A Technique for Simulating the Effect of Dose Reduction on Image Quality in Digital Chest Radiography

Purpose: The purpose of this study is to provide a pragmatic tool for studying the relationship between dose and image quality in clinical chest images. To achieve this, we developed a technique for simulating the effect of dose reduction on image quality of digital chest images. Materials and Methods: The technique was developed for a digital charge-coupled-device (CCD) chest unit with slot-scan acquisition. Raw pixel values were scaled to a lower dose level, and a random number representing noise to each specific pixel value was added. After adding noise, raw images were post processed in the standard way. Validation was performed by comparing pixel standard deviation, as a measure of noise, in simulated images with images acquired at actual lower doses. To achieve this, a uniform test object and an anthropomorphic phantom were used. Additionally, noise power spectra of simulated and actual images were compared. Also, detectability of simulated lesions was investigated using a model observer. Results: The mean difference in noise values between simulated and real lower-dose phantom images was smaller than 5% for relevant clinical settings. Noise power spectra appeared to be comparable on average but simulated images showed slightly higher noise levels for higher spatial frequencies and slightly lower noise levels for lower spatial frequencies. Comparable detection performance was shown in simulated and actual images with slightly worse detectability for simulated lower dose images. Conclusion: We have developed and validated a method for simulating dose reduction. Our method seems an acceptable pragmatic tool for studying the relationship between dose and image quality.     

Optimising the Use of Computed Radiography in Pediatric Chest Imaging

The objective of this study was to analyze image quality of chest examinations in pediatric patients using computed radiography (CR) obtained with a wide range of doses to suggest the appropriate parameters for optimal image quality. A sample of 240 chest images in four age ranges was randomly selected from the examinations performed during 2004. Images were obtained using a CR system and were evaluated independently by three radiologists. Each image was scored using criteria proposed by the European Guidelines on Quality Criteria in Pediatrics. Mean global scoring and scoring of individual criteria more sensitive to noise were used to evaluate image quality. Agfa dose level (DL) was in the range 1.20 to 2.85. It was found that there was not significant correlation (R < 0.5) between image quality and DL for any of the age ranges for either global score or for individual criteria more related to noise. The mean value of DL was in the ranges 1.9–2.1 for the four age bands. From this study, a DL value of 1.6 is proposed for pediatric CR chest imaging. This could yield a reduction of approximately a factor of 2.5 in mean patient entrance surface doses.     

高千伏胸部摄影在DR系统的应用

目的：探讨DR高千伏胸部摄影的条件，评价DR胸部影像。方法：①选择5种体型人体（特瘦、瘦、中等、胖、特胖）各10人，将KV固定为125KV，按7种不同档次的mAs进行正侧位投照。②选取最佳成像的摄影条件，按此条件对1000例患者进行摄影。③对1000例DR胸部影像进行质量评定。结果：①高千伏投照5种体型最佳成像的mAs范围，正位2．0－6．4mAs，侧位4．0－10．0mAs。②1000例DR胸部影像甲级片占50．6％，乙级片占38．5％，丙级片占10．9％，无废片影像。结论：高千伏DR胸部摄影可代替高千伏屏－胶胸部摄影，并具有更多的优越性。     

Study of Automatic Enhancement for Chest Radiograph

Because of the large difference of the densities in the lung and other structures, the chest x-ray image behaves as a wide-range intensity distribution, which brings on a bit of difficulty to investigate the focus. In the paper, according to the intensity properties of the chest radiograph, the chest radiographic image is divided into three subregions, and a piecewise linear transformation model is established. An approach of automatic enhancement is presented, based on the gray-level normalization. The average enhanced ratios of three subregions of the normal and severe acute respiratory syndrome image are increased by 10.70% and 25.55%, respectively. The technique is proved to be effective through the evaluation of the improved images.     

胸片计算机辅助检测的研究进展

随着医学影像数字化的发展,对影像的智能化理解成为一种必然趋势,计算机辅助检测（computer-aided detection,CAD）系统已经成为了医学影像学研究的热点之一,并逐步进入了医学临床应用,这对于提高诊断准确率、减少漏诊有着非常积极的作用。文章在介绍CAD系统基本概念的基础上,重点阐述了CAD系统在胸片疾病诊断中的基本工作流程,包括病灶区域增强、肺区分割、可疑区域选择、病灶筛选和病灶特征的进一步分析,以及CAD系统在肺部结节检测、肺间质性病变检测、利用时间减影检测间期病理变化等方面的应用,并讨论了其发展趋势。     

