Hardware-Software Partitioning of Digital Signal Processing in Ultrasound Medical Devices a Case Study

The development of ultrasound devices and diagnostic methods is closely related with the development of microelectronics and digital signal processing. In most of the state of the art electronic devices, the signal is digitally processed. These devices may be generally categorized based on the number of parallel processing channels. Imaging devices with multi-element linear or phased arrays usually have 16-256 transmission/reception channels. Single channel processing is usually performed in imaging devices with mechanically moved single element sector heads, the so-called “wobbler” and in dedicated Doppler devices. The methods of signal processing are much the same in all device categories. The paper presents a general overview of ultrasound signal processing and its digital implementation with emphasis on hardware-software partitioning. The available state of the art methods and systems of digital signal processing using both hardware and software are presented as well as the issues pertaining to algorithm implementation methodology. The state of the art system solutions are presented based on the descriptions of representative ultrasound devices, found in literature. The similarities between the presented devices and radio signal processing systems used in telecommunication are also discussed in the paper. Based on device description, the authors present the architecture of processing and communication as well as specific design solutions. The discussed issues and system solutions are analyzed based on two ultrasound medical devices, namely: • uScan high frequency ultrasonograph with coded transmission (Lewandowski & Nowicki, 2008), • digiTDS transcranial Doppler system (Lewandowski et al., 2009). Both devices have been designed and built by the author and co-workers at the Institute of Fundamental Technological Research, Polish Academy of Sciences. They have been designed for commercial purposes, in conformity with medical standards and economic limitations. The analysis of the presented solution comprises: • description of the presented systems architecture and of the processing algorithm implementation, • decisions concerning the design and hardware-software partitioning.