Renal surface reconstruction and segmentation for image-guided surgical navigation of laparoscopic partial nephrectomy.

An unpredictable dynamic surgical environment makes it necessary to measure morphological information of target tissue real-time for laparoscopic image-guided navigation. The stereo vision method for intraoperative tissue 3D reconstruction has the most potential for clinical development benefiting from its high reconstruction accuracy and laparoscopy compatibility. However, existing stereo vision methods have difficulty in achieving high reconstruction accuracy in real time. Also, intraoperative tissue reconstruction results often contain complex background and instrument information that prevents clinical development for image-guided systems. Taking laparoscopic partial nephrectomy (LPN) as the research object, this paper realizes a real-time dense reconstruction and extraction of the kidney tissue surface. The central symmetrical Census based semi-global block stereo matching algorithm is proposed to generate a dense disparity map. A GPU-based pixel-by-pixel connectivity segmentation mechanism is designed to segment the renal tissue area. An in-vitro porcine heart, in-vivo porcine kidney and offline clinical LPN data were performed to evaluate the accuracy and effectiveness of our approach. The algorithm achieved a reconstruction accuracy of ± 2 mm with a real-time update rate of 21 fps for an HD image size of 960 × 540, and 91.0% target tissue segmentation accuracy even with surgical instrument occlusions. Experimental results have demonstrated that the proposed method could accurately reconstruct and extract renal surface in real-time in LPN. The measurement results can be used directly for image-guided systems. Our method provides a new way to measure geometric information of target tissue intraoperatively in laparoscopy surgery. Supplementary Information: The online version contains supplementary material available at 10.1007/s13534-023-00263-1.

Effects of cane use on the kinematic and kinetic of lower-extremity joints in inexperienced users.

The cane is commonly prescribed for the elderly to maintain balance and enhance independent mobility. However, improper use of cane can increase the risk of falling. Understanding the characteristics of cane gait is critical for better establishing proper cane usage norms. The paper aimed to investigate effects of cane use on kinematics and kinetics of lower extremities in the elderly and the young to guide the development of adaptive cane gait. Twenty participants (10 elder and 10 young) were recruited and walked at a self-comfortable speed or with a cane in a two-point gait. The spatiotemporal gait parameters, hip/knee/ankle joint angles and ground reaction force (GRF) were statistically analyzed using MANOVAs to assess the effects of age and cane. Using the cane significantly decreased step length, cadence and speed and increased step time in both age groups. Age and cane had significant effects on ankle plantarflexion angle in initial swing phase (APA-ISw). In cane gait, the peaks of vertical GRF(V-GRF) and anterior-posterior GRF (AP-GRF) in bilateral lower extremities significantly decreased, and the troughs of right V-GRF significantly increased for both groups. These results suggest that using a cane does interfere with the natural gait of the user and insufficient ankle plantarflexion in initial swing phase (ISw) and reduced AP-GRF may be two key risk factors contributing to cane gait instability. Therefore, the users should consider actively increasing ankle plantarflexion in ISw to avoid deteriorating gait performance due to over-reliance on the cane.

Autostereoscopic 3D Augmented Reality Navigation For Laparoscopic Surgery: A Preliminary Assessment.

OBJECTIVE: Since Augmented Reality (AR) and 3D visualization have proven to be of great significance to the safety and effectiveness of surgical outcomes, will autostereoscopic 3D AR without glasses bring new opportunities for surgical navigation of laparoscopic surgery? METHODS: We used the CPD-based deformation registration algorithm and the proposed virtual view generation algorithm, realizing a deformable autostereoscopic 3D AR navigation framework for laparoscopic surgery. The depth perception and user experience of the 3D AR navigation were evaluated compared with the 2D AR display using an in-vitro porcine heart and offline clinical partial nephrectomy laparoscopic images. RESULTS: The autostereoscopic 3D AR allowed participants to have a more consistent spatial perception as well as a shorter measuring time than 2D AR with significant difference of p<0.05. It can also improve relative depth perception for smaller distance separation of objects < = 3.28 mm. However, the autostereoscopic 3D AR perceived a worse experience compared to 2D AR in the user experience. CONCLUSION: Autostereoscopic 3D AR shows a more efficient and robust sense of spatial scale than 2D AR with better potential to shorten the operating time and improve surgical outcomes than 2D AR, but image blur and distortion are issues that must be solved to improve the perception effect. High precise registration and high fluency visualization requirements could make autostereoscopic 3D AR navigation for soft tissue more challenging. SIGNIFICANCE: Our work lays a theoretical foundation for the further development of laparoscopic surgical navigation.

