BENNETT乳腺机自动曝光功能的原理及维修

1故障现象 不能自动曝光,手动曝光后,操作面板的显示屏上显示：Back up reset。2故障原理 自动曝光系统由微处理器板、自动曝光控制板D10和半导体电离室组成[1]。在自动曝光模式中,电离室内的固态AEC传感器检测通过胶片盒的X线能量连接到AEC板的J2上。A/DC电流与传感器上产生的能量成正比,共同作为U13和U14构成的积分电路的输入。     

数字乳腺机不同曝光模式对辐射剂量的影响研究

目的 研究数字乳腺摄影机在自动曝光(AEC)与手动曝光模式下图像质量达到诊断要求时,两者辐射剂量有无差别。方法 采用西门子MAMMOMAT NovationDR型数字乳腺机,应用自动曝光(AEC)和手动曝光模式对20mm厚标准乳腺模体和X线用矩形波测试卡进行照射,记录其辐射剂量并观察测试卡显示的线对数,再对同一病人的左右乳房分别采取自动曝光(AEC)和手动曝光模式进行照射,记录其辐射剂量并观察照片有无差别。结果 在自动曝光(AEC)和手动曝光模式下对模体和测试卡所摄照片显示的线对数都达到4lp时,手动曝光可比自动曝光(AEC)模式下调曝光剂量50%,辐射剂量减少50%,在同一临床病例实验中,曝光剂量相差50%所照射的照片除放大相同倍数外再不经过任何后处理让2位副主任职称以上医师进行阅读,结果两张照片无明显差别,全部达到诊断要求。结论 在实际工作中应根据不同乳腺压迫厚度掌握手动曝光摄影条件,并尽可能应用手动曝光进行摄影,以尽量减少患者的辐射剂量。     

AEC模式下CTDI剂量指数指导意义初探

CT生产厂商推出了自动曝光控制AEC技术,根据受检者的体态调节管电流,达到减小辐射剂量的目的。在扫描过程中采用AEC技术,系统会给出一个剂量指数CTDI_(vol),但对于整个扫描过程,实际的CTDI_(vol)是随着管电流的改变而不断改变的。因此,厂商提供的CTDI_(vol)到底有什么指导意义,本文将以临床实验和计算机软件模拟相结合的方法,探讨系统剂量指数的指导意义。     

自动曝光控制在数字化摄影中的应用

探讨自动曝光控制在数字化摄影中的合理应用,进一步提高数字化摄影图像质量。在自动曝光控制条件下数字化摄影中,关键是要选择合适的kV值,同时还要选择合适的电离室、密度补偿值和和必要的图像后处理。     

东芝KXO-15C X光机系统中的AEC电路原理与维修

自动曝光控制简称AEC,在过去操作者为了获得最佳的胶片密度必须努力选择适宜的曝光参数kV.mA和sec,就算很有经验的操作者要获得最佳的曝光,也是困难的,胶片密度也总是不合适宜,在X线诊断系统中,AEC的角色就是在短时间内,用简单的操作将最佳的密度的X线影像自动的提供给使用者。     

自动曝光控制在计算机X线摄影中的合理应用

探讨自动曝光控制在计算机X线摄影中的合理应用,进一步提高摄影图像质量.在自动曝光控制条件下计算机X线摄影中,关键是要选择合适的KV值,同时还要选择合适的电离室、密度补偿值和和必要的图像后处理.     

鼻骨DR摄影不同曝光模式的辐射剂量和图像质量比较

目的 探讨鼻骨DR不同曝光模式辐射剂量和图像质量的关系。方法 用DR出厂设定的鼻骨曝光量对PMMA模拟鼻骨厚度1.25cm和对比度细节体模(CDRAD2.0)组合行自动曝光控制(AEC)摄影,选定合理的曝光量为65kV、1mAs。对不同曝光量下mAs、ESD、DAP和IQF值的差异和不同曝光模式图像的影像诊断效能行统计学分析。结果 ①固定管电压65kV,随着mAs提高ESD、DAP增加,其间比较有显著性差异(F=1106、1416,P < 0.05)。IQF值变化不明显,差异比较无统计学意义。②固定管电流1 mAs,55 kV时,曝光量不足。65kV~85kV的ESD、DAP之间差异比较有统计学意义,IQF值差异比较无统计学意义。不同曝光模式图像诊断鼻骨骨折的ROC曲线下面积之间比较无显著性差异。结论 ①在保证图像质量的前提下,65 kV、0.5 mAs手动曝光较65 kV自动曝光的辐射剂量更低,可作为成人鼻骨DR手动曝光模式的适宜曝光量。②AEC初始曝光量的设定水平有必要校验,其有助于手动模式适宜曝光量范围的确定。     

