Collaborative Simulation of Soft-Tissue Deformation for Virtual Surgery Applications

An experimental method is described for estimating the mechanical properties of human soft tissues by calculating Young's modulus which was defined according to the slope of the hysteresis curve of the test subject, reflecting the dependence of its deformation on the force applied. The main causes of numerous difficulties in obtaining such data and the ways for their overcoming are considered. Experiments were made on the biceps in the isometric mode under different degrees of internal tension. It has been shown that the higher the physical development of the test subject the less the magnitude of Young's modulus. The dependence of its magnitude on the degree of muscular tension is sublinear in character in the group with good physical development and superlinear in that with poor physical development.

This paper concentrated on how to apply meshless method to do physical based soft tissue deformation. First we approximated the deformation field using a Moving Least Squares (MLS) approximation method. Then, a compact force computation was applied to accelerate the physical computation speed. Finally we implemented a surface animation method to simulate the deformation of soft tissue under external forces. We made experiments with real properties of human soft tissue and the results showed that our method successfully made physical based deformation of human soft tissue.

Emerging biomedical applications require realistic phantoms for validation and testing of prototype systems. These phantoms require stable and flexible tissue-mimicking materials with realistic dielectric properties in order to properly model human tissues. To create a tissue-mimicking material to fulfill these needs, carbon powder and urethane rubber mixtures were created, and the dielectric properties were measured using a dielectric probe. Both graphite and carbon black were tested. Mixtures of graphite and urethane (0% to 50% by weight) provided relatively low permittivity and conductivity, suitable for mimicking fatty tissues. Mixtures of carbon black and urethane (0% to 15% by weight) provided a broad range of suitable properties. Samples with 15% carbon black had permittivity and conductivity similar to higher-water-content tissues, however the cured samples were not mechanically suitable for moulding into complex shapes. Finally, mixtures of graphite, carbon black, and urethane were created. These exhibited a range of dielectric properties and can be used to mimic a variety of soft tissues. The mechanical properties of these samples were tested and presented properties that exceed typical phantom requirements. This tissue-mimicking material will be useful when creating thin, flexible, and robust structures such as skin layers.

Acoustic properties are the main criteria to evaluate the compatibility of tested materials as a medical phantom. We determined the acoustic properties of konjac glucomannan (KGM) gel to verify its compatibility as a medical phantom. The acoustic properties measurement employed ultrasonic insertion technique and utilized two identical transducers of 5 MHz center frequencies. One KGM gel block with 5.62 mm thickness was used as sample to determine its longitudinal speed, acoustic impedance and attenuation coefficient at three different water temperatures; (21.5 ± 0.1), (22.5 ± 0.1) and (23.5 ± 0.1) °C. Findings indicated that its longitudinal speed and acoustic impedance increased from (1495 ± 1) to (1499 ± 1) m s-1 and (1.555 ± 0.001) to (1.559 ± 0.001) × 106 kg m-2 s-1 as the water temperature increased from (21.5 ± 0.1) to (23.5 ± 0.1) °C. It also indicated that its attenuation coefficient varied around (0.1303 ± 0.0107) to (0.1373 ± 0.0103) dB cm-1 with increasing water temperature. KGM gel is compatible to be a medical phantom since its acoustic properties are comparable to the acoustic properties of human soft tissue.

This paper is concerned with layer-by-layer ultrasound tomographic imaging methods for differential diagnosis of breast cancer. The inverse problem of ultrasound tomography is formulated as a coefficient inverse problem for a hyperbolic differential equation. The scalar mathematical model takes into account wave phenomena, such as diffraction, refraction, multiple scattering, and absorption of ultrasound. The algorithms were tested on real data obtained in experiments on a test bench for ultrasound tomography studies. Low-frequency ultrasound in the 100–500 kHz band was used for sounding. An important result of this study is an experimental confirmation of the adequacy of the underlying mathematical model. The ultrasound tomographic imaging methods developed have a spatial resolution of 2 mm, which is acceptable for medical diagnostics. The experiments were carried out using phantoms with parameters close to the acoustical properties of human soft tissues. The image reconstruction algorithms are designed for graphics processors. Architecture of the GPU cluster for ultrasound tomographic imaging is proposed, which can be employed as a computing device in a tomographic complex.

Characterization of biomechanical properties of soft biological tissues is important to understand the tissue mechanics and explore the biomechanics-related mechanisms of disease, injury, and development. The mechanical testing method is the most straightforward way for tissue characterization and is considered as verification for in vivo measurement. Among the many ex vivo mechanical testing techniques, the indentation test provides a reliable way, especially for samples that are small, hard to fix, and viscoelastic such as brain tissue. Magnetic resonance elastography (MRE) is a clinically used method to measure the biomechanical properties of soft tissues. Based on shear wave propagation in soft tissues recorded using MRE, viscoelastic properties of soft tissues can be estimated in vivo based on wave equation. Here, the viscoelastic properties of gelatin phantoms with two different concentrations were measured by MRE and indentation. The protocols of phantom fabrication, testing, and modulus estimation have been presented.

