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1.
Sci Rep ; 10(1): 13164, 2020 Aug 04.
Artigo em Inglês | MEDLINE | ID: mdl-32753621

RESUMO

The often poorly orientated small-bowel mucosal biopsies taken for the diagnostics of celiac disease and other intestinal disorders are prone to misinterpretation. Furthermore, conventional histopathology has suboptimal sensitivity for early histopathological changes observed in short-term challenge studies. X-ray microtomography (micro-CT) is a promising new method for accurate imaging of human-derived biological samples. Here, we report that micro-CT could be utilized to create virtual reconstructions of endoscopically obtained intestinal biopsies. The formed digital 3D images enabled selection of always optimal cutting angles for accurate measurement of the mucosal damage and revealed diagnostic lesions in cases interpreted as normal with conventional histomorphometry. We also demonstrate that computer-assisted point cloud analysis can be used to calculate biologically meaningful surface areas of the biopsies in different stages of mucosal damage with excellent replicability and correlation with other disease parameters. We expect the improved diagnostic accuracy and capability to measure the surface areas to provide a powerful tool for the diagnostics of intestinal diseases and for future clinical and pharmaceutical trials.

2.
Sci Total Environ ; 731: 138955, 2020 Aug 20.
Artigo em Inglês | MEDLINE | ID: mdl-32417473

RESUMO

Short-term agronomic and environmental benefits are fundamental factors in encouraging farmers to use biochar on a broad scale. The short-term impacts of forest residue biochar (BC) on the productivity and carbon (C) storage of arable boreal clay soil were studied in a field experiment. In addition, rain simulations and aggregate stability tests were carried out to investigate the potential of BC to reduce nutrient export to surface waters. A BC addition of 30 t ha-1 increased soil test phosphorus and decreased bulk density in the surface soil but did not significantly change pH or water retention properties, and most importantly, did not increase the yield. There were no changes in the bacterial or fungal communities, or biomasses. Soil basal respiration was higher in BC-amended plots in the spring, but no differences in respiration rates were detected in the fall two years after the application. Rain simulation experiments did not support the use of BC in reducing erosion or the export of nutrients from the field. Of the C added, on average 80% was discovered in the 0-45 cm soil layer one year after the application. Amendment of boreal clay soil with a high rate of BC characterized by a moderately alkaline pH, low surface functionalities, and a recalcitrant nature, did not induce such positive impacts that would unambiguously motivate farmers to invest in BC. BC use seems unviable from the farmer's perspective but could play a role in climate change mitigation, as it will likely serve as long-term C storage.


Assuntos
Argila , Solo , Carvão Vegetal , Florestas
3.
J R Soc Interface ; 17(165): 20200102, 2020 04.
Artigo em Inglês | MEDLINE | ID: mdl-32228403

RESUMO

Micro-computed tomography (micro-CT) provides a means to analyse and model three-dimensional (3D) tissue engineering scaffolds. This study proposes a set of micro-CT-based tools firstly for evaluating the microstructure of scaffolds and secondly for comparing different cell seeding methods. The pore size, porosity and pore interconnectivity of supercritical CO2 processed poly(l-lactide-co-ɛ-caprolactone) (PLCL) and PLCL/ß-tricalcium phosphate scaffolds were analysed using computational micro-CT models. The models were supplemented with an experimental method, where iron-labelled microspheres were seeded into the scaffolds and micro-CT imaged to assess their infiltration into the scaffolds. After examining the scaffold architecture, human adipose-derived stem cells (hASCs) were seeded into the scaffolds using five different cell seeding methods. Cell viability, number and 3D distribution were evaluated. The distribution of the cells was analysed using micro-CT by labelling the hASCs with ultrasmall paramagnetic iron oxide nanoparticles. Among the tested seeding methods, a forced fluid flow-based technique resulted in an enhanced cell infiltration throughout the scaffolds compared with static seeding. The current study provides an excellent set of tools for the development of scaffolds and for the design of 3D cell culture experiments.

