脉冲占空比对磁性微泡介导的聚焦超声温升效应的影响

集合多种诊断和治疗功能的声/磁造影剂微泡的研究与开发已经成为当前医学超声、生物医学工程及临床应用领域共同关注的热点问题.超顺磁氧化铁纳米颗粒具有独特的磁性特征和良好的生物相容性,可被用作核磁共振造影剂来提升影像对比度、空间分辨率及临床诊断准确性.我们的前期工作表明,通过将超顺磁氧化铁纳米颗粒挂载于常规超声造影剂微泡表面,可以成功构建多模态诊断及治疗介质,显著改变超声造影剂微泡的尺度分布及包膜粘弹系数等物理特性,进而影响微泡造影剂的声散射特性及其声空化效应和热效应.然而,此前的研究仅考虑了声场强度和微泡浓度等影响因素,对于脉冲超声时间特性对磁性微泡造影剂动力学响应的影响的相关研究仍有所欠缺.本文通过热电偶对凝胶仿体血管模型中流动的双模态磁性微泡在不同占空比超声脉冲信号作用下,产生温升效应开展了系统的实验测量,并基于有限元模型对实验结果进行了仿真验证.结果显示,脉冲信号占空比的提升是增强血管中磁性微泡在聚焦超声作用下温升效果的关键性时间影响因素.本文的研究成果将有助于更好地理解不同超声作用参数对双模态磁性微泡的热效应的影响机制,对保障双模态磁性微泡在临床热疗应用中的安全性和有效性具有重要的...     

医疗超声中脉冲超声波生物效应的研究

脉冲回波超声波在产科中有很重要的应用,一般认为,使用脉冲超声比较安全,对胎儿没有影响.这种观点的根据在于:(1)通常所用的超声波强度很小,不足以在所照射的生物组织中产生有效的温升;(2)隐含假定:所用的声脉冲很短,不足以产生空化现象. 有人认为,近年来的研究结果表明,有必要注意毫秒量级长度的脉冲超声产生空化的可能性.邱尔特(S·Z·Child)等人的工作表明,低的时间平均强度的脉冲超声可以杀死Drosophila幼虫;生物体对超声波     

空化粉碎结石的试验研究

体外冲击波碎石术已经在临床上取得了成功的应用,但其引起的空化对组织的损伤以及如何合理利用空化来提高碎石效率还有待更细致的研究.本文利用兆赫兹频率级别的聚焦超声换能器诱发冲击波作用于结石模型材料,采用不同的声波参数包括频率、强度、占空比等进行了实验.结果表明,聚焦冲击波对结石的损伤呈凹坑状;空化在凹坑形成初期起到主导作用;采用高低频搭配的脉冲超声波可以实现对结石模型最大的损伤.     

飞秒激光诱导硬质合金YG6表面累积效应

采用波长800nm的飞秒激光对硬质合金YG6表面进行多脉冲加工,利用光学显微镜测量微凹坑损伤形貌及损伤直径,研究了飞秒激光在不同能量密度和脉冲数下硬质合金YG6的损伤阈值和损伤直径的变化规律及其损伤机制.试验结果表明:硬质合金YG6的多脉冲损伤阈值随着脉冲数增加而降低,呈现明显的累积效应.试验得到了多脉冲飞秒激光加工YG6的损伤阈值、损伤直径与脉冲数及中心能量密度的定量关系,YG6多脉冲损伤阈值主要与脉冲数相关,由单脉冲损伤阈值和累积系数共同决定,试验得到YG6单脉冲损伤阈值为1.14±0.06J/cm2,累积系数为0.84±0.02.损伤直径主要与光束中心能量密度和脉冲数相关,由光束束腰半径,单脉冲损伤阈值和累积系数共同决定.试验采用多组平均功率和脉冲数对YG6进行烧蚀,验证了单脉冲损伤阈值和累积系数的可靠性.     

