  Spatial frequency domain imaging (SFDI) is a low-cost imaging technique that
can deliver real-time maps of absorption and reduced scattering coefficients.
However, there are a wide range of imaging geometries that practical SFDI
systems must cope with including imaging flat samples ex vivo, imaging inside
tubular lumen in vivo such as in an endoscopy, and measuring tumours or polyps
of varying shapes, sizes and optical properties. There is a need for a design
and simulation tool to accelerate design and fabrication of new SFDI systems.
We present such a system implemented using open-source 3D design and
ray-tracing software Blender that is capable of simulating media with realistic
optical properties (mimicking healthy and cancerous tissue), a wide variety of
shapes and size, and in both planar and tubular imaging geometries. We first
demonstrate quantitative agreement between Monte-Carlo simulated scattering and
absorption coefficients and those measured from our Blender system. Next, we
show the ability of the system to simulate absorption, scattering and shape for
flat samples with small simulated tumours and show that the improved contrast
associated with SFDI is reproduced. Finally, to demonstrate the versatility of
the system as a design tool we show that it can be used to generate a custom
look-up-table for mapping from modulation amplitude values to absorption and
scattering values in a tubular geometry, simulating a lumen. As a demonstrative
example we show that longitudinal sectioning of the tube, with separate look-up
tables for each section, significantly improves accuracy of SFDI, representing
an important design insight for future systems. We therefore anticipate our
simulation system will significantly aid in the design and development of novel
SFDI systems, especially as such systems are miniaturised for deployment in
endoscopic and laparoscopic systems.
