In summary, NIRS has spatial resolution of slightly less than 1 cm, temporal resolution of milliseconds to tens of milliseconds, light penetration of only about 1 cm into the superficial portions of the brain, and the ability to estimate amounts of oxyhemoglobin, deoxyhemoglobin
, and total hemoglobin.
When the crosslinked deoxyhemoglobin
was compared with deoxyhemoglobin
refined using a similar protocol (7), no significant perturbations in the tertiary or quaternary structure were found to be introduced by the presence of the sebacyl residue.
This higher field strength makes possible images of sufficiently high resolution to localize brain activity to the scale of fractions of an inch, and also maximizes the contrast between hemoglobin and deoxyhemoglobin
Fortunately, techniques such as those disclosed above can overcome this limitation because oxy- and deoxyhemoglobin
have numerous isosbestic points in the visible spectral range, allowing blood vessels to be imaged with visible light.
When T2 is significantly lowered (as in hematomas containing deoxyhemoglobin
, intracellular methemoglobin, or hemosiderin), diffusion weighting cannot be successfully achieved and DWI becomes unreliable.
Polymer structure and polymerization of deoxyhemoglobin
In the dermis, absorptive properties are largely dependent on oxy- and deoxyhemoglobin
located in the dermal blood vessels /plexuses, whereas collagen fibers account for almost all of the light-scattering properties of the dermis.
Absorption spectra of human fetal and adult oxyhemoglobin, deoxyhemoglobin
, carboxyhemoglobin and methemoglobin.
It is also known that erythrocyte folate is electrostatically associated with deoxyhemoglobin
, within the hollow central cavity of the quaternary structure of the hemoglobin (Hb) molecule (21-24).
It is likely that in pulse oximetry the signal backgrounds track well enough compared with oxy- and deoxyhemoglobin
absorbance changes over the clinical range that the results are acceptably accurate.
Absorption spectra of human, fetal and adult oxyhemoglobin, deoxyhemoglobin
, carboxyhemoglobin, and methemoglobin.
The Chiron 800 CO-oximeter is an overdetermined system that uses 10 wavelengths to directly measure total hemoglobin, oxyhemoglobin, carboxyhemoglobin, deoxyhemoglobin
, and MetHb.
2] affinity by cross-linking the [beta] chains of the tetramer and stabilizing the salt bridges present in deoxyhemoglobin
that must be broken for [O.
(HHb), methemoglobin (MetHb), and carboxyhemoglobin (COHb).
Summing the concentrations for five derivatives--oxyhemoglobin, deoxyhemoglobin
, SulfHb, carboxyhemoglobin (COHb), and MetHb--yields the concentration of total Hb, and the percentage of each individual derivative present was obtained by dividing each concentration by the total Hb concentration.