Irregular Motion Research Articles

RePLaT-Chaos: A Simple Educational Application to Discover the Chaotic Nature of Atmospheric Advection

Large-scale atmospheric pollutant spreading via volcano eruptions and industrial accidents may have serious effects on our life. However, many students and non-experts are generally not aware of the fact that pollutant clouds do not disperse in the atmosphere like dye blobs on clothes. Rather, an initially compact pollutant cloud soon becomes strongly stretched with filamentary and folded structure. This is the result of the chaotic behaviour of advection of pollutants in 3-D flows, i.e., the advection dynamics of pollutants shows the typical characteristics such as sensitivity to the initial conditions, irregular motion, and complicated but well-organized (fractal) structures. This study presents possible applications of a software called RePLaT-Chaos by means of which the characteristics of the long-range atmospheric spreading of volcanic ash clouds and other pollutants can be investigated in an easy and interactive way. This application is also a suitable tool for studying the chaotic features of the advection and determines two quantities which describe the chaoticity of the advection processes: the stretching rate quantifies the strength of the exponential stretching of pollutant clouds; and the escape rate characterizes the rate of the rapidity by which the settling particles of a pollutant cloud leave the atmosphere.

Magnetically modulated orbit for human motion energy harvesting

Human energy harvesting for powering wearable or portable electronics has been extensively studied. We propose an electromagnetic energy harvester with a magnetic orbit (EMH-MO) for low-frequency and irregular human motion energy harvesting. A circular uniform low potential orbit is designed using the reasonable arrangement of multiple magnetic fields. Driven by irregular excitations, the moving magnet is magnetically modulated to move more regularly along the noncontact magnetic orbit, which is conducive to electromechanical energy conversion. A theoretical model is established to characterize the proposed energy harvester. Both simulations and experiments indicate that EMH-MO can work effectively under ultralow frequency (<5 Hz) weak excitation. The peak-peak open-circuit voltage is 4.3 V, and the average power is 0.33 mW under a reciprocating motion of 10 Hz and 20 mm. Besides, the EMH-MO can effectively harvest energy from walking, jogging, and running of people with different physical characteristics (chunky males, tall males, and petite females).

Wave induced motions of partially submerged bodies near a fixed structure

Wave driven impact of small icebergs with offshore structures is a design consideration in Arctic and sub-Arctic regions. The near field hydrodynamic interaction of these wave driven ice masses has been investigated through experimental and CFD studies by Sayeed et al. (2017b, 2018a, 2018b). These studies found that motions were significantly influenced by the standing wave generated due to the superposition of the incident and reflected waves in front of the fixed structure. In regular waves the small bodies may or may not impact the structure, depending on initial starting condition whereas in irregular waves the ice masses hit the structure in all cases. Spectrum analysis carried out over the entire distance travelled by the free floating ice mass in irregular waves revealed relatively small difference in surge and heave velocity due to the presence of the structure (Sayeed et al. (2018b)). The reason is attributed to insufficient data at each separation distances to capture the motion responses for all the frequencies in the spectrum. In this paper, the surge and heave motion time series data in irregular waves are reanalyzed in a similar manner as was previously done for regular waves (Sayeed et al. (2018a). The present analysis reveals correlation of significant wavelength with the motion history at variable separation distances in front of the fixed structure. A statistical approach is then adopted to both regular and irregular wave motion data sets to identify percentiles of velocity response vs position as the small floating bodies approach head on to the fixed structure. These findings enable the identification of the motions of small bodies at specific locations in front of the structure and provide understanding of how wave-induced surge and heave velocities change as small floating bodies approach a fixed structure in a realistic wave field.

