Micro-computed Tomography System Research Articles

Investigations into the Geometric Calibration and Systematic Effects of a Micro-CT System.

Micro-Computed Tomography (µCT) systems are used for examining the internal structures of various objects, such as material samples, manufactured parts, and natural objects. Resolving fine details or performing accurate geometric measurements in the voxel data critically depends on the precise calibration of the µCT systems geometry. This paper presents a calibration method for µCT systems using projections of a calibration phantom, where the coordinates of the phantom are initially unknown. The approach involves detecting and tracking steel ball bearings and adjusting the unknown system geometry parameters using non-linear least squares optimization. Multiple geometric models are tested to verify their suitability for a self-calibration approach. The implementation is tested using a calibration phantom captured at different magnifications. The results demonstrate the system's capability to determine the geometry model parameters with a remaining error on the detector between 0.27 px and 0.18 px. Systematic errors that remain after calibration, as well as changing parameters due to system instabilities, are investigated. The source code of this work is published to enable further research.

Correlation of Microstructural Features within Short Carbon Fiber/ABS Manufactured via Large-Area Additive- Manufacturing Beads

Short carbon fiber-reinforced polymer composites are widely used in polymer extrusion additive manufacturing (AM), including large-area additive manufacturing (LAAM), due to their enhanced mechanical properties as compared to neat polymers. However, the mechanical properties of these composites depend on microstructural characteristics, including fibers and micro-voids, which are determined during processing. In this work, the correlation between fibers and micro-voids within the microstructure of LAAM polymer composites throughout various processing stages of short carbon fiber-reinforced acrylonitrile butadiene styrene (SCF/ABS) is investigated. The processing stages considered here include the incoming pellets, a single freely extruded strand, a single regularly deposited bead, and a single regularly deposited bead pressed by a mechanical roller. A high-resolution X-ray micro-computed tomography (µCT) system is employed to characterize the microstructural features in terms of the fibers (volume fraction, fiber orientation tensor) and micro-voids (volume fraction, sphericity) in the SCF/ABS samples. The results indicate that micro-voids exist within the microstructure of the SCF/ABS composite in all four stages considered here and that the micro-void volume fraction and micro-void sphericity vary among the test samples. Moreover, the results show a considerable variation in fiber orientation and fiber volume fraction within the microstructure throughout all the stages considered; however, all the samples show the highest alignment in the extrusion/print direction. Furthermore, a correlation is identified between the fiber orientation and the micro-void volume fraction within samples from all four stages considered here. This finding suggests that fibers tend to align more in the extrusion/print direction in regions with less micro-void content.

Characterisation of pore structure of bulk wheat mixed with dockage using X-ray micro-computed tomography and deep learning

Characterisation of pore structure inside grain bulks is essential for predicting the airflow resistance during grain drying and aeration. Herein, the 3D pore network of wheat mixed with different percentages of canola and dockage was characterised. The characterised parameters include pore size, throat length, coordination number, airpath length, and tortuosity. To simulate the grain storage condition, the loaded wheat mixtures were cured using wax at 110 °C. The images of the waxed wheat mixtures were produced by using a high-resolution X-ray micro-computed tomography (μCT) system at a resolution of 50 μm per pixel. The computed space distribution was based on the 3D medial axis analysis of each image stack using Dragonfly 4.1 software. The pore space was segmented using a deep-learning model with 90.1–98.0% accuracy. A watershed-based image algorithm was used to generate the pore network from the segmented pore space. The pore structure parameters were extracted from the pore network of each wheat mixture. Most pores were classified as mesopores (>99%) in a range from 62.5 to 4000 μm, with less than 1% classified as micropores (1–62.5 μm). The mean pore size of clean bulk wheat was 648 ± 403 μm with a mean throat length of 1115 ± 611 μm. In the mixtures with 10% canola, 5 and 10% wheat dockage, the mean pore size was reduced by 10%, 29%, and 17%, respectively, from clean wheat. Adding canola and dockage generally influenced the connectivity in the pore microstructure with changes in bulk porosity, tortuosity, airpath number, and length.

