This thesis contributes to knowledge by describing two novel methods to calculate 3D blood velocity and flow within the heart using 3D colour Doppler images. The principal goal of both methods was to overcome the main limitation of Doppler systems which is that the Doppler effect only measures one component of the velocity (parallel to the beam direction). For that reason, measured velocity and calculated flow depend on the angle between the beam direction and the flow. The first method was developed to reconstruct 3D intracardiac velocity vector fields. This is the first time that such vector fields have been obtained from 3D colour Doppler images. The novelty of the proposal lies not only in the 3D velocity reconstruction, but also 1) a new noise model for colour Doppler images was proposed which improves the realism of simulation studies, 2) an efficient patch-wise implementation was introduced and 3) ventricle wall motion was used to enable full ventricular coverage. Based on simulations minimum acquisition requirements for accurate reconstruction were established. These requirements were: view angles over 20 degrees and noise below 10% of the Doppler maximum velocity. The method was tested on healthy volunteers and on paediatric patients and an accuracy of 15% compared to flow Magnetic Resonance Imaging (MRI) was obtained, when acquisition and data conditions were close to the optimum range. The second method proposes an algorithm to calculate angle-independent flow rates through surfaces within the heart and vessels. Built on the Gauss’s theorem, this method enables to increase coverage beyond the Field of View (FoV) of individual colour Doppler images by combining images acquired from multiple views. The method was validated in patients with Hypoplastic Left Heart Syndrome. Results were compared with the current clinical gold standard measurement of flow MRI, agreeing on flow values and volumes to less than 10%. The novel methods proposed in this thesis have shown encouraging results using volunteer and patient data. I hope that the methods proposed will in the future be able to offer advanced flow measurements using echo. The ability to improve the information available from echo imaging, due to its ease of use and cost effective nature, has the potential for widespread improvements in clinical care.

Ekokardiografi (EKO) är en vanlig metod som används för bedömning och uppföljning av eventuella hjärtsjukdomar. Idag är tvådimensionell (2D) EKO standardmetoden för bestämning av slutdiastolisk volym (EDV), slutsystolisk volym (ESV) och ejektionsfraktionen (EF). Tredimensionell (3D) EKO har börjat användas mer kliniskt för bestämning av EDV, ESV och EF. Idag används två olika 3D mjukvaruprogram, Tomtec som är helautomatiserad och Dynamic Heart Model (DHM) som även den är helautomatiserad. Dessa används för bestämning av EDV, ESV och EF. Syftet med undersökningen var att jämföra två olika 3D-mjukvaruprogram, Tomtec samt DHM, för bestämning av EF och vänsterkammarvolymer (EDV och ESV). Dessa jämförs även med 2D som idag är standardmetod för värdering av både volymer och EF. Det erhölls signifikanta skillnader mellan programmen Tomtec och DHM, där högre volymer uppmättes med DHM. I jämförelse med 2D påvisades även signifikant större volymer med 3D (Tomtec och DHM). Resultatet från korrelationsanalysen visade en mycket hög korrelation mellan Tomtec och DHM för EDV, ESV och EF. Även en hög korrelation mellan 3D och 2D för bestämning av EDV, ESV och EF förelåg. Detta bekräftades med Bland Altman analyserna som visade goda överenstämmelser mellan Tomtec och DHM, samt mellan 3D och 2D. Överenstämmelserna mellan metoderna var hög. Mjukvaruprogrammen Tomtec och DHM stämmer väl överens med varandra och med 2D EKO. Skillnaden beror sannolikt på att Tomtec, DHM och 2D bygger på olika metodiker, däremot är denna skillnad obetydlig vid klinisk användning. / Echocardiography (ECHO) is a common method used for assessment and follow-up of possible heart diseases. Today, two-dimensional (2D) ECHO is the standard method for determining end-diastolic volume (EDV), end-systolic volume (ESV) and ejection fraction (EF). Currently, three-dimensional (3D) ECHO is used more clinically for the determination of EDV, ESV and EF. Two different 3D software are used today, Tomtec which is a fully automated method and Dynamic Heart Model (DHM) which is also a fully automated method. These are used to determine EDV, ESV and EF. The aim of the study was to compare two different 3D softwares, Tomtec and DHM, for assessment of EF and left ventricular volumes (EDV and ESV). These are also compared to 2D, which currently is the standard method for assessing both volumes and EF. Significant differences were seen between the Tomtec and DHM software, where higher volumes were measured with DHM.  In comparison with 2D, significantly larger volumes were obtained with 3D (Tomtec and DHM). The result from the correlation analysis showed very high correlation between Tomtec and DHM for EDV, ESV and EF. High correlation between 3D and 2D for determination of EDV, ESV and EF was present. This was confirmed with the Bland Altman analyses, which showed good agreement between Tomtec and DHM, as well as between 3D and 2D. Agreements between the methods were high. The Tomtec and DHM softwares showed good agreement as well as with 2D ECHO. The significant difference is probably because Tomtec, DHM and 2D are based on different methodologies, although in clinical practice this difference is of minor relevance.