三维分析仪与两维矩阵射野测量的比较

目的:应用不同仪器与方法测量加速器6 MV X线射野的特性,比较各方法的优劣和局限性,探讨快速简便检测射野特性的方法。材料与方法:分别采用电离室和半导体探头配合三维射野分析仪测量加速器6 MV X线不同射野大小的百分深度剂量曲线PDD和离轴比曲线OCR,并以二维电离室矩阵测量相同条件的OCR。(1)比较采用电离室和半导体探头测量PDD的差别。(2)比较两维矩阵与电离室半导体探头测量射野的对称性、平坦度、射野大小和半影等的差别。结果:对小于15 cm×15 cm照射野,半导体探头和电离室测量PDD的结果一致性较好,两者偏差小于1.3%。对于20 cm×20 cm照射野,半导体探头的测量结果大于电离室,最大差别3.5%,偏差为2.6%。用半导体探头与电离室测量射野的大小,两者的最大差别为0.6 mm,两者有较好的一致性,二维电离室矩阵测量与前两者比较,最大差别为2.9 mm,最小差别0.5 mm。三种方法测量的射野平坦度差别在1.2%~2.6%,矩阵的测量数值在半导体和电离室测量范围之内。结论:在检测加速器射野性能时,二维矩阵可以快速检测射野平坦度、对称性,但测量射野大小时可能有较大误差,不宜用作验收加速器和收集...     

X线射野内有效焦点的方位特性研究

近年来使用的 X 线管靶面倾角较小,因此其照射量分布曲线与历史上用作实验的 X线管也不尽相同。本文对小倾角靶面 X 线管的照射量进行测试并给出照射量曲线。指出靶面不同的 X 线管其照射量曲线也不相同,特别是阳极跟端的截止点各不相同,此点在临床使用时应予以注意。     

最佳适形野边距的决定因素和求取方法

目的：探讨最佳适形野边距(block aperture margin，BAM)的决定因素和求取方法。方法：采用三维治疗计划系统(three-dimensional treatment planning system,3-D TPS)，测算出头部和胸部常用放疗条件下“建议射野边距”(P90／50)；根据“建议射野边距”，计算出采用不同BAM时，6MeV X线三野照射头部靶区的剂量分布及15MeV X线四野照射胸部靶区的剂量分布。确定其中符合临床剂量要求，治疗体积在大小和形状上与计划靶区适形程度最好者所采用的BAM为最佳BAM。结果：头部靶区6MeV X线三野照射的最佳BAM为5-7mm，胸部靶区15MeV X线四野照射的最佳BAM为7-10mm。结论：最佳BAM的决定因素复杂，最终求取需三维剂量分布计算。     

模拟调强放疗照射离体细胞的质量保证

目的：在模拟调强放疗方式照射细胞的过程中，保证细胞按调强方式被照射，照射剂量准确。方法：在细胞培养瓶中装满细胞培养液，水平固定在标准水箱（30cm×30cm×30cm）电离室横梁上，在水箱中加水到电离室上方5cm，用CT机（philips brilliance bigbor CT）扫描获取图像，传到计划系统（ECLIPSE 7．0）中；再用一个空的培养瓶替换装满培养液的培养瓶，重新用CT机扫描，获取图像，传到计划系统中。采用先设野中野后合并野中野的设计方法，设计模拟调强照射计划，设定电离室处的吸收剂量400cGy。再把此水箱放到加速器（Varian 600-C／D）下，按设计的模拟调强照射计划进行照射，同时用电离室（NE 0．6cc）剂量仪（NE FARMER 2570）测量得到实际吸收剂量。结果：在细胞培养瓶中装满细胞培养液时模拟调强照射实测得到397cGy，与理论值相差-0．8％；在细胞培养瓶中不装细胞培养液时模拟调强照射实测得到395cGy，与理论值相差-1.3％。结论：用CT模拟定位，用计划系统通过设野中野的方法设计模拟调强照射计划是可行的，可以实现模拟调强照射离体细胞，理论剂量与实测剂量相差小于2％。     

