Deformation Angle Research Articles

An anti‐vibration‐shock inertial matching measurement method for hull deformation

In order to establish a unified spatial reference for the whole ship, inertial matching measurement of hull deformation is widely used because of its continuity and concealment. However, the vibration-shock signal of shipborne equipment often brings short-time output disturbance to the user-side fibre gyroscope unit (FGU), and the disturbance will bring great challenges to the accuracy and convergence of inertial matching measurement. To solve these problems, the authors put forward a new algorithm named as attitude quaternion matching method-improved double factor adaptive Kalman filter-parameter adaptive Kalman filter (AQM-IDFAKF-PAKF). (1) The AQM established the FGU attitude as observation to build the basic model for hull deformation inertial matching method. (2) The authors introduced IDFAKF to track the trend of dynamic hull deformation in vibration interference by using historical data. (3) After judging the anti-vibration-shock calculation stop node, PAKF was utilised to adaptively adjust the parameters of hull deformation matching after vibration-shock, so as to quickly calculate the static hull deformation angle after shock interference. Numerical simulation results illustrated that the AQM-IDFAKF-PAKF can quickly converge the calculation of hull deformation angle with a small steady-state error under the condition of vibration-shock signal interference.

Effect of Wall Shear Stress Gradient on Cells: Distribution of Deformation and Rotation

The effect of wall shear stress gradient on the deformation and rotation of each cell was investigated <em>in vitro</em>. To make a Couette-type of shear flow, the culture medium fluid was sandwiched with a constant gap between parallel walls: a lower stationary culture disk, and an upper rotating disk. Mouse fat precursor cells (3T3-L1) were used in this experiment. After cultivation without flow for 24 hours for adhesion of cells on the lower plate, a shear stress of less than 2 Pa was continuously applied to cells for 24 hours in the incubator. The behavior (deformation and major axis angle) of each single cell was tracked using time-lapse images observed by an inverted phase contrast microscope placed in the incubator. For wall shear stresses of less than 1.9 Pa, each cell exhibited active behavior: migration, deformation, and rotation. Whereas, the cells transformed into spheres when wall shear stress was higher than 1.9 Pa. In addition, the cells were observed to tilt against for a wall shear stress gradient approaching 50 Pa/m.

Spinopelvic Balance Restoration Using Posterior Vertebral Column Resection in Fixed Lumbosacral Deformity Following Pyogenic Spondylodiscitis

Background Data: Several articles reported on PVCR for correction of thoracolumbar deformities that followed tuberculous spondylodiscitis. But fewer focused on fixed lumbosacral deformity secondary to L5 pathology. Study Design: A retrospective cohort study. Purpose: This article aims to determine the degree of spinopelvic parameters correction after posterior vertebral column resection (PVCR) of the fifth lumbar vertebra (L5) in lumbosacral deformities secondary to pyogenic spondylodiscitis and define its relation to patients` clinical and functional outcomes. Patients and Methods: This retrospective study included 12 patients with kyphotic lumbopelvic spinal deformity secondary to healed pyogenic spondylodiscitis at the lumbosacral junction. The study included seven males (58.3%) and five females (41.7%) with a mean age of 37.5 ± 7.61 years. Patients were treated with posterior vertebral column resection (PVCR). Plain radiography, computed tomography (CT), and Magnetic Resonance Imaging (MRI) were performed on all patients, and the following parameters were measured using the Surgimap (version: 2.2.13) computer program: lumbar lordosis (LL), pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), and focal deformity angle. Bony fusion is assessed using postoperative X-rays and/or CT. Visual Analogue Scale (VAS) for both leg and back pain and the Oswestry Disability Index (ODI) were assessed preoperatively and at the last follow-up. Results: The follow-up period lasted for 16 months (12–18). The solid union was achieved in all patients in 8.17 ± 1.52 months with no major postoperative complications. The mean kyphotic deformity was significantly corrected to -5.69° ± 6.77 (p

Аналіз ефективності використання системи гало-гравітаційної тракції як фактора, що впливає на крововтрату при хірургічній корекції складних сколіотичних деформацій у дітей

