3D-Printed Phantom Fabricated by Photopolymer Jetting Technology for High-Frequency Ultrasound Imaging

In the field of high-frequency ultrasound imaging (≥ 20 MHz), tools for characterizing the performance of imaging systems are lacking. Indeed, commercial phantoms are often inad- equate for this frequency range. The development of homemade phantoms on the laboratory scale is often required but is hindered by the difficulty in making very small structures that must be distributed with high accuracy in three-dimensional space. We propose investigating the use of 3D photopolymer printing to create resolution and calibration phantoms designed for high- frequency ultrasound imaging. The quality and importance of these phantoms are discussed from the point of view of ultrasound parameters and imaging. First, the compressional wave group velocity, acoustic impedance and attenuation of six photopoly- merized materials were measured using temporal and spectral methods in a substitution experimental setup. Measurements were performed on printed samples using a broadband focused single-element transducer covering a large frequency range (15- 55 MHz). Two 3D phantoms incorporating different shapes and dimensions were designed and printed. Finally, 3D acoustic images were obtained using either a mechanically driven single- element transducer or a high-frequency commercial imaging system. 3D printing enabled us to generate phantoms suitable for high-frequency imaging with complex geometry inclusions and with a surrounding material having acoustic properties close to those of human skin. The calculated SNR between the inclusion and surrounding media is approximately 50 dB. In conclusion, 3D printing is a useful tool for directly, easily and rapidly manufacturing ultrasound phantoms for ultrasound imaging system assessments and computational calibration or validation