T1-weighted Motion Mitigation in Abdominal MRI: Technical Principles, Clinical Applications, Current Limitations, and Future Prospects.

T1-weighted (T1W) pulse sequences are an indispensable component of clinical protocols in abdominal MRI but usually require multiple breath holds (BHs) during the examination, which not all patients can sustain. Patient motion can affect the quality of T1W imaging so that key diagnostic information, such as intrinsic signal intensity and contrast enhancement image patterns, cannot be determined. Patient motion also has a negative impact on examination efficiency, as multiple acquisition attempts prolong the duration of the examination and often remain noncontributory. Techniques for mitigation of motion-related artifacts at T1W imaging include multiple arterial acquisitions within one BH; free breathing with respiratory gating or respiratory triggering; and radial imaging acquisition techniques, such as golden-angle radial k-space acquisition (stack-of-stars). While each of these techniques has inherent strengths and limitations, the selection of a specific motion-mitigation technique is based on several factors, including the clinical task under investigation, downstream technical ramifications, patient condition, and user preference. The authors review the technical principles of free-breathing motion mitigation techniques in abdominal MRI with T1W sequences, offer an overview of the established clinical applications, and outline the existing limitations of these techniques. In addition, practical guidance for abdominal MRI protocol strategies commonly encountered in clinical scenarios involving patients with limited BH abilities is rendered. Future prospects of free-breathing T1W imaging in abdominal MRI are also discussed. ©RSNA, 2024 See the invited commentary by Fraum and An in this issue.

[A deep blur learning-based motion artifact reduction algorithm for dental cone-beam computed tomography images].

OBJECTIVE: We propose a motion artifact correction algorithm (DMBL) for reducing motion artifacts in reconstructed dental cone-beam computed tomography (CBCT) images based on deep blur learning. METHODS: A blur encoder was used to extract motion-related degradation features to model the degradation process caused by motion, and the obtained motion degradation features were imported in the artifact correction module for artifact removal. The artifact correction module adopts a joint learning framework for image blur removal and image blur simulation for treatment of spatially varying and random motion patterns. Comparative experiments were conducted to verify the effectiveness of the proposed method using both simulated motion data sets and clinical data sets. RESULTS: The experimental results with the simulated dataset showed that compared with the existing methods, the PSNR of the proposed method increased by 2.88%, the SSIM increased by 0.89%, and the RMSE decreased by 10.58%. The results with the clinical dataset showed that the proposed method achieved the highest expert level with a subjective image quality score of 4.417 (in a 5-point scale), significantly higher than those of the comparison methods. CONCLUSION: The proposed DMBL algorithm with a deep blur joint learning network structure can effectively reduce motion artifacts in dental CBCT images and achieve high-quality image restoration.

Research on control strategy of pneumatic soft bionic robot based on improved CPG.

To achieve the accuracy and anti-interference of the motion control of the soft robot more effectively, the motion control strategy of the pneumatic soft bionic robot based on the improved Central Pattern Generator (CPG) is proposed. According to the structure and motion characteristics of the robot, a two-layer neural network topology model for the robot is constructed by coupling 22 Hopfield neuron nonlinear oscillators. Then, based on the Adaptive Neuro-Fuzzy Inference System (ANFIS), the membership functions are offline learned and trained to construct the CPG-ANFIS-PID motion control strategy for the robot. Through simulation research on the impact of CPG-ANFIS-PID input parameters on the swimming performance of the robot, it is verified that the control strategy can quickly respond to input parameter changes between different swimming modes, and stably output smooth and continuous dynamic position signals, which has certain advantages. Then, the motion performance of the robot prototype is analyzed experimentally and compared with the simulation results. The results show that the CPG-ANFIS-PID motion control strategy can output coupled waveform signals stably, and control the executing mechanisms of the pneumatic soft bionic robot to achieve biological rhythms motion propulsion waveforms, confirming that the control strategy has accuracy and anti-interference characteristics, and enable the robot have certain maneuverability, flexibility, and environmental adaptability. The significance of this work lies in establishing a CPG-ANFIS-PID control strategy applicable to pneumatic soft bionic robot and proposing a rhythmic motion control method applicable to pneumatic soft bionic robot.

