Orthogonal polarization spectral imaging

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Orthogonal polarization spectral imaging is a method for imaging small blood vessels[1] in tissue like the nail bed or lip.

It uses a light source of linearly polarized light with a wavelength of 550 nanometers, an isosbestic point for hemoglobin, thus imaging the erythrocytes as they are flowing through the small blood vessels. The reflected light orthogonal (at a 90° angle) to the emitted light is recorded, thus eliminating direct reflections. The depolarized light forms an image of the microcirculation on a CCD, which can be captured through single frames or on videotape. The image produced is as if the light source is actually placed behind the desired target or transilluminated.[2]

It has been validated, even under low hematocrit circumstances.[3]


  1. ^ Cerný V, Turek Z, Parízková R (2007). "Orthogonal polarization spectral imaging" (PDF). Physiol Res. 56 (2): 141–7. PMID 16555953. 
  2. ^ "OPS Imaging". Cytometrics. Retrieved 2009-08-17. 
  3. ^ Harris, AG; Sinitsina I; Messmer K. (2002-04). "Validation of OPS imaging for microvascular measurements during isovolumic hemodilution and low hematocrits". Am J Physiol Heart Circ Physiol. 282 (4): 1502–9. PMID 11893588. doi:10.1152/ajpheart.00475.2001.  Check date values in: |date= (help)