Abstract
This work proposes a proof-of-concept ultrasound blood-flow-monitoring circuit system using a single-element transducer. The circuit system consists of a single-element ultrasonic transducer, an analog interface circuit, and a field-programmable gate array (FPGA). Since the system uses a single-element transducer, an ultrasound image cannot be reconstructed unless scanning with mechanical movement is used. An ultrasound blood-flow monitor basically needs to acquire a Doppler sample volume by positioning a range gate at a vessel region on a scanline. Most recent single-transducer-based ultrasound pulsed-wave Doppler devices rely on a manual adjustment of the range gate to acquire Doppler sample volumes. However, the manual adjustment of the range gate depends on the user’s experience, and it can be time consuming if a transducer is not properly positioned. Thus, automatic range-gate-positioning is more desirable for image-free pulsed-wave Doppler devices. This work proposes a circuit system which includes a new automatic range-gate-positioning scheme. It blindly tracks the position of a blood vessel on a scanline by using the accumulation of Doppler amplitude deviations and a hysteresis slicing function. The proposed range-gate-positioning scheme has been implemented in an FPGA for real-time operation and is based on addition-only computations, except for filter parts to reduce the complexity of computation in the hardware. The proposed blood-flow-monitoring circuit system has been implemented with discrete commercial chips for proof-of-concept purposes. It uses a center frequency of 2 MHz and a system-clock frequency of 20 MHz. The FPGA only utilizes 5.6% of slice look-up-tables (LUTs) for implementation of the range-gate-positioning scheme. For measurements, the circuit system was utilized to interrogate a customized flow phantom model, which included two vessel-mimicking channels. The circuit system successfully acquired Doppler sample volumes by positioning a range gate on a fluid channel. In addition, the estimated Doppler shift frequency shows a good agreement with the theoretical value.
Highlights
Spectral-Doppler-based ultrasound medical devices have the potential to be used for pre-screening various vascular diseases such as diabetes, vascular stenosis, arterial stiffness, and so on
Analog interface circuits consist of a high-voltage (TX) pulser, a transmit/receive (T/R) switch, and analog front-end (AFE) circuit including a transmitter (TX) pulser, a transmit/receive (T/R) switch, and analog front-end (AFE) cirpre-amplifier, an anti-aliasing filter, and an analog-to-digital converter (ADC)
The blood-flow-monitoring circuit system consists of a transducer, an analog interface circuit, and an field-programmable gate array (FPGA)
Summary
Spectral-Doppler-based ultrasound medical devices have the potential to be used for pre-screening various vascular diseases such as diabetes, vascular stenosis, arterial stiffness, and so on. There are various study results showing the pre-diagnosis of vascular diseases by monitoring hemodynamics via ultrasound [1,2,3,4,5,6,7,8]. A spectral Doppler mode, one of the essential imaging modes of commercial medical ultrasound imaging devices, provides a real-time spectrogram of blood flow, so various studies on the pre-diagnosis of vascular diseases can be done by using a commercial imaging device. In the case of portable or wearable ultrasound blood-flow monitors for early diagnosis, a hardware-efficient system implementation to intensively support a spectral Doppler mode is required
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