[ { "key": "Z9SXGNNQ", "version": 2, "library": { "type": "group", "id": 230303, "name": "EPI geometry correction", "links": { "alternate": { "href": "https://www.zotero.org/groups/epi_geometry_correction", "type": "text/html" } } }, "links": { "self": { "href": "https://api.zotero.org/groups/230303/items/Z9SXGNNQ", "type": "application/json" }, "alternate": { "href": "https://www.zotero.org/groups/epi_geometry_correction/items/Z9SXGNNQ", "type": "text/html" } }, "meta": { "createdByUser": { "id": 51558, "username": "zigurana", "name": "Daniel Polders", "links": { "alternate": { "href": "https://www.zotero.org/zigurana", "type": "text/html" } } }, "creatorSummary": "Reber et al.", "parsedDate": "1998", "numChildren": 0 }, "data": { "key": "Z9SXGNNQ", "version": 2, "itemType": "journalArticle", "title": "Correction of off resonance-related distortion in echo-planar imaging using EPI-based field maps", "creators": [ { "creatorType": "author", "firstName": "Paul J.", "lastName": "Reber" }, { "creatorType": "author", "firstName": "Eric C.", "lastName": "Wong" }, { "creatorType": "author", "firstName": "Richard B.", "lastName": "Buxton" }, { "creatorType": "author", "firstName": "Lawrence R.", "lastName": "Frank" } ], "abstractNote": "We present, here, a simple method for measurement and correction of off-resonance related geometric distortion in echo-planar imaging (EP1). This method uses high signal-to-noise ratio (SNR) EPI-based field maps, rapidly acquired using a series of gradient recalled images collected across a range of TE values. This field map is distorted in the same manner as the EPI images to be unwarped, providing a direct look-up table for the correct location of each pixel of data. This method adds very little scan time and is robust and easy to implement.", "publicationTitle": "Magnetic Resonance in Medicine", "publisher": "", "place": "", "date": "1998", "volume": "39", "issue": "2", "section": "", "partNumber": "", "partTitle": "", "pages": "328–330", "series": "", "seriesTitle": "", "seriesText": "", "journalAbbreviation": "", "DOI": "10.1002/mrm.1910390223", "citationKey": "", "url": "http://onlinelibrary.wiley.com/doi/10.1002/mrm.1910390223/abstract", "accessDate": "2013-11-07T15:53:48Z", "PMID": "", "PMCID": "", "ISSN": "1522-2594", "archive": "", "archiveLocation": "", "shortTitle": "", "language": "en", "libraryCatalog": "Wiley Online Library", "callNumber": "", "rights": "Copyright © 1998 Wiley-Liss, Inc., A Wiley Company", "extra": "", "tags": [ { "tag": "Echo-Planar Imaging", "type": 1 }, { "tag": "Geometric distortion", "type": 1 }, { "tag": "field map correction", "type": 1 } ], "collections": [ "KBCFGVCJ" ], "relations": {}, "dateAdded": "2013-11-07T16:03:59Z", "dateModified": "2013-11-07T16:03:59Z" } }, { "key": "ZF52X5R7", "version": 2, "library": { "type": "group", "id": 230303, "name": "EPI geometry correction", "links": { "alternate": { "href": "https://www.zotero.org/groups/epi_geometry_correction", "type": "text/html" } } }, "links": { "self": { "href": "https://api.zotero.org/groups/230303/items/ZF52X5R7", "type": "application/json" }, "alternate": { "href": "https://www.zotero.org/groups/epi_geometry_correction/items/ZF52X5R7", "type": "text/html" } }, "meta": { "createdByUser": { "id": 51558, "username": "zigurana", "name": "Daniel Polders", "links": { "alternate": { "href": "https://www.zotero.org/zigurana", "type": "text/html" } } }, "creatorSummary": "Farzaneh et al.", "parsedDate": "1990", "numChildren": 0 }, "data": { "key": "ZF52X5R7", "version": 2, "itemType": "journalArticle", "title": "Analysis of T2 limitations and off-resonance effects on spatial resolution and artifacts in echo-planar imaging", "creators": [ { "creatorType": "author", "firstName": "Farhad", "lastName": "Farzaneh" }, { "creatorType": "author", "firstName": "Stephen J.", "lastName": "Riederer" }, { "creatorType": "author", "firstName": "Norbert J.", "lastName": "Pelc" } ], "abstractNote": "Several aspects of blipped echo-planar imaging (EPI) are treated mathematically. An expression relating the necessary readout gradient strength and sampling time to the spatial resolution and readout duration is derived. It is shown how the net spatial resolution may be limited by the object's T2 characteristics and Bo field homogeneity, irrespective of the number of sampled points. Additionally, off-resonance effects result in a loss of spatial resolution and image distortion to a considerably greater degree than in conventional