Patent
Multi-dimensional iterative phase-cycled reconstruction for MRI images
| العنوان: | Multi-dimensional iterative phase-cycled reconstruction for MRI images |
|---|---|
| Patent Number: | 8,934,694 |
| تاريخ النشر: | January 13, 2015 |
| Appl. No: | 13/824704 |
| Application Filed: | October 03, 2011 |
| مستخلص: | Methods, systems, computer programs, circuits and workstations are configured to carry out image processing to generate MRI images with reduced aliasing artifacts (e.g., Nyquist and/or motion-induced image artifacts) by (a) electronically reconstructing a series of images using patient image data obtained from a patient MRI image data set by iteratively cycling through different estimated values of phase gradients in at least two dimensions; and (b) electronically selecting an image from the reconstructed images as having a lowest artifact level. |
| Inventors: | Chen, Nan-Kuei (Cary, NC, US); Avram, Alexandru V. (Bethesda, MD, US); Song, Allen W. (Chapel Hill, NC, US); Truong, Trong-Kha (Durham, NC, US) |
| Assignees: | Duke University (Durham, NC, US) |
| Claim: | 1. A method for generating MRI images with reduced aliasing artifacts in either non-parallel or parallel MRI, comprising: electronically reconstructing a series of images using patient image data obtained from a patient MRI image data set by iteratively cycling through different estimated values of phase gradients in at least two dimensions; and electronically selecting an image from the reconstructed images as having a lowest artifact level, wherein the electronically reconstructing step comprises, for a respective image slice, generating a first series of images using different possible phase gradient values along a frequency encoding direction and a second series of images using different possible values of phase gradients along a phase-encoding direction; the method further comprising: generating 1D image signal profiles associated with the reconstructed first and second series of images; and multiplying the 1D image signal profiles by a respective sigmoid-function weight to generate sigmoid-weighted signals, wherein the electronically selecting step is carried out using the sigmoid-weighted signals to identify phase error patterns. |
| Claim: | 2. The method of claim 1 , wherein the 1D image signal profiles represent background energy in the reconstructed images. |
| Claim: | 3. The method of claim 1 , wherein the reconstructing step is carried out without acquiring reference scans or without requiring user input to identify background regions in the images. |
| Claim: | 4. The method of claim 1 , wherein the generating and identifying steps are carried out to suppress, correct or remove Nyquist ghost artifacts, motion-induced artifacts or other types of aliasing artifacts from the patient images acquired with either non-parallel or parallel MRI. |
| Claim: | 5. The method of claim 1 , wherein the reconstructing image step is carried out using a defined phase range of values and a defined step size in a change in the estimated values of phase gradients (i) along the frequency encoding direction and (ii) along the phase-encoding direction. |
| Claim: | 6. The method of claim 1 , wherein the reconstructing step comprises generating a first series of images using a selected first column of image data along the phase encoding direction located near a center of a field of view (FOV) at a defined location along the frequency encoding direction, then generating a second series of images using an adjacent second column of image data with a different range of phase values and a different step size in change between phase values. |
| Claim: | 7. The method of claim 6 , wherein phase errors φ in the selected first column along the phase encoding (y) direction and location x o along the frequency-encoding direction, can be represented using at least C 1 and C 2 identified by the following equation: φ(x 0 ,y)= C 1 +C 2 ×y where C 1 includes a contribution from both 1) a phase offset that is uniform for the whole 2D image and 2) nonlinear phase terms along the frequency-encoding direction, and C 2 represents a linear phase gradient along the phase encoding direction. |
| Claim: | 8. The method of claim 6 , wherein phase errors φ in the selected first column along the phase encoding (y) direction and location x 0 along the frequency-encoding direction, can be represented using the following equation: φ(x 0 ,y)= C 1 +C 2 ×y+C 3 ×y 2 where C 1 includes a contribution from both 1) a phase offset that is uniform for a whole 2D image and 2) nonlinear phase terms along the frequency-encoding direction, C 2 represents a linear phase gradient along the phase encoding direction, and C 3 represents a nonlinear phase gradient along the phase-encoding direction. |
| Claim: | 9. The method of claim 1 , wherein the generating step comprises generating multiple sets of 1D signal profiles based on different possible values of C 1 cycled between −π and +π per pixel in a defined number “N” of steps and C 2 also cycled between −π per pixel and +π per pixel in the defined number “N” of steps to generate N×N 1D profile signals from the chosen column, where C 1 is a variable that includes a contribution from both 1) a phase offset that is uniform for a whole 2D image and 2) nonlinear phase terms along the frequency-encoding direction, and where C 2 represents a linear phase gradient along the phase encoding direction. |
| Claim: | 10. The method of claim 1 , further comprising electronically sorting the 1D signal profiles in a defined order before the multiplying step, then multiplying the sorted signal profiles by the respective sigmoid-function weight to define the sigmoid-weighted signals; electronically summing the weighted sorted signal profiles; and electronically identifying a lowest summed 1D signal profile as being an image with a lowest artifact level, wherein the elctronically selecting is carried out by identifying a phase error pattern associated with a column corresponding to the lowest summed 1D signal profile. |