超声作用加速骨折愈合

许多研究表明,低强度的超声辐照对细胞和组织有深远影响,特别在动物和人体骨折的愈合方面。这里报告的是,特定的超声加速了兔子腓骨骨折、人体的科利斯骨折和腔骨骨折的愈合。 试验选用的是175只成熟的雌性新西兰白兔(3.5—5.0kg),用无损的脉冲超声辐照锯开的腓骨。脉冲超声的载频为1.5MHz,它在软组织中衰减较小。为避免引起声空化和使组织发热,对超声幅值和平均功率加以限制。脉冲宽度取200μs、重复作用频率1kHz、输入声强(SATA)25±5mW/cm~2。为造成双侧“C”形腓骨骨折,采用了1mm的季格利(Gigli)锯,以确保骨骼横向接合并稳定愈合线。从切骨手术     

超声空化增强川芎嗪对脑缺血再灌注损伤保护作用机制的研究

川芎的生物活性成分(川芎嗪)已广泛应用于治疗心脑血管疾病。基于谷氨酸诱导PC12细胞损伤建立脑缺血再灌注损伤的细胞模型,探讨超声增强川芎嗪对谷氨酸损伤PC12细胞的保护作用机制。研究结果表明,超声能进一步加强川芎嗪对细胞的保护,其主要作用机制为:(1)抑制氧化应激和细胞凋亡相关的Bcl-2蛋白和Bax蛋白的变化从而达到抗凋亡的效果;(2)降低炎症因子(TNF-α和IL-8)的表达,减轻炎症反应损伤;(3)适当的声压可以增强川芎嗪对谷氨酸损伤PC12细胞的保护作用,但过高的声压会引起细胞损伤,导致细胞凋亡。本文的工作表明超声能够增强川芎嗪对脑缺血再灌注损伤的保护作用,为临床脑缺血再灌注损伤的治疗提供了新治疗策略。      

迈克尔逊干涉在超短脉冲测量中的应用

分析了迈克尔逊干涉仪用于强度自相关测量超短脉冲的原理,设计了非共线结构迈克尔逊干涉仪,并利用二次谐波晶体对超短脉冲的强度自相关过程进行分辨,实现对超短脉冲的测量。     

532nm皮秒脉冲激光对单晶硅的损伤特性研究

随着光电对抗和超短脉冲激光技术的发展,研究超短脉冲激光与单晶硅相互作用具有非常重要的理论和实际意义.为了进一步明确532 nm皮秒脉冲激光对单晶硅的损伤机理,本文开展了532 nm皮秒脉冲激光辐照单晶硅的损伤效应实验研究,测定了损伤阈值,明确了损伤机理,探讨了低通量下的脉冲累积效应.首先,利用波长为532 nm、脉冲宽...     

激光对半导体材料损伤的机理研究

研究了半导体材料对激光的吸收机制。运用一维热传导方程以及载流子耦合扩散方程研究了激光与半导体材料相互作用的热输运、自由载流子输运过程。分析了半导体材料的热学损伤、力学损伤,以及光电探测器的击穿损伤机制。应用数值模拟的方法对Nd:YAG脉冲激光(1.06μm)辐照下感兴趣的半导体材料PbS内部瞬时温度场分布进行了模拟。     

产生于双色脉冲与原子相互作用的光电子的时间相关谱

本文研究了双色激光脉冲与原子相互作用的过程.计算了光电子的时间相关谱.并对光电子的时间相关谱的特性以及脉冲强度对该谱的影响进行了讨论.     

Low-intensity pulsed ultrasound (LIPUS) and cell-to-cell communication in bone marrow stromal cells

Low-intensity pulsed ultrasound (LIPUS) is an established therapy for fracture repair and has been used widely in the clinics, but its underlying mechanism of action remains unclear. The aim of the current research was to determine the effect of LIPUS on gap junctional cell-to-cell intercellular communication in rat bone marrow stromal cells (BMSC) in vitro and to determine whether the ability of BMSCs to communicate by gap junctions would affect their response to LIPUS. Single or daily-multiple LIPUS treatment at 1.5 MHz, 30 mW/cm², for 20 min was applied to BMSC. We demonstrated that BMSC form functional gap junctions and single LIPUS treatment significantly increased the intracellular dye transfer between BMSC. In addition, activated phosphorylation of ERK1/2 and p38 by LIPUS stimulation was diminished when cells were treated with a gap junction inhibitor 18β-glycyrrhetinic acid (18β). We further demonstrated that 18β diminished the significant increase in alkaline phosphatase activity following LIPUS stimulation. These results suggest a potential role of gap junctional cell-to-cell intercellular communication on the effects of LIPUS in BMSC.     