two-dimensional Fourier transform imaging. The extent of these effects is directly related to the time required to acquire the data matrix, and is therefore amplified when EPI is implemented on a standard commercial whole-body system which because of limited gradient performance uses necessarily longer sampling durations. Specific hardware modifications to a standard commercial imager are considered to allow successful EPI implementation. EPI image characteristics are compared quantitatively with those of conventional methods. © 1990 Academic Press, Inc.", "publicationTitle": "Magnetic Resonance in Medicine", "publisher": "", "place": "", "date": "1990", "volume": "14", "issue": "1", "section": "", "partNumber": "", "partTitle": "", "pages": "123–139", "series": "", "seriesTitle": "", "seriesText": "", "journalAbbreviation": "", "DOI": "10.1002/mrm.1910140112", "citationKey": "", "url": "http://onlinelibrary.wiley.com/doi/10.1002/mrm.1910140112/abstract", "accessDate": "2013-11-07T15:22:30Z", "PMID": "", "PMCID": "", "ISSN": "1522-2594", "archive": "", "archiveLocation": "", "shortTitle": "", "language": "en", "libraryCatalog": "Wiley Online Library", "callNumber": "", "rights": "Copyright © 1990 Wiley-Liss, Inc., A Wiley Company", "extra": "", "tags": [], "collections": [ "KBCFGVCJ" ], "relations": {}, "dateAdded": "2013-11-07T16:03:59Z", "dateModified": "2013-11-07T16:03:59Z" } }, { "key": "6QGHA3PP", "version": 2, "library": { "type": "group", "id": 230303, "name": "EPI geometry correction", "links": { "alternate": { "href": "https://www.zotero.org/groups/epi_geometry_correction", "type": "text/html" } } }, "links": { "self": { "href": "https://api.zotero.org/groups/230303/items/6QGHA3PP", "type": "application/json" }, "alternate": { "href": "https://www.zotero.org/groups/epi_geometry_correction/items/6QGHA3PP", "type": "text/html" } }, "meta": { "createdByUser": { "id": 51558, "username": "zigurana", "name": "Daniel Polders", "links": { "alternate": { "href": "https://www.zotero.org/zigurana", "type": "text/html" } } }, "creatorSummary": "Munger et al.", "parsedDate": "1998", "numChildren": 0 }, "data": { "key": "6QGHA3PP", "version": 2, "itemType": "conferencePaper", "title": "Conjugate Gradient Restoration of EPI images", "creators": [ { "creatorType": "author", "firstName": "P", "lastName": "Munger" }, { "creatorType": "author", "name": "G.R. Crelier" }, { "creatorType": "author", "name": "T.M. Peters" }, { "creatorType": "author", "name": "G.B. Pike" } ], "abstractNote": "", "proceedingsTitle": "Proceedings of the International Society for Magnetic Resonance in Medicine", "conferenceName": "", "publisher": "", "place": "Sydney, Australia", "date": "1998", "eventPlace": "", "volume": "", "issue": "", "numberOfVolumes": "", "pages": "416", "series": "", "seriesNumber": "", "DOI": "", "ISBN": "", "citationKey": "", "url": "", "accessDate": "", "ISSN": "", "archive": "", "archiveLocation": "", "shortTitle": "", "language": "", "libraryCatalog": "", "callNumber": "", "rights": "", "extra": "", "tags": [], "collections": [ "KBCFGVCJ" ], "relations": {}, "dateAdded": "2013-11-07T16:03:59Z", "dateModified": "2013-11-07T16:03:59Z" } }, { "key": "U4S6BXKT", "version": 2, "library": { "type": "group", "id": 230303, "name": "EPI geometry correction", "links": { "alternate": { "href": "https://www.zotero.org/groups/epi_geometry_correction", "type": "text/html" } } }, "links": { "self": { "href": "https://api.zotero.org/groups/230303/items/U4S6BXKT", "type": "application/json" }, "alternate": { "href": "https://www.zotero.org/groups/epi_geometry_correction/items/U4S6BXKT", "type": "text/html" } }, "meta": { "createdByUser": { "id": 51558, "username": "zigurana", "name": "Daniel Polders", "links": { "alternate": { "href": "https://www.zotero.org/zigurana", "type": "text/html" } } }, "creatorSummary": "Munger et al.", "parsedDate": "2000", "numChildren": 0 }, "data": { "key": "U4S6BXKT", "version": 2, "itemType": "journalArticle", "title": "An inverse problem approach to the correction of distortion in EPI images", "creators": [ { "creatorType": "author", "firstName": "P.", "lastName": "Munger" }, { "creatorType": "author", "firstName": "G.R.", "lastName": "Crelier" }, { "creatorType": "author", "firstName": "T.M.", "lastName": "Peters" }, { "creatorType": "author", "firstName": "G.B.", "lastName": "Pike" } ], "abstractNote": "Magnetic resonance imaging using the echo planar imaging (EPI) technique is particularly sensitive to main (B 0) field