乳腺CR曝光量对影像质量的影响

探讨X线曝光量的控制在乳腺CR影像质量的用法;采用调整后的Planmed钼靶X线机配合柯达乳腺专用IP板对852人次应用自动曝光控制(AEC)使之适应乳腺CR摄影的要求,使AEC的X线曝光量适合IP板的感光度;使用调整后的钼靶X线机配合CR在安全的病人剂量(AGD)的前提下能够获得较高的钼靶乳腺CR图像质量,应用调试后的钼靶X线乳腺机AEC,降低了被检者的受线剂量,保证了稳定的钼靶乳腺CR的图像质量。     

佛山市医疗机构DR系统质量控制和放射防护检测结果

目的分析佛山市医用数字X射线摄影(DR)系统质量控制和机房放射防护现状。方法 2018年6—9月采用分层抽样方法,以佛山市19家医院的45台DR系统为研究对象,按照WS 521-2017《医用数字X射线摄影(DR)系统质量控制检测规范》和GBZ 130-2013《医用X射线诊断放射防护要求》的检测要求和技术指标,对DR设备的质量控制及其机房的放射防护情况进行评价与分析。结果佛山市抽取的19家医院共45台DR设备质量控制检测合格率为53.3%,其中,三级医院合格率为73.3%,二级医院合格率为50.0%,一级及以下医院合格率为37.5%,差异无统计学意义(P0.05)。检测项目中光野与照射野四边的偏离、响应均匀性和自动曝光控制(AEC)电离室之间一致性的不合格率较高,管电压指示的偏离、输出量重复性和有用线束半值层的合格率为100.0%。45间DR机房共对476个点的周围剂量当量率进行检测并根据工作量估算年剂量,各检测点均符合标准要求,但仍存在辐射泄露情况,其中机房的门、观察窗等泄漏率较高,分别达到45.1%和25.5%。结论佛山市医用DR系统质量控制检测不合格率较高,DR机房存在较高泄漏风险,仍需加强设备维护和保养,完善辐射安全管理。     

X线机自动曝光控制电离室的研制及其特性研究

研制用于医用诊断Ｘ线机自动曝光控制用电离室，并对其各种输出特性进行了实验测量与研究。电离室中心电极采用了静电喷涂石墨电极，因此不会在胶片上形成影像，为增大电离室输出效率电离室采用复式结构，减小了电离室厚度与极间电容。研制的电离室可方便安装于不同Ｘ线机上，其输出信号与输入射线强度线性良好，线质响应均匀，输出时间响应线性良好。     

Evidence for the presence of a type III secretion system in diffusely adhering Escherichia coli (DAEC).

Diffusely adhering Escherichia coli (E. coli) strains (DAEC) represent a potential cause of diarrhoea in infants, and the detection of type three secretion system (TTSS) genes in DAEC would substantiate their pathogenic nature. In this work, four isolates of DAEC, recovered from stools of diarrhoeic children, were analysed by PCR, in order to detect the presence of TTSS genes. Primers targeted to the escC, escJ, escN and escV, some of the most conserved TTSS genes in enteropathogenic and enterohaemorrhagic Escherichia coli (EPEC and EHEC), were used in order to verify the occurrence of homologous genes in our DAEC isolates. By this approach, we were able to characterise DNA fragments corresponding to putative escJ and escN genes in all DAEC isolates. Furthermore, DNA fragments homologous to the escC and escV genes were also amplified from all isolates. Besides the similarity found among the DAEC esc homologues with EPEC and EHEC esc genes, the nucleotide sequence analysis of the flanking regions of the amplified DNA fragments suggests that the putative DAEC esc genes are organised in the same manner as observed in EPEC and in EHEC strains. The results described here provide strong evidence for the presence of a TTSS in the DAEC strains analysed, implicating a pathogenic nature of these isolates.     