Algorithm to determine local basis weight of random fibrous networks with X-ray microtomography and SEM images

Analysis of the basis weight for random fibrous networks is important to understand their microstructure, properties and performance. Two-dimensional microscopical images show in-plane fibers without giving any information on their distribution in three dimensions. This research introduces a fully parametric algorithm for computing the local basis weight of random fibrous networks using three-dimensional images because out-of-plane fiber orientation is important, especially for high-density or thick networks. Voxel models of real nonwoven webs were generated by an X-ray micro-computed tomography system. The developed algorithm could accurately estimate a local basis weight value for random fibrous networks produced with various manufacturing parameters. Numerical results computed with the developed method were compared with those obtained with a physical weight measurement technique. The algorithm was tested and validated for various nonwoven fabrics with different densities. It was observed that the developed method can be used to examine and/or compare the basis weight of a wide range of random fibrous networks. In addition, it can be used to predict the basis weight for fabrics, especially in a new product development process.

Analyzing the microstructure of cemented fills adding polypropylene-glass fibers with X-ray micro-computed tomography

Fiber reinforced cementitious tailings backfill (FRCTB) is progressively employed in mining industry due to its high strength/stiffness-to-weight ratio. However, the wide use of the FRCTB technique requires further study of the practice of many different types of fibers, either alone or in combination. In this regard, this paper explores the impact of composite (glass-polypropylene) fibers on microstructure of FRCTBs considering weak surface and pore characteristics. The fractures of backfills were quantitatively analyzed by a non-destructive X-ray micro-computed tomography system which permits imagining of the interior microstructures of backfills via the construction of 3D volumetric data in diverse spatial scales. Quantitative parameters cover percent weak surface, porosity, and pore sphericity. The spatial distribution of weak surfaces, pores, and fissures and the bridging effect of fibers were also analyzed based on the 3D reconstruction technique. Adding fibers increased the percentage of FRCTB's weak surface. The greater the glass fiber dose, the larger the percentage of the weak surface. Composite fibers can lessen FRCTB's porosity. The smallest FRCTB porosity was 0.07 % for glass and PP fiber contents of 0.4 wt% and 0.2 wt%, respectively. A rise in glass fiber dose causes a rise in volume of 10–100 mm3 pore content. Fibers have a greater impact on the volume of 0.1–100 mm3 pores, and the rise in glass fiber dose deteriorates shape of this type of pores, leading to a reduction in the sphericity of this type of pores. There is a clear correlation between the distribution patterns of weak surfaces, pores, and fissures along the height of the specimens. Weak surfaces and pores are prone to develop as fractures. Fibers can limit the crack expansion in FRCTB. Lastly, this study presents a time- and cost-saving method for analyzing FRCTB's microstructure.

Comparison of Performance of Micro-Computed Tomography (Micro-CT) and Synchrotron Radiation CT in Assessing Coronary Stenosis Caused by Calcified Plaques in Coronary Artery Phantoms

Synchrotron-radiation-computed tomography (SRCT) allows more accurate calcified plaque and coronary stenosis assessment as a result of its superior spatial resolution; however, typical micro-computed tomography (micro-CT) systems have even higher resolution. The purpose of this study was to compare the performance of high-resolution micro-CT with SRCT in the assessment of calcified plaques and a previously published dataset of coronary stenosis assessment. This experimental study involved micro-CT scanning of three-dimensional printed coronary artery models with calcification in situ used in our previously published SRCT study on coronary stenosis assessment. Measurements of coronary stenosis utilizing both modalities were compared using a paired sample t-test. The degrees of stenosis measured on all but one micro-CT dataset were statistically significantly lower than the corresponding SRCT measurements reported in our previous paper (p < 0.0005–0.05). This indicates that the superior spatial resolution of micro-CT was able to further reduce over-estimation of stenosis caused by extensive calcification of coronary arteries and, hence, false positive results. Our results showed that the high-resolution micro-CT used in this study outperformed the Australian Synchrotron SRCT in both calcified plaque and coronary stenosis assessment. These findings will become clinically important for cardiovascular event prediction and enable reclassification of individuals with low and intermediate risk into appropriate risk categories when the technical challenges of micro-CT in clinical practice such as the small field of view and demanding on image processing power are addressed.

