Reducing motion artifacts in two-dimensional Fourier transform imaging

Haacke, E. Mark; Patrick, John

doi:10.1016/0730-725x(86)91046-5

Cited by 196 publications

(114 citation statements)

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“…The powerful k-space formalism, which was introduced to solve this system of linear differential equations for the cases of signal reception (5) and excitation (6), is based on the time-invariance of the position vector r. Thus, if the voxels are moving, the k-space formalism is no longer valid and image reconstruction via fast Fourier transform (FFT) generally becomes impossible. Only for the special case of interview motion has it been shown that the kspace formalism may be preserved to correct for translation (7) and linear expansion (8). Hence, this paper discusses affine motion in terms of the Bloch equations, which allows for a more coherent description of motion compensation during signal excitation and reception without being restricted to interview motion.…”

Section: Theorymentioning

confidence: 99%

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Prospective correction of affine motion for arbitrary MR sequences on a clinical scanner

Nehrke

Börnert

2005

Magnetic Resonance in Med

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The concept of prospective 3D affine motion correction was generalized, based on the Bloch equations, for signal excitation and sampling using arbitrary MR sequences. The technique was implemented on a clinical MRI scanner for Cartesian, radial, and spiral imaging sequences, as well as for 2D spatially selective RF excitation pulses. A patient-specific motion model steered by real-time navigators was employed to account for the additional degrees of freedom provided by the affine motion model. Different navigator concepts (multiple spatial and temporal navigators, quadratic navigators and other motion sensors) were investigated, with the aim of improving the correlation between navigator information and the motion model. Many MR imaging (MRI) and spectroscopy (MRS) applications suffer from motion artifacts caused by, e.g., respiratory and cardiac motion. Currently employed real-time gating techniques, such as EKG triggering and navigatorbased respiratory gating (1), reduce motion artifacts considerably but result in a strong increase in scan time. Hence, motion-correction techniques, which allow the acquisition of MR data in the presence of motion, are highly desirable. Slice-tracking approaches based on respiratory navigators have been shown to improve image quality in coronary MRA (2). However, due to the simplicity of the underlying 1D translatory motion model, only small gating windows (typically 5 mm) can be applied (3). Recently a patient-specific calibration approach was introduced for coronary MRA that allows the prediction of affine transformation parameters, including 3D translation, rotation, scale, and shear motion, from navigator measurements (4). In addition, a prospective correction of affine motion was proposed. However, the technical complexity of such an approach limited the implementation to prospective correction of 3D translation and 1D expansion for Cartesian imaging sequences. Furthermore, additional offline processing was required, which challenged the practical feasibility of the method in a clinical workflow.In the current work, prospective motion correction is discussed in the framework of the Bloch equations, which conceptually overcomes the restriction to Cartesian imaging sequences. Thus, the approach is generalized to signal excitation and sampling for arbitrary MRI sequences, such as multidimensional excitation pulses and non-Cartesian imaging sequences. Following the theoretical treatment, the technique is fully implemented on a clinical scanner in a sequence-independent manner, which enables the employment of a full 3D affine transformation for all available pulse and imaging sequences, including Cartesian, radial, and spiral scanning, as well as 2D excitation pulses. The results of phantom experiments are presented that prove the technical feasibility of the approach, whereas initial in vivo results demonstrate the potential for coronary MRA and abdominal imaging. THEORYThe principles of affine motion correction may be derived directly from the Bloch equations. The Bloch equati...

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Section: Theorymentioning

confidence: 99%

“…[1] and [2], and [7] and [8] shows that the effect of affine motion may be compensated for prospectively in an MRI experiment by precompensating for the gradient waveforms and (de)modulating the transmitted and received RF signal according to Eqs.…”

Section: Theorymentioning

confidence: 99%

Prospective correction of affine motion for arbitrary MR sequences on a clinical scanner

Nehrke

Börnert

2005

Magnetic Resonance in Med

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“…For respiratory motion, breath-holding may be used for short acquisi- tions and respiratory gating or phase-encode reordering, [30][31][32] for longer scans. Similarly for offsetting cardiac motion, cardiac gating, 33 a method of synchronizing data acquisition with the cardiac cycle, is available, whereas gradient-moment nulling has been proposed 34 for reducing pulsatility artifacts from flowing blood.…”

