Miller, Justin (2010) Design of a wireless acquisition system for a digital stethoscope. [Thesis (PhD/Research)]
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The auscultation of the heart with a stethoscope is one of the most common methods employed by physicians to diagnose cardiovascular and respiratory illnesses. Phonocardiography refers to the technique of acquiring and recording of heart sound signals. The emergence of teleheath and electronic stethoscope technology has opened new opportunities for rural and regional medical services including the remote screening of heart murmurs.
This dissertation investigates the design and implementation of a wireless data acquisition module to capture auscultation sounds from an electronic stethoscope, and sets the foundation for further research into the area of remote auscultation diagnosis and non-invasive techniques for diagnosing abnormalities.
Methods to detect activity in the signal are evaluated for the suppression of ambient noise and adaptive gain control. Several well known noise reduction techniques for signals acquired from a single source are studied and evaluated. A PI controller is developed to control the gain of the input stage to account for attenuation of the heart and respiratory sounds caused by volume effects (i.e. absorption) of the human body.
The acquisition module is controlled by a 16bit dsPic digital signal controller which samples auscultation signals from a digital stethoscope and streams the auscultation signals to the host over a wireless Bluetooth connection. The signal and power supply is isolated for compliance with the international standards for medical devices (IEC 60601-1). A Windows application incorporating a Bluetooth client was developed to receive incoming data packets from the acquisition module and display the signal graphically.
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