Research On Quality Control Qualitative Testing Technology Of Medical Endoscope’s Optical Performance

Research Objective and SignificanceCurrently endoscopes have developed into a complete system, classified by its development and imaging structure, endoscopes could be roughly divided into three categories:hard-tube endoscopy, optical fiber (tube type) endoscopy, medical ultrasound endoscopy and electronic endoscopy. Technology enables the development of medical endoscope which can achieve high vivid image display, high resolution, flexible operation, and they can almost stretch into any cavities or holes of human body, therefore they are widely used and welcome by the majority of medical workers.With minimally invasive surgery of medical endoscope increasing popularity, people’s understanding of the safety and efficacy of endoscopic clinical applications is gradually developing and deepening. The optical performance of the endoscope has a direct or indirect impact on patients’ safety, meanwhile, the emerging malpractice in minimally invasive endoscopic surgery which are both making it urgent to carry out quality performance testing work of medical endoscopes. It is of great clinical and social significance to launch quality performance testing work especially the detection of optical properties during the medical endoscopic quality control tests.For a long time, our country does not have a unified agency to regulate and manage endoscopic medical career. Skill levels vary around the area and endoscopic equipment sterilization does not meet specifications. Meanwhile, endoscopic equipment is of low quality and ongoing clinical endoscopy service is not in place that may cause medical endoscopes work adversely affected. Therefore, in order to avoid medical malpractice caused by endoscope quality, as well as to ensure the quality of the performance state of the endoscope, it is imperative to launch the establishment of medical endoscopes to test the quality of the performance for routine maintenance and decontamination work regulatory measures.Currently, a small number of relevant international and domestic research institutions carry out the research of medical endoscope detection device, and some of the research may have a high technical level. The endoscope quality control related work is of significance to the maintenance of endoscopy’s performance state and also provides an important safeguard security for the implementation of clinical endoscopic surgery. However, the work of domestic and foreign research institutions may face that test items do not match the national standards, industry standards, or a lack of important endoscopic test items index, or the problem of complex detection device and complicated detection methods. And almost medical research is conducted only for rigid endoscope, and it’s not designed for fiber mirrors and electronic endoscope that are more widely used.This paper is referring to the national standards, industry standards and testing specification of various types endoscopes, absorbing the advantages of similar research work, and taking the use of the existing work to develop a set of optical properties quality control qualitative detection device of medical endoscopes and corresponding method for optical detection project. And this detection device aims to meet the needs of medical endoscope optical performance state routine inspection maintenance, fault detection and receiving inspection, meanwhile, it also ensures quality of medical endoscopes in the best performance status and reduces medical malpractice due to medical endoscope caused by quality problems.Research Contents and MethodsThe innovation of this study lies in the rapid detection process, qualitative detection, extended detection object of medical rigid endoscope, fiber endoscope and electronic endoscope. And endoscopic system is detected as a whole. Corresponding thereto, this paper has developed a medical endoscope qualitative detection device detection target, and corresponding detection methods. The core content is the design of detect comparison card.In accordance with the relevant standards and practice research, this paper identifies five medical endoscope test items, including angle (field of view, direction of angle), visual resolution, geometric distortion, color reproduction ability and light efficiency. Each test item has a corresponding test target, test comparison card and corresponding contrast detection method.1. Angle1.1 Direction of view(1) Test content and significanceDirection of angle refers to the angle between the visual axis and the optic axis of the optical lens composed of the lens body, which can be on behalf of different human tissues orientation observed by endoscope.(2) Test target and test comparison cardTest target of direction of angle is the same as field of view’s, which is composed by four concentric circles of different radius.(3) Test methodMove the target holder so that the endoscope image captured by endoscope can be in proper size and position in the display. Then observe the target image, if the image is seriously deformed, it indicates that the endoscope’s direction of angle is detected to be unqualified, otherwise the test item is qualified.1.2 Field of view (FOV)(1) Test contents and significanceFOV refers to the maximum field angle of aperture height between center of optical lens and end of the object. FOV determines the observation range of endoscope in human body cavity. If the observation range is too small, it will cause the state of the lesion organization and the surroundings unknown, thus resulting in difficult diagnosis or treatment.(2) Test target and comparison cardTest target is FOV test target which contains four concentric circles of different radius. Content of test comparison card is common FOV of medical endoscopes and corresponding distance error range.(3) Test methodMake the test target image fill the entire field of medical endoscopes, then measure the distance between medical endoscope and target and the distance is denoted by D. Find the distance range of the corresponding theoretical FOV 6 in the FOV angle test comparison card, if D is located in the distance range, indicating FOV test is qualified, otherwise it’s unqualified.2. Visual resolution2.1 Test contents and significanceMedical endoscopes’ visual resolution refers to the maximum line pairs through the endoscope which human eye can distinguish. Resolution is the endoscopes’ key optical index. If endoscope is of poor detail resolution, lesion area and surrounding tissue characteristics will be lost, and endoscope will then lose its clinical significance.2.2 Test target and comparison cardResolution target contains 15 black and white line pairs in both horizontal and vertical direction and each line pair is of different density.2.3 Test methodObserve the target resolution images, and find the largest number of black and white line pairs that can be resolved. The number is the endoscopic resolution value. If the measured value is bigger than the theoretical value, the endoscope’s resolution test item is qualified. Otherwise, it’s unqualified.3. Geometric distortion3.1 Test contents and significanceIt refers to the differences between the peripheral magnification of