Line-scanning fiber bundle endomicroscopy with a virtual detector slit.

Michael Hughes,Guang-Zhong Yang

doi:10.1364/boe.7.002257

Abstract

Coherent fiber bundles can be used to relay the image plane from the distal tip of an endomicroscope to an external confocal microscopy system. The frame rate is therefore determined by the speed of the microscope's laser scanning system which, at 10-20 Hz, may be undesirably low for in vivo clinical applications. Line-scanning allows an increase in the frame rate by an order of magnitude in exchange for some loss of optical sectioning, but the width of the detector slit cannot easily be adapted to suit different imaging conditions. The rolling shutter of a CMOS camera can be used as a virtual detector slit for a bench-top line-scanning confocal microscope, and here we extend this idea to endomicroscopy. By synchronizing the camera rolling shutter with a scanning laser line we achieve confocal imaging with an electronically variable detector slit. This architecture allows us to acquire every other frame with the detector slit offset by a known distance, and we show that subtracting this second image leads to improved optical sectioning.

Highlights

In endoscopic microscopy, or ‘endomicroscopy’, coherent fiber bundle image guides provide a convenient means of relaying images from the tissue to external microscope optics [1,2,3,4,5]
For many applications there is a clear decrease in image quality compared to confocal imaging [17], and high-resolution microendoscope (HRME) is not used with intravenous fluorescein, where the out-of-focus signal is significantly greater
We provide the first demonstration of line-scanning fiber bundle endomicroscopy using the rolling shutter of a CMOS scanner as a virtual detector slit

Summary

Introduction

‘endomicroscopy’, coherent fiber bundle image guides provide a convenient means of relaying images from the tissue to external microscope optics [1,2,3,4,5] This is advantageous for confocal imaging because the laser scanning system can sit outside of the patient. Widefield epi-fluorescence illumination endomicroscopy (known as high resolution microendoscopy or HRME) [12] has been validated for a number of applications, including for diagnosis of esophageal [13], oral [14], cervical [15] and bowel [13] cancers It has the advantage of significantly reduced complexity due to the use of incoherent, non-scanned illumination, but as a result does not offer optical sectioning. Structured illumination techniques can be used to achieve optical sectioning under widefield illumination [17,18,19,20], but generally at the expense of introducing motion artifacts [19] and reducing the signal to noise ratio [17] and image bit depth

Methods

Results

Discussion

Conclusion