BioSono provides a cyberspace (www.biosono.com) where researchers, engineers, and students can find useful reference and educational materials, conduct acoustic simulation, post questions on design and development, and get answers. The online KLM based transducer acoustic stack simulation, which is currently free, can help you choose piezoelectric, matching and backing material, and a tuning electrical network. The output from the model includes electrical transmit impedance, acoustic receive impedance, and the impulse or pulse-echo response. The ultrasound beam profile simulation provides the calculated transmitted ultrasound pressure field under certain excitation for a given transducer aperture in a number of different geometrical configurations, including circular elements (flat and concave piston), rectangular elements, linear arrays, convex arrays, and 2D arrays. The simulation is based on Field II, which is a free program that utilizes the spatial impulse response method, and has been validated by many researchers for accuracy. In addition to the web based acoustic simulation, we also provide pulse-echo system, transducers, and customized design and develop services.
Transducer KLM Model Simulation
Beam Profile Simulation
SonoLab Echo I
Time Gain Control
Ultrasound Time-Gain-Compensation (TGC)
Ultrasound imaging is based on pulse-echo method. The transmitted acoustic pulse will lose its energy due to two main factors: beam spread and attenuation. As shown in Fig. 1, along the axial axis through the center of a piston transducer, the beam will reach its maximum at certain depth and then decrease monotonously. How fast it decreases is determined by the geometry and bandwidth of the transducer, and frequency and bandwidth of the excitation pulse.
The echo signal will decrease in the same way even if the tissue structure is the same. The gain for the echo has to increase with depth to maintain a uniform brightness of the image from near field to far field. Soft tissue has an attenuation of about 0.3dB/MHz/cm to the acoustic pulse. The Time-Gain-Compensation (TGC) has to compensate the lose from both of beam spread and attenuation.
The TGC amplifier usually is a variable gain amplifier with gain controlled by a TGC voltage curve. The curve can be generated by an analog oscillation circuit or a digital curve through DAC, triggered by the pulse transmit signal.
The most simple TGC curve is a saw-tooth curve with adjustable slope. For most imaging system, TGC curve is adjustable independently for each depth segments such as 1cm at 5MHz.
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