inhomogeneities. The primary effect is geometrical distortion in the phase encoding direction. Here, the authors present a method based on the conjugate gradient algorithm to correct for this geometrical distortion, by solving the EPI imaging equation. Two versions are presented: one that attempts to solve the full four-dimensional (4-D) imaging equation, and one that independently solves for each profile along the blip encoding direction. Results are presented for both phantom and in vivo brain EPI images and compared with other proposed correction methods.", "publicationTitle": "IEEE Transactions on Medical Imaging", "publisher": "", "place": "", "date": "2000", "volume": "19", "issue": "7", "section": "", "partNumber": "", "partTitle": "", "pages": "681-689", "series": "", "seriesTitle": "", "seriesText": "", "journalAbbreviation": "", "DOI": "10.1109/42.875186", "citationKey": "", "url": "", "accessDate": "", "PMID": "", "PMCID": "", "ISSN": "0278-0062", "archive": "", "archiveLocation": "", "shortTitle": "", "language": "", "libraryCatalog": "IEEE Xplore", "callNumber": "", "rights": "", "extra": "", "tags": [ { "tag": "Algorithms", "type": 1 }, { "tag": "Brain", "type": 1 }, { "tag": "EPI images", "type": 1 }, { "tag": "EPI imaging equation", "type": 1 }, { "tag": "Echo-Planar Imaging", "type": 1 }, { "tag": "Equations", "type": 1 }, { "tag": "Humans", "type": 1 }, { "tag": "Image Processing, Computer-Assisted", "type": 1 }, { "tag": "Image coding", "type": 1 }, { "tag": "Magnetic Resonance Imaging", "type": 1 }, { "tag": "Nonlinear distortion", "type": 1 }, { "tag": "Nonuniform sampling", "type": 1 }, { "tag": "Phase distortion", "type": 1 }, { "tag": "Predistortion", "type": 1 }, { "tag": "Sampling methods", "type": 1 }, { "tag": "_tablet" }, { "tag": "biomedical MRI", "type": 1 }, { "tag": "blip encoding direction", "type": 1 }, { "tag": "conjugate gradient algorithm", "type": 1 }, { "tag": "conjugate gradient methods", "type": 1 }, { "tag": "distortion correction", "type": 1 }, { "tag": "full four-dimensional imaging equation", "type": 1 }, { "tag": "geometrical distortion", "type": 1 }, { "tag": "image reconstruction", "type": 1 }, { "tag": "in vivo brain EPI images", "type": 1 }, { "tag": "inverse problem approach", "type": 1 }, { "tag": "inverse problems", "type": 1 }, { "tag": "main field inhomogeneities", "type": 1 }, { "tag": "medical diagnostic imaging", "type": 1 }, { "tag": "medical image processing", "type": 1 }, { "tag": "phantom images", "type": 1 } ], "collections": [ "KBCFGVCJ" ], "relations": {}, "dateAdded": "2013-11-07T16:03:59Z", "dateModified": "2013-11-07T16:03:59Z" } }, { "key": "E496AVB3", "version": 2, "library": { "type": "group", "id": 230303, "name": "EPI geometry correction", "links": { "alternate": { "href": "https://www.zotero.org/groups/epi_geometry_correction", "type": "text/html" } } }, "links": { "self": { "href": "https://api.zotero.org/groups/230303/items/E496AVB3", "type": "application/json" }, "alternate": { "href": "https://www.zotero.org/groups/epi_geometry_correction/items/E496AVB3", "type": "text/html" } }, "meta": { "createdByUser": { "id": 51558, "username": "zigurana", "name": "Daniel Polders", "links": { "alternate": { "href": "https://www.zotero.org/zigurana", "type": "text/html" } } }, "creatorSummary": "Munger", "parsedDate": "2001", "numChildren": 0 }, "data": { "key": "E496AVB3", "version": 2, "itemType": "thesis", "title": "An inverse-problem approach to spatial distortion correction in MRI /", "creators": [ { "creatorType": "author", "firstName": "Patrice", "lastName": "Munger" } ], "abstractNote": "This thesis treats of the issue of distortion in magnetic resonance (MR) imaging, with focus on Echo Planar imaging (EPI) and anatomical 3D imaging. After a review of MR theory, the principle of image formation, an analysis of distortion in the context of MRI and field mapping principles, an analysis of the EPI image formation process, which reveals the two-dimensional nature of the EPI point-spread function (PSF), is presented, and a full 2D correction technique based on the inversion of the 4D tensor EPI imaging equation using the Conjugate Gradient (CG) method is proposed. A 1D approximation of the technique is also derived for cases where the PSF can be approximated as being one-dimensional, such as in Fourier imaging, or EPI imaging in fields with low field inhomogeneity. The proposed technique is demonstrated by means of computer simulations, and several aspects of