PERFORMANCE EVALUATION OF NEW IMAGING TECHNOLOGIES FOR IN VIVO ASSESSMENT OF BONE HEALTH

Research has shown that quantitative assessment of bone microstructure can be beneficial for early detection of musculoskeletal conditions such as osteoarthritis and osteoporosis. However, bone microstructure cannot be accurately measured using current generation x-ray systems due to their limited spatial resolution. Therefore, the present clinical practice relies primarily on the image-based metric of Bone Mineral Density (BMD), which does not distinguish different arrangements of trabecular microarchitecture. We investigate whether the recently introduced computed tomography (CT) scanners with enhanced spatial resolution, specifically CMOS detector-based extremity Cone Beam CT (CBCT) and ultra-high resolution multi-detector CT (UHR-MDCT, e.g. Canon Aquilion Precision CT), could potentially enable quantitative assessment of trabecular microstructure in clinical settings. This could benefit the research, early detection, and monitoring of musculoskeletal conditions. The performance of the new imaging systems is evaluated for applications in conventional Trabecular Morphometrics (including metrics of trabecular thickness, spacing, number), in classification of trabeculae into Rods and Plates, and in texture analysis. Human cadaveric bone samples are used for the assessment. The biomarker results from the new imaging systems are compared to the gold-standard micro-CT. We also assess the accuracy and reproducibility of Bone Mineral Density (BMD) measurements on extremity CMOS-CBCT using data from a pilot human subject study. The study shows that CMOS-CBCT and UHR-MDCT are able to achieve improved bone microstructure measurements compared to conventional technologies. In terms of established biomarkers such as BMD and texture features, the new imaging systems provide a good degree of reproducibility, supporting the use of CMOS-CBCT and UHR-MDCT for those biomarkers in the same manner as currently done with conventional modalities. Our results offer motivation for future clinical translation of in vivo quantitative bone microstructure evaluation using the new high resolution CT technologies

High-Resolution Quantitative Cone-Beam Computed Tomography: Systems, Modeling, and Analysis for Improved Musculoskeletal Imaging

This dissertation applies accurate models of imaging physics, new high-resolution imaging hardware, and novel image analysis techniques to benefit quantitative applications of x-ray CT in in vivo assessment of bone health. We pursue three Aims: 1. Characterization of macroscopic joint space morphology, 2. Estimation of bone mineral density (BMD), and 3. Visualization of bone microstructure. This work contributes to the development of extremity cone-beam CT (CBCT), a compact system for musculoskeletal (MSK) imaging. Joint space morphology is characterized by a model which draws an analogy between the bones of a joint and the plates of a capacitor. Virtual electric field lines connecting the two surfaces of the joint are computed as a surrogate measure of joint space width, creating a rich, non-degenerate, adaptive map of the joint space. We showed that by using such maps, a classifier can outperform radiologist measurements at identifying osteoarthritic patients in a set of CBCT scans. Quantitative BMD accuracy is achieved by combining a polyenergetic model-based iterative reconstruction (MBIR) method with fast Monte Carlo (MC) scatter estimation. On a benchtop system emulating extremity CBCT, we validated BMD accuracy and reproducibility via a series of phantom studies involving inserts of known mineral concentrations and a cadaver specimen. High-resolution imaging is achieved using a complementary metal-oxide semiconductor (CMOS)-based x-ray detector featuring small pixel size and low readout noise. A cascaded systems model was used to performed task-based optimization to determine optimal detector scintillator thickness in nominal extremity CBCT imaging conditions. We validated the performance of a prototype scanner incorporating our optimization result. Strong correlation was found between bone microstructure metrics obtained from the prototype scanner and µCT gold standard for trabecular bone samples from a cadaver ulna. Additionally, we devised a multiresolution reconstruction scheme allowing fast MBIR to be applied to large, high-resolution projection data. To model the full scanned volume in the reconstruction forward model, regions outside a finely sampled region-of-interest (ROI) are downsampled, reducing runtime and cutting memory requirements while maintaining image quality in the ROI

METHODS FOR QUANTITATIVE ANALYSIS OF IN-VIVO BONE MICROSTRUCTURE USING COMPUTED TOMOGRAPHY

Bone health can be assessed by observing alterations in trabecular microarchitecture. These alterations are an early indicator for a range of musculoskeletal diseases ranging from osteoporosis to osteoarthritis. Fractures due to loss of bone are also seen in patients undergoing radiation therapy. Early detection of changes in the trabecular microstructure can be used to help design protocols and therapies targeting the factors affecting bone health. In-vivo evaluation if bone microarchitecture is still a challenge due to the limited spatial resolution provided by conventional computed tomography (CT). In this thesis, we investigate different high-resolution modalities to perform quantitative analysis of trabecular bone. New diagnostic imaging modalities with enhanced spatial resolution include Cone Beam CT (CBCT) systems with flat-panel detectors (FPD) and CMOS detectors. The FPD and CMOS detectors offer higher spatial resolution than the detectors in Conventional CT. Another example of a new modality with potential application in the imaging of trabecular microstructures is a recently introduces ultra–high resolution (UHR) multi-detector CT which has ~2x better spatial resolution than Conventional CT (Aquilion Precision CT, Canon Medical). We also investigate the performance of this novel Precision CT for trabecular microstructure imaging. The modalities are evaluated using bone morphometry parameters extracted from the scanned volumes. Bone metrics (including BV/TV, Tb.Th, Tb.Sp, and Tb.N, each defined below) are computed from the images obtained from CMOS-CBCT, FPD-CBCT, Conventional CT and Precision CT. These values are compared with the bone metrics obtained from analysis performed on Micro-CT (which is taken as a ‘gold standard’ reference and basis of comparison). Those studies involved imaging of cadaveric bone samples. A patient study is also performed to assess the feasibility of imaging trabecular structures in realistic clinical scenarios as opposed to a controlled experimental environment while imaging cadaveric samples. In cadaveric samples, imaging using CBCT achieves improved performance in quantification of bone microstructure. The methods and results offer motivation and a platform for ongoing development of quantitative imaging and evaluation of bone health in osteoporosis, osteoarthritis and bone loss due to radiation therapy

