Endoscopic measurement by virtual internal standard:Feasibility and accuracy
- VernacularTitle:虚拟内标内镜测量法的建立及其应用
- Author:
Youke LU
;
Fangyu WANG
;
Yuxiu LIU
;
Haijun WAN
;
Xinxin JIN
- Publication Type:Journal Article
- Keywords:
Endoscopy;
Measurement;
Internal standard;
Virtual;
Barrel distortion;
Fuzzy measurement;
Visual measurement
- From:
Journal of Medical Postgraduates
2003;0(05):-
- CountryChina
- Language:Chinese
-
Abstract:
Objective: Endoscopic measurement mainly depends on visual estimation or open biopsy forceps,which have been proved lacking in accuracy due to the image barrel distortion caused by wide-angle lens in endoscope.This study aimed to validate a new concept of "virtual internal standard" proposed by ourselves and develop a new method for endoscopic measurement based on the concept.Methods: We photographed planar grid graphs printed with standard calibrations with an electronic endoscope at different object distances,obtained the information on the virtual internal standard from each photo at the corresponding object distance,and analyzed the digital characteristics of the barrel distortion photos,including the size of the visual field,the image compression ratio,and the credible area for measurement with the virtual internal standard.Based on the analyses,the method of endoscopic measurement by the virtual internal standard was established and experiments both in vivo and in vitro were conducted.Results: The ratio of the object distance to the visual field was 1 ∶ 2 when the former was between 10 mm and 40 mm.Calculation of the compression ratio showed that the credible area of measurement in the central area was 10 mm at the object distance of 10-15 mm,20 mm at 20-30 mm,and 30 mm at 30-50 mm.The credible area of measurement on various planes accounted for 2/5 to 3/5 of the total image width.There was a tendency of double-curve change in the arrangement of pixel values of the central grids on different planes.The differences between the pixel values per centimeter became slight at the object distance of 35-50 mm.Conclusion: Endoscopic measurement by the virtual internal standard is a objective,accurate,simple and practical method.
