Abstract
Modern ultrasound (US) imaging is increasing its clinical impact, particularly with the introduction of US-based quantitative imaging biomarkers. Continued development and validation of such novel imaging approaches requires imaging phantoms that recapitulate the underlying anatomy and pathology of interest. However, current US phantom designs are generally too simplistic to emulate the structure and variability of the human body. Therefore, there is a need to create a platform that is capable of generating well-characterized phantoms that can mimic the basic anatomical, functional, and mechanical properties of native tissues and pathologies. Using a 3D-printing technique based on stereolithography, we fabricated US phantoms using soft materials in a single fabrication session, without the need for material casting or back-filling. With this technique, we induced variable levels of stable US backscatter in our printed materials in anatomically relevant 3D patterns. Additionally, we controlled phantom stiffness from 7 to >120 kPa at the voxel level to generate isotropic and anisotropic phantoms for elasticity imaging. Lastly, we demonstrated the fabrication of channels with diameters as small as 60 micrometers and with complex geometry (e.g., tortuosity) capable of supporting blood-mimicking fluid flow. Collectively, these results show that projection-based stereolithography allows for customizable fabrication of complex US phantoms.
Highlights
Ultrasound (US) imaging has long been a valuable tool for medical diagnostics due to its noninvasive nature, high resolution, dynamic-imaging capabilities, and its capacity to assess tissue properties beyond simple anatomy [1]
In B-mode images of matched phantoms, these exposure discontinuities were aligned with the US scattering generated at each layer boundary (Fig 3C), demonstrating that the “stacking” of photocured layers that occurs with extrusion printing produces local density discontinuities that result in hyperechoic regions
For phantoms printed with 50-μm layers, the printlayer boundaries were spatially averaged even using a 50-MHz center frequency, and they were indistinguishable at 12 MHz (S2 Fig), indicating that such print-voxel size is well suited for fabricating phantoms intended for more typical clinical US frequencies (i.e.,
Summary
Ultrasound (US) imaging has long been a valuable tool for medical diagnostics due to its noninvasive nature, high resolution, dynamic-imaging capabilities, and its capacity to assess tissue properties beyond simple anatomy (e.g., blood flow or tissue stiffness) [1].
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