Download or read book Acquisition and Processing Techniques for Image Based Prospective Motion Correction in Magnetic Resonance Imaging written by Daniel Christopher Hoinkiss and published by . This book was released on 2018 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Motion Correction in MR written by Andre van der Kouwe and published by Academic Press. This book was released on 2022-10-28 with total page 622 pages. Available in PDF, EPUB and Kindle. Book excerpt: Motion Correction in MR: Correction of Position, Motion, and Dynamic Changes, Volume Eight provides a comprehensive survey of the state-of-the-art in motion detection and correction in magnetic resonance imaging and magnetic resonance spectroscopy. The book describes the problem of correctly and consistently identifying and positioning the organ of interest and tracking it throughout the scan. The basic principles of how image artefacts arise because of position changes during scanning are described, along with retrospective and prospective techniques for eliminating these artefacts, including classical approaches and methods using machine learning. Internal navigator-based approaches as well as external systems for estimating motion are also presented, along with practical applications in each organ system and each MR modality covered. This book provides a technical basis for physicists and engineers to develop motion correction methods, giving guidance to technologists and radiologists for incorporating these methods in patient examinations. Provides approaches for correcting scans prospectively and retrospectively Shows how motion and secondary effects such as field changes manifest in MR scans as artifacts and subtle biases in quantitative research Gives methods for measuring motion and associated field changes, quantifying motion and judging the accuracy of the motion and field estimates

Download or read book Detection and Correction of Patient Motion in Magnetic Resonance Imaging written by Murat Aksoy and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Due to the sequential nature of magnetic resonance imaging (MRI) data acquisition, correction of image artifacts originating from involuntary patient motion is essential for reliable diagnostic quality. Especially during MRI scans of certain patient populations such as children, elderly or patients with certain medical conditions (e.g. stroke, Parkinson's), motion correction methods must be incorporated into the MR imaging protocol for adequate image quality. With increased demands for higher resolution or time-resolved examinations (e.g. functional MRI), examination times also increase and even willing patients might have trouble staying still during the course of the examination. The first part of this thesis provides a method for retrospective correction of head motion artifacts using a multi-shot spiral-in \ & out readout and parallel-imaging based iterative image reconstruction. The spiral-in part provided a low resolution image that was used for measurement of head motion. Due to rotational motion, locally undersampled areas appear in MR acquisition space (i.e., k-space), which violate the Nyquist theorem and cause artifacts even after motion correction. These artifacts were addressed through the data redundancy provided by multiple receiver channels that is present in modern receiver coils and an iterative conjugate-gradient based reconstruction. This method was then applied to diffusion tensor imaging (DTI) with multi-shot readout. Since DTI uses directional gradients to encode diffusion, rotational motion causes the image contrast to change, and it becomes incorrect to combine data with varying diffusion encodings on them. To address this issue, a non-linear conjugate gradient based reconstruction is presented and it is shown that this method provided more accurate description of white matter pathways compared to traditional methods. In the second part of this thesis, a prospective motion correction system using an optical tracking device is presented. Such systems are preferable compared to retrospective navigator-based methods due to various reasons, such as ability to perform motion correction independent of the MR data acquisition and immunity to spin history effects. The system proposed used a single camera mounted on the head coil and a self-encoded checkerboard marker mounted on the patient's forehead. Results on structural and diffusion imaging revealed that prospective motion correction outperforms retrospective navigator-based schemes. In the last part of the thesis, entropy-based retrospective autofocusing was used in combination with motion data obtained from prospective tracking to remove residual motion artifacts in the images. This method was especially useful for removing errors caused by inaccurate cross-calibration between the scanner and camera frame-of-references. It was also shown that prospective tracking can be the enabling technology for autofocusing in 3D acquisitions.

