Search

Zhijie Li,1,2,* Mengnan Li,1,* Xiaowei Yao,3 Bo Liu,1 Sikai Liu,1 Zeming Liu,1 Binquan Zhang,1 Yongtai Han1 1Department of Osteonecrosis and Hip Surgery, Hebei Medical University Third Affiliated Hospital, Shijiazhuang, People’s Republic of China; 2Orthopedics Department, Affiliated Hospital of Hebei Engineering University, Handan, People’s Republic of China; 3Orthopedics Department, Hebei Provincial Chest Hospital, Shijiazhuang, People’s Republic of China*These authors contributed equally to this workCorrespondence: Yongtai Han, Email yongtaihan@foxmail.comBackground: Whether hip revision with a metaphyseal-fixation femoral stem component can restore the bone mass of the proximal femur remains unclear. The aims of this study were to identify whether the bone mineral density (BMD) of the proximal femur increases following hip revision with a metaphyseal-fixation femoral stem and to identify the factors associated with BMD recovery.Methods: This was a retrospective study involving 36 patients who underwent hip arthroplasty with a metaphyseal-diaphyseal fixation stem (standard length stem) and had indications for hip revision, which was performed with a proximal press-fit short-stem prosthesis for each patient. Dual-energy X-ray absorptiometry (DEXA) was used to obtain, evaluate, and compare the BMD at baseline and one year and two years postoperatively. The proximal femur was divided into several independent areas according to the Gruen zone (Gruen 1 to Gruen 7 from the greater trochanter counterclockwise to the lesser trochanter). Logistic regression analyses were used to assess potential factors significantly associated with an increase in BMD.Results: An increased BMD was obviously identified in the proximal femur. Two years after the surgery, the BMD of the Gruen 1, Gruen 2, Gruen 6, and Gruen 7 areas had increased by 22.6%, 12.6%, 16.2% and 24.2%, respectively, relative to baseline. Three independent risk factors associated with bone mineral density recovery were identified: age (OR=1.100, 95% CI=1.005– 1.203, P=0.038), osteoporosis (OR=14.921, 95% CI=1.223– 182.101, P=0.034) and fair to poor hip function (OR=13.142, 95% CI=1.024– 168.582, P=0.048).Conclusion: This study confirms that metaphyseal-fixation stem hip revision can indeed help restore bone mass in the proximal femur, especially in the Gruen 1, Gruen 2, Gruen 6 and Gruen 7 zones. It was also found that advanced age, osteoporosis, and fair to poor hip joint function were three important risk factors affecting the recovery of proximal femur bone mass after surgery.Trial Registration: Retrospectively registered.Keywords: uncemented fixation, hip revision, bone mineral density, metaphyseal-fixation femoral stem component

The single event effect caused by space heavy ion radiation is one of the important factors affecting the safety and operation of spacecraft on orbit. In the research and evaluation of the frequency, spatial distribution and time characteristics of single event effects, linear energy transfer (LET) spectra of space radiation play an important role. On the Beidou navigation M15 and M16 satellites, a single event upset (SEU) and LET monitor was developed to obtain the upsets of the memory device and the LET spectra of space radiation which passes through the device. Through the measurement results from this monitor, the correlation between the device’s SEUs and the LET spectra could be studied.

The orbit of BeiDou satellite system is a very ideal space environment monitoring area. The radiation dosimeters are present on this series of navigation satellites, and they are respectively installed in the x, y and z positions. A charge detector installed in the satellite cabin is used for monitoring satellite deep charging potential. Radiation dosimeters select the 100 nm P-channel metal oxide semiconductor (PMOS) sensors, whose monitoring range can reach 2 × 106 rad (Si). In the circuit design part, the “zero temperature coefficient” current of the PMOS is used as the constant current source for measuring, which effectively reduces the influence of temperature effect. Three radiation dosimeters realize the daily dose change monitoring during the satellite’s operation, and the detection accuracy is high. The deep charging potential sensor adopts the equivalent capacitor design which is composed of the outer optical quartz glass and the inner circular gold-plate. The two kinds of detection instruments have the characteristics of small volume, low power consumption and high detection accuracy. The detection results show that they have important application value for space environment prediction and guarantee.

