Oxygen distribution and vascular injury in the mouse eye measured by phosphorescence-lifetime imaging

Abstract

Maps of the oxygen distribution in the retina of the mouse eye were obtained by phosphorescencelifetime imaging. Phosphor dissolved in the blood was excited by modulated light and phosphorescence imaged through microscope optics with an intensified-CCD camera. Phosphorescence lifetimes and oxygen pressures were calculated for each pixel of the images. The resolution was sufficient to permit the detection of anomalies that result in reduced oxygen pressures in individual retinal capillaries. High-resolution maps of oxygen distribution in the retina can provide greater understanding of the role of oxygen and vascular function in diseases of the eye.

Imaging of Hypoxia in Retinal Vascular Disease

“…Upon imaging and analysis using an oxygen map of the laser burn and surrounding area they observed a circular lesion with a central area of hypoxia (< 7 mmHg) that extended approximately 150-200 μm outward from the initial laser injury [100]. After imaging the lesion again 1 hour later there was no evidence of leakage of the phosphor into the tissue [100]. This study indicates that phosphorescence-lifetime imaging is a useful tool for identifying focal areas of regional hypoxia.…”

“…It was observed that phosphorescencelifetimes were directly dependent on oxygen concentration, with an increase in phosphorescence signal as PO 2 decreased, as described by a Stern-Volmer relationship [92,93]. This technique was modified for use in vivo to measure PO 2 in the retinal and choroidal vasculature of large animals such as cats and pigs [95][96][97], and later for smaller animals such as mice and rats [98][99][100][101][102][103][104]. More recently Shahidi et al have made significant advances by using phosphorescence-lifetime to image oxygen tension within the retinal tissue itself [105,106].…”

“…Other investigators have examined whether phosphorescence-lifetime imaging can be used to detect regions of local hypoxia created by laser photocoagulation. In these studies, a laser was used to create small (75 μm) focal lesions within the capillary network of the mouse retina [100]. Upon imaging and analysis using an oxygen map of the laser burn and surrounding area they observed a circular lesion with a central area of hypoxia (< 7 mmHg) that extended approximately 150-200 μm outward from the initial laser injury [100].…”

“…In these studies, a laser was used to create small (75 μm) focal lesions within the capillary network of the mouse retina [100]. Upon imaging and analysis using an oxygen map of the laser burn and surrounding area they observed a circular lesion with a central area of hypoxia (< 7 mmHg) that extended approximately 150-200 μm outward from the initial laser injury [100]. After imaging the lesion again 1 hour later there was no evidence of leakage of the phosphor into the tissue [100].…”

In vivophotoacoustic lifetime imaging of tumor hypoxia in small animals

“…While all these methods provide information about oxygen, each of them has significant limitations. Optical methods including near-infrared spectroscopy 12 and phosphorescence imaging 13 suffer from low penetration depth due to the strong optical scattering in tissue. Nuclear methods use various hypoxia-related probes for positron emission tomography 14 and single-photon emission computed tomography.…”