Kinetics and modeling of Pb (II) adsorption in pellet biochar based on micro-computed tomography characterization

Biochar, a cost-effective adsorbent for the removal of heavy metals from aqueous solutions, has gained increasing attention. In this study, an advanced micro-computed tomography (micro-CT) system was used to investigate the adsorption kinetics by direct localization and visualization of Pb (II) on wheat straw pellet biochar. The normalized digital images indicating the dynamic changes of Pb (II) adsorption on biochar samples at different initial Pb (II) concentrations of 100, 200, 300, and 400 mg/L and adsorption times were obtained. It was found that image grayscale (GS) changes over adsorption time (t) followed the power function, GSe/GSt=2.45∗t-0.27. Based on this finding, modified pseudo-first-order (PFO) and pseudo-second-order (PSO) models incorporated with time-dependent kinetic constants kPFOt=KPFO∗GSe/GSt and kPSOt=KPSO∗GSe/GSt were proposed, resulting in a better interpretation of the adsorption mechanism. The micro-CT-guided novel approach demonstrated visual evidence-based superiority and should prove valuable to the existing body of research in related fields.

An injectable copolymer of fatty acids (ARA 3000 BETA) as a promising treatment for osteoarthritis

Osteoarthritis (OA) is the most prevalent rheumatic disease and a fast growing cause of disability. Current pharmacological treatments include antalgics and non-steroid anti-inflammatory drugs to control pain and inflammation as well as slow acting drugs such as intra-articular (IA) administration of hyaluronic acid. Oral supplementation or diet rich in polyunsaturated free fatty acids are proposed but evidence for benefit is still under debate. We here investigated the therapeutic potential of ARA 3000 BETA, an injectable copolymer of fatty acids, at the structural level in OA. Collagenase-induced osteoarthritis model was induced in C57BL/6 mice by collagenase injection into knee joint. Mice were treated with one or two IA or four intra-muscular injections (IM) of ARA 3000 BETA. At sacrifice, knee joints were recovered for cartilage analysis by confocal laser scanning microscopy (CLSM) and bone analysis by micro-computed tomography system. OA histological scoring was performed after safranin O/fast green staining. Histological analysis revealed a protective effect against cartilage degradation in treated knee joints after IM and IA administration. This was confirmed by CLSM with a significant improvement of all articular cartilage parameters, including thickness, volume and surface degradation whatever the administration route. A slight protective effect was also noticed on subchondral bone parameters and knee joint calcification after IM administration and to a lesser extent, two IA injections. We demonstrated the therapeutic efficacy of injectable ARA 3000 BETA in OA with a protection against cartilage and bone alterations providing the proof-of-concept that clinical translation might be envisioned to delay disease progression.

Evaluation of a half-digital technique for fabricating customized post-cores: A pilot study

ObjectivesThe current half-digital post-core fabrication technique can replace the conventional methods; however, it does not consider the impact occlusion has on the digital design. This study proposed a half-digital workflow that integrated intracanal impression with dentition scanning, and evaluated the accuracy of the post-cores fabricated by it. MethodsStandard models with three extracted teeth (a central incisor, a premolar, and a molar) were prepared. Eight post-cores were fabricated for each tooth by the half-digital technique and eight by the conventional technique as controls. Scanning was performed with a microcomputed tomography system. The volume of the overall space (VOS) between the post and canal wall, the space areas in three standardized sections (A, B, and C), and the apical gap (AG) were calculated and statistically analyzed using two-way analysis of variance. Statistical significance was set at p < 0.05. ResultsThe two techniques differed significantly in the VOS (p < 0.05), section B (p < 0.05), and AG (p < 0.05) of all three teeth but not for sections A (p = 0.099) and C (p = 0.636). ConclusionsThe half-digital technique investigated in this study could produce better-fitting customized post-cores than the conventional technique.