The diagnostic value of next-generation sequencing (NGS) of blood samples from patients with periprosthetic joint infection (PJI) after total hip arthroplasty (THA) was evaluated by comparing it with drainage fluid NGS and bacterial culture. The study was designed as a retrospective diagnostic test. Thirty-six infected patients were diagnosed with PJI according to the Musculoskeletal Infection Society (MSIS) criteria and 57 volunteers were included in our study. NGS and bacterial culture were chosen to detect PJI after THA. Blood samples and drainage fluid were collected for NGS, and the drainage fluid, which was collected at the same time as the NGS drainage fluid sample, was used for bacterial culture. The primary outcomes of interest were sensitivity, specificity, and accuracy. In the infection group, 31 patients showed positive results by blood sample NGS, 33 patients showed positive results by drainage fluid NGS, and 17 patients showed positive bacterial culture results. In the control group, the results of 2 blood sample NGS, 16 drainage fluid NGS, and 3 bacterial cultures were positive. The sensitivity, specificity, and accuracy of the blood sample were 0.86, 0.96, and 0.92, respectively. The sensitivity, specificity, and accuracy of the drainage fluid samples were 0.92, 0.72, and 0.80, respectively. The sensitivity, specificity, and accuracy of bacterial culture were 0.47, 0.95, and 0.79, respectively. The study demonstrated that both the sensitivity and specificity of NGS were higher than those of bacterial culture, regardless of the kind of sample. Compared with drainage fluid NGS, the sensitivity of blood sample NGS was slightly lower (0.86 vs 0.92), but blood sample NGS showed higher specificity (0.96 vs 0.72). In total, the diagnostic value of blood sample NGS was superior to that of drainage fluid NGS and bacterial culture. The majority of infected patients could be identified by blood sample NGS. Moreover, because of its high specificity, blood sample NGS can not only detect infectious bacteria but also distinguish infectious from non-infectious bacteria, which is dramatically different from using drainage fluid NGS.

Semi-structured orchard environment has the characteristics of high complexity and strong uncertainty, which brings many challenges to the localization and navigation of agricultural automation equipment with limited sensors. This paper introduces a tree trunk localization system in a semi-structured orchard using camera/ultrasonic sensors fusion. In our method, the location of each tree trunk, which is relative to the robot, is obtained through the trunk tracking camera/ultrasonic detection system on the robot. And the location and direction of the robot are obtained through wheel odometer and IMU, respectively, rather than the traditional high-precision RTK-GPS. In order to reduce the error caused by odometer and IMU, several control points are introduced to revise the tree trunks’ location, of which positions are determinate. Experiments suggest that in a simulated environment and a real orchard, which both have a row-column spacing of $4.3m\times 3.4m$, the tree trunk localization error of our approach is within 0.3m.

In a semi-structured orange orchard, multi-tree trunk detection is an effective method for mobile robot localization. However, because of the complex background of the natural orchard environment, dwarf orange tree trunks are easy to misrecognize. In this paper, we present a novel tree trunk detection method based on multiple cameras and ultrasonic sensors integration technology. These devices are integrated into a single organic mechanical structure that can rotate to detect the surrounding orchard environment such that they can reduce the non-detection zone. Multi-feature fusion will be used in this study. First, histograms of oriented gradient (HOG) and support vector machine (SVM) are used to train an initial tree trunk classifier. Next, the gray scale histogram features of the tree trunk and non-trunk images are extracted to optimize the classifier. Finally, the Roberts cross edge detector is used to extract the trunk’s gradient histogram features, which will improve the recognition accuracy of the classifier. The orange tree trunk recognition experiments exhibited a recall rate and accuracy of 92.14% and 95.49%, respectively. On this basis, ultrasonic sensors are used to get the location data of the trunks and a moving average filter is used to reduce the error of mobile robot localization. The experiment showed that the average localization error was approximately 62 mm (2.5%), and the robot moved stably and precisely along the road of the semi-structured orange orchard.

