Nonrigid Registration of Monomodal MRI Using Linear Viscoelastic Model

This paper describes a method for nonrigid registration of monomodal MRI based on physical laws. The proposed method assumes that the properties of image deformations are like those of viscoelastic matter, which exhibits the properties of both an elastic solid and a viscous fluid. Therefore, the deformation fields of the deformed image are constrained by both sets of properties. After global registration, the local shape variations are assumed to have the properties of the Maxwell model of linear viscoelasticity, and the deformation fields are constrained by the corresponding partial differential equations. To speed up the registration, an adaptive force is introduced according to the maximum displacement of each iteration. Both synthetic datasets and real datasets are used to evaluate the proposed method. We compare the results of the linear viscoelastic model with those of the fluid model on the basis of both the standard and adaptive forces. The results demonstrate that the adaptive force increases in both models and that the linear viscoelastic model improves the registration accuracy

Nonrigid Image Registration Using Physically Based Models

It is well known that biological structures such as human brains, although may contain the same global structures, differ in shape, orientation, and fine structures across individuals and at different times. Such variabilities during registration are usually represented by nonrigid transformations. This research seeks to address this issue by developing physically based models in which transformations are constructed to obey certain physical laws. In this thesis, a novel registration technique is presented based on the physical behavior of particles. Regarding the image as a particle system without mutual interaction, we simulate the registration process by a set of free particles moving toward the target positions under applied forces. The resulting partial differential equations are a nonlinear hyperbolic system whose solution describes the spatial transformation between the images to be registered. They can be numerically solved using finite difference methods. This technique extends existing physically based models by completely excluding mutual interaction and highly localizing image deformations. We demonstrate its performance on a variety of images including two-dimensional and three-dimensional, synthetic and clinical data. Deformable images are achieved with sharper edges and clearer texture at less computational cost

Planning Framework for Robotic Pizza Dough Stretching with a Rolling Pin

Stretching a pizza dough with a rolling pin is a nonprehensile manipulation. Since the object is deformable, force closure cannot be established, and the manipulation is carried out in a nonprehensile way. The framework of this pizza dough stretching application that is explained in this chapter consists of four sub-procedures: (i) recognition of the pizza dough on a plate, (ii) planning the necessary steps to shape the pizza dough to the desired form, (iii) path generation for a rolling pin to execute the output of the pizza dough planner, and (iv) inverse kinematics for the bi-manual robot to grasp and control the rolling pin properly. Using the deformable object model described in Chap. 3, each sub-procedure of the proposed framework is explained sequentially

Variational methods for modeling and simulation of tool-tissue interaction

Ph.DDOCTOR OF PHILOSOPH

Meshfree and Particle Methods in Biomechanics: Prospects and Challenges

The use of meshfree and particle methods in the field of bioengineering and biomechanics has significantly increased. This may be attributed to their unique abilities to overcome most of the inherent limitations of mesh-based methods in dealing with problems involving large deformation and complex geometry that are common in bioengineering and computational biomechanics in particular. This review article is intended to identify, highlight and summarize research works on topics that are of substantial interest in the field of computational biomechanics in which meshfree or particle methods have been employed for analysis, simulation or/and modeling of biological systems such as soft matters, cells, biological soft and hard tissues and organs. We also anticipate that this review will serve as a useful resource and guide to researchers who intend to extend their work into these research areas. This review article includes 333 references

Biomechanics and Remodelling for Design and Optimisation in Oral Prosthesis and Therapeutical Procedure

The purpose of dental prostheses is to restore the oral function for edentulous patients. Introducing any dental prosthesis into mouth will alter biomechanical status of the oral environment, consequently inducing bone remodelling. Despite the advantageous benefits brought by dental prostheses, the attendant clinical complications and challenges, such as pain, discomfort, tooth root resorption, and residual ridge reduction, remain to be addressed. This thesis aims to explore several different dental prostheses by understanding the biomechanics associated with the potential tissue responses and adaptation, and thereby applying the new knowledge gained from these studies to dental prosthetic design and optimisation. Within its biomechanics focus, this thesis is presented in three major clinical areas, namely prosthodontics, orthodontics and dental implantology. In prosthodontics, the oral mucosa plays a critical role in distributing occlusal forces a denture to the underlying bony structure, and its response is found in a complex, dynamic and nonlinear manner. It is discovered that interstitial fluid pressure in mocosa is the most important indicator to the potential resorption induced by prosthetic denture insertion, and based on this finding, patient-specific analysis is performed to investigate the effects caused by various types of dentures and prediction of the bone remodelling activities. In orthodontic treatments, a dynamic algorithm is developed to analyse and predict potential bone remodelling around the target tooth during orthodontic treatment, thereby providing a numerical approach for treatment planning. In dental implantology, a graded surface morphology of an implant is designed to improve osseointegration over that of a smooth uniform surface in both the short and long term. The graded surface can be optimised to achieve the best possible balance between the bone-implant contact and the peak Tresca stress for the specific clinical application need

