凹球面聚焦超声换能器用于热疗时在人体内引起的瞬态温度场

本文引入了虚拟热源的概念,分析了边界条件对升温的影响及加热时间及温度场点位置的关系,详细研究了声源参数及生物组织特性参数对治疗区升温快慢的影响,比较了聚焦参数相同的册球面换在和高斯换能器声焦点的瞬态温度,所得结果对超声热疗的实施具有指导作用。     

用X刀治疗颅内肿瘤

本文介绍了一种新的立体定向放射外科设备X刀，主要介绍它的工作原理、系统数据的测量、治疗过程和临床应用。     

高强度聚焦超声在医学领域中应用的新进展

本文综述了国内外在高强度聚焦超声（high intensity focused ultrasound，HIFU）技术方面研究与应用的新进展。介绍了HIFU的治疗功能原理，特别给出了焦斑半径的具体计算公式和对相关组织的热效应、空化效应、机械效应，辐照效应等损伤机理，重点研究了热效应随声波频率及声强变化的规律。给出了HIFU的一般试验模型即分层组织模型以及HIFU应用与临床的情况。重点研究了HIFU源，主要讨论了换能器的聚焦方式（1）球面自聚焦换能器，（2）声透镜聚焦换能器，（3）大功率多元超声换能器，（4）电子扫描或相控阵列聚焦换能器，以及频率选择与目标深度和辐照强度的关系，并指出与其匹配的几类聚焦换能器的优缺点，列举了HIFU技术在泌尿科、肿瘤学、神经外科、眼科、妇科、止血以及其他医学领域中的最新应用。最后评价了目前HIFU在治疗方面的优势与某些不足以及可能改进的有效措施．展望了HIFU技术广阔的应用前景．     

HIFU热疗生物学焦域温场的研究及其现状(综述)

高强度聚焦超声(high intensity focused ultrasound,HIFU)热疗是利用超声的易聚焦性、生物体内穿透性强等物理特性,将超声波发生器发射出的低能量超声波聚焦于人体内肿瘤组织处,在焦点处产生的瞬态高温效应(>65℃)、空化效应、机械效应和声化学效应的作用下,使靶区肿瘤组织凝固性坏死的肿瘤治疗方法。由于这种治疗方法具有非创伤性、不易引起癌细胞转移、病人痛苦小、治疗后康复快等优点而被应用于临床。现在,HIFU热疗研究也是众多研究者关注的热点。     

X刀的研究与应用

Ｘ刀集计算机立体定向技术和近代放射外科技术在于一体，是继γ刀之后兴起的又一种最先进的立体定向放射外科仪器，它与γ刀相比，具有安全，灵活，高效，低成本，适应范围大，易维护等优点，它对脑血管疾病，颅内肿瘤以及功能性神经外科疾病等具有独特的治疗作用，目前已投入临床应用，本文回顾了Ｘ刀的研究历史，介绍了Ｘ刀的原理结构，性能特点，应用范围，治疗过程，临床疗效和发展现状与未来，客观地评价了Ｘ刀的优缺点和发生几     

γ刀、X刀的发展趋势

1引言 立体定向放射外科(stereotactic radiosugery,SRS)或称立体定向放射治疗(stereotactic radiotherapy,SRT),是一门新的医疗技术.它应用CT、MRI、DSA、PET等影像立体定位和扫描技术,把患者多层序列图像、光盘、磁带等直接数字化图像信息进行传输,经A/D转换器,进入计算机图像处理系统,作虚拟人体3D快速图像重建和高精度立体可视化显示(3D volume rendering,visualization),精确确定病灶空间坐标,并采用数学物理--剂量优化模式和生物学优化模式,优化设计医用高能X(γ)线束,非共面多弧或多个固定野(bcam)立体聚焦照射计划,评估优化其空间剂量分布,确保将大剂量X(γ)射线,单次或分次限制性地适形照射到所设定的头颈、体部靶区病灶上,使该靶区体积内无论良性或恶性的病灶都受到了足够剂量的照射或不可逆损毁,同时又能保证靶体积边缘之外所接受的放射线剂量呈锐减性分布,从而达到治疗肿瘤而对靶体积周围的正常组织影响很小的目的.照射时,由于靶区外组织因剂量迅速递减而免受累及,从而在其边缘形成一如刀割样的界面,达到类似外科手术的效果.用γ射线时称为γ刀,用X射线时称为X刀;但它并不是将病变切除,而是用放射线杀死肿瘤细胞.[1,2]     

