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Single Breath Hold Multiple Slice DENSE MRI
Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicin och hälsa, Klinisk fysiologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Hjärtcentrum, Fysiologiska kliniken.
Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicin och hälsa, Klinisk fysiologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Hjärtcentrum, Fysiologiska kliniken.
Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicin och hälsa, Klinisk fysiologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Hjärtcentrum, Fysiologiska kliniken.ORCID-id: 0000-0003-1395-8296
Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicinsk teknik, Medicinsk informatik. Linköpings universitet, Tekniska högskolan.ORCID-id: 0000-0002-9091-4724
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2010 (Engelska)Ingår i: Magnetic Resonance in Medicine, ISSN 0740-3194, E-ISSN 1522-2594, Vol. 63, nr 5, s. 1411-1414Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

A method to acquire multiple displacement encoded slices within asingle breath hold is presented. Efficiency is improved overconventional Displacement ENcoding with Stimulated Echoes (DENSE) without compromising image quality by read-out of multiple slices inthe same cardiac cycle, thus utilizing the position encoded stimulatedecho available in the whole heart. The method was evaluated bycomparing strain values obtained using the proposed method to strainvalues obtained by conventional separate breath hold single-sliceDENSE acquisitions. Good agreement (Lagrangian E2 strainbias=0.000, 95% limits of agreement ±0.04,root-mean-square-difference 0.02 (9.4% of the mean end-systolic E2)) was found between the methods, indicating that the proposedmethod can replace a multiple breath hold acquisition. Eliminating theneed for multiple breath holds reduces the risk of changes in breathhold positions or heart rate, results in higher patient comfort andfacilitates inclusion of DENSE in a clinical routine protocol.

Ort, förlag, år, upplaga, sidor
John Wiley and Sons, Ltd , 2010. Vol. 63, nr 5, s. 1411-1414
Nyckelord [en]
DENSE, strain, multi-slice, breath hold, cardiac function
Nationell ämneskategori
Medicinsk laboratorie- och mätteknik
Identifikatorer
URN: urn:nbn:se:liu:diva-51974DOI: 10.1002/mrm.22305ISI: 000277098100030OAI: oai:DiVA.org:liu-51974DiVA, id: diva2:278375
Tillgänglig från: 2009-11-25 Skapad: 2009-11-25 Senast uppdaterad: 2017-12-12Bibliografiskt granskad
Ingår i avhandling
1. Multidimensional MRI  of Myocardial Dynamics: Acquisition, Reconstruction and Visualization
Öppna denna publikation i ny flik eller fönster >>Multidimensional MRI  of Myocardial Dynamics: Acquisition, Reconstruction and Visualization
2009 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

Methods for measuring deformation and motion of the human heart in-vivo are crucial in the assessment of cardiac function. Applications ranging from basic physiological research, through early detection of disease to follow-up studies, all rely on the quality of the measurements of heart dynamics. This thesis presents new improved magnetic resonance imaging methods for acquisition, image reconstruction and visualization of cardiac motion and deformation.As the heart moves and changes shape during the acquisition, synchronization to the heart dynamics is necessary. Here, a method to resolve not only the cardiac cycle but also the respiratory cycle is presented. Combined with volumetric imaging, this produces a five-dimensional data set with two cyclic temporal dimensions. This type of data reveals unique physiological information, such as interventricular coupling in the heart in different phases of the respiratory cycle.The acquisition can also be sensitized to motion, measuring not only the magnitude of the magnetization but also a signal proportional to local velocity or displacement. This allows for quantification of the motion which is especially suitable for functional study of the cardiac deformation. In this work, an evaluation of the influence of several factors on the signal-to-noise ratio is presented for in-vivo displacement encoded imaging. Additionally, an extension of the method to acquire multiple displacement encoded slices in a single breath hold is also presented.Magnetic resonance imaging is usually associated with long scan times, and many methods exist to shorten the acquisition time while maintaining acceptable image quality. One class of such methods involves acquiring only a sparse subset of k-space. A special reconstruction is then necessary in order to obtain an artifact-free image. One family of these reconstruction techniques tailored for dynamic imaging is the k-t BLAST approach, which incorporates data-driven prior knowledge to suppress aliasing artifacts that otherwise occur with the sparse sampling. In this work, an extension of the original k-t BLAST method to two temporal dimensions is presented and applied to data acquired with full coverage of the cardio-respiratory cycles. Using this technique, termed k-t2 BLAST, simultaneous reduction of scan time and improved spatial resolution is demonstrated. Further, the loss of temporal fidelity when using the k-t BLAST approach is investigated, and an improved reconstruction is proposed for the application of cardiac function analysis.Visualization is a crucial part of the imaging chain. Scalar data, such as regular anatomical images, are straightforward to display. Myocardial strain and strain-rate, however, are tensor quantities which do not lend themselves to direct visualization. The problem of visualizing the tensor field is approached in this work by combining a local visualization that displays all degrees of freedom for a single tensor with an overview visualization using a scalar field representation of the complete tensor field. The scalar field is obtained by iterated adaptive filtering of a noise field, creating a continuous geometrical representation of the myocardial strain-rate tensor field.The results of the work presented in this thesis provide opportunities for improved imaging of myocardial function, in all areas of the imaging chain; acquisition, reconstruction and visualization.

