Motion Compensation Approach Research Articles

The effect of IMU inaccuracies on airborne SAR imaging

When using motion compensation approaches based on the measurement of motion sensors, the residual uncompensated motion errors due to measurement instrument inaccuracies contribute to phase errors and hence degrade Synthetic Aperture Radar (SAR) images. This paper presents a model to compute the phase error caused by Inertial Measurement Unit (IMU) measurement inaccuracies. By analyzing SAR motion compensation method and the effect of lever arm, this model derives the contribution of each term of IMU inaccuracies towards the residual uncompensated motion errors and provides a method to calculate each order of the residual phase error. According to the model, computed results of the airborne X-band SAR system with POS AV510 accord closely with the actual image quality.

Iterative motion compensated reconstruction for parallel imaging using an orbital navigator

A new navigator-guided motion-compensated MR image reconstruction for segmented Cartesian imaging using multiple reception coils is presented. In-plane patient motion, comprising translation and rotation, is quantified for each scan segment by an orbital navigator. A robust and accurate approach to extract the motion parameters from the orbital navigator data is presented. The navigator information is used in an efficient iterative image reconstruction algorithm to avoid motion-induced image artifacts. Experiments in phantoms and volunteers using segmented turbo spin echo imaging as an example were performed to show the basic feasibility of this new motion compensation approach. The method can also be applied to other segmented acquisitions such as magnetization-prepared gradient echo imaging or EPI.

Motion Adaptive Compensation Approach for Deinterlacing of Video Sequences

de-interlacing algorithm using adaptive 4-field motion compensation approach is presented. It consists of block- based directional edge interpolation, same- parity 4-field motion detection, 4-field motion estimation and compensation. The intra field methods are reconstructed the frame from the current field information .but this method introduce the edge flicker problems and jitter effect. The inter field methods are depends on the previous and future fields for reconstruction of the current frame. This method introduces feathering effect. The edges are sharper when the directional edge interpolation is adopted and jitter effect and the feathering effect eliminated. The motion adaptive deinterlacing scheme is taking the advantages of both intra and inters field methods. First it finds the motion by using motion detection scheme if the field contain motion apply intra field interpolation method if the field contain stationary objects apply the inter field interpolation method. The 3-field motion detection can not detect the fast motion areas from field to field. The same parity 4-field motion adaptive deinterlacing and the 4-field motion compensation detect the static areas and fast motion by four reference fields. The Compensation recovers the interlaced videos to the progressive ones but the feathering effect is not recovered in this method. The adaptive 4-field motion compensation method removes the feathering effect along with detecting fast motion areas by using four reference fields. Experimental results show that the peak signal-to-noise ratio of our adaptive 4-field motion compensation deinterlacing algorithm is 4 to 6 dB higher than that of 3-field motion adaptive deinterlacing and 2 to 3 dB higher than 4-field motion compensation deinterlacing and attain the best quality of video.

Visual Tracking of a Hand–Eye Robot for a Moving Target Object with Multiple Feature Points: Translational Motion Compensation Approach

In this paper, we propose a visual tracking control method of a hand–eye robot for a moving target object with multiple feature points. The hand–eye robot is composed of a 3-d.o.f. planar manipulator and a single charge-coupled-device camera that is mounted on the manipulator's end-effector. The control objective is to keep all feature points of the target object around their desired coordinates on the image plane. In many conventional visual servo methods, it is assumed that the target object is static. Consequently, the visual tracking error arises in the case of a moving target object. We have already proposed a visual tracking control system that takes into consideration the target object motion. This method can reduce the visual tracking error, but can only deal with a single feature point. Therefore, this paper extends such a visual tracking control method to multiple feature points. The effectiveness of our control method is evaluated experimentally.

Respiratory motion compensation by model-based catheter tracking during EP procedures

In many cases, radio-frequency catheter ablation of the pulmonary veins attached to the left atrium still involves fluoroscopic image guidance. Two-dimensional X-ray navigation may also take advantage of overlay images derived from static pre-operative 3D volumetric data to add anatomical details otherwise not visible under X-ray. Unfortunately, respiratory motion may impair the utility of static overlay images for catheter navigation. We developed a novel approach for image-based 3D motion estimation and compensation as a solution to this problem. It is based on 3D catheter tracking which, in turn, relies on 2D/3D registration. To this end, a bi-plane C-arm system is used to take X-ray images of a special circumferential mapping catheter from two directions. In the first step of the method, a 3D model of the device is reconstructed. Three-dimensional respiratory motion at the site of ablation is then estimated by tracking the reconstructed catheter model in 3D based on bi-plane fluoroscopy. Phantom data and clinical data were used to assess model-based catheter tracking. Our phantom experiments yielded an average 2D tracking error of 1.4mm and an average 3D tracking error of 1.1mm. Our evaluation of clinical data sets comprised 469 bi-plane fluoroscopy frames (938 monoplane fluoroscopy frames). We observed an average 2D tracking error of 1.0 + or - 0.4mm and an average 3D tracking error of 0.8 + or - 0.5mm. These results demonstrate that model-based motion-compensation based on 2D/3D registration is both feasible and accurate.