Oб эмпирических моделях нерегулярной качки корабля

Oб эмпирических моделях нерегулярной качки корабля

Seafloor massive sulphide exploration using deep-towed controlled source electromagnetics: Navigational uncertainties

SUMMARY Deep-towed geophysical surveys require precise knowledge of navigational parameters such as instrument position and orientation because navigational uncertainties reflect in the data and therefore in the inferred geophysical properties of the sub-seafloor. We address this issue for the case of electrical conductivity inferred from controlled source electromagnetic data. We show that the data error is laterally variable due to irregular motion during deep towing, but also due to lateral variations in conductivity, including those resulting from topography. To address this variability and quantify the data error prior to inversion, we propose a two-dimensional perturbation study. Our workflow enables stable and geologically reliable results for multi-component and multi-frequency inversions. An error estimation workflow is presented, which comprises the assessment of navigational uncertainties, perturbation of navigational parameters, and forward modelling of electric field amplitudes for a homogeneous and then a heterogeneous sub-seafloor conductivity model. Some navigational uncertainties are estimated from variations of direct measurements. Other navigational parameters required for inversion are derived from the measured quantities and their error is calculated by means of error propagation. Some navigational parameters show direct correlation with the measured electric fields. For example, the antenna dip correlates with the vertical electric field and the depth correlates with the horizontal electric field. For the perturbation study each standard deviation is added to the navigational parameters. Forward models are run for each perturbation. Amplitude deviations are summed in quadrature with the stacking error for a total, laterally varying, data error. The error estimation is repeated for a heterogeneous sub-seafloor model due to the large conductivity range (several orders of magnitude), which affects the forward model. The approach enables us to utilize data from several components (multiple electric fields, frequencies and receivers) in the inversion to constrain the final model and reduce ambiguity. The final model is geologically reasonable, in this case enabling the identification of conductive metal sulphide deposits on the seafloor.

Dosimetric effect of a change in breathing patterns between simulation and delivery on VMAT lung stereotactic body radiation therapy (SBRT)

In radiotherapy planning, it is vital that the breathing patterns at simulation scan mimic treatment scenario as accurately as possible. A number of previous studies assumed that a patient has the same breathing trace shape at both simulation and treatment delivery. This is not always the case and this work was to evaluate the dosimetric effect of a change in breathing patterns between planning and delivery in lung volumetric modulated arc therapy (VMAT) stereotactic body radiation therapy (SBRT). A TrueBeam LINAC with 6MV flattened filter free (FFF) beams was used. A dynamic motion phantom with sinusoidal (reference) motion (20 mm diameter ‘tumour’; period = 3 s; amplitude = 30 mm) underwent a 4D-CT scan. A treatment plan was created using Eclipse version 15.1 and optimised according to St Luke’s protocol. The delivered plan was evaluated in five situations: using the same trace as simulation, using a modified trace which contained variabilities in amplitude (VA), using a modified trace which contained variabilities in period (VP), using a highly regular trace (RT), and finally using a highly irregular trace (IRT). Measurements were made with EBT-XD films and evaluated against convolved dose distribution using a gamma analysis of 3% dose difference and 2 mm distance to agreement. Results indicate that both sinusoidal and RT traces showed a high passing rate of more than 98%. However, there was more variability in passing rates for the irregular motion. Results and dosimetric analysis will be presented.

Simultaneous electrophysiological and morphological assessment of functional damage to neural networks in vitro after 30\u2013300\u2009g impacts

An enigma of mild traumatic brain injury are observations of substantial behavior and performance deficits in the absence of bleeding or other observable structural damage. Altered behavior and performance reflect changes in action potential (AP) patterns within neuronal networks, which could result from subtle subcellular responses that affect synaptic efficacy and AP production. The aim of this study was to investigate and quantify network activity changes after simulated concussions in vitro and therewith develop a platform for simultaneous and direct observations of morphological and electrophysiological changes in neural networks. We used spontaneously active networks grown on microelectrode arrays (MEAs) to allow long-term multisite monitoring with simultaneous optical observations before and after impacts delivered by a ballistic pendulum (30 to 300 g accelerations). The monitoring of AP waveshape templates for long periods before and after impact provided an internal control for cell death or loss of cell-electrode coupling in the observed set of neurons. Network activity patterns were linked in real-time to high power phase contrast microscopy. There was no overt loss of glial or neuronal adhesion, even at high-g impacts. All recording experiments showed repeatable spike production responses: a loss of activity with recovery to near reference in 1 hr, followed by a slow activity decay to a stable, level plateau approximately 30–40% below reference. The initial recovery occurred in two steps: a rapid return of activity to an average 24% below reference, forming a level plateau lasting from 5 to 20 min, followed by a climb to within 10% of reference where a second plateau was established for 1 to 2 hrs. Cross correlation profiles revealed changes in firing hierarchy as well as in Phase 1 in spontaneous network oscillations that were reduced by as much as 20% 6–8 min post impact with only a partial recovery at 30 min. We also observed that normally stable nuclei developed irregular rotational motion after impact in 27 out of 30 networks. The evolution of network activity deficits and recovery can be linked with microscopically observable changes in the very cells that are generating the activity. The repeatable electrophysiological impact response profiles and oscillation changes can provide a quantitative basis for systematic evaluations of pharmacological intervention strategies. Future expansion to include fluorescent microscopy should allow detailed investigations of damage mechanisms on the subcellular level.