Download or read book Magnetic Resonance Image Reconstruction written by Mehmet Akcakaya and published by Academic Press. This book was released on 2022-11-04 with total page 518 pages. Available in PDF, EPUB and Kindle. Book excerpt: Magnetic Resonance Image Reconstruction: Theory, Methods and Applications presents the fundamental concepts of MR image reconstruction, including its formulation as an inverse problem, as well as the most common models and optimization methods for reconstructing MR images. The book discusses approaches for specific applications such as non-Cartesian imaging, under sampled reconstruction, motion correction, dynamic imaging and quantitative MRI. This unique resource is suitable for physicists, engineers, technologists and clinicians with an interest in medical image reconstruction and MRI. Explains the underlying principles of MRI reconstruction, along with the latest research“/li> Gives example codes for some of the methods presented Includes updates on the latest developments, including compressed sensing, tensor-based reconstruction and machine learning based reconstruction

Download or read book Comprehensive Head Motion Correction For Functional Magnetic Resonance Imaging written by Zahra Faraji-Dana and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Head motion artifacts are major confounds that limit use of functional magnetic resonance imaging (fMRI) in neuroscience research and clinical settings. Prospective motion correction is a promising candidate solution for head motion in fMRI that ideally allows the image plane to remain fixed with respect to the moving head (i.e., in the moving reference frame). Prospective motion correction has been shown to correct successfully for rigid body movement artifacts, but residual geometric distortion due to dynamic magnetic field nonuniformities and dynamic changes in receiver coil sensitivity profiles in the moving reference frame still remain a problem. This thesis focuses on three objectives. First, I investigated and corrected for the influence of respiratory effects on the performance of dynamic geometric correction using Phase Labeling for Additional Coordinate Encoding (PLACE). It was demonstrated that PLACE combined with the dynamic off-resonance in k-space (DORK) method, and temporal averaging substantially improved fMRI data quality in comparison to the results obtained by standard processing and static geometric distortion correction. Second, I verified that appreciable signal artifacts occur due to coil sensitivity changes in fMRI maps in presence of overt head motion with prospective motion correction using Prospective Acquisition CorrEction (PACE) technique [1]. Sensitivity map compensations were shown to suppress these artifacts and provide improved fMRI results Third, I studied signal artifacts resulted from the head motion between the coil sensitivity map measurement (i.e., the calibration step) and data acquisition for fMRI with parallel-imaging reconstruction methods using two parallel imaging schemes: sensitivity encoding (SENSE) and generalized autocalibrating partially parallel acquisitions (GRAPPA) with acceleration factors 2 and 4. Coil sensitivity map compensations were shown to improve fMRI results obtained with PACE in the presence of overt head motion compared to those obtained with no overt head motion. Overall, prospective motion correction, integrated dynamic geometric distortion correction, and coil sensitivity map correction present an appealing compound approach for suppressing rigid and non-rigid motion artifacts during fMRI. This thesis has developed robust and comprehensive head motion correction strategies that ultimately will expand the patient populations for which fMRI can be performed robustly.

Download or read book Pitfalls in Diagnostic Radiology written by Wilfred C. G. Peh and published by Springer. This book was released on 2014-11-10 with total page 545 pages. Available in PDF, EPUB and Kindle. Book excerpt: The practice of diagnostic radiology has become increasingly complex, with the use of numerous imaging modalities and division into many subspecialty areas. It is becoming ever more difficult for subspecialist radiologists, general radiologists, and residents to keep up with the advances that are occurring year on year, and this is particularly true for less familiar topics. Failure to appreciate imaging pitfalls often leads to diagnostic error and misinterpretation, and potential medicolegal problems. This textbook, written by experts from reputable centers across the world, systematically and comprehensively highlights the pitfalls that may occur in diagnostic radiology. Both pitfalls specific to different modalities and techniques and those specific to particular organ systems are described with the help of numerous high-quality illustrations. Recognition of these pitfalls is crucial in helping the practicing radiologist to achieve a more accurate diagnosis.

Download or read book Compressed Sensing Magnetic Resonance Image Reconstruction Algorithms written by Bhabesh Deka and published by Springer. This book was released on 2018-12-29 with total page 122 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents a comprehensive review of the recent developments in fast L1-norm regularization-based compressed sensing (CS) magnetic resonance image reconstruction algorithms. Compressed sensing magnetic resonance imaging (CS-MRI) is able to reduce the scan time of MRI considerably as it is possible to reconstruct MR images from only a few measurements in the k-space; far below the requirements of the Nyquist sampling rate. L1-norm-based regularization problems can be solved efficiently using the state-of-the-art convex optimization techniques, which in general outperform the greedy techniques in terms of quality of reconstructions. Recently, fast convex optimization based reconstruction algorithms have been developed which are also able to achieve the benchmarks for the use of CS-MRI in clinical practice. This book enables graduate students, researchers, and medical practitioners working in the field of medical image processing, particularly in MRI to understand the need for the CS in MRI, and thereby how it could revolutionize the soft tissue imaging to benefit healthcare technology without making major changes in the existing scanner hardware. It would be particularly useful for researchers who have just entered into the exciting field of CS-MRI and would like to quickly go through the developments to date without diving into the detailed mathematical analysis. Finally, it also discusses recent trends and future research directions for implementation of CS-MRI in clinical practice, particularly in Bio- and Neuro-informatics applications.