A new approach of motion compensation for synthetic wideband radar under multitarget environment

This paper studies target velocity estimation for stepped frequency radar with up-down linear frequency coding under multi-target environment. It is shown that target matching is needed in the estimation of target velocity when targets have unequal velocities. Based on monopulse radar scheme, this target matching process is extended to angular domain, and an angle matching method of velocity measurement is proposed to resolve different velocities of multi-target. The method is analyzed from different aspects in terms of matching probability and CRLB of velocity estimation. Simulation results demonstrate that it is effective and feasible.

Compensation of breathing motion artifacts for MRI with continuously moving table

Breathing motion is one of the main sources of artifacts in MRI acquisitions that can severely impair diagnosis. In MRI with continuously moving table, the application of common motion compensation approaches such as breath holding or the synchronization of the measurement with the breathing motion can be problematic. In this study, a technique for the reduction of breathing-motion artifacts for MRI with continuously moving table is presented, which reconstructs motion-consistent volumes from data acquired during free breathing. Axial images are acquired rapidly compared to the period of the breathing motion and consistently combined using a combination of rigid and nonrigid slice-to-volume registration. This new technique is compared to a previously reported artifact reduction method for MRI with continuously moving table that is based on the same acquisition scheme. While the latter method only suppresses ghosting artifacts, the new technique is shown to additionally reduce blurring, misregistrations, and signal cancellations in the reconstructed images.

An Improved Topography-Dependent Motion Compensation Approach for Airborne Repeat-Pass Interferometric SAR Systems

In this paper, the precise topography-dependent motion compensation for repeat-pass InSAR is studied. The effects of the residual motion errors caused by the flat surface assumption and center-beam approximation are analyzed, which shows the necessity of performing a precise topography-dependent motion compensation for the repeat-pass InSAR systems. The precision requirement for the external DEM data is analyzed to show the feasibility of deriving precise DEM data by motion compensation based on rough DEM data. An improved approach is presented according to the deficiencies of the existing topography-dependent motion compensation approaches. It can adjust the parameters according to the conditions of trajectory deviations and topography variations, so it has the advantage of performing the precise motion compensation efficiently. Finally, the processing results of the X-band airborne repeat-pass interferometric SAR data confirm its validity and superiority in precision and efficiency compared to the original algorithms.

Experimental results on ISAR imaging with stepped-frequency waveforms

A simple and successful processing for the bandwidth synthetic of stepped-frequency waveforms (SFWs) is presented. The high range resolution is obtained by combining the sub-pulses of SFWs in the frequency domain. The overlapping bandwidth of the two adjacent sub-pulses is used to estimate phase errors. Also the usual motion compensation approach is avoided if the band coherent processing is used. Experimental results of the ship target are shown.

Motion compensation for wide beam SAR based on frequency division

Aperture-dependent motion compensation is important for wide beam Synthetic Aperture Radar (SAR) data processing. This paper studies a wide beam motion compensation algorithm based on frequency division. It takes blocks along azimuth dimension in frequency domain and applies angle-variant motion compensation in time domain. With this frequency division based motion compensation approach, the effects of aperture-dependent residual phase errors are corrected precisely. The rationale and procedure of this algorithm are introduced in detail. Point targets and images of a P-band airborne SAR with motion errors are simulated to validate this algorithm. Compared with the wide beam motion compensation algorithms based on time division, the proposed algorithm has better performance, especially in terms of high-frequency motion errors.

