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dc.contributor.advisorTorp, Hansnb_NO
dc.contributor.authorHergum, Torbjørnnb_NO
dc.date.accessioned2014-12-19T14:23:28Z
dc.date.available2014-12-19T14:23:28Z
dc.date.created2009-09-02nb_NO
dc.date.issued2009nb_NO
dc.identifier233818nb_NO
dc.identifier.isbn978-82-471-1656-2nb_NO
dc.identifier.isbn978-82-471-1656-6nb_NO
dc.identifier.urihttp://hdl.handle.net/11250/264654
dc.description.abstractMedical ultrasound imaging is widely used to diagnose cardiacdiseases. The recent availability of real time 3D ultrasound posesseveral interesting challenges and opportunities, and the work of thisthesis is devoted to both challenges and opportunities. One of the key benefits of ultrasound imaging is that its images arereal time. This has been challenged with the recent introduction of 3Dimages, where the number of ultrasound beams is squared compared totraditional 2D images. One common way to alleviate this is byreceiving several closely spaced ultrasound beams from each pulsetransmission, which increases acquisition speed but affects the imagequality. Specifically, B-mode images are irregularly sampled and losespatial shift invariance while a bias in the Doppler velocityestimates causes a discontinuity in the velocity estimates in colorflow images. We have found that these artifacts can be reducedsignificantly by interpolation of the beamformed data from overlappingbeams, with the limitation of requiring at least twice the number ofbeamformers. We have also found that valvular regurgitation is one of thecardiac diseases that can benefit greatly from quantification ofseverity using 3D ultrasound. We have devised a modality that useshigh pulse repetition frequency 3D Doppler to isolate thebackscattered signal power from the vena contracta of a regurgitantjet. This measure is calibrated with a narrow reference beam insidethe jet to estimate the cross-sectional area of the vena contracta. Wehave validated this method with computer simulations, with an in vitrostudy and finally in vivo with 27 patients who had mitralregurgitation. We found that the cross-sectional area and regurgitantvolume of the vena contracta could be quantified without bias as long as the orifice was sufficiently large for a calibration beam tofit inside it. The severity of smaller regurgitations will beoverestimated, but this does not pose a clinical problem, as thesepatients can easily be identified by standard 2D Doppler examination and donot typically need further quantification. Finally, we have developed a new, fast 3D ultrasound simulation methodthat can incorporate anisotropic scattering from cardiac muscle cells. This approach is three orders of magnitudefaster than the most commonly used simulation methods, making it wellsuited for the simulation of dynamic 3D images for development and testingof quantitative diagnostic methods such as 3D speckle tracking andvolumetric measurements.nb_NO
dc.languageengnb_NO
dc.publisherNTNUnb_NO
dc.relation.ispartofseriesDoctoral Theses at NTNU, 1503-8181; 2009:135nb_NO
dc.relation.haspartHergum, Torbjørn; Bjåstad, Tore; Kristoffersen, Kjell; Torp, Hans. Parallel beamforming using synthetic transmit beams.. IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control. (ISSN 0885-3010). 54(2): 271-280, 2007. <a href='http://dx.doi.org/10.1109/ULTSYM.2008.0319'>10.1109/ULTSYM.2008.0319</a>. <a href='http://www.ncbi.nlm.nih.gov/pubmed/17328324'>17328324</a>.nb_NO
dc.relation.haspartHergum, Torbjørn; Bjåstad, Tore; Løvstakken, Lasse; Kristoffersen, Kjell; Torp, Hans. Reducing Color Flow Artifacts caused by Parallel Beam Acquisition. IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control. (ISSN 0885-3010). 57(4): 830-838, 2010. <a href='http://dx.doi.org/10.1109/TUFFC.2010.1488'>10.1109/TUFFC.2010.1488</a>.nb_NO
dc.relation.haspartHergum, Torbjørn; Skaug, Thomas Renhult; Matre, Knut; Torp, Hans. Quantification of valvular regurgitation area and geometry using HPRF 3-D Doppler.. IEEE transactions on ultrasonics, ferroelectrics, and frequency control. (ISSN 1525-8955). 56(5): 975-82, 2009. <a href='http://dx.doi.org/10.1109/TUFFC.2009.1129'>10.1109/TUFFC.2009.1129</a>. <a href='http://www.ncbi.nlm.nih.gov/pubmed/19473915'>19473915</a>.nb_NO
dc.relation.haspartSkaug, Thomas R; Hergum, Torbjørn; Amundsen, Brage H; Skjaerpe, Terje; Torp, Hans; Haugen, Bjørn Olav. Quantification of mitral regurgitation using high pulse repetition frequency three-dimensional color Doppler.. Journal of the American Society of Echocardiography. (ISSN 0894-7317). 23(1): 1-8, 2010. <a href='http://dx.doi.org/10.1016/j.echo.2009.10.005'>10.1016/j.echo.2009.10.005</a>. <a href='http://www.ncbi.nlm.nih.gov/pubmed/19914037'>19914037</a>.nb_NO
dc.subjectultrasounden_GB
dc.subjectDoppleren_GB
dc.subjectechocardiographyen_GB
dc.subjectbeamformingen_GB
dc.title3D Ultrasound for Quantitative Echocardiographynb_NO
dc.typeDoctoral thesisnb_NO
dc.source.pagenumber145nb_NO
dc.contributor.departmentNorges teknisk-naturvitenskapelige universitet, Det medisinske fakultet, Institutt for sirkulasjon og bildediagnostikknb_NO
dc.description.degreePhD i medisinsk teknologinb_NO
dc.description.degreePhD in Medical Technologyen_GB


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