A deeper understanding to predict fracture in soft biological tissues is of crucial importance to better guide and improve medical monitoring, planning of surgical interventions and risk assessment ...of diseases such as aortic dissection, aneurysms, atherosclerosis and tears in tendons and ligaments. In our previous contribution (Gültekin et al., 2016) we have addressed the rupture of aortic tissue by applying a holistic geometrical approach to fracture, namely the crack phase-field approach emanating from variational fracture mechanics and gradient damage theories. In the present study, the crack phase-field model is extended to capture anisotropic fracture using an anisotropic volume-specific crack surface function. In addition, the model is equipped with a rate-dependent formulation of the phase-field evolution. The continuum framework captures anisotropy, is thermodynamically consistent and based on finite strains. The resulting Euler–Lagrange equations are solved by an operator-splitting algorithm on the temporal side which is ensued by a Galerkin-type weak formulation on the spatial side. On the constitutive level, an invariant-based anisotropic material model accommodates the nonlinear elastic response of both the ground matrix and the collagenous components. Subsequently, the basis of extant anisotropic failure criteria are presented with an emphasis on energy-based, Tsai–Wu, Hill, and principal stress criteria. The predictions of the various failure criteria on the crack initiation, and the related crack propagation are studied using representative numerical examples, i.e. a homogeneous problem subjected to uniaxial and planar biaxial deformations is established to demonstrate the corresponding failure surfaces whereas uniaxial extension and peel tests of an anisotropic (hypothetical) tissue deal with the crack propagation with reference to the mentioned failure criteria. Results favor the energy-based criterion as a better candidate to reflect a stable and physically meaningful crack growth, particularly in complex three-dimensional geometries with a highly anisotropic texture at finite strains.
Registration of pelvic computed tomography (CT) and magnetic resonance imaging (MRI) is highly desired as it can facilitate effective fusion of two modalities for prostate cancer radiation therapy, ...i.e., using CT for dose planning and MRI for accurate organ delineation. However, due to the large intermodality appearance gaps and the high shape/appearance variations of pelvic organs, the pelvic CT/MRI registration is highly challenging. In this paper, we propose a region-adaptive deformable registration method for multimodal pelvic image registration. Specifically, to handle the large appearance gaps, we first perform both CT-to-MRI and MRI-to-CT image synthesis by multi-target regression forest. Then, to use the complementary anatomical information in the two modalities for steering the registration, we select key points automatically from both modalities and use them together for guiding correspondence detection in the region-adaptive fashion. That is, we mainly use CT to establish correspondences for bone regions, and use MRI to establish correspondences for soft tissue regions. The number of key points is increased gradually during the registration, to hierarchically guide the symmetric estimation of the deformation fields. Experiments for both intra-subject and inter-subject deformable registration show improved performances compared with the state-of-the-art multimodal registration methods, which demonstrate the potentials of our method to be applied for the routine prostate cancer radiation therapy.
The dielectric properties of tissues are the key parameters in electromagnetic medical technologies. Despite the apparent simplicity of the dielectric measurement process, reported data have been ...inconsistent for heterogeneous tissues. Dielectric properties may be attributed to heterogeneous tissues by identifying the tissue types that contributed to the measurement through histological analysis. However, accurate interpretation of the measurements with histological analysis requires first defining an appropriate histology region to examine. Here, we investigate multiple definitions for the probe sensing depth and uniquely calculate this parameter for measurements with a realistic range of tissues. We demonstrate that different sensing depth definitions are not equivalent, and may introduce error in dielectric data. Last, we propose an improved definition, given by the depth to which the probe can detect changes in the tissue sample, within the measurement uncertainty. We equate this sensing depth with histology depth, thus supporting the need of having the tissue region that contributes to the dielectric data be the same as that which is analyzed histologically. This paper demonstrates that, for these tissues, the histology depth is both frequency and tissue dependent. Therefore, the histology depth should be selected based on the measurement scenario; otherwise, inaccuracies in the data may result.
Progress in implantable and ingestible wireless biotelemetry requires versatile and efficient antennas to communicate reliably from a body. We propose an ultraminiature 434 MHz antenna immune to ...impedance detuning caused by varying electromagnetic properties of the surrounding biological environment. It is designed for a standard input impedance of 50 Ω. The antenna is synthesized and miniaturized using a hybrid analytical-numerical approach, and then optimized to conform to the inner surface of a 17 mm long biocompatible encapsulation (7 mm diameter). The substrate is 50 μm thick. The capsule antenna is analyzed both in simplified and anatomically realistic heterogeneous phantoms. It remains matched at common implantation sites and through the whole gastrointestinal tract. Enhanced robustness allows using the antenna for a wide range of in-body applications. Computed reflection coefficients and radiation performance both show good agreement with measurements. The far field is characterized with the direct illumination technique using an analog fiber optic link. The realized gain (measured max. value -19.6 dBi) exceeds the counterparts by about 3 dBi. The proposed antenna contributes to the further development of a new generation of miniature in-body devices that involve complex and dense integration of sensors, logic, and power source.
