Comparative study of tumor hypoxia by diffuse optical spectroscopy and immunohistochemistry in two tumor models

In vivo monitoring of vascularization and oxygenation of tumor xenografts using optoacoustic microscopy and diffuse optical spectroscopy

The research is devoted to comparison of the blood vessel structure and the oxygen state of three xenografts: SN-12C, HCT-116 and Colo320. Differences in the vessel formation and the level of oxygenation are revealed by optoacoustic (OA) microscopy and diffuse optical spectroscopy (DOS) respectively. The Colo320 tumor is characterized by the highest values of vessel size and fraction. DOS showed increased content of deoxyhemoglobin that led to reduction of saturation level for Colo320 as compared to other tumors. Immunohistochemical (IHC) analysis for CD31 demonstrates the higher number of vessels in Colo320. The IHC for hypoxia was consistent with DOS results and revealed higher values of the relative hypoxic fraction in Colo320.

Diffuse Optical Spectroscopy Monitoring of Experimental Tumor Oxygenation after Red and Blue Light Photodynamic Therapy

Photodynamic therapy (PDT) is an effective technique for cancer treatment based on photoactivation of photosensitizer accumulated in pathological tissues resulting in singlet oxygen production. Employment of red (660 nm) or blue (405 nm) light differing in typical penetration depth within the tissue for PDT performance provides wide opportunities for improving PDT protocols. Oxygenation dynamics in the treated area can be monitored using diffuse optical spectroscopy (DOS) which allows evaluating tumor response to treatment. In this study, we report on monitoring oxygenation dynamics in experimental tumors after PDT treatment with chlorin-based photosensitizers using red or blue light. The untreated and red light PDT groups demonstrate a gradual decrease in tumor oxygen saturation during the 7-day observation period, however, the reason is different: in the untreated group, the effect is explained by the excessive tumor growth, while in the PDT group, the effect is caused by the blood flow arrest preventing delivery of oxygenated blood to the tumor. The blue light PDT procedure, on the contrary, demonstrates the preservation of the blood oxygen saturation in the tumor during the entire observation period due to superficial action of the blue-light PDT and weaker tumor growth inhibition. Irradiation-only regimes show a primarily insignificant decrease in tumor oxygen saturation owing to partial inhibition of tumor growth. The DOS observations are interpreted based on histology analysis.

Spatially resolved diffuse imaging for high-speed depth estimation of jet injection

We investigate the use of spatially resolved diffuse imaging to track a fluid jet delivered at high speed into skin tissue. A jet injector with a short needle to deliver drugs beneath the dermis, is modified to incorporate a laser beam into the jet, which is ejected into ex vivo porcine tissue. The diffuse light emitted from the side and top of the tissue sample is recorded using high-speed videography. Similar experiments, using a depth-controlled fiber optic source, generate a reference dataset. The side light distribution is related to source depth for the controlled-source experiments and used to track the effective source depth of the injections. Postinjection X-ray images show agreement between the jet penetration and ultimate light source depth. The surface light intensity profile is parameterized with a single parameter and an exponential function is used to relate this parameter to source depth for the controlled-source data. This empirical model is then used to estimate the effective source depth from the surface profile of the injection experiments. The depth estimates for injections into fat remain close to the side depth estimates, with a root-mean-square error of 1.1 mm, up to a source depth of 8 mm.

Diffuse optical spectroscopy assessment of rodent tumor model oxygen state after single-dose irradiation

Modern radiation therapy of malignant tumors requires careful selection of conditions that can improve the effectiveness of the treatment. The study of the dynamics and mechanisms of tumor reoxygenation after radiation therapy makes it possible to select the regimens for optimizing the ongoing treatment. Diffuse optical spectroscopy (DOS) is among the methods used for non-invasive assessment of tissue oxygenation. In this work DOS was used forin vivoregistration of changes in oxygenation level of an experimental rat tumor after single-dose irradiation at a dose of 10 Gy and investigation of their possible mechanisms. It was demonstrated that in 24 h after treatment, tumor oxygenation increases, which is mainly due to an increase in the oxygen supply to the tissues. DOS is demonstrated to be efficient for study of changes in blood flow parameters when monitoring tumor response to therapy.