its implementation are studied. A comparison between different correction methods based on field map data, still using computer simulations, is presented and reveals the behaviour of the different methods when applied in non-ideal conditions. Finally, the practical application of the proposed method is demonstrated on real EPI scans and gradient echo images. This work reveals some interesting characteristics of the correction method based on the CG algorithm, like fast convergence, possibility to recover from severe distortions and EPI B0-induced ghost artifacts reduction, but it also points out limitations of this correction method, such as potentially high computational cost and noise sensitivity.", "thesisType": "", "university": "", "place": "", "date": "2001", "series": "", "seriesNumber": "", "numPages": "", "DOI": "", "ISBN": "", "citationKey": "", "url": "http://digitool.library.mcgill.ca/R/?func=dbin-jump-full&object_id=37792&local_base=GEN01-MCG02", "accessDate": "2013-08-15T09:31:08Z", "ISSN": "", "archive": "", "archiveLocation": "", "shortTitle": "", "language": "", "libraryCatalog": "digitool.library.mcgill.ca", "callNumber": "", "rights": "", "extra": "", "tags": [], "collections": [ "KBCFGVCJ" ], "relations": {}, "dateAdded": "2013-11-07T16:03:59Z", "dateModified": "2013-11-07T16:03:59Z" } }, { "key": "37HBPH8Q", "version": 2, "library": { "type": "group", "id": 230303, "name": "EPI geometry correction", "links": { "alternate": { "href": "https://www.zotero.org/groups/epi_geometry_correction", "type": "text/html" } } }, "links": { "self": { "href": "https://api.zotero.org/groups/230303/items/37HBPH8Q", "type": "application/json" }, "alternate": { "href": "https://www.zotero.org/groups/epi_geometry_correction/items/37HBPH8Q", "type": "text/html" } }, "meta": { "createdByUser": { "id": 51558, "username": "zigurana", "name": "Daniel Polders", "links": { "alternate": { "href": "https://www.zotero.org/zigurana", "type": "text/html" } } }, "creatorSummary": "Hutton et al.", "parsedDate": "2002-05", "numChildren": 0 }, "data": { "key": "37HBPH8Q", "version": 2, "itemType": "journalArticle", "title": "Image Distortion Correction in fMRI: A Quantitative Evaluation", "creators": [ { "creatorType": "author", "firstName": "Chloe", "lastName": "Hutton" }, { "creatorType": "author", "firstName": "Andreas", "lastName": "Bork" }, { "creatorType": "author", "firstName": "Oliver", "lastName": "Josephs" }, { "creatorType": "author", "firstName": "Ralf", "lastName": "Deichmann" }, { "creatorType": "author", "firstName": "John", "lastName": "Ashburner" }, { "creatorType": "author", "firstName": "Robert", "lastName": "Turner" } ], "abstractNote": "A well-recognized problem with the echo-planar imaging (EPI) technique most commonly used for functional magnetic resonance imaging (fMRI) studies is geometric distortion caused by magnetic field inhomogeneity. This makes it difficult to achieve an accurate registration between a functional activation map calculated from an EPI time series and an undistorted, high resolution anatomical image. A correction method based on mapping the spatial distribution of field inhomogeneities can be used to reduce these distortions. This approach is attractive in its simplicity but requires postprocessing to improve the robustness of the acquired field map and reduce any secondary artifacts. Furthermore, the distribution of the internal magnetic field throughout the head is position dependent resulting in an interaction between distortion and head motion. Therefore, a single field map may not be sufficient to correct for the distortions throughout a whole fMRI time series. In this paper we present a quantitative evaluation of image distortion correction for fMRI at 2T. We assess (i) methods for the acquisition and calculation of field maps, (ii) the effect of image distortion correction on the coregistration between anatomical and functional images, and (iii) the interaction between distortion and head motion, assessing the feasibility of using field maps to reduce this effect. We propose that field maps with acceptable noise levels can be generated easily using a dual echo-time EPI sequence and demonstrate the importance of distortion correction for anatomical coregistration, even for small distortions. Using a dual echo-time series to generate a unique field map at each time point, we characterize the interaction between head motion and geometric distortion. However, we suggest that the variance between