Effects of Physical Agents on Muscle Healing with a Focus on Animal Model Research

Skeletal muscle injury is caused by a variety of events, such as muscle laceration, contusions, or strain. Muscle fibers respond to minor damage with immediate repair mechanisms that reseal the cell membrane. On the other hand, repair of irreversibly damaged fibers is achieved by activation of muscle precursor cells. Muscle repair is not always perfect, especially after severe damage, and can lead to excessive fibroblast proliferation that results in the formation of scar tissue within muscle fibers. Remaining scar tissue can impair joint movement, reduce muscular strength, and inhibit exercise ability; therefore, to restore muscle function, minimizing the extent of injury and promoting muscle regeneration are necessary. Various physical agents, such as cold, thermal, electrical stimulation, and low-intensity pulsed ultrasound therapy, have been reported as treatments for muscle healing. Although approaches based on the muscle regeneration process have been under development, the most efficacious physiological treatment for muscle injury remains unclear. In this review, the influence of these physical agents on muscle injury is described with a focus on research using animal models.     

Readout-segmented echo-planar diffusion-weighted MR at 3.0 T for the evaluation the effect of low-intensity transcranial ultrasound on stroke in a rat model

ObjectiveTo investigate the feasibility of the relative apparent diffusion coefficient (rADC) values based on readout-segmented echo-planar diffusion sequence in evaluation the effects of low-intensity transcranial ultrasound (LIPUS) on ischemic stroke in rat models at different onset times.MethodsSixty Sprague-Dawley rats (weight, 250 ± 10 g) were divided randomly into six groups (n = 10) to establish a permanent model of distal middle cerebral artery occlusion (dMCAO). The rats were stimulated with ultrasound for 10 min in the LIPUS groups at 0.5 h, 1 h, 3 h, 6 h, and 9 h after dMCAO (denoted as the LIPUS group (0.5 h), LIPUS group (1 h), LIPUS group (3 h), LIPUS group (6 h), LIPUS group (9 h), and Control group without ultrasound stimulation). Magnetic resonance imaging was acquired at 0.5 h and 1 h after dMCAO and then at 1-hour intervals until 12 h. The rADC values were then measured and calculated. The pathological results from the rat brains were obtained after the experiment.ResultsWhen LIPUS was applied 0.5 h after dMCAO, the rate of decline of rADC values in the early stages were significantly reduced and the final rADC values were significantly increased. When LIPUS were applied at 1 h, 3 h, and 6 h, the final rADC values only increased slightly and did not prevent early declines. No significant difference of ultrasound stimulation at 9 h was found.ConclusionThe rADC values demonstrated difference at different time points after dMCAO between with and without LIPUS groups.     

Osteocytes exposed to far field of therapeutic ultrasound promotes osteogenic cellular activities in pre-osteoblasts through soluble factors

Low intensity pulsed ultrasound (LIPUS) was reported to accelerate the rate of fracture healing. When LIPUS is applied to fractures transcutaneously, bone tissues at different depths are exposed to different ultrasound fields. Measurement of LIPUS shows pressure variations in near field (nearby transducer); uniform profile was found beyond it (far field). Moreover, we have reported that the therapeutic effect of LIPUS is dependent on the axial distance of ultrasound beam in rat fracture model. However, the mechanisms of how different axial distances of LIPUS influence the mechanotransduction of bone cells are not understood. To understand the cellular mechanisms underlying far field LIPUS on enhanced fracture healing in rat model, the present study investigated the effect of ultrasound axial distances on (1) osteocyte, the mechanosensor, and (2) mechanotransduction between osteocyte and pre-osteoblast (bone-forming cell) through paracrine signaling. We hypothesized that far field LIPUS could enhance the osteogenic activities of osteoblasts via paracrine factors secreted from osteocytes. The objective of this study was to investigate the effect of axial distances of LIPUS on osteocytes and osteocyte–osteoblast mechanotransduction. In this study, LIPUS (plane; 2.2 cm in diameter, 1.5 MHz sine wave, I_SATA = 30 mW/cm²) was applied to osteocytes (mechanosensor) at three axial distances: 0 mm (near field), 60 mm (mid-near field) and 130 mm (far field). The conditioned medium of osteocytes (OCM) collected from these three groups were used to culture pre-osteoblasts (effector cell). In this study, (1) the direct effect of ultrasound fields on the mechanosensitivity of osteocytes; and (2) the osteogenic effect of different OCM treatments on pre-osteoblasts were assessed. The immunostaining results indicated the ultrasound beam at far field resulted in more β-catenin nuclear translocation in osteocytes than all other groups. This indicated that osteocytes could detect the acoustic differences of LIPUS at various axial distances. Furthermore, we found that the soluble factors secreted by far field LIPUS exposed osteocytes could further promote pre-osteoblasts cell migration, maturation (transition of cell proliferation into osteogenic differentiation), and matrix calcification. In summary, our results of this present study indicated that axial distance beyond near field could transmit ultrasound energy to osteocyte more efficiently. The LIPUS exposed osteocytes conveyed mechanical signals to pre-osteoblasts and regulated their osteogenic cellular activities via paracrine factors secretion. The soluble factors secreted by far field exposed osteocytes led to promotion in migration and maturation in pre-osteoblasts. This finding demonstrated the positive effects of far field LIPUS on stimulating osteocytes and promoting mechanotransduction between osteocytes and osteoblasts.     