Measurement of the microlayer characteristics in the whole range of nucleate boiling for water by laser interferometry

During nucleate boiling, a thin liquid film (microlayer) is formed beneath a boiling bubble when the bubble undergoes rapid growth/expansion. The linear distribution of the microlayer has been previously confirmed, and its crest shape has been observed in the isolated bubble region of nucleate boiling. However, the microlayer behavior in larger heat flux regions up to critical heat flux has not yet been elucidated. In this study, to further understand the microlayer structure in the whole heat flux range of nucleate boiling, microlayer configuration was measured using laser interferometry. Water was adopted as the test fluid, and it is confirmed that the microlayer can be observed over a whole range of nucleate boiling containing the critical heat flux point. It is also confirmed that the deformation of the microlayer from axisymmetric shape was caused by complicated, irregular bubble motions such as bubble coalescence, which was observed for relatively higher heat flux. The crest shape of the microlayer, which appears near the periphery of its maximum diameter under relatively smaller heat flux, was not observed at a relatively higher heat flux. Finally, it is confirmed that heat flux does not obviously influence the thickness distribution of the initial microlayer.

Stack transition artifact removal (STAR) for cardiac CT.

In cardiac computed tomography (CT), irregular motion may lead to unique artifacts for scanners with a longitudinal collimation that does not cover the entire heart. Given partial coverage, subvolumes, or stacks, may be reconstructed and used to assemble a final CT volume. Irregular motion, for example, due to cardiac arrhythmia or breathing, may cause mismatch between neighboring stacks and therefore discontinuities within the final CT volume. The aim of this work is the removal of the discontinuities that are hereafter referred to as stack transition artifacts. A stack transition artifact removal (STAR) is achieved using a symmetric deformable image registration. A symmetric Demons algorithm was implemented and applied to stacks to remove mismatch and therefore the stack transition artifacts. The registration can be controlled with one parameter that affects the smoothness of the deformation vector field (DVF). The latter is crucial for realistically transforming the stacks. Different smoothness settings as well as an entirely automatic parameter selection that considers the required deformation magnitude for each registration were tested with patient data. Thirteen datasets were evaluated. Simulations were performed on two additional datasets. STAR considerably improved image quality while computing realistic DVFs. Discontinuities, for example, appearing as breaks or cuts in coronary arteries or cardiac valves, were removed or considerably reduced. A constant smoothing parameter that ensured satisfactory results for all datasets was found. The automatic parameter selection was able to find a proper setting for each individual dataset. Consequently, no over regularization of the DVF occurred that would unnecessarily limit the registration accuracy for cases with small deformations. The automatic parameter selection yielded the best overall results and provided a registration method for cardiac data that does not require user input.

Design of Efficient Perspective Affine Motion Estimation/Compensation for Versatile Video Coding (VVC) Standard

The fundamental motion model of the conventional block-based motion compensation in High Efficiency Video Coding (HEVC) is a translational motion model. However, in the real world, the motion of an object exists in the form of combining many kinds of motions. In Versatile Video Coding (VVC), a block-based 4-parameter and 6-parameter affine motion compensation (AMC) is being applied. In natural videos, in the majority of cases, a rigid object moves without any regularity rather than maintains the shape or transform with a certain rate. For this reason, the AMC still has a limit to compute complex motions. Therefore, more flexible motion model is desired for new video coding tool. In this paper, we design a perspective affine motion compensation (PAMC) method which can cope with more complex motions such as shear and shape distortion. The proposed PAMC utilizes perspective and affine motion model. The perspective motion model-based method uses four control point motion vectors (CPMVs) to give degree of freedom to all four corner vertices. Besides, the proposed algorithm is integrated into the AMC structure so that the existing affine mode and the proposed perspective mode can be executed adaptively. Because the block with the perspective motion model is a rectangle without specific feature, the proposed PAMC shows effective encoding performance for the test sequence containing irregular object distortions or dynamic rapid motions in particular. Our proposed algorithm is implemented on VTM 2.0. The experimental results show that the BD-rate reduction of the proposed technique can be achieved up to 0.45% and 0.30% on Y component for random access (RA) and low delay P (LDP) configurations, respectively.