Halo-gravity traction (HGT) systems are widely used in leading clinics around the world as a staged method for correcting complex (>100°) scoliotic deformities of the spine in children. Today there is no single approach to the use of this technique, and each doctor makes a decision regarding the treatment regimen empirically, based on his clinical experience. Purpose - to identify the factors that affect the amount of blood loss during surgical correction of scoliotic deformity in children. Materials and methods. 76 patients aged 7 to 17 years were examined, on average 11.0±2.8 years. I (experimental) group - 38 children were treated with HGT using the developed tactics of staged surgical treatment; II (control) group - 38 children who underwent one-step surgical correction. The age of children in the groups in group I was 11.0±2.8 years, in group II - 11.2±2.8 years, the age of children in groups was statistically the same (t=-0.409; p=0.684). There were 28 (36.8%) boys and 48 (63.2%) girls. The distribution of children by age and sex in the groups was the same. Data on operative blood loss were statistically processed. Results. According to the statistical study, it can be argued that the blood loss during surgical correction of scoliotic deformity is most affected by the angle of deformation and age of the patient. At an angle of deformation of >100° blood loss is significantly greater than at an angle of <100°, children over 14 years also observed a significant increase in blood loss, and this is associated not only with greater body weight but also with the fact that these children the greater the angle of deformation of the spine, as well as the use of HGT, the angle of deformation decreases less than in younger children. Conclusions. It was determined that after HGT in children the angle of deformation decreased statistically significantly (p<0.001) by an average of 36.5±14.9°. The change in deformation in boys and girls was the same. With surgical correction of scoliotic deformity <100° blood loss (1025.0±235.9 ml), (statistically significant) (p<0.001) is statistically significantly less than blood loss with correction of deformity greater than 100° (1297.5±327.8 ml). With age, blood loss increases in children, and this difference between age subgroups is statistically significant (α=0.05). The value of the angle of scoliotic deformity after surgical correction has a statistically significant (r=0.576; p=0.001) effect on blood loss, the value of surgical correction of deformity on blood loss (r=0.015; p=0.879) does not affect. The research was carried out in accordance with the principles of the Helsinki declaration. The study protocol was approved by the Local ethics committee of all participating institutions. The informed consent of the patient was obtained for conducting the studies. No conflict of interest was declared by the authors. Key words: intraoperative bleeding, spinal deformity, halo-gravity traction.

Bionic Soft Multimodal Actuators for Fast, Large Deformation under Ultralow Magnetic Conditions

AbstractVery recently, magnetically driven soft actuators have prompted increasing interest due to their programmable deformation, swift response, and remote actuation. However, it is still challenging to trigger strong and fast actuating performances with an extremely weak magnetic field due to the difficult task of in situ programming of magnetic domains and the limited mechanical structures. Here, first a bionic sandwich structure is proposed for designing soft magnetic actuators with a specific threshold value. The crab‐like jointed structure of PDMS‐embedded NdFeB upper/lower layers is essential for generating the desirable threshold effect, while a flytrap‐inspired soft interlayer is further implemented to decrease the driving magnetic field. Theoretical analysis and numerical simulations are implemented to optimize the actuating performances of soft actuators (deformation rate, deformation angle) by modulating the structural parameters. Experimental results show that the biomimetic features yield a promptly switchable bistable state, a superior strong deformation rate of 1.93, and a maximum deformation angle of 25.5° under an ultralow magnetic field of 1 mT. Two demonstrative applications of soft actuators are investigated, including threshold switching and soft grippers, suggesting their broad applications in engineering fields. Remarkably, the magnetic soft grippers associated with the gecko‐inspired adhesion surface exhibit an improved and stable grasping ability. This work focuses on designing highly deformable actuators and functions in emerging areas of soft robotics.