^192Ir源两种刻度方法的比较

目的：通过对＾１９２Ｉｒ源的再次刻度，校准源活度的精确值。材料与方法：用电离室法，分别测量源在水介质中和自由空气中的照射量率。结果：两种方法在刻度＾１９２Ｉｒ源活性上得到的结果是一致的。结论：利用空气比释动能活可以对＾１９２Ｉｒ源进行精确刻度。     

半导体和电离室探头在直线加速器数据测量中的比较与分析

目的：比较分析半导体探头和电离室探头在三维水箱测量中的差异，为能够提高数据测量精度从而实现治疗计划系统建立准确的计算模型提供依据：方法：在加速器8MV光子线下，使用0．13cm^3的指形电离室和半导体探头在三维水箱中分别测量照射野1cm×lcm，2cm×2cm，3cm×3cm，4cm×4cm，5cm×5cm，6cm×6cm，8cm×8cm，10cm×l0cm的总散射因子、百分深度剂量曲线、离轴比曲线，对测量结果进行比较和分析；结果：对于总散射因子，在较大照射野测量时结果一致，在小野测量时存在差异，1cm×lcm照射野的两者测量结果偏差15．32％；对于百分深度曲线，在建成区差异最大，各照射野的在水面处的测量结果均偏差10％以上：对于离轴比曲线，在半影区存在显著差异．半导体探头在最大剂量点深度测量的射野大小均小明显小于电离室测量的结果。结论：总散射因子，小照射野测量时建议使用半导体探头或者较小体积的电离室；百分深度剂量曲线，建议使用电离室探头；离轴比曲线，使用半导体探头可测量到较好的射野半影区。     

用蒙特卡洛方法模拟和评价电离室矩阵探测器的定位灵敏度

目的:由于阵列式平板探测器内每个电离室单元探测器结构和尺寸的差异,构成了不同厂家生产的探测器阵列在放射治疗质量控制中的地位,各自的优势和不足。本文通过Monte Carlo(MC)模拟对不同面积的准直器遮挡入射束所形成的剂量场分布,并和实验测量的结果进行比较,用于评价不同厂家生产的方形探测器电离室矩阵与圆形探测器阵列的对照射野定义的位置灵敏度。方法:用BEAMnrc软件对电子直线加速器机头建模并模拟6 MV X射线的注量场分布,得到PHASE SPACE(相空间)文件,用DOSXYZnrc计算水模体中探测器的剂量分布范围与实际被照射面积的对应关系,从而评价PTW公司的SEVEN29电离室矩阵(方形探测器)与IBA公司的MatriXX电离室矩阵(圆形探测器)对位置的探测敏感度。结果和结论:PTW公司的SEVEN29和IBA公司的MatriXX两种阵列中单个探测器的定位灵敏度在2%的误差范围内基本一致,在放射治疗中凡是涉及对位置的精度检测的操作过程中,这两种电离室矩阵都可以任意选用,其位置的空间定位精度在1 mm以下。     

大剂量X射线照射后淋巴滤泡的形成

目的：观察用500rad X线全身照射后小鼠胭窝淋巴结淋巴滤泡的形成。方法：本实验用光镜、透射电镜方法及三维重塑技术。结果：X线照射后，淋巴细胞发生凋亡和坏死，淋巴滤泡被破坏。之后，淋巴细胞逐渐增多，从照射后第5天开始，出现淋巴滤泡的再构筑；第10天淋巴滤泡数量增多并且出现生发中心；到照射后第14天，淋巴滤泡的数量正常。此外，滤泡树突状细胞的超微结构没有发生改变。结论：500md的X线可以破坏淋巴滤泡，受破坏的滤泡经过一定时期可以重新再聚集。再构筑的滤泡不是新产生的而是受损滤泡再生形成的。滤泡的再构筑与有无生发中心无关。     

~(192)Ir源两种刻度方法的比较

目的 通过对~（192）Ir源的再次刻度， 校准源活度的精确值。材料与方法： 用电离室法，分别测量源在水介质中和自由空气中的照射量率。结果： 两种方法在刻度~（192）Ir源活性上得到的结果是一致的。结论： 利用空气比释动能法可以对~（192）Ir源进行精确刻度。     

