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Several observational studies on the association between Cd exposure and risk of prostate cancer have yielded inconsistent results. To address this issue, we conducted a meta-analysis to evaluate the correlation between Cd exposure and risk of prostate cancer. Relevant studies in PubMed and Embase databases were retrieved until October 2015. We compared the highest and lowest meta-analyses to quantitatively evaluate the relationship between Cd exposure and risk of prostate cancer. Summary estimates were obtained using a random-effects model. In the general population, high Cd exposure was not associated with increased prostate cancer (OR 1.21; 95% CI 0.91–1.64), whereas the combined standardized mortality ratio of the association between Cd exposure and risk of prostate cancer was 1.66 (95% CI 1.10–2.50) in populations exposed to occupational Cd. In addition, high D-Cd intake (OR 1.07; 95% CI 0.96–1.20) and U-Cd concentration (OR 0.86; 95% CI 0.48–1.55) among the general population was not related to the increased risk of prostate cancer. In the dose analysis, the summary relative risk was 1.07 (95% CI 0.73–1.57) for each 0.5 μg/g creatinine increase in U-Cd and 1.02 (95% CI 0.99–1.06) for each 10 μg/day increase of dietary Cd intake. However, compared with nonoccupational exposure, high occupational Cd exposure may be associated with the increased risk of prostate cancer. This meta-analysis suggests high Cd exposure as a risk factor for prostate cancer in occupational rather than nonoccupational populations. However, these results should be carefully interpreted because of the significant heterogeneity among studies. Additional large-scale and high-quality prospective studies are needed to confirm the association between Cd exposure and risk of prostate cancer.

To realize the calibration of a camera and a light plane in the line structured light sensor simultaneously,a calibration method was proposed based on a single plane calibration target which contains a concentric circle and two orthogonal lines passing through its center.Firstly,several images of model plane were captured from different orientations,and the camera parameters were determined via computing conjugated points linearly and were optimized according to the orthogonal constraints.Then,by moving the sensor for several times freely and keeping the light plane intersecting with the concentric circle,the perspective-three-points(P3P) model was implemented,and the 3D coordinates of calibration points on the light plane were computed.Finally,the light plane equation was derived eventually using the least square algorithm.Experimental results indicate that this calibration method has high accuracy,its average measuring accuracy is 0.036 82 mm,and relative error is about 0.277 13%.This calibration method requires only one target to complete the calibration of camera parameters and light plane equation,therefore,the calibration cost is reduced.It is characterized by simple calculation,easy operation and suitable for calibration in fields.

A calibration approach based on active vision for a light plane is proposed to achieve the self-calibration of a line structured light sensor.The proposed method is different from the previous plane fitting methods using the target points on the light plane,and the entire calibration process can be accomplished in two steps by several translational motions of a sensor.Firstly,the projections of parallel lines in the light plane are captured through some translational motions,and the normal vector of light plane is obtained via computing vanishing points.Then,in order to satisfy the model of perspective-three-points,the sensor is controlled to move along the set direction twice which is perpendicular to the normal vector,and the distance from the origin of camera coordinate system to the light plane is derived eventually.Experimental result shows that this calibration method has high accuracy,its average measuring accuracy is 0.015 4 mm,and relative error is about 0.183 0%.This calibration approach belongs to the self-calibration method without calibration targets,therefore,the calibration cost is reduced.It concludes that the whole process is easy,flexible and suitable for calibration on sites.

A novel 3D digital dental scanning system is introduced in this paper. The system is consisted of some action-controlling units and one structured light vision sensor. The scanning principle, the kinematic model and the calibration algorithm are discussed in detail. It is concluded that, from experiment, the scanning precision can be reached 0.18mm and 8000 pts can be obtained per second in the system. The dental scanning system can be used to reconstruct 3D model of dental wax conveniently.