Numerical Study of Wave Effect on Aircraft Water-Landing Performance

Aircraft, such as amphibious planes, airliners, helicopters and re-entry capsules, are frequently subject to impacting loads from water-landing/ditching on various free surfaces, especially under wave conditions. Understanding and quantifying the water-landing/ditching performance on wave surfaces are of fundamental important for the design and certification of crashworthiness in the field of aerospace engineering. This study aims to numerically assess the effect of wave surface on water-landing process of an amphibious aircraft. The numerical implementation is realized in Reynolds-averaged Navier–Stokes (RANS) framework by combining finite volume method (FVM), volume of fluid (VOF) approach and velocity-inlet wavemaker. The temporal-spatial characteristic of numerical wave and the accuracy of presented model are, respectively, validated by analytical wave and convergence studies. The aircraft landing simulations with different free surface conditions, i.e., calm water, regular wave with different wave heights are then performed and quantitatively compared through several physical parameters, including acceleration, velocity, pressure, pitch angle and free surface deformation. It was found that the aircraft regular wave-landing process experiences several unique stages comparing with the calm-water-landing case. The results clearly confirm that wave surface can influence the aircraft landing performance to a great extent. The fundamental mechanism is found to be that the wave surface slope and wave particle velocity remarkably change the impacting position and effective impacting velocity of the aircraft.

A Validated Score for Evaluating Spinal Instability to Assess Surgical Candidacy in Active Spinal Tuberculosis-An Evidence Based Approach and Multinational Expert Consensus Study.

Modified Delphi Consensus and Observational Study. Instability in spinal tuberculosis (STB) leads to disabling spinal deformity and neurodeficit. Identifying and estimating instability remains subjective, mainly based on experience. This study aims to develop an objective scoring system to determine instability in STB. The study included 4 phases. (1) A panel of 10 experienced spine surgeons developed a questionnaire based on literature. (2) 68 spine surgeons from 12 countries opined on the importance of each factor in a survey. Five factors deemed important by >70% of participants were further analyzed (3) 60 representative cases of STB were analyzed for instability. A preliminary scoring system was developed, a threshold score for determining instability was derived, and (4) Results were validated. All the 5 factors ("Spine at risk" signs, severity of vertebral body loss, Cervicothoracic/Thoracolumbar junction involvement, age ≤15, and kyphotic deformity ≥30°) considered important by >70% of participants were associated with instability and included in scoring: age ≤15years (P-value, 0.05), cervicothoracic/thoracolumbar junction involvement (P-value, 0.028), sagittal deformity angle ratio (DAR) ≥ 15° (P-value, <.001), vertebral body loss-segmental ratio ≥.5 (P-value, <.001), and presence of spine at risk signs (P-value, <.001). A total score of ≥3/09 indicated definite instability with good sensitivity (77%) and excellent specificity (100%). Repeatability assessment showed a good agreement (.9625), and Cohen's kappa coefficient was strong (.809). A simple objective scoring system for predicting instability in STB has been developed using 5 main factors; young age, junctional involvement, severity of the deformity, vertebral body loss, and presence of spine at risk signs.

Marker- three dimensional measurement versus traditional radiographic measurement in the treatment of tibial fracture using Taylor spatial frame

BackgroundThe Taylor Spatial Frame (TSF) has been widely used for tibial fracture. However, traditional radiographic measurement method is complicated and the reduction accuracy is affected by various factors. The purpose of this study was to propose a new marker- three dimensional (3D) measurement method and determine the differences of reduction outcomes, if any, between marker-3D measurement method and traditional radiographic measurement in the TSF treatment.MethodsForty-one patients with tibial fracture treated by TSF in our institution were retrospectively analyzed from January 2016 to June 2019, including 21 patients in the marker-3D measurement group (experimental group) and 20 patients in the traditional radiographic measurement group (control group). In the experimental group, 3D reconstruction with 6 markers installed on the TSF was performed to determine the electronic prescription. In the control group, the anteroposterior (AP) and lateral radiographs were performed for the traditional parameter measurements. The effectiveness was evaluated by the residual displacement deformity (RDD) and residual angle deformity (RAD) in the coronal and sagittal plane, according to the AP and lateral X-rays after reduction.ResultsAll patients achieved functional reduction. The residual RDD in AP view was 0.5 (0, 1.72) mm in experimental group and 1.74 (0.43, 3.67) mm in control group. The residual RAD in AP view was 0 (0, 1.25) ° in experimental group and 1.25 (0.62, 1.95) °in control group. As for the lateral view, the RDD was 0 (0, 1.22) mm in experimental group and 2.02 (0, 3.74) mm in control group, the RAD was 0 (0, 0) ° in experimental group and 1.42 (0, 1.93) ° in control group. Significant differences in all above comparisons were observed between the two groups (AP view RDD: P = 0.024, RAD: P = 0.020; Lateral view RDD: P = 0.016, RAD: P = 0.004).ConclusionsThe present study introduced a marker-3D measurement method to complement the current TSF treatment. This method avoids the manual measurement error and improves the accuracy of fracture reduction, providing potential advantages of bone healing and function rehabilitation.