Micro-computed tomography in endodontics

In recent years, biomedical and dental researchers have started using micro-computed tomography (MCT) for research purposes. Due to a wide range of technological developments in various sources of X-ray and X-ray imaging techniques, the use of MCT in experimental studies has been improved. MCT systems allow researchers to analyze microstructures, differences in density, and morphological changes. This review article emphasizes on the recent advancements of MCT applied in endodontics. MCT applications in the analysis of root canal morphology, evaluation of biomechanical preparation, irrigation and intracanal medicament extrusion, restoration of root canal, and retreatment have been summarized.

Effect of Process Parameters on Void Distribution, Volume Fraction, and Sphericity within the Bead Microstructure of Large-Area Additive Manufacturing Polymer Composites.

Short carbon fiber-reinforced composite materials produced by large-area additive manufacturing (LAAM) are attractive due to their lightweight, favorable mechanical properties, multifunctional applications, and low manufacturing costs. However, the physical and mechanical properties of short carbon-fiber-reinforced composites 3D printed via LAAM systems remain below expectations due in part to the void formation within the bead microstructure. This study aimed to assess void characteristics including volume fraction and sphericity within the microstructure of 13 wt% short carbon fiber acrylonitrile butadiene styrene (SCF/ABS). Our study evaluated SCF/ABS as a pellet, a single freely extruded strand, a regularly deposited single bead, and a single bead manufactured with a roller during the printing process using a high-resolution 3D micro-computed tomography (µCT) system. Micro voids were shown to exist within the microstructure of the SCF/ABS pellet and tended to become more prevalent in a single freely extruded strand which showed the highest void volume fraction among all the samples studied. Results also showed that deposition on the print bed reduced the void volume fraction and applying a roller during the printing process caused a further reduction in the void volume fraction. This study also reports the void's shape within the microstructure in terms of sphericity which indicated that SCF/ABS single freely extruded strands had the highest mean void sphericity (voids tend to be more spherical). Moreover, this study evaluated the effect of printing process parameters, including nozzle temperature, extrusion speed and nozzle height above the printing table on the void volume fraction and sphericity within the microstructure of regularly deposited single beads.

Morinda officinalis polysaccharide attenuates osteoporosis in rats underwent bilateral ovariectomy by suppressing the PGC-1α/PPARγ pathway.

Osteoporosis (OP) is a widespread disease that causes risks of spine and hip fractures. Morinda officinalis polysaccharide (MOP) shows therapeutic potential in OP. This article intended to understand the mechanism by which MOP impacts bone mineral density (BMD) and serum trace elements in OP rats. OP rat models were established by bilateral ovariectomy (OVX). Rats were intragastrically administered with MOP or ZLN005 [the activator of peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α)] since the first day after operation for 8 weeks. Microstructural changes in OP rats were analyzed using micro-computed tomography system. Contents of serum Zn, Cu, Fe, and Mg in rats were measured. Levels of serum superoxide dismutase (SOD), glutathione peroxidase (GSH-PX), GSH, and malondialdehyde (MDA) in rats were determined by Enzyme-linked immunosorbent assay. Protein levels of PGC-1α and peroxisome proliferator-activated receptor γ (PPARγ) in cartilage tissues of rats were determined via Western blotting. MOP enhanced BMD, bone volume per trabecular volume (BV/TV), Tb.N, and Tb.Th and reduced Tb.Sp in the distal femur of OVX rats, elevated levels of serum Cu, Fe, and Mg and contents of SOD, GSH, and GSH-PX and decreased MDA content. Moreover, MOP suppressed the PGC-1α/PPARγ pathway. Activation of PGC-1α partially abolished the action of MOP on ameliorating OP in OVX rats and strengthening anti-oxidation ability. MOP mitigated OP in OVX rats by inhibiting the PGC-1α/PPARγ pathway.