Download or read book Motion Artifact Reduction in Steady state Magnetic Resonance Imaging written by Richard Reeve Ingle and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Magnetic resonance imaging (MRI) is a powerful medical imaging modality that offers excellent soft-tissue contrast and numerous contrast-generation mechanisms. However, due to the relatively low signal-to-noise ratio (SNR) of MRI, many volumetric and high-resolution imaging techniques require long acquisition times yielding an increased sensitivity to motion. In many cardiac MRI applications, one of the most significant challenges is the reduction of motion artifacts caused by cardiac and respiratory motion. In these applications, a combination of SNR-efficient balanced steady-state free precession (bSSFP) pulse sequences, high-temporal-resolution motion tracking acquisitions, and retrospective motion correction algorithms are commonly employed to mitigate motion artifacts. Despite recent advances in steady-state pulse sequence development, navigator motion tracking acquisitions, and motion correction algorithms, motion artifact reduction continues to be a significant challenge for many cardiac MRI applications. A novel class of perturbed steady-state free precession (SSFP) pulse sequences is developed and analyzed, yielding new forms of steady-state image contrast. These sequences utilize alternating perturbations of sequence parameters such as the repetition time (TR) and flip angle to produce oscillating steady-state frequency responses. Large oscillations of the signal magnitude and phase occur at specific off-resonant frequencies, and the combination of these signals can yield spectrally selective image contrast. Applications are demonstrated for retrospective motion correction using cardiac fat navigator acquisitions in free-breathing whole-heart cardiac MRI and for positive-contrast imaging of superparamagnetic iron-oxide nanoparticles. The bSSFP pulse sequence is widely used in cardiac imaging due to its high signal per unit time and excellent blood-myocardial contrast. A drawback of this pulse sequence is the generation of bright signal from fat, which can lead to unwanted image artifacts. Alternating repetition time (ATR) SSFP is a recently developed sequence that generates fat-suppressed steady-state contrast, but it requires the addition of an unused time interval every repetition, making it less time efficient than bSSFP. A small modification to the ATR pulse sequence is proposed to enable the acquisition of a one-dimensional self-gating signal during this unused time interval. The self-gating signals are used for retrospective cardiac triggering in breath-held cardiac cine imaging, and the proposed sequence is evaluated in volunteer and patient populations. The resulting ECG-free self-gated images have no statistically significant differences compared with conventional ECG-gated images. The proposed sequence also yields robust suppression of epicardial fat compared with standard bSSFP cardiac cine imaging. In coronary MR angiography (CMRA), high-resolution, whole-heart acquisitions are typically required for visualization of the relatively small coronary vasculature. These acquisitions require long scan times that are carried out during free breathing, which can lead to severe ghosting and blurring artifacts without motion compensation. A nonrigid retrospective motion correction technique is proposed for motion artifact reduction in image-navigated CMRA. The technique reconstructs a bank of motion-compensated CMRA images using many candidate motion estimates derived from navigator images acquired throughout the scan. A metric-based autofocusing approach is used to automatically generate a final nonrigid-motion-corrected image from this bank of images. The proposed technique is evaluated in volunteer and patient studies, leading to improvements in vessel sharpness and image quality compared with rigid-body translational motion correction. These new steady-state pulse sequences, motion tracking acquisitions, and nonrigid reconstruction techniques address several of the challenges to cardiac MRI, enabling the reduction of motion artifacts and improvement of image quality.

