迈入新世纪的硼中子俘获疗法（BNCT）

扼要叙述进入21世纪之际,硼中子俘获疗法(boron neutorn capture therapy,BNCT)在国际范围内的一些显著进展,包括BNCT的临床定位、肿瘤复发的探索、硼浓度的定量探测、靶向掺硼药物的开发以及我国医院中子照射器的问世.这些BNCT长期开发中的瓶颈趋于缓解,预示了BNCT个性化与例行化的前景更为清晰.     

BPA接枝聚乙二醇化壳聚糖的合成与表征

硼中子俘获疗法(Boron Neutron Capture Therapy,BNCT)是当前治疗脑胶质瘤等恶性肿瘤的唯一有效方法,而对恶性肿瘤有高特异性的含硼药物的制备是硼中子捕获治疗研究中的一个重点。用已知BNCT药物BPA接枝mPEG-壳聚糖,进一步提高BPA的水溶性及肿瘤对硼药物的摄取率,以期达到BNCT药物的要求。目标产物通过红外,核磁表征表明聚乙二醇和BPA都成功的链接到壳聚糖上,所制得的产物有望成为潜在的BNCT药物。     

医院中子照射器I型堆热中子束流孔道等效平面源的模拟计算

采用蒙特卡罗程序MCNP模拟计算了医院中子照射器Ⅰ型堆(IHNI-1)热中子束流孔道出口处的等效平面源.对B堆芯进行了临界搜索计算,模拟计算了热中子束流孔道及出口处中子、γ的束流参数,应用等效平面源模型建立了BNCT等效中子、γ平面源.为人体头颅等效模型剂量分布的快速计算提供了较为可靠的平面源.     

MCDB蒙特卡罗剂量计算系统及应用

硼中子俘获治疗(BNCT)蒙特卡罗剂量计算软件系统MCDB(Monte Carlo dosimetry code for brain)已经开发成功.它包括医学前处理、剂量计算和后处理.前处理把CT、MRI图像数据自动转化为剂量计算的输入文件,剂量计算基于蒙特卡罗(MC)方法,后处理是确定照射方向和照射时间.为了提高剂量计算的精度和缩短计算时间,MCDB发展了针对体素模型的快速粒子径迹算法,构造材料矩阵和计数矩阵,程序实现了MPI并行化.通过一个病例,MCDB完成了从CT、MRI提取数据、剂量计算和后处理的全过程.计算取得了与MCNP程序一致的结果,串行计算速度较MCNP提高3倍以上,并行效率可以达到90％,完全满足临床对计算精度和计算时间的要求.     

聚乳酸纤维的研究进展

聚乳酸是一种新型的生态环保型高分子材料.本文主要介绍了世界各国对聚乳酸纤维研究及生产的相关情况,对聚乳酸的生产工艺作了深入的探究,并介绍了聚乳酸的应用及发展前景.     

变频器用调速在工艺生产中的应用

本文主要介绍了变频器的工作原理和控制方式，文中遵循理论和实际相结合的原则，对变频器的工作原理和控制方式作了系统的分析，并介绍了变频器在生产中的应用情况及效果。     

膜法富氧技术在燃煤锅炉上的应用

介绍了膜法富氧助燃技术及装置首次运用于燃煤蒸汽锅炉的运行情况,对该技术的节能机理作了简要阐述,介绍了该技术的工艺流程及设备、 安装及调试情况,并对节能效果作了分析,具有显著的综合效益,半年左右收回投资。     

血液透析器膜材料研究进展

从膜材料的血液相容性、可纺性以及价格等因素出发,简要介绍了影响透析膜膜材料性能的因素.通过大量调研发现目前临床上的透析膜所使用的膜材料主要有纤维素类、聚砜类、聚丙烯腈类以及聚氨酯类等.在前人研究的基础上,对透析器膜材料的国内外进展情况作了全面综述,并对其发展趋势作出预测.     

水源热泵设计及应用实例

对水源热泵空调系统的设计作了一个简单的总结,针对四川大学新校区图书馆的工程实例空调设计,对如何选择水源热泵空调系统、系统的设计情况及建成后的使用效果作了介绍。     

污染物在室内的运动规律

对一些主要的或具有代表性的污染物的影响因素及变化情况作简要的介绍.通过了解污染物在室内的变化规律有效控制室内污染物.     

