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Phantoms for polarized light exhibiting controllable scattering, birefringence, and optical activity

Recently, the use of polarized light for medical diagnosis and therapeutic management has seen increased interest due the noninvasive nature of light-tissue interactions. Examples of the use of polarized light include polarization imaging to enhance spatial resolution in turbid media, selective imaging of polarized light to increase surface contrast in tissue, polarization-sensitive optical coherence tomography (PS-OCT), and glucose monitoring. With these emerging applications there is a need for controllable phantoms to validate the emerging techniques; however, this has been done only to a limited degree primarily due to the difficulty in creating controllable phantoms. The primary effects of tissue on the polarization of light are scattering, linear birefringence, and optical activity (circular birefringence). An ideal phantom would exhibit all these effects simultaneously in a controllable fashion. We have achieved this through the use of polyacrylamide gels with polystyrene microspheres added as scattering particles, strain applied to the gels to create birefringence, and sucrose added for optical activity. The phantom methodology has been validated using our polarimetry system. Currently, the phantom system is being used to extend our work in birefringence mapping of the myocardium and to further our work in characterizing tissue.