Validation of a novel imaging approach using multi-slice CT and cone-beam CT to follow-up on condylar remodeling after bimaxillary surgery

The main goal of this study was to introduce a novel three-dimensional procedure to objectively quantify both inner and outer condylar remodelling on preoperative multi-slice computed tomography （MSCT） and postoperative cone-beam computed tomography （CBCT） images. Second, the reliability and accuracy of this condylar volume quantification method was assessed. The mandibles of 20 patients （11 female and 9 male） who underwent bimaxillary surgery were semi-automatically extracted from MSCT/CBCT scans and rendered in 3D. The resulting condyles were spatially matched by using an anatomical landmark-based registration procedure. A standardized sphere was created around each condyle, and the condylar bone volume within this selected region of interest was automatically calculated. To investigate the reproducibility of the method, inter- and intra-observer reliability was calculated for assessments made by two experienced radiologists twice five months apart in a set of ten randomly selected patients. To test the accuracy of the bone segmentation, the inner and outer bone structures of one dry mandible, scanned according to the clinical set-up, were compared with the gold standard, micro-CT. Thirty-eight condyles showed a significant （P〈O.05） mean bone volume decrease of 26.4%_ 11.4% （502.9 mm3＋ 268.1 mm3）. No significant effects of side, sex or age were found. Good to excellent （ICC〉 0.6） intra- and inter-observer reliability was observed for both MSCT and CBCT. Moreover, the bone segmentation accuracy was less than one voxel （0.4 mm） for MSCT （0.3 mm __. 0.2 mm） and CBCT （0.4 mm _ 0.3 mm）, thus indicating the clinical potential of this method for objective follow-up in pathological condylar resorption.

An automatic optimization method for minimizing supporting structures in additive manufacturing

The amount of supporting structure usage has been a major research topic in layer-based additive manufacturing(AM)over the past years as it leads to increased fabrication time and decreased surface quality.Previous studies focused on deformation and topology optimization to eliminate the number of support structures.However,during the actual fabrication process,the properties of shape and topology are essential.Therefore,they should not be modified casually.In this study,we present an optimizer that reduces the number of supporting structures by identifying the prime printing direction.Without rotation,models are projected in each direction in space,and the basis units involved in the generation of support structures are separated.Furthermore,the area of the supporting structures is calculated.Eventually,the prime printing direction with minimal supporting area is obtained through pattern-searching method.The results of the experiment demonstrated that the printing area was reduced by up to 60%for some cases,and the surface quality was also improved correspondingly.Furthermore,both the material consumption and fabrication time were decreased in most cases.In future work,additional factors will be considered,such as the height of the supporting S Xiao-Jun Chen xiaojunchen@sjtu.edu.cn 1 Institute of Biomedical Manufacturing and Life Quality Engineering,State Key Laboratory of Mechanical System and Vibration,School of Mechanical Engineering,Shanghai Jiao Tong University,Shanghai 200240,P.R.China 2 OMFS-IMPATH Research Group,Department of Imaging and Pathology,Faculty of Medicine,Katholieke Universiteit Leuven,Leuven,Belgium 3 Department of Oral and Maxillofacial Surgery,University Hospitals Leuven,Leuven,Belgium structures and the adhesion locations to improve the efficiency of this optimizer.