Research On Fiber-Optic Photoacoustic Endoscopy

Colorectal cancer is one of the major diseases that endanger human health.It has the characteristics of high incidence,fast growth and easy transfer,which poses a serious threat to the lives of patients.Early detection and early diagnosis are the best strategies for cancer prevention and treatment,and can significantly improve the cure rate of colorectal cancer.Precise screening is essential for diagnosis of early tumors.Photoacoustic endoscope is a new type of non-invasive medical imaging technology.Compared with traditional endoscopy,it has high spatial resolution,high contrast and can provide a certain penetration depth.Photoacoustic endoscope has application prospects in the diagnosis of diseases and cardiovascular diseases.However,due to the limitation of the core functional device of the photoacoustic imaging system—the piezoelectric ultrasonic sensor,the existing photoacoustic endoscopy cannot balance the small probe size and superior imaging capability.In response to this problem,we use fiber-optic ultrasound sensors as the core functional unit,develop a small-size,high-resolution fiber-optic photoacoustic endoscope,and perform noninvasive threedimensional endoscopic imaging of the animal rectum.The main research contents of this article are as follows:(1)Designed and constructed a photoacoustic endoscopic probe with a fiber-optic ultrasonic sensor as the core function.We take advantage of the unique advantages of the fiber laser sensor,such as small size,high sensitivity,and no need for photoacoustic confocal.It is placed in an endoscopic probe with a diameter of 2.3 mm.The lateral spatial resolution of the probe is 10 ?m and the axial spatial resolution is 150 ?m,imaging depth of field can reach 1 mm.For performance characterization,we used this probe to carry out two-dimensional scanning photoacoustic micro imaging of Magnolia leaf veins and live mouse ear,Experimental result shows that the details of leaf veins and the capillaries in the ears of mice were clearly visualized.(2)Based on the optical fiber photoacoustic endoscopic probe,we performed vivo three-dimensional endoscopic imaging of the rat rectum with an imaging length of 6.3mm,an imaging frame rate of 1 Hz,a coverage angle of 285 °,and an excitation light energy of only 200 n J.This system demonstrates the spatial distribution of blood vessels at various levels in the inner wall of the rat rectum,and clearly show the capillaries in the submucosa and the larger branches of arteries and veins in the muscularis.Provides important physiological information for medical research through non-invasive means.