Abstract 6184: Kras Co-mutations lead to resistance to mutant TP53 targeted therapy in mouse models of spontaneous non-small cell lung cancer

Abstract Background: Lung cancer results in more than 131,000 deaths per year with estimated 236,000 new cases in 2021 in the United States. About 85% of lung cancers are non-small cell lung cancer (NSCLC). TP53 is an important tumor-suppressor and about 50% of human lung NSCLCs contain a mutant TP53. Targeting of mutant p53 is very limited due to the lack of drugs. PRIMA-1 is a first in class anti-mutant TP53 molecule with the ability to induce apoptosis by restoring the wild-type function of TP53 through covalently binding and modifying thiol groups in the central domain of the mutated protein. Recently, the FDA granted breakthrough therapy designation to the PRIMA-1 methylated analog, APR-246 in combination with azacytidine for the treatment of patients with myelodysplastic syndromes and a TP53 mutation. The major setback of targeted therapy today continues to be resistance. Herein, we report our findings related to resistance to PRIMA-1 targeted therapy in spontaneous P53 mutant driven NSCLC. Methods: We have previously reported the generation of a line of transgenic mice with a human mutant p53(273H) expressed in a lung-specific manner. Human mutant TP53 expression was regulated under the transcriptional control of the human surfactant protein C (SP-C) promoter. After the age of 12 months, the mice developed spontaneous lung adenocarcinomas. We treated SPC-p53-273H lung tumor mice via intraperitoneal injection (i.p) with PRIMA-1 at a dose of 100 mg/kg in 0.2 mL PBS every other day for two weeks. The tumors were identified using micro-computed tomography (micro-CT) system and pre-and post-treatment diameters were estimated based on the CT image. K-ras status was analyzed by PCR-based Sanger sequencing. Results: Of the 10 lung tumor-bearing mice treated with PRIMA-1, micro-CT derived sum of the largest diameters indicated that six mice (60%) experienced tumor volume reductions whereas four mice experienced tumor volume increase. Sequencing analysis showed five tumors contained K-ras mutations (two p.G12D, one p.G12F, one p.G12V and one p.Q61L). On average, lung tumor diameter had a 31% reduction post-treatment of PRIMA-1 for the lung tumors containing wild-type K-ras gene. Whereas it increased 18% on the average post-treatment of PRIMA-1 for the lung tumors containing a mutant K-ras gene. There is a significant difference statistically (p = 0.016) in the response to the treatment of PRIMA-1 between the mutant K-ras cohort and the wild-type K-ras cohort. Conclusion: PRIMA 1 therapy results in antitumor activity against P53 mutant lung tumors. However, the presence of K-ras co-mutation is a significant resistance factor. Combination of APR-246 and K-ras inhibitor therapy would be needed to overcome this resistance. Citation Format: David T. Costa, Shaylyn Grier, Melanie Perez, Li Gao, Miguel A. Villalona-Calero, Wenrui Duan. Kras Co-mutations lead to resistance to mutant TP53 targeted therapy in mouse models of spontaneous non-small cell lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 6184.

Performance evaluation of a micro-CT system for laboratory animal imaging with iterative reconstruction capabilities.

