改进Mask R-CNN网络在医学图像识别与分割中的应用

针对现有医学图像处理方法在人体复杂结构组织器官分割中的不足,提出复用低层特征信息的Mask R-CNN网络。该网络可对特定组织器官识别时同时进行分割,为了提高包含较多细节信息的低层特征层的利用率,将低层的特征信息添加到高层的特征中,使低层与高层特性优劣互补,将原始图像首次长宽压缩两次后的特征层定义为C1层,而后分别通过复用C1层和复用依次卷积的C1层这两种方法实现。并将主干网络进行了精简,以加快网络的训练速度,降低识别和分割的时间。以下颌骨作为应用对象,自建包含1?064张下颌骨CT图片的数据集,按9∶1的比例划分为训练集和验证集进行训练,使得复用依次卷积C1层的Mask R-CNN网络的训练损失降至2.8%,验证损失降至6.6%,表明该网络在下颌骨的识别和分割上具有很高的准确率。     

颅颌面整复术前规划虚拟截骨研究

虚拟外科手术是虚拟现实技术在医学领域的一个重要研究方向．建立颅颌面虚拟手术可通过分析病人的个体手术计划及步骤，降低颅颌面外科手术风险并提高手术精度．虚拟截骨是虚拟手术中的重点及难点，故侧重探索颅颌面虚拟术前规划技术中关键的虚拟截骨，以整形外科手术中的下颌角骨组织切除作为研究内容．以MC算法实现头颅的DICOM格式CT图像三维重建；利用二元树结构定义在重建出的三维头颅模型上分离出下颌升支；再研究虚拟截骨算法并对下颌升支实施虚拟截骨．虚拟截骨结果表明，本研究采用的三维重建算法及截骨算法得到成功应用，该系统具备一定的应用价值．     

Mandibular morphology,task specialization and bite mechanics in Pheidole ants (Hymenoptera: Formicidae)

Ants show remarkable ecological and evolutionary success due to their social life history and division of labour among colony members. In some lineages, the worker force became subdivided into morphologically distinct individuals (i.e. minor versus major workers), allowing for the differential performance of particular roles in the colony. However, the functional and ecological significance of these morphological differences are not well understood. Here, we applied finite element analysis (FEA) to explore the biomechanical differences between major and minor ant worker mandibles. Analyses were carried out on mandibles of two Pheidole species, a dimorphic ant genus. We tested whether major mandibles evolved to minimize stress when compared to minors using combinations of the apical tooth and masticatory margin bites under strike and pressure conditions. Majors performed better in pressure conditions yet, contrary to our expectations, minors performed better in strike bite scenarios. Moreover, we demonstrated that even small morphological differences in ant mandibles might lead to substantial differences in biomechanical responses to bite loading. These results also underscore the potential of FEA to uncover biomechanical consequences of morphological differences within and between ant workers.     

3类面型下颌骨应力分布的数值研究

针对不同下颌骨结构对应力分布的影响问题,基于面型与下颌骨结构的关系,选择3类面型（尖型、方型和圆型）的下颌骨,建立3维有限元模型。比较分析了3类面型下颌骨的位移、应力及肌肉力分布规律和差异。结果发现,不同面型所对应的下颌骨具有一定的构型特征。圆型的前后径距显著低于方型和尖型,但其对位移、应力分布和肌肉力等的影响不显著。方型面型下颌骨的升支高度明显高于圆型和尖型,其位移、应力和肌肉力均显著低于圆型和尖型。说明不同下颌骨结构对应力分布的影响是存在的,但不同的结构差异,其影响是不同的。因此,为了使有限元结果更合理和具有可比性,对临床有更明确的指导作用,深人细致地研究不同构型下颌骨对应力分布的影响规律,建立下颌骨有限元模型的量化标准是非常必要的。     

Severe jaw enlargement associated with uremic hyperparathyroidism

Marked enlargement of the jaws is a rare complication of renal osteodystrophy. This report describes a localized enlargement of the mandible due to a brown tumor in a patient undergoing chronic hemodialysis. Literature on jaw involvement in secondary hyperparathyroidism is reviewed.     