Verification of the effect of data-driven brain motion correction on PET imaging.

INTRODUCTION: Brain positron emission tomography/computed tomography (PET/CT) scans are useful for identifying the cause of dementia by evaluating glucose metabolism in the brain with F-18-fluorodeoxyglucose or Aß deposition with F-18-florbetaben. However, since imaging time ranges from 10 to 30 minutes, movements during the examination might result in image artifacts, which interfere with diagnosis. To solve this problem, data-driven brain motion correction (DDBMC) techniques are capable of performing motion corrected reconstruction using highly accurate motion estimates with high temporal resolution. In this study, we investigated the effectiveness of DDBMC techniques on PET/CT images using a Hoffman phantom, involving continuous rotational and tilting motion, each expanded up to approximately 20 degrees. MATERIALS AND METHODS: Listmode imaging was performed using a Hoffman phantom that reproduced rotational and tilting motions of the head. Brain motion correction processing was performed on the obtained data. Reconstructed images with and without brain motion correction processing were compared. Visual evaluations by a nuclear medicine specialist and quantitative parameters of images with correction and reference still images were compared. RESULTS: Normalized Mean Squared Error (NMSE) results demonstrated the effectiveness of DDBMC in compensating for rotational and tilting motions during PET imaging. In Cases 1 and 2 involving rotational motion, NMSE decreased from 0.15-0.2 to approximately 0.01 with DDBMC, indicating a substantial reduction in differences from the reference image across various brain regions. In the Structural Similarity Index (SSIM), DDBMC improved it to above 0.96 Contrast assessment revealed notable improvements with DDBMC. In continuous rotational motion, % contrast increased from 42.4% to 73.5%, In tilting motion, % contrast increased from 52.3% to 64.5%, eliminating significant differences from the static reference image. These findings underscore the efficacy of DDBMC in enhancing image contrast and minimizing motion induced variations across different motion scenarios. CONCLUSIONS: DDBMC processing can effectively compensate for continuous rotational and tilting motion of the head during PET, with motion angles of approximately 20 degrees. However, a significant limitation of this study is the exclusive validation of the proposed method using a Hoffman phantom; its applicability to the human brain has not been investigated. Further research involving human subjects is necessary to assess the generalizability and reliability of the presented motion correction technique in real clinical scenarios.

Diagnostic efficiency of intravoxel incoherent motion-based virtual magnetic resonance elastography in pulmonary neoplasms.

BACKGROUND: The aim of the study were as below. (1) To investigate the feasibility of intravoxel incoherent motion (IVIM)-based virtual magnetic resonance elastography (vMRE) to provide quantitative estimates of tissue stiffness in pulmonary neoplasms. (2) To verify the diagnostic performance of shifted apparent diffusion coefficient (sADC) and reconstructed virtual stiffness values in distinguishing neoplasm nature. METHODS: This study enrolled 59 patients (37 males, 22 females) with one pulmonary neoplasm who underwent computed tomography-guided percutaneous transthoracic needle biopsy (PTNB) with pathological diagnosis (26 adenocarcinoma, 10 squamous cell carcinoma, 3 small cell carcinoma, 4 tuberculosis and 16 non-specific benign; mean age, 60.81 ± 9.80 years). IVIM was performed on a 3 T magnetic resonance imaging scanner before biopsy. sADC and virtual shear stiffness maps reflecting lesion stiffness were reconstructed. sADC and virtual stiffness values of neoplasm were extracted, and the diagnostic performance of vMRE in distinguishing benign and malignant and detailed pathological type were explored. RESULTS: Compared to benign neoplasms, malignant ones had a significantly lower sADC and a higher virtual stiffness value (P < 0.001). Subsequent subtype analyses showed that the sADC values of adenocarcinoma and squamous cell carcinoma groups were significantly lower than non-specific benign group (P = 0.013 and 0.001, respectively). Additionally, virtual stiffness values of the adenocarcinoma and squamous cell carcinoma subtypes were significantly higher than non-specific benign group (P = 0.008 and 0.001, respectively). However, no significant correlation was found among other subtype groups. CONCLUSIONS: Non-invasive vMRE demonstrated diagnostic efficiency in differentiating the nature of pulmonary neoplasm. vMRE is promising as a new method for clinical diagnosis.

