2 values estimated by the proposed method were consistent with gold standard spin-echo acquisition. Compared to the reference 3D fast spin echo (FSE) images, distortion caused by off-resonance and eddy current effects were effectively mitigated. BUDA-gSlider SE-EPI acquisition and gSlider-subspace joint reconstruction enabled distortion-free whole-brain T2 mapping in 2 min at ~1 mm3 isotropic resolution, which could bring significant benefits to related clinical and neuroscience applications.

Interactive urban building energy modelling with functional mockup interface of a local residential building stock

The transformation towards a low carbon energy system requires municipalities to improve their local building stock. Urban building energy modelling (UBEM) is an emerging tool to support municipalities in shaping the necessary strategies by estimating energy demand with high spatial and temporal resolution. This study proposes a Functional Mockup Interface (FMI)-based UBEM that enables interactive capacities to simulate diverse environmental conditions without reinitialisation. The FMI-based approach allows to couple the building energy simulation EnergyPlus with external models. These capacities were tested on a real-world example in the German city of Wuppertal with urban microclimate data. The results are estimates of sub-hourly energy demand based on the adjacent environmental conditions of each building. In order to ameliorate the applicability, the FMI-based UBEM is further enriched by incorporating an automatic procedure to derive 3D building models, displaying high geometrical fidelity, from city-wide point clouds through the screened Poisson surface reconstruction algorithm. The study area contains 5736 residential buildings. A diverse residential building stock was modelled on the basis of the EU project TABULA. To demonstrate the functionality of the proposed UBEM, a demand response scenario was constructed with microclimate data and heat pumps instead of other heating and hot water systems. The capacity of UBE-FMI to dynamically change parameters (e.g. thermostat setpoint) in the building models can benefit the evaluation of demand response strategies and its potential to shed peak loads. In comparison with reference studies, UBE-FMI produced reasonable estimates of energy demand. The 3D building models and simulation results using “live” weather are visualized by a web-interface, which is implemented with the geospatial 3D framework NASA WorldWind.

Plastic Forming of Graphene Oxide Membranes into 3D Structures.

Flat, membrane-like materials made of graphene oxide (GO) nanoflakes have extraordinary mechanical properties including high stiffness, high strength, and low weight. However, the forming of complex nonplanar structures from flat GO membranes is difficult because of the intrinsic brittleness of GO. Here we present a simple and low-cost method to plasticize vacuum-filtrated GO membranes using a cellulose additive. Compared with the pure GO membrane, the GO-cellulose membranes had a lower Young's modulus but significantly improved ductility. Using the flat GO-cellulose membrane, we successfully embossed hemispherical caps with high geometrical fidelity, smooth surfaces, and no tearing or other damages to the membrane. The stiffness of the embossed 3D structure was increased further by cross-linking with a borax solution. Hemispherical caps made of 75 wt % GO with 25 wt % cellulose slurry combining borax cross-linking showed the highest stiffness. This study extends the applications of GO membranes and allows the harnessing of their extraordinary properties to nonplanar structures.

A VERSATILE MULTI-CAMERA SYSTEM FOR 3D ACQUISITION AND MODELING

Abstract. Image-based 3D models generation typically involves three stages, namely: 2D image acquisition, data processing, and 3D surface generation and editing. The availability of different easy-to-use and low-cost image acquisition solutions, combined with open-source or commercial processing tools, has democratized the 3D reconstruction and digital twin generation. But high geometric and texture fidelity on small- to medium-scale objects as well as integrated commercial system for mass 3D digitization are not available. The paper presents our effort to build such a system, i.e. a market-ready multi-camera solution and a customized reconstruction process for mass 3D digitization of small to medium objects. The system is realized as a joint work between industrial and academic partners, in order to employ the latest technologies for the needs of the market. The proposed versatile image acquisition and processing system pushes to the limits the 3D digitization pipeline combining a rigid capturing system with photogrammetric reconstruction methods.