successively measured field maps introduces additional unwanted variance in the voxel time-series and is therefore not adequate to correct for time-varying distortions.", "publicationTitle": "NeuroImage", "publisher": "", "place": "", "date": "May 2002", "volume": "16", "issue": "1", "section": "", "partNumber": "", "partTitle": "", "pages": "217-240", "series": "", "seriesTitle": "", "seriesText": "", "journalAbbreviation": "NeuroImage", "DOI": "10.1006/nimg.2001.1054", "citationKey": "", "url": "http://www.sciencedirect.com/science/article/pii/S1053811901910547", "accessDate": "2013-08-14T14:56:20Z", "PMID": "", "PMCID": "", "ISSN": "1053-8119", "archive": "", "archiveLocation": "", "shortTitle": "Image Distortion Correction in fMRI", "language": "", "libraryCatalog": "ScienceDirect", "callNumber": "", "rights": "", "extra": "", "tags": [], "collections": [ "KBCFGVCJ" ], "relations": {}, "dateAdded": "2013-11-07T16:03:59Z", "dateModified": "2013-11-07T16:03:59Z" } }, { "key": "I4FFQS89", "version": 2, "library": { "type": "group", "id": 230303, "name": "EPI geometry correction", "links": { "alternate": { "href": "https://www.zotero.org/groups/epi_geometry_correction", "type": "text/html" } } }, "links": { "self": { "href": "https://api.zotero.org/groups/230303/items/I4FFQS89", "type": "application/json" }, "alternate": { "href": "https://www.zotero.org/groups/epi_geometry_correction/items/I4FFQS89", "type": "text/html" } }, "meta": { "createdByUser": { "id": 51558, "username": "zigurana", "name": "Daniel Polders", "links": { "alternate": { "href": "https://www.zotero.org/zigurana", "type": "text/html" } } }, "creatorSummary": "Zeng and Constable", "parsedDate": "2002", "numChildren": 0 }, "data": { "key": "I4FFQS89", "version": 2, "itemType": "journalArticle", "title": "Image distortion correction in EPI: Comparison of field mapping with point spread function mapping", "creators": [ { "creatorType": "author", "firstName": "Huairen", "lastName": "Zeng" }, { "creatorType": "author", "firstName": "R. Todd", "lastName": "Constable" } ], "abstractNote": "Echo-planar imaging (EPI) can provide rapid imaging by acquiring a complete k-space data set in a single acquisition. However, this approach suffers from distortion effects in geometry and intensity, resulting in poor image quality. The distortions, caused primarily by field inhomogeneities, lead to intensity loss and voxel shifts, the latter of which are particularly severe in the phase-encode direction. Two promising approaches to correct the distortion in EPI are field mapping and point spread function (PSF) mapping. The field mapping method measures the field distortions and translates these into voxel shifts, which can be used to assign image intensities to the correct voxel locations. The PSF approach uses acquisitions with additional phase-encoding gradients applied in the x, y, and/or z directions to map the 1D, 2D, or 3D PSF of each voxel. These PSFs encode the spatial information about the distortion and the overall distribution of intensities from a single voxel. The measured image is the convolution of the undistorted density and the PSF. Measuring the PSF allows the distortion in geometry and intensity to be corrected. This work compares the efficacy of these methods with equal time allowed for field mapping and PSF mapping. Magn Reson Med 48:137–146, 2002. © 2002 Wiley-Liss, Inc.", "publicationTitle": "Magnetic Resonance in Medicine", "publisher": "", "place": "", "date": "2002", "volume": "48", "issue": "1", "section": "", "partNumber": "", "partTitle": "", "pages": "137–146", "series": "", "seriesTitle": "", "seriesText": "", "journalAbbreviation": "", "DOI": "10.1002/mrm.10200", "citationKey": "", "url": "http://onlinelibrary.wiley.com/doi/10.1002/mrm.10200/abstract", "accessDate": "2013-08-14T14:51:24Z", "PMID": "", "PMCID": "", "ISSN": "1522-2594", "archive": "", "archiveLocation": "", "shortTitle": "Image distortion correction in EPI", "language": "en", "libraryCatalog": "Wiley Online Library", "callNumber": "", "rights": "Copyright © 2002 Wiley-Liss, Inc.", "extra": "", "tags": [ { "tag": "Echo-Planar Imaging", "type": 1 }, { "tag": "Geometric distortion", "type": 1 }, { "tag": "field mapping", "type": 1 }, { "tag": "point spread function", "type": 1 }, { "tag": "rapid imaging", "type": 1 } ], "collections": [ "KBCFGVCJ" ], "relations": {}, "dateAdded": "2013-11-07T16:03:59Z", "dateModified": "2013-11-07T16:03:59Z" } }, { "key": "SBH22K6Z", "version": 