Factors Affecting Rebound Phenomenon After Temporary Hemiepiphysiodesis and Implant Removal for Idiopathic Genu Valgum in Adolescent Patients.

The aim of this study was to investigate factors determining postoperative courses, especially focusing on the rebound phenomenon, in adolescent patients with idiopathic genu valgum who underwent temporary hemiepiphysiodesis and implant removal. We identified and reviewed patients with idiopathic genu valgum treated with temporary hemiepiphysiodesis [using tension-band plates (plate group, PG) or transphyseal screws (screw group, SG)] and followed-up to skeletal maturity. In our cohort [68 patients and their 68 limbs (randomly selected in bilateral cases)], the mean hip-knee-ankle alignment was -5.4±1.8 degrees at the time of temporary hemiepiphysiodesis (negative means valgus), 2.6±2.1 degrees at the time of implant removal, and 0.7±2.6 degrees at the last follow-up, respectively. Regarding the implants, the correction speed was not significantly different (P=0.192-0.315) between the PG (total 1.29±0.37 degrees/mo, 0.71±0.23 degrees/mo at distal femur, 0.59±0.16 degrees/mo at proximal tibia, n=19) and the SG (total 1.22±0.49 degrees/mo, 0.65±0.25 degrees/mo at distal femur, 0.57±0.23 degrees/mo at proximal tibia, n=49). The magnitude of rebound phenomenon in the PG (4.1±1.9 degrees) was greater (P<0.001) than that in the SG (1.1±3.1 degrees). The use of plates and faster correction speed, rather than more severe preoperative deformity or greater correction angle, were positively associated with the rebound phenomenon in regression analyses. Among the 68 knees, 1 showed valgus alignment ≥5 degrees and 5 showed varus alignment ≥5 degrees at the last follow-up. All the 6 cases were observed in the SG. Surgical wound dehiscence was observed in 1 patient in the PG. The use of plates and faster correction speed were positively associated with the rebound phenomenon. Careful attention will be needed with the corresponding conditions for optimal results. Progressive genu varum after transphyseal screw removal, which was observed in this study, should be explored in future research. Level III-retrospective comparative series.

Manipulated and Improved Photoinduced Deformation Property of Photoresponsive Liquid Crystal Elastomers by Copolymerization.

Photoresponsive liquid crystal elastomers (LCEs) have aroused much attention due to their unique structures, properties, and potential applications. However, many reported photoresponsive LCEs show small photoinduced deformation with a slow deformation speed, which limits their application to a certain extent. In this article, multiple hydrogen bond component and biphenyl component was introduced into photoresponsive LCEs bearing cyanostilbene by copolymerization, and prepared a series of LCEs CSm-BPn (CS and BP means cyanostilbene and biphenyl component, respectively; m, n means the content ratio of CS and BP). All uniaxially oriented CSm-BPn fibers show photoinduced deformation behavior under 365nm UV light except for CS0-BP5. The introduction of hydrogen bond and the decrease of glass transition temperature realize large deformation and fast deformation speed. Besides, the properties of LCEs are successfully regulated by changing the content ratio of each component. What's more interesting is that the addition of appropriate amount of biphenyl can significantly improve and manipulate the deformation property of the CSm-BPn fibers. The maximum bending angle can reach 175° , and the whole photoinduced deformation process only takes 11 s. The photoresponsive LCEs with such large bending angle and fast deformation rate are rarely reported.