With the emerging of wearable robots, the safety and effectiveness of human-robot physical interaction have attracted extensive attention. Recent studies suggest that online measurement of the interaction force between the robot and the human body is essential to the aspects above in wearable exoskeletons. However, a large proportion of existing wearable exoskeletons monitor and sense the delivered force and torque through an indirect-measure method, in which the torque is estimated by the motor current. Direct force/torque measuring through low-cost and compact wearable sensors remains an open problem. This paper presents a compact soft sensor system for wearable gait assistance exoskeletons. The contact force is converted into a voltage signal by measuring the air pressure within a soft pneumatic chamber. The developed soft force sensor system was implemented on a robotic hip exoskeleton, and the real-time interaction force between the human thigh and the exoskeleton was measured through two differential soft chambers. The delivered torque of the hip exoskeleton was calculated based on a characterization model. Experimental results suggested that the sensor system achieved direct force measurement with an error of 10.3 ± 6.58%, and torque monitoring for a hip exoskeleton which provided an understanding for the importance of direct force/torque measurement for assistive performance. Compared with traditional rigid force sensors, the proposed system has several merits, as it is compact, low-cost, and has good adaptability to the human body due to the soft structure.

Phase-variable-based approaches are emerging in the control of lower-limb wearable robots, such as exoskeletons and prosthetic legs. However, real-time smooth estimation of the gait phase within each gait cycle remains an open problem. This paper presents a novel method for real-time continuous gait phase estimation during walking. The proposed framework consists of three subsystems: real-time kinematic data collection, gait phase variable estimation, and online adaptation of individual kinematics through backward data segmentation of completed gait strides. It is worth noting that we introduce an online learning mechanism for extracting and learning gait features from previous strides, in contrast with offline parameter tuning. The proposed basic gait model is initialized by human average data and is incrementally refined as a function of the individual gait features over different walking speeds. This provides a framework for long-term personalized control. Furthermore, the phase variable is constructed through the thigh angle measured by an inertial measurement unit. The resulting simple sensor system improves the usability of the proposed technique in wearable robotics. Validation experiments with seven healthy subjects, including treadmill walking and free level-ground walking, were conducted to evaluate the performance of the proposed method. In treadmill validation, the root-mean-square error (RMSE) of the phase estimator was 4.14 ± 1.68% for steady speeds, while it was 6.77 ± 2.29% for unsteady-speed walking. In level-ground validation, the average RMSE of the phase estimator was 4.59 ± 1.76%. Preliminary experiments were also conducted using a single-joint hip exoskeleton to demonstrate the usability of our method in lower-limb wearable robots.

Computational phantoms representing workers and patients are essential in estimating organ doses from various occupational radiation exposures and medical procedures. Nearly all existing phantoms, however, were purposely designed to match internal and external anatomical features of the Reference Man as defined by the International Commission on Radiological Protection (ICRP). To reduce uncertainty in dose calculations caused by anatomical variations, a new generation of phantoms of varying organ and body sizes is needed. This paper presents detailed anatomical data in tables and graphs that are used to design such size-adjustable phantoms representing a range of adult individuals in terms of the body height, body weight and internal organ volume/mass. Two different sets of information are used to derive the phantom sets: (1) individual internal organ size and volume/mass distribution data derived from the recommendations of the ICRP in Publications 23 and 89 and (2) whole-body height and weight percentile data from the National Health and Nutrition Examination Survey (NHANES 1999-2002). The NHANES height and weight data for 19 year old males and females are used to estimate the distributions of individuals' size, which is unknown, that corresponds to the ICRP organ and tissue distributions. This paper then demonstrates the usage of these anthropometric data in the development of deformable anatomical phantoms. A pair of phantoms--modeled entirely in mesh surfaces--of the adult male and female, RPI-adult male (AM) and RPI-adult female (AF) are used as the base for size-adjustable phantoms. To create percentile-specific phantoms from these two base phantoms, organ surface boundaries are carefully altered according to the tabulated anthropometric data. Software algorithms are developed to automatically match the organ volumes and masses with desired values. Finally, these mesh-based, percentile-specific phantoms are converted into voxel-based phantoms for Monte Carlo radiation transport simulations. This paper also compares absorbed organ doses for the RPI-AM-5th-height and -weight percentile phantom (165 cm in height and 56 kg in weight) and the RPI-AM-95th-height and -weight percentile phantom (188 cm in height and 110 kg in weight) with those for the RPI-AM-50th-height and -weight percentile phantom (176 cm in height and 73 kg in weight) from exposures to 0.5 MeV external photon beams. The results suggest a general finding that the phantoms representing a slimmer and shorter individual male received higher absorbed organ doses because of lesser degree of photon attenuation due to smaller amount of body fat. In particular, doses to the prostate and adrenal in the RPI-AM-5th-height and -weight percentile phantom is about 10% greater than those in the RPI-AM-50th-height and -weight percentile phantom approximating the ICRP Reference Man. On the other hand, the doses to the prostate and adrenal in the RPI-AM-95th-height and -weight percentile phantom are approximately 20% greater than those in the RPI-AM-50th-height and -weight percentile phantom. Although this study only considered the photon radiation of limited energies and irradiation geometries, the potential to improve the organ dose accuracy using the deformable phantom technology is clearly demonstrated.

