Tissue Hemoglobin Index (Thi); References - Hutchinson Technology InSpectra StO2 650 Manual Del Usuario

Technology of the InSpectra
(continued)
Although a first derivative technique can remove baseline shifts from optical density spectra, it cannot remove
sloping or tilting due to changes in wavelength dependent scattering, either over time or upon movement
of the measurement sensor to different tissue sites. Matcher and Cooper (1984) showed that the second
derivative preprocessing of tissue attenuation measurements corrects for shifting and sloping baselines, as a
result of measuring the attenuation of light in a tissue scattering environment. Research by Myers et al (2005)
demonstrated that scaling the second derivative absorbance spectrum provides a measurement that is further
insensitive to total hemoglobin and optical path length changes and yields a calibration curve to tissue hemoglobin
oxygen saturation.

Tissue Hemoglobin Index (THI)

Tissue Hemoglobin Index (THI), as measured in a range of 1–99 by the InSpectra
Monitor, is a quantified value that corresponds to the amount of hemoglobin present within the volume of tissue
illuminated by the patient contact sensor optical signal. Because the volume of tissue illuminated is comprised of
extra vascular and vascular tissue, THI measurements do not reflect blood hemoglobin content alone. The amount
of tissue hemoglobin present is influenced by blood hemoglobin concentration and microvasculature volume.
Using InSpectra Sensor, a THI reading of 10 indicates twice the signal strength as a reading of 5.0.
™ StO
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Along with regional tissue oxygen saturation (StO
hemoglobin present in the illuminated volume, and can therefore serve as a hemoglobin signal strength
indicator at the measurement site. A THI greater than 5.0 indicates sufficient hemoglobin to obtain an adequate
signal in most circumstances.

References

1. Cui W, Kumar C, Chance B. (1991). Experimental study of migration depth for the photons measured at sample
surface. Proc SPIE, 1431, 180–191.
2. Mancini D, Bolinger L, Li H, Kendrick K, Chance B, Wilson JR. (1994). Validation of near-infrared spectroscopy
in humans. J Appl Physiol, 77, 2740–2747.
3. Matcher SJ, Cooper CE. (1984). Absolute quantification of deoxyhaemoglobin concentration in tissue near
infrared spectroscopy. Phys Med Biol, 39, 1295–1312.
4. Merrick, MF, Pardue, HL. (1986). Evaluation of absorption and first-and second-derivative spectra for
simultaneous quantification of bilirubin and hemoglobin. Clin Chem, 32(4), 598–602.
5. Myers D, Anderson L, Seifert R, Ortner J, Cooper CE, Beilman G, Mowlem, JD. (2005). Noninvasive method
for measuring local hemoglobin oxygen saturation in tissue using wide gap second derivative near infrared
spectroscopy. J BioMed Opt, 10(3), 034017/1–18.
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Technology
StO Tissue Oxygenation Monitor
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), THI provides a method for determining the amount of
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StO Tissue Oxygenation
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