Download or read book Data Acquisition and Processing Techniques in Magnetic Resonance Spectroscopic Imaging written by Shantanu Sarkar and published by . This book was released on 2002 with total page 262 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Motion Correction in Orbital Imaging Using MRI Compatible Eye Tracker written by Anita Dushyanth and published by . This book was released on 2014 with total page 98 pages. Available in PDF, EPUB and Kindle. Book excerpt: The body motion of patients during magnetic resonance imaging (MRI) causes significant artifacts in the reconstructed image. Artifacts are manifested as a motion induced blur and ghost repetitions of the moving structures, which obscure vital anatomical and pathological detail. The techniques that have been proposed for suppressing motion artifacts fall into two major categories. Realtime techniques that attempt to prevent the motion from corrupting the data by restricting the data acquisition times or motion of the patients, and post-processing techniques that use information embedded in the corrupted data to restore the image. The post-processing techniques usually demand an appropriate model of the motion that requires the parameters be determined in order to invert the data degradation process. However, motion is manifested differently depending on the time and duration it occurred during Magnetic Resonance (MR) data acquisition. Estimating motion parameters from such cases are heavily based on assumptions and the reconstructed image is compromised on either contrast or resolution. A major challenge in high resolution MR imaging of the orbit (eyeball and associated tissues in the eye socket) is image degradation by artifacts resulting from eye movements and eyelid blinks. In this thesis a novel method for motion correction has been developed by incorporating an optical sensor that detects these eye movements during MR scan acquisition without generating signal artifacts, and which is not affected by either the strong static magnetic field or the pulsed field gradients. Detection of the subjects eye movements and blinks is essential for determining the exact times during the MR scan when each such movement occurred. This thesis presents a method for refining orbital MRI techniques to compensate for the effects of blinking and fixation instability. It employs an eye tracker system to track eye/eyelid movements in the MRI studies of strabismus in humans that is based on infrared (IR) light reflection. It incorporates custom-fabricated optical fiber probes that illuminate the eye with low intensity infrared light, while eye/eyelid movements are detected by changes in ocular surface reflectance transmitted by another optical fiber cable coupled to a photodiode. Additionally, there is another light source that serves as a visible point target for ocular fixation during MRI scanning. The volunteer's eye movements are recorded simultaneously while the orbit is scanned using MRI. The output signal from the detector is amplified and synchronized in time with the MR acquired data. Image data corrupted by motion is flagged so that the affected data can be removed during image reconstruction. The purpose of this experiment is to outline experimental protocols for acquiring and correcting the above mentioned images in high quality, discuss these protocols from a wide range of perspectives, and finally present some observations on pilot data from volunteer subjects as well as patient with pathology. The MRI methodology developed was able to suppress motion artifacts considerably to provide interpretable MRI images.

Download or read book Application Tailored Accelerated Magnetic Resonance Imaging Methods written by Ziwu Zhou and published by . This book was released on 2018 with total page 180 pages. Available in PDF, EPUB and Kindle. Book excerpt: Magnetic resonance imaging (MRI) is a powerful diagnostic medical imaging technique that provides very high spatial resolution. By manipulating the signal evolution through careful imaging sequence design, MRI can generate a wide range of soft-tissue contrast unique to individual application. However, imaging speed remains an issue for many applications. In order to increase scan output without compromising the image quality, the data acquisition and image reconstruction methods need to be designed to fit each application to achieve maximum efficiency. This dissertation concerns several application-tailored accelerated imaging methods through improved sequence design, efficient k-space traverse, as well as tailored image reconstruction algorithm, all together aiming to exploit the full potential of data acquisition and image reconstruction in each application. The first application is ferumoxtyol-enhanced 4D multi-phase cardiovascular MRI on pediatric patients with congenital heart disease. By taking advantage of the high signal-to-noise ratio (SNR) results from contrast enhancement, we introduced two methods to improve the scan efficiency with maintained clinical utility: one with reduced scan time and one with improved temporal resolution. The first method used prospective Poisson-disc under-sampling in combination with graphics processing unit accelerated parallel imaging and compressed sensing combined reconstruction algorithm to reduce scan time by approximately 50% while maintaining highly comparable image quality to un-accelerated acquisition in a clinically practical reconstruction time. The second method utilized a motion weighted reconstruction technique to increase temporal resolution of acquired data, and thus permits improved cardiac functional assessment. Compared with existing acceleration method, the proposed method has nearly three times lower computation burden and six times faster reconstruction speed, all with equal image quality. The second application is noncontrast-enhanced 4D intracranial MR angiography with arterial spin labeling (ASL). Considering the inherently low SNR of ASL signal, we proposed to sample k-space with the efficient golden-angle stack-of-stars trajectory and reconstruct images using compressed sensing with magnitude subtraction as regularization. The acquisition and reconstruction strategy in combination produces images with detailed vascular structures and clean background. At the same time, it allows a reduced temporal blurring delineation of the fine distal arteries when compared with the conventional k-space weighted image contrast (KWIC) reconstruction. Stands upon on this, we further developed an improved stack-of-stars radial sampling strategy for reducing streaking artifacts in general volumetric MRI. By rotating the radial spokes in a golden angle manner along the partition-encoding direction, the aliasing pattern due to under-sampling is modified, resulting in improved image quality for gridding and more advanced reconstruction methods. The third application is low-latency real-time imaging. To achieve sufficient frame rate, real-time MRI typically requires significant k-space under-sampling to accelerate the data acquisition. At the same time, many real-time application, such as interventional MRI, requires user interaction or decision making based on image feedback. Therefore, low-latency on-the-fly reconstruction is highly desirable. We proposed a parallel imaging and convolutional neural network combined image reconstruction framework for low-latency and high quality reconstruction. This is achieved by compacting gradient descent steps resolved from conventional parallel imaging reconstruction as network layers and interleaved with convolutional layers in a general convolutional neural network. Once all parameters of the network are determined during the off-line training process, it can be applied to unseen data with less than 100ms reconstruction time per frame, while more than 1s is usually needed for conventional parallel imaging and compressed sensing combined reconstruction.

