Material Development for Ultrasound Quality Assurance

Abstract

Ultrasound transducers are usually the weakest point in an ultrasonic device. Malfunction in the transducer can cause distortion in an ultrasound image. Ultrasonic devices should therefore be checked in a regular basis to prevent the usage of broken devices although there are no necessary standards for ultrasound quality assurance. Progress is slow because ultrasound is considered as a safe imaging method, which doesn’t need such accurate supervision. Studies have shown that there are several ultrasonic devices in use, which have some kind of malfunction. With the quality assurance phantom, the operation ability of ultrasonic devices and especially the functionality of the transducer can be improved via testing transducers regularly. Phantoms in clinical use are usually meant to mimic the human body or properties of tissues. Phantoms are used in studies, tests and trainings where in vivo models are inappropriate.

The main objective of this thesis is to study the materials, which are used in ultrasound phantoms, and to study the functionality of materials for the application. The most common materials used in phantom materials are gelatin and agar. These materials are of animal origin and they are exposed to bacterial growth easily, which shortens their lifetime. Other materials are polymer based like polyurethane, polyvinyl alcohol and polyacrylamide. All materials mentioned are water-based, which cause hydration. Materials usually retain their acoustical properties only a few months, some couple of years. There are commercially available ultrasound phantoms but they are expensive.

Therefore new materials, which would be more stable and cheaper of a price, were studied for ultrasound quality assurance. Study of more stable materials was started with silicones, which do not show property changes during a long period of time. However, the acoustical properties of silicones are not suitable for ultrasound phantom application. Next step was to study the acoustical properties of experimental material. The properties turned out suitable for the ultrasound phantom application. Study of this material was carried out and different concentrations of experimental material were tested. The experimental material still needs further studies to be able to be used as the ultrasound phantom