Treatment of comminuted diaphyseal fractures of the femur using closed blocking intramedullary osteosynthesis

During 1996-2000 at the Department of Urgent Traumatology of Loco-Motor System (Scientific Research Institute of Emergency Care named after N.V. Sklifosovskiy) intramedullar osteosynthesis using AO/ASIF blocked pin was performed in 20 patients with comminuted femur fractures (21 fractures). This method gives stabile fixation of fragments that allows to stand up and walk using crutches on 5-10 days after operation. Mean term of load bearing restoration and moving extremity function was 4.5 months. One patient had delayed fragments consolidation. No complications such as suppuration, extremity shortening, angle and rotation deformity were observed.

Failure Criteria of a 6-Inch Carbon Steel Pipe Elbow According to Deformation Angle Measurement Positions

Failure Criteria of a 6-Inch Carbon Steel Pipe Elbow According to Deformation Angle Measurement Positions

Experimental study on seismic performance of steel slit damper under additional tensile load

Hysteretic steel dampers of the flexural/shear yield-type may resist unanticipated tensile load because of their installation pattern, boundary conditions, and scale difference with the frame. In this study, the effect of unexpected additional tensile loads on a flexural yield-type steel slit damper was experimentally analyzed. To this end, two experimental boundary conditions were applied as the experimental variables: 1) shear loading only, and 2) combined shear and tensile loading. Experimental results showed that the damper hysteresis under shear load has a typical parallelogram shape, whereas that under combined shear–tensile loading shows a butterfly-shaped curve. The effect of additional tension is proportional to the aspect ratio and maximum deformation angle of the damper. The plastic deformation capacity according to the cyclic hysteresis of the damper under additional tensile load was found to be similar to that of the damper under shear loading only, and the amount of plastic energy absorbed until failure was measured to be equal or higher. However, the dissipated energy of the damper under additional tensile load contains a substantial amount of unstable energy owing to out-of-plane deformation. According to the test results, the hysteresis of the damper under additional tension was found to be lower than the existing predicted curve for the evaluation of the plastic energy, and a design value was proposed for the predicted curve of the flexural yield-type steel slit damper under an additional tensile load.

Green–Light–Driven Poly(N-isopropylacrylamide-acrylamide)/Fe3O4 Nanocomposite Hydrogel Actuators

Light-responsive hydrogel actuators show attractive biomedical applications for in vivo drug delivery tool, surgical tissue repair operation, and vascular cleaning due to its non-contact, rapid, precise, and remote spatial control of light. Conventional visible–light–responsive hydrogels contain special chemical structure or groups, and the difficulty in synthesis results in that few can be applied to fabricate visible–light–driven hydrogel actuators. In this study, based on photothermal effect, surface-modified Fe3O4 nanoparticles were incorporated into poly(N-isopropylacrylamide-acrylamide) hydrogel by UV photopolymerization, which revealed excellent green–light–responsive volume change. Under a laser irradiation of 200 mW at 520 nm, the bending angle deformation of hydrogel strips with 2.62 wt% Fe3O4 reached 107.8°. Strip-shaped hydrogel actuators could be applied to transport tiny objects. Furthermore, a boomerang-like hydrogel actuator was designed and fabricated to drive floating foam on water. By 12 cycles of continuous laser on–off irradiation to a hydrogel actuator underwater, a circular returning movement of the float was accomplished. The study on driving a float using visible–light–triggered hydrogel actuators provides a new idea for the design of light-driven biomedical devices and soft robots.

Association of Normal vs Abnormal Meary Angle With Hindfoot Malalignment and First Metatarsal Rotation: A Short Report.