The Effects of Pedestrian Environment on Ambulation with a Walking Frame in Elderly Individuals: A Survey and Experimental Study.

Understanding the effects of sloped roads in the pedestrian environment on the body during ambulation with a walking frame can help design friendlier living environments for elderly individuals. A survey of the characteristics of walking frames used in different pedestrian environments was investigated in five communities, and a controlled study of the effects of a sloped road on a subject with different walking frames was carried out as foundational research in the laboratory. A synchronous acquisition system consisting of a wireless motion capture module and a physiological information recording module was applied to collect data on the motion of the shoulder joint and skin conductance response (SCR) of fingers in one participant. Force data were collected from sensors placed on the four legs of the walking frame. The experimental data obtained during different tasks were quantitatively analyzed. Compared to flat ground, the shoulder joint rotated in the opposite direction in horizontal and internal/external planes when using a wheeled walking frame on an uphill road, and the supportive force decreased on both uphill and downhill roads. The range of motion of the shoulder joint reduced and the direction of the shoulder joint motion changed when using a footed walking frame on both uphill and downhill roads. Additionally, the peak value of the supportive force on the uphill road appeared in the first 50% of the gait cycle, which was earlier than in the other cases. In addition, walking on the uphill road with a walking frame had a maximum SCR value, which means a greater impact of psychological arousal. Biomechanics of the shoulder joint and psychological arousal are closely related to the ease of walking on a sloped road with a walking frame. These findings are beneficial for designing more appropriate environments for elderly individuals who walk with aids.

The high thermal stability of white emitting phosphor Mg2 Y2 Al2 Si2 O12 :Dy3+ ,Eu3+ ,La3+ /Lu3+ for white light emitting diodes.

A series of Mg2 Y2 Al2 Si2 O12 :Dy3+ ,Eu3+ was prepared using a solid-state method, and the phosphor emitted white light by tuning the ratio of Dy3+ /Eu3+ . The effects of La3+ /Lu3+ on the structure and luminescence properties of Mg2 Y2 Al2 Si2 O12 :Dy3+ ,Eu3+ were explored. Under the influence of bond length and twist, the luminescence intensity of the materials increased first and then decreased under excitation with ultraviolet light. The lattice distortion of the trivalent cation La3+ -substituted Mg2 Y2 Al2 Si2 O12 :Dy3+ and Eu3+ phosphors was reduced, the symmetry of polyhedron occupied by the luminescence centre improved, and the thermal stability of the luminescence centre improved to a certain extent. White light emitting diodes (LEDs) were fabricated by combining a 370 nm LED chip and the Mg2 Y2 Al2 Si2 O12 :Dy3+ ,Eu3+ ,La3+ (Mg2 Y2 Al2 Si2 O12 :Dy3+ ,Eu3+ ,Lu3+ ) phosphor. The results showed that Mg2 Y2 Al2 Si2 O12 :Dy3+ ,Eu3+ ,La3+ /Lu3+ may have potential application in the area of white LEDs.

Purinergic Signaling Mediates PTH and Fluid Flow-Induced Osteoblast Proliferation.