4.
J Funct Biomater ; 10(3)2019 Aug 13.
Artigo em Inglês | MEDLINE | ID: mdl-31412615

RESUMO

This study reports on the processing of three-dimensional (3D) chitosan/bioactive glass composite scaffolds. On the one hand, chitosan, as a natural polymer, has suitable properties for tissue engineering applications but lacks bioactivity. On the other hand, bioactive glasses are known to be bioactive and to promote a higher level of bone formation than any other biomaterial type. However, bioactive glasses are hard, brittle, and cannot be shaped easily. Therefore, in the past years, researchers have focused on the processing of new composites. Difficulties in reaching composite materials made of polymer (synthetic or natural) and bioactive glass include: (i) The high glass density, often resulting in glass segregation, and (ii) the fast bioactive glass reaction when exposed to moisture, leading to changes in the glass reactivity and/or change in the polymeric matrix. Samples were prepared with 5, 15, and 30 wt% of bioactive glass S53P4 (BonAlive ®), as confirmed using thermogravimetric analysis. MicrO-Computed tomography and optical microscopy revealed a flaky structure with porosity over 80%. The pore size decreased when increasing the glass content up to 15 wt%, but increased back when the glass content was 30 wt%. Similarly, the mechanical properties (in compression) of the scaffolds increased for glass content up to 15%, but decreased at higher loading. Ions released from the scaffolds were found to lead to precipitation of a calcium phosphate reactive layer at the scaffold surface. This is a first indication of the potential bioactivity of these materials. Overall, chitosan/bioactive glass composite scaffolds were successfully produced with pore size, machinability, and ability to promote a calcium phosphate layer, showing promise for bone tissue engineering and the mechanical properties can justify their use in non-load bearing applications.

5.
J Tissue Eng Regen Med ; 13(3): 406-415, 2019 03.
Artigo em Inglês | MEDLINE | ID: mdl-30644174

RESUMO

Deep osteochondral defects may leave voids in the subchondral bone, increasing the risk of joint structure collapse. To ensure a stable foundation for the cartilage repair, bone grafts can be used for filling these defects. Poly(lactide-co-glycolide) (PLGA) is a biodegradable material that improves bone healing and supports bone matrix deposition. We compared the reparative capacity of two investigative macroporous PLGA-based biomaterials with two commercially available bone graft substitutes in the bony part of an intra-articular bone defect created in the lapine femur. New Zealand white rabbits (n = 40) were randomized into five groups. The defects, 4 mm in diameter and 8 mm deep, were filled with neat PLGA; a composite material combining PLGA and bioactive glass fibres (PLGA-BGf); commercial beta-tricalcium phosphate (ß-TCP) granules; or commercial bioactive glass (BG) granules. The fifth group was left untreated for spontaneous repair. After three months, the repair tissue was evaluated with X-ray microtomography and histology. Relative values comparing the operated knee with its contralateral control were calculated. The relative bone volume fraction (∆BV/TV) was largest in the ß-TCP group (p ≤ 0.012), which also showed the most abundant osteoid. BG resulted in improved bone formation, whereas defects in the PLGA-BGf group were filled with fibrous tissue. Repair with PLGA did not differ from spontaneous repair. The PLGA, PLGA-BGf, and spontaneous groups showed thicker and sparser trabeculae than the commercial controls. We conclude that bone repair with ß-TCP and BG granules was satisfactory, whereas the investigational PLGA-based materials were only as good as or worse than spontaneous repair.


Assuntos
Regeneração Óssea/efeitos dos fármacos , Condrogênese/efeitos dos fármacos , Vidro/química , Osteogênese/efeitos dos fármacos , Copolímero de Ácido Poliláctico e Ácido Poliglicólico/farmacologia , Animais , Substitutos Ósseos/farmacologia , Feminino , Articulação do Joelho/diagnóstico por imagem , Articulação do Joelho/cirurgia , Coelhos , Microtomografia por Raio-X
6.
J Mater Sci Mater Med ; 29(10): 156, 2018 Oct 08.
Artigo em Inglês | MEDLINE | ID: mdl-30298429

