Support line and tube visibility in chest examinations using computed radiography

The visibility of support lines and tubes was compared in computed radiography (CR) and screen-film adult chest radiographs. Parameters investigated were radiation dose, image minification, and the use of unsharp mask enhancement. Five radiologists rated the visibility of support lines and tubes on a five-point scale ranging from 1 (entire course of line visible) to 5 (line not visible or only small portion seen). These CR results were compared with the visibility of support lines and tubes as assessed by the same readers for conventional screen-film radiographs (600 speed). Support line and tube visibility improved with image enhancement, image minification, and increasing radiation dose. At the same radiation exposure, support line and tube visibility of the screen-film combination was superior to that of standard CR images. Application of an unsharp mask enhancement algorithm to CR images, however, significantly improved support line and tube visibility in comparison to that obtained with the screen-film combination. It was concluded that unsharp mask processing is a valuable tool for improving the visibility of support lines and tubes in CR chest radiographs.     

Evaluating radiographic parameters for mobile chest computed radiography: phantoms, image quality and effective dose

Conventional chest radiography is technically difficult because of wide variations in tissue attenuations in the chest and limitations of screen-film systems. Mobile chest radiography, performed bedside on hospital inpatients, presents additional difficulties due to geometric and equipment limitations inherent in mobile x-ray procedures and the severity of illness in the patients. Computed radiography (CR) offers a different approach for mobile chest radiography by utilizing a photostimulable phosphor. Photostimulable phosphors overcome some image quality limitations of mobile chest imaging, particularly because of the inherent latitude. Because they are more efficient in absorbing lower-energy x-rays than rare-earth intensifying screens, this study evaluated changes in kVp for improving mobile chest CR. Three commercially available systems were tested, with the goal of implementing the findings clinically. Exposure conditions (kVp and grid use) were assessed with two acrylic-and-aluminum chest phantoms which simulated x-ray attenuation for average-sized and large-sized adult chests. These phantoms contained regions representing the lungs, heart and subdiaphragm to allow proper CR processing. Signal-to-noise ratio (SNR) measurements using different techniques were obtained for acrylic and aluminum disks (1.9 cm diameter) superimposed in the lung and heart regions of the phantoms, where the disk thicknesses (contrast) were determined from disk visibility. Effective doses to the phantoms were also measured for these techniques. The results indicated that using an 8:1, 33 lines/cm antiscatter grid improved the SNR by 60-300 % compared with nongrid images, depending on phantom and region; however, the dose to the phantom also increased by 400-600%. Lowering x-ray tube potential from 80 to 60 kVp improved the SNR by 30-40%, with a corresponding increase in phantom dose of 40-50%. Increasing the potential from 80 to 100 kVp reduced both the SNR and the phantom dose by approximately 10%. The most promising changes in technique for trial in clinical implementation include using an antiscatter grid, especially for large patients, and potentially increasing kVp.     

Diagnostic usefulness of chest computed radiography—Film versus cathode-ray tube images

Seventy-one plain chest images obtained by computed radiography (CR) with an imaging plate were interpreted on film and two kinds of cathode-ray tube (CRT) monitors installed separately at two facilities (1,024 × 1,536 pixels, 8 bits, and 1,024 × 1,280 pixels, 10 bits) by 20 radiologists and four chest internists. The clinical categories of these 71 cases included pulmonary nodules and interstitial abnormalities. Image reading sessions were held over a total of 4 days, ie, 2 days and then another 2 days, 3 weeks later. Twenty-four observers formed four groups with six members each. Two groups read either films or CRT images at one of the two facilities. In the second experiment, 26 of 71 images were compressed at 10∶1, 19 of 71 were compressed at 20∶1, and 26 were not compressed. Analyses of the areas under the receiver-operating characteristic curves showed no significant differences in detection of pulmonary abnormalities between film and CRT. In detecting interstitial pulmonary abnormalities, film was more sensitive than CRT monitor. There were no significant differences in observers’ performances between the two different kinds of CRT workstation. Subjective evaluation of image quality showed that images irreversibly compressed to the ratios of 10∶1 and 20∶1 were inferior to original images. Although further considerations are needed with regard to spatial resolution requirements, image processing, and image compression, the utilization of CR CRT image as a substitute for CR film image will be possible.

     

Evaluation of radiation dose and image quality following changes to tube potential (kVp) in conventional paediatric chest radiography

Purpose

A study of radiation dose and image quality following changes to the tube potential (kVp) in paediatric chest radiography.