| Claim: | 11. The method of claim 1 , wherein the reconstructing step is carried out so that a first series of reconstructed images is electronically evaluated using a first phase error range and iterative step size, and a second series of reconstructed images is subsequently electronically evaluated using a reduced phase error range and an adjusted step size. |
| Claim: | 12. The method of claim 1 , wherein the patient image data is obtained using at least one of the following pulse sequences: single-shot EPI, segmented EPI, parallel EPI, GRASE, multi-shot spiral imaging, fast spin-echo imaging, and integration of spin-warp imaging and EPI. |
| Claim: | 13. A method of generating images from multi-shot EPI or spiral imaging with corrected motion-induced phase errors, comprising: obtaining multi-shot EPI or spiral acquired MRI patient image data; iteratively phase cycling images of the obtained MRI patient image data reconstructed from central k-space, wherein the iterative phase cycling comprises, for a respective image slice, generating a first series of images using different possible phase gradient values along a frequency encoding direction and a second series of images using different possible values of phase gradients along a phase-encoding direction; generating 1D image signal profiles associated with the first and second series of images; and multiplying the 1D image signal profiles by a respective sigmoid-function weight to generate sigmoid-weighted signal profiles; selecting an image with a lowest level of signal intensity in a background region as the image with a least amount of aliasing using the sigmoid-weighted signal profiles to identify phase error patterns; and generating a patient image based on the selected image. |
| Claim: | 14. The method of claim 13 , wherein the phase cycling is carried out iteratively starting with a first range and step size at a first iteration, then reducing the range and adjusting the step size at a subsequent iteration. |
| Claim: | 15. The method of claim 13 , wherein the iterative phase cycling reconstructions are carried out by reconstructing low resolution images from central k-space, and wherein the generating step is carried out to generate a higher resolution patient image. |
| Claim: | 16. The method of claim 13 , further comprising sorting pixel values associated with background energy in the reconstructed images in a defined order. |
| Claim: | 17. The method of claim 16 , wherein the sorting is in an ascending order, the method further comprising summing a lowest percentage or number of pixels in each image to define a measure of background energy for that image. |
| Claim: | 18. The method of claim 13 , wherein the obtained patient image data are from diffusion-weighted spiral imaging. |
| Claim: | 19. An image processing circuit configured to (a) electronically perform iterative phase-cycled image reconstruction in at least two dimensions on MRI patient image data sets to generate MRI images with reduced aliasing artifacts without a reference scan, wherein the iterative phase-cycled reconstruction can be applied to MRI patient image data to suppress multi-dimensional phase errors in either image-domain or k-space domain, and (b) electronically select an image from the reconstructed images as having a lowest artifact level, wherein the iterative phase-cycled image reconstruction comprises, for a respective image slice, generating a first series of images using different possible phase gradient values along a frequency encoding direction and a second series of images using different possible values of phase gradients along a phase-encoding direction, generating 1D image signal profiles associated with the first and second series of images, and multiplying the 1D image signal profiles by a respective sigmoid-function weight to generate sigmoid-weighted signal profiles, wherein the electronically selecting step is carried out using the sigmoid-weighted signal profiles to identify phase error patterns. |
| Claim: | 20. The circuit of claim 19 , wherein the circuit is at least partially integrated into or in communication with at least one of: (a) a MR Scanner; (b) a clinician workstation; or (c) Picture Archiving and Communication System with archived patient image data. |
| Claim: | 21. The circuit of claim 19 , wherein the image processing circuit is configured to sort the sigmoid-function weighted signal profiles to identify phase pattern errors and correct for Nyquist artifacts. |
| Claim: | 22. The circuit of claim 19 , wherein the image processing circuit is configured to reconstruct low resolution image slices by iteratively phase cycling images of the obtained MRI patient image data from central k-space, then select an image with a lowest level of signal intensity in a background region as an image with a least amount of aliasing using the sigmoid-function weighted signal profiles, and generate a patient image based on the selected image. |
| Claim: | 23. The circuit of claim 22 , wherein the iterative phase cycling is carried out starting with a first range and step size at a first iteration, then reducing the range and adjusting the step size at a subsequent iteration. |
