Full 3D Blood Velocity Mapping and Flow Quantification from Doppler Echocardiographic Images

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

Name dc:type.qualificationname

Doctor of Philosophy

Level dc:type.qualificationlevel

Doctoral Thesis

Grantor dc:publisher.institution

King's College London

Year dc:date.issued

2013

Author dc:creator

• Gomez, Alberto

Advisors dc:contributor.advisor

• Schaeffter, Tobias Richard
• Penney, Graeme Patrick

• Echo
• Doppler
• Flow
• 3D echo

Language dc:language

eng

Identifier

oai:kclpure.kcl.ac.uk:studenttheses/f6a945d7-3a8e-4458-91c8-377ce3202119

OAI identifier oai:identifier

oai:kclpure.kcl.ac.uk:studenttheses/f6a945d7-3a8e-4458-91c8-377ce3202119