Mechanical properties of soft human tissues under dynamic loading

Tissue mimicking phantoms play a crucial role in the development of Acoustic Radiation Force Impulse Imaging. This paper deals with the preparation and study of agar based tissue mimicking phantoms. Acoustic and elastic properties are studied for various concentration of agar samples (1.7%-10% by weight). Acoustic properties are measured using pulse echo transmit receive principle. Young's modulus of the samples are measured using compression test. Reproducible phantom preparation procedures are standardised for matching various properties of normal and abnormal human soft tissues.

Mechanical properties of soft human tissue are linked to their pathological state. One way to assess these properties is through the Young modulus measurement, which is related to the shear wave speed in the medium when considering tissues as nearly incompressible. In order to characterize its elastic properties using sonoelastography, we introduce a new technique for shear wave estimation from a static interference pattern based on Shear Wave Holography. A relation between the mathematical representation of the interference pattern and the local shear speed is derived using the Phase Derivative approach. The experimental scheme is presented, detailing the advantages of the new configuration. Homogeneous and heterogeneous elastic media were simulated, generating an interference pattern on them. The shear speed estimation algorithm was explained and applied to obtain the speed map, calculating the mean value over each medium. The technique was tested on a nearly incompressible homogeneous elastic phantom, yielding a maximum and a mean estimation error of 6% and 4.6% respectively. Overall, Shear Wave Holography using normal vibration is feasible and shows promising results in estimating shear wave speed in elastic materials.

Ultrasound properties of human prostate tissue during heating

Real deformation modeling of soft tissue is a major difficulty in the development of virtual surgery. The solution of this difficulty requires in-depth research on the mechanical properties of soft tissue. This paper is devoted to the study of constitutive relations in soft tissue mechanical models: viscoelastic model and hyperelastic model. Through a series of experiments and calculations, the stability and applicability of various hyperelastic models were evaluated. The coefficients and exponents of Prony Series in viscoelastic generalized Maxwell model were calculated and optimized. Finally, tensile simulation was carried out based on the existing constitutive model. The results showed that the large intestine soft tissue data fitted by van der Waals model was stable and accurate; The viscoelasticity of large intestine has little influence on the whole stretching process. The viscoelasticity will replace hyperelasticity and dominate the whole stretching process when the viscosity reaches the current 100 times.

The main driver of industry 4.0 is data and information for realizing resilient manufacturing systems through data-based decision-making. This requires the data flow from different machinery and its processing. Therefore, a methodical survey on the logical and technical requirements for enabling an efficient data flow can be beneficial since it fastens the process of establishing the data flow and gives production and software engineers a common understanding of the data’s meaning. Hence, data, related metadata like the unit or the frequency of recordings, and technical information, e.g., the machine’s interface or the communication protocol, are necessary. Based on the classical value stream mapping (VSM) as a lean management tool, the first approach for a methodical gathering of data, value stream mapping 4.0, was established in 2016. Since VSM 4.0 provides technical properties for specifying the data flow, some shortcomings were identified, particularly related to technical information. This contribution introduces the VSM 4.0 plus that solved the identified shortcomings by adding new properties. Compared to VSM 4.0, VSM 4.0 plus offers detailed specifications of data points, includes technical information, e.g., used communication protocols, adds information regarding data processing, and enhances the storage and usage dimension by providing more details. Through the added properties, VSM 4.0 plus allows domain and software engineers more efficient collaboration since all required information for establishing the data flow and its processing are united in one methodology. To verify the practicability, the VSM 4.0 plus was applied within several manufacturing-related use cases.

Many factors such as the type and the orientation of capsule antenna, the position of the capsule antenna in gastrointestinal tract, the dielectric properties of human body tissues and so on can influence the radiation characteristics of Ingestible Wireless Devices (IWDs). This paper analyses the uncertainty of the radiation characteristics of IWD and how these factors influence the performance of IWD. It is notable that the electric intensity outside human body models where a helix antenna is implanted is larger than that exposed to a dipole antenna. The link performance of helix antenna is influenced by the ground. The dielectric properties of human body tissues and the orientation of IWD also influence the radiation characteristics of IWD. However, among these factors, the position of IWD has the most important influence.

Measuring the compressive viscoelastic mechanical properties of human cervical tissue using indentation

Understanding the failure properties of human aortic tissue at high strain rate loading is important to understand the mechanism of traumatic rupture of aorta (TRA). This study reports 18 uniaxial tensile tests performed on human aortic tissue in the longitudinal direction. Rectangular specimens were obtained from cadaveric human aortic tissue. Uniaxial tensile tests were performed at target strain rates of 0.001 s–1, 65 s–1, 130 s–1and 190 s–1 to failure. High-speed video was used to measure the gripper to gripper displacement. Failure stress and strain were calculated. The load-deformation relationship of aorta is found to be nonlinear and strain rate dependent with higher failure stress and lower effective failure engineering strains at higher strain rates. Across tests, the failure stress ranged from 0.86 MPa to 1.86 MPa and effective failure strain from 13.52% to 10.80%.