Both parathyroid hormone (PTH) and mechanical signals are able to regulate bone growth and regeneration. They also can work synergistically to regulate osteoblast proliferation, but little is known about the mechanisms how PTH and mechanical signals interact with each other during this process. In this study, we investigated responses of MC3T3-E1 osteoblasts to PTH and oscillatory fluid flow. We found that osteoblasts are more sensitive to mechanical signals in the presence of PTH according to ERK1/2 phosphorylation, ATP release, CREB phosphorylation, and cell proliferation. PTH may also reduce the osteoblast refractory period after desensitization due to mechanical signals. We further found that the synergistic responses of osteoblasts to fluid flow or ATP with PTH had similar patterns, suggesting that synergy between fluid flow and PTH may be through the ATP pathway. After we inhibited ATP effects using apyrase in osteoblasts, their synergistic responses to mechanical stimulation and PTH were also inhibited. Additionally, knocking down P2Y2 purinergic receptors can significantly attenuate osteoblast synergistic responses to mechanical stimulation and PTH in terms of ERK1/2 phosphorylation, CREB phosphorylation, and cell proliferation. Thus, our results suggest that PTH enhances mechanosensitivity of osteoblasts via a mechanism involving ATP and P2Y2 purinergic receptors.

Luminescence and energy transfer of warm white-emitting phosphor Mg2Y2Al2Si2O12:Dy3+,Eu3+ for white LEDs.

A series of Mg2Y2Al2Si2O12:Dy3+,Eu3+ phosphors were synthesized by the solid-state method. The luminescent properties and crystal structures of the Mg2Y2Al2Si2O12:Dy3+,Eu3+ phosphors were analyzed. The XRD results show that the synthesized Mg2Y2Al2Si2O12:Dy3+,Eu3+ phosphors are of pure phase. Mg2Y2Al2Si2O12:Dy3+ can emit blue and yellow light under 367 nm light excitation; when doped with Eu3+, there is an obvious energy transfer from Dy3+ to Eu3+, and warm white light can be realized by adjusting the concentrations of Dy3+ and Eu3+ in Mg2Y2Al2Si2O12. A warm white LED device was fabricated by combining Mg2Y1.88Al2Si2O12:0.05Dy3+,0.07Eu3+ and a UV LED chip (370 nm) under a voltage of 3.2 V and current of 5 mA, the characteristics of the white LED being CIE = (0.4071, 0.3944), CCT = 3500 K and CRI = 91.3.

Improvement of thermal stability and photoluminescence in Mg2Y2Al2Si2O12:Ce3+ by the cation substitution of Ca2+, Sr2+ and Ba2+ ions.

The luminescence of Ce3+ in Mg2Y2Al2Si2O12 (MgYAlSiO6) can be controlled by substituting with Ca2+, Sr2+, and Ba2+ ions. The materials show blue shifts in their emission spectra that become highly evident with the increase in the ionic radius, and this phenomenon is the result of the combined action of the nephelauxetic effect and crystal field splitting. Due to the introduction of Ca2+, Sr2+, and Ba2+, the distortion of the crystal decreases and the structural rigidity and stability increase, improving the quantum efficiency and temperature stability of Mg2Y1.93Al2Si2O12:0.07Ce3+. Mg2Y1.93Al2Si2O12:0.07Ce3+,Ca2+ is more stable than Mg2Y1.93Al2Si2O12:0.07Ce3+,Sr2+/Ba2+ because the radius of Sr2+/Ba2+ is larger than that of Mg2+. The Mg1.9Y1.93Al2Si2O12:0.07Ce3+,0.1Ca2+ fluorescent powder and blue chip were packaged to obtain warm white light-emitting diodes (LEDs) with luminous efficiency of 60 lm W-1. These results show that the Mg2Y2Al2Si2O12:Ce3+ phosphor has potential application value in white LEDs.

Investigation of Correction Trajectory Considering Bone End-Plane Orientation and the Shortest Growth Path.

