Abstract
The oxygenation status of tissue is important in several medical applications. It has long been appreciated that hypoxic tumors are resistant to radiation therapy, while in photodynamic therapy (PDT), the dependence on oxygen is even more pronounced. Our laboratory studies several problems in PDT that originate with this 3O 2-dependence. Use of 3O 2-sensitive electrodes with small (≤ 10 μm) tip diameters enables accurate measurement of metabolic and photochemical 3O 2 consumption in photosensitized tumor spheroids in vitro. The temporal response of these devices (<1 s) is sufficient to capture rapid depletion of 3O 2 during laser irradiation of individual spheroids. An important aspect of this research has been the development of appropriate mathematical models with which to interpret the microelectrode data and determine photophysical parameters. Recently, we have been establishing optical methods of measuring hemoglobin 3O 2-saturation in order to monitor oxygenation in rodent tumors during PDT. We have adopted a steady-state diffuse reflectance technique, in which white light is injected into the tumor via an optical fiber, and the spatially-resolved diffuse reflectance is monitored using appropriately spaced detection fibers. The signals are spectrally dispersed onto a CCD camera by a grating spectrograph, providing simultaneous acquisition of spatially-resolved diffuse reflectance data for a 160 nm range of wavelengths. Absorption spectra reconstructed using a diffusion theory approximation are then fit to linear combinations of oxy- and deoxyhemoglobin spectra to obtain the 3O 2-saturation.
| Original language | English |
|---|---|
| Title of host publication | Proceedings of SPIE - The International Society for Optical Engineering |
| Editors | Steven L. Jacques |
| Pages | 140-146 |
| Number of pages | 7 |
| Volume | 2681 |
| State | Published - 1996 |
| Externally published | Yes |
| Event | Laser-Tissue Interaction VII - San Jose, CA, USA Duration: Jan 29 1996 → Feb 1 1996 |
Other
| Other | Laser-Tissue Interaction VII |
|---|---|
| City | San Jose, CA, USA |
| Period | 1/29/96 → 2/1/96 |
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All Science Journal Classification (ASJC) codes
- Engineering(all)
Cite this
Microelectrode and optical measurements of oxygen in biological systems in vitro and in vivo. / Foster, Thomas H.; Nichols, Michael G.; Georgakoudi, Irene; Hull, Edward L.
Proceedings of SPIE - The International Society for Optical Engineering. ed. / Steven L. Jacques. Vol. 2681 1996. p. 140-146.Research output: Chapter in Book/Report/Conference proceeding › Conference contribution
}
TY - GEN
T1 - Microelectrode and optical measurements of oxygen in biological systems in vitro and in vivo
AU - Foster, Thomas H.
AU - Nichols, Michael G.
AU - Georgakoudi, Irene
AU - Hull, Edward L.
PY - 1996
Y1 - 1996
N2 - The oxygenation status of tissue is important in several medical applications. It has long been appreciated that hypoxic tumors are resistant to radiation therapy, while in photodynamic therapy (PDT), the dependence on oxygen is even more pronounced. Our laboratory studies several problems in PDT that originate with this 3O 2-dependence. Use of 3O 2-sensitive electrodes with small (≤ 10 μm) tip diameters enables accurate measurement of metabolic and photochemical 3O 2 consumption in photosensitized tumor spheroids in vitro. The temporal response of these devices (<1 s) is sufficient to capture rapid depletion of 3O 2 during laser irradiation of individual spheroids. An important aspect of this research has been the development of appropriate mathematical models with which to interpret the microelectrode data and determine photophysical parameters. Recently, we have been establishing optical methods of measuring hemoglobin 3O 2-saturation in order to monitor oxygenation in rodent tumors during PDT. We have adopted a steady-state diffuse reflectance technique, in which white light is injected into the tumor via an optical fiber, and the spatially-resolved diffuse reflectance is monitored using appropriately spaced detection fibers. The signals are spectrally dispersed onto a CCD camera by a grating spectrograph, providing simultaneous acquisition of spatially-resolved diffuse reflectance data for a 160 nm range of wavelengths. Absorption spectra reconstructed using a diffusion theory approximation are then fit to linear combinations of oxy- and deoxyhemoglobin spectra to obtain the 3O 2-saturation.
AB - The oxygenation status of tissue is important in several medical applications. It has long been appreciated that hypoxic tumors are resistant to radiation therapy, while in photodynamic therapy (PDT), the dependence on oxygen is even more pronounced. Our laboratory studies several problems in PDT that originate with this 3O 2-dependence. Use of 3O 2-sensitive electrodes with small (≤ 10 μm) tip diameters enables accurate measurement of metabolic and photochemical 3O 2 consumption in photosensitized tumor spheroids in vitro. The temporal response of these devices (<1 s) is sufficient to capture rapid depletion of 3O 2 during laser irradiation of individual spheroids. An important aspect of this research has been the development of appropriate mathematical models with which to interpret the microelectrode data and determine photophysical parameters. Recently, we have been establishing optical methods of measuring hemoglobin 3O 2-saturation in order to monitor oxygenation in rodent tumors during PDT. We have adopted a steady-state diffuse reflectance technique, in which white light is injected into the tumor via an optical fiber, and the spatially-resolved diffuse reflectance is monitored using appropriately spaced detection fibers. The signals are spectrally dispersed onto a CCD camera by a grating spectrograph, providing simultaneous acquisition of spatially-resolved diffuse reflectance data for a 160 nm range of wavelengths. Absorption spectra reconstructed using a diffusion theory approximation are then fit to linear combinations of oxy- and deoxyhemoglobin spectra to obtain the 3O 2-saturation.
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M3 - Conference contribution
SN - 0819420557
SN - 9780819420558
VL - 2681
SP - 140
EP - 146
BT - Proceedings of SPIE - The International Society for Optical Engineering
A2 - Jacques, Steven L.
ER -