Ratiometric spectral imaging for fast tumor detection and chemotherapy monitoring in vivo

We report a novel in vivo spectral imaging approach to cancer detection and chemotherapy assessment. We describe and characterize a ratiometric spectral imaging and analysis method and evaluate its performance for tumor detection and delineation by quantitatively monitoring the specific accumulation of targeted gallium corrole (HerGa) into HER2-positive (HER2 +) breast tumors. HerGa temporal accumulation in nude mice bearing HER2 + breast tumors was monitored comparatively by a. this new ratiometric imaging and analysis method; b. established (reflectance and fluorescence) spectral imaging; c. more commonly used fluorescence intensity imaging. We also tested the feasibility of HerGa imaging in vivo using the ratiometric spectral imaging method for tumor detection and delineation. Our results show that the new method not only provides better quantitative information than typical spectral imaging, but also better specificity than standard fluorescence intensity imaging, thus allowing enhanced in vivo outlining of tumors and dynamic, quantitative monitoring of targeted chemotherapy agent accumulation into them

Depth dependence of vascular fluorescence imaging

In vivo surface imaging of fluorescently labeled vasculature has become a widely used tool for functional brain imaging studies. Techniques such as phosphorescence quenching for oxygen tension measurements and indocyanine green fluorescence for vessel perfusion monitoring rely on surface measurements of vascular fluorescence. However, the depth dependence of the measured fluorescence signals has not been modeled in great detail. In this paper, we investigate the depth dependence of the measured signals using a three-dimensional Monte Carlo model combined with high resolution vascular anatomy. We found that a bulk-vascularization assumption to modeling the depth dependence of the signal does not provide an accurate picture of penetration depth of the collected fluorescence signal in most cases. Instead the physical distribution of microvasculature, the degree of absorption difference between extravascular and intravascular space, and the overall difference in absorption at the excitation and emission wavelengths must be taken into account to determine the depth penetration of the fluorescence signal. Additionally, we found that using targeted illumination can provide for superior surface vessel sensitivity over wide-field illumination, with small area detection offering an even greater amount of sensitivity to surface vasculature. Depth sensitivity can be enhanced by either increasing the detector area or increasing the illumination area. Finally, we see that excitation wavelength and vessel size can affect intra-vessel sampling distribution, as well as the amount of signal that originates from inside the vessel under targeted illumination conditions

Haemodynamics and Oxygenation of the Tumor Microcirculation

Abnormalities of the tumor vasculature and their consequences on the microenvironment of tumor cells impact on tumor progression and response to both blood-borne anti-cancer agents and radio-therapy, as well as making tumor blood vessels a target for therapy in their own right. Intravital microscopy of experimental tumors, most commonly grown in ‘window’ chambers, such as the dorsal skin fold chamber in mice and rats, enables investigations of tumor microcirculatory function. This is needed both to understand the molecular control of tumor vascular function and to measure the response of the vasculature to treatment. In particular, intravital microscopy enables parameters associated with blood supply, vascular permeability and oxygenation to be estimated, at high spatial and temporal resolution. In this chapter, methods used for measuring a range of these parameters, specific examples of their applications, the significance of findings and some of the limitations of the techniques are described

Longitudinal Imaging of the Ageing Mouse

Several non-invasive imaging techniques are used to investigate the effect of pathologies and treatments over time in mouse models. Each preclinical in vivo technique provides longitudinal and quantitative measurements of changes in tissues and organs, which are fundamental for the evaluation of alterations in phenotype due to pathologies, interventions and treatments. However, it is still unclear how these imaging modalities can be used to study ageing with mice models. Almost all age related pathologies in mice such as osteoporosis, arthritis, diabetes, cancer, thrombi, dementia, to name a few, can be imaged in vivo by at least one longitudinal imaging modality. These measurements are the basis for quantification of treatment effects in the development phase of a novel treatment prior to its clinical testing. Furthermore, the non-invasive nature of such investigations allows the assessment of different tissue and organ phenotypes in the same animal and over time, providing the opportunity to study the dysfunction of multiple tissues associated with the ageing process. This review paper aims to provide an overview of the applications of the most commonly used in vivo imaging modalities used in mouse studies: micro-computed-tomography, preclinical magnetic-resonance-imaging, preclinical positron-emission-tomography, preclinical single photon emission computed tomography, ultrasound, intravital microscopy, and whole body optical imaging

Oxygen tension measurements in the cat eye: Influence of the vasculature

Previous studies investigating the regulation of oxygen in the retina and optic nerve head (ONH) have focused on the changes in local tissue oxygen tension (pO\sb2) induced by changes in arterial blood gases or acute increases in intraocular pressure (IOP). However, most of these studies have not considered how the larger retinal vessels directly affect the local oxygen environment and the overall pattern of oxygen delivery from vessel to tissue. This work is the first to combine retinal intra-vascular and peri-vascular pO\sb2 measurements to study the delivery of oxygen to the retina. An optical imaging technique, based on the oxygen dependent quenching of phosphorescence, was used to measure pO\sb2 inside the lumen of retinal and ONH vessels during hyperoxia and acute increases in the IOP. In parallel studies, oxygen-sensitive microelectrodes were used to measure vitreal pO\sb2 near retinal vessels and the ONH during hyperoxia and diffuse flicker. Laser Doppler flowmetry was used simultaneously in some of the microelectrode studies to measure both the pO\sb2 and ONH blood flow changes during diffuse flicker. Retinal venules were found to have a high luminal pO\sb2 in normoxia (32-54 mmHg) and, in some cases, an outward oxygen flux. During hyperoxia, the outward oxygen flux increased and luminal pO\sb2 values were significantly higher. Because venular pO\sb2 was sometimes higher than surrounding tissue pO\sb2, it is proposed that oxygen from the choroid and/or neighboring arterioles could be responsible. The ONH center was found to be well regulated to hyperoxia and to artificial increases in IOP. The pO\sb2 in the ONH rim was not as well regulated during hyperoxia, suggesting that an outward diffusion of oxygen from retinal arterioles near the rim may be a factor. Diffuse flicker stimulation of the retina produced a decrease in periarteriolar pO\sb2 and an increase in ONH blood flow. This suggests that increased neuronal activity associated with flicker increases inner retinal and ONH metabolism and blood flow. Finally, peri-arteriolar pO\sb2 increased during dark adaptation, suggesting an increased retinal vascular oxygen delivery in dark

Effects of Thermal Stress on Ascidian Larval Development

Rising ocean temperatures caused by climate change have the potential to cause detrimental effects to the development of many marine organisms. Numerous species of ascidians have been shown to undergo faster rates of larval development when subject to heat stress. In this study, we investigated the effects of increased temperature on the development and survival of embryos in the species Boltenia villosa. B. villosa embryos were placed under three different temperature conditions, ambient (11-12°C), mid (14-15.5°C) or high (16.5-18°C), and rates of development to important stage markers were observed. Survival rate to larval stage was also recorded. Our results show that embryos subjected to higher temperatures develop faster than those at ambient temperatures but have lower survival rates. This suggests that while higher temperatures speed up development, they also have detrimental effects on the quality of development