We report on novel hyper-spectral imaging filter-modules based on acousto-optic tuneable filters (AOTF). The AOTF
functions as a full-field tuneable bandpass filter which offers fast continuous or random access tuning with high filtering
efficiency. Due to the diffractive nature of the device, the unfiltered zero-order and the filtered first-order images are
geometrically separated. The modules developed exploit this feature to simultaneously route both the transmitted white-light
image and the filtered fluorescence image to two separate cameras. Incorporation of prisms in the optical paths and
careful design of the relay optics in the filter module have overcome a number of aberrations inherent to imaging
through AOTFs, leading to excellent spatial resolution. A number of practical uses of this technique, both for in vivo
auto-fluorescence endoscopy and in vitro fluorescence microscopy were demonstrated. We describe the operational
principle and design of recently improved prototype instruments for fluorescence-based diagnostics and demonstrate
their performance by presenting challenging hyper-spectral fluorescence imaging applications.
A novel prototype instrument for mutli-spectral imaging applications is described. The device is based on an acousto-optic tuneable filter (AOTF) that can be easily attached to many standard imaging systems (e.g. endoscope or fluorescence microscope). The instrument developed offers significant advantages over typical fixed-filter based systems in terms of flexibility, performance and diagnostic potential. The selected AOTF was designed to have a large acceptance aperture suitable for imaging applications. Any filtering centre-wavelength in the visible range (450 to 700nm) can be rapidly selected by either random access or by continuous tuning thus providing a versatile performance. The prototype instrument has been demonstrated for in-vivo applications where it was attached to the eyepiece of a commercial endoscope allowing simultaneous white light and fluorescence endoscopy. Autofluorescence of endogenous protoporphyrin IX (PpIX), a biomarker of diseased tissues undergoing an inflammatory response, was mapped in vivo on a rat model. The AOTF device was also coupled to the viewing port of a commercial fluorescence microscope thus realising a powerful fluorescence imaging spectrometer capable of detecting and mapping fluorescent biomolecules in vitro.
We describe the design and development two prototype spectroscopy imaging instruments based on custom-made acousto-optic tuneable filters (AOTF). These devices can be coupled to many standard imaging systems (e.g. an endoscope or a fluorescence microscope). The instruments developed offer significant advantages over typical fixed-filter imaging systems in terms of flexibility, performance and diagnostic potential. Any filtering wavelength in the visible range can be rapidly selected either by random access or continuous tuning. Since filtering is achieved through a diffractive process, an excellent signal-to-noise ratio is achieved that allows the detection of extremely low fluorescence signals such as autofluorescence. These adapters were designed to allow the simultaneous imaging of both the filtered and unfiltered signals. A first prototype instrument was developed and demonstrated for in-vivo applications. When attached to the eyepiece of a commercial endoscope, it allowed the simultaneous white light endoscopy and fluorescence imaging. Autofluorescence of protoporphyrin IX (PpIX), an endogenous chromophore that traces early-stage diseased tissue experiencing an inflammatory response, was mapped in vivo on a rat model. The system has also been approved for medical use and human clinical trials are underway. In addition, we are currently testing a second AOTF module for in vitro applications. This new AOTF adapter was designed to be coupled to the viewing port of a commercial fluorescence microscope to realise a fluorescence imaging spectrometer capable of detecting and mapping fluorescent biomolecules.
Two novel prototype instruments for in vivo fluorescence-based medical diagnostics are described. The devices are based on an acousto-optic tuneable filter (AOTF) and can be easily attached to the eyepiece of most commercially available endoscopes. The instruments developed offer significant advantages over typical fixed-filter or filter-wheel fluorescence imaging systems in terms of flexibility, performance and diagnostic potential. Any filtering center-wavelength in the range from 450 to 700 nm can be rapidly selected either by random access or sequential tuning using simple commands delivered over a PC serial interface. In addition, both filtered and unfiltered light can be imaged to facilitate the direct association of fluorescence signals with specific anatomical sites. To demonstrate the system in vivo, a study of the diagnostic potential of fluorescence imaging for pancreatitis was conducted on rats. The aim was to detect extremely low-levels of endogenous protoporphyrin IX (PpIX) that has been shown to accumulate in early-stage diseased tissue undergoing an inflammatory response. Results show clearly that the device is effective in diagnosing mild pancreatitis in rats without the necessity of administering PpIX promoting agents such as ALA. Planning of human clinical trials is currently underway to demonstrate its potential as a tool for non-invasive early diagnosis of gastroenterological diseases.
A prototype instrument for fluorescence-based medical diagnostics in vivo is described. The system consists of a rigid endoscope comprising a UV laser-source for fluorescence excitation and a white light source for direct imaging. An acousto-optic tuneable filter (AOTF) is employed as a full-field tuneable bandpass filter. This allows fast continuous or random-access tuning with high filtering efficiency. A study of the diagnostic potential of fluorescence imaging for pancreatitis was conducted on a rat model. In particular, the aim was to detect autofluorescence of endogenous protoporphyrin IX (PpIX) that has been shown to accumulate in early-stage diseased tissue undergoing an inflammatory response.