Respiratory gating in magnetic resonance imaging at 0.5 Tesla.

Runge, Val M.; Clanton, Jeffrey A.; Partain, C. Leon; James, A. Everette

doi:10.1148/radiology.151.2.6709928

Cited by 112 publications

(54 citation statements)

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“…The relationship between a baseline position signal S measured at the original location (k x , k y , k z ) and a later signal SЈ measured in a new rotated coordinate system (k x Ј, k y Ј, k z Ј) with translation (⌬x, ⌬y, ⌬z) is expressed in Eq. [1]. The same relation expressed in spherical coordinates is shown in Eq.…”

Section: Theorymentioning

confidence: 85%

“…Notice that the k-space radius, k , is unchanged in the new rotated coordinate frame because the signal is collected on a spherical shell. SЈ͑kЈ x ,kЈ y ,kЈ z ͒ ϭ S͑k x ,k y ,k z ͒e i2͑⌬xkxϩ⌬ykyϩ⌬zkz͒ [1] SЈ͑k ,Ј,Ј͒ ϭ S͑k ,,͒e i2k͑⌬xcossinϩ⌬ysinsinϩ⌬zcos͒ [2] Rotations of an object in the spatial domain correspond to rotations in k-space, which in this case means that points simply rotate on the spherical surface and their magnitude values do not change. Off-center rotations are mathematically equivalent to an on-center rotation plus an apparent translation of the coordinate frame, and can be treated in this manner, as is done for ONAVs.…”

Section: Theorymentioning

confidence: 99%

See 1 more Smart Citation

Spherical navigator echoes for full 3D rigid body motion measurement in MRI

Welch

Manduca

Grimm

et al. 2001

Magnetic Resonance in Med

193

226

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We developed a 3D spherical navigator (SNAV) echo technique that can measure rigid body motion in all six degrees of freedom simultaneously by sampling a spherical shell in k-space. 3D rotations of an imaged object simply rotate the data on this shell and can be detected by registration of k-space magnitude values. 3D translations add phase shifts to the data on the shell and can be detected with a weighted least-squares fit to the phase differences at corresponding points. MRI pulse sequences were developed to study k-space sampling strategies on such a shell. Data collected with a computer-controlled motion phantom with known rotational and translational motions were used to evaluate the technique. The accuracy and precision of the technique depend on the sampling density. Roughly 2000 sample points were necessary for accurate detection to within the error limits of the motion phantom when using a prototype time-intensive sampling method. This number of samples can be captured

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Section: Theorymentioning

confidence: 85%

Section: Theorymentioning

confidence: 99%

Spherical navigator echoes for full 3D rigid body motion measurement in MRI

Welch

Manduca

Grimm

et al. 2001

Magnetic Resonance in Med

193

226

View full text Add to dashboard Cite

show abstract

“…An image registration procedure was then used to determine the actual rotation of the phantom to an accuracy of 0. 1 . FNAV data were then processed to determine the rotation angles and compared with the actual rotation angles.…”

Section: Imaging Experimentsmentioning

confidence: 99%

“…For periodic physiologic (e.g., cardiac and respiratory) motion, effective motion-compensation methods have been developed and are accepted in clinical practice. A gating signal, from electrocardiography (ECG), respiratory belt, or navigator echo, is often utilized to time the data acquisition, as well as to reject and reorder data (1)(2)(3). Random, spontaneous patient motion, however, is much more challenging due to its irregularity and complexity.…”

mentioning

confidence: 99%

Motion correction using an enhanced floating navigator and GRAPPA operations

Wei

Huang

Börnert

et al. 2009

Magnetic Resonance in Med

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A method for motion correction in multicoil imaging applications, involving both data collection and reconstruction, is presented. The floating navigator method, which acquires a readout line off center in the phase-encoding direction, is expanded to detect translation/rotation and inconsistent motion. This is done by comparing floating navigator data with a reference k-space region surrounding the floating navigator line, using a correlation measure. The technique of generalized autocalibrating partially parallel acquisition is further developed to correct for a fully sampled, motion-corrupted dataset. The flexibility of generalized autocalibrating partially parallel acquisition kernels is exploited by extrapolating readout lines to fill in missing ''pie slices'' of k-space caused by rotational motion and regenerating full k-space data from multiple interleaved datasets, facilitating subsequent rigid-body motion correction or proper weighting of inconsistent data (e.g., with throughplane and nonrigid motion). Phantom and in vivo imaging experiments with turbo spin-echo sequence demonstrate the correction of severe motion artifacts. Magn Reson Med 63:339-348,

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“…In view of the tendency to employ conformation therapy based on treatment planning techniques using static CT and or MRI, instead of dynamic uoroscopy, knowledge about organ motion is becoming more and more important. There has been a surge of respiration gated studies among MRI users, since image quality may bedegraded by the respiration motion Ehman et al 1984;Runge et al 1984;Korin et al 1992;Ritchie et al 1994. Respiration motion studies for RTP are scarce.…”

Section: Mri Organ Motion Studies For Rtpmentioning

confidence: 99%

Magnetic resonance imaging in radiotherapy treatment planning

Moerland¹

1997

Medical Physics

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The aim of this study is to investigate the capabilities of magnetic resonance imaging (MRI) in radiotherapy treatment planning (RTP) and to explore the MR image distortions and how these distortions can be reduced or, if necessary, corrected in order to integrate MRI into RTP in a reliable manner. Image distortions and the efficacy of correction methods were evaluated in phantom, volunteer, and patient studies. From the measurement, analysis, and correction of machine‐related geometric distortions in MRI, it was concluded that MR image corrections are necessary in applications which require mm accuracy and that correction methods, based on 3D maps of static field inhomogeneity and gradient nonlinearity, are feasible in clinical practice. From the measurement and numerical analysis of object‐related geometric distortions, it was concluded that these distortions can be reduced to the order of the pixel size by imaging at 0.5 T and using gradients on the order of 3 mT normalm−1. Furthermore, in a study on volunteers, fast MRI scan techniques were used to measure the respiration induced kidney movement and in a study on patients with prostate cancer, the value of MRI for the evaluation of brachytherapy was demonstrated. The MR image artifacts induced by the I‐125 seeds were used to evaluate the dose distributions and dose volume histograms of permanent prostate implants.

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Respiratory gating in magnetic resonance imaging at 0.5 Tesla.

Cited by 112 publications

References 0 publications

Spherical navigator echoes for full 3D rigid body motion measurement in MRI

Spherical navigator echoes for full 3D rigid body motion measurement in MRI

Motion correction using an enhanced floating navigator and GRAPPA operations

Magnetic resonance imaging in radiotherapy treatment planning

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