2, "library": { "type": "group", "id": 230303, "name": "EPI geometry correction", "links": { "alternate": { "href": "https://www.zotero.org/groups/epi_geometry_correction", "type": "text/html" } } }, "links": { "self": { "href": "https://api.zotero.org/groups/230303/items/SBH22K6Z", "type": "application/json" }, "alternate": { "href": "https://www.zotero.org/groups/epi_geometry_correction/items/SBH22K6Z", "type": "text/html" } }, "meta": { "createdByUser": { "id": 51558, "username": "zigurana", "name": "Daniel Polders", "links": { "alternate": { "href": "https://www.zotero.org/zigurana", "type": "text/html" } } }, "creatorSummary": "Haselgrove and Moore", "parsedDate": "1996", "numChildren": 0 }, "data": { "key": "SBH22K6Z", "version": 2, "itemType": "journalArticle", "title": "Correction for distortion of echo-planar images used to calculate the apparent diffusion coefficient", "creators": [ { "creatorType": "author", "firstName": "John C.", "lastName": "Haselgrove" }, { "creatorType": "author", "firstName": "James R.", "lastName": "Moore" } ], "abstractNote": "An algorithm for correcting the distortions that occur in diffusion-weighted echo-planar images due to the strong diffusion-sensitizing gradients is presented. The dominant distortions may be considered to be only changes of scale coupled with a shear and linear translation in the phase-encoding direction. It is then possible to correct for them by using an algorithm in which each line of the image in the phase-encoding direction is considered in turn, with only one parameter (the scale) to be found by searching.", "publicationTitle": "Magnetic Resonance in Medicine", "publisher": "", "place": "", "date": "1996", "volume": "36", "issue": "6", "section": "", "partNumber": "", "partTitle": "", "pages": "960–964", "series": "", "seriesTitle": "", "seriesText": "", "journalAbbreviation": "", "DOI": "10.1002/mrm.1910360620", "citationKey": "", "url": "http://onlinelibrary.wiley.com/doi/10.1002/mrm.1910360620/abstract", "accessDate": "2013-11-07T15:38:54Z", "PMID": "", "PMCID": "", "ISSN": "1522-2594", "archive": "", "archiveLocation": "", "shortTitle": "", "language": "en", "libraryCatalog": "Wiley Online Library", "callNumber": "", "rights": "Copyright © 1996 Wiley-Liss, Inc., A Wiley Company", "extra": "", "tags": [ { "tag": "EPI", "type": 1 }, { "tag": "apparent diffusion coefficient (ADC)", "type": 1 }, { "tag": "diffusion imaging", "type": 1 }, { "tag": "distortions", "type": 1 } ], "collections": [ "KBCFGVCJ" ], "relations": {}, "dateAdded": "2013-11-07T16:03:59Z", "dateModified": "2013-11-07T16:03:59Z" } }, { "key": "NPKAC5U3", "version": 2, "library": { "type": "group", "id": 230303, "name": "EPI geometry correction", "links": { "alternate": { "href": "https://www.zotero.org/groups/epi_geometry_correction", "type": "text/html" } } }, "links": { "self": { "href": "https://api.zotero.org/groups/230303/items/NPKAC5U3", "type": "application/json" }, "alternate": { "href": "https://www.zotero.org/groups/epi_geometry_correction/items/NPKAC5U3", "type": "text/html" } }, "meta": { "createdByUser": { "id": 51558, "username": "zigurana", "name": "Daniel Polders", "links": { "alternate": { "href": "https://www.zotero.org/zigurana", "type": "text/html" } } }, "creatorSummary": "Robinson and Jovicich", "parsedDate": "2011", "numChildren": 0 }, "data": { "key": "NPKAC5U3", "version": 2, "itemType": "journalArticle", "title": "B0 mapping with multi-channel RF coils at high field", "creators": [ { "creatorType": "author", "firstName": "Simon", "lastName": "Robinson" }, { "creatorType": "author", "firstName": "Jorge", "lastName": "Jovicich" } ], "abstractNote": "", "publicationTitle": "Magnetic Resonance in Medicine", "publisher": "", "place": "", "date": "10/2011", "volume": "66", "issue": "4", "section": "", "partNumber": "", "partTitle": "", "pages": "976-988", "series": "", "seriesTitle": "", "seriesText": "", "journalAbbreviation": "", "DOI": "10.1002/mrm.22879", "citationKey": "", "url": "http://doi.wiley.com/10.1002/mrm.22879", "accessDate": "2013-09-25T15:13:10Z", "PMID": "", "PMCID": "", "ISSN": "07403194", "archive": "", "archiveLocation": "", "shortTitle": "", "language": "", "libraryCatalog": "CrossRef", "callNumber": "", "rights": "", "extra": "", "tags": [ { "tag": "_tablet" } ], "collections": [ "KBCFGVCJ" ], "relations": {}, "dateAdded": "2013-11-07T16:03:59Z", "dateModified": "2013-11-07T16:03:59Z" } }, { "key": "F87XBZME", "version": 2, "library": { "type": "group", "id": 230303, "name": "EPI