The Frequency Domain System Based On Endoscopic Circumferential Scan And The Experimental Study With Imaging

Endoscopic Near-Infrared Diffuse Optical Imaging Technology (DOT) is a noveloptical measurement technique for the detection of the internal organs, which plays animportant role in early cancer diagnosis because of its real-time, non-invasivecharacteristics. To obtain the frequency-domain optical diffuse tomographic image ofthe cervix, an endoscopic imaging system of circumference scanning in effectivedetection range (EDR) has been developed, which is based on a frequency-domainsystem.Firstly, to achieve endoscopic detection, a novel endoscopic rotary probe withonly one source fiber and one detection fiber has been designed to simplify the systemand reduce the cost. The optical fiber parameters are obtained by the simulation andverification of Monte Carlo Algorithm. To acquire the efficient light perpendicular tothe cervical inner wall, the top of GRIN lens which is placed at the top of source fiberto collimate light is cut to45°and the top of detection fiber is also cut to45°. Theexperiments for evaluating the rotational accuracy of probe proved that the maximumrelative error of the source fiber for measuring amplitude and phase is1.7%and0.13%, respectively. As to the detection fiber, the relative error of amplitude andphase is3.01%and0.58%, respectively.Secondly, to achieve automatic control, the frequency-domain system with therotary probe was integrated with software on the platform of LabVIEW to save timeand manpower. In this article, the experiments were conducted to verify the accuracyof the system. The relative error of the frequency-domain system in measuringamplitude and phase is12.3%and20.9%, respectively. According to theseexperimental results, the possible errors of the system were analyzed. Furthermore,the improvement measures methods were investigated to make better reconstructedresults of the system.Finally, in order to verify the imaging capability of the system, a series ofexperiments using the solid phantoms and tubular biological tissue were implemented.In the solid phantoms experiment with one target and two targets, the experimentalresults demonstrated that both the location and the size of the targets in the solidphantoms were reconstructed correctly. Two targets could also be clearly separated. The quantitative ratio (QR) of the reconstructed absorption coefficient and reducedscattering coefficient was over25%and20%, respectively. In the experiment usingtubular biological tissue, the results demonstrated that the location of the target wasreconstructed correctly. The QR of the reconstructed absorption coefficient andreduced scattering coefficient was over25.3%and18.7%, respectively. In conclusion,the reasonable reconstructed image can be obtained using the endoscopic imagingsystem of circumference scanning in EDR, which would promote the development ofendoscopic DOT from experiments to clinical practice.