Patient-specific tissue-mimicking phantoms for photoacoustic and ultrasound imaging (Conference Presentation)

Phantoms are crucial for developing photoacoustic imaging systems and for training practitioners. Advances in 3D printing technology have allowed for the generation of detailed moulds for tissue-mimicking materials that represent anatomically realistic tissue structures such as blood vessels. Here, we present methods to generate phantoms for photoacoustic and ultrasound imaging based on patient-specific anatomy and mineral oil based compounds as tissue-mimicking materials. Moulds were created using a 3D printer with fused deposition modelling. Optical and acoustic properties were independently tuned to match different soft tissue types using additives: inorganic dyes for optical absorption, TiO2 particles for optical scattering, paraffin wax for acoustic attenuation, and solid glass spheres for acoustic backscattering. Melted mineral oil compounds with additives were poured into the 3D printed moulds to fabricate different anatomical structures. Optical absorption and reduced scattering coefficients across the wavelength range of 400 to 1600 nm were measured using a spectrophotometer with an integrating sphere, and inverse adding-doubling. The acoustic attenuation and speed-of-sound were measured in reflection mode using a 10 MHz transducer. Three phantoms were created to represent nerves and adjacent blood vessels, a human placenta obtained after caesarean section, and a human heart based on an MRI image volume. Co-registered multi-wavelength photoacoustic and ultrasound images were acquired with a system that comprised a clinical ultrasound imaging scanner, an optical parametric oscillator, and linear-array ultrasound imaging probes. We conclude that mineral oil based compounds can be well suited to create anatomically-realistic phantoms for photoacoustic and ultrasound imaging using 3D printed moulds.