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Influence of the FID and off-resonance effects in dense MRI
Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicin och hälsa, Klinisk fysiologi. Linköpings universitet, Hälsouniversitetet.
Linköpings universitet, Institutionen för medicin och hälsa, Klinisk fysiologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Hjärtcentrum, Fysiologiska kliniken.
(Department of Radiology, Mie University, Japan)
Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicin och hälsa, Klinisk fysiologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Hjärt- och Medicincentrum, Fysiologiska kliniken US.
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2011 (Engelska)Ingår i: Magnetic Resonance in Medicine, ISSN 0740-3194, E-ISSN 1522-2594, Vol. 65, nr 4, s. 1104-1112Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Accurate functional measurement in cardiovascular diseases is important as inaccuracy may compromise diagnostic decisions. Cardiac function can be assessed using displacement encoding with stimulated echoes, resulting in three signal components. The free induction decay (FID), arising from spins undergoing T1-relaxation, is not displacement encoded and impairs the displacement acquired. Techniques for suppressing the FID exist; however, a residual will remain. The effect of the residual is difficult to distinguish and investigate in vitro and in vivo. In this work, the influence of the FID as well as of off-resonance effects is evaluated by altering the phase of the FID in relation to the stimulated echo. The results show that the FID and off-resonance effects can impair the accuracy of the displacement measurement acquired. The influence of the FID can be avoided by using an encoded reference. We therefore recommend the assessment of this influence of the FID for each displacement encoding with stimulated echoes protocol.

Ort, förlag, år, upplaga, sidor
Wiley , 2011. Vol. 65, nr 4, s. 1104-1112
Nationell ämneskategori
Medicin och hälsovetenskap
Identifikatorer
URN: urn:nbn:se:liu:diva-60266DOI: 10.1002/mrm.22692ISI: 000288612000023OAI: oai:DiVA.org:liu-60266DiVA, id: diva2:355899
Tillgänglig från: 2010-10-08 Skapad: 2010-10-08 Senast uppdaterad: 2017-12-12
Ingår i avhandling
1. 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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Haraldsson, HenrikSigfridsson, AndreasEngvall, JanEbbers, Tino

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