Inspection and Testing of Diagnostic Ultrasound Devices

This chapter provides an overview of the safety aspects of application of ultrasound in medicine. It begins with the short history of ultrasound methods and devices as well as basic principles of ultrasound imaging systems. The application of ultrasound in medicine has highly evolved and nowadays it can be divided into two main areas: imaging and therapy. To assure quality, safe use and responsible application of ultrasound in medicine one should be aware of physical processes which can be produced in tissue by ultrasound such as temperature rise, cavitation, and acoustic streaming. The importance of understanding how these processes can affect the human cell is self-explanatory. To better understand the guidelines for testing and quality control of ultrasonic devices it is necessary to provide an overview of basic output parameters. Only the most important parameters from the point of safe use of ultrasound are described, e.g., acoustic pressure, acoustic power and intensity. To protect the public against inappropriate exposure when ultrasound is used for medical applications, international standards and national regulations are developed. Diagnostic ultrasound imaging is very often the basis for diagnostic decision; therefore, it is also necessary to include such systems into a comprehensive quality assurance programme. Ultrasound systems used for therapy have larger intensities though there are additional safety requirements compared to diagnostic systems. The ultrasound intensity, effective radiation area and beam non-uniformity ratio and are parameters which should be monitored.