Recent work has reported a significant association between first metatarsal (M1) rotation and hindfoot alignment, with the finding of a moderate association between the calcaneal moment arm (CMA) and 2 M1 pronation angular measures: Saltzman (r = 0.641, P < .01) and Kim (r = 0.615, P < .01). The aim of the current post hoc investigation was to determine if this association is related with Meary angle. We reanalyzed previously published data set separating patients into 2 groups: (1) those with normal Meary angle (n = 128) and (2) those with abnormal Meary angle (n = 147). Hindfoot alignment and M1 rotation were measured on weightbearing computed tomography. Statistical analyses were performed to evaluate for association between these variables among the groups. The correlation between CMA and M1 rotation of the entire cohort was r = 0.577 (Saltzman ankle) and r = 0.540 (Kim angle). For the subset with a normal Meary angle, this association was negligible (Saltzman and Kim angles, r = 0.194 and 0.240, respectively). Conversely, for the abnormal Meary angle subset, the association was substantial (Saltzman and Kim angles, r = 0.733 and 0.675, respectively). Patients presenting with an abnormal Meary angle and hindfoot deformity have a high likelihood of manifesting a proportionate degree of M1 rotation. Level III, Retrospective Cohort Study.

Abdominal motion tracking with free-breathing XD-GRASP acquisitions using spatio-temporal geodesic trajectories.

Free-breathing external beam radiotherapy remains challenging due to the complex elastic or irregular motion of abdominal organs, as imaging moving organs leads to the creation of motion blurring artifacts. In this paper, we propose a radial-based MRI reconstruction method from 3D free-breathing abdominal data using spatio-temporal geodesic trajectories, to quantify motion during radiotherapy. The prospective study was approved by the institutional review board and consent was obtained from all participants. A total of 25 healthy volunteers, 12 women and 13 men (38years ± 12 [standard deviation]), and 11 liver cancer patients underwent imaging using a 3.0T clinical MRI system. The radial acquisition based on golden-angle sparse sampling was performed using a 3D stack-of-stars gradient-echo sequence and reconstructed using a discretized piecewise spatio-temporal trajectory defined in a low-dimensional embedding, which tracks the inhale and exhale phases, allowing the separation between distinct motion phases. Liver displacement between phases as measured with the proposed radial approach based on the deformation vector fields was compared to a navigator-based approach. Images reconstructed with the proposed technique with 20 motion states and registered with the multiscale B-spline approach received on average the highest Likert scores for the overall image quality and visual SNR score 3.2 ± 0.3 (mean ± standard deviation), with liver displacement errors varying between 0.1 and 2.0mm (mean 0.8 ± 0.6mm). When compared to navigator-based approaches, the proposed method yields similar deformation vector field magnitudes and angle distributions, and with improved reconstruction accuracy based on mean squared errors. Schematic illustration of the proposed 4D-MRI reconstruction method based on radial golden-angle acquisitions and a respiration motion model from a manifold embedding used for motion tracking. First, data is extracted from the center of k-space using golden-angle sampling, which is then mapped onto a low-dimensional embedding, describing the relationship between neighboring samples in the breathing cycle. The trained model is then used to extract the respiratory motion signal for slice re-ordering. The process then improves the image quality through deformable image registration. Using a reference volume, the deformation vector field (DVF) of sequential motion states are extracted, followed by deformable registrations. The output is a 4DMRI which allows to visualize and quantify motion during free-breathing.

Improved whale optimization-based parameter identification algorithm for dynamic deformation of large ships

In the field of ship deformation measurement, the inertial matching method has become a current research hotspot due to its advantages of high accuracy, easy implementation, and strong real-time performance. However, the parameters of dynamic deformation are affected by the environment, which severely restricts the further improvement of its accuracy. In response to this problem, this paper derives the mapping mechanism between the angular velocity difference and the dynamic deformation angle. And the data in the sliding window is used to establish the objective function on this basis. After that an improved whale optimization algorithm (IWOA) based on logic mapping is designed to perform parameters identification. Simulation and turntable experiment results show that the algorithm proposed in this paper can effectively identify the parameters. The results of the shipboard experiment show that the measurement accuracy of the deformation angle is significantly improved after parameters identification, and the RMS of estimation errors for the pitch, roll and yaw are 10.04′′,12.16′′,9.07′′ respectively.