Pedestrian Flow Optimization to Reduce the Risk of Crowd Disasters Through Human–Robot Interaction

Pedestrian flow in densely populated or congested areas usually presents irregular or turbulent motion state due to competitive behaviors of individual pedestrians, which reduces flow efficiency and raises the risk of crowd accidents. Effective pedestrian flow regulation strategies are highly valuable for flow optimization. Existing studies seek for optimal design of indoor architectural features and spatial placement of pedestrian facilities for the purpose of flow optimization. However, once placed, the stationary facilities are not adaptive to real-time flow changes. In this paper, we investigate the problem of regulating two merging pedestrian flows in a bottleneck area using a mobile robot moving among the pedestrian flows. The pedestrian flows are regulated through dynamic human-robot interaction (HRI) during their collective motion. We adopt an adaptive dynamic programming (ADP) method to learn the optimal motion parameters of the robot in real time, and the resulting outflow through the bottleneck is maximized with the crowd pressure reduced to avoid potential crowd disasters. The proposed algorithm is a data-driven approach that only uses camera observation of pedestrian flows without explicit models of pedestrian dynamics and HRI. Extensive simulation studies are performed in both MATLAB and a robotic simulator to verify the proposed approach and evaluate the performances.

Sniffer-Net: quantitative evaluation of smoke in the wild based on spatial–temporal motion spectrum

Smoke detection plays an essential role in the wild video surveillance systems for abnormal events warning. In this paper, we introduced a dedicated neural network structure named Sniffer-Net to simultaneously extract smoke dynamic feature robustly and evaluate the smoke concentration accurately. Firstly, we utilize an improved LiteFlowNet to estimate the global optical flow from image sequence. Meanwhile, a Marr–Hildreth method is brought up and fused into this network to distinguish and eliminate occluded regions from global flow map. Then, an evaluation module based on Context-Encoder network is put forward specially to quantify smoke concentration levels. This network, following the improved LiteFlowNet, is modified through replacing the loss function and removing the multiscale scheme and trained to infer approximate smoke optical flow behind occlusion regions. Starting from the statistical view, the irregular RGB/HSV feature spaces are converted into a specific quantitative evaluation space. As a result, the whole evaluation system is responsible to transform the distribution of irregular smoke motion feature into a quantified form of representation. In turn, this transformation endows the system with a novel numerical standard for smoke concentration evaluation. Finally, an accuracy assessment method is applied to compare the results of detected smoke concentration with the human experience prior model, which feedback the accuracy and false detection rate of system algorithm. In the experiments of five smoke datasets, our proposed smoke detection approach is superior to other state-of-the-art methods, and concentration algorithm achieves the satisfactory performance of 97.3% accuracy on some specialized dataset.

Validation of a model for physical dose variations in irregularly moving targets treated with carbon ion beams.

