Development and evaluation of a light emitting diode endoscopic light source Neil T. Clancy* 1,2 , Rui Li 1,2 , Kevin Rogers 3,4 , Paul Driscoll 4 , Peter Excel 5 , Ron Yandle 4 , George Hanna 2 , Nigel Copner 3,4 , Daniel S. Elson 1,2 1 Hamlyn Centre for Robotic Surgery, Imperial College London, UK; 2 Department of Surgery and Cancer, Imperial College London, UK; 3 Faculty of Advanced Technology, University of Glamorgan, UK; 4 Cymtec Ltd. Cardiff, UK; 5 Glyndwr University, Wrexham, UK ABSTRACT Light-emitting diode (LED) based endoscopic illumination devices have been shown to have several benefits over arc- lamp systems. LEDs are energy-efficient, small, durable, and inexpensive, however their use in endoscopy has been limited by the difficulty in efficiently coupling enough light into the endoscopic light cable. We have demonstrated a highly homogenised lightpipe LED light source that combines the light from four Luminus LEDs emitting in the red, green, blue and violet using innovative dichroics that maximise light throughput. The light source spectrally combines light from highly divergent incoherent sources that have a Lambertian intensity profile to provide illumination matched to the acceptance numerical aperture of a liquid light guide or fibre bundle. The LED light source was coupled to a standard laparoscope and performance parameters (power, luminance, colour temperature) compared to a xenon lamp. Although the total illuminance from the endoscope was lower, adjustment of the LEDs’ relative intensities enabled contrast enhancement in biological tissue imaging. The LED light engine was also evaluated in a minimally invasive surgery (MIS) box trainer and in vivo during a porcine MIS procedure where it was used to generate ‘narrowband’ images. Future work using the violet LED could enable photodynamic diagnosis of bladder cancer. Keywords: Light-emitting diode (LED), laparoscopy, minimally-invasive surgery 1. INTRODUCTION Minimally-invasive surgery (MIS) has enabled diagnosis and intervention for patients in a manner that minimizes trauma and reduces recovery time. During these procedures the surgeon does not have a direct line-of-sight to the area under investigation and is therefore dependent on the quality of the imaging system to relay information on the health of the tissue as well as its general appearance. Due to the high attenuation of visible light in biological tissue and the relatively poor light coupling ability of endoscopes, the quality of the light delivery system is of utmost importance. The current standard light source for most MIS procedures, particularly laparoscopy, is the xenon arc lamp, which emits over a broad spectrum across the visible range, providing a colour close to daylight. These lamps are high power but highly inefficient, requiring approximately 300 W of electrical power to deliver just over 1 W of optical power. They are also expensive, requiring an initial payment of about $8000 and $1500 for replacement bulbs, which have a relatively short lifetime. Alternative sources such as laser-phosphor fibres and supercontinuum lasers have been explored but these have tended to focus on niche areas that require specialized lighting such as narrow lumen work and the single access surgery regime 1 where high optical power per cross-sectional area is required. A more significant limitation is perhaps the fact that these devices are currently limited to research models. Commercial devices have focused on providing the surgeon with more information by enhancing contrast in the tissue. This has been achieved using fluorescence to aid visualization of tumours 2 , and narrowband imaging (NBI) to increase the visibility of the vasculature 3 . However, separate systems are required for each of these approaches, leading to increased expenditure. Previous work has indicated that tip-mounted *n.clancy@imperial.ac.uk; imperial.ac.uk/roboticsurgery Advanced Biomedical and Clinical Diagnostic Systems X, edited by Tuan Vo-Dinh, Anita Mahadevan-Jansen, Warren S. Grundfest, Proc. of SPIE Vol. 8214, 82140R · © 2012 SPIE CCC code: 1605-7422/12/$18 · doi: 10.1117/12.909331 Proc. of SPIE Vol. 8214 82140R-1 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/05/2015 Terms of Use: http://spiedl.org/terms