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1 June 2001 Monitoring Tumor Response During Photodynamic Therapy Using Near-infrared Photon-migration Spectroscopy
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Benzoporphyrin-derivative (BPD)–monoacid-ring A photodynamic therapy (PDT) was performed on subcutaneous tumor implants in a rat ovarian cancer model. In order to assess PDT efficacy the tumor and normal tissue optical properties were measured noninvasively prior to and during PDT using frequency-domain photon migration (FDPM). FDPM data were used to quantify tissue absorption and reduced scattering properties (given by the parameters μa and μ′s, respectively) at four near-infrared (NIR) wavelengths (674, 811, 849 and 956 nm). Tissue physiologic properties, including the in vivo concentration of BPD, deoxy-hemoglobin (Hb), oxy-hemoglobin (HbO2), total hemoglobin (TotHb), water (H2O) and percent tissue hemoglobin oxygen saturation (%StO2), were calculated from optical property data. PDT efficacy was also determined from morphometric analysis of tumor necrosis in histologic specimens. All the measured tumor properties changed significantly during PDT. [Hb] increased by 9%, while [HbO2], [TotHb] and %StO2 decreased by 18, 7 and 12%, respectively. Using histologic data we show that long-term PDT efficacy is highly correlated to mean BPD concentration in tumor and PDT-induced acute changes in [HbO2], [TotHb] and %StO2 (correlation coefficients of 0.829, 0.817 and 0.953, respectively). Overall, our results indicate that NIR FDPM spectroscopy is able to quantify noninvasively and dynamically the PDT-induced physiological effects in vivo that are highly correlated with therapeutic efficacy.

Tuan H. Pham, René Hornung, Michael W. Berns, Yona Tadir, and Bruce J. Tromberg "Monitoring Tumor Response During Photodynamic Therapy Using Near-infrared Photon-migration Spectroscopy," Photochemistry and Photobiology 73(6), 669-677, (1 June 2001).<0669:MTRDPT>2.0.CO;2
Received: 3 August 2000; Accepted: 1 February 2001; Published: 1 June 2001

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