In recent years, there has been a rapid proliferation in micro-computed tomography (micro-CT) systems becoming more available for routine preclinical research, with applications in many areas, including bone, lung, cancer, and cardiac imaging. Micro-CT provides the means to non-invasively acquire detailed anatomical information, but high-resolution imaging comes at the cost of longer scan times and higher doses, which is not desirable given the potential risks related to x-ray radiation. To achieve dose reduction and higher throughputs without compromising image quality, fewer projections can be acquired. This is where iterative reconstruction methods can have the potential to reduce noise since these algorithms can better handle sparse projection data, compared to filtered backprojection PURPOSE: We evaluate the performance characteristics of a compact benchtop micro-CT scanner that provides iterative reconstruction capabilities with GPU-based acceleration. We thereby investigate the potential benefit of iterative reconstruction for dose reduction. Based on a series of phantom experiments, the benchtop micro-CT system was characterized in terms of image uniformity, noise, low contrast detectability, linearity, and spatial resolution. Whole-body images of a plasticized ex vivo mouse phantom were also acquired. Different acquisition protocols (general-purpose versus high-resolution, including low dose scans) and different reconstruction strategies (analytic versus iterative algorithms: FDK, ISRA, ISRA-TV) were compared. Signal uniformity was maintained across the radial and axial field-of-view (no cupping effect) with an average difference in Hounsfield units (HU) between peripheral and central regions below 50. For low contrast detectability, regions with at least ∆HU of 40 to surrounding material could be discriminated (for rods of 2.5mm diameter). A high linear correlation (R2 =0.997) was found between measured CT values and iodine concentrations (0-40mg/ml). Modulation transfer function (MTF) calculations on a wire phantom evaluated a resolution of 10.2 lp/mm at 10% MTF that was consistent with the 8.3% MTF measured on the 50µm bars (10 lp/mm) of a bar-pattern phantom. Noteworthy changes in signal-to-noise and contrast-to-noise values were found for different acquisition and reconstruction protocols. Our results further showed the potential of iterative reconstruction to deliver images with less noise and artefacts. In summary, the micro-CT system that was evaluated in the present work was shown to provide a good combination of performance characteristics between image uniformity, low contrast detectability, and resolution in short scan times. With the iterative reconstruction capabilities of this micro-CT system in mind (ISRA and ISRA-TV), the adoption of such algorithms by GPU-based acceleration enables the integration of noise reduction methods which here demonstrated potential for high-quality imaging at reduced doses.

N-acetylcysteine promotes cyclic mechanical stress-induced osteogenic differentiation of periodontal ligament stem cells by down-regulating Nrf2 expression

Background/purposeMechanical stress plays a vital role in osteogenic differentiation of periodontal ligament stem cells (PDLSCs). Cyclic mechanical stress may up-regulate reactive oxygen species (ROS) level. N-acetylcysteine (NAC) possesses powerful antioxidant capacity. However, it is undefined the impact of NAC on osteogenic differentiation stimulated by cyclic mechanical stress in PDLSCs. The aim of our research was to study the effect of NAC on PDLSCs during osteogenic differentiation under cyclic mechanical stress. Materials and methodsThe expression levels of osteogenesis markers were used to examine the osteogenic differentiation of PDLSCs. ROS production were measured by flow cytometry. The levels of reduced glutathione (GSH) and oxidized glutathione (GSSG) were analyzed. We also examined the changes of alveolar bone and periodontal ligament (PDL) tissues in orthodontic rats by micro-computed tomography (micro-CT) system and immunohistochemistry (IHC) staining. The nuclear factor erythroid-2-related factor-2 (Nrf2) expression was examined. ResultsNAC could enhance the osteogenic differentiation and up-regulate the GSH level as well as the ratio of GSH/GSSG, while down-regulate ROS generation and Nrf2 expression induced by cyclic mechanical stress in PDLSCs. NAC had beneficial effects on the microstructure of alveolar bone and enhanced the expression levels of osteogenesis markers, such as alkaline phosphatase (ALP) and collagen type 1 (COL1) in PDL in orthodontic rats at the tension side. ConclusionNAC could improve the osteogenic differentiation stimulated by cyclic mechanical stress in PDLSCs and in orthodontic rats, suggesting a potential therapeutic approach for alveolar bone remodeling in orthodontics.