External fixators are widely used in orthopedics for the purposes of fracture reduction and bone deformity correction. Since there is nonlinear mapping between the joint and operation spaces of the external fixator, bone correction trajectories achieved by equally adjusting the length of the struts in the joint space are usually not the trajectories that clinicians expect. Based on two different adjustment strategies, a new strategy considering bone end-plane orientation and the shortest growth path is proposed to plan the position and orientation of the distal bone end, which is named joint adjustment for equal bone distraction. By proposing the inverse and forward kinematic solutions of an Ortho-SUV external fixator, correction trajectories with three different adjustment strategies are generated and compared, and the bone shapes for each strategy are modeled. The results obtained by comparative analysis indicate that a smooth and uniformly spaced linear trajectory can be acquired using the new adjustment strategy, which can avoid bone end interference and maintain an optimal distraction rate of 1.03 mm/day, with only a 3% error compared with 1 mm/day. The new strategy can perform multiplane corrections simultaneously and is beneficial for stimulating the growth of new bone tissue.

Configuration design and correction ability evaluation of a novel external fixator for foot and ankle deformity treated by U osteotomy.

As a basic osteotomy technique, U osteotomy can be applied for certain complex foot and ankle deformities. Gradual correction cases using Ilizarov apparatus and Taylor Spatial Frame have been reported. This paper proposes a novel parallel distraction apparatus for U osteotomy (PDA-Uos) to supplement the correction equipment for surgeon. Designed with an adjustable structure, the PDA-Uos can adopt different assembly shapes (joint connection points). However, the influence of the change in assembly shape on interference-free workspace and self-structural performance of the external fixator have received little attention. To address this issue and enhance the selection of the most suitable assembly shape for patient, an algorithm to obtain the interference-free workspace of different assembly shapes is proposed based on the inverse position solution of the PDA-Uos. Additionally, correction ability indices are defined according to the requirements of accurately controlled motion and high structural stiffness of the external fixator along the correction path. The results of simulation cases indicate that the interference-free workspace and the correction ability vary according to the assembly shape and thus the proposed method can be used to select an assembly shape with sufficient workspace and the best correction ability before performing correction for a given patient. Graphical abstract.

Mechanical properties and antibacterial activities of novel starch-based composite films incorporated with salicylic acid.

To control food contamination and meet the growing demand for high quality food, a novel and excellent starch composite film as packing material with optimized physical, mechanical properties and antimicrobial activity was produced in this paper. Starch-based composite films incorporated with salicylic acid (SA) and waxy maize starch nanoparticles/κ-carrageenan (WMSNs/KC) were used to achieve antimicrobial activity and improve the mechanical properties. WMSNs were fabricated through enzymolysis and recrystallisation method, followed by individually adding KC to form WMSNs/KC by self-assembly, and used as a nanofiller and stabilizer to be incorporated into hydroxypropyl tapioca starch-based films at a concentration of 0-9%. Characterization of macromorphology and scanning electron microscope indicated the starch composite films with WMSNs/KC were smooth, uniform, and transparent. X-ray diffraction pattern and Thermogravimetric analysis also showed strong interactions such as hydrogen bond formation among films, WMSNs/KC and SA. Compared with the pure starch-based films, the composite films reinforced by the addition of WMSNs/KC significantly increased the tensile strength, water vapor barrier and thermal stability, while the transparency and elongation at break decreased slightly. Moreover, the starch composite films showed excellent antimicrobial activity for three typical undesired microorganisms in foods, Escherichia coli, Staphylococcus aureus, and Bacillus subtilis.

Investigation of load transfer process between external fixator and bone model by experimental and finite element methods.