Batch Fabrication of Flexible Strain Sensors with High Linearity and Low Hysteresis for Health Monitoring and Motion Detection.

In recent years, flexible strain sensors have gradually come into our lives due to their superiority in the field of biomonitoring. However, these sensors still suffer from poor durability, high hysteresis, and difficulty in calibration, resulting in great hindrance of practical application. Herein, starting with interfacial interaction regulation and structure-induced cracking, flexible strain sensors with high performance are successfully fabricated. In this strategy, dopamine treatment is used to enhance the bonding between flexible substrates and carbon nanotubes (CNT). The combination within the conductive networks is then controlled by substituting the CNT type. Braid-like fibers are employed to achieve controllable expansion of the conductive layer cracks. Finally, we obtain strain sensors that possess high linearity (R2 = 0.997) with low hysteresis (5%), high sensitivity (GF = 60) and wide sensing range (0-50%), short response time (62 ms), outstanding stability, and repeatability (>10,000 cycles). Flexible strain sensors with all performances good are rarely reported. Static and dynamic respiration and pulse signal monitoring by the fiber sensor are demonstrated. Moreover, a knee joint monitoring system is constructed for the monitoring of various walking stances, which is of great value to the diagnosis and rehabilitation of many diseases.

Design of Cellulose Nanocrystal-Based Self-Healing Nanocomposite Hydrogels and Application in Motion Sensing and Sweat Detection.

Hydrogels, as flexible materials, have been widely used in the field of flexible sensors. Human sweat contains a variety of biomarkers that can reflect the physiological state of the human body. Therefore, it is of great practical significance and application value to realize the detection of sweat composition and combine it with human motion sensing through a hydrogel. Based on mussel-inspired chemistry, polydopamine (PDA) and gold nanoparticles (AuNPs) were coated on the surface of cellulose nanocrystals (CNCs) to obtain CNC-based nanocomposites (CNCs@PDA-Au), which could simultaneously enhance the mechanical, electrochemical, and self-healing properties of hydrogels. The CNCs@PDA-Au was composited with poly(vinyl alcohol) (PVA) hydrogel to obtain the nanocomposite hydrogel (PVA/CNCs@PDA-Au) by freeze-thaw cycles. The PVA/CNCs@PDA-Au has excellent mechanical strength (7.2 MPa) and self-healing properties (88.3%). The motion sensors designed with PVA/CNCs@PDA-Au exhibited a fast response time (122.9 ms), wide strain sensing range (0-600.0%), excellent stability, and fatigue resistance. With the unique electrochemical redox properties of uric acid, the designed hydrogel sensor successfully realized the detection of uric acid in sweat with a wide detection range (1.0-100.0 µmol/L) and low detection limit (0.42 µmol/L). In this study, the dual detection of human motion and uric acid in sweat was successfully realized by the designed PVA/CNCs@PDA-Au nanocomposite hydrogel.

Dynamic behavior of DNA molecules in microchannels: exploring deflective, elliptical, and spin motions induced by Saffman and Magnus forces.

Precise manipulation of individual DNA molecules entering and leaving the channel ports, as well as their smooth passage across the channel, is essential for the detection and screening of DNA molecules using nano-/micro-fluidic technologies. In this paper, by combining single-molecule fluorescence imaging and numerical simulations, the motion states of DNA molecules translocating through a microfluidic channel under the action of the applied electric field are monitored and analyzed in detail. It is found that, under certain conditions of the applied electric field DNA molecules exhibit various motion states, including translation crossing, deflection outflow, reverse outflow, reciprocal movement, and elliptical movement. Simulations indicate that, under the action of Saffman force, DNA molecules can only undergo deflective motion when they experience a velocity gradient in the microchannel flow field; and they can only undergo elliptical motion when their deflective motion is accompanied by a spin motion. In this case, the Magnus force also plays an important role. The detailed study and elucidation of the movement states, dynamic characteristics and mechanisms of DNA molecules such as the deflective and elliptical motions under the actions of Saffman and Magnus forces have helpful implications for the development of related DNA/gene nano-/microfluidic chips, and for the separation, screening and detection of DNA molecules.