Soft biological tissues are complex materials with a large structural variety, with differences in behavior, but with some common characteristics. Skin is an archetypal soft tissue which presents ...many common characteristics to other soft biological tissues, like being a multilayer collagen-reinforced structure, with nonlinear behavior, anisotropy, viscosity, preconditioning effects, internal stresses and tissue growth and adaptation. Departing from a detailed description of the structures of the skin and the experimental evidence, we herein analyze the different modeling approaches in the literature for the distinct aspects of the skin behavior, with attention to the implementation in finite element codes.
•A new method using zero-frequency-modulation-based optical data encoding scheme has been proposed to realize accurate optical information transmission through thick tissues at low light ...intensities.•Optical experiments have been conducted to verify the proposed method using different thicknesses of chicken breast tissues and the laser beam with different wavelengths.•The proposed method provides a promising means for accurate optical information transmission through deep biological tissues.
Delivering accurate information through thick biological tissues is critical in many biomedical applications. However, it is challenging to realize accurate optical information transmission and achieve large penetration depth due to complex structures and compositions of thick biological tissues. The absorption and scattering through biotissues are inter-related, and could cause light attenuation dramatically. In this paper, a new method based on zero-frequency modulation (ZFM) is proposed to generate a series of 2D random amplitude-only patterns for accurate optical information transmission through thick tissues at low light intensities. Light source modulated by the generated 2D patterns propagates through biological tissues, and a single-pixel bucket detector is used to record light intensity with a differential detection technique. Different sample thicknesses and the light source with different wavelengths are used to experimentally verify the proposed method. The proposed method can realize accurate optical information transmission through biological tissues with a thickness of 16.0 mm, when a low laser power of only 0.08 mW/cm2 is used to illuminate the sample at wavelength of 658.0 nm. The proposed method realizes accurate optical information transmission through thick biological tissues, and is able to overcome the challenges, e.g., penetration through small-thickness tissues and low quality of the retrieved signals. The proposed method provides a promising means for optical data transmission through deep tissues.
Chronic diseases like diabetes mellitus often require a permanent monitoring of vital signs. Especially the use of telemedicine will increase the quality of life for affected patients. Therefore, ...novel systems are necessary which are able to permanently detect and provide health status information. But these systems must not control patient's life and should work autonomously. For this purpose, intelligent medical implants are well qualified. This work describes a system for wireless power supply and communication with medical implant applications. Monitoring vital signs will create a big amount of data. Therefore, high data rates are necessary provided by high operating frequencies which in turn lead to electromagnetic far-field conditions. In this case, high attenuation losses due to the permittivity of the human body ε r have to be considered. Hence, high frequencies are not suitable for the transfer of energy into the human body. The presented concept is based on two different frequencies for power supply and data transmission. An independent development of both blocks is thereby possible. The power supply operates at a frequency of 13.56 MHz, using inductive coupling. Consequently, the human body does not affect the energy transfer. In contrast, the data transmission is operated at a frequency of the medical implant communication service (MICS) band. The elaborated system consists of a power supply unit, a data transmission unit, and a control unit. The implementation of the power supply and data transmission as well as associated theoretical basics are presented. Performed measurements demonstrate that the realized system is qualified for the use on human beings.
In the above paper <xref ref-type="bibr" rid="ref1">1 , the acknowledgment of grant support is missing. The grant support should be: This work was supported in part by the NIH under Grant EB006733.
New highly-multiplexed imaging technologies have enabled the study of tissues in unprecedented detail. These methods are increasingly being applied to understand how cancer cells and immune response ...change during tumor development, progression, and metastasis, as well as following treatment. Yet, existing analysis approaches focus on investigating small tissue samples on a per-cell basis, not taking into account the spatial proximity of cells, which indicates cell-cell interaction and specific biological processes in the larger cancer microenvironment. We present Visinity, a scalable visual analytics system to analyze cell interaction patterns across cohorts of whole-slide multiplexed tissue images. Our approach is based on a fast regional neighborhood computation, leveraging unsupervised learning to quantify, compare, and group cells by their surrounding cellular neighborhood. These neighborhoods can be visually analyzed in an exploratory and confirmatory workflow. Users can explore spatial patterns present across tissues through a scalable image viewer and coordinated views highlighting the neighborhood composition and spatial arrangements of cells. To verify or refine existing hypotheses, users can query for specific patterns to determine their presence and statistical significance. Findings can be interactively annotated, ranked, and compared in the form of small multiples. In two case studies with biomedical experts, we demonstrate that Visinity can identify common biological processes within a human tonsil and uncover novel white-blood cell networks and immune-tumor interactions.
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