Methemoglobin (MetHb) is an important biomolecule, which is involved in a number of pathways associated with reactive oxygen species (ROS). Thus, MetHb has a potential to be used as a surrogate measure of ROS activity. Unfortunately, most of the existing clinical modalities used for MetHb concentration measurements determine the systemic MetHb level. Local MetHb variations, which can be a significant predictor of tissue health for some etiologies (e.g., burns), cannot be measured in a simple and systematic way. The present study is an attempt to develop a MetHb visualization approach using multispectral imaging.
Methods: The phantoms mimicking the optical property of human skin were prepared and imaged using a multispectral imaging device: (1) 4% intralipid (IL) (20%, Sigma-Aldrich, Canada) was used to mimic the scattering property of skin; (2) 10% (15 g/L) of red blood cells (netCAD;Vancouver, Canada) was used to mimic the optical absorption of skin; and MetHb [obtained by dissolved human hemoglobin lyophilized powder (H7379, Sigma-Aldrich, Canada) in phosphate buffer saline (PBS)]: 0%, 1%, 3%, 10% and 20% of MetHb/oxyhemoglobin were used to provide optical contrast. The phantoms were cured in 10-mm standard cuvettes. Thus, all concentrations were scaled by the factor of 0.15 to get the optical properties similar to the skin with the thickness of 1.5 mm. For visualization, we placed five phantoms side-to-side and imaged them with a multispectral imaging device (600-1000 nm spectral range) with a field of view 7 × 7 cm.
Results: The extracted MetHb concentrations are in qualitative agreement with the design, which was validated using light transmission spectroscopy.
Discussion: The preliminary results show the utility of multispectral imaging for visualization/quantification of local MetHb concentrations in surface tissues.