Dynamically observing intratumor, injection of laser-absorbing dye and immunoadjuvant using digital x-ray imaging technique

Selective laser-tissue interaction is a promising method for noninvasive tr eatment of deep tumors. Using a laser beam with a wavelength in the near-in frared region and an intratumoral injection of a laser-absorbing dye, the l aser energy can destroy targeted tumor cells while sparing normal surroundi ng tissue. Introducing an immunoadjuvant can achieve possible systemic anti tumor immune response, hence augmenting the selective laser-tissue interact ion. Administration of the dye and the immunoadjuvant, and the time window for optimal laser application, are crucial in determining the outcome of th e treatment. To determine the dynamic distribution of intratumor-injected l aser-absorbing dye and immunoadjuvant, a digital x-ray imaging technique wa s employed. Indocyanine green as the laser-absorbing dye and glycated chito san as the immunoadjuvant were injected into the center of a rat tumor and the, transmitted x-ray signals through tumor tissue and surrounding normal tissue, before and after the injection, were acquired and analyzed. The tra nsmitted signals through tissue were reduced due to the injection of either dye or immunoadjuvant solution. The diffusion of aqueous solutions in tiss ue was a function of time and of the properties of the solutes. The indocya nine green solution, due to its low molecular weight, diffused through the tumor almost immediately after injection, then gradually dispersed into the surrounding tissue. The glycated chitosan, on the other hand, due to its h igh molecular weight and high viscosity, dispersed slowly and took about 20 to 25 min to reach maximum accumulation at the edge of the tumor. Our resu lts showed that the digital x-ray images could be used to guide the precise positioning of the injecting needle, and to determine the distributions of the dye and immunoadjuvant in the tumor and in the surrounding normal tiss ue. Apparently, the dynamic observation of dye and immunoadjuvant administr ation and their diffusion process could be used to optimize the parameters for laser treatment of deep tumors. (C) 2001 Society of Photo-Optical Instr umentation Engineers.