Abstract
Removing the comb artifact introduced by imaging fibre bundles, or ‘fibrescopes’, for example in medical endoscopy, is essential to provide high quality images to the observer. Multispectral imaging (MSI) is an emerging method that combines morphological (spatial) and chemical (spectral) information in a single data ‘cube’. When a fibrescope is coupled to a spectrally resolved detector array (SRDA) to perform MSI, comb removal is complicated by the demosaicking step required to reconstruct the multispectral data cube. To understand the potential for using SRDAs as multispectral imaging sensors in medical endoscopy, we assessed five comb correction methods with respect to five performance metrics relevant to biomedical imaging applications: processing time, resolution, smoothness, signal and the accuracy of spectral reconstruction. By assigning weights to each metric, which are determined by the particular imaging application, our results can be used to select the correction method to achieve best overall performance. In most cases, interpolation gave the best compromise between the different performance metrics when imaging using an SRDA.
Highlights
Fibrescopes relay elements of an image via total internal reflection of light along individual fibrelets of a flexible fibre optic bundle
Fibrescopes are used in many applications that exploit their small diameter and high flexibility, such as inspection of engines, fine diameter pipework and boilers[2], but they are still most prominent in medical imaging, where they are known as endoscopes
All metrics used for evaluation of the correction methods are defined in the Methods
Summary
Fibrescopes relay elements of an image via total internal reflection of light along individual fibrelets of a flexible fibre optic bundle. A commercial endomicroscope can capture high resolution in vivo ‘optical biopsy’ information by relaying a fluorescence signal emitted from a stain applied to the tissue (typically fluorescein) through a bundle of 30,000 fibrelets[10]. One example is the integration of multispectral imaging (MSI), which enables both spatial (x, y) and spectral (wavelength, λ) information to be recorded from the tissue. Reported spectrally resolved detector arrays (SRDAs) have the potential to overcome this problem by providing a robust compact solution for multispectral endoscopic imaging[22,38]. In fibrescope applications, the number of individual fibrelets further limits the spatial resolution and introduces a comb artifact into the images due to the opaque cladding between fibrelets. Processing multispectral fibrescope images, for example during image co-registration or feature classification, requires careful attention to both removal of the comb artifact (“decombing”) and separation of the spectral bands (“demosaicking”), in order to maintain image quality but perhaps more importantly, spectral fidelity[40]
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