Annotated normal CT data of the abdomen for deep learning: Challenges and strategies for implementation

PurposeThe purpose of this study was to report procedures developed to annotate abdominal computed tomography (CT) images from subjects without pancreatic disease that will be used as the input for deep convolutional neural networks (DNN) for development of deep learning algorithms for automatic recognition of a normal pancreas.Materials and methodsDual-phase contrast-enhanced volumetric CT acquired from 2005 to 2009 from potential kidney donors were retrospectively assessed. Four trained human annotators manually and sequentially annotated 22 structures in each datasets, then expert radiologists confirmed the annotation. For efficient annotation and data management, a commercial software package that supports three-dimensional segmentation was used.ResultsA total of 1150 dual-phase CT datasets from 575 subjects were annotated. There were 229 men and 346 women (mean age: 45 ± 12 years; range: 18–79 years). The mean intra-observer intra-subject dual-phase CT volume difference of all annotated structures was 4.27 mL (7.65%). The deep network prediction for multi-organ segmentation showed high fidelity with 89.4% and 1.29 mm in terms of mean Dice similarity coefficients and mean surface distances, respectively.ConclusionsA reliable data collection/annotation process for abdominal structures was developed. This process can be used to generate large datasets appropriate for deep learning.     

人工智能对胃肠疾病诊疗的推动作用

高速发展的计算机技术给日常生活及工作带来巨大变化。人工智能是计算机科学的一个分支,是让计算机去行使通常情况下具备智能生命才可能行使的活动,广义的人工智能涵盖机器学习和机器人等等,本文主要聚焦于机器学习与相关的医学领域,深度学习是机器学习中的人工神经网络,卷积神经网络(CNN)是深度神经网络的一种,是在深度神经网络基础上,进一步模仿大脑的视觉皮层构造和视觉活动原理而开发;目前在医疗大数据分析中应用的机器学习方式主要为CNN。在未来数年内,人工智能作为常规工具进入医学图像解读相关的科室是发展趋势。本文主要分享人工智能与生物医学的融合进展,并结合实际案例,重点介绍CNN在胃肠道疾病的病理诊断、影像学诊断及内镜诊断等方面的应用研究现状。     

数字化技术在颅颌面外科中的应用进展与展望

数字化技术的引进极大地推动了颅颌面外科的进步。数字化三维重建、3D模型打印、数字图像模拟手术和手术导板等革新了治疗手段、降低了手术难度、提升了治疗结果的精准性和可预测性,现已成为颅颌面外科常规诊疗手段。相信随着不断完善的动态导航、智能化手术机器人的研发和使用,颅颌面外科将会获得长足的发展。     

机器学习在医学中的应用现状

人工智能在近年来已广泛应用于社会各个领域,取得巨大成就。但公众对人工智能的认知仍存在一定误区,笔者就人工智能的当前定义、主要思想及方法做了简要回顾;对当前主流的人工智能技术——机器学习及不足做简要介绍。介绍当前人工智能在医学领域中的应用。相信随着技术的进步,在可见的未来,人工智能将作为医师的强有力的助手,减轻医师负担,减少误诊、误治,提高医疗救治水平。     

人工颈椎间盘置换联合前路减压融合术治疗多节段颈椎病的临床疗效分析

目的探讨人工颈椎间盘置换联合前路减压融合术治疗多节段颈椎病的临床疗效。方法回顾性分析2009年1月~2013年4月因多节段颈椎病于我院行人工颈椎间盘置换联合前路融合术的18例患者临床资料,男7例,女11例;年龄37~59岁,平均47.1岁;11例患者行人工颈椎间盘置换联合椎间盘切除减压融合术,7例患者行人工颈椎间盘置换联合椎体次全切减压融合术。采用日本整形外科协会评分(Japanese orthopaedic association,JOA)、颈椎功能残障指数(neck disability index,NDI)、疼痛视觉模拟评分(visual analogue scale,VAS)评价临床疗效;行颈椎正侧位、功能位X线片及颈椎CT三维重建扫描,分别测量置换节段、手术相邻节段及颈椎整体活动度,并观察融合节段融合率、内固定位置及异位骨化情况。结果术后随访18~54个月,平均26.3个月,术后各随访点患者JOA、NDI、VAS评分均较术前显著改善(P<0.05);术后24个月时置换节段活动度(8.37°±2.77°)与术前(8.23°±3.36°)相比差异无统计学意义(P>0.05),颈椎整体活动度(41.71°±6.99°)较术前(44.91°±9.48°)显著减小,置换邻近节段活动度(9.16°±2.72°)与术前(9.41°±2.72°)相比差异无统计学意义(P>0.05),融合邻近节段活动度(9.43°±2.6°)较术前(8.18°±2.42°)显著增加(P<0.05);术后12个月融合节段融合率100%,术后各随访点未观察到内植物松动、移位及异位骨化等并发症。结论人工颈椎间盘置换联合前路减压融合术治疗多节段颈椎病可有效缓解疼痛、改善神经功能、维持颈椎生理活动度,获得满意临床疗效。     

Is the side with the best masticatory performance selected for chewing?