 

Ort, förlag, år, upplaga, sidor
Linköping: Linköping University Electronic Press, 2009. s. 71
Serie
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1287
Nyckelord
MRI, Cardiac motion, myocardial dynamics, strain, tensor, deformation, DENSE, k-t BLAST
Nationell ämneskategori
Medicinsk laboratorie- och mätteknik
Identifikatorer
urn:nbn:se:liu:diva-51489 (URN)978-91-7393-494-7 (ISBN)
Disputation
2009-12-18, Conrad, Campus US, Linköpings Universitet, Linköping, 09:15 (Engelska)
Opponent
Handledare
Tillgänglig från: 2009-11-30 Skapad: 2009-11-04 Senast uppdaterad: 2020-02-19Bibliografiskt granskad
2. Assessment of Myocardial Function using Phase Based Motion Sensitive MRI
Öppna denna publikation i ny flik eller fönster >>Assessment of Myocardial Function using Phase Based Motion Sensitive MRI
2010 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

Quantitative assessment of myocardial function is a valuable tool for clinical applications and physiological studies. This assessment can be acquired using phase based motion sensitive magnetic resonance imaging (MRI) techniques. In this thesis, the accuracy of these phase based motion sensitive MRI techniques is investigated, and modifications in acquisition and post-processing are proposed.

The strain rate of the myocardium can be used to evaluate the myocardial function. However, the estimation of strain rate from the velocity data acquired with phase-contrast MRI (PC-MRI) is sensitive to noise. Estimation using normalized convolution showed, however, to reduce this sensitivity to noise and to minimize the influence of non-myocardial tissue which could impair the result.

Strain of the myocardium is another measure to assess myocardial function. Strain can be estimated from the myocardial displacement acquired with displacement encoding with stimulated echo (DENSE). DENSE acquisition can be realized with several different encoding strategies. The choice of encoding scheme may make the acquisition more or less sensitive to different sources of error. Two potential sources of errors in DENSE acquisition are the influence of the FID and of  the off-resonance effects. Their influence on DENSE were investigated to determine suitable encoding strategies to reduce their influence and thereby improve the measurement accuracy acquired.

The quality of the DENSE measurement is not only dependent on the accuracy, but also the precision of the measurement. The precision is affected by the SNR and thereby depends on flip angle strategies, magnetic field strength and spatial variation of the receiver coil sensitivity. A mutual comparison of their influence on SNR in DENSE was therefore performed and could serve as a guideline to optimize parameters for specific applications.

The acquisition time is often an important factor, especially in clinical applications where it affects potential patient discomfort and patient through-put. A multiple-slice DENSE acquisition was therefore presented, which allows the acquisition of strain values according to the 16-segment cardiac model within a single breath-hold, instead of the conventional three breath-holds.

The DENSE technique can also be adapted toward comprehensive evaluation of the heart in the form of full three-dimensional three-directional acquisition of the displacement. To estimate the full strain tensor from these data, a novel post-processing technique using a polynomial was investigated. The method yielded accurate results on an analytical model and \textit{in-vivo} strains obtained agreed with previously reported myocardial strains in normal volunteers.

Ort, förlag, år, upplaga, sidor
Linköping: Linköping University Electronic Press, 2010. s. 53
Serie
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1341
Nationell ämneskategori
Medicinsk laboratorie- och mätteknik
Identifikatorer
urn:nbn:se:liu:diva-60027 (URN)978-91-7393-302-5 (ISBN)
Disputation
2010-11-12, Conrad, Universitetssjukhuset, Campus US, Linköpings universitet, Linköping, 09:15 (Engelska)
Opponent
Handledare
Tillgänglig från: 2010-11-16 Skapad: 2010-10-04 Senast uppdaterad: 2020-02-19Bibliografiskt granskad

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