High-fidelity, high-isotropic-resolution diffusion imaging through gSlider acquisition with and T1 corrections and integrated ΔB0 /Rx shim array.

and T1 corrections and dynamic multicoil shimming approaches were proposed to improve the fidelity of high-isotropic-resolution generalized slice-dithered enhanced resolution (gSlider) diffusion imaging. An extended reconstruction incorporating inhomogeneity and T1 recovery information was developed to mitigate slab-boundary artifacts in short-repetition time (TR) gSlider acquisitions. Slab-by-slab dynamic B0 shimming using a multicoil integrated ΔB0 /Rx shim array and high in-plane acceleration (Rinplane = 4) achieved with virtual-coil GRAPPA were also incorporated into a 1-mm isotropic resolution gSlider acquisition/reconstruction framework to achieve a significant reduction in geometric distortion compared to single-shot echo planar imaging (EPI). The slab-boundary artifacts were alleviated by the proposed and T1 corrections compared to the standard gSlider reconstruction pipeline for short-TR acquisitions. Dynamic shimming provided >50% reduction in geometric distortion compared to conventional global second-order shimming. One-millimeter isotropic resolution diffusion data show that the typically problematic temporal and frontal lobes of the brain can be imaged with high geometric fidelity using dynamic shimming. The proposed and T1 corrections and local-field control substantially improved the fidelity of high-isotropic-resolution diffusion imaging, with reduced slab-boundary artifacts and geometric distortion compared to conventional gSlider acquisition and reconstruction. This enabled high-fidelity whole-brain 1-mm isotropic diffusion imaging with 64 diffusion directions in 20 min using a 3T clinical scanner.

Distortion correction for high-resolution single-shot EPI DTI using a modified field-mapping method.

The widely used single-shot EPI (SS-EPI) diffusion tensor imaging (DTI) suffers from strong image distortion due to B0 inhomogeneity, especially for high-resolution imaging. Traditional methods such as the field-mapping method and the top-up method have various deficiencies in high-resolution SS-EPI DTI distortion correction. This study aims to propose a robust distortion correction approach, which combines the advantages of traditional methods and overcomes their deficiencies, for high-resolution SS-EPI DTI. The proposed correction method is based on the echo planar spectroscopic imaging field-mapping followed by an intensity correction procedure. To evaluate the efficacy of distortion correction, the proposed method was compared with the conventional field-mapping method and the top-up method, using a newly developed quantitative evaluation framework. The correction results were also compared with multi-shot EPI DTI to investigate whether the proposed method can provide high-resolution SS-EPI DTI with high geometric fidelity and high time efficiency. The results show that accurate field-mapping and intensity correction are critical to distortion correction in high-resolution SS-EPI DTI. The proposed method can provide more precise field maps and better correction results than the other two methods (p<0.0001), and the corrected images show higher geometric fidelity than those from MS-EPI DTI. An effective method is proposed to reduce image distortion in high-resolution SS-EPI DTI. It is practical to achieve high-resolution DTI with high time efficiency and high structure accuracy using this method.

Highly accelerated multishot echo planar imaging through synergistic machine learning and joint reconstruction.

To introduce a combined machine learning (ML)- and physics-based image reconstruction framework that enables navigator-free, highly accelerated multishot echo planar imaging (msEPI) and demonstrate its application in high-resolution structural and diffusion imaging. Single-shot EPI is an efficient encoding technique, but does not lend itself well to high-resolution imaging because of severe distortion artifacts and blurring. Although msEPI can mitigate these artifacts, high-quality msEPI has been elusive because of phase mismatch arising from shot-to-shot variations which preclude the combination of the multiple-shot data into a single image. We utilize deep learning to obtain an interim image with minimal artifacts, which permits estimation of image phase variations attributed to shot-to-shot changes. These variations are then included in a joint virtual coil sensitivity encoding (JVC-SENSE) reconstruction to utilize data from all shots and improve upon the ML solution. Our combined ML + physics approach enabled Rinplane × multiband (MB) = 8- × 2-fold acceleration using 2 EPI shots for multiecho imaging, so that whole-brain T2 and T2 * parameter maps could be derived from an 8.3-second acquisition at 1 × 1 × 3-mm3 resolution. This has also allowed high-resolution diffusion imaging with high geometrical fidelity using 5 shots at Rinplane × MB = 9- × 2-fold acceleration. To make these possible, we extended the state-of-the-art MUSSELS reconstruction technique to simultaneous multislice encoding and used it as an input to our ML network. Combination of ML and JVC-SENSE enabled navigator-free msEPI at higher accelerations than previously possible while using fewer shots, with reduced vulnerability to poor generalizability and poor acceptance of end-to-end ML approaches.