RESUMO

The advantages of synthetic bone graft substitutes over autogenous bone grafts include abundant graft volume, lack of complications related to the graft harvesting, and shorter operation and recovery times for the patient. We studied a new synthetic supercritical CO2 -processed porous composite scaffold of ß-tricalcium phosphate and poly(L-lactide-co-caprolactone) copolymer as a bone graft substitute in a rabbit calvarial defect. Bilateral 12 mm diameter critical size calvarial defects were successfully created in 18 rabbits. The right defect was filled with a scaffold moistened with bone marrow aspirate, and the other was an empty control. The material was assessed for applicability during surgery. The follow-up times were 4, 12, and 24 weeks. Radiographic and micro-CT studies and histopathological analysis were used to evaluate new bone formation, tissue ingrowth, and biocompatibility. The scaffold was easy to shape and handle during the surgery, and the bone-scaffold contact was tight when visually evaluated after the implantation. The material showed good biocompatibility and its porosity enabled rapid invasion of vasculature and full thickness mesenchymal tissue ingrowth already at four weeks. By 24 weeks, full thickness bone ingrowth within the scaffold and along the dura was generally seen. In contrast, the empty defect had only a thin layer of new bone at 24 weeks. The radiodensity of the material was similar to the density of the intact bone. In conclusion, the new porous scaffold material, composed of microgranular ß-TCP bound into the polymer matrix, proved to be a promising osteoconductive bone graft substitute with excellent handling properties.


Assuntos
Substitutos Ósseos/química , Fosfatos de Cálcio/química , Poliésteres/química , Tecidos Suporte/química , Animais , Fenômenos Biomecânicos , Regeneração Óssea , Transplante Ósseo , Feminino , Teste de Materiais , Osteogênese , Porosidade , Coelhos , Crânio/cirurgia , Propriedades de Superfície
7.
R Soc Open Sci ; 5(8): 180811, 2018 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-30225072

RESUMO

The surgical reconstruction of functional neovagina is challenging and susceptible to complications. Therefore, developing tissue engineering-based treatment methods for vaginal defects is important. Our aim was to develop and test a novel supercritical carbon dioxide foamed poly-l-lactide-co-ɛ-caprolactone (scPLCL) scaffold for vaginal reconstruction. The scaffolds were manufactured and characterized for porosity (65 ± 4%), pore size (350 ± 150 µm) and elastic modulus (2.8 ± 0.4 MPa). Vaginal epithelial (EC) and stromal cells (SC) were isolated, expanded and characterized with flow cytometry. Finally, cells were cultured with scPLCL scaffolds in separate and/or co-cultures. Their attachment, viability, proliferation and phenotype were analysed. Both cell types strongly expressed cell surface markers CD44, CD73 and CD166. Strong expression of CD326 was detected with ECs and CD90 and CD105 with SCs. Both ECs and SCs attached and maintained viability on scPLCL. Further, scPLCL supported the proliferation of especially ECs, which also maintained epithelial phenotype (cytokeratin expression) during 14-day assessment period. Interestingly, ECs expressed uroplakin (UP) Ia, UPIb and UPIII markers; further, UPIa and UPIII expression was significantly higher on ECs cultured on scPLCL than on cell culture plastic. In conclusion, the scPLCL is potential scaffold for vaginal tissue engineering and the results of this study further illustrate the excellent biocompatibility of PLCL.

8.
Stem Cells Int ; 2018: 5928935, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29853915

RESUMO

Polybutylene succinate (PBS) is a biodegradable polyester with better processability and different mechanical properties compared to polylactides (PLAs), the most commonly used synthetic polymers in tissue engineering (TE). Since only few studies have evaluated PBS-containing materials for bone TE, we prepared PLA-PBS blends and analyzed material properties as well as cell attachment, proliferation, and osteogenic differentiation of human mesenchymal stem cells (hMSCs) on scaffolds. In addition to PLA, PBS, and PLA-PBS blends, PLA-polycaprolactone and PLA-poly(trimethylene carbonate) blends were evaluated. Polymer fibers were prepared using melt spinning. Pure PBS was observed to have the highest crystallinity and strain at break compared to the tougher PLA and PLA blends. No degradation occurred during the 4-week hydrolysis in either of the materials. Knitted and rolled scaffolds were manufactured, seeded with hMSCs, and cultured for 27 days. Human MSC viability was good on all the materials, but cell spreading along the fibers was only detected in PBS-containing scaffolds. They also induced the strongest proliferative response and osteogenic differentiation, which diminished with decreasing PBS content. Based on these results, PBS is superior to PLA with respect to hMSC attachment, proliferation, and osteogenesis. This encourages utilizing PBS-based biomaterials more widely in bone TE applications.

