Wurong Yu

Evaluation of a rotary laser body scanner for body volume and fat assessment

This paper reports the evaluation tests on the reliability and validity of a 3-dimensional (3D) laser body scanner for estimation of body volume and % fat. Repeated measures of body imaging were performed for reproducibility analysis. Validity of the instrument was assessed by comparison of measures of body volume by imaging to hydrodensitometry, and body fat was compared to hydrodensitometry and dual energy X-ray absorptiometry. Reproducibility analysis showed little difference between within-subjects measurements of volume (ICC ≥ 0.99, p < 0.01). Body volume estimations by laser body scanner and hydrodensitometry were strongly related (r = 0.99, p < 0.01), and agreement was high (ICC = 0.99, p < 0.01). Measurements of % body fat also agreed strongly with each other between methods (ICC = 0.86, p < 0.01), and mean % fat estimates by body imaging did not differ from criterion methods (p > 0.05). These findings indicate that the 3D laser body scanner is a reliable and valid technique for the estimation of body volume. Furthermore, body imaging is an accurate measure of body fat, as compared to dual energy X-ray absorptiometry. This new instrument is promising as a quick, simple to use, and inexpensive method of body composition analysis.

A portable stereo vision system for whole body surface imaging

This paper presents a whole body surface imaging system based on stereo vision technology. We have adopted a compact and economical configuration which involves only four stereo units to image the frontal and rear sides of the body. The success of the system depends on a stereo matching process that can effectively segment the body from the background in addition to recovering sufficient geometric details. For this purpose, we have developed a novel sub-pixel, dense stereo matching algorithm which includes two major phases. In the first phase, the foreground is accurately segmented with the help of a predefined virtual interface in the disparity space image, and a coarse disparity map is generated with block matching. In the second phase, local least squares matching is performed in combination with global optimization within a regularization framework, so as to ensure both accuracy and reliability. Our experimental results show that the system can realistically capture smooth and natural whole body shapes with high accuracy.

3-D Surface Reconstruction and Evaluation of Wrinkled Fabrics by Stereo Vision

This paper presents a stereo vision system for reconstructing the three-dimensional (3-D) surface of a wrinkled fabric and for detecting and characterizing wrinkles to evaluate the severity of wrinkling. The system captures a pair of images through two 10.2-megapixel digital cameras, performs subpixel stereo matching based on correlation gradients, and yields a depth resolution under 0.1 mm. The matching algorithm is realized in a regularization framework and implemented by the finite-element method, in which the disparity map is parameterized by dense bicubic B-splines. The outputs of the system include a wrinkle map that depicts the locations of the ridges of individual wrinkles and quantitative data on wrinkle density, amplitude, and sharpness for a tested sample.

Validation of a 3-dimensional laser body scanner for assessment of waist and hip circumference.

Objectives: To evaluate the reliability and validity of a 3-dimensional laser body scanner for estimation of waist and hip circumferences and waist:hip ratio. Methods: Seventy women were evaluated for waist and hip circumference and waist∶hip ratio via laser scanner and tape measure. In a subset of 34 participants, 8 repeated measures of laser scanning were performed for reproducibility analysis. Validity of the instrument was assessed by regression and Bland-Altman comparison of measures of waist and hip circumferences and waist∶hip ratio to tape measure. Results: Reproducibility analysis showed little difference between within-subjects measurements of circumferences (intraclass correlation coefficient ≥0.992, p < 0.01). Evaluation of waist and hip circumferences measured by body scanning did not differ significantly from tape measure (p > 0.05). Bland-Altman analysis showed no bias between laser scanning and tape measure. Conclusion: These findings indicate that the 3-dimensional laser body scanner is a reliable and valid technique for the estimation of waist and hip circumferences as compared with tape measure. This instrument is promising as a quick and simple method of body circumference analysis.