Materials and Method

A total of 109 patients ranging from 1 month to 15 years were included in two phases of the study. Phase 1 investigated the range of entrance surface air kerma (ESAK) values received from patients exposed to the existing exposure factors. In the second phase, new exposure factors using recommended values of tube potential (kVp) with reduced mAs were used. ESAK values were measured using thermoluminescent dosemeters (TLDs). Image quality in both phases was evaluated using image quality criteria proposed by the Council of the European Communities (CEC). Results of both techniques were analysed for any differences.

Results

The overall mean ESAK before the changes was 0.22 mGy (range: 0.05-0.43) Following changes in tube potential, the overall mean reduced to 0.15 mGy (range: 0.03-0.38), a significant reduction by 34%. The interquartile range was reduced from 45% to 40%. However, doses to those below a year in age still remained high. Assessment of image quality was found to have no significant differences as far as the two techniques used were concerned. However, higher image scores were achieved using higher kVps.

Conclusion

Significant dose reduction was achieved through appropriate changes in tube potential and reduction of mAs without any loss in image quality.     

工频X线机和中频X线机在胸部计算机X线摄影中应用分析

目的分析工频X线机和中频X线机在胸部计算机X线摄影(CR)中的图像质量,监测相应辐射剂量,比较两种X线机在CR摄影中的适用性。方法使用工频X线机和中频X线机摄取2～3岁小儿胸片共28例,分析图像质量,监测辐射剂量;并对两种X线机高压输出及IP对X线吸收特点进行分析。结果同工频X线机相比,中频X线机更易获得优质图像,且降低了辐射剂量。结论在CR应用中,中频X线机比工频X线机有明显优势。     

简化CR后处理方法提高床旁胸片质量的探讨

目的应用计算机X线摄影（CR）后处理方法,提高床旁胸片图像质量。方法使用FujiCR机,随机选取床旁胸片20例,设定为第1组,调整后处理参数灰阶（GS）和对比度（CS）,测量调整前后同一床旁胸片6个区的密度值,采用统计学方法比较其变化情况：使用Konica CR机．再随机选取床旁胸片20例,设定为第2组,用与第1组相同的方法调整GS和CS．测量调整前后同一床旁胸片6个区的密度值．比较其变化情况。结果调整后第1组5个区的P〈0．01．1个区的P〈0．05。第2组5个区的P〉0．05．1个区的P〈0．05。图像密度和CS增加．图像质量提高。结论应用CR后处理．调整后处理参数GS和CS．可以提高图像质量。     

A-Si:H/CsI(Tl) flat-panel versus computed radiography for chest imaging applications: image quality metrics measurement

Amorphous silicon (a-Si:H) flat-panel (FP) imaging systems have recently become commercially available for both chest and mammographic imaging applications. It has been shown that this new detector technology offers better image quality and various operational advantages over the computed radiography (CR) which to date has been the most widely implemented and used digital radiography technique. However, most image quality measurements reported on flat-panel systems have been performed on prototype systems in laboratories while those for CR systems were typically independently performed and reported on in separate studies. To directly compare the two technologies, we have measured the image properties for a commercial amorphous silicon/cesium iodide [a-Si:H/CsI(Tl)] flat-panel based digital chest system and a commercial CR system under clinical imaging conditions. In this paper, measurements of image quality metrics, including the modulation transfer functions (MTFs), noise power spectra (NPSs), and detective quantum efficiencies (DQEs), for the FP and CR systems are presented and compared. Methods and issues related to these measurements are discussed. The results show that the flat-panel system has slightly lower MTF but significantly higher DQEs than the CR system. The DQEs of the flat-panel system were found to increase with the exposure while those of the CR system decrease slightly with the exposure.     