Application of TEPC microdosimetry to boron neutron capture therapy

Boron neutron capture therapy (BNCT) is a bimodal radiation therapy used primarily for highly malignant gliomas. Tissue-equivalent proportional counter (TEPC) microdosimetry has proven an ideal dosimetry technique for BNCT, facilitating accurate separation of the photon and neutron absorbed dose components, assessment of radiation quality and measurement of the BNC dose. A miniature dual-TEPC system has been constructed to facilitate microdosimetry measurements with excellent spatial resolution in high-flux clinical neutron capture therapy beams. A 10B-loaded TEPC allows direct measurement of the secondary charged particle spectrum resulting from the BNC reaction. A matching TEPC fabricated from brain-tissue-equivalent plastic allows evaluation of secondary charged particle spectra from photon and neutron interactions in normal brain tissue. Microdosimetric measurements performed in clinical BNCT beams using these novel miniature TEPCs are presented, and the advantages of this technique for such applications are discussed.     

Preliminary evaluations of the undesirable patient dose from a BNCT treatment at the ENEA-TAPIRO reactor

Boron neutron capture therapy (BNCT) is an experimental technique for the treatment of certain kinds of tumors. Research in BNCT is performed utilizing both thermal and epithermal neutron beams. Epithermal neutrons (0.4 eV-10 keV) penetrate more deeply into tissue and are thus used in non-superficial clinical applications such as the brain glioma. In the last few years, the fast reactor TAPIRO (ENEA-Casaccia Rome) has been employed as a neutron source for research into BNCT applications. Recently, an 'epithermal therapeutic column' has been designed and its construction has been completed. The Monte Carlo code MCNPX was employed to optimize the design of the column and to evaluate the dose profiles and the therapeutic parameters in the cranium of the anthropomorphic phantom ADAM. In the same context, some preliminary evaluations of the undesirable doses to the patient were performed with MCNPX. A hermaphrodite phantom derived from ADAM and EVA was employed to evaluate the energy deposition in some organs during a standard BNCT treatment. The total dose consists of the contributions from the primary neutron beam, the neutron interactions with boron and the neutron induced photons generated in the epithermal column structures and in the patient's tissues. The paper summarizes the computational procedure and provides a general dosimetric framework of the patient radiological protection aspects related to a BNCT treatment scenario at the TAPIRO reactor.     

硼中子俘获治疗人脑胶质母细胞瘤的前景和困惑

硼中子俘获疗法是一种可以选择性杀伤肿瘤细胞的放射疗法,其产生的α粒子对临床治疗新诊断和复发的脑胶质母细胞瘤有较好的疗效.发达国家20世纪五六十年代就已进入临床试验,但一直受到硼携带载体和中子源发展的限制.现就其治疗脑胶质母细胞瘤的前景做一综述.     

Use of the CT images for BNCT calculation: development of BNCT treatment planning system and its applications to dose calculation for voxel phantoms

A BNCT (Boron Neutron Capture Therapy) treatment planning system (BTPS) was developed for BNCT study and treatment planning. Three kinds of CT images, VHP, PINNACLE and DICOM images, were employed to make voxel phantoms for BNCT patient treatment using the BTPS. The thermal neutron, fast neutron, gamma and boron doses are calculated and background, tissue, and tumour doses for idealised standard reactor neutron field (ISRNF) neutron beam were calculated by using BTPS and MCNP code. It was noted that the total computing times needed for BNCT analysis could be greatly reduced since the BTPS system provides a dose analysis tool and a lengthy MCNP input in a short time. It is, thus, expected that the BTPS can significantly contribute the BNCT study for the treatment of patients.     

硼中子俘获疗法治疗脑胶质瘤及难治性垂体腺瘤的现状及展望

硼中子俘获疗法在脑胶质瘤治疗研究中已经取得很大进展,但由于脑胶质瘤的特性以及缺乏与肿瘤高亲和力的掺硼药物,硼中子俘获治疗的效果并不十分理想.此外,难治性垂体腺瘤具有很多与脑胶质瘤相同的特点,硼中子俘获疗法可能具有一定的意义.文章重点介绍硼中子俘获疗法治疗脑胶质瘤的研究现状和治疗难治性垂体腺瘤的可能性.     

