Effect of exposure factors on image quality in screening mammography

IntroductionThe aim of this research was to study the effect of exposure factors on image quality for digital screening mammography units in Kuwait which use Tungsten (W) targets with Rhodium (Rh) and Silver (Ag) as filters.MethodsMammography Accreditation Phantom Model 015 was imaged using a Hologic Selenia Digital mammography unit with W targets and Rh and Ag filters. Four images, each at 26, 28, 30, and 32 kVp, were obtained using each target-filter combination (W/Rh and W/Ag). The images were evaluated by five senior technologists for the number of specks, fibers and masses visible on each image. Statistical analysis was carried out using non-parametric tests at p = 0.05 level.ResultsThere were significant changes in the visibility of fibers and specks between different kVp values with W/Rh (p < 0.001). However, with W/Ag combination, significant differences were observed in the fibers only (p < 0.001). Among the kVp values used, 28 kV emerged as the optimal value. Comparison of images obtained with the two filter materials, led to significant differences in the visibility of fibers and specks (p < 0.008). At 32 kVp, there were significant differences in the visibility of specks only (p < 0.008).ConclusionA W/Rh target-filter combination provides better image quality than that provided by W/Ag. In particular, 30 and 32 kVp X-ray beams produce higher quality images than the lower kV values.     

双轴旋转冠脉造影术与常规冠状动脉造影术的临床应用效果及辐射剂量比较

目的：比较双轴旋转冠脉造影(XperSwing)术与常规冠状动脉造影（CCA）术的临床应用效果和辐射剂量,评价2种冠脉造影技术的差异性及临床价值。方法：收集行临床冠脉造影检查患者30例,其中CCA组20例,XperSwing组10例,分析2组患者检查的透视时间、对比剂用量和图像质量评分。应用中国人仿真胸部体模模拟XperSwing技术及CCA检查环境,将热释光个人剂量计（TLD）布放于仿真胸部体模的主要组织器官,测量各组织器官的吸收剂量,计算2种冠脉造影技术的有效剂量。结果：与CCA组比较,XperSwing组患者的对比剂用量减少27.74%（P<0.05）,透视时间和图像质量评分差异无统计学意义（P>0.05）;XperSwing组仿真胸部体模各组织器官平均吸收剂量低于CCA组（P<0.05）;XperSwing组有效剂量（4.94 mSv）低于CCA组（5.57 mSv）。结论：XperSwing　术可满足冠脉造影图像质量要求,并可有效降低冠脉造影的对比剂用量和辐射剂量。
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低场磁共振FLAIR序列对脑脊液内钆剂浓度检出的实验研究

 目的 探讨低场磁共振液体衰减反转恢复序列T2WI对人工脑脊液(cerebral spinal fluid,CSF)内钆浓度的识别水平,为临床应用提供依据.方法 采用浓度0～8 mmol/L的Gd-DTPA人工CSF溶液模拟CSF内不同的强化水平,新鲜熟蛋清模拟正常脑实质.使用0.35T机型,对样本分别行SE序列T1WI和快速FLAIR序列T2WI扫描,测算出各被检样本与参照样本间的对比噪声比(contrast-to-noise ratios,CNR),比较两种成像序列所能检出的最低钆剂浓度.结果 FLAIR序列T2WI所能识别的最低钆剂浓度为0.0078 mmol/L,比SE序列T1WI约低10倍;当样本内钆剂浓度超过0. 8 mmol/L时,FLAIR序列T2WI的检出能力不及SE序列T1WI.结论 低场磁共振FLAIR序列T2WI对人工CSF内低浓度钆剂的检出能力明显优于其SE序列T1WI.     