9.
Environ Sci Pollut Res Int ; 25(26): 25648-25658, 2018 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-28342082

RESUMO

Pore space characteristics of biochars may vary depending on the used raw material and processing technology. Pore structure has significant effects on the water retention properties of biochar amended soils. In this work, several biochars were characterized with three-dimensional imaging and image analysis. X-ray computed microtomography was used to image biochars at resolution of 1.14 µm and the obtained images were analysed for porosity, pore size distribution, specific surface area and structural anisotropy. In addition, random walk simulations were used to relate structural anisotropy to diffusive transport. Image analysis showed that considerable part of the biochar volume consist of pores in size range relevant to hydrological processes and storage of plant available water. Porosity and pore size distribution were found to depend on the biochar type and the structural anisotopy analysis showed that used raw material considerably affects the pore characteristics at micrometre scale. Therefore, attention should be paid to raw material selection and quality in applications requiring optimized pore structure.


Assuntos
Carvão Vegetal , Processamento de Imagem Assistida por Computador , Imageamento Tridimensional , Difusão , Porosidade , Água/química
10.
Materials (Basel) ; 10(11)2017 Nov 06.
Artigo em Inglês | MEDLINE | ID: mdl-29113141

RESUMO

Composite scaffolds were obtained by mixing various amounts (10, 30 and 50 weight % [wt %]) of borosilicate bioactive glass and poly(l-lactide-co-ε-caprolactone) (PLCL) copolymer. The composites were foamed using supercritical CO2. An increase in the glass content led to a decrease in the pore size and density. In vitro dissolution/reaction test was performed in simulated body fluid. As a function of immersion time, the solution pH increased due to the glass dissolution. This was further supported by the increasing amount of Ca in the immersing solution with increasing immersion time and glass content. Furthermore, the change in scaffold mass was significantly greater with increasing the glass content in the scaffold. However, only the scaffolds containing 30 and 50 wt % of glasses exhibited significant hydroxyapatite (HA) formation at 72 h of immersion. The compression strength of the samples was also measured. The Young's modulus was similar for the 10 and 30 wt % glass-containing scaffolds whereas it increased to 90 MPa for the 50 wt % glass containing scaffold. Upon immersion up to 72 h, the Young's modulus increased and then remained constant for longer immersion times. The scaffold prepared could have great potential for bone and cartilage regeneration.

11.
Biofabrication ; 9(2): 025001, 2017 04 12.
Artigo em Inglês | MEDLINE | ID: mdl-28402967

RESUMO

Reproduction of the anatomical structures and functions of tissues using cells and designed 3D scaffolds is an ongoing challenge. For this, scaffolds with appropriate biomorphic surfaces promoting cell attachment, proliferation and differentiation are needed. In this study, eight triply-periodic minimal surface (TPMS)-based scaffolds were designed using specific trigonometric equations, providing the same porosity and the same number of unit cells, while presenting different surface curvatures. The scaffolds were fabricated by stereolithography using a photocurable resin based on the biocompatible, biodegradable and rubber-like material, poly(trimethylene carbonate) (PTMC). A numerical approach was developed to calculate the surface curvature distributions of the TPMS architectures. Moreover, the scaffolds were characterized by scanning electron microscopy, micro-computed tomography and water permeability measurements. These original scaffold architectures will be helpful to decipher the biofunctional role of the surface curvature of scaffolds intended for tissue engineering applications.


Assuntos
Engenharia Tecidual/métodos , Tecidos Suporte/química , Dioxanos/química , Microscopia Eletrônica de Varredura , Modelos Teóricos , Distribuição Normal , Permeabilidade , Porosidade , Reprodutibilidade dos Testes , Propriedades de Superfície , Água , Microtomografia por Raio-X
12.
J Orthop Res ; 34(5): 745-53, 2016 05.
Artigo em Inglês | MEDLINE | ID: mdl-26573959

RESUMO

The purpose of this study was to investigate the potential of a novel recombinant human type II collagen/polylactide scaffold (rhCo-PLA) in the repair of full-thickness cartilage lesions with autologous chondrocyte implantation technique (ACI). The forming repair tissue was compared to spontaneous healing (spontaneous) and repair with a commercial porcine type I/III collagen membrane (pCo). Domestic pigs (4-month-old, n = 20) were randomized into three study groups and a circular full-thickness chondral lesion with a diameter of 8 mm was created in the right medial femoral condyle. After 3 weeks, the chondral lesions were repaired with either rhCo-PLA or pCo together with autologous chondrocytes, or the lesion was only debrided and left untreated for spontaneous repair. The repair tissue was evaluated 4 months after the second operation. Hyaline cartilage formed most frequently in the rhCo-PLA treatment group. Biomechanically, there was a trend that both treatment groups resulted in better repair tissue than spontaneous healing. Adverse subchondral bone reactions developed less frequently in the spontaneous group (40%) and the rhCo-PLA treated group (50%) than in the pCo control group (100%). However, no statistically significant differences were found between the groups. The novel rhCo-PLA biomaterial showed promising results in this proof-of-concept study, but further studies will be needed in order to determine its effectiveness in articular cartilage repair. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:745-753, 2016.


