The purpose of this study was to compare the shaping effects of three nickel-titanium rotary instruments, ProTaper, K3, and RaCe, with emphasis on canal transportation. Simulated canals with an S-shaped curvature in clear resin blocks were prepared with a torque-control, low-speed engine. Canals were prepared using the crown-down technique to the size of #30. Canal aberrations were assessed by comparing the pre- and postinstrumentation images under a stereomicroscope. ProTaper instruments caused greater widening of canals compared to K3 or RaCe. Furthermore, ProTaper files showed a tendency to ledge or zip formation at the end-point of preparation. These canal aberrations may be caused by ProTaper finishing files, which appear to be less flexible than other files of the same tip-size, because of their greater taper-size. These results suggest that nickel-titanium file systems including less tapered, more flexible instruments, like K3 and RaCe should be used in the apical preparation of canals with a complicated curvature.

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Purpose:The purpose of this study is to investigate the feasibility of a low cost, small size positioning assistance simulator system for skull radiography using the Microsoft Kinect sensor. A conventional radiographic simulator system can only measure the three‐dimensional coordinates of an x‐ray tube using angle sensors, but not measure the movement of the subject. Therefore, in this study, we developed a real‐time simulator system using the Microsoft Kinect to measure both the x‐ray tube and the subject, and evaluated its accuracy and feasibility by comparing the simulated and the measured x‐ray images.Methods:This system can track a head phantom by using Face Tracking, which is one of the functions of the Kinect. The relative relationship between the Kinect and the head phantom was measured and the projection image was calculated by using the ray casting method, and by using three‐dimensional CT head data with 220 slices at 512 × 512 pixels. X‐ray images were thus obtained by using a computed radiography (CR) system. We could then compare the simulated projection images with the measured x‐ray images from 0 degrees to 45 degrees at increments of 15 degrees by calculating the cross correlation coefficient C.Results:The calculation time of the simulated projection images was almost real‐time (within 1 second) by using the Graphics Processing Unit(GPU). The cross‐correlation coefficients C are: 0.916; 0.909; 0.891; and, 0.886 at 0, 15, 30, and 45 degrees, respectively. As a result, there were strong correlations between the simulated and measured images.Conclusion:This system can be used to perform head positioning more easily and accurately. It is expected that this system will be useful for learning radiographic techniques by students. Moreover, it could also be used for predicting the actual x‐ray image prior to x‐ray exposure in clinical environments.

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Purpose: Currently, dual energy subtraction is used for the separation of the soft tissue and bone. There are two methods of calculation: the filter method and the double tube voltage method. However, there are problems with these methods, such as an increase of exposure (double tube voltage method), and image quality degradation due to attenuation of x‐rays (filter method). In the present study, we have developed a new method of separating bone and soft tissue by using a single x‐ray exposure combined with object thickness measurement using the Microsoft Kinect sensor. Methods: We used a hand phantom as an object and measured the thickness of the object from a depth image obtained with the Microsoft Kinect. X‐ray images were taken at different tube voltages (40 kV, 60 kV, 80 kV), and thicknesses of the two components were calculated from x‐ray attenuation equation. A software program for an ImageJ Plugin was developed to obtain separated images, and the separated bone image was compared with the original image by visual evaluation and profile data. The thicknesses of the separated phalanx bones were also compared with those measured from CT images. Results: It was possible to obtain separated bone and soft tissue images using a single x‐ray exposure. The gray values of the bone were greatly enhanced while those of soft tissue were diminished. A comparison with the CT images showed that the bone thickness error was less than 20.0% in phalanx bones. Conclusion: It was shown that the image separation of bone and soft tissue was made possible by using a single x‐ray exposure combined with object thickness measurement. This method will be useful for the accurate evaluation of bone changes after a fracture without using any additional x‐ray exposure.