New beam forming methodologies for fast transoesophageal volumetric cardiac imaging using ultrasound

As cardiovascular diseases remain the leading cause of death worldwide, the scientific community strives to develop advanced diagnostic tools to detect early cardiac dysfunction. Echocardiography has established itself as a major trump in this quest. Novel treatments have also emerged, offering new hope in combating these pathologies. With them, it came the need for new monitoring tools and there again, ultrasound - and especially, transoesophageal echocardiography - appears as an appealing choice. There is, therefore, a clear urge for new echocardiographic methodologies that combine additional clinical value with a reduction of the examination burden, for both the clinician and the patient.

Notably, recent technological breakthroughs have improved echocardiography in the last decade. However, the use of 3-D ultrasound imaging in the clinical environment remains very limited, mainly due to the insufficient spatio-temporal resolution. Although all state-of-the-art clinical systems offer 3-D imaging, their frame rates are currently limited to ~30 Hz. Despite allowing the assessment of global cardiac morphology and motion, this is insufficient to resolve transient phases, which are known to be critical for the cardiac function and exhibit fast myocardial motion or blood flow. Therefore, the full understanding of the cardiac condition requires clinician to acquire multiple 2-D views, which can be obtained at much higher frame rates. However, this significantly prolongs the examination time and increases the complexity of the acquisition and analysis. Creating a tool for the detailed analysis of the heart directly in 3-D would therefore improve the prognostic and diagnostic value of medical ultrasound and, ultimately, contribute to a better clinical outcome for patients.

The present Ph.D. therefore aimed at improving temporal resolution of clinical 3-D echocardiography. Novel beamforming methodologies that could easily be implemented in clinical echocardiographic systems were investigated and their acoustic safety was evaluated. Finally, a scan sequence adapted for the constraints of clinical scanners was proposed and imaging of fast myocardial events was demonstrated in-vivo at 600 Hz.