endoscopic imaging optical system visual axis and the magnification of the visual axis center. Too large magnify differences between endoscope field center and the edge may lead to orientation confusion, visual errors, experience loss, losing confidence in diagnosis or surgery, even resulting in clinical harm.3.2 Test target and comparison cardGeometric distortion target is mesh structure composed by 100 same square rectangles made of a side length of 5mm. The gray annular region in test comparison card indicates the standard value and allowable tolerance limits, and other regions outside gray areas is white region which is out of the range of allowable error in distortion.3.3 Test methodCompare the transparent material distortion contrast card with the grid image in the display. If the distortion image is within the gray area of the distortion comparison card, indicating that the endoscopic geometric distortion test is qualified; on the contrary, if the distortion image is out of the gray area range, it indicates that the test is failed.4. Color reproduction ability4.1 Test contents and significanceIt refers to the ability of the endoscope to distinguish the color. If the ability of the endoscope to distinguish the color is poor, it may affect the field of view of human tissue observation and operation of the doctor, resulting in misdiagnosis or surgical failure.4.2 Test target and comparison cardTest target is constituted with a round of four equal area sectors of red, white, blue and yellow. The composition of test contrast card includes the standard color block and color blocks that are located within the range of allowable error.4.3 Test methodCompare the color from the display with the corresponding color from the card, if the color from the display is located in the comparison card, indicating that the test items qualified, otherwise unqualified.5. Light efficiency5.1 Test contents and significanceIt refers to the brightness difference rate between the endoscopic field center and the field edge. Effective brightness uniformity of image surface is important to the field of view and observation of normal tissue lesions, diagnosis and treatment.5.2 Test target and comparison cardLight efficiency target is composed of a circle with the gray value of 255. The composition of test comparison card is 20 rectangular block area of the same size with gray value uniformly changing.5.3 Test methodIdentify the gray scale blocks in the contrast card separately corresponding to the brightness of image center and the brightness of image edge, if the gray value difference between the edge and the center of the image is less than ten gray scale blocks, and then we can determine the endoscope light efficiency testing is qualified, otherwise unqualified.Results and conclusions1. Medical rigid endoscope(1) Mechanical properties such as burrs, scratches, reliable connection, appearance etc. of 11 endoscopes’are all meeting the requirements.(2) The error range of rigid endoscopes’direction of angle detected from 0°,12°, 30° to 70° are within±10°, in line with the requirements of testing standards; Error values of FOV are within the error range, and the maximum error is 13% of the 5th endoscope which is within the allowable range (±15% of the nominal value).(3) Visual resolution values are 8 (line pairs/mm) or above, all up to nominal value, in line with the requirements; geometric distortion values are all less than 0.3, in line with the standard requirements; The test error of light efficiency are all below 37.8%, less than the maximum required value of 50%, tested qualified.(4) The average error values of color reproduction of three endoscopes including 2nd endoscope,7th endoscope and 11th endoscope are bigger than 20%, which don’t meet the standard requirements, indicating test item failed.Through comparison analysis, among 1st endoscope,2nd endoscope and 3rd endoscope of three LUT HD scope sinus endoscope,3rd has the best performance of status,1st endoscope following by, and the 2nd has the worst the performance of status; Among three colors red, green and blue, rigid endoscopes have the worst reproduction capability of blue, the reproduction capability of red color followed by, and the color reproduction capability of green is the best. The 5th,6th,8th and 9th endoscopes’color reproduction ability is better in 11 rigid endoscopes.2. Electronic Endoscope(1) Mechanical properties detection such as burrs, scratches, controlled bending, reliable connection, appearances etc. of 11 electronic endoscopes’all meet the requirements.(2) FOV detection error values are all qualified, the maximum error value is 8% of the 6th endoscope, less than the 15% error tolerance range; Detection of visual resolution and geometric distortion are all qualified, and geometric distortion error values are within the allowable 30% error range.(3) The maximum error value of light efficiency detection is 26.4%, of the 10th endoscope, less than the required maximum error value.(4) 1st endoscope,10th endoscope and 11th endoscope failed in the detection of color reproduction ability.Through comparison analysis, among No.1-5 enteroscopy, the FOV error value, the light efficiency error value and the color reproduction error value of the 5th OLYMPUS duodenoscope are all less than the other four enteroscopy, so the quality of performance state of the 5th is the best. The quality performance state of the 7th Gastroscopy is the best in 6-9 Gastroscopy, and the 8th Gastroscopy’s quality performance state is poor. In the two bronchoscopys, the quality state performance of the 11th bronchoscopy is better than the 10th.The medical endoscope qualitative detection device proposed by this paper is capable of launching rapid qualitative optical items detection of medical endoscopes, and all the test items are summarized from endoscopic detection standard and clinical experience in the field. Test results and medical endoscope factory theoretical data have consistency, and this endoscopic detection device is suitable for carrying out routine inspection and maintenance work by endoscope health care work users.Inadequate and Prospects1. Inadequacies of researchDetection objects:limits of the objective conditions lead to small detection sample size, resulting in short statistics data; lack of fiber endoscope detection cause of technical constraints and objective conditions.Detection items:the existing five test items may not be able to fully reflect the optical performance characteristics of medical endoscopes.Detection target:the target is condensing surface so the center is too bright, affecting observation.Detection device:the entire device is too heavy to handling; when target rises to a certain height the target holder beams may block in the target image; trench is too wide which may result that a smaller diameter of the endoscope can not be clamped tight.2. Prospects of researchNext phase of research task will be to improve detection device’s weight, size and other aspects; to increase detection sample size and detection work of fiber endoscope, then do further testing to improve detection device. Subsequent research will be to improve or perfect detection device, detection items and targets, and to put detection device into application.