A site-specific skeleton voxel model for a Chinese adult male was constructed in this paper upon a previous Chinese individual voxel model. The whole skeleton was divided into 19 site-specific bones and bone groups; the mass of various skeleton tissues at each bone site, e.g. red bone marrow, was specified according to Asian reference data and the distribution data from ICRP Publication 70. The resultant voxel model (called CAM) has a resolution of 1.741 mm x 1.741 mm in plane, and the total bone mass is 8397.8 g which is almost equal to the Asian reference value. Dose coefficients for the red bone marrow and bone surface in CAM were calculated, and then compared with those from Rex, CMP and ICRP 74. It shows that the dose to RBM in Rex is generally 12% lower than that to CAM in low-energy range (30-150 keV) for AP, LAT, ROT and ISO geometries. It is also found that the RBM dose from mathematical models, i.e. CMP and ICRP 74, is underestimated by -30% in AP geometry and overestimated by 30% in PA geometry for low-energy photons. Meanwhile, the bone surface dose in the low-energy range is overestimated by 150% and 75% in CMP and ICRP 74, respectively, if compared with that from CAM.

The key techniques of visual monitoring contain searching and measuring multiple targets in large region. However, many intelligent monitoring systems today cannot satisfy these requirements simultaneously. By analyzing the features of creatural vision in predator-prey relation, the relationships among visual characteristic parameters were obtained. On this basis, a multi-target visual monitoring system with avian bifoveate feature was designed with the idea and technology of bionics in this paper. This system is characterized by wide vision field in prey and developed binocular vision in predators, and also expands animal visual performance. It has the ability to synchronously achieve the goals of rapidly searching and precisely positioning multiple objects in all directions. This research also provides new insight into bionics design of visual monitoring systems.

A high-resolution whole-body voxel model called CAM representing the Chinese adult male was constructed in this paper based on a previous individual voxel model. There are more than 80 tissues and organs in CAM, including almost all organs required in the ICRP new recommendation. The mass of individual organs has been adjusted to the Chinese reference data. Special considerations were given to representing the gross spatial distribution of various bone constituents as realistically as possible during the construction of the site-specific skeleton. Organ dose conversion coefficients were calculated for six idealized external photon exposures from 10 keV to 10 MeV by using Monte Carlo simulation. The resulting dose coefficients were then compared with those from other models, e.g. CMP, ICRP 74, Rex, HDRK-man and VIP-man. Old and new effective male doses of CAM were calculated by using the tissue weighting factors from ICRP 60 and 103 Publications, respectively. Dosimetric differences between mathematical and voxel models, and the differences between Asian and Caucasian models are also discussed in this paper.

A voxel phantom of Chinese adult male called CNMAN was constructed from color photographs of the first Chinese visible human data set, for radiation protection purpose. This data set was obtained from a 35-y-old Chinese male cadaver by a medical university in China. The man, 170 cm in height and 65 kg in weight, was dead without any pathological changes. The image size for transversal anatomical photographs of the whole body was 3072 x 2048. After the photographs were semi-automatically segmented, the voxel phantom (CNMAN) with a voxel size of 0.16 mm x 0.16 mm x 1 mm, consisting of 29 tissues or organs was constructed. Combined with the MCNP Monte Carlo transport code, preliminary results for radiation protection dosimetry were obtained based on this Chinese voxel phantom.