Assuntos
Doenças das Cartilagens/terapia , Cartilagem Articular/lesões , Condrócitos/transplante , Tecidos Suporte , Animais , Colágeno Tipo II , Feminino , Análise de Elementos Finitos , Humanos , Poliésteres , Distribuição Aleatória , Suínos , Microtomografia por Raio-X
13.
Mater Sci Eng C Mater Biol Appl ; 56: 457-66, 2015 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-26249615

RESUMO

Bone tissue engineering requires highly porous three-dimensional (3D) scaffolds with preferable osteoconductive properties, controlled degradation, and good dimensional stability. In this study, highly porous 3D poly(d,l-lactide-co-glycolide) (PLGA) - bioactive glass (BG) composites (PLGA/BG) were manufactured by combining highly porous 3D fibrous BG mesh skeleton with porous PLGA in a freeze-drying process. The 3D structure of the scaffolds was investigated as well as in vitro hydrolytic degradation for 10weeks. The effect of BG on the dimensional stability, scaffold composition, pore structure, and degradation behaviour of the scaffolds was evaluated. The composites showed superior pore structure as the BG fibres inhibited shrinkage of the scaffolds. The BG was also shown to buffer the acidic degradation products of PLGA. These results demonstrate the potential of these PLGA/BG composites for bone tissue engineering, but the ability of this kind of PLGA/BG composites to promote bone regeneration will be studied in forthcoming in vivo studies.


Assuntos
Vidro/química , Poliglactina 910/química , Tecidos Suporte/química , Regeneração Óssea , Porosidade , Engenharia Tecidual
14.
Hear Res ; 326: 59-65, 2015 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-25922206

RESUMO

Cone-beam computed tomography (CBCT) plays a key role in cochlear implantation in both planning implantation before surgery and quality control during surgery due to the high spatial resolution and convenience of application in the operation theater. We recently designed a novel, highresolution cone-beam acquisition system that has been tested in temporal bones with cochlear implantation to identify the scalar localization of the electrode arrays. The current study aimed to verify the reliability of the experimental CBCT set-up using high-resolution in vitro X-ray microtomography (µCT) imaging as a reference. Nine human temporal bones were studied by inserting a straight electrode of a cochlear implant using the round window approach followed by sequential imaging using experimental CBCT and µCT with and without 1% iodine as the contrast agent. In the CBCT images, the electrodes were located in the scala tympani and near the lateral wall in all temporal bones. In the µCT images, the cochlear fine structures, including Reissner's membrane, stria vascularis, spiral ligament, basilar membrane, spiral limbus, osseous spiral lamina, and Rosenthal's canal that hosts the spiral ganglion cells, were clearly delineated; the electrode array avoided the lateral wall of the scala tympani in the hook region and then ran along the lateral wall of the scala tympani without any exception, a feature that was also detected in a temporal bone with ruptures in the basilar and Reissner's membranes. In conclusion, the current in vitro µCT imaging system produced high-quality images that could demonstrate the fine cochlear structures faithfully and verify the reliability of a novel experimental CBCT set-up aimed for clinical application in identifying the scalar localization of the electrode array. The straight electrode is safe for cochlear structures with low risk of translocation and is suitable for atraumatic implantation, although a large gap between the contacts and the modiolus exists.