应用统计学体模评价CR乳腺摄影影像的探讨

目的应用ALVIM统计学体模TRM,探讨乳腺计算机X线摄影(CR)获得尺寸最小的Al2O3斑点(钙化灶)和尼龙纤维(肿块灶)信号的能力。方法将具有各5种大小不同Al2O3斑点和尼龙纤维组成的ALVIM统计学体模TRM置于成像板(IP)上,用钼靶X线机26kV,调节毫安量,选择适当图像处理参数,获得一张密度值D=0·70±0·05的实验照片,用5值判断法取得每一行由5个信号和噪声所组成的10行信号的记分总值,用ALVIM统计学体模的计算公式计算出一组真阳性概率P(S/s)和假阳性概率P(S/n)值,绘制ROC曲线,并计算出每种信号的判断概率值Pdet,再用SPSS10·0统计学单因素方差分析软件处理数据,获得尺寸最小的钙化灶和软组织肿块灶。结果用概率统计方法获得制作ROC曲线的数据和判断概率平均值Pdet,5种大小不同的Al2O3斑点(钙化灶)中,0·20mm的Pdet=0·6250最小,0·55mm的Pdet=0·9000最大,而0·20mm与0·25mm的Pdet差异无统计学意义,与其他的差异有统计学意义;5种大小不同的尼龙纤维(肿块灶)中,0·45mm的Pdet=0·5313最小,1·00mm的Pdet=0·8813最大,而0·45mm的与0·60mm的差异无统计学意义,0·45mm与其他的差异有统计学意义。结论应用ALVIM统计学体模TRM制作ROC曲线和获得判断概率值Pdet的计算简单、快捷,宜于日常临床工作开展的评价影像质量控制,值得推广。     

Assessment of calcium scoring performance in cardiac computed tomography

Electron beam tomography (EBT) has been used for cardiac diagnosis and the quantitative assessment of coronary calcium since the late 1980s. The introduction of mechanical multi-slice spiral CT (MSCT) scanners with shorter rotation times opened new possibilities of cardiac imaging with conventional CT scanners. The purpose of this work was to qualitatively and quantitatively evaluate the performance for EBT and MSCT for the task of coronary artery calcium imaging as a function of acquisition protocol, heart rate, spiral reconstruction algorithm (where applicable) and calcium scoring method. A cardiac CT semi-anthropomorphic phantom was designed and manufactured for the investigation of all relevant image quality parameters in cardiac CT. This phantom includes various test objects, some of which can be moved within the anthropomorphic phantom in a manner that mimics realistic heart motion. These tools were used to qualitatively and quantitatively demonstrate the accuracy of coronary calcium imaging using typical protocols for an electron beam (Evolution C-150XP, Imatron, South San Francisco, Calif.) and a 0.5-s four-slice spiral CT scanner (Sensation 4, Siemens, Erlangen, Germany). A special focus was put on the method of quantifying coronary calcium, and three scoring systems were evaluated (Agatston, volume, and mass scoring). Good reproducibility in coronary calcium scoring is always the result of a combination of high temporal and spatial resolution; consequently, thin-slice protocols in combination with retrospective gating on MSCT scanners yielded the best results. The Agatston score was found to be the least reproducible scoring method. The hydroxyapatite mass, being better reproducible and comparable on different scanners and being a physical quantitative measure, appears to be the method of choice for future clinical studies. The hydroxyapatite mass is highly correlated to the Agatston score. The introduced phantoms can be used to quantitatively assess the performance characteristics of, for example, different scanners, reconstruction algorithms, and quantification methods in cardiac CT. This is especially important for quantitative tasks, such as the determination of the amount of calcium in the coronary arteries, to achieve high and constant quality in this field. Electronic Publication     

CT扫描所致受检者器官剂量的体模实验研究

目的 了解不同部位X射线CT扫描所致受检者器官或组织的吸收剂量及其分布。方法 实测体模中重要组织器官的CT值,并转换成线性吸收系数与人体正常值进行比较;在体模中 布放光致辐射发光玻璃剂量计,分别模拟测量头部、胸部、腹部和盆腔CT扫描所致受检者主要器官或组织的吸收剂量。结果 实验用仿真人体模具有良好的组织等效性。头部扫描吸收剂量最大的器官是大脑,胸部扫描吸收剂量较大的器官是甲状腺、乳腺、肺和食道,腹部扫描吸收剂量较大的器官是肝、胃、结肠和肺,单次盆腔扫描体所致骨表面和结肠的吸收剂量可达50 mGy以上。结论 X射线CT扫描所致受检者的器官剂量及其分布随扫描部位的不同而异。盆腔扫描时结肠、红骨髓、性腺和膀胱等主要器官的吸收剂量较大,应引起注意。     

