What it does…

Tissue scatters light. When a surgeon views tissue under a regular microscope, he/she is unable to clearly see the margins of the cancer due to this scattering. The degree of scatter and depolarization further depends upon the depth of tissue travelled and the wavelength (color) of the light.

LumaMed’s PsiScan uses Polarization subtraction Imaging (PSI) to overcome this problem. Polarization subtraction imaging can examine tissue at selected depths (about 200 to 500 microns) by imaging only light that remains polarized and rejecting all depolarized light. In other words it microscopically images only the superficial layer of the tissue resulting in a high resolution, high contrast image that is not obscured by light from deeper layers. This is important for two reasons.

• Cancers originate in the epidermal or superficial layers of organs. Therefore early cancer is found in this layer.
• Successful surgical excision of cancer requires that the margins be normal or negative. This can be readily determined by examining the superficial layer of removed tissue.

PSI produces images with a resolution similar to those produced by conventional pathology but with a higher degree of contrast between normal and cancer tissue. In conventional pathology, a technician uses a special knife called a microtome to cut thin layers of frozen or fixed tissue for examination. This takes time and several processing steps. PSI by contrast, uses polarized light to obtain the thin layer allowing the examination to be done on the patient in real time rather than taking the tissue to the laboratory.

How it works…

To see a video explaining how PSI works in a research device named the PolCam that appeared on KOIN Local 6 TV in Portland. Play a movie below.