高强度聚焦超声热疗技术的发展和应用

高强度聚焦超声热疗技术以其微创、精确度高、副作用小且并发症少而被应用于临床治疗。目前,该技术主要用于前列腺癌、肝癌、原发性恶性骨肉瘤及乳腺癌等疾病的治疗。主要论述高强度聚焦超声热疗的现状、临床应用及进展。     

大型医疗设备LEKSELL伽玛刀治疗过程简介

大型医疗设备ＬＥＫＳＥＬＬ伽玛刀治疗过程简介解放军第１５０中心医院周前早ＬＥＫＳＥＬＬ伽玛刀（即γ刀）是世界上最先进的大型高科技治疗设备，它开创了立体定向神经外科的先河，给部分患颅内良性、恶性、转移瘤、脑血管畸形及功能性神经外科疾病等患者带来了福音。...     

任意三角形和六边形超声阵元及其高填充率阵列的声场仿真研究

为提高超声设备中二维相控阵列聚焦换能器的面积填充率,提升聚焦区域的超声能量和治疗效率,本研究利用空间脉冲响应理论对任意三角形阵元进行声场计算,通过对三角形阵元进行二维平面旋转完成了六边形阵元声场仿真,并通过对六边形阵元进行三维空间旋转实现了球面阵列聚焦换能器声场仿真。仿真结果显示,六边形7阵元球面填充率提高了6.1%,其-6 dB焦域横向宽度为2.0 mm、纵向长度为30.1 mm; 19阵元球面填充率提高了5.5%,其-6 dB焦域横向宽度为1.2 mm、纵向长度为9.8 mm,可实现高精度超声治疗。本研究可为任意三角形和六边形及不规则形状阵元声场仿真提供新方法,且为高填充率的球面聚焦超声换能器设计提供新思路。     

纳米微粒磁性靶向热疗作用的应用研究(文献综述)

1 热疗及磁性靶向热疗的概念 将肿瘤部位加热到41℃以上治疗恶性肿瘤的方法称热疗（Hyperthermia）。高温治疗肿瘤由来已久,很早就被认为是有效的疗法。近30年来,随着高温设备的不断更新,加热技术、测温技术的不断发展,高温疗法已成为肿瘤治疗的重要手段之一。目前常用的热疗方法如射频、微波、激光、聚焦超声、全身热疗、隔离灌注等,因对肿瘤的靶向能力差,易导致周围组织的温度升高,具有一定的创伤性,其临床应用范围有限。近年来,随着纳米技术的研究进展,在纳米水平上研制纳米磁性微粒作为药物载体又引起了人们的广泛兴趣,磁性微粒不仅可以用作药物载体,而且在交变磁场下还可发热升温,引起了人们对其在肿瘤热疗方面的潜在价值的重视。     

Ellipsoidal electrogastrographic forward modelling

The theoretical and computational study of the electromagnetic forward and inverse problems in ellipsoidal geometry is important in electrogastrography because the geometry of the human stomach can be well approximated using this idealized body. Moreover, the anisotropies inherent to this organ can be highlighted by the characteristics of the electric potential associated with current dipoles in an ellipsoid. In this paper, we present a forward simulation for the stomach using an analytic expression of the gastric electric potential that employs a truncated expansion of ellipsoidal harmonics; we then demonstrate that an activation front of dipoles propagating along the body of an ellipsoid can simulate gastric electrical activity. In addition to the usefulness of our model, we also discuss its limitations and accuracy.     

Four-shell ellipsoidal model employing multipole expansion in ellipsoidal coordinates

Although the head is more closely represented as an ellipsoid than a sphere, calculation in ellipsoidal coordinates is difficult. This paper presents a four shell ellipsoidal model, employing multipole expansion in ellipsoidal coordinates, for EEG, MEG, and evoked potential applications. Computational detail and insight into efficient calculation of the Lamé functions of the first and second kind are provided to demonstrate feasibilty. The Lamé function of the second kind, derived from the Lamé function of the first kind, can be computed at higher degrees by means of partial fraction expansion.     

