At a Glance
Researchers at Colorado State University have developed and patented a new optical imaging platform technology for rapid 3D imaging, even in highly scattering tissues. Dubbed Coherent Holographic Image Reconstruction by Phase Transfer, or CHIRPT, this imaging method allows transfer of propagation phase of coherent illumination light to incoherent emission, enabling large increases in three-dimension imaging speed and image volumes in epi-collected fluorescent light.
Within medical research as well as clinical applications is the need for advanced imaging technologies that can dynamically and non-invasively image large volumes (e.g., whole brains). While conventional diffractive imaging techniques are commonly utilized, a major limitation of these methods is that light collected by the optical detector must be coherent, thus ruling out the ability to utilize incoherent light emissions, such as fluorescence. This is unfortunate, as fluorescent tagging is pervasive in biological sciences owing to its molecular specificity, which allows for labeling of targeted processes.
Although a few techniques exist that utilize fluorescent emission (e.g., optical scanning holography, fluorescence incoherent correlation holography), these methods are slow and unsuitable for dynamic volumetric imaging of 3D samples.
Researchers at Colorado State University are developing several related optical technologies that will enable dynamic, 3D imaging utilizing fluorescence-based emission. The power of their approach has been demonstrated experimentally using a coherent diffraction tomographic imaging technology with rates exceeding 350 planes/second (~11.7x video rate) and unprecedented imaging volumes (6 mm3, up to at least 1 cm3 appears possible) within tissues that exhibit optical scattering (normally difficult to image). Images have been collected in an epi-fluorescent configuration with a single element optical detector – an attractively simple setup for any application, but essential for applications requiring single port access (e.g., in vivo murine brain scans).
The core innovation utilized by the CSU technologies is relatively straightforward but incredibly powerful and versatile. Whereas incoherent light (including fluorescence) does not contain the propagation phase information required for conventional diffractive imaging techniques (usually based on interferometry), the CSU technologies are able to impart a frequency to the intensity of the incoherent light that depends on the physical location that the light originates from. The result is that each point on a plane within the sample will produce fluorescence with a different intensity pattern. Utilizing sophisticated mathematics and scanning of the instrument across multiple planes, a 3D image of the fluorescence can be generated.
The technology has been validated and demonstrated in an experimental proof-of-concept setup. With funding, a larger scale prototype will be developed. It is anticipated that this prototype will allow for whole brain imaging of murine samples (both excised and in vivo) without any need for physical manipulation (e.g., slicing). In contrast to conventional techniques that can require up to a month, it is expected that whole brain images will be collected over a matter of hours – a dramatic improvement. For clinical imaging, depths of up to 5 mm are possible. The equipment is cost effective and relatively simple.
- Does not require coherent light signal, suitable for fluorescence-based imaging.
- Rapid – single detector, large field of view, collects ata in an entire plane with “one shot”.
- Simple, cost effective, and amenable to single port access (e.g., no in vivo murine brain imaging) by virtue of the single detector, epi-fluorescence configuration.
- Versatile – whole brain imaging, optical cancer biopsies, oxygenation levels, and other biomedical applications within research and clinical setting.
Early applications of these technologies are likely to be for scientific research with clinical applications to follow. This technology will be well-suited for applications where there is a demand for rapid, high-throughput 3D imaging of scattering tissues where only non-coherent light signals may be obtained (e.g., fluorescence-based microscopy). It may also be possible to incorporate LED light sources and fiber optic probe configurations for endoscope applications.
The technique is suitable for a wide variety of incoherent optical imaging (not just fluorescence), such as:
- Whole brain optical imaging
- Optical biopsies for cancer imaging
- Oxygenation levels
- Other biological and biomedical applications are anticipated.
Last updated: March 2023