INTRODUCTION:: Unilateral external fixators are widely used in orthopedics to stabilize fractured bones and to treat limb deformities. One of the main problems is that it is difficult to detect healing status. In addition, whether load transfer progress between the fixator and bone model are the same under axial, torsional, and bending loads has not been studied. METHODS:: Therefore the main purpose of this study was to detect the load transfer process between the fixator and a bone model by measuring strains on the fixator-bone system during four healing states using experimental and finite element methods. In the experimental method, 20 strain gauges were used to measure strain on the fixator and bone model under three load conditions. Polyacetal slice models with different material properties were used to simulate the callus model during four growth states. RESULTS:: The results indicate that strain on the bone model increased and strain on the fixator parts decreased with maturation of the callus under axial, bending, and torsional loads. Although all curves showed a similar changing trend, they were slightly different under the three loads. DISCUSSION AND CONCLUSIONS:: This study provides a useful method to monitor the fracture healing process, and identifies the healing endpoint, detects healing status, and provides useful information for the orthopedist.

A finite element analysis for monitoring the healing progression of fixator-bone system under three loading conditions.

BACKGROUND: Unilateral external fixators are widely used in orthopedics to stabilize fractured bones and in the treatment of limb deformities. The main value for evaluation of mechanical stability of the external fixator is fixator stiffness. The fixator stiffness is an important factor as it will influence the biomechanical environment to which fixator and regenerating tissues are exposed. OBJECTIVE: The main objective of this work was to monitor the transmission of stress and the change of displacement generated in fixator-bone system under three loading conditions during healing process. METHODS: In this study, a finite element model with changing Young's modulus of the callus is established, finite element analysis was used to investigating stress and deformation of fixator-bone system caused by axial load, torsional load and bending load during three healing stages. RESULTS: The results reveal that at different healing stages, stress distribution between the fixator and fractured bone is different, the position of displacement is mainly concentrated in the fracture site and proximal bone and with the increase of healing time, the deformation decreased. CONCLUSIONS: This work helps orthopedic doctors to monitor the progression of fracture healing and determine the appropriate time for removal of a fixation device and provide useful information.

Numerical investigation of the relationship between pin deviations and joint coordinates of a unilateral external fixator.

BACKGROUND: Fracture correction is an important orthopedic operation, which can be performed using a unilateral external fixator. Regulating the rotational and translational joints of the fixator is usually necessary to correct complex deformities. However, pin deviations inevitably occur during surgery, and the fixator has its own limitations. Therefore, the relationship between fixator joint adjustment and pin deviations must be identified and discussed. METHODS: The influence of pin deviation on the fixator joint adjustment was analyzed using the inverse kinematics method based on a 6-DOF unilateral external fixator. The effect of multiple pin deviations on fixator joint was also discussed. FINDINGS: This study reveals that the single pin deviations in different axes affect different fixator joints. When multiple deviations occur simultaneously, the regulated quantity is equal to the sum of that of each deviation. INTERPRETATION: Reasonable pin placement can reduce the joint adjustment values and prevent reaching limit values of fixator joint, which aids in expanding the application scope of the fixator. This research can also help reduce the duration of orthopedic surgeries, if the relationship between pin deviation and joint adjustment is known in advance.

A theoretical analysis and finite element simulation of fixator-bone system stiffness on healing progression.

INTRODUCTION: The unilateral external fixator has become a quick and easy application for fracture stabilization of the extremities; the main value for evaluation of mechanical stability of the external fixator is stiffness. The stiffness property of the external fixator affects the local biomechanical environment of fractured bone. METHODS: In this study, a theoretical model with changing Young's modulus of the callus is established by using the Castigliano's theory, investigating compression stiffness, torsional stiffness and bending stiffness of the fixator-bone system during the healing process. The effects of pin deviation angle on three stiffness methods are also investigated. In addition, finite element simulation is discussed regarding the stress distribution between the fixator and bone. RESULTS: The results reveal the three stiffness evaluation methods are similar for the fixator-bone system. Finite element simulation shows that with increased healing time, the transmission of the load between the fixator and bone are different. In addition, the finite element analyses verify the conclusions obtained from the theoretical model. CONCLUSIONS: This work helps orthopedic doctors to monitor the progression of fracture healing and determine the appropriate time for removal of a fixation device and provide important theoretical methodology.

