足头向穿刺路径在膈肌下方肝肿瘤消融治疗中的CT模拟测量研究

【摘要】 目的 对足头向穿刺路径进行模拟测量并评价在膈肌下方肝肿瘤热消融治疗中的临床应用价值。方法 重建患者上腹部CT图像，选取有代表性的3个矢状面和1个冠状面作为标准层面，在各层面建立膈下标准病灶模型，并采用足头向穿刺路径进行模拟穿刺。测量各平面上膈肌高度、穿刺路径长度及间距。采用可到达性评价模拟穿刺时穿刺针分布于标准病灶中的最理想的位置情况。结果 纳入86例患者行测量研究，多数患者矢状2、3面的膈肌高度低于2cm，仅分别对平面内1511%的病灶e和813%的病灶f进行了测量。标准病灶a、b、c、d、b’的完全到达比例分别为5243%、6097%、3837%、5294%、6353%，中位路径长度分别为1039cm、1337cm（背侧，腹侧1266cm）、1315cm、888cm、1126cm，中位穿刺路径间距分别为21cm、209cm（背侧，214cm腹侧）、206cm、211cm、2145cm。结论 采用足头向穿刺路径进行穿刺，标准病灶a、b、d、b’有较高的完全到达比例，穿刺宽容度较高，有进一步在临床中应用的价值。标准病灶c的完全到达率不高。标准病灶e、f需要采用该路径穿刺的比例不高。     

Analysis of the uninjured tibiofibular syndesmosis using conventional CT-imaging and axial force in different foot positions

BackgroundSyndesmosis measurments and indices have been controversial and showed interindividual variability. The purpose of this study was to analyze, by conventional axial computed tomography images and a simulated load device, the uninjured tibiofibular syndesmosis under axial force and forced foot positions.MethodsA total of 15 healthy patients (30 ankles) were studied using adjustable simulated load device (ASLD). This device allowed to perform bilateral ankle CT scans in two forced foot and ankle positions (30° of plantar flexion, 15° of inversion, 20° of internal rotation and 15° of dorsal flexion, 15° of eversion, 30° of external rotation). Axial load was applied simultaneously in a controlled manner (70% body weight). Measurements on the axial image of computed tomography were: syndesmotic area (SA), fibular rotation (FR), position of the fibula in the sagittal plane (FPS), depth of the incisura (ID) and direct anterior difference (ADD), direct middle difference (MDD) and direct posterior difference (PDD).ResultsIn patients without injury to the tibiofibular syndesmosis, the application of axial load and forced foot and ankle positions showed statistically significant differences on the distal tibiofibular measurements between the stressed and the relaxed position, it also showed interindividual variability : SA (median = 4.12 [IQR = 2.42, 6.63]) (p < 0.001), ADD (0.67 [0.14, 0.67]) (p < 0.001), MDD(0.45, [0.05, 0.9]) (p < 0.001), PDD (0.73 [?0.05, 0.73]) (p < 0.002). However, it did not detect statistically significant differences when the tibiofibular differences between the stressed and the relaxed position in one ankle were compared with the contralateral side: SA (?0.14, SD = 4.33 [95% CI = ?2.53, 2.26]), ADD (?0.42, 1.08 [?1.02, 0.18]), MDD (0.29, 0.54 [?0.01, 0.59]), PDD (?0.1, 1.42 [?0.89, 0.68]). Interobserver reliability showed an Intraclass correlation coefficient of 0.990 [95% CI = 0.972, 0.997].ConclusionsWide interindividual variability was observed in all syndesmotic measurements, but no statistically significant differences were found when comparing one ankle to the contralateral side. Measuring syndesmosis alignment parameters, may only be of value, if those are compared to the contralateral ankle.     

Clinical equivalence assessment of T2 synthesized pediatric brain magnetic resonance imaging