大鼠全身辐射损伤后小肠吸收功能变化的研究

目的：研究大鼠全身辐射损伤后小肠吸收Ｌ－酪氨酸（Ｔｙｒ）的变化。方法：用在体门静脉取血法研究了６Ｇｙ６０Ｃｏγ线全身一次照射后不同时间以及不同剂量照射后第３ｄ大鼠小肠吸收Ｔｙｒ的变化，并测定相应的小肠上皮细胞计数、小肠粘膜钠－钾－ＡＴＰ酶（Ｎａ＋－Ｋ＋－ＡＴＰａｓｅ）活性以及Ｎａ＋的跨膜转运。结果：６Ｇｙγ线全身照射后第３ｄ出现小肠对Ｔｙｒ的吸收障碍，以后很快恢复，并持续在正常水平。随着照射剂量的加大，吸收障碍加重，但３Ｇｙ以下剂量照射，则不出现Ｔｙｒ的吸收障碍。小肠上皮细胞计数、Ｎａ＋－Ｋ＋－ＡＴＰａｓｅ活性和Ｎａ＋的跨膜转运的变化与小肠吸收Ｔｙｒ的变化基本一致。结论：辐射损伤后小肠对Ｔｙｒ的吸收障碍与小肠上皮细胞数量减少导致的吸收面积的下降以及Ｎａ＋－Ｋ＋－ＡＴＰａｓｅ活性下降导致的Ｎａ＋跨膜转运能力的减弱有关。     

胎儿左心室壁血管与心腔交通的研究

目的：从发生学角度探讨心肌血管重建术的供血机理。方法：本文采用不同胎龄的人胎心１３个，用墨汁灌注血管、组织切片染色法，观测左心室壁与心腔的血管交通状况。结果：显示人类胚胎早期的心脏，心室壁结构类似海绵状，心腔与心壁间存在着许多窦状通道。这类管道包括肉柱间隙、心肌窦样管等，其排列、配布及在心室壁的分布范围随着胎儿生长、结构重建而不断变化。其胚胎发育过程重复了种系发生的各个阶段。结论：提示激光心肌血管重建术从心腔直接供血，与人胚早期者相类似。     

电离室阵列在电子束旋转照射剂量验证中的应用

目的:考察一种二维电离室阵列对斜入射电子线剂量测量的特性与误差,探讨其用于电子束旋转照射计划剂量分布验证的可行性。材料与方法:(1)在±50°范围内比较电离室阵列与指形电离室测量的差别并校准电离室阵列;(2)设计6和10MeV电子束旋转照射体模计划各三个(0°机架角时的射线束中心轴对称夹角30°、60°和90°)。用二维电离室阵列分别测量验证各计划的剂量分布。结果:(1)电离室阵列中心探头与指形电离室在上述斜入射条件下对6MeV/10MeV电子线的测量差别小于2%。(2)各电子线旋转照射计划在中心轴上最大剂量深度处的剂量误差均小于3%。离轴剂量比误差在非旋转方向上旋转射野中间70%区域内小于2%;在旋转方向上最大不超过1.5%。冠状平面上的100%～20%各等剂量曲线符合性较好;6MeV和10MeV的电子线的30°、60°、90°旋转照射计划的Gamma指数通过率(=5%和=5mm)分别为99.98%、99.89%、99.74%、98.64%、99.16%和99.44%。结论:所测试的二维电离室阵列对斜入射电子线测量误差能满足±50°范围内的电子束旋转治疗的计划剂量验证要求。     

The Aachen-keratoprosthesis--a flexible KPro that permits intraocular pressure measurement