Hierarchical Shared Control of Cane-Type Walking-Aid Robot.

A hierarchical shared-control method of the walking-aid robot for both human motion intention recognition and the obstacle emergency-avoidance method based on artificial potential field (APF) is proposed in this paper. The human motion intention is obtained from the interaction force measurements of the sensory system composed of 4 force-sensing registers (FSR) and a torque sensor. Meanwhile, a laser-range finder (LRF) forward is applied to detect the obstacles and try to guide the operator based on the repulsion force calculated by artificial potential field. An obstacle emergency-avoidance method which comprises different control strategies is also assumed according to the different states of obstacles or emergency cases. To ensure the user's safety, the hierarchical shared-control method combines the intention recognition method with the obstacle emergency-avoidance method based on the distance between the walking-aid robot and the obstacles. At last, experiments validate the effectiveness of the proposed hierarchical shared-control method.

Electromagnetic forward and inverse problems of non-rotating magnetoacoustic tomography with magnetic induction.

The analysis of electromagnetic forward and inverse problems is very important in the process of image reconstruction for magnetoacoustic tomography with magnetic induction (MAT-MI). A new analysis method was introduced in this paper. It breaks through some illogical supposes that the existing methods applied and can improve the spatial resolution of the image availably. Besides it can avoid rotating the static magnetic field which is very difficult to come true in application, therefore the development of MAT-MI technique can be promoted greatly. To test the validity of the new method, two test models were analyzed, and the availability of the method was demonstrated.

[Microwave thermoacoustic signal analysis of biological tissues based on the coupling of multifield].

According to the coupling relationship of electromagnetic field, thermal field and acoustic field during the time that microwave irradiates the biological tissues, we conducted a study on the microwave-induced thermoacoustic tomography forward problem. In the study, we started from the thermoacoustic wave propagation that incorporated the spatial inhomogeneities of thermal and acoustic properties, and we used a method based on the finite element to solve the thermoacoustic equation. As the penetration depth and the specific absorption rate changed with the microwave frequency in biological tissue, the hotspot position and value altered, so the pressure wave propagation and the detecting value would be influenced. By analyzing the simulation results, we found that different detection point has different information content. Because the microwave-induced acoustic waves contain abundant information about the structural, electromagnetic and acoustic properties of phantom, they can reflect information on the tissue composition and structure of the phantom effectively.

[Experiment and analyse on the effect of magnetic nanoparticles upon relaxation time of proton in molecular recognition by MRI].

To research on the effect of three different magnetic nanoparticles upon relaxation time of proton. The detection by magnetic resonance imaging (MRI) indicates that there is the effect of marked difference to right control experiment and to analyze the difference from theory. The result discloses that will be able to perform the experiment of molecular recognition using magnetic nanoparticles later.

Energy Transform and Initial Acoustic Pressure Distribution in Microwave-induced Thermoacoustic Tomography.

A study of Microwave-induced Thermoacoustic Tomography is presented in this paper. Microwaves illuminate biological tissues to generate acoustic waves by thermoelastic expansion when electromagnetic energy was absorbed by human tissues. The generated acoustic waves carry information about different electromagnetic properties of different tissues which will be collected and processed to reconstruct human cross section image. In this paper, digital electromagnetic human body model with 1cm resolution was founded according to algorithm requirements. Firstly we analyzed the transform and interrelation among electromagnetic energy, heat energy and acoustic energy. On the basis of established human model: (1) we calculated initial acoustic pressure distribution in cross section image under plane microwave radiation with different frequency. It shows that microwave absorption properties and initial acoustic pressure were different with the change of frequency; (2) using single pulse to illuminate human model, initial acoustic pressure maps of thorax cross section at different time steps were analyzed. These results provided a research basis for further study and calculation of acoustic pressure in microwave-induced thermoacoustic tomography.