Background and purposeAutomated synthetic magnetic resonance imaging (MRI) provides qualitative, weighted image contrasts as well as quantitative information from one scan and is well-suited for various applications such as analysis of white matter disorders. However, the synthesized contrasts have been poorly evaluated in pediatric applications. The purpose of this study was to compare the image quality of synthetic T2 to conventional turbo spin-echo (TSE) T2 in pediatric brain MRI.Materials and methodsThis was a mono-center prospective study. Synthetic and conventional MRI acquisitions at 1.5 Tesla were performed for each patient during the same session using a prototype accelerated T2 mapping sequence package (TA_synthetic = 3:07 min, TA_conventional = 2:33 min). Image sets were blindly and randomly analyzed by pediatric neuroradiologists. Global image quality, morphologic legibility of standard structures and artifacts were assessed using a 4-point Likert scale. Inter-observer kappa agreements were calculated. The capability of the synthesized contrasts and conventional TSE T2 to discern normal and pathologic cases was evaluated.ResultsSixty patients were included. The overall diagnostic quality of the synthesized contrasts was non-inferior to conventional imaging scale (P = 0.06). There was no significant difference in the legibility of normal and pathological anatomic structures of synthetized and conventional TSE T2 (all P > 0.05) as well as for artifacts except for phase encoding (P = 0.008). Inter-observer agreement was good to almost perfect (kappa between 0.66 and 1).ConclusionsT2 synthesized contrasts, which also provides quantitative T2 information that could be useful, could be suggested as an equivalent technique in pediatric neuro-imaging, compared to conventional TSE T2.     

Acoustic emission analysis of the effect of simulated pulpal pressure and cavity type on the tooth–composite interfacial de-bonding

ObjectiveThe aim of this study was to evaluate the influence of in vitro pulpal pressure and cavity type on the tooth–composite bonding interface by means of acoustic emission (AE) analysis.MethodsClasses I and II cavities on extracted third molars were prepared and assigned to four groups of seven teeth each: (1) direct composite restoration without simulated pulpal pressure (SPP) in class I cavity, (2) direct composite restoration with SPP in class I cavity, (3) direct composite restoration without SPP in class II cavity, (4) direct composite restoration with SPP in class II cavity. The teeth were restored with Filtek Z250 composite and Adper Scotchbond Multi-Purpose adhesive system (3M ESPE, St. Paul, MN, USA). AE events were recorded for 2000 s during light-curing. Groups 2 and 4 were subjected to 20 cm H₂O hydrostatic pressure throughout the procedures. The data were analyzed with two-way ANOVA. After the AE test, teeth were sectioned longitudinally in mesio-distal direction, the tooth–composite interface was examined using SEM.ResultsSPP in Groups 2 (4.57 ± 1.40) and 4 (3.43 ± 1.13) yielded significantly higher AE events number than those of Groups 1 (3.43 ± 1.51) and 3 (1.71 ± 0.95) where the SPP was not applied (p < 0.05). The number of AE events of class I cavity in Groups 1 and 2 were significantly higher than those of class II cavity in Groups 3 and 4 (p < 0.05). SEM examination showed that all groups had intact enamel–composite interface, while micro-gaps were observed at the dentin–composite interface, mainly at the pulpal floor of the cavity. The class I cavities with SPP in Group 2 showed wider gaps more frequently than class II cavities without SPP in Group 3.SignificanceThe SPP and class I cavity with high C-factor triggered more AE events, confirming its negative impact on the bonding interface.     

树脂透明牙模型用于根管治疗操作训练的效果评价

目的 评价在根管治疗术的临床前探作训练中树脂透明牙模型的作用和效果。方法 在北大口腔医学专业牙体牙艇病学临床前教学中，选取46名学生用树脂透明牙作为根管治疗术的学具，每人均做上第一磨牙和上中切牙共184个根管，分别按设计模式进行直视探作和盲探作两种练习。问卷调查学生的学习效果。进行统计学分析。结果 ①直视下完成根管预备和充填，学生能够直观地了解根管的形态和分布，对于学生掌握探作器械到达的位置、操作手法的应用，以及操作效果的评价和探作缺陷的认知显示了极大优势。②先做盲预备再用透明牙直视下预备，可令学生加深理解一些关键的探作步骤。结论 树脂透明牙模型用于根管治疗的临床前探作训练具有直观的优点，使操作者更易于掌握根管治疗的探作要领，先盲预备后直视预备可获得更佳的学习效果。     

The influence of simulated masticatory loading regimes on the bi-axial flexure strength and reliability of a Y-TZP dental ceramic