Magnetic motors in interphases: Motion control and integration in soft robots.

Magnetic motors are a class of out-of-equilibrium particles that exhibit controlled and fast motion overcoming Brownian fluctuations by harnessing external magnetic fields. The advances in this field resulted in motors that have been used for different applications, such as biomedicine or environmental remediation. In this Perspective, an overview of the recent advancements of magnetic motors is provided, with a special focus on controlled motion. This aspect extends from trapping, steering, and guidance to organized motor grouping and degrouping, which is known as swarm control. Further, the integration of magnetic motors in soft robots to actuate their motion is also discussed. Finally, some remarks and perspectives of the field are outlined.

Landing force reveals new form of motion-induced sound camouflage in a wild predator.

Predator-prey arms races have led to the evolution of finely tuned disguise strategies. While the theoretical benefits of predator camouflage are well established, no study has yet been able to quantify its consequences for hunting success in natural conditions. We used high-resolution movement data to quantify how barn owls (Tyto alba) conceal their approach when using a sit-and-wait strategy. We hypothesized that hunting barn owls would modulate their landing force, potentially reducing noise levels in the vicinity of prey. Analysing 87,957 landings by 163 individuals equipped with GPS tags and accelerometers, we show that barn owls reduce their landing force as they approach their prey, and that landing force predicts the success of the following hunting attempt. Landing force also varied with the substrate, being lowest on man-made poles in field boundaries. The physical environment, therefore, affects the capacity for sound camouflage, providing an unexpected link between predator-prey interactions and land use. Finally, hunting strike forces in barn owls were the highest recorded in any bird, relative to body mass, highlighting the range of selective pressures that act on landings and the capacity of these predators to modulate their landing force. Overall, our results provide the first measurements of landing force in a wild setting, revealing a new form of motion-induced sound camouflage and its link to hunting success.

Curved Surfaces Induce Metachronal Motion of Microscopic Magnetic Cilia.

Cilia are hair-like organelles present on cell surfaces. They often exhibit a collective wave-like motion that can enhance fluid or particle transportation function, known as metachronal motion. Inspired by nature, researchers have developed artificial cilia capable of inducing metachronal motion, especially magnetic actuation. However, current methods remain intricate, requiring either control of the magnetic or geometrical properties of individual cilia or the generation of a complex magnetic field. In this paper, we present a novel elegant method that eliminates these complexities and induces metachronal motion of arrays of identical microscopic magnetic artificial cilia by applying a simple rotating uniform magnetic field. The key idea of our method is to place arrays of cilia on surfaces with a specially designed curvature. This results in consecutive cilia experiencing different magnetic field directions at each point in time, inducing a phase lag in their motion, thereby causing collective wave-like motion. Moreover, by tuning the surface curvature profile, we can achieve diverse metachronal patterns analogous to symplectic and antiplectic metachronal motion observed in nature, and we can even devise novel combinations thereof. Furthermore, we characterize the local flow patterns generated by the motion of the cilia, revealing the formation of vortical patterns. Our novel approach simplifies the realization of miniaturized metachronal motion in microfluidic systems and opens the possibility of controlling flow pattern generation and transportation, opening avenues for applications such as lab-on-a-chip technologies, organ-on-a-chip platforms, and microscopic object propulsion.

Tethered Particle Motion Technique in Crowded Media: Compaction of DNA by Globular Macromolecules.