ObjectiveThis study assessed the degree of relationship between masticatory laterality and lateral asymmetry of masticatory performance using silicon pieces enclosed in a latex bag.DesignForty-two young adults with natural dentition participated in this cross-sectional, observational study. They performed four different masticatory assays, each consisting of five trials of chewing three pieces of silicon for 20 cycles. In one assay, they were asked to masticate unbagged silicon free-style, whilst in the three other assays they were asked to masticate bagged silicon free-style, unilaterally on the right-hand side and unilaterally on the left-hand side. The preferred chewing side was determined by calculating the asymmetry index for both the free-style assays. Masticatory performance was determined by sieving the silicon particles and the cycle duration was also recorded. Data were analysed using independent samples or paired t-test and linear regression.ResultsMasticatory function using the bagged silicon was similar to that using the unbagged silicon. A significant and positive relationship was observed between the preferred chewing side expressed as the asymmetry index and the side with better masticatory performance. Alternate unilateral chewers demonstrated better masticatory performance than unilateral chewers. However, when free-style and unilateral chewing were compared for each subject, unilateral chewing was found to be as efficient as – or even more efficient than – free-style chewing.ConclusionsThere is a positive association between the preferred chewing side and the more efficient side. Alternate unilateral mastication per se does not promote better masticatory performance than consistently unilateral mastication.     

Simultaneous measurement of polymerization stress and curing kinetics for photo-polymerized composites with high filler contents

ObjectivesPhotopolymerized composites are used in a broad range of applications with their performance largely directed by reaction kinetics and contraction accompanying polymerization. The present study was to demonstrate an instrument capable of simultaneously collecting multiple kinetics parameters for a wide range of photopolymerizable systems: degree of conversion (DC), reaction exotherm, and polymerization stress (PS).MethodsOur system consisted of a cantilever beam-based instrument (tensometer) that has been optimized to capture a large range of stress generated by lightly-filled to highly-filled composites. The sample configuration allows the tensometer to be coupled to a fast near infrared (NIR) spectrometer collecting spectra in transmission mode.ResultsUsing our instrument design, simultaneous measurements of PS and DC are performed, for the first time, on a commercial composite with ≈80% (by mass) silica particle fillers. The in situ NIR spectrometer collects more than 10 spectra per second, allowing for thorough characterization of reaction kinetics. With increased instrument sensitivity coupled with the ability to collect real time reaction kinetics information, we show that the external constraint imposed by the cantilever beam during polymerization could affect the rate of cure and final degree of polymerization.SignificanceThe present simultaneous measurement technique is expected to provide new insights into kinetics and property relationships for photopolymerized composites with high filler content such as dental restorative composites.     

Remineralization potential of fully demineralized dentin infiltrated with silica and hydroxyapatite nanoparticles

Objective

This study investigates the potential of a novel guided tissue regeneration strategy, using fully demineralized dentin infiltrated with silica and hydroxyapatite (HA) nanoparticles (NPs), to remineralize dentin collagen that is completely devoid of native hydroxyapatite.

Methods

Dentin blocks were fully demineralized with 4 N formic acid and subsequently infiltrated with silica and HA NPs. The remineralizing potential of infiltrated dentin was assessed following a twelve week exposure to an artificial saliva solution by means of TEM, EDS and micro-CT. Measurements were taken at baseline and repeated at regular intervals for the duration of the study to quantify the P and Ca levels, the mineral volume percentage and mineral separation of the infiltrated dentin specimens compared to sound dentin and non-infiltrated controls.

Results

Infiltration of demineralized dentin with nano-HA restored up to 55% of the P and Ca levels at baseline. A local increase in the concentration of calcium phosphate compounds over a period of twelve weeks resulted in a higher concentration in P and Ca levels within the infiltrated specimens when compared to the non-infiltrated controls. Remineralization of demineralized dentin with silica NPs by immersion in artificial saliva was the most effective strategy, restoring 20% of the P levels of sound dentin. Micro-CT data showed a 16% recovery of the mineral volume in dentin infiltrated with silica NPs and a significant decrease in the mineral separation to levels comparable to sound dentin.

Significance

Demineralized dentin infiltrated with silica NPs appears to encourage heterogeneous mineralization of the dentin collagen matrix following exposure to an artificial saliva solution.     

Vertical and horizontal polymerization shrinkage in composite restorations

ObjectivePolymerization shrinkage developed in vertical and horizontal directions after light activation of light-curing composite restorative materials. The purpose of this study was to examine the effects of vertical and horizontal polymerization shrinkage on: (a) dimensional changes of resin composites in tooth cavities; (b) shear bond strengths to enamel and dentin; and (c) marginal gap width in a non-reacting Teflon mold.MethodsVertical and horizontal polymerization shrinkage in tooth cavities were measured immediately (3 min) after light activation. With the same time lapse, shear bond strengths to enamel and dentin and marginal gap widths in Teflon mold were also measured.ResultsThere was a significant correlation between vertical and horizontal polymerization shrinkage (r = 0.647, p = 0.043) in the tooth cavity. Composite materials which produced small vertical shrinkage also produced smaller horizontal shrinkage. Composite materials which produced small vertical shrinkage in the tooth cavity exhibited greater shear bond strengths to both enamel (r = −0.697, p = 0.025) and dentin (r = −0.752, p = 0.012). Composite materials which produced smaller horizontal shrinkage produced smaller marginal gap widths in the Teflon mold (r = 0.829, p = 0.003). No relationships were observed between horizontal shrinkage in the tooth cavity and shear bond strengths to both enamel and dentin (p > 0.05).SignificanceDuring the early stage of setting (<3 min) in tooth cavities, the vertical shrinkage of light-activated composite restorative materials was correlated with horizontal shrinkage.