| Claim: | 24. An MR image processing system, comprising: a clinician workstation with a display and user interface comprising or being in communication with at least one image processing system configured to (a) electronically perform multi-dimensional iterative phase-cycled image reconstruction on MRI patient image data sets to generate MRI images with reduced artifacts without a reference scan, wherein the iterative phase-cycled reconstruction can be applied to MRI patient image data sets to suppress multi-dimensional phase errors in either image-domain or k-space domain, and (b) electronically select an image from the reconstructed images as having a lowest artifact level, wherein the iterative phase-cycled image reconstruction comprises, for a respective image slice, generating a first series of images using different possible phase gradient values along a frequency encoding direction and a second series of images using different possible values of phase gradients along a phase-encoding direction, generating 1D image signal profiles associated with the first and second series of images, and multiplying the 1D image signal profiles by a respective sigmoid-function weight to generate sigmoid-weighted signal profiles, wherein the electronically selecting step is carried out using the sigmoid-weighted signal profiles to identify phase error patterns. |
| Claim: | 25. The system of claim 24 , further comprising an MR Scanner in communication with the workstation. |
| Claim: | 26. The system of claim 24 , wherein the workstation is in communication with a Picture Archiving and Communication System with archived patient MR image data. |
| Claim: | 27. A data processing system comprising non transitory computer readable storage medium having computer readable program code embodied in the medium, the computer-readable program code comprising computer readable program code performs multi-dimensional iterative phase-cycled image reconstruction on MRI patient image data sets to generate MRI images with reduced artifacts and without a reference scan, and selects an image from the reconstructed images as having a lowest artifact level, wherein the computer readable program code that performs the iterative phase-cycled image reconstruction is configured to, for a respective image slice, generate a first series of images using different possible phase gradient values along a frequency encoding direction and a second series of images using different possible values of phase gradients along a phase-encoding direction, generate 1D image signal profiles associated with the first and second series of images, and multiply the 1D image signal profiles by a respective sigmoid-function weight to generate sigmoid-weighted signals, and wherein the computer readable program code that selects the image with the lowest artifact level uses the sigmoid-weighted signals to identify phase error patterns. |
| Claim: | 28. The method of claim 1 , wherein the patient image data includes 1D phase corrected data using a 1D reference scan. |
| Claim: | 29. An image processing circuit, wherein the image processing circuit (a) electronically performs: iterative phase-cycled image reconstruction in at least two dimensions on (i) MRI patient image data sets without a reference scan or on (ii) MRI patient image data that have been 1D phase corrected based on a reference scan, wherein the iterative phase-cycled reconstruction can be applied to the MRI patient image data to suppress multi-dimensional phase errors in either image-domain or k-space domain to generate MRI images with reduced aliasing artifacts, and (b) electronically selects an image from the reconstructed images as having a lowest artifact level wherein the iterative phase-cycled image reconstruction comprises, for a respective image slice: generating a first series of images using different possible phase gradient values along a frequency encoding direction and a second series of images using different possible values of phase gradients along a phase-encoding direction; generating 1D image signal profiles associated with the first and second series of images; and multiplying the 1D image signal profiles by a respective sigmoid-function weight to generate sigmoid-weighted singals, wherein the circuit electronically selects the image having the lowest artifact level using the sigmoid-weighted signals to identify phase error patterns. |
| Claim: | 30. An MR image processing system, comprising: a clinician workstation with a display and user interface comprising or being in communication with at least one image processing system configured to; (a) electronically perform multi-dimensional iterative phase-cycled image reconstruction on MRI patient image data sets to generate MRI images with reduced artifacts, wherein the iterative phase-cycled reconstruction can be applied to MRI patient image data sets to suppress multi-dimensional phase errors in either image-domain or k-space domain; and (b) electronically select an image from the reconstructed images as having a lowest artifact level, and wherein the electronic iterative phase-cycled image reconstruction comprises, for a respective image slice, generating a first series of images using different possible phase gradient values along a frequency encoding direction, generating a second series of images using different possible values of phase gradients along a phase-encoding direction, generating 1D image signal profiles associated with the first and second series of images, and multiplying the 1D image signal profiles by a respective sigmoid-function weight to generate sigmoid-weighted signals, wherein the electronic selection uses the sigmoid-weighted signals to identify phase error patterns. |
| Claim: | 31. The system of claim 30 , wherein the image processing system is configured to perform the multi-dimensional iterative phase-cycled image reconstruction on MRI patient image data sets without a reference scan. |
| Claim: | 32. The system of claim 30 , wherein the image processing system is configured to perform the multi-dimensional iterative phase-cycled image reconstruction on MRI patient image data that have been 1D phase corrected based on a reference scan. |
| Current U.S. Class: | 382/131 |
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| Primary Examiner: | Bitar, Nancy |
| Attorney, Agent or Firm: | Myers Bigel Sibley & Sajovec, P.A. |
| رقم الانضمام: | edspgr.08934694 |
| قاعدة البيانات: | USPTO Patent Grants |
| الوصف غير متاح. |