婴幼儿胸部DR摄影源像距与辐射剂量和图像质量的相关性研究

目的 探讨婴幼儿胸部数字X射线摄影(DR)的源像距(SID)与图像质量及辐射剂量的相关性.方法 先进行仿真胸部体模(成都剂量体模)实验性曝光,采用同一管电压(65 kVp)和不同SID进行曝光组合,记录每次曝光的毫安秒(mAs)、单位面积剂量:在实验的基础上进行婴幼儿胸部DR,收集2008年5月～2010年5月初次人院的50例婴幼儿行胸部DR(其中男性28例,女性22例;年龄5个月～2岁,平均年龄10个月),住院期间复查1次作为对照,初检组均使用110cmSID,复检组均使用90cmSID进行DR胸部摄影.由3名资深影像学专家对获取的100幅图像质最进行评判,评判结果运用统计学软件SPSS 13.0进行分析,使用接受者操作特征曲线(ROC)分析和t检验.结果 100例初检及复查婴幼儿的图像质量均符合诊断要求(P>0.05);而不同的SID曝光的面积剂量差异有统计学意义(P<0.05).结论 婴幼儿胸部DR的不同SID,其辐射剂量差异具有统计学意义,且图像质量均能满足诊断要求,90cmSID在婴幼儿胸部DR中值得提倡.     

肺移植后患者传统屏-片与计算机数字化系统床边胸片的质量对比

背景：肺移植后患者床边胸片的质量关系到对肺部病变的评价,对临床具有十分重要的价值。 目的：比较肺移植后患者应用传统屏-片组合和计算机数字化系统进行床边胸部摄片的图像质量,以选择优良方案。 方法：回顾性分析南京医科大学附属无锡市人民医院78例肺移植后患者床边胸片传统屏-片摄影425张和计算机数字化摄影411张的图像资料,提出优质片评估标准,经3位高年资医师、技师读片将其从优质片到废片分为Ⅰ~Ⅳ级,然后分析影响两组床边胸片质量的因素,并计算两组的平均曝光剂量。 结果与结论：肺移植后患者床边胸片,传统屏-片组：Ⅰ级片135张(31.8%)、Ⅱ级片171张(40.2%)、Ⅲ级片107张(25.2%)、Ⅳ级片12张(2.8%);计算机数字化摄影组：Ⅰ级片266张(64.7%)、Ⅱ级片105张(25.5%)、Ⅲ级片37张(9.0%)、Ⅳ级片3张(0.7%),两组床边胸片图像质量分级差异有非常显著性意义(P  < 0.01)。计算机数字化摄影组平均曝光剂量1.56 mA•s明显小于屏-片组3.27 mA•s(P < 0.01)。提示肺移植后患者计算机数字化摄影系统床边胸片质量明显优于传统屏-片组合床边胸片,应用计算机数字化摄影系统可提高优质片,减少废片,降低X射线照射剂量,可作为肺移植后患者床边胸片的首选。     

Comparison of dual and single exposure techniques in dual-energy chest radiography

Conventional chest radiography is the most effective tool for lung cancer detection and diagnosis; nevertheless, a high percentage of lung cancer tumors are missed because of the overlap of lung nodule image contrast with bone image contrast in a chest radiograph. Two different energy subtraction strategies, dual exposure and single exposure techniques, were studied for decomposing a radiograph into bone-free and soft tissue-free images to address this problem. For comparing the efficiency of these two techniques in lung nodule detection, the performances of the techniques were evaluated on the basis of residual tissue contrast, energy separation, and signal-to-noise ratio. The evaluation was based on both computer simulation and experimental verification. The dual exposure technique was found to be better than the single exposure technique because of its higher signal-to-noise ratio and greater residual tissue contrast. However, x-ray tube loading and patient motion are problems.     

Comparison of an amorphous silicon/cesium iodide flat-panel digital chest radiography system with screen/film and computed radiography systems--a contrast-detail phantom study.

Flat-panel (FP) based digital radiography systems have recently been introduced as a new and improved digital radiography technology; it is important to evaluate and compare this new technology with currently widely used conventional screen/film (SF) and computed radiography (CR) techniques. In this study, the low-contrast performance of an amorphous silicon/cesium iodide (aSi/Csl)-based flat-panel digital chest radiography system is compared to those of a screen/film and a computed radiography system by measuring their contrast-detail curves. Also studied were the effects of image enhancement in printing the digital images and dependence on kVp and incident exposure. It was found that the FP system demonstrated significantly better low-contrast performance than the SF or CR systems. It was estimated that a dose savings of 70%-90% could be achieved to match the low-contrast performance of the FP images to that of the SF images. This dose saving was also found to increase with the object size. No significant difference was observed in low-contrast performances between the SF and CR systems. The use of clinical enhancement protocols for printing digital images was found to be essential and result in better low-contrast performance. No significant effects were observed for different kVps. From the results of this contrast-detail phantom study, the aSi/CsI-based flat-panel digital chest system should perform better under clinical situations for detection of low-contrast objects such as lung nodules. However, proper processing prior to printing would be essential to realizing this better performance.     