geometry correction", "links": { "alternate": { "href": "https://www.zotero.org/groups/epi_geometry_correction", "type": "text/html" } } }, "links": { "self": { "href": "https://api.zotero.org/groups/230303/items/F87XBZME", "type": "application/json" }, "alternate": { "href": "https://www.zotero.org/groups/epi_geometry_correction/items/F87XBZME", "type": "text/html" } }, "meta": { "createdByUser": { "id": 51558, "username": "zigurana", "name": "Daniel Polders", "links": { "alternate": { "href": "https://www.zotero.org/zigurana", "type": "text/html" } } }, "creatorSummary": "Reinsberg et al.", "parsedDate": "2005-06-07", "numChildren": 0 }, "data": { "key": "F87XBZME", "version": 2, "itemType": "journalArticle", "title": "A complete distortion correction for MR images: II. Rectification of static-field inhomogeneities by similarity-based profile mapping", "creators": [ { "creatorType": "author", "firstName": "Stefan A.", "lastName": "Reinsberg" }, { "creatorType": "author", "firstName": "Simon J.", "lastName": "Doran" }, { "creatorType": "author", "firstName": "Elizabeth M.", "lastName": "Charles-Edwards" }, { "creatorType": "author", "firstName": "Martin O.", "lastName": "Leach" } ], "abstractNote": "Radiotherapy treatment planning relies on the use of geometrically correct images. This paper presents a fully automatic tool for correcting MR images for the effects of B0 inhomogeneities. The post-processing method is based on the gradient-reversal technique of Chang and Fitzpatrick (1992 IEEE Trans. Med. Imaging 11 319–29) which combines two identical images acquired with a forward- and a reversed read gradient. This paper demonstrates how maximization of mutual information for registration of forward and reverse read gradient images allows the elimination of user interaction for the correction. Image quality is preserved to a degree not reported previously.", "publicationTitle": "Physics in Medicine and Biology", "publisher": "", "place": "", "date": "2005-06-07", "volume": "50", "issue": "11", "section": "", "partNumber": "", "partTitle": "", "pages": "2651", "series": "", "seriesTitle": "", "seriesText": "", "journalAbbreviation": "Phys. Med. Biol.", "DOI": "10.1088/0031-9155/50/11/014", "citationKey": "", "url": "http://iopscience.iop.org/0031-9155/50/11/014", "accessDate": "2013-09-03T10:24:43Z", "PMID": "", "PMCID": "", "ISSN": "0031-9155", "archive": "", "archiveLocation": "", "shortTitle": "A complete distortion correction for MR images", "language": "en", "libraryCatalog": "Institute of Physics", "callNumber": "", "rights": "", "extra": "", "tags": [], "collections": [ "KBCFGVCJ" ], "relations": {}, "dateAdded": "2013-11-07T16:03:59Z", "dateModified": "2013-11-07T16:03:59Z" } }, { "key": "26JTDP3S", "version": 2, "library": { "type": "group", "id": 230303, "name": "EPI geometry correction", "links": { "alternate": { "href": "https://www.zotero.org/groups/epi_geometry_correction", "type": "text/html" } } }, "links": { "self": { "href": "https://api.zotero.org/groups/230303/items/26JTDP3S", "type": "application/json" }, "alternate": { "href": "https://www.zotero.org/groups/epi_geometry_correction/items/26JTDP3S", "type": "text/html" } }, "meta": { "createdByUser": { "id": 51558, "username": "zigurana", "name": "Daniel Polders", "links": { "alternate": { "href": "https://www.zotero.org/zigurana", "type": "text/html" } } }, "creatorSummary": "Doran et al.", "parsedDate": "2005-04-07", "numChildren": 0 }, "data": { "key": "26JTDP3S", "version": 2, "itemType": "journalArticle", "title": "A complete distortion correction for MR images: I. Gradient warp correction", "creators": [ { "creatorType": "author", "firstName": "Simon J.", "lastName": "Doran" }, { "creatorType": "author", "firstName": "Liz", "lastName": "Charles-Edwards" }, { "creatorType": "author", "firstName": "Stefan A.", "lastName": "Reinsberg" }, { "creatorType": "author", "firstName": "Martin O.", "lastName": "Leach" } ], "abstractNote": "MR images are known to be distorted because of both gradient nonlinearity and imperfections in the B0 field, the latter caused either by an imperfect shim or sample-induced distortions. This paper describes in detail a method for correcting the gradient warp distortion, based on a direct field mapping using a custom-built phantom with three orthogonal grids of fluid-filled rods. The key advance of the current work over previous contributions is the large volume of the mapping phantom and the large distortions (>25 