A “bar chart” tissue phantom fabrication for the system-independent assessment of OCT axial resolution

We present a novel optical phantom fabrication approach for the characterization of optical coherent tomography (OCT) axial resolution and contrast via multilayered “bar charts.”  We explore two methods to fabricate these phantoms: the first is based on a combinatorial methods approach from polymer science to incorporate monolayers of light-scattering microspheres with an intervening layer of transparent silicone, and the second involves alternating layers of scattering-enhanced silicone and transparent silicone.  Varying the diameter of the microspheres and/or the thickness of the silicone layers permits different spatial frequencies to be realized in the axial dimension of the phantoms.  The physical dimensions of the phantom are measured with a stylus profilometer calibrated to a known standard. Because the phantom’s dimensions are accurately known independent of the OCT system, no information about the system’s spatial calibration is required.   We quantified the degree to which the bars in each phantom could be resolved with OCT, thereby providing insights into the axial contrast transfer function.