影响DR图像质量因素分析

目的研究影响DR图像质量因素和规避。方法通过DR成像系统成像后,经工作站后处理,调整至最佳传至激光相机打片。选取600幅照片,其中男性326例,女性274例;年龄2天～78岁,平均年龄45岁。照片所摄部位以胸片、脊柱片、四肢骨和关节片为主,通过X射线评片标准,对其质量进行评价,探讨影响成像质量因素。结果甲级片498张,非甲级片102张。通过着重对非甲级片分析,影响DR图像质量因素如下。①技术人员的操作技能和业务技术水平。此原因所致68张,占66%。②摄片技术参数。此原因所致23张,占23%。③机器性能。此原因所致3张,占3%。④图像后处理技术。此原因所致6张,占6%。⑤激光相机。此原因所致2张,占2%。结论影响DR照片质量因素很多,技术人员的操作技能和水平是其主要因素。应用DR设备过程中,只有不断提高技术人员的综合素质水平,规范操作和不断总结使用经验,增强对设备原理的学习,探索更多临床经验,才能得到质量更佳图像照片。     

Comparison of the quality of temporal subtraction images obtained with manual and automated methods of digital chest radiography

The authors have been developing a fully automated temporal subtraction scheme to assist radiologists in the detection of interval changes in digital chest radiographs. The temporal subtraction image is obtained by subtraction of a previous image from a current image. The authors' automated method includes not only image shift and rotation techniques but also a nonlinear geometric warping technique for reduction of misregistration artifacts in the subtraction image. However, a manual subtraction method that can be carried out only with image shift and rotation has been employed as a common clinical technique in angiography, and it might be clinically acceptable for detection of interval changes on chest radiographs as well. Therefore, the authors applied both the manual and automated temporal subtraction techniques to 181 digital chest radiographs, and compared the quality of the subtraction images obtained with the two methods. The numbers of clinically acceptable subtraction images were 147 (81.2%) and 176 (97.2%) for the manual and automated subtraction methods, respectively. The image quality of 148 (81.8%) subtraction images was improved by use of the automated method in comparison with the subtraction images obtained with the manual method. These results indicate that the automated method with the nonlinear warping technique can significantly reduce misregistration artifacts in comparison with the manual method. Therefore, the authors believe that the automated subtraction method is more useful for the detection of interval changes in digital chest radiographs.     

Comparison of imaging properties of a computed radiography system and screen-film systems

To compare the diagnostic quality of images obtained with a computed radiography (CR) system based on storage phosphor technology with that obtained with conventional screen-film systems, a dual-image recording technique was devised. With this technique, a CR imaging plate is placed behind a screen-film system in a conventional cassette. This makes it possible to obtain two images simultaneously, one from each system, in a clinical examination with the same patient positioning, the same degree of patient motion, the same geometric unsharpness, and no additional exposure. The modulation transfer functions (MTFs) of the CR system with and without the dual-image recording technique were greater at low frequencies, but lower at high frequencies, that the MTFs of the screen-film systems used. The noise Wiener spectra of the CR images at the plane of the imaging plate were greater than those of the screen-film systems, but were comparable to those of the screen-film systems at the plane of the printed film due to the reduction in image size. Clinical chest images obtained with the dual-image recording technique appeared comparable, probably because of the image size reduction and the use of mild unsharp mask processing.     

Comparison of radiographic texture analysis from computed radiography and bone densitometry systems

Osteoporosis is a disease that results in an increased risk of bone fracture due to a loss of bone mass and deterioration of bone structure. Bone mineral density (BMD) provides a measure of bone mass and is frequently measured by bone densitometry systems to diagnose osteoporosis. In addition, computerized radiographic texture analysis (RTA) is currently being investigated as a measure of bone structure and as an additional diagnostic predictor of osteoporosis. In this study, we assessed the ability of a peripheral bone densitometry (PD) system to yield images useful for RTA. The benefit of such a system is that it measures BMD by dual-energy x-ray absorptiometry and therefore provides high- and low-energy digital radiographic images. The bone densitometry system investigated was the GE/Lunar PIXI, which provides 512 x 512 digital images of the heel or forearm (0.2 mm pixels). We compared texture features of heel images obtained with this PD system to those obtained on a Fuji computed radiography (CR) system (0.1 mm pixels). Fourier and fractal-based texture features of images from 24 subjects who had both CR and BMD exams were calculated, and correlation between the two systems was analyzed. Fourier-based texture features characterize the magnitude, frequency content, and orientation of the trabecular bone pattern. Good correlation was found between the two modalities for the first moment (FMP) with r=0.71 (p value<0.0001) and for minimum FMP with r=0.52 (p value=0.008). Root-mean-square (RMS) did not correlate with r=0.31 (p value>0.05), while the standard deviation of the RMS did correlate with r=0.79 (p value<0.0001). Good correlation was also found between the two modalities for the fractal-based texture features with r=0.79 (p value<0.0001) for the global Minkowski dimension and r=0.63 (p value=0.0007) for the fractal dimension from a box counting method. The PD system therefore may have the potential for yielding heel images suitable for RTA.     