Computer-Aided Nodule Detection on Digital Chest Radiography: Validation Test on Consecutive T1 Cases of Resectable Lung Cancer

Purpose To evaluate the usefulness of a commercially available computer-assisted diagnosis (CAD) system on operable T1 cases of lung cancer by use of digital chest radiography equipment. Materials and Methods Fifty consecutive patients underwent surgery for primary lung cancer, and 50 normal cases were selected. All cancer cases were histopathologically confirmed T1 cases. All normal individuals were selected on the basis of chest computed tomography (CT) confirmation and were matched with cancer cases in terms of age and gender distributions. All chest radiographs were obtained with one computed radiography or two flat-panel detector systems. Eight radiologists (four chest radiologists and four residents) participated in observer tests and interpreted soft copy images by using an exclusive display system without and with CAD output. When radiologists diagnosed cases as positives, the locations of lesions were recorded on hard copies. The observers’ performance was evaluated by receiver operating characteristic analysis. Results The overall detectability of lung cancer cases with CAD system was 74% (37/50), and the false-positive rate was 2.28 (114/50) false positives per case for normal cases. The mean A_z value increased significantly from 0.896 without CAD output to 0.923 with CAD output (P = 0.018). The main cause of the improvement in performance is attributable to changes from false negatives without CAD to true positives with CAD (19/31, 61%). Moreover, improvement in the location of the tumor was observed in 1.5 cases, on average, for radiology residents. Conclusion This CAD system for digital chest radiographs is useful in assisting radiologists in the detection of early resectable lung cancer.     

Incorporation of a Laguerre–Gauss Channelized Hotelling Observer for False-Positive Reduction in a Mammographic Mass CAD System

Previously, we developed a simple Laguerre-Gauss (LG) channelized Hotelling observer (CHO) for incorporation into our mass computer-aided detection (CAD) system. This LG-CHO was trained using initial detection suspicious region data and was empirically optimized for free parameters. For the study presented in this paper, we wish to create a more optimal mass detection observer based on a novel combination of LG channels. A large set of LG channels with differing free parameters was created. Each of these channels was applied to the suspicious regions, and an output test statistic was determined. A stepwise feature selection algorithm was used to determine which LG channels would combine best to detect masses. These channels were combined using a HO to create a single template for the mass CAD system. Results from free-response receiver operating characteristic curves demonstrated that the incorporation of the novel LG-CHO into the CAD system slightly improved performance in high-sensitivity regions.     

Information Entropy Measure for Evaluation of Image Quality

This paper presents a simple and straightforward method for synthetically evaluating digital radiographic images by a single parameter in terms of transmitted information (TI). The features of our proposed method are (1) simplicity of computation, (2) simplicity of experimentation, and (3) combined assessment of image noise and resolution (blur). Two acrylic step wedges with 0–1–2–3–4–5 and 0–2–4–6–8–10 mm in thickness were used as phantoms for experiments. In the present study, three experiments were conducted. First, to investigate the relation between the value of TI and image noise, various radiation doses by changing exposure time were employed. Second, we examined the relation between the value of TI and image blurring by shifting the phantoms away from the center of the X-ray beam area toward the cathode end when imaging was performed. Third, we analyzed the combined effect of deteriorated blur and noise on the images by employing three smoothing filters. Experimental results show that the amount of TI is closely related to both image noise and image blurring. The results demonstrate the usefulness of our method for evaluation of physical image quality in medical imaging.     

Evaluation of the Image Quality of Temporal Subtraction Images Produced Automatically in a PACS Environment

The aim of the study is to evaluate the reliable production of temporal subtraction images in a picture archiving and communication system environment and to establish objective criteria for the evaluation of image quality. A total of 117 temporal subtraction chest images (55 in the upright position, 62 in the supine position) were obtained in five consecutive days. In all of these, we confirmed that there were no interval changes on the original images, and cases with diffuse lung disease were excluded. The temporal subtraction images were classified by three chest radiologists into five levels: 5, excellent; 4, good; 3, acceptable; 2, poor; and 1, very poor. The following were examined: (1) the yield of adequate quality of the temporal subtraction images; (2) whether the temporal subtraction images were obtained in the warping or nonwarping mode; and (3) the correlation of the overall subjective image quality with the relative shift angles, relative shift distances, and the standard deviation of gray levels in the temporal subtraction images. The percentages of acceptable temporal subtraction images were 100% and 66% in the upright and supine positions, respectively. Sixteen (26%) of the 62 supine-position images were made in nonwarping mode, whereas all upright images were made in warping mode. Significant correlations were obtained in the relative shift angle (P < 0.05), relative horizontal shift distance (P < 0.05), and standard deviation of gray levels (P < 0.0001). Temporal subtraction images with acceptable image quality were obtained in the upright position. The objective criteria may be useful for the evaluation of image quality.     