In particle therapy, conventional treatment planning systems rely on an imaging representation of the irradiated region to compute the dose. For irregular breathing, when an imaging dataset describing the actual motion is not available, a different approach for dose estimation is needed. To this aim, we validate a method for the estimation of physical dose variations in gated carbon ion treatments, providing also a demonstration of the feasibility of physical dose metrics to assess the method performance. Finally, we describe a sample use case, in which this method is used to assess plan robustness with respect to undetected irregular tumor motion. The method entails the definition of a patient- and beam-specific water equivalent depth (WED) space, the simulation of motion as a translation equal to tumor displacement, and the reconstruction of the altered dose. We validated the approach using four-dimensional computed tomographies (4DCTs) and clinical plans in 12 patients, treated with respiratory gated carbon ion beams at the National Centre for Oncological Hadrontherapy (Pavia, Italy). Using the end-exhale CT and dose distribution as a reference, the physical dose delivered at the end-inhale tumor position was estimated and compared to the ground-truth dose recalculation on the end-inhale CT. Biologically effective and physical dose variations between the plan and the recalculation were compared as well. As a use case, we evaluated dose changes caused by simulated irregular tumor motion, that is, linear and nonlinear baseline shifts and/or amplitude variations with hysteresis. The ratio between biologically effective and physical equivalent uniform dose (EUD) variations due to end-exhale to end-inhale motion was less than one for 96% of investigated structures. In the validation study, we found a median error corresponding to a 14% EUD overestimation for the tumor and 4% EUD underestimation for a subgroup of organs at risk, together with a high EUD variation due to motion [median 352% EUD variation between end-exhale and end-inhale doses in the planning tumor volume (PTV)]. Considering relevant dose-volume histogram (DVH) metrics, the median difference between estimated and ground truth doses was≤4%. Gamma analysis between estimated and recalculated dose distributions resulted in a pass rate>80% for 83% of the target volumes. For the two patients selected for the sample use case, a patient-specific assessment of the method performance was performed on the 4DCT and it was possible to relate EUD variations of both tumor and organs at risk to the simulated target motion. The physical dose distribution was found to be more sensitive to motion with respect to the biologically effective one, suggesting the suitability of the physical dose metrics for the WED-space method validation. We showed that the method can compensate for intra-fractional tumor motion with proper accuracy in the selected patient group, although its use is recommended when limited deformations are expected. In conclusion, the WED-space method can provide simulations of dose alteration due to irregular breathing when imaging data are lacking, and, once integrated with relative biological effectiveness (RBE) modeling, it would be useful in evaluating the robustness of carbon ion treatment plans.

A rotational pendulum based electromagnetic/triboelectric hybrid-generator for ultra-low-frequency vibrations aiming at human motion and blue energy applications

There is abundance of low-frequency biomechanical and blue energy that can be harvested from our ambient environment. Utilization of these energy plays a significant role for the sustainability of the wearable devices and environmental monitoring devices. Here, we presented a rotational pendulum triboelectric-electromagnetic hybrid generator (RPHG) which is able to scavenge low-frequency (<5 Hz) vibration energy from both arbitrary human motion and ocean waves. Four stacked disk-shaped rotor magnets are introduced into the generator for the rotational motion. The pendulum rotor can easily rotate around the bearing by gravity or inertia force with a broadband frequency excitation, and coupled with surrounding coils to operate electromagnetic generator (EMG). In the meantime, triboelectric nanogenerator (TENG) is realized by utilizing the rotor to trigger the contact-separation mode of the copper ring and surrounding fluorinated ethylene propylene (FEP) film. The hybridized generator is very sensitive to irregular human motion and ultra-low-frequency ocean waves. After the optimization of the configuration of the hybrid generator, the maximum power density of 3.25 W/m2 and 79.9 W/m2 are obtained at a driving frequency of 2 Hz and amplitude of 14 cm by the TENG and EMG, respectively, which can charge a capacitor of 22 μF to 7 V rapidly in 30 s. The RPHG can light up about more than hundreds of commercial lights emitting diodes (LEDs). Then, the RPHG was placed on human body and tested by running on treadmill and rope skipping. The open-circuit voltage of the EMG can be about 9 V and that of TENG can reach 150 V. Finally, the RPHG was tested on a homemade buoy in Tai Lake. When the wave frequency is about 1 Hz and the wave height is 20 cm, the open-circuit voltage of EMG can reach over 3 V and that of TENG can reach 80 V regardless of whether the RPHG is placed vertically or horizontally. Generally, the proposed device demonstrates the effectiveness towards energy harvesting from ambient environment of multidirectional and wide frequency range, i.e., human motion and blue energy, showing the great potential of being a sustainable power source for those wearable devices and monitoring devices in blue ocean.