超声增强藻酸钙凝胶支架材料孔隙率的研究

藻酸钙凝胶具有三维立体多孔结构, 能为细胞生长提供充分的附着空间, 且具有良好的生物相容性和一定的机械强度, 是一种理想的细胞支架材料. 本文研究了藻酸钙三维支架材料的力学特性与氯化钙/藻酸钠的配比的关系, 并提出采用低强度脉冲超声处理藻酸钙凝胶、基于超声空化效应增强藻酸钙凝胶孔隙率的新方法. 实验采用交联合成方法制备藻酸钙凝胶支架材料, 测量力学特性、孔洞的联通性与孔隙率, 并利用绿色荧光蛋白的表达评价细胞的增殖能力. 结果表明, 当氯化钙/藻酸钠的配比为3:5时, 凝胶的机械强度和弹性较好, 力学性能稳定, 为最佳配比参数. 采用声压0.055 MPa的脉冲超声作用20 min, 可以有效提高凝胶支架的孔隙率; 且细胞在该支架中生长状态良好, 呈现团簇状生长趋势.     

Investigation of rat bone fracture healing using pulsed 1.5 MHz, 30 mW/cm burst ultrasound – Axial distance dependency

This study investigated the effect of LIPUS on fracture healing when fractures were exposed to ultrasound at three axial distances: z = 0 mm, 60 mm, and 130 mm. We applied LIPUS to rat fracture at these three axial distances mimicking the exposure condition of human fractures at different depths under the soft tissue. Measurement of LIPUS shows pressure variations in near field (nearby transducer); uniform profile was found beyond it (far field). We asked whether different positions of the fracture within the ultrasound field cause inconsistent biological effect during the healing process. Closed femoral fractured Sprague–Dawley rats were randomized into control, near-field (0 mm), mid-near field (60 mm) or far-field (130 mm) groups. Daily LIPUS treatment (plane, but apodized source, see details in the text; 2.2 cm in diameter; 1.5 MHz sine waves repeating at 1 kHz PRF; spatial average temporal average intensity, I_SATA = 30 mW/cm²) was given to fracture site at the three axial distances. Weekly radiographs and endpoint microCT, histomorphometry, and mechanical tests were performed. The results showed that the 130 mm group had the highest tissue mineral density; and significantly higher mechanical properties than control at week 4. The 60 mm and 0 mm groups had significantly higher (i.e. p < 0.05) woven bone percentage than control group in radiological, microCT and histomorphometry measurements. In general, LIPUS at far field augmented callus mineralization and mechanical properties; while near field and mid-near field enhanced woven bone formation. Our results indicated the therapeutic effect of LIPUS is dependent on the axial distance of the ultrasound beam. Therefore, the depth of fracture under the soft tissue affects the biological effect of LIPUS. Clinicians have to be aware of the fracture depth when LIPUS is applied transcutaneously.     

Influence of low-intensity pulsed ultrasound on osteogenic tissue regeneration in a periodontal injury model: X-ray image alterations assessed by micro-computed tomography

Objective

This study was conducted to evaluate, with micro-computed tomography, the influence of low-intensity pulsed ultrasound on wound-healing in periodontal tissues.

Methods

Periodontal disease with Class II furcation involvement was surgically produced at the bilateral mandibular premolars in 8 adult male beagle dogs. Twenty-four teeth were randomly assigned among 4 groups (G): G1, periodontal flap surgery; G2, periodontal flap surgery + low-intensity pulsed ultrasound (LIPUS); G3, guided tissue regeneration (GTR) surgery; G4, GTR surgery plus LIPUS. The affected area in the experimental group was exposed to LIPUS. At 6 and 8 weeks, the X-ray images of regenerated teeth were referred to micro-CT scanning for 3-D measurement.