Cost-effective non-destructive testing of biomedical components fabricated using additive manufacturing

Biocompatible titanium-alloys can be used to fabricate patient-specific medical components using additive manufacturing (AM). These novel components have the potential to improve clinical outcomes in various medical scenarios. However, AM introduces stability and repeatability concerns, which are potential roadblocks for its widespread use in the medical sector. Micro-CT imaging for non-destructive testing (NDT) is an effective solution for post-manufacturing quality control of these components. Unfortunately, current micro-CT NDT scanners require expensive infrastructure and hardware, which translates into prohibitively expensive routine NDT. Furthermore, the limited dynamic-range of these scanners can cause severe image artifacts that may compromise the diagnostic value of the non-destructive test. Finally, the cone-beam geometry of these scanners makes them susceptible to the adverse effects of scattered radiation, which is another source of artifacts in micro-CT imaging. In this work, we describe the design, fabrication, and implementation of a dedicated, cost-effective micro-CT scanner for NDT of AM-fabricated biomedical components. Our scanner reduces the limitations of costly image-based NDT by optimizing the scanner\u27s geometry and the image acquisition hardware (i.e., X-ray source and detector). Additionally, we describe two novel techniques to reduce image artifacts caused by photon-starvation and scatter radiation in cone-beam micro-CT imaging. Our cost-effective scanner was designed to match the image requirements of medium-size titanium-alloy medical components. We optimized the image acquisition hardware by using an 80 kVp low-cost portable X-ray unit and developing a low-cost lens-coupled X-ray detector. Image artifacts caused by photon-starvation were reduced by implementing dual-exposure high-dynamic-range radiography. For scatter mitigation, we describe the design, manufacturing, and testing of a large-area, highly-focused, two-dimensional, anti-scatter grid. Our results demonstrate that cost-effective NDT using low-cost equipment is feasible for medium-sized, titanium-alloy, AM-fabricated medical components. Our proposed high-dynamic-range strategy improved by 37% the penetration capabilities of an 80 kVp micro-CT imaging system for a total x-ray path length of 19.8 mm. Finally, our novel anti-scatter grid provided a 65% improvement in CT number accuracy and a 48% improvement in low-contrast visualization. Our proposed cost-effective scanner and artifact reduction strategies have the potential to improve patient care by accelerating the widespread use of patient-specific, bio-compatible, AM-manufactured, medical components

Biomedical Engineering

Biomedical engineering is currently relatively wide scientific area which has been constantly bringing innovations with an objective to support and improve all areas of medicine such as therapy, diagnostics and rehabilitation. It holds a strong position also in natural and biological sciences. In the terms of application, biomedical engineering is present at almost all technical universities where some of them are targeted for the research and development in this area. The presented book brings chosen outputs and results of research and development tasks, often supported by important world or European framework programs or grant agencies. The knowledge and findings from the area of biomaterials, bioelectronics, bioinformatics, biomedical devices and tools or computer support in the processes of diagnostics and therapy are defined in a way that they bring both basic information to a reader and also specific outputs with a possible further use in research and development

Book of Abstracts 15th International Symposium on Computer Methods in Biomechanics and Biomedical Engineering and 3rd Conference on Imaging and Visualization

In this edition, the two events will run together as a single conference, highlighting the strong connection with the Taylor & Francis journals: Computer Methods in Biomechanics and Biomedical Engineering (John Middleton and Christopher Jacobs, Eds.) and Computer Methods in Biomechanics and Biomedical Engineering: Imaging and Visualization (JoãoManuel R.S. Tavares, Ed.). The conference has become a major international meeting on computational biomechanics, imaging andvisualization. In this edition, the main program includes 212 presentations. In addition, sixteen renowned researchers will give plenary keynotes, addressing current challenges in computational biomechanics and biomedical imaging. In Lisbon, for the first time, a session dedicated to award the winner of the Best Paper in CMBBE Journal will take place. We believe that CMBBE2018 will have a strong impact on the development of computational biomechanics and biomedical imaging and visualization, identifying emerging areas of research and promoting the collaboration and networking between participants. This impact is evidenced through the well-known research groups, commercial companies and scientific organizations, who continue to support and sponsor the CMBBE meeting series. In fact, the conference is enriched with five workshops on specific scientific topics and commercial software.info:eu-repo/semantics/draf

Optimization of Operation Sequencing in CAPP Using Hybrid Genetic Algorithm and Simulated Annealing Approach

In any CAPP system, one of the most important process planning functions is selection of the operations and corresponding machines in order to generate the optimal operation sequence. In this paper, the hybrid GA-SA algorithm is used to solve this combinatorial optimization NP (Non-deterministic Polynomial) problem. The network representation is adopted to describe operation and sequencing flexibility in process planning and the mathematical model for process planning is described with the objective of minimizing the production time. Experimental results show effectiveness of the hybrid algorithm that, in comparison with the GA and SA standalone algorithms, gives optimal operation sequence with lesser computational time and lesser number of iterations