Assuntos
Implante Coclear/métodos , Implantes Cocleares , Tomografia Computadorizada de Feixe Cônico/métodos , Janela da Cóclea/diagnóstico por imagem , Janela da Cóclea/cirurgia , Microtomografia por Raio-X/métodos , Cadáver , Humanos , Reprodutibilidade dos Testes
15.
J Nanobiotechnology ; 13: 5, 2015 Jan 27.
Artigo em Inglês | MEDLINE | ID: mdl-25622551

RESUMO

BACKGROUND: Silver nanoparticles (Ag NPs) displayed strong activities in anti-bacterial, anti-viral, and anti-fungal studies and were reportedly efficient in treating otitis media. Information on distribution of AgNPs in different compartments of the ear is lacking. OBJECTIVE: To detect distribution of Ag NPs in the middle and inner ear and transportation pathways after transtympanic injection. METHODS: Contrast effect of Ag NPs in the micro CT imaging was assessed in a phantom. AgNPs at various concentrations (1.85 mM, 37.1 mM, and 370.7 mM) were administered to rat middle ear using transtympanic injection and cadaver heads were imaged using micro CT at several time points. RESULTS: The lowest concentration of Ag NPs that could be visualized using micro CT was 37.1 mM. No difference was observed between the solvents, deionized H2O and saline. Ag NPs at 37.1 mM were visible in the middle ear on 7 d post-administration. Ag NPs at 370.7 mM generated signals in the middle ear, ossicular chain, round window membrane, oval window, scala tympani, and Eustachian tube for both 4 h and 24 h time points. A gradient distribution of Ag NPs from the middle ear to the inner ear was detected. The pathways for Ag NPs to be transported from the middle ear into the inner ear are round and oval windows. CONCLUSION: This study provided the imaging evidence that Ag NPs are able to access the inner ear in a dose-dependent manner after intratympanic administration, which is relevant to design the delivery concentration in the future clinic application in order to avoid adverse inner ear effect.


Assuntos
Orelha Interna/efeitos dos fármacos , Orelha Média/efeitos dos fármacos , Nanopartículas Metálicas/administração & dosagem , Prata/farmacocinética , Microtomografia por Raio-X/métodos , Animais , Meios de Contraste , Relação Dose-Resposta a Droga , Orelha Interna/metabolismo , Orelha Média/metabolismo , Injeção Intratimpânica , Masculino , Nanopartículas Metálicas/análise , Perilinfa/efeitos dos fármacos , Imagens de Fantasmas , Ratos Sprague-Dawley , Sensibilidade e Especificidade , Distribuição Tecidual
16.
Conf Proc IEEE Eng Med Biol Soc ; 2015: 5626-9, 2015 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-26737568

RESUMO

Methods to image and assess the microstructure of polymer based biomaterials in liquid phase, for example cell culture medium, are well warranted. X-ray microtomography could provide a mean to visualize and analyze such structures. However, the density of such polymers is close to that of water and hence the X-ray contrast is poor. Moreover, if the biomaterials contain cells and are dried, the cell morphology may be distorted. In this paper we test phosphotungstic acid (PTA) staining to improve the contrast. We imaged collagen and PLA samples with µCT in air, water and alcohol. The methods were compared visually and with contrast to noise ratio calculated from the images. Our results demonstrate that with alcohol the PLA can be imaged also in liquid phase. PTA staining seems to be a good method to increase the contrast for collagen in µCT imaging.


Assuntos
Microtomografia por Raio-X , Materiais Biocompatíveis , Colágeno , Poliésteres
17.
Conf Proc IEEE Eng Med Biol Soc ; 2014: 2484-7, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-25570494

RESUMO

This paper describes the creation of an anatomically detailed high resolution model of the human head based on the Visible Human Female data from the National Library of Medicine archives. Automatic and semi-automatic segmentation algorithms were applied over the 3 image volumes ­ CT, MRI and anatomical cryo-sections of the cadaver ­ to label a total of 23 tissues. The results were combined to create a labeled volume of the head with voxel dimensions of 0.33×0.33×0.33 mm. The individual label matrices and their corresponding surface meshes are made available to be used freely. The detailed blood vessel network and ocular tissues will be of interest in computational modelling and simulation studies.


Assuntos
Cabeça/anatomia & histologia , Modelos Anatômicos , Anatomia Transversal , Feminino , Cabeça/diagnóstico por imagem , Humanos , Imagem por Ressonância Magnética , Pessoa de Meia-Idade , Tomografia Computadorizada por Raios X
18.
J Biomech ; 47(1): 264-8, 2014 Jan 03.
Artigo em Inglês | MEDLINE | ID: mdl-24290177

