3D-printable phantoms for quantitative dynamic contrast-enhanced MRI

A novel 3D-printed phantom design and methodology are proposed, addressing important requirements for technical validation, quality assurance, and multi-site harmonization of quantitative DCE-MRI measurements.

Phantoms were produced by 3D-printing (3DP) gels incorporating channels and pores as proxies for blood vessels and extravascular extracellular space, respectively. A flow circuit was designed to reproduce clinically relevant arterial input functions. Using nine gels with variable porosity and channel size, we evaluated the effect of 3DP parameters on DCE-MRI parameters obtained using the extended Tofts model (ET). Physical gel and fitted model parameters were correlated by multiple linear regression.

All phantoms generated realistic arterial input functions, and tissue-like signal enhancement curves were accurately modeled by the ET model. As hypothesized, blood plasma volume fraction, v_p, was positively associated with the channel volume fraction, v_chan, (B = 0.86, p < 0.001) and showed a weaker, negative association with gel porosity, v_pore, (B = -0.18, p = 0.006). Vascular permeability-surface area product, PS, was positively associated with both v_chan (B = 0.13 min^-1, p < 0.001); and v_pore (B = 0.051 min^-1, p < 0.001). The extravascular extracellular space (EES) volume fraction, v_e, was positively associated with v_pore (B = 0.90, p < 0.001) but not v_chan. Fitted parameters were reproducible (coefficient of variation 2.1%-3.2%).

Tailorable 3D-printed porous gel phantoms generating tissue-mimicking DCE-MRI signals have the potential to support validation, quality assurance, and multi-site harmonization of quantitative DCE-MRI.