A review of bioengineering techniques applied to breast tissue: Mechanical properties, tissue engineering and finite element analysis

Female breast cancer was the most prevalent cancer worldwide in 2020, according to the Global Cancer Observatory. As a prophylactic measure or as a treatment, mastectomy and lumpectomy are often performed at women. Following these surgeries, women normally do a breast reconstruction to minimize the impact on their physical appearance and, hence, on their mental health, associated with self-image issues. Nowadays, breast reconstruction is based on autologous tissues or implants, which both have disadvantages, such as volume loss over time or capsular contracture, respectively. Tissue engineering and regenerative medicine can bring better solutions and overcome these current limitations. Even though more knowledge needs to be acquired, the combination of biomaterial scaffolds and autologous cells appears to be a promising approach for breast reconstruction. With the growth and improvement of additive manufacturing, three dimensional (3D) printing has been demonstrating a lot of potential to produce complex scaffolds with high resolution. Natural and synthetic materials have been studied in this context and seeded mainly with adipose derived stem cells (ADSCs) since they have a high capability of differentiation. The scaffold must mimic the environment of the extracellular matrix (ECM) of the native tissue, being a structural support for cells to adhere, proliferate and migrate. Hydrogels (e.g., gelatin, alginate, collagen, and fibrin) have been a biomaterial widely studied for this purpose since their matrix resembles the natural ECM of the native tissues. A powerful tool that can be used in parallel with experimental techniques is finite element (FE) modeling, which can aid the measurement of mechanical properties of either breast tissues or scaffolds. FE models may help in the simulation of the whole breast or scaffold under different conditions, predicting what might happen in real life. Therefore, this review gives an overall summary concerning the human breast, specifically its mechanical properties using experimental and FE analysis, and the tissue engineering approaches to regenerate this particular tissue, along with FE models

Advanced Sensing and Image Processing Techniques for Healthcare Applications

This Special Issue aims to attract the latest research and findings in the design, development and experimentation of healthcare-related technologies. This includes, but is not limited to, using novel sensing, imaging, data processing, machine learning, and artificially intelligent devices and algorithms to assist/monitor the elderly, patients, and the disabled population

A review of bioengineering techniques applied to breast tissue: Mechanical properties, tissue engineering and finite element analysis

Female breast cancer was the most prevalent cancer worldwide in 2020, according to the Global Cancer Observatory. As a prophylactic measure or as a treatment, mastectomy and lumpectomy are often performed at women. Following these surgeries, women normally do a breast reconstruction to minimize the impact on their physical appearance and, hence, on their mental health, associated with self-image issues. Nowadays, breast reconstruction is based on autologous tissues or implants, which both have disadvantages, such as volume loss over time or capsular contracture, respectively. Tissue engineering and regenerative medicine can bring better solutions and overcome these current limitations. Even though more knowledge needs to be acquired, the combination of biomaterial scaffolds and autologous cells appears to be a promising approach for breast reconstruction. With the growth and improvement of additive manufacturing, three dimensional (3D) printing has been demonstrating a lot of potential to produce complex scaffolds with high resolution. Natural and synthetic materials have been studied in this context and seeded mainly with adipose derived stem cells (ADSCs) since they have a high capability of differentiation. The scaffold must mimic the environment of the extracellular matrix (ECM) of the native tissue, being a structural support for cells to adhere, proliferate and migrate. Hydrogels (e.g., gelatin, alginate, collagen, and fibrin) have been a biomaterial widely studied for this purpose since their matrix resembles the natural ECM of the native tissues. A powerful tool that can be used in parallel with experimental techniques is finite element (FE) modeling, which can aid the measurement of mechanical properties of either breast tissues or scaffolds. FE models may help in the simulation of the whole breast or scaffold under different conditions, predicting what might happen in real life. Therefore, this review gives an overall summary concerning the human breast, specifically its mechanical properties using experimental and FE analysis, and the tissue engineering approaches to regenerate this particular tissue, along with FE models