磁共振扩散张量成像扩散椭球面积的简化计算方法

目的:提出一种可以精确计算磁共振扩散张量成像扩散椭球表面积的方法。方法:根据理想扩散椭球是旋转椭球及扩散张量矩阵均正定,可将三轴椭球校正为旋转椭球,进而由A.M.Legendre公式推出计算扩散椭球表面积的简化公式。分别利用A.M.Legendre、Knud Thomsen及本文提出的方法计算四种扩散椭球的表面积以评价本文方法的可行性。结果:对于旋转椭球,本文所提方法的计算结果与A.M.Legendre方法的结果一致。结论:本文所提方法计算量较小,可以精确地计算扩散椭球表面积。     

A language for generating tomographic images of mathematical phantoms

A computer language is presented that can be used to generate image files, as if the images are created with a CT or a MR scanner. The language defines objects in the "scanner's" coordinate system, as sets of quadratic inequalities. Each of these objects, e.g., an ellipsoid or a half-plane or a cylinder, has its own density. Objects can be superimposed and collections of objects are allowed to translate and rotate. The language allows for a concise way of describing complex objects with precisely defined geometries and densities. An implementation of the language can be used for testing, developing, and analyzing diagnostic software, treatment planning systems, etc. A software module that is based on the language can be made available. The utility of the module for acceptance testing of radiation therapy treatment planning systems is described.     

Splenic white pulp and associated vascular channels in chicken spleen

We have studied the chicken spleen by light and transmission electron microscopy. Germinal centers are located at the beginning of the central artery which is surrounded by the periarterial lymphatic sheath (PALS). The central artery has no branch crossing the PALS, and there is no histologically identifiable marginal zone in the chicken spleen. The central artery continues as penicilliform capillaries. The mid-portion of the penicilliform capillary is surrounded by the ellipsoid or Schweigger-Seidel sheath. The endothelial lining of this part of the pencilliform capillary contains small channels, formed between neighboring endothelial cells, which enter the ellipsoid. These channels allow circulating substances to accumulate in the ellipsoid. The cells of the ellipsoid are reticular cells, round or ovoid in shape, exhibiting a limited number of cell junctions. At the surface of the ellipsoid are ellipsoid-associated cells (EAC) which have an affinity for toluidine blue. After perfusion fixation, the majority of the cells in the ellipsoid are lost; this suggests weak cellular connections between the ellipsoid cells. The ellipsoid-associated cells remain in loco. On the basis of their shape and cytological features, two stages of EACs can be distinguished. The round or ovoid EACs elaborate active Golgi zones surrounded by numerous small vesicles containing an electron-dense substance. Occasionally, mitotic figures can be seen among them which may suggest that they are immature forms. In the second or more mature stage, the EACs assume an elongated spindle shape. The spindle-shaped EACs reveal inactive Golgi cis-ternae and fewer but larger granules than the round or immature EACs. Unmyelinated nerve fibers and nerve ending were observed in the ellipsoid. Perfusion fixation reveals that the distal portions of the penicilliform capillaries extend into the red pulp and become the sinuses. Therefore, the circulation of the chicken spleen is anatomically closed except for the channels in the mid-portion of the penicilliform capillary. The periellipsoid white pulp (PWP) possesses a few small lymphocytes, macrophages, and plasma cells with the majority of cells being young blastlike cells which may replenish the EACs and ellipsoidal cells. Carbon, injected intravenously, appears on the EAC membrane by 30 minutes, while Brucella abortus is completely phagocytized at this time. Binding the carbon triggers the EAC to detach from the ellipsoid and migrate to the periellipsoidal white pulp (PWP). The EACs phagocytize carbon by 2 hours, and by 5 and 8 days are present in the red pulp and surround the germinal centers at the border of the periarterial lymphatic sheath, respectively. Secretory cells which have been identified in germinal centers might originate from EACs.     

