All Research Areas

Oxygen Tension Imaging

The multimodal optical imaging system is a single instrument capable of simultaneously imaging numerous hemodynamic parameters such as cerebral blood flow and plasma oxygen tension (pO2). Laser speckle contrast imaging (LSCI) provides wide-field information regarding relative changes in blood flow while phosphorescence lifetime imaging provides mappings of absolute pO2 values. We use a biocompatible porphyrin probe whose phosphorescence is quenched by dissolved environmental oxygen. The measured lifetime is used to calculate the pO2 using the Stern-Volmer relationship.

\begin{equation}
\frac{I_0}{I} = 1 + k_q\tau_0[Q]
\end{equation}

A digital micromirror device (DMD) is used to provide structured illumination for the excitation of the oxygen-sensitive probe. This allows for rapid data acquisition and enhanced signal-to-noise compared to traditional laser scanning or gated camera techniques. The DMD is also used to induce precisely targeted ischemic lesions within individual vessels using photothrombosis. Conventional photothrombotic techniques suffer from a lack of specificity and produce non-pathophysiologically-relevant ischemic lesions.

Relevant Publications

Imaging of cortical oxygen tension and blood flow following targeted photothrombotic stroke

C. T. Sullender, A. E. Mark, T. A. Clark, T. V. Esipova, S. A. Vinogradov, T. A. Jones, and A. K. Dunn, Neurophotonics (2018)

Simultaneous imaging of oxygen tension and blood flow in animals using a digital micromirror device

A. Ponticorvo and A. K. Dunn, Optics Express (2010)

Simultaneous multispectral reflectance imaging and laser speckle flowmetry of cerebral blood flow and oxygen metabolism in focal cerebral ischemia

P. B. Jones, H. K. Shin, D. A. Boas, B. T. Hyman, M. A. Moskowitz, C. Ayata, and A. K. Dunn, Journal of Biomedical Optics (2008)

Simultaneous imaging of total cerebral hemoglobin concentration, oxygenation, and blood flow during functional activation

A. K. Dunn, A. Devor, H. Bolay, M. L. Andermann, M. A. Moskowitz, A. M. Dale, and D. A. Boas, Optics Letters (2003)
Oxygen Tension Measurements

Oxygen-dependent phosphorescence lifetime measurements are used to obtain absolute oxygen tension (pO2) within the cerebral vasculature. The pO2 within the descending arteriole is higher than the neighboring parenchyma or veins.

Multimodal Imaging System Schematic

Imaging system combining laser speckle contrast imaging and phosphorescence lifetime mapping for studying cerebral blood flow and vascular oxygenation.

Periinfarct Depolarization

Targeted photothrombosis is used to induce ischemic lesions that can cause spreading depolarizations easily imaged with LSCI.