University of Adelaide assesses ultra-sensitive low-light cameras for bioimaging

17 Mar 2025

Modern devices and quantum imaging can capture biological processes in their natural state.

Advances in low-light imaging are attractive for bioimaging applications, as they should reduce the risks of sample damage and phototoxicity.

The difficulty so far has been to maintain an image quality that captures the underlying biology of interest, one which can be used for quantitative measurements.

Fluctuations in pixel value induced by internal electronics, ie. camera noise, can predominate at low light levels, leading to qualitative degradation in the image and possible misinterpretation of data when used in quantitative analysis.

This is especially a concern for autofluorescence imaging, where vital molecular information is extracted through the quantitative imaging of weak fluorescence.

A project at the University of Adelaide has surveyed the performance of several modalities of low-light scientific camera, including electron-multiplying charge-coupled devices, scientific complementary metal oxide semiconductors (sCMOS), and photon-counting sCMOS architectures.

"Despite its major importance, the details and optimal use of scientific cameras remain opaque for many researchers," noted the project in its APL Photonics paper.

"Previous analyses of scientific cameras for biophotonics have typically focused on how to assess these cameras for noise statistics, without direct connection to the practicalities of biological imaging."

The findings indicate the current challenges in optical fluorescence imaging at low-light levels for quantitative microscopy, with an emphasis on live biological samples.

"Damage from illumination is a real concern which can often be overlooked," said Kishan Dholakia, director of the university's Centre of Light for Life. "Using the lowest level of light possible together with these very sensitive cameras is important for understanding biology in live and developing cells."

Subtle distinctions between modern camera platforms

The Adelaide project applied its selected camera types to imaging of live mouse embryos using two-photon light-sheet fluorescence microscopy, a modality especially suited for autofluorescence imaging but in which the intensity of fluorescence signals of interest can be inherently low.

It also explored how AI can be used to remove noise from the captured images, steps that "go beyond just putting the camera in the microscope to take pictures," commented Zane Peterkovic from the University of Adelaide.

The project's findings indicated some of the subtle distinctions between modern camera platforms, such as the ways in which electron-multiplying charge-coupled devices can attain sensitivities unreachable for sCMOS cameras, but do so while demonstrating excess noise that may diminish the reliability of those results.

"All else being equal, the read noise will determine the noise floor of the camera, but this value is defined only for a single pixel," noted the team in its paper.

"Low read noise may be necessary for photon counting experiments, but fluorescence microscopy differs from such studies, as the number of photons collected is of no consequence. Rather, the objective is to use the light intensity as a means of obtaining spatial information from a scene."

The Adelaide project now intends to carry out further investigates into the realm of quantum imaging, where quantum states of light may be used to further gain further information about the sample.