Power quality issues and the effects on medical equipment

Power quality issues are becoming more important as more medical equipment utilizes microprocessor controls and switched DC power supplies. Externally and internally induced power surges and harmonics can have a dramatic effect on equipment performance. The effectiveness of a good "Equipment Management Program" can be greatly affected by poor power quality in today's hospitals. With many hospitals having been constructed in the 1970's, there is an increased likelihood that this issue will play a part in equipment downtime, and more importantly in "unable to duplicate" findings by the Clinical Engineering staff. Resolving power quality problems can have a dramatic impact on equipment performance, uptime, and cost of maintenance. This presentation will focus on identifying power quality problems, solutions, and an overall management scheme to minimize the impact on the performance of critical equipment that your facility and staff rely on to deliver cost effective patient care.     

Measuring stem cell dimensionality in tissue scaffolds

Many scaffold systems have evolved for tissue engineering and in vitro tissue models to provide a 3D (three-dimensional) microenvironment that enables cells to behave more physiologically. We hypothesized that cells would adopt morphologies with more 3D character during culture in scaffolds as compared to planar substrates. Cell shape and function are tightly linked and effects of scaffold niche properties on cell shape and dimensionality are important for directing cell function. Herein, primary human bone marrow stromal cells (hBMSCs) were cultured in 6 different scaffolds and on a planar control substrate. hBMSCs were imaged using 3D confocal microscopy, and 3D image analyses were used to assess hBMSC shape and dimensionality. A characteristic gyration tensor ellipsoid was calculated for hBMSCs in the different scaffolds which enabled hBMSC dimensionality to be classified based on shape. A “Dimensionality Matrix” was developed that showed that hBMSC shape and dimensionality were influenced by scaffold properties, and that scaffolds could drive hBMSCs into 1D, 2D or 3D shapes. In addition, the hBMSC Z-Depth was measured to determine if hBMSCs became less flat during culture in scaffolds. Z-Depth results showed that all 6 scaffolds caused an increase in cell Z-Depth compared to the 2D planar substrate. These results demonstrate that hBMSCs take on morphologies with greater 3D character in scaffolds than on a planar substrate and that scaffold properties can be adjusted to modify cell dimensionality. In addition, biomaterialists can use this measurement approach to assess and compare scaffold design modifications as they strive to create optimal cell niches that provide a 3D microenvironment.     

Effects of point configuration on the accuracy in 3D reconstruction from biplane images

Two or more angiograms are being used frequently in medical imaging to reconstruct locations in three-dimensional (3D) space, e.g., for reconstruction of 3D vascular trees, implanted electrodes, or patient positioning. A number of techniques have been proposed for this task. In this simulation study, we investigate the effect of the shape of the configuration of the points in 3D (the "cloud" of points) on reconstruction errors for one of these techniques developed in our laboratory. Five types of configurations (a ball, an elongated ellipsoid (cigar), flattened ball (pancake), flattened cigar, and a flattened ball with a single distant point) are used in the evaluations. For each shape, 100 random configurations were generated, with point coordinates chosen from Gaussian distributions having a covariance matrix corresponding to the desired shape. The 3D data were projected into the image planes using a known imaging geometry. Gaussian distributed errors were introduced in the x and y coordinates of these projected points. Gaussian distributed errors were also introduced into the gantry information used to calculate the initial imaging geometry. The imaging geometries and 3D positions were iteratively refined using the enhanced-Metz-Fencil technique. The image data were also used to evaluate the feasible R-t solution volume. The 3D errors between the calculated and true positions were determined. The effects of the shape of the configuration, the number of points, the initial geometry error, and the input image error were evaluated. The results for the number of points, initial geometry error, and image error are in agreement with previously reported results, i.e., increasing the number of points and reducing initial geometry and/or image error, improves the accuracy of the reconstructed data. The shape of the 3D configuration of points also affects the error of reconstructed 3D configuration; specifically, errors decrease as the "volume" of the 3D configuration increases, as would be intuitively expected, and shapes with larger spread, such as spherical shapes, yield more accurate reconstructions. These results are in agreement with an analysis of the solution volume of feasible geometries and could be used to guide selection of points for reconstruction of 3D configurations from two views.