An Experimental Comparison of Flat-Panel Detector Performance for Direct and Indirect Systems (Initial Experiences and Physical Evaluation)

The purpose of this work was to compare direct and indirect detectors in terms of their system linearity, presampled modulation transfer function (MTF), Wiener spectrum (WS), noise equivalent quanta (NEQ), and power spectrum. Measurements were made on two flat-panel detectors, GE Revolution XR/d (indirect) and Shimadzu Safire (direct) radiographic techniques. The system linearity of the systems was measured using a time-scale method. The MTF of the systems was measured using an edge method. The WS of the systems was determined for a variable range of exposure levels by two-dimensional Fourier analysis. The NEQ was assessed from the measured MTF, WS, and estimated ideal signal-to-noise ratios. Power spectrum analyzed the chest phantom within artificial lesions. System linearity was excellent for the direct systems. For the direct system, the MTF was found to be significantly higher than that for the indirect systems. For the direct system, the WS was relatively uniform across all frequencies. In comparison, the indirect system exhibited a drop in the WS at high frequencies. At lower frequencies, the NEQ for the indirect system was noticeably higher than for the direct system. Power spectrum for the direct system was relatively flat and similar to that for white noise. The indirect system exhibited significant reduction at high spatial frequencies. In general, the direct systems exhibit improved image quality over indirect systems at comparable exposure dose.     

Automatic noise robust registration of radiographs for subtraction using strategic local correlation: an application to radiographs of dental implants

Most of digital subtraction methods in dental radiography are based on registration using manual landmarks. We have developed an automatic registration method without using the manual selection of landmarks. By restricting a geometrical matching of images to a region of interest (ROI), we compare the cross-correlation coefficient only between the ROIs. The affine or perspective transform parameters satisfying maximum of cross-correlation between the local regions are searched iteratively by a fast searching strategy. The parameters are searched on the 14 scale image coarsely and then, the fine registration is performed on the original scale image. The developed method can match the images corrupted by Gaussian noise with the same accuracy for the images without any transform simulation. The registration accuracy of the perspective method shows a 17% improvement over the manual method. The application of the developed method to radiographs of dental implants provides an automatic noise robust registration with high accuracy in almost real time.     

A novel real-time noise reduction system for the assessment of evoked otoacoustic emissions

A novel noise reduction method and apparatus to be used in connection with the measurement of evoked otoacoustic emissions (EOAE) are presented. The noise reduction method is based on an adaptive noise canceller and requires a noise-only reference microphone placed in the vicinity of the OAE-probe. The method was implemented in real time on a custom built digital signal processing system using an Analog Devices ADSP-2181 digital signal processor. The system interfaces seamlessly with a commercial EOAE acquisition system. Results of a series of experiments show than noise reductions of 7–8 dB can be reached.     

Development and Evaluation of a Head-Controlled Human-Computer Interface with Mouse-Like Functions for Physically Disabled Users

OBJECTIVES

The objectives of this study were to develop a pointing device controlled by head movement that had the same functions as a conventional mouse and to evaluate the performance of the proposed device when operated by quadriplegic users.

METHODS

Ten individuals with cervical spinal cord injury participated in functional evaluations of the developed pointing device. The device consisted of a video camera, computer software, and a target attached to the front part of a cap, which was placed on the user’s head. The software captured images of the target coming from the video camera and processed them with the aim of determining the displacement from the center of the target and correlating this with the movement of the computer cursor. Evaluation of the interaction between each user and the proposed device was carried out using 24 multidirectional tests with two degrees of difficulty.

RESULTS

According to the parameters of mean throughput and movement time, no statistically significant differences were observed between the repetitions of the tests for either of the studied levels of difficulty.

CONCLUSIONS

The developed pointing device adequately emulates the movement functions of the computer cursor. It is easy to use and can be learned quickly when operated by quadriplegic individuals.     