Section: Motion Compensationmentioning

confidence: 99%

Motion-Compensation Techniques in Neonatal and Fetal MR Imaging

Malamateniou

Malik

Counsell

et al. 2012

AJNR Am J Neuroradiol

109

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SUMMARY:Fetal and neonatal MR imaging is increasingly used as a complementary diagnostic tool to sonography. MR imaging is an ideal technique for imaging fetuses and neonates because of the absence of ionizing radiation, the superior contrast of soft tissues compared with sonography, the availability of different contrast options, and the increased FOV. Motion in the normally mobile fetus and the unsettled, sleeping, or sedated neonate during a long acquisition will decrease image quality in the form of motion artifacts, hamper image interpretation, and often necessitate a repeat MR imaging to establish a diagnosis. This article reviews current techniques of motion compensation in fetal and neonatal MR imaging, including the following: 1) motion-prevention strategies (such as adequate patient preparation, patient coaching, and sedation, when required), 2) motion-artifacts minimization methods (such as fast imaging protocols, data undersampling, and motion-resistant sequences), and 3) motion-detection/correction schemes (such as navigators and self-navigated sequences, external motion-tracking devices, and postprocessing approaches) and their application in fetal and neonatal brain MR imaging. Additionally some background on the repertoire of motion of the fetal and neonatal patient and the resulting artifacts will be presented, as well as insights into future developments and emerging techniques of motion compensation.ABBREVIATIONS: bFFE ϭ balanced fast-field echo; FLASH ϭ fast low-angle shot; G RO ϭ readout gradient; NSA ϭ number of signal averages; PROPELLER ϭ periodically rotated overlapping parallel lines with enhanced reconstruction; RF ϭ radio-frequency M R imaging is an ideal diagnostic technique for the evaluation of infants and fetuses 1-7 because of the absence of ionizing radiation, the superior contrast of soft tissues compared with sonography, and the availability of different contrast options (T1-weighted, T2-weighted, and diffusion-weighted imaging, Fig 1) to improve characterization of both anatomy and pathology. However MR imaging remains a relatively slow technique, with scanning times for most applications in the order of seconds to minutes, leaving them susceptible to motion artifacts. The normally mobile fetus and the unsettled neonate present a major difficulty because the presence of motion during a long acquisition will decrease image quality in the form of motion artifacts (Fig 2), hamper accurate image interpretation, and often necessitate a repeat MR imaging to establish a diagnosis. This may have major emotional implications for parents and can stress the tight budgets of health care providers.

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“…Solutions for this time interval have been 1) the use of improved gradients and asymmetric echo readout (4) to reduce the time between the phase-encoding gradient and the frequency-encoding echo center; 2) the addition of flow-compensation lobes to the phase-encoding gradients (3,6 -10); 3) the use of nonsequential phase-encoding sampling orders (12)(13)(14); and 4) the use of nonCartesian sampling techniques such as interleaved spirals and projection reconstruction (5). In this study we limit the discussion to Cartesian sampling, including numbers 1, 2, and 3.…”

Section: Theorymentioning

confidence: 99%

“…Nonsequential phase-encoding acquisition was first proposed for 2DFT imaging to reduce motion-related artifacts by destroying the periodicity of cyclic motion (12). Centric phase-encoding acquisition was used in 3D imaging to reduce motion artifacts by acquiring the central k-space views close together in time (13).…”

Section: Elliptical-centric (Ec) Acquisitionmentioning

confidence: 99%

The need for phase‐encoding flow compensation in high‐resolution intracranial magnetic resonance angiography

Parker

Goodrich

Roberts

et al. 2003

Magnetic Resonance Imaging

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Purpose: To demonstrate that the time delay between phase and frequency encoding and the presence of pulsatile blood flow in high-resolution time-of-flight (TOF) imaging of the intracranial arteries (especially near the circle of Willis) can distort the appearance of blood vessels and result in a cross-hatch-appearing artifact in surrounding tissue. Materials and Methods:Two techniques to reduce the artifact, tri-directional flow compensation (3DFC) and elliptical-centric (EC) phase-encoding order, are investigated in five volunteer studies.Results: 3DFC eliminates the pulsation-related artifacts and the vessel distortion. A residual amplitude variation artifact is observed. EC phase encoding nearly eliminates the pulsatile motion-related artifact, but it does not eliminate vessel distortion. Conclusion:The combination of 3DFC and EC phase encoding appears to provide the greatest artifact reduction in the five volunteer studies performed.

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Reducing motion artifacts in two-dimensional Fourier transform imaging

Cited by 196 publications

References 5 publications

Prospective correction of affine motion for arbitrary MR sequences on a clinical scanner

Prospective correction of affine motion for arbitrary MR sequences on a clinical scanner

Motion-Compensation Techniques in Neonatal and Fetal MR Imaging

The need for phase‐encoding flow compensation in high‐resolution intracranial magnetic resonance angiography

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