Abstract 1351: Targeting mutant p53 protein in spontaneous non-small cell lung cancers in transgenic mice

Abstract Background: Restoration of p53 function in cancer cells is an important approach for cancer therapy because p53 mutations are found in many human cancers, including lung cancers. An anti-mutant p53 agent, p53 reactivation and induction of massive apoptosis (PRIMA-1) has been used to restore the function of the mutant p53 to its wildtype function. Examination of PRIMA-1-induced tumor suppression has indicated the potential role of microRNAs (miRNAs) in the regulation of oncogene or tumor suppressor gene expression. However, the anti-tumor effect of the PRIMA-1 in the treatment of spontaneous lung cancer is still unclear. Methods: We developed a lung tumor model in transgenic mice in which the human mutant p53(273H) is expressed in a lung-specific manner, under the control of the surfactant protein C promoter. These mice developed lung adenocarcinomas after the age of 12 months. We treated SPC-p53-273H lung tumor-bearing mice via intraperitoneal injection (i.p) with PRIMA-1 at a dose of 100 mg/kg in 0.2 ml PBS every other day for three weeks. Lung tumor-bearing mice were identified with a micro-computed tomography (micro-CT) system and pre-and post-treatment tumor volumes were estimated based on the micro-CT image. miRNA expressions were analyzed with the NanoString nCounter Analysis System. Results: Of the 11 treated mice, micro-CT-derived volume changes indicated that five p53-273H mice were responsive to the PRIMA-1 treatment, with an average volume decrease of 93.55 mm3. Four of the treated mice experienced tumor growth post-treatment, with an average volume increase of 74.96 mm3. The remaining two p53-273H mice did not experience a significant change in tumor size. Compared against the control group, the PRIMA-1 treated p53-273H mice showed an overall decrease in tumor size, with an average tumor volume fold change of -2.33. The untreated controls showed a fold change of 8.16, nearly four times that of the treated cohort. Over 500 microRNA were compared between the treated and the control tumors by the NanoString nCounter array analysis. Seven microRNA were identified to have experienced a significant increase (greater than 2 folds) in expression in response to the PRIMA-1 treatment. Fifty-nine miRNAs displayed a significant decrease in expression (less than -2 folds). Conclusion: The results of the study indicated a significant reduction in tumor size in the mice treated with PRIMA-1, based on micro-CT images. Contrary to this finding, an increased average fold change was seen in the control group, indicating an overall average increase in tumor volume. The results indicate the activity of PRIMA-1 in lung tumor-bearing P53 mutant transgenics and suggest the potential feasibility of using PRIMA-1 (APR-246) to treat lung cancer. In addition, microRNA may potentially be involved in the anti-cancer property of PRIMA-1. Further investigation is needed to elucidate the mechanisms in PRIMA-1 induced apoptosis. Citation Format: Shaylyn Grier, Li Gao, Melanie Perez, Wenrui Duan. Targeting mutant p53 protein in spontaneous non-small cell lung cancers in transgenic mice [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1351.

Focus on lasers, imaging, microscopy, and nanoscience

Focus on lasers, imaging, microscopy, and nanoscience

Effects of various thicknesses and levels of mineral trioxide aggregate coronal plugs on nanoleakage and fracture resistance in revascularization: An invitro study.

The aim of this study was to evaluate the effects of mineral trioxide aggregate (MTA) applied at varying levels and thickness in the cervical region of the root on the leakage and fracture resistance of the simulated immature teeth. 3 study groups (n = 16) (Group 1: 2 mm MTA, Group 2: 4 mm MTA, Group 3: 2 mm MTA+2 mm RMGIC below cementoenamel junction) and 2 control groups (Group 4: Complete canal obturation, Group 5: No coronal plug) were used for the study. Nanoleakage was measured using a micro-computed tomography system. For the fracture resistance test, a universal testing machine was used. The amount of silver nitrate penetration decreased while MTA thicknesses increased (P < 0.001). However, the placement of MTA as a thicker layer did not make any additional contribution on the fracture resistance (P > 0.05). The 4-mm coronal MTA plug can be suggested in RETs for its superior sealing and reinforcement abilities.