PURPOSE: Postoperative glaucoma is one of the major complications observed in patients with keratoprostheses (KPro). The optical components of the majority of KPros are rigid and inflexible, which prevents indirect tonometry by common methods. This study confirms that the Aachen-KPro allows measurements of intraocular pressure (IOP) due to its flexible optical part with a modified Schiotz tonometer. METHODS: The Aachen-KPro was placed in a special chamber where pressure can be generated and monitored by a transducer. Measurements were taken by common ophthalmologic methods. The results were compared to the initial pressure values in the chamber. RESULTS: With the Goldmann tonometer, the Tono-Pen and the topography system (Technomed), no significant pressure changes could be observed. The results of the Schiotz tonometer were promising. It was slightly modified and standard curves with different weights could be obtained. CONCLUSIONS: With a modified Schiotz tonometer, it is possible to detect elevated IOPs. Modifying this common instrument is inexpensive and can be easily performed. This advantage of the Aachen-KPro permits early management of postoperative high tension glaucoma.     

Release of tryptase together with histamine during the immediate cutaneous response to allergen

Better in vivo techniques are needed for objective assessment of mast cell-dependent events. Tryptase, a neutral protease selectively concentrated in human mast cells, appears along with histamine in skin chamber fluid overlying sites of allergen challenge in sensitive human subjects. Maximal amounts of histamine were found 0 minutes to 30 minutes after challenge; maximal amounts of tryptase were found 30 minutes to 60 minutes after challenge. The later appearance of tryptase most likely reflects its slower diffusion through tissue after release of tryptase from cutaneous mast cells as a macromolecular complex with proteoglycan. The mean weight ratio of tryptase (134,000 molecular weight tetramer) to histamine (111 molecular weight) in chamber fluid after allergen challenge during a 1-hour time course was 4:1. Total amounts of tryptase and histamine recovered in the 0.3 ml chamber fluid samples after a 1-hour challenge averaged 95 ng and 26 ng, respectively. Tryptase levels in skin chamber fluid are an accurate indicator of mast cell activation.     

Dosimetric evaluation of a 2D pixel ionization chamber for implementation in clinical routine

In this paper we present the results of a dosimetric evaluation of a 2D ionization chamber array with the objective of its implementation for quality assurance in clinical routine. The pixel ionization chamber MatriXX (Scanditronix Wellhofer, Germany) consists of 32x32 chambers with a distance of 7.6 mm between chamber centres. The effective depth of measurement under the surface of the detector was determined. The dose and energy dependence, the behaviour of the device during its initial phase and its time stability as well as the lateral response of a single chamber of the detector in cross-plane and diagonal directions were analysed. It could be shown, that the detector's response is linear with dose and energy independent. Taking the lateral response into account, two different dose profiles, for a pyramidal and an IMRT dose distribution, were applied to compare the data generated by a treatment planning system with measurements. From these investigations it can be concluded that the detector is a suitable device for quality assurance and 2D dose verifications.     

A new extended-length parallel-plate ionization chamber

A special parallel-plate ionization chamber was developed. The motivation for the construction of this new chamber was mainly to fulfil the need of a reference system for computed tomography standard beams in the Calibration Laboratory of IPEN. However, the chamber was tested also in standard radiation beams of mammography and conventional diagnostic radiology. The chamber was manufactured at the institute workshop, as simply and cheaply as possible. Its design differs from the common ionization chambers used in dosimetric procedures of computed tomography equipment, because it is a parallel-plate chamber instead of a cylindrical chamber. However, its dimensions and sensitive volume are very similar to those of a commercial pencil ionization chamber. The new ionization chamber was submitted to several characterization and quality control tests, showing its very good performance.     

Polarity effect of plane-parallel ionization chambers in electron radiation

Although plane-parallel ionization chambers have been in use for some time, there is still much to be learned about their performance characteristics. This work is concerned with the polarity effect in electron beams about which there is little published data. The investigations involved several popular ionization chambers; the PTW Markus chamber, the NACP chamber and its Calcam version, the Vinten-631 chamber, and the NE 2571 (Farmer-type) thimble chamber. The chambers were irradiated in electron beams of nominal energies between 4 MeV and 18 MeV. It was found in this study that the NACP, Markus and Vinten chambers require a correction of the order of 0.2% in the energy range between 4.5 MeV and 18 MeV. The overall behaviour of the Calcam chamber was similar with the exception of energies below 4 MeV. The depth dependence of the polarity effect seemed closely related to the mean beam energy at the depth of measurement. There is some evidence that the effect is also dependent on the angular spread of the electron beam and its spectrum. The authors considered how best to quantify the polarity effect practically, and propose that it should be expressed as a correction factor to be applied to readings with one particular chamber bias.     