TU‐C‐342‐01: Image Guidance During Minimally Invasive Cardiac Interventions : Beyond Fluoroscopy

Minimally invasive cardiac procedures using endovascular access have enabled treatment of patients that previously would have required open‐heart surgery. Such procedures are typically carried out in the interventional suite, with x‐ray fluoroscopy used to guide the placement of a catheter, followed by a phase of the procedure in which x‐ray fluoroscopy provides little to no information on the treatment. C‐arm CT has been under development since the early 90's, but has now entered a new phase as the ability to visualize soft tissue and low‐contrast lesions improves. By generating 3D images utilizing the x‐ray system in the interventional suite, the error prone and time‐consuming spatio‐temporal registration with prior CT or MRI exams can be avoided. However, C‐arm CT imaging in the presence of cardiac motion remains a challenge due to the slow rotation speed of the gantry, and the slow readout rates of the flat‐panel detectors. Three main data acquisition approaches to circumvent these limitations will be discussed: multi‐sweep retrospective ECG gating for myocardial visualization, single‐ or double‐sweep with volume image fusion for left atrium and pulmonary vein visualization and single‐sweep with retrospective gating for coronary artery visualization. Approaches to improve image quality, both hardware and software, such as optimized acquisition timing, motion compensation approaches and algorithms for non‐idealities such as x‐ray scatter, detector lag, limited field‐of‐view or angular coverage, data insufficiency and noise will be presented. With these developments the ultimate goal is to accomplish faster and more accurate catheter based interventions with an equivalent success rate as surgical procedures (80–90%). The C‐arm CT technology described here could eventually impact many minimally invasive procedures such as RF ablation for atrial fibrillation and coronary stenting, and also future procedures as they become available, such as endocardial injection of stem cells for treatment of myocardial infarction.Educational Objectives:1. Learn how 3D cardiac imaging is done in the interventional suite: acquisition protocols, injection protocols, challenges and solutions.2. Learn how image quality of 3D cardiac images can be improved using hardware and algorithm approaches.

Lossless and near-lossless digital angiography coding using a two-stage motion compensation approach

This paper presents a two-stage motion compensation coding scheme for image sequences in hemodynamics. The first stage of the proposed method implements motion compensation, and the second stage corrects local pixel intensity distortions with a context adaptive linear predictor. The proposed method is robust to the local intensity distortions and the noise that often degrades these image sequences, providing lossless and near-lossless quality. Our experiments with lossless compression of 12 bits/pixel studies indicate that, potentially, our approach can perform 3.8%, 2% and 1.6% better than JPEG-2000, JPEG-LS and the method proposed by Scharcanski [1], respectively. The performance tends to improve for near-lossless compression. Therefore, this work presents experimental evidence that for coding image sequences in hemodynamics, an adequate motion compensation scheme can be more efficient than the still-image coding methods often used nowadays.

Motion compensation in ISAR imaging using the registration–restoration–fusion approach

The distortion in the inverse synthetic aperture radar (ISAR) image of a target is a result of small time-varying perturbed motion experienced by the target during the image integration period and is attributed to a phase modulation effect of the radar return from the target. Large distortion in ISAR images of a moving target has been investigated and demonstrated under controlled experiments and simulation. Results from the analysis suggest that severe distortion is attributed to the phase modulation effect where a time-varying Doppler frequency provides the smearing mechanism. For applications of target identification, the registration–restoration–fusion method has been developed to refocus the distorted ISAR images. This method has been applied to both the experimental and simulated ISAR data. Results demonstrate that the registration–restoration–fusion motion compensation approach can improve the distorted ISAR image better than what can be achieved by conventional Fourier transform methods. This study also adds insight into the distortion mechanisms that affect the ISAR images of a target in motion.

An efficient motion estimation and compensation method for ultrasound synthetic aperture imaging.

This paper describes a method for overcoming motion artifacts in synthetic aperture imaging. The method is based on a computer simulation study on the influence of target motion on synthetic aperture techniques. A region-based motion compensation approach is used in which only the axial motion is estimated and compensated for a given region of interest under the assumption that the whole ROI moves uniformly. The estimated axial motion is calculated with a crosscorrelation method at the point where the focused signal has the maximum energy within the ROI. We also present a method for estimating axial motion using the autocorrelation method that is widely used to estimate average Doppler frequency. Both computer simulations and in vivo experiments show that the proposed crosscorrelation-based method can greatly improve the spatial resolution and SNR of ultrasound imaging by implementing SA techniques for two-way dynamic focusing without motion artifacts. In addition, the autocorrelation-based motion compensation method provides almost the same results as the crosscorrelation-based method, but with a dramatically reduced computational complexity.