电离室与摄影部位的关系对图像质量的影响

介绍自动曝光控制系统原理的基础上,通过具体的实验讨论了电离室与摄影部关系的选择及其对X线图像质量的影响.     

Prospective study of verocytotoxin-producing, enteroaggregative and diffusely adherent Escherichia coli in different diarrhoeal states.

One hundred and eighty-one stool specimens from patients with various types of diarrhoea (135 patients) or from non-diarrhoeal controls (23 acute medical patients, 23 inflammatory bowel disease in remission) were investigated using a colony-blot DNA hybridization assay for the presence of Verocytotoxin-producing (VTEC), enteroaggregative (EAggEC) and diffusely adherent (DAEC) Escherichia coli. Twelve patients had probe-positive EAggEC in the stool and 8 of these had diarrhoea, 6 following recent travel. Eight patients had DAEC, 7 of whom had travellers'' diarrhoea. Six of 10 (60%) travellers with gastroenteritis, but without a recognized enteric pathogen, were positive for EAggEC (4) or DAEC (2). Five of 10 (50%) travellers with gastroenteritis related to a recognized enteric pathogen also had DAEC identified in their stool. Of the 23 acute medical control patients 11 had been abroad, 4 of these were immigrants and had EAggEC. VTEC were not found and, with one exception, immunoassays for antibodies to E. coli O 157 and O 2 lipopolysaccharides were negative.     

Quantification of the temperature equilibrium time of the cavity in parallel-plate-type ionization chambers by thermal analysis

Temperature corrections are necessary to account for the varying mass of air in the cavity volume of a vented ionization chamber. The temporal response resulting from temperature changes in a cylindrical and/or Farmer-type ionization chamber, which is the standard dosimeter, has been thoroughly discussed by some researchers. The purpose of this study was to characterise and analyse the dependence of the cavity air temperature of the parallel-plate-type ionization chamber on changes in the ambient temperature. Ionization chambers NACP-02 (IBA Dosimetry, GmbH) and Advanced Markus TN34045 (PTW, Freiburg) were modelled using thermal analysis software to present the temperature equilibrium time and the entire ionization chamber temperature distribution. The temporal response of each ionization chamber was measured for comparing the calculation results of the thermal analysis. The ionization chamber cavities of NACP-02 and TN34045 reached complete equilibrium in 670 and 750 s, respectively. Heat transfer occurred faster at the centre of the front wall of TN34045 than at the outside of the centre except for the edges. Further, the non-uniformity of temperature in the cavity was in the range of 24.2–24.8°C for NACP-02 and 23.7–24.4°C for TN34045 at 200 s after the ionization chamber was installed in the water phantom. The previous proposal to wait for about 15 mins after submerging the chamber in a water phantom before the measurement is demonstrated to be appropriate for parallel-plate-type ionization chambers.     

Lessons learned from a HDR brachytherapy well ionisation chamber calibration error

The outcomes of a recent brachytherapy well-type ionization chamber calibration error are given in the hope that other brachytherapy treatment centres may better understand the importance of each entry stated in a well chamber calibration certificate. A Nucletron Source Dosimetry System (SDS) PTW well-type ionization chamber was sent for a biennial calibration in September 2010. Upon calibration of the chamber, it was discovered that the previous calibration (in July 2008) contained a +2.6% error in the chamber calibration coefficient. Investigation of the information on the 2008 well chamber calibration certificate indicated the source of the error, which could or should have been detected by both the calibration laboratory and/or the radiation therapy department upon return of the chamber. Consideration must be given to all values and conditions given on the calibration certificate when accepting a ionization chamber back from a calibration laboratory. The issue of whether the source strength from the source calibration certificate or the measured source strength from the calibrated ionization chamber should be entered into the treatment unit is also raised.     