A design chart approach for the tuning of parallel and trapezoidal bifilar centrifugal pendulum

The centrifugal pendulum is a device used to reduce torsional vibrations generated by motion irregularities of rotating machinery. It is adopted in many engineering applications. Even though different arrangements have been developed, because of its versatility, bifilar pendulum is the most commonly used architecture.In this paper, a new modeling approach and a novel design chart procedures for the trapezoidal bifilar centrifugal pendulum vibration absorber are proposed.In the first part, the case of parallel bifilar centrifugal pendulum is considered.In the second part, an innovative approach for the trapezoidal bifilar centrifugal pendulum design is proposed. For the first time, it has been established a dynamic equivalence between the trapezoidal bifilar and the unifilar centrifugal pendulum. This allowed the development of designs charts for trapezoidal bifilar pendulum. The dynamic equivalence is not only based on inertia, but involves concepts from the theory of curvature kinematics.The numerical results, obtained by means of multibody dynamics simulations, confirm the reliability of the procedure in terms of rotor torsional vibrations suppression. The methodology herein presented could be extended to cycloidal and epicycloidal vibration absorbers.

Morphology and Behavior of Gametes and Zoospores from the Plant-Parasitic Green Algae, Cephaleuros (Chlorophyta, Ulvophyceae)1

Plant–parasitic green algae in the genus Cephaleuros infect leaves, twigs and fruits of numerous host plants worldwide. The reproductive structures of Cephaleuros are important in the infection process. The goal of this study was to determine the in vitro morphology and behavior of the zoospores and gametes of five Cephaleuros species: Cephaleuros karstenii, C. pilosa, C. solutus, C. virescens and Cephaleuros sp. Microscopic observations revealed that zoospores were ellipsoidal, rod-shaped, or spherical with four flagella. Gametes were spherical in shape with two flagella. Zoospores were released from all five Cephaleuros species, but gametes were released only by C. karstenii, C. solutus and Cephaleuros sp. After their release from gametangia, gametes swarmed in a water drop in irregular and circular motions until the resting stage; some gametes attached to each other, and others burst. Zoospores were released from papilla-pores located at the base of zoosporangia and swarmed in a water drop in irregular and circular motions. Some zoospores germinated and others burst, similar to the gametes. In this study, germinated zoospores formed germ tubes, and filaments containing carotenoid pigment, and then died without forming thalli.

Effects of age-related breathing characteristics on the performance of four-dimensional magnetic resonance imaging reconstructed by prospective gating for radiation therapy planning.

Background and purposeFour-dimensional magnetic resonance imaging (4D MRI) has advanced recently by incorporating prospective gating, but its performance on pediatric populations has not been investigated. This study aimed to determine the age-related performance of prospective gating, as compared with retrospective sorting.Materials and methodsProspectively gated 4D MRI scans were acquired on a motion phantom driven by real respiratory waveforms obtained from 23 pediatric and young adult patients (aged 5–24 years). The correlations between patient-specific breathing characteristics and the performance of 4D MRI were comparatively evaluated against retrospective sorting for the same scan time. For six patients who underwent both 4D MRI and 4D CT, the internal target volumes (ITVs) determined by the two modalities were compared.ResultsLonger scan time and greater sorting error were most highly correlated (P < 0.001) with breathing irregularity and extent of diaphragm motion, but age was not a strong covariate because of interindividual variation. Prospective gating was more accurate than retrospective sorting except for those patients with severe breathing irregularity (peak-to-peak coefficient of variation >30%). The ITVs of 4D MRI and 4D CT were comparable (Dice similarity: >90%) unless the breathing characteristics changed between the two imaging sessions.ConclusionsFor most patients analyzed in this study, prospective gating provided more accurate 4D MRI (95th percentile of deviation: <1.5 mm) than did retrospective sorting within a clinically feasible scan time (median: 5.9 min). The 4D MRI tended to take longer and to give larger sorting errors with deeper and irregular breathers.