Makoplasty medial unicondylar knee replacement: Correction or postoperative angle matters?

Various considerations prevail around optimal postoperative varus deformity, correction angle and physiological constitutional varus deformity. The goal of our present study was to understand correlation between these parameters and their influence over Western Ontario McMaster University Osteoarthritis Index scale (WOMAC). Consecutive robotic-arm-assisted medial onlay fixed bearing unicompartmental knee arthroplasty (UKA) in 143 knees studied. WOMAC score was recorded preoperatively and at specific intervals after surgery for consecutive 2 years. Mean preoperative and postoperative varus deformities were 10.2° and 4.8°, respectively, and mean correction angle was 5.4°. The preoperative varus and correction angles were found well correlated (r=0.815). The amount of improvement in the WOMAC total score was not influenced by the postoperative varus angle. The correction angle has a stronger correlation with preoperative varus deformity, and postoperative varus deformity does not imply favourable clinical outcomes.

Angle deformation of Kähler–Einstein edge metrics on Hirzebruch surfaces

We construct a family of K\"ahler-Einstein edge metrics on all Hirzebruch surfaces using the Calabi ansatz and study their angle deformation. This allows us to verify in some special cases a conjecture of Cheltsov-Rubinstein that predicts convergence towards a non-compact Calabi-Yau fibration in the small angle limit. We also give an example of a K\"ahler-Einstein edge metric whose edge singularity is rigid, answering a question posed by Cheltsov.

Follow the Curve: Robotic Ultrasound Navigation With Learning-Based Localization of Spinous Processes for Scoliosis Assessment

The scoliosis progression in adolescents requires close monitoring to timely take treatment measures. Ultrasound imaging is a radiation-free alternative in scoliosis assessment to X-ray, which is typically used in clinical practice. However, ultrasound images are prone to speckle noise, making it challenging for sonographers to detect bony features and follow the spinal curvature. This study introduces a novel robotic ultrasound approach for spinous process localization and automatic spinal curvature tracking for scoliosis assessment. The positions of the spinous processes are computed using a fully connected network with a deconvolutional head. A 5-fold cross-validation was performed on a dataset of ultrasound images from 25 human subjects with scoliosis. The resulting percentage of correct keypoints of the spinous process is 0.966±0.027 with a mean distance error of 1.0±0.99 mm. We use this machine learning-based method to guide the motion of the robot-held ultrasound probe and to follow the spinal curvature while capturing ultrasound images. We present a new force-driven controller that automatically adjusts the pose and orientation of the probe relative to the skin surface, which ensures a good acoustic coupling between the probe and skin. We extended the network architecture to additionally perform classification of the spine into its regions, i.e., sacrum, lumbar, and thoracic, which are used to adjust the probe’s orientation to account for the varying curvature along the spine. After the autonomous scanning, the acquired data is used to reconstruct the coronal spinal image, where the deformity of the scoliosis spine can be assessed and measured. The proposed learning-based method for anatomical landmarks localization was compared to conventional methods based on phase symmetry and image intensity. The learning-based method proved to be more precise for spinous process localization while processing images at a faster rate, which is advantageous for real-time scoliosis scanning. To evaluate the performance of our robotic method, we conducted an experimental study with human scoliosis subjects where deviations of the spinous process from the image center can be compared to those appearing in a manual scan. Our results show that the robotic approach reduces the mean error of spinal curvature following for mild scoliosis from 4.6±4.6mm (manual scanning) to 1.0±0.8mm (robotic scanning); For moderate scoliosis from 4.3±3.9mm (manual scanning) to 2.8±1.8mm (robotic scanning). The angles of spinal deformity measured on spinal reconstruction images were similar for both methods, implying that they equally reflect human anatomy. The spinal region-specific moment-based probe orientation control showed to improve the scanning performance. An ablation study was performed to investigate the importance of each component of the proposed system.