一种直线加速器电离室保护装置的研制

目的:为了减少因电离室工作温度、湿度变化引起的直线加速器故障,延长直线加速器电离室使用寿命,设计一种电离室保护装置。方法:通过使用温度23℃、湿度15%、流量10L/min的干燥空气吹拂电离室的方法,改变电离室的工作环境,减少外部应用环境的变化对电离室产生的不良影响。结果:将装置安装在2台直线加速器上使用,同比上年同期的故障次数,故障率减少80%以上。结论:通过实际运行及参数检测,该电离室保护装置运行稳定,在一定程度上改善了电离室的工作环境,可以减少外部应用环境的变化对电离室产生的不良影响,减少电离室故障,延长使用寿命。     

针尖电离室水中吸收剂量校准方法研究

目的 ⁶⁰Co γ射线下,建立针尖电离室水中吸收剂量校准方法。方法 参考剂量仪（DOSE 1静电计+FC65-G型电离室）经过中国计量科学研究院校准,得到水中吸收剂量校准因子。采用⁶⁰Co γ射线,IAEA TRS-398测量程序,用参考剂量仪测量水下10 cm吸收剂量。替代法,用针尖电离室剂量仪进行水吸收剂量测量并对其进行水吸收剂量因子校准。更换⁶⁰Co γ射线辐射场,用参考剂量仪、针尖电离室剂量仪进行剂量验证测量。结果 参考剂量仪在水下10 cm处,参考条件下测得水吸收剂量结果为0.249 9 Gy。两台针尖电离室剂量仪测量结果分别为0.248 0 Gy和0.250 0 Gy;两台针尖电离室剂量仪测量结果与参考剂量仪测量结果相对偏差均在±0.8%内,针尖电离室剂量仪测量水吸收剂量不确定度为2.8%（k=2）。结论 针尖电离室可用于小野水中吸收剂量的测量。     

利用二维电离室矩阵进行调强放疗计划剂量验证的探讨

目的：探讨二维电离室矩阵在调强放疗（IMRT）计划剂量验证中的应用价值。方法选取于我院行IMRT的患者16例,先在治疗计划系统中进行计划设计,然后移植到固体水上,得到体模杂交计划;利用二维电离室矩阵对杂交计划的计算剂量进行验证;参照3%/3 mm标准对结果进行分析。结果所有治疗野的绝对剂量验证结果通过率为86.4%-100%;相对剂量验证结果通过率为88.5%-100%。结论二维电离室矩阵是一种快速的剂量测量系统,在IMRT计划剂量验证中有重要价值。     

Mammographic image quality and exposure in South East Asia

Generally there is a significant delay before optimized performance of mammography is fully realized in the developing countries. To evaluate the status of mammographic performance, a survey of mammographic image quality and exposure was performed in nine hospitals from four selected South East Asian countries. The entrance exposure on the surface of the American College of Radiology (ACR) mammographic phantom (ACR-RMI model 156) was made using both thermoluminescent dosimeters (TLDs) and an ionization chamber. The TLDs were mailed from the University of Wisconsin Radiation Calibration Laboratory (UWRCL) to the cooperating hospitals. The surveyed hospitals processed the images and returned them to the UWRCL for subsequent evaluation of the image quality of the mammographic phantom. Machine-specific data, technique factors and sensitometric data were also obtained. At 28 kVp, the mean entrance exposure is 0.91 R (0.46 to 2.6 R), mean glandular dose is 1.61 mGy (0.90 to 4.15 mGy), mean optical density is 1.37 (0.66 to 2.30), mean total phantom image score is 9.1(4-12). Only three of the nine hospitals tested achieved an acceptable score above the minimum 10. Results for 25 and 30 kVp showed similar trend. The variation between the ion chamber measurements and TLD measurements ranged from 4 to 24%. There is a wide variation in the image quality and entrance exposure among hospitals in South East Asia. There is a need for a quality assurance program. The factors that cause low score in the phantom images must be corrected. Calibration and the use of appropriate ionization chambers for mammography is important.     

用于中低能质子回旋加速器剂量监测的空气电离室初步研究

目的 研制用于测量中低能质子回旋加速器产生的伽玛场的空气电离室。方法 分别采用有限元分析方法和蒙特卡罗方法模拟计算空气电离室的电场分布和伽玛射线在电离室中的能量沉积，确定电离室各个部分的机械尺寸和结构；根据中低能回旋加速器实际运行时的剂量率情况，设计了低电流放大器，并进行了初步校准试验。结果 模拟结果表明空气电离室对1~8 MeV的光子灵敏度在±30%以内，信号输出噪声小于2 mV，运行稳定。结论 初步测试结果表明，该电离室工作稳定，能量响应范围宽，满足设计指标要求。