Development of Vessel Phantoms for Ultrasound Methods

Sammanfattning: Phantoms mimicking the specific mechanical and acoustic properties of human tissues are essential in the development and evaluation of novel ultrasound methods. In this work, various ultrasound phantoms are proposed to be used in the development of ultrasound methods to investigate the arterial walls longitudinal movements influence on the vasa vasorum circulation. The longitudinal movement of arteries has been shown in vivio. It has been measured to be of the same magnitude as the diameter change of the arteries. Ultrasound phantoms simulating the arterial longitudinal movement has recently been made using Polyvinyl alcohol (PVA). However, these phantoms suffered from having low temporal stability and easy degradation. This master’s thesis investigates several tissues mimicking materials and describes the design and fabrication of ultrasound phantom models that simulate the vasa vasorum (the vessels of the vessel) and the longitudinal movement of the arterial wall. The mechanical properties of phantom materials were evaluated with a mechanical test instrument and the speed of sound was measured using a method based on the time of flight, and the attenuation was also measured. We showed that copolymer-in-oil, as well as ballistic gel, are excellent alternatives for vessel phantom fabrication. The Young’s modulus for copolymer in oil and ballistic gel was measured to be 37 and 82 kPa, respectively. The attenuation coefficients were 0.83 and 0.40 dB/MHz/cm, respectively. The ultrasound speed ranged from 1433–1458 m/s. The results suggest that the best alternative is to use the commercially available styrene-ethylene/butylene-styrene (SEBS) block copolymer in mineral oil, and the clear synthetic ballistics gelatin of 10%. A walled and multi-layered vessel phantom in a cylindrical geometry and with decreasing diameter was designed and fabricated. The longitudinal and radial movements were generated by the use of pulsatile flow produced from a gear pump. The longitudinal movement was measured to 0.2 mm and the radial movement to 0.8 mm.