A toolkit for epithermal neutron beam characterisation in BNCT

Methods for dosimetry of epithermal neutron beams used in boron neutron capture therapy (BNCT) have been developed and utilised within the Finnish BNCT project as well as within a European project for a code of practise for the dosimetry of BNCT. One outcome has been a travelling toolkit for BNCT dosimetry. It consists of activation detectors and ionisation chambers. The free-beam neutron spectrum is measured with a set of activation foils of different isotopes irradiated both in a Cd-capsule and without it. Neutron flux (thermal and epithermal) distribution in phantoms is measured using activation of Mn and Au foils, and Cu wire. Ionisation chamber (IC) measurements are performed both in-free-beam and in-phantom for determination of the neutron and gamma dose components. This toolkit has also been used at other BNCT facilities in Europe, the USA, Argentina and Japan.     

Normalisation of prescribed dose in BNCT

Normalisation of prescribed dose in boron neutron capture therapy (BNCT) is needed to facilitate combining clinical data from different centres in the world to help expedite development of the modality. The approach being pursued within the BNCT community is based upon improving precision in the measurement and specification of absorbed dose. Beam characterisations using a common method are complete as are comparative dosimetry measurements between clinical centres in Europe and the USA. Results from treatment planning systems at these centres have been compared with measurements performed by MIT, and the scale factors determined are being confirmed with independent tests using measurements in an ellipsoidal water phantom. Dose normalisations have successfully been completed and applied to retrospectively analyse treatment plans from Brookhaven National Laboratory (1994-99) so that reported doses are consistently expressed with the trials performed during 1994-2003 at Harvard-MIT. Dose response relationships for adverse events and other endpoints can now be more accurately established.     

Gel dosimetry in the BNCT facility for extra-corporeal treatment of liver cancer at the HFR Petten

A thorough evaluation of the dose inside a specially designed and built facility for extra-corporeal treatment of liver cancer by boron neutron capture therapy (BNCT) at the High Flux Reactor (HFR) Petten (The Netherlands) is the necessary step before animal studies can start. The absorbed doses are measured by means of gel dosemeters, which help to validate the Monte Carlo simulations of the spheroidal liver holder that will contain the human liver for irradiation with an epithermal neutron beam. These dosemeters allow imaging of the dose due to gammas and to the charged particles produced by the (10)B reaction. The thermal neutron flux is extrapolated from the boron dose images and compared to that obtained by the calculations. As an additional reference, Au, Cu and Mn foil measurements are performed. All results appear consistent with the calculations and confirm that the BNCT liver facility is able to provide an almost homogeneous thermal neutron distribution in the liver, which is a requirement for a successful treatment of liver metastases.     

Characterisation of an accelerator-based neutron source for BNCT versus beam energy

Neutron capture in ¹⁰B produces energetic alpha particles that have a high linear energy transfer in tissue. This results in higher cell killing and a higher relative biological effectiveness compared to photons. Using suitably designed boron compounds which preferentially localize in cancerous cells instead of healthy tissues, boron neutron capture therapy (BNCT) has the potential of providing a higher tumor cure rate within minimal toxicity to normal tissues. This clinical approach requires a thermal neutron source, generally a nuclear reactor, with a fluence rate sufficient to deliver tumorcidal doses within a reasonable treatment time (minutes). Thermal neutrons do not penetrate deeply in tissue, therefore BNCT is limited to lesions which are either superficial or otherwise accessible. In this work, we investigate the feasibility of an accelerator-based thermal neutron source for the BNCT of skin melanomas. The source was designed via MCNP Monte Carlo simulations of the thermalization of a fast neutron beam, generated by 7 MeV deuterons impinging on a thick target of beryllium. The neutron field was characterized at several deuteron energies (3.0–6.5 MeV) in an experimental structure installed at the Van De Graaff accelerator of the Laboratori Nazionali di Legnaro, in Italy. Thermal and epithermal neutron fluences were measured with activation techniques and fast neutron spectra were determined with superheated drop detectors (SDD). These neutron spectrometry and dosimetry studies indicated that the fast neutron dose is unacceptably high in the current design. Modifications to the current design to overcome this problem are presented.