The measurement of kappach factors for application with the IPEMB very low energy dosimetry protocol

In 1996. the IPEMB issued a new code of practice detailing the procedures by which the output of therapeutic kilovoltage x-ray devices are to be determined. For x-ray beam qualities in the range 0.035-1.0 mm Al half-value thickness (HVL), the equation for converting the instrument reading into absorbed dose to water contained a factor named kch. This was included to account for the change in response of the parallel plate chamber from its calibration conditions free in air to those in the user's measurement phantom. As no data were available with which to quantify this factor at very low energies, the code advised that the user take a value of unity until sufficient data became available upon which to base an addendum. In this work, kch values have been determined for four chambers: two PTW 23344 large volume soft x-ray chambers, one PTW 23342 small volume soft x-ray chamber and a Markus electron chamber. Variations in the value of kch were investigated for changes in FSD, applicator size and beam quality. The water equivalence of the Mix-D phantom used for these measurements was also verified. A comparison of the results for the two PTW 23344 chambers showed no significant differences for any experimental situation, indicating that kch is a factor of chamber design rather than variations in construction. No variation in kch was identified with changes in FSD. A small dependence on applicator size was identified for larger applicators, and this was found to be dependent upon chamber design. The measured values of kch were found to increase with energy and again differences were seen between chamber designs. Overall, the values of kch recorded during these measurements ranged from 1.01 to 1.08. These results highlight a significant underestimation of doses calculated using the very low energy code of practice. This supports the need for further work to confirm these results. and the production of an addendum to the code in its present form.     

高度近视白内障摘除人工晶体植入术

目的评价高度近视白内障摘除及人工晶体植入术的临床疗效 .方法对眼轴长 >2 6mm的 39例 (43只眼 )高度近视并发白内障患者 ,施行白内障摘除及人工晶体植入术 .结果平均随访 2 4个月 (12～ 48个月 ) ,眼轴2 6～ 2 8mm 2 5只眼 ,术后矫正视力 >0 5的 2 2只眼 ,占 88% ,眼轴长 >2 8mm 18只眼 ,术后矫正视力 >0 5的 4只眼 ,仅占 2 2 % .术后未见视网膜脱离、青光眼、角膜营养不良等并发症 .结论高度近视眼白内障行人工晶体植入术 ,安全可靠 ,手术并发症少 .视力差的主要原因为眼底病变 ,并随眼轴长增加而增加 .     

Immune privilege in the anterior chamber of the eye: alloantigens and tumour-specific antigens presented into the anterior chamber simultaneously induce suppression and activation of delayed hypersensitivity to the respective antigens.

Allografts placed into the anterior chamber of the eye enjoy prolonged and sometimes permanent survival while similar grafts are promptly rejected if transplanted to non-privileged sites. The immunological privilege of the anterior chamber is due, in large part, to the systemic suppression of delayed-type hypersensitivity (DTH) that is induced by anterior chamber presentation of alloantigens and is termed anterior chamber-associated immune deviation (ACAID). Although many categories of antigens elicit ACAID, strong tumour-specific transplantation antigens (TSTA) do not induce ACAID and instead, provoke potent DTH responses following anterior chamber presentation. The present study sought to determine if the anterior chamber were simultaneously confronted with these two categories of antigens, which systemic immune response would prevail: DTH or suppression of DTH? The results show that inoculation of minor histocompatibility alloantigens and TSTA into the anterior chamber induced both afferent and efferent suppression of specific anti-alloantigen DTH responses, yet simultaneously induced normal anti-TSTA DTH responses. Both responses (i.e. DTH and suppression) were transferable with lymphoid cells.