Ultrasound is widely used for medical imaging and increasingly in therapeutic applications for example in the treatment of cancer. However, tissue inhomogeneity can affect the accuracy with which ultrasound can be focused in the body. This is particularly problematic in applications in which high intensity ultrasound is used.

One solution to this that has been implemented in a small number of commercial ultrasound systems is to use an array transducer to enable “steering” of the ultrasound beam. This approach, however, greatly increases the cost and complexity of the system and individual treatments. An alternative is to use patient-specific acoustic lenses that can be fitted to simpler ultrasound systems.

Scientists at the University of Oxford have developed an alternative to conventional acoustic lenses in the form of a grid of acoustic wave guides. The grids can be manufactured rapidly (< 1 hour) and at very low cost (<£20) and may be easily integrated into clinical ultrasound systems.

They offer efficient modulation of the phase and amplitude of the transmitted sound field, enabling the required exposure conditions within the target tissue. The method may also be of interest for other applications where ultrasound lenses are used, such as for non-destructive testing, or underwater imaging.