An in vitro study for the dosimetric and radiobiological validation of respiratory gating in conventional and hypofractionated radiotherapy of the lung: effect of dose, dose rate, and breathing pattern

Stereotactic body radiotherapy (SBRT) of the lung has become a standard of care for early-stage inoperable non-small cell lung cancer (NSCLC). A common strategy to manage respiratory motion is gating, which inevitably results in an increase in treatment time, especially in irregularly-breathing patients. Flattening-filter free (FFF) beams allow for delivery of the treatment at a higher dose rate, therefore counteracting the lengthened treatment time due to frequent interruption of the beam during gated radiotherapy. In this study, we perform our in vitro evaluation of the dosimetric and radiobiological effect of gated lung SBRT with simultaneous integrated boost (SIB) using both flattened and FFF beams. A moving thorax-shaped phantom with inserts and applicators was used for simulation, planning, gated treatment delivery measurements and in vitro tests. The effects of gating window, dose rate, and breathing pattern were evaluated. Planned doses represented a typical conventional fractionation, 200 cGy per fraction with SIB to 240 cGy, flattened beam only, and SBRT, 800 cGy with SIB to 900 cGy, flattened and FFF beams. Ideal, as well as regular and irregular patient-specific breathing patterns with and without gating were used. A survival assay for lung adenocarcinoma A549 cell line was performed. Delivered dose was within 6% for locations planned to receive 200 and 800 cGy and within 4% for SIB locations. Time between first beam-on and last beam-off varied from approximately 1.5 min for conventional fractionation, 200/240 cGy, to 10.5 min for gated SBRT, 800/900 cGy doses, flattened beam and irregular breathing motion pattern. With FFF beams dose delivery time was shorter by a factor of 2–3, depending on the gating window and breathing pattern. We have found that, for the most part, survival depended on dose and not on dose rate, gating window, or breathing regularity.

A Kalman-Based Approach With EM Optimization for Respiratory Motion Modeling in Medical Imaging

Respiratory motion degrades quantitative and qualitative analysis of medical images. Estimation and, hence, correction of motion commonly uses static correspondence models between an external surrogate signal and internal motion. This paper presents a patient specific respiratory motion model with the ability to adapt in the presence of irregular motion via a Kalman filter with expectation maximization for parameter estimation. The adaptive approach introduces generalizability allowing the model to account for a broader variety of motion. This may be required in the presence of irregular breathing and with different sensors monitoring the external surrogate signal. The motion model framework utilizing an adaptive Kalman filter approach is tested on dynamic magnetic resonance imaging data of nine volunteers and compared to a state-of-the-art static total least squares approach. Results demonstrate the framework is capable of reducing motion to the order of ${p} ) more effective in the presence of irregular motion, assessed using the ${F}$ -test for model comparison. Utilizing the total sum of squares of estimated vector field error from the calculated ground truth, we observe approximately a fifty percent reduction in root mean square error and thirty percent reduction in standard deviation utilizing the Kalman model (EKF) in comparison to a static counterpart.

The irregular breathing effect on target volume and coverage for lung stereotactic body radiotherapy.

The major challenge in treating a mobile target is obtaining the temporal and spatial information imaging and treatment details. This phantom study quantitatively evaluates the geometric and dosimetric effects of various treatment techniques under different respiratory patterns. The regular motion model was a sinusoidal waveform with a longitudinal range of ±1.5 cm and a period of 4 sec, while irregular motion models were generated by extracting signals from clinical cases. Helical CT for a static target and 4D CT with retrospective sorting were acquired. Phase bin, maximum, and average intensity projection (MIP and AIP) CT datasets were reconstructed. RapidArc and IMRT plans were generated on static and moving target CT datasets with different motion patterns using the phase‐based gating and nongating treatment. Dose measurements were performed using EBT3 films. Dose profile and gamma analysis (±3%/1 mm criteria) were used for dose comparisons. For the irregular motions, internal target volume variations between AIP and MIP datasets (AIP/MIP) had slight differences (−6.2% to −7.7%) for gated plans, and larger differences (−12.3% to −15.2%) for nongated plans. Dosimetric measurements showed a high gamma passing rate (>98.5%) for the static plan in the target region, while the AIP and MIP gated plans had average passing rates of 92.2% ± 5.7% and 85.8% ± 9.5%, respectively. Nongated plans had significantly lower and deviated passing rates, while the AIP and MIP plans had passing rates of 43.6% ± 22.2% and 66.7% ± 28.2%, respectively (p < 0.05). Lung stereotactic body radiotherapy treatment delivered with the gated technique did not compromise the gross tumor volumes coverage, and was insensitive to the breathing irregularities and plan techniques. Adequate margins should be accounted to cover the mis‐gating effect when using the phase‐based gating under irregular motion.