激光全息和散斑干涉法测量新鲜人体下颌骨的弹性性质

本文采用激光全息和散斑干涉法测量了新鲜人体下颌骨皮质骨的弹性性质,实验结果表明:新鲜人体下颌骨皮质骨的力学性质呈各向异性。     

An intelligent dental robot

An intelligent dental robot (IDR) is reported for the purpose of artificial denture verification and test. Methods: The IDR is composed of power system, intelligent control and driving system, sensor system and supporting system. Five Maxon motors are adopted to provide the driving force for the IDR. Novel motor linear actuators are developed to mimic the movement of human’s masticatory muscles. Forward and inverse kinematics of the IDR are analyzed. Seven high-precision pressure sensors are utilized to detect the force on individual artificial tooth. Results: Motion and force experiments are conducted on the IDR. The maximum biting force provided by the IDR is 490?N. Hysteresis rate of the biting force loading and unloading is less than 3%. The largest displacement for the mandible movement test is found to be 60, 9 and 22?mm in the vertical, protrusive and lateral directions, respectively. Conclusion: IDR can complete simulated human masticatory movement and provide sufficient biting force. Significance: The IDR provides clinical guidance for the design and performance test of artificial denture.     

Bone Repair Stimulation in Rat Mandible by New Chitosan Silver(I) Complexes

Two new chitosan silver(I) complexes, [Ag(2CS)(H₂O)(NO₃)] and [Ag(2CS)(ahmp)(H₂O)] (CS = chitosan, Hahmp = 4-amino-6-hydroxy-2-mercaptopyrimidine) were synthesized and characterized on the basis of elemental analysis, spectral (FT-IR and solid-state ¹³C-NMR), morphological (SEM, matrix analysis, XRD, and XRPE), and thermal measurements. Chitosan behaves as a neutral ligand, coordinates Ag(I) through half of amino nitrogen centers, with the pendant glucose amine hydroxy functionality playing no role in coordination, while 4-amino-6-hydroxy-2-mercaptopyrimidine functions as mononegative bidentate, chelating through the deprotonated cyclic nitrogen and thione sulfur atoms. [Ag(2CS)(ahmp)(H₂O)] displays a significant potential bone regenerator in rat mandible. Forty male rats were divided into two groups: bone defect (control) and bone defect with [Ag(2CS)(ahmp)(H₂O)] (treated). The bone defects were stained with hematoxylin and eosin, and Masson's trichrome for histological analysis. The treated group shows faster and well organized bone formation in the defect in comparison to the control group which shows little new bone trabeculae and wide marrow cavities.     

快速成形技术应用于下颌骨缺损二次重建手术指导

下颌骨肿瘤切除术后或下颌骨外伤后,均可造成下颌骨的缺损,从而导致语言和咀嚼功能障碍。游离腓骨瓣修复下颌骨的手术是目前最主流、最先进的下颌骨缺损修复方法,能最大限度恢复下颌骨的外形和功能,同时该手术比较复杂。为提高游离腓骨瓣和下颌骨缺损的匹配程度,采用定制化修复钛板设计和制造方法。通过采集分析病人CT数据,利用可视化和CAD技术设计出符合病人生理结构的修复体模型。利用快速原型技术制造出树脂模型用于手术指导,通过临床研究,该方法可节省手术时间,提高手术成功率。一例利用传统手术方法进行下颌骨缺损修复手术失败的病人,利用快速成型技术辅助成功的进行了二次手术。       

Effects of 4-Hexylresorcinol on Craniofacial Growth in Rats

4-Hexylresorcinol (4HR) has been used as a food additive, however, it has been recently demonstrated as a Class I histone deacetylase inhibitor (HDACi). Unlike other HDACi, 4HR can be taken through foods. Unfortunately, some HDACi have an influence on craniofacial growth, therefore, the purpose of this study was to evaluate the effects of 4HR on craniofacial growth. Saos-2 cells (osteoblast-like cells) were used for the evaluation of HDACi and its associated activities after 4HR administration. For the evaluation of craniofacial growth, 12.8 mg/kg of 4HR was administered weekly to 4 week old rats (male: 10, female: 10) for 12 weeks. Ten rats were used for untreated control (males: 5, females: 5). Body weight was recorded every week. Serum and head samples were collected at 12 weeks after initial administration. Craniofacial growth was evaluated by micro-computerized tomography. Serum was used for ELISA (testosterone and estrogen) and immunoprecipitation high-performance liquid chromatography (IP-HPLC). The administration of 4HR (1–100 μM) showed significant HDACi activity (p < 0.05). Body weight was significantly different in male rats (p < 0.05), and mandibular size was significantly smaller in 4HR-treated male rats with reduced testosterone levels. However, the mandibular size was significantly higher in 4HR treated female rats with increased growth hormone levels. In conclusion, 4HR had HDACi activity in Saos-2 cells. The administration of 4HR on growing rats showed different responses in body weight and mandibular size between sexes.