针刺联合五步复位法治疗游泳运动员椎间盘突出的临床效果评价

目的 探讨针刺联合五步复位法治疗椎间盘突出的临床效果。方法 选取符合条件要求的80例腰椎盘突出患者，将其随机分为对照组、针刺组、五步复位推拿组、针刺联合五步复位法组，每组20人，各治疗两个疗程，共1个月。治疗完毕后，评价针刺、五步复位推拿及针刺联合五步复位推拿治疗效果。观察指标包括腰痛JOA量表、McGill疼痛量表、生活质量QOL量表、重力矩和肌肉矩。结果 干预治疗后，与对照组相比，针刺组、五步复位推拿组、针刺联合五步复位推拿组患者JOA、McGill、QOL、重力矩和肌肉矩均有显著改善（P＜0.05），且联合治疗组改善效果更为显著（P＜0.01）。结论 针刺联合五步复位法显著改善游泳运动员腰椎盘突出的症状。     

Evaluation of the use of digital images for a national prostate core external quality assurance scheme

Harnden P, Coleman D, Moss S, Kodikara S, Griffin N R & Melia J

(2011) Histopathology 59 , 703–709 Evaluation of the use of digital images for a national prostate core external quality assurance scheme Aims: To evaluate the use of virtual images as an alternative to glass slides to expand the number of participants in the External Quality Assurance Scheme for prostatic biopsies. Methods and results: Benign and neoplastic cases, previously circulated as glass slides, were selected to include cases that had demonstrated a high level of agreement (n = 10) and a lesser degree of agreement (n = 10). Whole slide virtual images were circulated to 68 pathologists; 51 responses were returned. The levels of agreement for the primary diagnosis and for Gleason grading of cancers were analysed using kappa statistics. Responses for glass slides versus images were compared for the 24 pathologists for whom data were available. Levels of agreement for diagnostic categories using virtual slides were moderate to substantial, comparable to those found using glass slides. The level of agreement for Gleason grades 8–10 was substantial, but for lower grades was fair or moderate, poorer than for the glass slide circulation. Conclusions: Circulation of virtual images of biopsy material is a suitable alternative to glass slide‐based schemes for the evaluation of diagnostic consistency. The majority of participants agreed that the ability to evaluate limited diagnostic material outweighed the disadvantages of a virtual system.     

应用无垂直瘢痕的下蒂瓣巨乳缩小术体会

目的探讨如何更好地运用无垂直瘢痕的下蒂瓣巨乳缩小术,重点讨论了如何解决新乳房下部皮肤不足、保存术后乳头乳晕感觉及术后乳房潜在的泌乳功能。方法通过①提高乳房返折处皮肤切口(高于乳房下皱襞线1.5cm～2cm),利用部分原乳房下部皮肤来补足新乳房下部皮肤不足的情况。②所有患者的下蒂瓣均制作成真皮-脂肪-乳腺复合瓣,蒂宽不小于12cm,该复合瓣由浅入深逐渐增宽,并保持与胸大肌附着。结果所有8例患者的16只巨乳术后切口均一期愈合。5例于术后6个月到2年时获得随访,乳房外形满意,乳头乳晕感觉正常,乳房表面瘢痕少而隐蔽。结论(1)当设计乳晕下缘与原乳晕上缘间距过短(不足4cm)时,可通过提高乳房返折处皮肤切口(高于乳房下皱襞线1～2cm)保留部分原乳房下部皮肤来补足新乳房下部皮肤不足的情况。(2)与胸大肌附着的真皮-脂肪-乳腺复合瓣有助于保存术后乳头乳晕的感觉及潜在的泌乳功能。     

数字化乳腺成像系统量子探测效率检测方法研究

数字化乳腺X线摄影技术已成为临床检测早期无症状隐匿性乳腺癌的重要手段,在此背景下,评价数字乳腺机性能的量子探测效率(DQE)检测方法,是国内外临床医学界和医学影像检测部门所关注的重要课题。针对相对成熟的IEC62220-1标准不适用于辐射剂量小、辐射野小的数字乳腺机DQE检测的问题,本文较深入地研究了基于IEC62220-1-2标准的数字乳腺机DQE检测方法和具体数字图像处理算法的实现。并将该DQE检测手段实施于辽宁省医疗器械检验所受检产品某公司生产的乳腺机,得到了相应的DQE测试结果,最后,本文讨论了数字化乳腺成像系统量子探测效率的重要影响因素。     