Results

Bone volume (BV), bone surface (BS), and number of trabeculae (Tb) in G2 and G4 were higher than in G1 and G3 (p < 0.05). BV, BS, and Tb.N of the GTR + LIPUS group were higher than in the GTR group. BV, BS, and Tb.N of the LIPUS group were higher than in the periodontal flap surgery group.

Conclusion

LIPUS irradiation increased the number, volume, and area of new alveolar bone trabeculae. LIPUS has the potential to promote the repair of periodontal tissue, and may work effectively if combined with GTR.     

Osteogenic differentiation of rat bone marrow stromal cells by various intensities of low-intensity pulsed ultrasound

Bone growth and repair are under the control of biochemical and mechanical signals. Low-intensity pulsed ultrasound (LIPUS) stimulation at 30 mW/cm² is an established, widely used and FDA approved intervention for accelerating bone healing in fractures and non-unions. Although this LIPUS signal accelerates mineralization and bone regeneration, the actual intensity experienced by the cells at the target site might be lower, due to the possible attenuation caused by the overlying soft tissue. The aim of this study was to investigate whether LIPUS intensities below 30 mW/cm² are able to provoke phenotypic responses in bone cells. Rat bone marrow stromal cells were cultured under defined conditions and the effect of 2, 15, 30 mW/cm² and sham treatments were studied at early (cell activation), middle (differentiation into osteogenic cells) and late (biological mineralization) stages of osteogenic differentiation. We observed that not only 30 mW/cm² but also 2 and 15 mW/cm², modulated ERK1/2 and p38 intracellular signaling pathways as compared to the sham treatment. After 5 days with daily treatments of 2, 15 and 30 mW/cm², alkaline phosphatase activity, an early indicator of osteoblast differentiation, increased by 79%, 147% and 209%, respectively, compared to sham, indicating that various intensities of LIPUS were able to initiate osteogenic differentiation. While all LIPUS treatments showed higher mineralization, interestingly, the highest increase of 225% was observed in cells treated with 2 mW/cm². As the intensity increased to 15 and 30 mW/cm², the increase in the level of mineralization dropped to 120% and 82%. Our data show that LIPUS intensities lower than the current clinical standard have a positive effect on osteogenic differentiation of rat bone marrow stromal cells. Although Exogen™ at 30 mW/cm² continues to be effective and should be used as a clinical therapy for fracture healing, if confirmed in vivo, the increased mineralization at lower intensities might be the first step towards redefining the most effective LIPUS intensity for clinical use.     

低强度脉冲超声激发的声微流增强藻酸钙凝胶支架材料的孔隙率和通透性研究

低强度脉冲超声(LIPUS)激发的声微流场所产生的剪切应力可作用于细胞膜表面,从而显著增强细胞膜的通透性。构建了三维藻酸钙凝胶支架培养系统,来模拟有利于细胞生长的营养供给和新陈代谢体内微环境;基于扫描电子显微镜、体内荧光图像和激光共聚焦图像观测技术,对LIPUS增强三维藻酸钙凝胶支架材料的孔隙率和通透性的作用机制和参数相关性进行了系统的研究。结果表明,三维藻酸钙凝胶支架材料的孔隙率和通透性可随着LIPUS的驱动声压的升高而显著增强。此外,通过对三维支架材料内的细胞增殖情况分析,发现在适当的LIPUS驱动声压(如P-=0.055 MPa)下,HeLa细胞在LIPUS作用下的三维藻酸钙凝胶支架材料中可获得更高的增殖率。      

基于多疲劳信息融合的车载疲劳检测系统的研究和实现

疲劳驾驶是目前道路交通的一个重要安全隐患,对车载疲劳驾驶系统的研发具有重要的应用价值和广阔的市场前景。目前存在的疲劳监测系统普遍存在成本高,可靠性不足,使用不够便捷等缺陷。通过在安卓平台上采用计算机视觉的途径进行开发和实现,将大大降低系统的成本和使用复杂度。通过多种疲劳特征融合的方法对疲劳状态进行综合性判断,可以有效的增加系统的准确性和可靠性。采用优化的二叉树支持向量机多分类算法能够使得特征融合的过程具有准确性和速度上的优势。在对该疲劳检测系统的相应测试中也获取了良好的实验结果。