Evaluation of Different Root Canal Obturation Techniques in Internal Root Resorption of Three-Dimensional Printed Teeth Manufactured Using Computer Software.

The objective of this study was to evaluate and compare the filling ability of various root canal obturation techniques on the internal root resorption (IRR) cavities of replicated tooth samples manufactured using computer software and a three-dimensional (3D) printer. Orthographic images and root structures of a healthy upper maxilla central incisor in determined volumes and sizes were drawn as a prototype with the aid of computer software. Using the same software, an IRR defect was also modeled. These two images were then transferred to the AutoDesk Fusion 360 3D modeling program (AutoDesk, San Rafael, CA) for meshing. Afterward, the tooth model was transferred to a 3D modeling and prototyping program (RhinoCeros 3D; Robert McNells & Assoc., New York) and printed on a 3D printer. Eighty replicas with IRR were manufactured and divided into four groups (n = 20 per group) according to the obturating techniques as follows: Group 1: Cold lateral compaction (CLC), Group 2: Core Carrier System (GuttaCore), Group 3: Injectable Cold Filling (GuttaFlow® BioSeal), and Group 4: Continuous Wave Obturation System (Elements Free). After root canal filling, replicas were scanned with a high-resolution micro-computed tomography system (SkyScan 1172; Bruker-microCT, Kontich, Belgium), data regarding voids (unobturated areas) inside the IRR defects were statistically analyzed using nonparametric Kruskal-Wallis tests. A pairwise comparison between the tested groups showed that Groups 3 and 4 had significantly fewer voids compared with Groups 1 and 2 in IRR defects (p < 0.05). Group 1/Group 2 and Group 3/Group 4 had similar results in terms of voids and there were no statistically significant differences (p > 0.05). The injectable cold filling system (GuttaFlow BioSeal) and the injectable continuous wave obturation system (Elements Free) successfully obturated the pathological IRR irregularities when compared with CLC and core carrier (GuttaCore) systems.

Investigations on fracture in reinforced concrete beams in 3-point bending using continuous micro-CT scanning

This study explores a fracture process in rectangular reinforced concrete (RC) beams subjected to quasi-static three-point bending. RC beams were short and long with included longitudinal reinforcement in the form of a steel or basalt bar. The ratio of the shear span to the effective depth was 1.5 and 0.75. The focus was on the load–deflection diagram and crack formation. Three-dimensional (3D) analyses of the size and distribution of pores and cracks were carried out with an X-ray micro-computed tomography system SkyScan 1173 of high resolution that is a very valuable non-destructive tool for studying a 3D material interior. The tomography system was connected with a quasi-static loading machine ISTRON 5569 to continuously follow fracture changes without loading breaks. The beams failed in shear due to a diagonal shear crack that was steeper with basalt reinforcement. The shear strength and flexural strength of RC beams with steel reinforcement were higher by about 10% than of RC beams with basalt reinforcement. The deflection corresponding to the maximum load of RC beams was higher by about 20–25% in RC beams with basalt reinforcement due to its lower basalt modulus of elasticity. The final volume of cracks in beams reinforced with basalt bars was higher by about 9–20% than in concrete beams reinforced with steel bars due to a higher beam deflection whereas the maximum crack width in concrete beams reinforced with basalt bars was higher by about 20–40% than in concrete beams reinforced with steel bars. The critical shear crack in RC beams with basalt reinforcement was wider by about 20–40% and steeper by about 10–45% as compared to concrete beams with steel reinforcement. The relationship between the crack volume and beam deflection was bi-linear. Both, aggregate breakage and crack branching occurred during beam bending.