A High-Resolution Compression Scheme for Ray Tracing Subdivision Surfaces with Displacement

Subdivision surfaces, especially with displacement, are one of the key modeling primitives used in high-quality rendering environments, such as, e.g., movie production. While their use easily maps to rasterization-based frameworks, they pose a significant challenge for ray tracing environments. This is due to the fact that incoherent access patterns require storing or caching fully tessellated and displaced meshes for efficient intersection computations. In this paper we use a two-tier hierarchy built on a scene's patches. It relies on compressed and quantized bounding volumes on the second tier to reduce the size of the BVH itself. Based on this acceleration structure, we propose a quantized, compact approximation for leaf nodes while being faithful to the underlying patch-geometry. We build on recent advances and present a system that shows competitive performance regarding run-time speed, which is close to full-resolution pre-tessellation methods as well as to previous compression approaches. Ultimately, we provide strong compression of up to a factor of 5: 1 compared to state-of-the-art methods while maintaining high geometrical fidelity surpassing similarly compact approximations and getting close to uncompressed geometry.

Optimization of a novel large field of view distortion phantom for MR-only treatment planning.

Purpose MR‐only treatment planning requires images of high geometric fidelity, particularly for large fields of view (FOV). However, the availability of large FOV distortion phantoms with analysis software is currently limited. This work sought to optimize a modular distortion phantom to accommodate multiple bore configurations and implement distortion characterization in a widely implementable solution.Method and MaterialsTo determine candidate materials, 1.0 T MR and CT images were acquired of twelve urethane foam samples of various densities and strengths. Samples were precision‐machined to accommodate 6 mm diameter paintballs used as landmarks. Final material candidates were selected by balancing strength, machinability, weight, and cost. Bore sizes and minimum aperture width resulting from couch position were tabulated from the literature (14 systems, 5 vendors). Bore geometry and couch position were simulated using MATLAB to generate machine‐specific models to optimize the phantom build. Previously developed software for distortion characterization was modified for several magnet geometries (1.0 T, 1.5 T, 3.0 T), compared against previously published 1.0 T results, and integrated into the 3D Slicer application platform.ResultsAll foam samples provided sufficient MR image contrast with paintball landmarks. Urethane foam (compressive strength ∼1000 psi, density ~20 lb/ft3) was selected for its accurate machinability and weight characteristics. For smaller bores, a phantom version with the following parameters was used: 15 foam plates, 55 × 55 × 37.5 cm3 (L×W×H), 5,082 landmarks, and weight ~30 kg. To accommodate > 70 cm wide bores, an extended build used 20 plates spanning 55 × 55 × 50 cm3 with 7,497 landmarks and weight ~44 kg. Distortion characterization software was implemented as an external module into 3D Slicer's plugin framework and results agreed with the literature.ConclusionThe design and implementation of a modular, extendable distortion phantom was optimized for several bore configurations. The phantom and analysis software will be available for multi‐institutional collaborations and cross‐validation trials to support MR‐only planning.

Drug deposition in coronary arteries with overlapping drug-eluting stents

Drug-eluting stents are accepted as mainstream endovascular therapy, yet concerns for their safety may be under-appreciated. While failure from restenosis has dropped to below 5%, the risk of stent thrombosis and associated mortality remain relatively high. Further optimization of drug release is required to minimize thrombosis risk while maintaining therapeutic dose.The complex three-dimensional geometry of deployed stents together with the combination of diffusive and advective drug transport render an intuitive understanding of the situation exceedingly difficult. In situations such as this, computational modeling has proven essential, helping define the limits of efficacy, determine the mode and mechanism of drug release, and identify alternatives to avoid toxicity.A particularly challenging conformation is encountered in coronary arteries with overlapping stents. To study hemodynamics and drug deposition in such vessels we combined high-resolution, multi-scale ex vivo computed tomography with a flow and mass transfer computational model. This approach ensures high geometric fidelity and precise, simultaneous calculation of blood flow velocity, shear stress and drug distribution.Our calculations show that drug uptake by the arterial tissue is dependent both on the patterns of flow disruption near the wall, as well as on the relative positioning of drug-eluting struts. Overlapping stent struts lead to localized peaks of drug concentration that may increase the risk of thrombosis. Such peaks could be avoided by anisotropic stent structure or asymmetric drug release designed to yield homogeneous drug distribution along the coronary artery and, at the least, suggest that these issues need to remain in the forefront of consideration in clinical practice.