Localization of cortical tissue optical changes during seizure activity in vivo with optical coherence tomography.

Optical coherence tomography (OCT) is a high resolution, minimally invasive imaging technique, which can produce depth-resolved cross-sectional images. In this study, OCT was used to detect changes in the optical properties of cortical tissue in vivo in mice during the induction of global (pentylenetetrazol) and focal (4-aminopyridine) seizures. Through the use of a confidence interval statistical method on depth-resolved volumes of attenuation coefficient, we demonstrated localization of regions exhibiting both significant positive and negative changes in attenuation coefficient, as well as differentiating between global and focal seizure propagation.

Decreased light attenuation in cerebral cortex during cerebral edema detected using optical coherence tomography.

Cerebral edema develops in response to a variety of conditions, including traumatic brain injury and stroke, and contributes to the poor prognosis associated with these injuries. This study examines the use of optical coherence tomography (OCT) for detecting cerebral edema in vivo. Three-dimensional imaging of an in vivo water intoxication model in mice was performed using a spectral-domain OCT system centered at 1300 nm. The change in attenuation coefficient was calculated and cerebral blood flow was analyzed using Doppler OCT techniques. We found that the average attenuation coefficient in the cerebral cortex decreased over time as edema progressed. The initial decrease began within minutes of inducing cerebral edema and a maximum decrease of 8% was observed by the end of the experiment. Additionally, cerebral blood flow slowed during late-stage edema. Analysis of local regions revealed the same trend at various locations in the brain, consistent with the global nature of the cerebral edema model used in this study. These results demonstrate that OCT is capable of detecting in vivo optical changes occurring due to cerebral edema and highlights the potential of OCT for precise spatiotemporal detection of cerebral edema.

Thinned-skull cortical window technique for in vivo optical coherence tomography imaging.

Optical coherence tomography (OCT) is a biomedical imaging technique with high spatial-temporal resolution. With its minimally invasive approach OCT has been used extensively in ophthalmology, dermatology, and gastroenterology. Using a thinned-skull cortical window (TSCW), we employ spectral-domain OCT (SD-OCT) modality as a tool to image the cortex in vivo. Commonly, an opened-skull has been used for neuro-imaging as it provides more versatility, however, a TSCW approach is less invasive and is an effective mean for long term imaging in neuropathology studies. Here, we present a method of creating a TSCW in a mouse model for in vivo OCT imaging of the cerebral cortex.

In vivo detection of cortical optical changes associated with seizure activity with optical coherence tomography.

The most common technology for seizure detection is with electroencephalography (EEG), which has low spatial resolution and minimal depth discrimination. Optical techniques using near-infrared (NIR) light have been used to improve upon EEG technology and previous research has suggested that optical changes, specifically changes in near-infrared optical scattering, may precede EEG seizure onset in in vivo models. Optical coherence tomography (OCT) is a high resolution, minimally invasive imaging technique, which can produce depth resolved cross-sectional images. In this study, OCT was used to detect changes in optical properties of cortical tissue in vivo in mice before and during the induction of generalized seizure activity. We demonstrated that a significant decrease (P < 0.001) in backscattered intensity during seizure progression can be detected before the onset of observable manifestations of generalized (stage-5) seizures. These results indicate the feasibility of minimally-invasive optical detection of seizures with OCT.