Tethered Particle Motion (TPM) is a single molecule technique, which consists in tracking the motion of a nanoparticle (NP) immersed in a fluid and tethered to a glass surface by a DNA molecule. The present work addresses the question of the applicability of TPM to fluids which contain crowders at volume fractions ranging from that of the nucleoid of living bacteria (around 30%) up to the jamming threshold (around 66%). In particular, we were interested in determining whether TPM can be used to characterize the compaction of DNA by globular crowders. To this end, extensive Brownian Dynamics simulations were performed with a specifically built coarse-grained model. Analysis of the simulations reveals several effects not observed in dilute media, which impose constraints on the TPM setup. In particular, the Tethered Fluorophore Motion (TFM) technique, which consists in replacing the NP by a much smaller fluorophore, is probably better suited than standard TPM. Moreover, a sample preparation technique which does not involve hydrophilic patches may be required. Finally, the use of a DNA brush may be needed to achieve DNA concentrations close to in vivo ones.

Measurement of wing motion, deformation, and inertial forces of a biomimetic butterfly.

This paper introduces a method for measuring wing motion, deformation, and inertial forces in bio-inspired aircraft research using a camera motion capture system. The method involves placing markers on the wing surface and fitting rigid planes to determine the wing's spatial axis. This allows for describing the wing's rigid motion and obtaining deformation characteristics, such as deflection, twist angle, and gap distance of the forewing and hindwing. An image-based method is proposed for determining wing mass distribution, mass blocks, and mass points for inertial force measurement. The study addresses wing motion, deformation, and inertial force measurement in a real butterfly-like flapping wing vehicle and demonstrates the effectiveness of the approach. The results reveal that inertial forces play a negligible role in the generation of lift peaks and contribute minimal lift during the entire flapping cycle. Furthermore, a transitional phase between downstroke and upstroke is found in flexible wing motion, which has high lift production. This measurement approach offers a rapid and effective solution to experimental challenges in bio-inspired aircraft design and optimization.

Analysis of the effect of motion on highly accelerated 3D FatNavs in 3D brain images acquired at 3T.

PURPOSE: 3D FatNavs are rapid acquisitions of MRI fat-volumes within the head that can be used for retrospective motion correction for brain MRI. 3D FatNavs typically use very high acceleration factors and are reconstructed with the GRAPPA parallel imaging technique. However, the GRAPPA reconstruction is not expected to perform well on 3D FatNavs volumes in the presence of strong motion due to the mismatched calibration data acquired once at the start of the scan, leading to motion-parameter misestimation. This study aims to assess the accuracy and precision of 3D FatNav-derived motion-estimates in the presence of large changes in head position. METHODS: Rigid motion parameters were simulated and applied retrospectively to the 3D FatNav volumes from MPRAGE datasets acquired at 3T. The transformed images were then re-reconstructed using GRAPPA to simulate real motion deterioration of the fat-navigator, and used to estimate the motion applied and evaluate the tracking inaccuracy. This information was then used to estimate the residual motion after 3D FatNav-based motion correction and applied to the original MPRAGE volumes. The effect of the misestimation was assessed using an image quality metric and the evaluation scores from two observers. Quality boundaries were then estimated to assess the motion tolerance when 3D FatNavs are used. RESULTS: The GRAPPA reconstruction was shown to deteriorate for large changes in the head position, affecting the quality of 3D FatNav volumes and consequently degrading the accuracy of the motion-estimates. Based on our simulations, the estimated threshold of motion that led to a noticeable degradation in the MPRAGE image quality was up to RMS values of 3.7° and 3 mm for rotations and translations respectively. CONCLUSIONS: 3D FatNavs were shown to be able to correct for a wide range of motion levels and types. Boundaries of acceptable motion magnitudes for different levels of acceptable loss of image quality were determined.

Quantitation of DNA Binding Affinity Using Tethered Particle Motion.

