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Effect of Photothermal Therapy on Breast Tumor Vascular Contents: Noninvasive Monitoring by Near-infrared Spectroscopy


  • Posted on the website on 4 April 2005

*To whom correspondence should be addressed: Biomedical Engineering Graduate Program, P.O. Box 19138, University of Texas at Arlington, Arlington, TX 76019, USA. Fax: 817-272-2251; e-mail:


The goal of this study was to investigate the effect of photothermal laser irradiation on rat breast tumor (DMBA-4) vascular contents. An 805-nm diode laser was used in our experiment with a power density ranging from 0.32 to 1.27 W/cm2. The dynamic changes of oxygenated hemoglobin and total hemoglobin concentrations, Δ[HbO2] and Δ[Hb]total, in rat tumors during photothermal irradiation were noninvasively monitored by a near-infrared spectroscopy system. A multichannel thermal detection system was also used simultaneously to record temperatures at different locations within the tumors. Our experimental results showed that: (1) photoirradiation did have the ability to induce hyperthermic effects inside the rat breast tumors in a single exponential trend; (2) the significant changes (P < 0.005) of Δ[HbO2] and Δ[Hb]total in response to a low dosage of laser irradiation (0.32 W/cm2) have a single exponential increasing trend, similar to that seen in the tumor interior temperature; and (3) the increase in magnitude of Δ[Hb]total is nearly two times greater than that of Δ[Hb]total, suggesting that photoirradiation may enhance tumor vascular oxygenation. The last observation may be important to reveal the hidden mechanism of photoirradiation on tumors, leading to improvement of tumor treatment efficiency.