Development of a multi-spectral imaging system for medical applications

We describe the development of a multi-spectral imaging (MSI) system based on a rapid-scanning solid-state device, an acousto-optic tunable filter (AOTF), for wavelength selection and a two-dimensional charge-coupled device for detection. The MSI device is designed for in vivo optical detection in medical diagnostic applications. Unlike conventional grating spectrometers, the AOTF is a miniature solid-state device that has no moving parts, and can be rapidly tuned to any wavelength within its operating range. The large aperture of the AOTF and its high spatial resolution allows the optical image from an imaging fibre optic probe to be recorded by the detector. These characteristics, combined with their small size, make AOTFs important new alternatives to conventional monochromators, especially for spectral imaging in biomedical applications. The MSI can also be used for dual-modality diagnostics to detect both fluorescence and diffuse reflectance images. The usefulness and potential of the MSI system is illustrated in several applications of biomedical interest, such as reflectance fluorescence imaging of skin and brain tissues.