The binding constant is an important characteristic of a DNA-binding protein. A large number of methods exist to measure the binding constant, but many of those methods have intrinsic flaws that influence the outcome of the characterization. Tethered particle motion (TPM) is a simple, cheap, and high-throughput single-molecule method that can be used to measure binding constants of proteins binding to DNA reliably, provided that they distort DNA. In TPM, the motion of a bead tethered to a surface by DNA is tracked using light microscopy. A protein binding to the DNA will alter bead motion. This change in bead motion makes it possible to measure the DNA-binding properties of proteins. We use the bacterial protein integration host factor (IHF) and the archaeal histone HMfA as examples to show how specific binding to DNA can be measured. Moreover, we show how the end-to-end distance can provide structural insights into protein-DNA binding.

Tethered Particle Motion Analysis of DNA-Binding Properties of Architectural Proteins.

Architectural DNA-binding proteins are key to the organization and compaction of genomic DNA inside cells. Tethered particle motion (TPM) permits analysis of DNA conformation and detection of changes in conformation induced by such proteins at the single molecule level in vitro. As many individual protein-DNA complexes can be investigated in parallel, these experiments have high throughput. TPM is therefore well suited for characterization of the effects of protein-DNA stoichiometry and changes in physicochemical conditions (pH, osmolarity, and temperature). Here, we describe in detail how to perform tethered particle motion experiments on complexes between DNA and architectural proteins to determine their structural and biochemical characteristics.

A dynamic flow fetal membrane organ-on-a-chip system for modeling the effects of amniotic fluid motion.

Fetal membrane (amniochorion), the innermost lining of the intrauterine cavity, surround the fetus and enclose amniotic fluid. Unlike unidirectional blood flow, amniotic fluid subtly rocks back and forth, and thus, the innermost amnion epithelial cells are continuously exposed to low levels of shear stress from fluid undulation. Here, we tested the impact of fluid motion on amnion epithelial cells (AECs) as a bearer of force impact and their potential vulnerability to cytopathologic changes that can destabilize fetal membrane functions. A previously developed amnion membrane (AM) organ-on-chip (OOC) was utilized but with dynamic flow to culture human fetal amnion membrane cells. The applied flow was modulated to perfuse culture media back and forth for 48 h to mimic fluid motion. A static culture condition was used as a negative control, and oxidative stress (OS) condition was used as a positive control representing pathophysiological changes. The impacts of fluidic motion were evaluated by measuring cell viability, cellular transition, and inflammation. Additionally, scanning electron microscopy (SEM) imaging was performed to observe microvilli formation. The results show that regardless of the applied flow rate, AECs and AMCs maintained their viability, morphology, innate meta-state, and low production of pro-inflammatory cytokines. E-cadherin expression and microvilli formation in the AECs were upregulated in a flow rate-dependent fashion; however, this did not impact cellular morphology or cellular transition or inflammation. OS treatment induced a mesenchymal morphology, significantly higher vimentin to cytokeratin 18 (CK-18) ratio, and pro-inflammatory cytokine production in AECs, whereas AMCs did not respond in any significant manner. Fluid motion and shear stress, if any, did not impact AEC cell function and did not cause inflammation. Thus, when using an amnion membrane OOC model, the inclusion of a dynamic flow environment is not necessary to mimic in utero physiologic cellular conditions of an amnion membrane.

Investigation of Motor Learning Effects Using a Hybrid Rehabilitation System Based on Motion Estimation.

Upper-limb paralysis requires extensive rehabilitation to recover functionality for everyday living, and such assistance can be supported with robot technology. Against such a background, we have proposed an electromyography (EMG)-driven hybrid rehabilitation system based on motion estimation using a probabilistic neural network. The system controls a robot and functional electrical stimulation (FES) from movement estimation using EMG signals based on the user's intention, enabling intuitive learning of joint motion and muscle contraction capacity even for multiple motions. In this study, hybrid and visual-feedback training were conducted with pointing movements involving the non-dominant wrist, and the motor learning effect was examined via quantitative evaluation of accuracy, stability, and smoothness. The results show that hybrid instruction was as effective as visual feedback training in all aspects. Accordingly, passive hybrid instruction using the proposed system can be considered effective in promoting motor learning and rehabilitation for paralysis with inability to perform voluntary movements.