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Three-point Dixon method enables whole-body water and fat imaging of obese subjects
Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för onkologi, radiologi och klinisk immunologi, Enheten för radiologi.
Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för onkologi, radiologi och klinisk immunologi, Enheten för radiologi.
Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för onkologi, radiologi och klinisk immunologi, Enheten för radiologi.
Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för onkologi, radiologi och klinisk immunologi, Enheten för radiologi.
2010 (Engelska)Ingår i: Magnetic Resonance in Medicine, ISSN 0740-3194, E-ISSN 1522-2594, Vol. 63, nr 6, s. 1659-1668Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Dixon imaging techniques derive chemical shift-separated water and fat images, enabling the quantification of fat content and forming an alternative to fat suppression. Whole-body Dixon imaging is of interest in studies of obesity and the metabolic syndrome, and possibly in oncology. A three-point Dixon method is proposed where two solutions are found analytically in each voxel. The true solution is identified by a multiseed three-dimensional region-growing scheme with a dynamic path, allowing confident regions to be solved before unconfident regions, such as background noise. 2 pi-Phase unwrapping is not required. Whole-body datasets (256 x 184 x 252 voxels) were collected from 39 subjects (body mass index 19.8-45.4 kg/m(2)), in a mean scan time of 5 min 15 sec. Water and fat images were reconstructed offline, using the proposed method and two reference methods. The resulting images were subjectively graded on a four-grade scale by two radiologists, blinded to the method used. The proposed method was found superior to the reference methods. It exclusively received the two highest grades, implying that only mild reconstruction failures were found. The computation time for a whole-body dataset was 1 min 51.5 sec +/- 3.0 sec. It was concluded that whole-body water and fat imaging is feasible even for obese subjects, using the proposed method.

Ort, förlag, år, upplaga, sidor
2010. Vol. 63, nr 6, s. 1659-1668
Nyckelord [en]
three-point Dixon, whole-body MRI, water and fat separation, chemical shift imaging, fat suppression
Nationell ämneskategori
Medicin och hälsovetenskap
Identifikatorer
URN: urn:nbn:se:uu:diva-129498DOI: 10.1002/mrm.22385ISI: 000278164400026PubMedID: 20512869OAI: oai:DiVA.org:uu-129498DiVA, id: diva2:344031
Tillgänglig från: 2010-08-17 Skapad: 2010-08-17 Senast uppdaterad: 2017-12-12Bibliografiskt granskad
Ingår i avhandling
1. Separation of Water and Fat Signal in Magnetic Resonance Imaging: Advances in Methods Based on Chemical Shift
Öppna denna publikation i ny flik eller fönster >>Separation of Water and Fat Signal in Magnetic Resonance Imaging: Advances in Methods Based on Chemical Shift
2011 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

Magnetic resonance imaging (MRI) is one of the most important diagnostic tools of modern healthcare. The signal in medical MRI predominantly originates from water and fat molecules. Separation of the two components into water-only and fat-only images can improve diagnosis, and is the premier non-invasive method for measuring the amount and distribution of fatty tissue.

Fat-water imaging (FWI) enables fast fat/water separation by model-based estimation from chemical shift encoded data, such as multi-echo acquisitions. Qualitative FWI is sufficient for visual separation of the components, while quantitative FWI also offers reliable estimates of the fat percentage in each pixel. The major problems of current FWI methods are long acquisition times, long reconstruction times, and reconstruction errors that degrade image quality.

In this thesis, existing FWI methods were reviewed, and novel fully automatic methods were developed and evaluated, with a focus on fast 3D image reconstruction. All MRI data was acquired on standard clinical scanners.

A triple-echo qualitative FWI method was developed for the specific application of 3D whole-body imaging. The method was compared with two reference methods, and demonstrated superior image quality when evaluated in 39 volunteers.

The problem of qualitative FWI by dual-echo data with unconstrained echo times was solved, allowing faster and more flexible image acquisition than conventional FWI. Feasibility of the method was demonstrated in three volunteers and the noise performance was evaluated.

Further, a quantitative multi-echo FWI method was developed. The signal separation was based on discrete whole-image optimization. Fast 3D image reconstruction with few reconstruction errors was demonstrated by abdominal imaging of ten volunteers.

Lastly, a method was proposed for quantitative mapping of average fatty acid chain length and degree of saturation. The method was validated by imaging different oils, using gas-liquid chromatography (GLC) as the reference. The degree of saturation agreed well with GLC, and feasibility of the method was demonstrated in the thigh of a volunteer.

The developed methods have applications in clinical settings, and are already being used in several research projects, including studies of obesity, dietary intervention, and the metabolic syndrome.

Ort, förlag, år, upplaga, sidor
Uppsala: Acta Universitatis Upsaliensis, 2011. s. 85
Serie
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 701
Nyckelord
Magnetic resonance imaging, digital image reconstruction, chemical shift imaging, water and fat separation, Dixon method, fat suppression, quantitative MRI, whole-body MRI, fatty acid composition, fat unsaturation, triglycerides, adipose tissue, liver fat, T2* mapping
Nationell ämneskategori
Klinisk vetenskap
Forskningsämne
Radiologi
Identifikatorer
urn:nbn:se:uu:diva-158111 (URN)978-91-554-8154-4 (ISBN)
Disputation
2011-10-21, Hedstrandsalen, Entrance 70, Uppsala University Hospital, Uppsala, 13:15 (Engelska)
Opponent
Handledare
Tillgänglig från: 2011-09-29 Skapad: 2011-08-31 Senast uppdaterad: 2011-11-03Bibliografiskt granskad

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