Experimental characterisation of breast tissues and its application to a numerical model of a healthy breast

In this work, a great contribution to the knowledge of the biomechanics of the breast has been done. None of the previous works were valid to simulate the real movement of the breast and a little knowledge existed about many factors which play an important role in the behaviour of the breast. We have gone in depth in this field and provided the path that must be followed in the future computational and experimental studies about the breast. Many possibilities have been discarded shedding light on the way the development of the finite element model of the breast should be carried out. Moreover, the difficult interaction between the adipose tissue and the pectoral muscle has been pointed out as key in the process. Concerning the experimental work, a lot of relaxation test have been done in human adipose tissue, in the abdomen and in the breast. Different patients and areas have been tested. Two different viscoelastic models (with several hyperelastic strain energy functions) were adjusted to the experimental tests, providing very good results. For both of them, the independency of their constants with respect to the strain rate was proved, although the independency with respect to the strain level was not accomplished. That means that it is not possible to define a unique set of constants for the adipose tissue with these two models. Probably the tissue is suffering some damage at the different strain levels, making the constants dependent on it. This damage should be studied more carefully and a damage model should be used in case the degradation was confirmed. In spite of this fact, for a certain strain level, both models are valid, being the internal variables viscoelastic model, with an Ogden strain energy function, the formulation that adjusted the experimental results more accurately. Several comparisons have been made to analyse the differences between the mechanical behaviour of the adipose tissue of different areas and individuals. The mechanical behaviour of different individuals' abdominal fat was compared. Inter-individual differences were found in both, the elastic and the viscous constants, confirming that it was a correct decision to extract the specimens from the same individual in the subsequent statistical analyses, for example, to check the validity of the QLV and IVV models or to compare the adipose tissue from different anatomical regions. It is therefore advisable to extract the specimens from the same patient if avoiding the inter-individual effects is desired. In the comparison of the mechanical properties of the adipose tissue of several regions of the abdomen and the breast, differences were found between the superficial breast and three groups of the abdomen: superficial-medial, deep-medial and deep-lateral. However, there are no differences with the superficial-lateral group. No differences were detected between the deep breast and the rest of the groups either. These conclusions have a high relevance for the breast reconstruction surgery with autologous abdominal tissue. The breast adipose tissue can be considered as a unique tissue from the mechanical point of view. Moreover, in the breast reconstruction surgery, the deep breast fat can be replaced by any part of the abdomen, since no significant differences exist in the mechanical properties. However, the superficial breast fat should be replaced, if possible, by the superficial lateral region of the abdomen. Also important although with less clinical relevance are the differences found between regions of the abdominal adipose tissue. It seems that no differences exist in the mechanical properties between both regions of the superficial layer, between both parts of the deep layer and between both parts of the medial regions. However, differences between the deep and superficial layers were found, that is to say, the mechanical properties of the abdominal adipose tissue seem to change with the depth. Comparing the elastic part of the final model presented here for the breast adipose tissue with the Samani's constants (which are the only ones found in the literature for the breast fat), it can be seen that the behaviour modelled with the Samani's constants is much stiffer than that measured experimentally in this thesis. Also supported by the results obtained in the FE models, it seems that the constants provided by Samani do not correspond to the real behaviour of the breast adipose tissue. Regarding the computational work, several models, boundary conditions and strain energy functions for different materials have been tried. The deformed shape of the deformed breast model from supine to prone position has been improved much from the initial models, although some issues need to be solved yet to improve the models and finally obtain a deformation which can be considered valid. It has been found that none of the material models and boundary conditions proposed in the literature produce reasonable results. In particular, they yield an excessively stiff behaviour. The interaction between the muscle and the breast tissue has been detected to play a key role in the deformation of the breast. The properties of the muscle are not determinant, as the muscle is not activated during the change of position modelled here and, moreover, it is stiffer than the rest of the involved tissues. Of course, if an activity in which the dynamics matter, like running, is under study, the role of the muscle can change. The skin properties can be important in the global behaviour because it is the tissue which surrounds the organ. In general, a deeper knowledge about the mechanical properties of the materials is needed. Normally, these properties have been determined in the literature with one “simple" experimental test, whereas the deformation in the breast is not simple whatsoever and quite different from the experimental test which was carried out. This can lead to wrong results when using these mechanical properties in a computational model. In addition, more studies are needed about the internal structure of the tissues and their connections