Contrast-enhanced magnetic resonance imaging (MRI) is a novel approach to detect breast tumor, however, multiple 3D image sets need to be analyzed which causes unaffordable inspection tasks to physicians. Computer assistant detection is of great help to this situation and image segmentation is most important process of computer assistant detection. To segment the breast region from 3D MRI set, a multistage image processing procedure was proposed. Considering the morphological features of breast image, the image was divided into two parts to reduce the complexity of the segmentation procedure. For the anterior part of the image, the breast tissue was segmented from background using the region growing method. Meanwhile, the mean intensity of breast tissue was estimated. To segment the posterior part of the image, the estimated mean breast intensity was used to initialize an approximate boundary between breast and chest. The estimated intensity distribution of breast tissue was used to set the propagation term of following level set iterations. Based on this initialization, threshold-based 3D level set algorithm was used to seek the precise boundary between chest and breast. The level set algorithm achieves novel performance for the 3D segmentation of chest boundary. Based on the segmentation of one set of 3D image, the segmentation result was used as the initial boundary of following image sets to achieve automatic 4D segmentation. This multistage procedure greatly accelerates the convergence of the level set algorithm and reduces the chance of running into local minimum. Clinical data demonstrated that this processing procedure was effective for automatic segmentation of 4D breast MRI.

This paper proposed a method of using virtual markers to track the movement of the articular bearing surfaces of femur, tibia and patella simultaneously. With this method, the femur, tibia and patella were treated as three rigid body connected by soft tissue and thus the articular surface moves with corresponding bone in three dimensional (3D) space. The contact kinematics of articular bearing surface can be figured out by track the position and orientation of bones during knee flexion. To perform this method, three sets of tracking marker were attached tightly to femur, tibia and patella to track the 3D motion of lower limb. The articular bearing surfaces of knee joint were digitized to create three groups of registered virtual markers associated to the tracking markers of each bone, respectively. During knee flexion, 3D movement of femur, tibia and patella were tracked by capture the motion of tracking markers. Then the 3D coordinate of each virtual marker was calculated using the registration information of virtual markers. Thus, the trajectory of virtual markers could be tracked during knee flexion which indicates the real kinematics of bearing surfaces of knee joint. Three fresh-frozen lower limbs were tested before and after total knee replacement operation using this technique. The test results show that this method could be used to explore the contact condition of articular bearing surfaces accurately.

Image Guided Surgery (IGS) has been widely used in neurosurgical procedures to minimize invasion and to improve surgical accuracy. Registration is a key step of IGS, while Fiducial Localization Error (FLE) is an important factor affecting registration accuracy. FLE can be caused in both image domain (I-FLE) and physical domain (P-FLE). In this study, we design experiments to measure and compare the affecting factors on image FLE of point-based registration with special designed phantom. The results show that two factors affecting I-FLE are artificial picking and image voxel size. The artificial picking may cause the I-FLE average from 0.43±0.14mm to 0.74±0.26mm, and the voxel size may cause from0.43±0.14mm to 0.77±0.23mm. The artificial picking error can be reduced by improving the picking person’s experience, and we strongly recommend using smallest pixel spacing images for the registration. As for the selection of slice thickness, we find that the situation of Over-Sampling and Under-Sampling may occur, which would cause the thinner slice group of the image to get a higher I-FLE.

The revision of total hip arthroplasty (THA) is becoming an increasingly common procedure around the world. The extended trochanteric osteotomy (ETO) has proved to be an effective way in revision of THA. Four generations of trochanteric osteotomy fixation systems have been developed, all of which has its own clinical application. However, few studies on the biomechanical stability of the above fixation methods have been reported, though many clinical follow-up studies showed some postoperative functional differences among th em.Research in this field is mainly subject to constraints of measurement devices and 3D motion analysis. We designed a synchronous testing approach to acquire the tension data loaded to the greater trochanter and minimal rotation or migration of osteotomy fragment which could not be solved by strain gauge method. Active markers were designed to precisely track proximal femoral bed and the osteotomy fragment in 3D space. Six cadaver femurs constructed as vitro biomechanical models were chosen for a preliminary study. Each femur underwent the steps of prosthesis implanting, ETO and a series of five fixation methods in a random order with 2 wires, 3wires, 2 wires and a short claw plate,2 cables and a short claw plate, and a long claw plate. We also gave a preliminary result of the displacement of fragment and the stiffness of femur after ETO in this paper. Further clinical significance remains to be discussed.