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BioPhotonics Preview - November/December 2021

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Here is your first look at the editorial content for the upcoming November/December issue of BioPhotonics.



Two-Photon Imaging and Neuropsychiatric Disease

Since its introduction to neuroscience, two-photon imaging has been used to image synaptic connections in living animals. The formation of synapses, their solidification, and disappearance forms one fundamental aspect of how intact brain circuits learn, memorize, and forget. Synaptic-scale two-photon imaging has also brought to light key mechanisms underlying neuropsychiatric diseases such as epilepsy, multiple sclerosis, or schizophrenia. Recent synaptic imaging in mice during prolonged anesthesia highlights once again, how two-photon microscopy may help to connect the dots and drive paradigm shifts in patient care, in this case, intensive care medicine. It’s long known that prolonged anesthesia often leads to cognitive deficits in ICU survivors of all ages, but it was only now shown that widespread synaptic changes may play a key role in it. More research in this direction will drive standardized, individually tailored anesthetic regimens in intensive care, and push adjuvant therapies to maintain brain structure and function during prolonged anesthesia.

NIR Spectroscopy and Stroke Detection

In most cases, near-infrared wavelengths are used due to their ability to partially transmit through biological tissues. Experiments utilizing conventional absorption have been developed to monitor relative concentrations of Hemoglobin, which can be correlated to brain activity. Time-resolved modalities have been developed to monitor flow dynamics and to determine absolute oxygen concentrations. These measurements can be used to track recovery times following a stroke. To elucidate structural information, ultrafast lasers are being used to collect images deep into brain tissue. Because of their short pulse duration, dynamical information can be simultaneously collected including blood flow and recovery in real-time. In this manuscript, a presentation of several experiments is discussed with particular focus on the different laser technologies used to facilitate these results.

Fluorescence Lifetime Imaging and Glioblastoma Detection

Glioblastoma multiforme (GBM) is the most aggressive form of brain cancer. Despite its very poor prognosis, accurate tumor resection has been directly linked to elongated survival rates. During craniotomy procedures to perform tumor resection, neurosurgeons need to find a fine balance between aggressive resection of the tumor and the surrounding tissue while preserving the neurological activities of the brain. GBM tumors do not have a well-defined border. Instead, they are characterized by a highly infiltrative edge into the surrounding tissue, or peritumoral region. This peritumoral region harbors tumor cells and other cancer-associated molecular markers infiltrated within viable brain tissue. There is a need to identify and characterize the infiltrative edges of GBM tumors in vivo to avoid recurrence and improve the patient’s prognosis. Fluorescence lifetime imaging (FLIm) is an optical technique well-suited to interrogate tissues in vivo. By measuring the time-resolved fluorescence properties of tissue without the need of additional contrast agents, FLIm can distinguish different tissue types including cortex, white matter, tumor masses, and the infiltrative edges in GBM patients. Ongoing clinical studies will demonstrate the efficacy of optical techniques such as FLIm as an intraoperative tool for neurosurgeons to improve tumor resection strategies and ultimately impact the survival rate of GBM patients.

Lasers and Epilepsy Treatment

In a survey conducted by SUNY Downstate Medical Center some years ago, more than half of epilepsy patients said they would not consider brain surgery even if it cured them; and today neurosurgeons say much hesitancy remains. But while the most common treatments for epilepsy remain potent medication and invasive resection surgery (following craniotomy), lasers are shining the light on a potentially safer and lasting alternative. MRI-guided laser interstitial thermal therapy, where a laser-based system such as VISUALASE (distributed by Medtronic) heats and ablates the cells propagating seizures, has been shown in a multi-institutional study to dramatically improve patients outcomes on the Engel scale, even for those for whom drug therapy is not effective. And researchers at Cornell University used a Ti:sapphire laser to generate pulses that blocked seizure propagation in the neocortex in rats – all while not severing other key brain messaging, such as that involving tail movement. As probes guided by imaging technology have improved the precision of laser treatment, the day may arrive where laser treatment of epilepsy can swiftly profoundly improve quality of life, much as deep brain stimulation has done for those with various motor-related disabilities.


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