Surface Reconstruction from Two-view Body Scanner Data

We propose an effective algorithm based on subdivision surface representation for reconstruction of the human body from the data of a two-view body scanner. In the case that the scan data can be grouped into front and back views, we firstly rearrange the data by resampling in the frontal projection plane, and triangulate each set of data points followed by zippering the front and back contours with an Add—Delete method to create an initial mesh. Then the initial mesh is simplified to produce a control mesh as the base of a subdivision surface. Finally, the control mesh is optimized by fitting its subdivision surface to the original data, and, accordingly, a piecewise smooth body model is reconstructed. Experimental results show that the algorithm is capable of gap and hole filling, is robust to noise, and is computationally efficient.We propose an effective algorithm based on subdivision surface representation for reconstruction of the human body from the data of a two-view body scanner. In the case that the scan data can be grouped into front and back views, we firstly rearrange the data by resampling in the frontal projection plane, and triangulate each set of data points followed by zippering the front and back contours with an Add—Delete method to create an initial mesh. Then the initial mesh is simplified to produce a control mesh as the base of a subdivision surface. Finally, the control mesh is optimized by fitting its subdivision surface to the original data, and, accordingly, a piecewise smooth body model is reconstructed. Experimental results show that the algorithm is capable of gap and hole filling, is robust to noise, and is computationally efficient.

Three-dimensional surface imaging system for assessing human obesity

The increasing prevalence of obesity suggests a need to develop a convenient, reliable, and economical tool for assessment of this condition. Three-dimensional (3-D) body surface imaging has emerged as an exciting technology for the estimation of body composition. We present a new 3-D body imaging system, which is designed for enhanced portability, affordability, and functionality. In this system, stereo vision technology is used to satisfy the requirement for a simple hardware setup and fast image acquisition. The portability of the system is created via a two-stand configuration, and the accuracy of body volume measurements is improved by customizing stereo matching and surface reconstruction algorithms that target specific problems in 3-D body imaging. Body measurement functions dedicated to body composition assessment also are developed. The overall performance of the system is evaluated in human subjects by comparison to other conventional anthropometric methods, as well as air displacement plethysmography, for body fat assessment.

Efficacy of thigh volume ratios assessed via stereovision body imaging as a predictor of visceral adipose tissue measured by magnetic resonance imaging

The research examined the efficacy of regional volumes of thigh ratios assessed by stereovision body imaging (SBI) as a predictor of visceral adipose tissue measured by magnetic resonance imaging (MRI). Body measurements obtained via SBI also were utilized to explore disparities of body size and shape in men and women.

Evaluating fabric fuzziness using laser range sensing

This paper introduces a high-resolution 3-D scanning system for objective evaluation of fabric fuzziness using laser range-sensing technology. This system consists of a laser range sensor, a 2-D mechanical stage, and a computer with dedicated software. The paper covers the process of surface digitization from 3-D scanning, image-processing techniques for surface feature description, and methods for characterization of fabric fuzziness. It also reports a preliminary test on a set of fabrics that were treated in different laundering cycles to gain different levels of fuzziness. The test demonstrates that this system has great potential for discriminating among fabric fuzziness levels in a quantitative and reliable manner.

A sub-pixel stereo matching algorithm and its applications in fabric imaging

In this paper, we describe a sub-pixel stereo matching algorithm where disparities are iteratively refined within a regularization framework. We choose normalized cross-correlation as the matching metric, and perform disparity refinement based on correlation gradients, which is distinguished from intensity gradient-based methods. We propose a discontinuity-preserving regularization technique which utilizes local coherence in the disparity space image, instead of estimating discontinuities in the intensity images. A concise numerical solution is derived by parameterizing the disparity space with dense bicubic B-splines. Experimental results show that the proposed algorithm performs better than correlation fitting methods without regularization. The algorithm has been implemented for applications in fabric imaging. We have shown its potentials in wrinkle evaluation, drape measurement, and pilling assessment.

A 3D surface imaging system for assessing human obesity

The increasing prevalence of obesity suggests a need to develop a convenient, reliable and economical tool for assessment of this condition. Three-dimensional (3D) body surface imaging has emerged as an exciting technology for estimation of body composition. This paper presents a new 3D body imaging system, which was designed for enhanced portability, affordability, and functionality. In this system, stereo vision technology was used to satisfy the requirements for a simple hardware setup and fast image acquisitions. The portability of the system was created via a two-stand configuration, and the accuracy of body volume measurements was improved by customizing stereo matching and surface reconstruction algorithms that target specific problems in 3D body imaging. Body measurement functions dedicated to body composition assessment also were developed. The overall performance of the system was evaluated in human subjects by comparison to other conventional anthropometric methods, as well as air displacement plethysmography, for body fat assessment.