Imaging at the micron scale
Many biomedical applications such as optical microscopy and laser nano-surgery require the ability to focus light at the micron scale. However, the heterogeneity of biological tissues causes light scattering and prohibits efficient focusing. As a result, optical microscopy is currently restricted to superficial investigation of samples. However, accumulating evidence suggests that this random scattering can be controlled by high-resolution wavefront shaping. The EU-funded NOLIMIT (Nonlinearity-assisted optical focusing and imaging deep inside scattering media) project developed a novel approach based on photoacoustic (PA) transmission-matrix for imaging and light control. The generated apparatus included a conventional PA tomographic setup equipped with a high-resolution computer-controlled spatial light modulator. The ultimate goal was to overcome the resolution limit of deep-tissue optical techniques and improve microscopic imaging. Using the PA transmission matrix, scientists were able to focus light at any target within a visually opaque sample and at any position in a large field of view. The modulation of the photoacoustic signal allowed them to image absorbing structures that were invisible by conventional means. Additionally, the consortium developed an endoscopic imaging technique and passive acoustic imaging approach to generate images without using lenses or conventional scanners. This technique has great potential for miniaturisation of medical endoscopic imaging probes. Overall, the scientific achievements of the NOLIMIT study overcome the resolution limitations of deep-tissue optical techniques and should improve biomedical imaging. Researchers are hopeful that imaging embryonic development through the visually opaque shell of an egg will soon be realisable.
Keywords
Imaging, optical focusing, microscopy, resolution, photoacoustic transmission
