Synchronisation of vascular ultrasonic scans with heart activity using ECG signals

Bener, Omer Faruk (2010) Synchronisation of vascular ultrasonic scans with heart activity using ECG signals. MPhil thesis, University of Nottingham.

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Abstract

Diagnosis, monitoring and curing of various vascular abnormalities can be linked to measurements of wall thicknesses of blood vessels. However, use of echo ultrasonic signals for these measurement is complicated by the low level of reflections from the vessels (1-2% from the incident energy), which results in considerable noise. Since the changes in thickness to be monitored are very small, this requires operation of ultrasonic scanners at high sampling frequencies, much higher than 50–100 MHz sampling frequencies that are used by contemporary ultrasonic scanners. That is because the resolution of the measured thickness is dependent on the time domain resolution of the recorded echoes; the latter is determined by the sampling frequency. An additional issue is the variability in the blood vessel wall thickness depending on the phase of the heart activity. Several studies show that these variations with a cycle time of around one second result in the same changes as building atherosclerosis for one year.

The objective of the study was to develop an instrument that would allows recording of ultrasonic A-scans that are synchronised with the heart activity and that would allow improved accuracy of wall thickness measurements. Using an electronics point of view, the objective was met by the simulation, construction, programming and testing of an ECG monitor that triggers ultrasonic scans. The FPGA design of an existing high accuracy ultrasonic A-mode scanner was modified to allow interfacing of this monitor. Ultrasonic scans were taken with different transducers and transducer attachments (“shoes”) using various settings of the scanner. The scans were then analysed using dedicated Matlab programs.

Overall, the design proved to be successful – it allowed repeatable records to be obtained at the same stage of heart activity. However, reliable and unambiguous detection of the artery walls (especially the back wall) was achieved only sporadically within the time available for in vivo experiments.

Item Type:Thesis (MPhil)
Supervisors:Kalashnikov, A.
Hayes-Gill, B.R.
Faculties/Schools:UK Campuses > Faculty of Engineering > Department of Electrical and Electronic Engineering
ID Code:1640
Deposited By:Mr Omer Faruk Bener
Deposited On:18 May 2011 11:49
Last Modified:18 May 2011 11:49

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