Researchers have developed a combination of commercially available hardware and open-source software, named PySight, which improves rapid 2D and 3D imaging of the brain and other tissues. By seamlessly enabling integration of the fastest 3D imaging solution available today, the advance in microscopy could help scientists to better understand brain dynamics and discover new treatments for health problems such as stroke, epilepsy, and dementia.
In Optica, The Optical Society’s journal for high impact research, the researchers describe PySight, which serves as an add-on for laser scanning microscopes. Geared with this novel combination of software and hardware, they improved the quality of 2D and 3D imaging of neuronal activity in the living brain.
Because it can image deep into tissue, a laser-based imaging technique known as multiphoton microscopy is often used to study the rapid activity patterns of neurons, blood vessels, and other cells at high resolution over time. This microscopy method uses laser pulses to excite fluorescent probes, eliciting the emission of photons, some of which are detected and used to form 2D and 3D images.
Trying to capture the full breadth of neuronal activity with multiphoton microscopy forces scientists to image faster. As a result, fewer and fewer photons become available to form images, much like taking a photo with shorter and shorter exposure times. The challenge then becomes how to get meaningful images under these dim conditions.
In addition to advancing neural imaging research, PySight’s improved sensitivity could facilitate rapid intraoperative identification of malignant cells in human patients using multiphoton microscopy. PySight’s novel approach for reconstructing 3D scenes could also improve performance of light detection and ranging, or LIDAR. This could help lower the costs of self-driving cars that use LIDAR to map their surroundings.
PySight provides high spatiotemporal resolution while producing a data stream that scales with the number of detected photons, not the volume or area being imaged.
To reconstruct a multidimensional image, knowing when each photon hits the detector isn’t enough. It’s necessary to also know where it originated in the brain.
The photon arrival times are generated by a device known as a multiple-event time digitizer, or multiscaler, which records the times with a precision of 100 picoseconds. Another key component was an off-the-shelf resonant axial scanning lens that changes the focal plane hundreds of thousands of times per second. This lens was used to rapidly scan the laser beam across different depths within the brain and allowed the team to reconstruct continuous 3D images.