mm) corrected, making the method suitable for use with large field of view, extra-cranial images. Experimental measurements on the Siemens AS25 gradient set, as installed on a Siemens Vision scanner, are compared with a theoretical description of the gradient set, based on the manufacturer's spherical harmonic coefficients. It was found that over a volume of 320 × 200 × 340 mm3 distortions can be successfully mapped to within the voxel resolution of the raw imaging data, whilst outside this volume, correction is still good but some systematic errors are present. The phenomenon of through-plane distortion (also known as 'slice warp') is examined in detail, and the perturbation it causes to the measurements is quantified and corrected. At the very edges of the region of support provided by the phantom, through-plane distortion is extreme and only partially corrected by the present method. Solutions to this problem are discussed. Both phantom and patient data demonstrate the efficacy of the gradient warp correction.", "publicationTitle": "Physics in Medicine and Biology", "publisher": "", "place": "", "date": "2005-04-07", "volume": "50", "issue": "7", "section": "", "partNumber": "", "partTitle": "", "pages": "1343", "series": "", "seriesTitle": "", "seriesText": "", "journalAbbreviation": "Phys. Med. Biol.", "DOI": "10.1088/0031-9155/50/7/001", "citationKey": "", "url": "http://iopscience.iop.org/0031-9155/50/7/001", "accessDate": "2013-09-03T10:19:26Z", "PMID": "", "PMCID": "", "ISSN": "0031-9155", "archive": "", "archiveLocation": "", "shortTitle": "A complete distortion correction for MR images", "language": "en", "libraryCatalog": "Institute of Physics", "callNumber": "", "rights": "", "extra": "", "tags": [], "collections": [ "KBCFGVCJ" ], "relations": {}, "dateAdded": "2013-11-07T16:03:59Z", "dateModified": "2013-11-07T16:03:59Z" } }, { "key": "ZGFX6CRT", "version": 2, "library": { "type": "group", "id": 230303, "name": "EPI geometry correction", "links": { "alternate": { "href": "https://www.zotero.org/groups/epi_geometry_correction", "type": "text/html" } } }, "links": { "self": { "href": "https://api.zotero.org/groups/230303/items/ZGFX6CRT", "type": "application/json" }, "alternate": { "href": "https://www.zotero.org/groups/epi_geometry_correction/items/ZGFX6CRT", "type": "text/html" } }, "meta": { "createdByUser": { "id": 51558, "username": "zigurana", "name": "Daniel Polders", "links": { "alternate": { "href": "https://www.zotero.org/zigurana", "type": "text/html" } } }, "creatorSummary": "Jezzard and Balaban", "parsedDate": "1995", "numChildren": 0 }, "data": { "key": "ZGFX6CRT", "version": 2, "itemType": "journalArticle", "title": "Correction for geometric distortion in echo planar images from B0 field variations", "creators": [ { "creatorType": "author", "firstName": "Peter", "lastName": "Jezzard" }, { "creatorType": "author", "firstName": "Robert S.", "lastName": "Balaban" } ], "abstractNote": "A method is described for the correction of geometric distortions occurring in echo planar images. The geometric distortions are caused in large part by static magnetic field inho-mogeneities, leading to pixel shifts, particularly in the phase encode direction. By characterizing the field inhomogeneities from a field map, the image can be unwarped so that accurate alignment to conventionally collected images can be made. The algorithm to perform the unwarping is described, and results from echo planar images collected at 1.5 and 4 Tesla are shown.", "publicationTitle": "Magnetic Resonance in Medicine", "publisher": "", "place": "", "date": "1995", "volume": "34", "issue": "1", "section": "", "partNumber": "", "partTitle": "", "pages": "65–73", "series": "", "seriesTitle": "", "seriesText": "", "journalAbbreviation": "", "DOI": "10.1002/mrm.1910340111", "citationKey": "", "url": "http://onlinelibrary.wiley.com/doi/10.1002/mrm.1910340111/abstract", "accessDate": "2013-08-14T14:55:19Z", "PMID": "", "PMCID": "", "ISSN": "1522-2594", "archive": "", "archiveLocation": "", "shortTitle": "", "language": "en", "libraryCatalog": "Wiley Online Library", "callNumber": "", "rights": "Copyright © 1995 Wiley-Liss, Inc., A Wiley Company", "extra": "", "tags": [ { "tag": "EPI", "type": 1 }, { "tag": "Geometric distortion", "type": 1 }, { "tag": "echo planar imaging", "type": 1 }, { "tag": "field map correction", "type": 1 } ], "collections": [ "KBCFGVCJ" ], "relations": {}, "dateAdded": "2013-11-07T16:03:59Z", "dateModified": "2013-11-07T16:03:59Z" } } ]