RESUMO

Large mandibular continuity defects pose a significant challenge in oral maxillofacial surgery. One solution to this problem is to use computer-guided surgical planning and additive manufacturing technology to produce patient-specific reconstruction plates. However, when designing customized plates, it is important to assess potential biomechanical responses that may vary substantially depending on the size and geometry of the defect. The aim of this study was to assess the design of two customized plates using finite element method (FEM). These plates were designed for the reconstruction of the lower left mandibles of two ameloblastoma cases (patient 1/plate 1 and patient 2/plate 2) with large bone resections differing in both geometry and size. Simulations revealed maximum von Mises stresses of 63 MPa and 108 MPa in plates 1 and 2, and 65 MPa and 190 MPa in the fixation screws of patients 1 and 2. The equivalent strain induced in the bone at the screw-bone interface reached maximum values of 2739 micro-strain for patient 1 and 19,575 micro-strain for patient 2. The results demonstrate the influence of design on the stresses induced in the plate and screw bodies. Of particular note, however, are the differences in the induced strains. Unphysiologically high strains in bone adjacent to screws can cause micro-damage leading to bone resorption. This can adversely affect the anchoring capabilities of the screws. Thus, while custom plates offer optimal anatomical fit, attention should be paid to the expected physiological forces on the plates and the induced stresses and strains in the plate-screw-bone assembly.


Assuntos
Parafusos Ósseos , Processamento de Imagem Assistida por Computador/métodos , Mandíbula/cirurgia , Procedimentos Cirúrgicos Reconstrutivos/métodos , Estresse Mecânico , Adulto , Placas Ósseas , Simulação por Computador , Feminino , Análise de Elementos Finitos , Humanos , Fixadores Internos , Masculino , Mandíbula/anatomia & histologia , Pessoa de Meia-Idade , Pressão , Software , Tomografia Computadorizada por Raios X/métodos
19.
J Biomater Appl ; 28(4): 529-43, 2013 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-23048066

RESUMO

There is an increasing need for synthetic bone substitute materials that decrease the need for allografts and autografts. In this study, composites of ß-tricalcium phosphate and a biodegradable poly(L-lactide-co-ε-caprolactone) were manufactured using extrusion to form biodegradable composites with high ß-tricalcium phosphate contents for osteoconductivity. The hydrolytic degradation of the composites containing 0, 10, 20, 35 and 50% of ß-tricalcium phosphate was studied in vitro for 52 weeks. During the study, it was observed that ß-tricalcium phosphate did not have an effect on the degradation rate of the polymer matrix. However, the crystallinity of the materials increased throughout the test series and changes in glass transition temperatures were also observed as the comonomer ratio of the polymer matrix changed as the degradation proceeded. The results show that the materials have desirable degradation properties and, thus, possess great potential as bioabsorbable and osteoconductive bone filling materials.


Assuntos
Materiais Biocompatíveis , Fosfatos de Cálcio/química , Poliésteres/química , Tampões (Química) , Varredura Diferencial de Calorimetria , Concentração de Íons de Hidrogênio , Hidrólise , Microscopia Eletrônica de Varredura , Estrutura Molecular , Peso Molecular , Microtomografia por Raio-X
20.
Bioelectromagnetics ; 29(5): 363-70, 2008 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-18247366

RESUMO

The aim of this study was a dosimetrical analysis of the setup used in the exposure of the heads of domestic pigs to GSM-modulated radio frequency electromagnetic fields (RF-EMF) at 900 MHz. The heads of pigs were irradiated with a half wave dipole using three different exposure routines; short bursts of 1-3 s at two different exposure levels and a continuous 10-min exposure. The electroencephalogram (EEG) was registered continuously during the exposures to search for RF-EMF originated changes. The dosimetry was based on simulations with the anatomical heterogeneous numerical model of the pig head. The simulation results were validated by experimental measurements with the exposure dipole and a homogeneous liquid phantom resembling the pig head. The specific absorption rate (SAR), defined as a maximum average over 10 g tissue mass (SAR(10g)), was 7.3 W/kg for the first set of short bursts and 31 W/kg for the second set of short bursts. The SAR(10g) in the continuous 10-min exposure was 31 W/kg. The estimated uncertainty for the dosimetry was +/-25% (K = 2).


Assuntos
Telefone Celular , Exposição Ambiental , Cabeça/fisiologia , Cabeça/efeitos da radiação , Micro-Ondas , Radiometria/instrumentação , Anestesia , Animais , Desenho de Equipamento , Análise de Falha de Equipamento , Radiometria/métodos , Suínos
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