| 【Background】 The accurate measurement of the length or areas of the wounds or the scar on the human body surface caused by traffic accidents,occupational injury and intentional injury is the difficulty in forensic clinical medicine. The examiner who utilize traditional measurement methods(such as ruler, tracing method, the rule of palms, photographic method,etc.) is easily influenced by human factors and irregular, hyperplasia and contracture scars and other factors, the measurement error is large, easily lead to controversial identification.With the development and maturity of the three-dimensional scanning technology(3D), it has been gradually applied to oral, plastic, and other fields of medicine in recent years. The study on applying the three-dimensional scanning technology to the measurement of body surface area gains more attention. Surface structured light three-dimensional scanning technology(SSL-3D), as a ideal scanning measurement techniques with the high speed and accuracy, has not been reported currently in related domestic and foreign research about measuring length and surface area of injury scar. This study was designed to compare the difference between and reliability of the three-dimensional surface structured light measurement technology and traditional measurement methods in the measurement of the length and surface area of the scar. Our aim is to develop a rapid 3D measuring method of scar length and area; it will meet the requirements of forensic science and have good value and social benefits.【 Obejective 】(1) Assessing the measurement accuracy of standard area and length of mannequin with SSL-3D technology;(2) Using SSL-3D technology to measure body scars,verify its accuracy, initially established a rapid 3D measuring technology of scar length and area, which will meet the requirements of forensic clinical medicine.【Methods】 The first experiment is measuring the length of the simulated linear scar. By using the traditional measurement tools(tape) and Power Scan-Ⅱ3D scanners(with two CCD cameras) respectively to measure 30 standard simulated linear scars which are adhered to mannequin maxillofacial.(These simulated linear scar divided into short and long scar group,wherein the short scar group(1-10cm) 15 cases, long scar group(15-30 cm, 15 cases). The measurement data(traditional measurement group data and 3D measurement group data) are compared with the standard data for statistical analysis.The second experiment is measuring the area of sheet scars. Using length×width method,pixel method, SSL-3D measurement method to measure standard analog sheet scar, which are affixed to the human body model, and real sheet scar of the patients. These standard analog sheet scars are divided into two groups, namely regular(25 cases) and irregular shape analog sheet scars(10 cases). The regular shape analog sheet scars are divided into a small area group(surface area≤25cm2, 10 cases) with smaller surface curvature and a large area group(150cm2≤ surface area ≤ 320 cm2, 15 cases)with bigger surface curvature. Using transparent graph paper tracing method to measure the patient scar(15 cases), and the measurement data will be a standard area group. Comparing length × width method area,pixel area, and 3D measurement area respectively with standard area for statistical analysis.The third experiment: reproducibility and reliability tests of SSL-3D measurement method. Before using the SSL-3D measurement method, using caliper and thin thread to measure 50 linear scars, and the data will be the standard group. Two laboratory personnel(A and B) apply the SSL-3D measurement method respectively to the measurement of 50 linear scars, the measurement data are divided into two groups(A group and B group). Then B use the SSL-3D measurement method to measure 50 linear scars once again. Each set of data and standards group are compared with intraclass correlation coefficient analysis.【 Results 】 The first experiment reveal that when measuring short linear scars group(1-10cm), there was no significant difference between the data from the traditional measurement(tape) and the standard data(t=0.72, P=0.48). While, there was significant difference between the data from the traditional measurement(tape) and the standard data(t=10.24,P<0.01), when measuring the long linear scars group(15-30cm), the measurement results of traditional measurements(tape) are shorter than the standard length. When applying SSL-3D measurement method to linear scars(short linear scars group and long linear scars group), the difference between the SSL-3D measurement results and the standard data was not statistically significant(1-10 cm group: t=﹣0.87,P= 0.40; 15-30cm: t=﹣1.06,P=0.31).The second experiment show that when measuring a small area group of the regular shape analog sheet scars with smaller surface curvature, There was no significant difference between the measurement results of the pixel method, the traditional measurement methods and 3D measurements method with the standard area(t/P value were﹣1.36/0.21, 0.48/0.64,0.72/0.49). When measuring large areas of regular shape analog sheet scars with bigger surface curvature, both of measurement results of length × width method and SSL-3D measurement method have no significant differences with the standard areas(t/P value were﹣1.24/0.24, 0.25/0.80), while measurement results of pixels method is significantly lower than the standard areas(t=8.51,P < 0.01); When measuring large areas of irregular shape analog sheet scars and patient sheet scar with bigger surface curvature, measurement results of length × width method are significantly higher than the standard area(t=-4.91, P<0.05),the measurement results of pixels method is significantly lower than the standard area(t=6.65, P<0.05), the measurement results with SSL-3D was no significant difference from standard area(t=0.30, P=0.77).The third experiment show that the two data groups from two experimenters using SSL-3D measurements method to measure scars have a high intraclass correlation coefficient,that is 0.998, and the two data groups from one experimenter using SSL-3D measurements method to measure scars twice also have a high intraclass correlation coefficient, that is 1.000.The intraclass correlation coefficient analysis between SSL-3D measurement data and standard method( caliper + thread method) data was made, and ICC is 0.996.【Conclusion】 That means when measuring the length of linear scars in the body surface,the tape measurement result was affected by the location and length of scars. These linear scars, which are cross-site, irregular or longer, is easy to have measurement error withtraditional method(tape); The length×width method which is commonly used in forensic case only applies to the area measurement of regular shape of sheet scars; Pixel method is not suitable for measuring the surface area of sheet scars with larger curvature. While SSL-3D measurement methods calculate surface area and length, by acquiring three-dimensional information of the sheet scar, is basically unaffected by surface curvature and scar locations.Two experimenters using SSL-3D measurements method to measure scars have a high intraclass correlation coefficient, and the two data groups from one experimenter using SSL-3D measurements method to measure scars twice also have a high intraclass correlation coefficient. That means the three-dimensional measurement techniques which is applied to measure body injury is not only accurate and reliable, but also has a unique advantage. |
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