Download or read book Combining Data Acquisition and Post processing Techniques for Magnetic Resonance Imaging of Moving Objects written by Kate McLeish and published by . This book was released on 2003 with total page 422 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Advanced Motion Corrected Reconstruction Techniques for Magnetic Resonance Imaging written by Gastão Cruz and published by . This book was released on 2016 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The proposed method reduced scan times by 2.6x when compared with the gated acquisition while maintaining similar image quality. In the second application, the framework is combined with interleaved image navigators to add high temporal resolution motion correction. This method also presented similar coronary lumen quality to the gated, despite a 1.6x reduction in scan time. Additionally, it presented sig- nificantly superior vessel wall quality when compared to translation correction. In the third application, the framework is combined with Parallel Imaging, Compressed Sensing and interleaved image naviga- tors. Initial results indicate the proposed approach produces signifi- cantly superior water and fat images than translation correction.

Download or read book Motion Correction Techniques for Three dimensional Magnetic Resonance Imaging Acquired with the Elliptical Centric View Order Or the Shells Trajectory written by Yunhong Shu and published by . This book was released on 2006 with total page 338 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Motion Correction and Reduction Techniques in Magnetic Resonance Imaging written by Hope Waggener Korin and published by . This book was released on 1991 with total page 334 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Motion Correction Techniques for Magnetic Resonance Imaging written by Edward Brian Welch and published by . This book was released on 2003 with total page 318 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Reduced encoding Dynamic Imaging written by Jill Marie Hanson and published by . This book was released on 1997 with total page 194 pages. Available in PDF, EPUB and Kindle. Book excerpt: This research addresses the problem of acquiring a time series of magnetic resonance images with both high spatial and temporal resolutions. Specifically, we systematically investigate the advantages and limitations of reduced-encoding imaging using a priori constraints. This study reveals that if the available a priori information is a reference image, direct use of this information to 'optimize' data acquisition using the existing wavelet transform or singular value decomposition schemes can undermine the capability to detect new image features. However, proper incorporation of the a priori information in the image reconstruction step can significantly reduce the resolution loss associated with reduced-encoding. For Fourier encoded data, we have shown that the Generalized-Series (GS) model is an effective mathematical framework for carrying out the constrained reconstruction step. Several techniques are proposed in this dissertation to improve the basis functions of the GS model by introducing dynamic information. The two reference reduced-encoding imaging by generalized-series reconstruction (TRIGR) method suppresses background information through the use of a second high resolution reference image. A second technique injects information from the dynamic data into the GS basis functions, as opposed to deriving them solely from the reference information. These techniques allow the GS basis functions to more accurately represent the areas of dynamic change. Finally, motion that occurs between the acquisition of the reference and dynamic data sets can render the reference information useless as a constraint for image reconstruction. A motion compensation method is proposed which uses a similarity norm to accurately detect the motion in spite of contrast changes and the low resolution nature of the dynamic data.