Focusing the sound waves used in ultrasound devices has always posed a number of technical challenges. However, a new innovation from Germany that gives greater control over the sound waves could lead to far more accurate ultrasound-based tools.
Beamforming is one of the most important features required in state of the art ultrasonic devices. Dynamic focusing, steering, amplitude weighting and controlling the size of the aperture of an array probe are some of the techniques which have been used in the past to achieve this.
In addition, using multiple beams simultaneously shortens the time to acquire one image.
From an R&D point of view, the ideal situation would be to have complete control over the parameters that determine geometry, direction, number and acoustic properties of the sound beams.
This has now been achieved in the digital phased array system (DiPhAS), a new development from the Department of Ultrasound at the Fraunhofer-Institut Fur Biomedizinische Technik.
In the early days of medical ultrasound, physicians only saw shadowy outlines of the structures inside the body. Today's techniques are not only capable of providing still and moving images of very high resolution. They can be used to measure the rate of blood flow or even discern signs of hardening of the arteries: where the walls of the blood vessels have lost their elasticity, the pulsating pressure of the blood only expands them to a minimal extent.
In modern devices, the sound waves are not emitted in a simple conical beam like a loudspeaker but are focused and variably directed by the scanning head.
The beam is reflected when it encounters tissue such as the wall of an artery, and the signals are echoed back to receiving sensors in the scanning head. Signal delay, intensity and direction are analysed by the hard- and software, building an image pixel by pixel and line by line, like a television picture.
However, the ability to detect changes in length of less than one millimetre in real time calls for extreme precision on the part of the ultrasound scanning head and electronics that process the echoed signals DiPhAS.
Peter Weber of the Fraunhofer Institute and the members of his Ultrasound Systems Development research group have been working on a system that allows this beam to be shaped and directed with exceptional flexibility, producing images of unprecedented high resolution.
The difference with DiPhAS lies in its hardware and software which process all signals end to end in digital form, making them very precise and reproducible. The system is capable of recording up to 25 separate images per second. Stored data, such as those of a beating heart, can be retrieved at any time for later evaluation.