Radial cortical and trabecular bone densities of men and women standardized with the European forearm phantom

We previously showed that it is possible to cross-calibrate peripheral bone densitometers using the European Spine Phantom (ESP). We have now performed a multinational study of cross-calibrated radius bone density based on normal subjects of both sexes in eight European centers. Six centers were equipped with machines made by Scanco or Stratec for determining distal radial trabecular bone density by quantitative computed tomography (QCT) and two were equipped with Lunar SP2 single photon absorptiometry (SPA) equipment for measuring midshaft cortical bone density. Subjects recruited ranged from 20 to over 80 years of age. Over one hundred and fifteen men were studied by QCT and a different cohort of 104 men were studied with SPA; the equivalent figures for women were 235 and 123. Reference ranges were derived for bone density against age for each of the four groups, and their applicability is discussed in relation to between-center differences in the results obtained. There were insignificant differences (P>0.05 with Bonferroni correction) between centers in the values obtained by QCT in the different populations. However, there were considerably larger and highly statistically significant differences between midshaft cortical bone density values of about 10% of overall means between subjects from eastern Finland and central Belgium (P<0.001), with higher Finnish values. Women had considerably lower radial trabecular bone density values than men at all ages, a result that differentiates the radius from the spine. This sex difference widened after menopause. These results have important implications for understanding the contribution of bone density to the differential risk of Colles' fracture in the two sexes and suggest that further work is needed to establish young normal reference ranges for radial bone density in Europe.     

Design and Characterisation of a Tissue Phantom System for Optical Diagnostics

We present an optical phantom system especially suited to investigating the generation and transport of laser-induced fluorescence in biological tissues. The phantom system consists of micrometre-sized particles of aluminium oxide, iron and coloured resin dispersed in a solid, transparent host (polyorganosiloxane), from which mechanically stable samples can be made. Mie theory is applied to predict the radiation transport parameters from the optical properties of the isolated components. The predictions are in good agreement with the results of integrating sphere measurements. The radiation transport parameters of the samples are reproducible and temporally stable. Received for publication 4 June 1997; accepted following revision 8 November 1997.     

Phantom design method for high-field MRI human systems.

A phantom design method suitable for high-field MRI based on the RF field wave characteristics of sample and experimental validations at 7.0 T and 3.0 T are presented. The RF field distribution in a phantom with a given RF coil system is primarily determined by the sample size relative to the wavelength inside the sample, and the ratio between the displacement and conduction currents. Experimental results demonstrate that the MR image intensity patterns associated with wave behavior in human samples at a given field strength can be reproduced with a phantom at the same or different field strengths once the dimension and penetration constant are scaled by the corresponding wavelength in the sample medium.     

参考体模和孤立性肺结节CT诊断的初步研究

孤立性肺结节（ＳＰＮ）是放射学常见的诊断难题，笔者应用生物医学工程技术，对参考体模和ＳＰＮＣＴ初步研究结果作报告。我们设计并制成参考体模和参考ＳＰＮ，能对任何密度的ＳＰＮ作为比较标准，评价所有的ＳＰＮ，参考体模用组织等效材料，仿真模拟胸部的解剖并组成四或五层的横断面。参考ＳＰＮ为各种大小的园柱形和不同的密度，应用ＣＴ能获得其生物物理参数（形态、大小、密度、三维座标等）这有利于ＣＴ诊断的质量保证（ＱＡ）和质量控制（ＱＣ）。