Minimum description length criterion and segmentation map coding for region-based video compression

This paper presents a new technique for region-oriented video compression based on the minimization of a minimum description length (MDL) criterion. The proposed scheme is based on a region-based motion compensation approach, in which the displaced frame difference (DFD) is coded together with the segmentation map and the motion parameters. The region-based segmentation is approximated by a polygonal representation which permits us to significantly reduce the segmentation coding cost. The polygonal approximation, which minimizes the MDL criterion, is considered the optimal approximation in terms of compression performance. In this contest, the MDL criterion has been developed and tested for the three following DFD coding techniques: (1) entropy coding of the quantized DFD image; (2) entropy coding of the quantized DFD values obtained after morphological filtering of the DFD image; and (3) DCT-based coding of the DFD image. The experimental results, presented on real video sequences, validate the proposed approach.

Diagnostic ultrasound for two-dimensional temperature mapping in hyperthermia and laser-induced tissue coagulation

Laser-induced tissue heating and coagulation is a common technique in minimally invasive surgery to achieve localized thermal tissue damage. Precision and efficiency of treatment could be improved markedly by noninvasive spatio-temporal temperature monitoring. A method for two-dimensional mapping of tissue temperature as well as tissue structural changes has been investigated in vitro. The algorithms are based on the temperature dependence of speed of sound and a combination of additional acoustical parameters in order to consider the expansion of the heated volume, creation of gas bubbles, and carbonization. An approach for motion compensation, as it is necessary for clinical application, will be described in short.

A scene adaptive hybrid video coding scheme based on the LOT

Conventional standard video coding schemes based on independent coding of nonoverlapping image blocks produce undesirable effects (blocking effect and color bleeding, etc.) at low bit rate. A hybrid coding scheme evolving from the standard MPEG codec that combines lapped orthogonal transform (LOT) and overlapped block motion compensation and quantization approaches based on human visual system sensitivity is proposed to remove the artifacts. The LOT is applied to compress the resulting prediction errors of the overlapped motion compensation. The LOT coefficients are quantized by a dynamic intra/inter scene adaptive quantizer that is designed according to the human visual system and scene analysis to optimize the decoded image quality. This technique involves automatically deriving the most favorable quantizer matrix from the motion and scene analysis of image sequences and scaling the resulting matrix further by considering the buffer status. If a scene change is detected from the motion information, the proposed adaptive quantization can also help solve the difficulty of the buffer controller and maintain the picture quality as constant as possible. Performance of the proposed hybrid coding scheme with scene adaptive quantizer is demonstrated by computer simulations using standard test sequences and compared to that of the conventional MPEG-2 coding schemes. Subjective and objective tests show that image quality is improved considerably and the required bit rate is much less than that of the conventional method. Particularly, the image quality can be kept almost consistent, and the undesirable artifacts are reduced considerably.

Trifocal motion modeling for object-based video compression and manipulation

Following an overview of two-dimensional (2-D) parametric motion models commonly used in video manipulation and compression, we introduce trifocal transfer, which is an image-based scene representation used in computer vision, as a motion compensation method that uses three frames at a time to implicitly capture camera/scene motion and scene depth. Trifocal transfer requires a trifocal tensor that is computed by matching image features across three views and a dense correspondence between two of the three views. We propose approximating the dense correspondence between two of the three views by a parametric model in order to apply the trifocal transfer for object-based video compression and background mosaic generation. Backward, forward, and bidirectional motion compensation methods based on trifocal transfer are presented. The performance of the proposed motion compensation approaches using the trifocal model has been compared with various other compensation methods, such as dense motion, block motion, and global affine transform on several video sequences. Finally, video compression and mosaic synthesis based on the trifocal motion model are implemented within the MPEG-4 Video Verification Model (VM), and the results are compared with those of the standard MPEG-4 video VM. Experimental results show that the trifocal motion model is superior to block and affine models when there is depth variation and camera translation.

Motion Compensation for Synthetic Aperture Radar

A generalized motion compensation approach applicable to all SAR modes, i.e., strip mapping (side-looking or squint), spotlight (or telescope) mapping, and Doppler beam sharpened mapping (DBS), is described. The basic concept is the formation for unit vector ū and the slaving of the real illuminating antenna and the processed synthetic antenna to this unit vector. The amount of motion compensation which is required is developed in terms of transfer curves for the main motion reduction paths, i.e., translational, rotational (lever arm), and real antenna stabilization. The transfer curves are obtained by dividing the expected motion spectrum by the required sensitivity spectrum. The most critical motion reduction path for typical parameters is shown to be the translational path. The lever arm and real antenna stabilization paths are less critical, but must also be implemented.