OBJECTIVES: The purpose of the current study was to examine the influence of simulated masticatory loading regimes, to which all-ceramic crown or bridge restorations will routinely be subjected during their service-life, on the performance of a yttria-stabilised tetragonal zirconia polycrystalline (Y-TZP) dental ceramic. METHODS: Ten sets of 30 Y-TZP ceramic discs (13 mm diameter, 1.48-1.54 mm thickness) supplied by the manufacturer were randomly selected. Six groups were loaded for 2000 cycles at 500 N (383-420 MPa), 700N (536-588 MPa) and 800 N (613-672 MPa) with three groups maintained dry and the remaining three groups loaded while immersed in water at 37+/-1 degrees C. A further two groups underwent extended simulated masticatory loading regimes at 80 N (61-67 MPa) for 10(4) and 10(5)cycles under dry conditions. The mean bi-axial flexure strengths, standard deviations and associated Weibull moduli (m) were determined. The surface hardness was also determined using the Vickers hardness indentation technique. RESULTS: No significant difference (P>0.05) was identified in the bi-axial flexure strength of the simulated masticatory loading regimes and the control specimens loaded dry or wet. A significant increase in m was identified for the Y-TZP specimens following loading while immersed in water (8.6+/-1.6, 8.5+/-1.6 and 10.3+/-1.9) compared with the control (7.1+/-1.3). However, the extended loading regime to 10(5)cycles resulted in a significant reduction in the m of the Y-TZP specimens (5.3+/-1.0) compared with the control. Localised areas of increased surface hardness were identified to occur directly beneath the spherical indenter. CONCLUSIONS: The occurrence of localised areas of increased surface hardness could be the result of either a transformation toughening mechanism or crushing and densification of the material beneath the indentor manifested as the formation of a surface layer of compressive stresses that counteracted the tensile field generated at the tip of a propagating crack which increased the Weibull modulus of the Y-TZP specimens. The reduced reliability of the Y-TZP specimens loaded to 80 N for 10(5)cycles was associated with the accumulation of subcritical damage as a result of the extended nature of loading.     

Effect of simulated microgravity on salivary and serum oxidants, antioxidants, and periodontal status

Background: Microgravity is associated with an increase in peroxidative damage. The effect is more pronounced after long‐duration space flights and can even last for several weeks after landing. The objective of the study is to determine the influence of simulated microgravity on the periodontal status and salivary and serum oxidant/antioxidant status of the body in simulated microgravity (?6° head‐down‐tilt [HDT) bed rest). Methods: Twenty healthy male volunteers were studied before and after 60 days of simulated microgravity (?6° HDT bed rest). We measured salivary and serum oxidative markers, such as malondialdehyde (MDA), 8‐oxo‐7,8 dihydro‐2 deoxyguanosine (8‐OHdG), and vitamins C and E, and clinical periodontal parameters (probing depth [PD] and clinical attachment level [CAL]). Results: Serum and salivary vitamin C and E concentrations were significantly decreased, whereas MDA and 8‐OHdG levels were significantly increased after 60 days of simulated microgravity. Serum and salivary markers showed a strong and significant correlation. CAL and PD were higher but not statistically significant in simulated microgravity. Conclusions: This study suggests that oxidative stress in the microgravity environment was increased but did not significantly influence periodontal parameters after 2 months. Also, this study indicates the possibility that the findings may have a broader clinical relevance to patients on bed rest or who are physically inactive. Studies on larger patient samples and follow‐up for a longer time are required to verify the relationship between antioxidant status in the space microgravity condition and periodontal health.     

3D回旋仪模拟微重力效应对小鼠骨骼和 心脏的影响

目的：利用3D 回旋仪模拟微重力效应探究对小鼠骨骼和心脏的影响。方法：25 只8 周龄雄性C57BL/6J 小鼠,随机分成5 组（n=3~5）：地面对照组（GC 组）,3 周处理对照组（TC3 组）,3 周模拟微重力组（SM3 组）,6 周 处理对照组（TC6 组）,6 周模拟微重力组（SM6 组）。使用Micro-CT 检测小鼠左股骨参数变化。采用超声方法检 测小鼠心脏结构和功能的变化。结果：与GC 组相比,TC3 组、SM3 组、TC6 和SM6 组小鼠的骨体积分数,骨小 梁厚度显著降低（P<0.05）,骨小梁间距显著增加（P<0.05）。骨小梁数量和皮质骨壁厚度没有显著性差异。3D 回 旋仪处理3 周后,与小鼠左心室后壁厚度变薄相比,其他参数没有变化。而在第6 周,舒张期和收缩期的左心室 内径变小,左心室质量变轻。结论：3D 回旋仪模拟微重力效应会导致小鼠骨质流失,影响心脏结构和功能,且具 有时间效应。     

微重力引起的骨质丢失研究进展

人类对太空的探索日益频繁,然而太空微重力会引起航天员骨质丢失,对航天员的健康造成损害。因此,有研究者通过航天实验及模拟微重力实验研究微重力下骨质丢失的发生机制及解决措施。微重力会引起成骨细胞和破骨细胞代谢活动改变,并引起机体对钙离子新陈代谢的改变。航天微重力导致的骨质丢失是微重力和太空射线共同作用的结果。本文将对微重力所致骨质丢失的发生机制和治疗对策加以概述。