关于基于可扩展PACS的医学影像处理科研教学实验室建设的设想

目的：提出了在高校医学影像工程专业建设一个先进的医学影像处理科研教学实验室的设想，以促进医、工、教、研的结合，并方便医学图像处理科研、教学乃至产业化。方法：首先建立基于可扩展PACS系统的研究平台，并在此基础上构建可扩展影像数据库和相关软硬件技术研发平台．逐步形成实验室科研教学所需要的硬环境，同时建立必要的管理制度、项目培育和激励机制以及研究生和优秀本科生能力培养机制等软环境．然后随着实验室与医院和产业界合作程度的加深以及学生毕业后走向社会的“滚动式”的反馈和影响，使得实验室的运作逐步形成良性循环和长效机制。结果：建立这样的实验室不但会方便科研、教学，还可紧扣医院的临床需求把医学影像产品的研发与产业化密切联系在一起，能够形成一个医、工、教、研交叉融合的良好平台和媒介。结论：充分体现卓越工程师教育的新思想和理念，通过不断增强实验室基础职能及其平台和媒介作用，可逐步形成一种范式。可以预见该类实验室建设和良性运作必将同时受到实验室师生、医院相关医生和产业界涉众的欢迎和支持。其对产学研密切结合的教研模式的研究不失为一种有益的试验和探索。     

Effects of a Web-Based Intervention for Stress Reduction in Primary Care: A Cluster Randomized Controlled Trial

Background

Preliminary findings suggest that Web-based interventions may be effective in achieving significant stress reduction. To date, there are no findings available for primary care patients. This is the first study that investigates a Web-based intervention for stress reduction in primary care.

Objective

The aim was to examine the short-term effectiveness of a fully automated Web-based coaching program regarding stress reduction in a primary care setting.

Methods

The study was an unblinded cluster randomized trial with an observation period of 12 weeks. Individuals recruited by general practitioners randomized to the intervention group participated in a Web-based coaching program based on education, motivation, exercise guidance, daily text message reminders, and weekly feedback through the Internet. All components of the program were fully automated. Participants in the control group received usual care and advice from their practitioner without the Web-based coaching program. The main outcome was change in the Perceived Stress Questionnaire (PSQ) over 12 weeks.

Results

A total of 93 participants (40 in intervention group, 53 in control group) were recruited into the study. For 25 participants from the intervention group and 49 participants from the control group, PSQ scores at baseline and 12 weeks were available. In the intention-to-treat analysis, the PSQ score decreased by mean 8.2 (SD 12.7) in the intervention group and by mean 12.6 (SD 14.7) in the control group. There was no significant difference identified between the groups (mean difference –4.5, 95% CI –10.2 to 1.3, P=.13).

Conclusions

This trial could not show that the tested Web-based intervention was effective for reducing stress compared to usual care. The limited statistical power and the high dropout rate may have reduced the study’s ability to detect significant differences between the groups. Further randomized controlled trials are needed with larger populations to investigate the long-term outcome as well as the contents of usual primary care.

Trial Registration

German Clinical Trials Register DRKS00003067; http://drks-neu.uniklinik-freiburg.de/drks_web/navigate.do?=DRKS00003067 (Archived by WebCite at http://www.webcitation.org/6eXk0PXmO)     

Evaluation of a Web-Based Food Record for Children Using Direct Unobtrusive Lunch Observations: A Validation Study

Background

High-quality, Web-based dietary assessment tools for children are needed to reduce cost and improve user-friendliness when studying children’s dietary practices.

Objective

To evaluate the first Web-based dietary assessment tool for children in Norway, the Web-based Food Record (WebFR), by comparing children’s true school lunch intake with recordings in the WebFR, using direct unobtrusive observation as the reference method.

Methods

A total of 117 children, 8-9 years, from Bærum, Norway, were recruited from September to December 2013. Children completed 4 days of recordings in the WebFR, with parental assistance, and were observed during school lunch in the same period by 3 observers. Interobserver reliability assessments were satisfactory. Match, omission, and intrusion rates were calculated to assess the quality of the recordings in the WebFR for different food categories, and for all foods combined. Logistic regression analyses were used to investigate whether body mass index (BMI), parental educational level, parental ethnicity or family structure were associated with having a “low match rate” (≤70%).

Results

Bread and milk were recorded with less bias than spreads, fruits, and vegetables. Mean (SD) for match, omission, and intrusion rates for all foods combined were 73% (27%), 27% (27%), and 19% (26%), respectively. Match rates were statistically significantly associated with parental educational level (low education 52% [32%] versus high 77% [24%], P=.008) and parental ethnicity (non-Norwegian 57% [28%] versus others 75% [26%], P=.04). Only parental ethnicity remained statistically significant in the logistic regression model, showing an adjusted odds ratio of 6.9 and a 95% confidence interval between 1.3 and 36.4.

Conclusions

Compared with other similar studies, our results indicate that the WebFR is in line with, or better than most of other similar tools, yet enhancements could further improve the WebFR.