Ultrasound is one of the most widely used modalities in medical imaging.Ultrasound imaging is regularly
for further reading ::http://www.medimaging.jp/whitepaper/750.pdf
used in cardiology,obstetrics, gynecology, abdominal imaging, etc. Its popularity arises from the fact that
it provides high-resolution images without the use of ionizing radiation.It is also mostly non-invasive, although an invasive technique like intra-vascular imaging is also possible. Non-diagnostic use of ultrasound is finding increased use in clinical applications, (e.g., in guiding interventional procedures). There are also novel non-imaging uses of ultrasound like bone densitometer where the ultrasound speed difference is used to measure the depth or width of bones non-invasively.Ultrasound systems are signal processing intensive. With various imaging modalities and different processing requirements in each modality, digital signal processors (DSP) are finding increasing use in such systems. The advent of low power system-on-chip (SOC) with DSP and RISC processors is allowing OEMs to provide portable and low cost systems without compromising the image quality necessary for clinical applications. This white paper introduces ultrasound systems. The focus of this paper is on the signal processing aspects of the ultrasound system . The basic concepts behind ultrasound systems are provided in Section 2. In this section, the components that a modern ultrasound system are based on are provided along with a brief description of ultrasound properties applicable to imaging. Section 3 introduces the ultrasound transducer that forms the basic ultrasound transmission and reception sensor for this imaging mode. Section 4 focuses on front-end processing with special attention to the basics of beamforming using multiple transducer elements. The most commonly used delay and sum (DAS) beamforming is also introduced in this section. Section 5 describes the mid-end processing, which is defined as any processing that is done on each scan line during image acquisition. Section 6 describes the back-end processing of an ultrasound system, which is composed of image enhancement, noise reduction, and display functionalities. Section 7 describes the Doppler mode of operation, which provides a visual display of motion inside the body. Finally, Section 8 briefly introduces the basic concepts used for 3D/4D imaging.