A cost-analysis of computed radiography and picture archiving and communication systems in portable radiography

A total of 40,000 portable examinations are performed each year at Shands Hospital (Gainesville, FL), a 570-bed teaching hospital. Radiographs are obtained using a screen-film combination with the films digitized for transmission to displays in four intensive care units. A cost-analysis of replacing screen-film with computed radiography (CR) integrated into a filmless picture archiving and communication system (PACS) network was performed. Equipment requirements included two CR units, three high-resolution dual monitor displays, and an archive to store 3 months of image data. The capital costs were amortized over a 5-year period. Capital and operating costs of the proposed expansion to the existing PACS network, together with anticipated cost savings, were determined. The maximum data transfer rate for portable examinations was 150 MByte per hour and approximately 400 GByte of image data are generated each year. These figures were used to determine hhe hardware requirements for handling the acquisition, transfer, and display of the images. Annual costs of the proposed expansion were about $220,000. Cost savings were achieved by elimination of film, including its handling by technologists/library clerks, and amounted to about $200,000 per year.     

Effect of different cold application materials on pain during chest tube removal: three-arm randomized controlled clinical trial

BackgroundChest tube causes severe pain during removal because it attaches to the endothelium in the chest cavity.ObjectivesThis study aimed to determine the effectiveness of cold application with ice pack and gel pad in the control of pain experienced during chest tube removal.MethodsThe sample of prospective, parallel three-arm (1:1:1), randomized controlled clinical trial consisted of 180 patients in two experimental groups (ice pack/gel pad) and one control group. The primary outcome was effect of cold application materials on severity of pain during chest removal. Secondary outcomes were duration of cold application and analgesic requirements of the patients.ResultsThe study found that the cold application using either of the materials reduced the severity of pain and the need for analgesics after the removal of chest tube compared to the control group (p<0.05). But cold application with ice pack allowed the skin to drop to the temperature effective in pain control in a shorter time than gel pad application (p<0.05).ConclusionsDespite entirely covering the area around the chest tube, the gel pad was more disadvantageous than ice pack in pain control due to the longer duration of cold application.     

Digital chest radiography at the University of Chicago: Present status and future plans

Storage-phosphor computed radiography and film digitization systems have been in routine clinical use at the University of Chicago for several years. During this time we have implemented numerous modifications including techniques for scatter reduction, image processing enhancements and display systems to improve the image quality and utility of these devices. We have also evaluated the image quality and functionality of digital systems relative to conventional screen-film radiography. In this paper, we review our experience and summarize our impressions. In addition, we summarize our plans for a rapid transition into picture archiving and communication systems, with hardcopy interpretation being phased out for most modalities over the next 2 to 5 years.     

Assessment of the effects of pixel loss on image quality in direct digital radiography

Modern digital radiographic 'flat panel' detectors can exhibit a progressive form of image degradation arising from non-functioning pixels. The effect of these 'dead pixels' on the quantitive image quality measures of modulation transfer function (MTF), noise power spectrum (NPS) and detective quantum efficiency (DQE) is investigated by a simulated degradation of images obtained from an Hologic EPEX system. The effects on the semi-quantitive measures obtained from contrast threshold test objects and resolution gratings are also investigated. Results suggest that the contrast-detail tests often employed in quality assurance measures are not sufficient to reveal the presence of dead pixels until well beyond the recommended replacement point for the flat panel detector. However, measurements of spatial resolution using a line pairs phantom were found to be more sensitive to pixel loss. Measurement of the MTF, NPS and DQE can reveal small changes in image quality with increasing pixel loss, with a distinctive pattern in the trend of the NPS.