Carbogen breathing significantly enhances the penetration of red light in murine tumours in vivo.
We report results of experiments that evaluated the influence of oxygenation on the penetration of red light in tissue, with particular emphasis on 630 and 650 nm laser wavelengths commonly used in photodynamic therapy (PDT) of solid tumours. Direct measurements in tissue-simulating phantoms comprised of intact human erythrocytes suspended in a scattering emulsion demonstrated significant enhancements in fluence rate at depths of 0.5-2 cm from the irradiated surface when the cells were fully oxygenated versus fully deoxygenated. The 630 and 650 nm fluence rates at depth in the homogeneous phantoms continued to increase when examined over a continuous range of oxygen partial pressures from 0 to 160 Torr. When considered as a function of haemoglobin oxygen saturation, the largest increases in fluence rate were observed as the saturation increased beyond 70%. Dramatic increases in optical fluence rate were measured at the base of 1-cm-thick subcutaneous EMT6 mammary carcinomas in vivo when the tumour-bearing mouse was subjected to carbogen through a nose cone. These results indicate that improved tumour oxygenation is important in PDT not only for the maintenance of the oxygen-dependent photochemistry but, through the effects reported here, may also enable more efficient treatment of thicker lesions.
Mitra
Soumya
S
Department of Biochemistry and Biophysics, University of Rochester, 601 Elmwood Avenue, Box 648, Rochester, NY 14642, USA. soumya_mitra@urmc.rochester.edu
Foster
Thomas H
TH
D000818:Animals; D002245:Carbon Dioxide / Q000737:chemistry*; D004912:Erythrocytes / Q000378:metabolism; D006454:Hemoglobins / Q000378:metabolism; D006801:Humans; D001239:Inhalation; D007834:Lasers; D008027:Light; D051379:Mice; D010100:Oxygen / Q000737:chemistry* / Q000378:metabolism; D019047:Phantoms, Imaging; D010778:Photochemotherapy / Q000379:methods*; D011312:Pressure; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology; D012119:Respiration; D013053:Spectrophotometry; D013997:Time Factors
D006454:Hemoglobins; D011838:Radiation-Sensitizing Agents; D002245:Carbon Dioxide; C011700:carbogen; D010100:Oxygen