A comparison of low contrast performance for amorphous Silicon/caesium iodide direct radiography with a computed radiography: A contrast detail phantom study

A range of digital image acquisition devices exists in diagnostic radiology. This study compares contrast performance of two such systems: an amorphous Silicon/caesium iodide (a-Si:CsI) based flat panel (DR) digital chest radiography system and a computed radiography (CR) system. Images of a contrast detail resolution phantom were acquired at a range of radiation doses. Three observers assessed all hardcopy images using a four-alternative forced choice observer perception technique. Contrast detail performance was calculated and low contrast performance quantified.The DR system demonstrated significantly better low contrast performance and potential dose savings of up to 75% compared to the CR system. Threshold levels of contrast detail resolution were defined and levels of under- and over-exposure, compared to the threshold level, were highlighted. Both systems were noise limited at lower exposures and latitude limited at higher exposures. The results demonstrate that the DR system should perform better than the CR system under typical clinical conditions relevant to chest radiography particularly for the detection of low contrast details such as lung metastases or pneumothoraces.     

Root fracture detection: a comparison of direct digital radiography with conventional radiography

OBJECTIVES: To compare the diagnostic potential of direct digital radiography with conventional film for detecting experimental root fractures. METHODS: Two hundred and one extracted single-rooted human teeth were endodontically instrumented and divided into two groups, a control group of 100 teeth and a fractured group of 101 teeth in which root fractures were produced experimentally. Each tooth was imaged using the paralleling technique with a CCD-based digital system and D-speed film. The images were interpreted by an experienced radiologist without prior knowledge of the distribution of the root fractures. The degree of agreement in detecting root fractures with each imaging system compared with the actual condition was expressed as the kappa value. The difference between the radiographic systems was then assessed by chi(2)-test at the 95% significance level. RESULTS: There was substantial agreement between the digital system and the actual condition (kappa=0.71; 95% Confidence Interval: 0.62 to 0.80) and close agreement between the film and the actual condition (kappa=0.63; 95% Confidence Interval: 0.53 to 0.74). However, this difference was not significantly different (P=0.2). CONCLUSIONS: The performance of CCD-based digital radiography in detecting root fractures is similar to film-based radiography.     

胃癌的诊断:普通摄影和DR摄影临床对比

本文介绍应用DR进行胃肠检查，以对比CCD-DR对胃癌的诊断的准确性，并作了ROC曲线分析来评价CCD-DR和CR的不同效果。     

Comparison of radiation doses to patients undergoing standard radiographic examinations with conventional screen-film radiography, computed radiography and direct digital radiography

New flat-panel direct digital radiography equipment has recently been installed in our Accident and Emergency Department; its characteristics and versatility are well suited to the work undertaken in this environment. The aim of this study was to compare radiation doses to patients undergoing standard radiographic examinations using conventional screen-film radiography, computed radiography and direct digital radiography; entrance surface dose and effective dose were calculated for six standard examinations (a total of 10 projections) using standard patient exposure parameters for the three imaging modalities. It was found that doses for computed radiography (all examinations) were higher than the doses for the other two modalities; effective doses for direct digital radiography were approximately 29% and approximately 43% lower than those for screen-film radiography and computed radiography, respectively. The image quality met the criteria in the European guidelines for all modalities.     

常规数字化X线摄影与组织均衡技术在鼻骨外伤诊断的比较

目的：探讨数字化X线摄影（DR）中组织均衡技术在鼻骨外伤诊断中的应用价值。方法：对94例鼻骨外伤患者分别行常规鼻骨侧位摄片,对直接获得的图像和采用组织均衡技术进行后处理获得的图像进行比较,比较两组影像的图像质量情况。结果：常规摄影技术得到的图像需反复调节不同的窗宽、窗位,才能显示密度、厚度不同的鼻骨与软组织;组织均衡技术可在同一帧图像上清晰显示鼻骨及其邻近软组织。结论：采用组织均衡技术能将密度和厚度不同的鼻骨及其邻近组织在同一帧图像上清晰显示。     

Resolution requirements for monitor viewing of digital flat-panel detector radiographs: a contrast detail analysis

With the introduction of digital flat-panel detector systems into clinical practice, the still unresolved question of resolution requirements for picture archiving communication system (PACS) workstation monitors has gained new momentum. This contrast detail analysis was thus performed to define the differences in observer performance in the detection of small low-contrast objects on clinical 1K and 2K monitor workstations. Images of the CDRAD 2.0 phantom were acquired at varying exposures on an indirect-type digital flat-panel detector. Three observers evaluated a total of 15 images each with respect to the threshold contrast for each detail size. The numbers of correctly identified objects were determined for all image subsets. No significant difference in the correct detection ratio was detected among the observers; however, the difference between the two types of workstations (1K vs 2K monitors) despite less than 3% was significant at a 95% confidence level. Slight but statistically significant differences exist in the detection of low-contrast nodular details visualized on 1K- and 2K-monitor workstations. Further work is needed to see if this result holds true also for comparison of clinical flat-panel detector images and may, for example, exert an influence on the diagnostic accuracy of chest X-ray readings. Electronic Publication     

Image quality and detection performance of a direct digital radiography system

The physical characteristics of a direct amorphous Selenium (a-Se) digital fluoroscopy and radiography system were investigated. Pre-sampled modulation transfer functions (MTF) were measured using a slit method. Noise power spectra were determined for different input exposures by fast Fourier transform of uniformly exposed samples. The MTFs of direct digital radiography systems showed significantly higher values than those of indirect digital radiography and screen-film systems. The direct digital radiography systems showed higher noise levels compared with those of indirect systems under roughly the same exposure conditions. Contrast-detail analysis was performed to compare detection by direct digital radiography systems with that of the screen-film (FUJI HG-M2/UR2) systems. The average contrast-detail curves of digital and film images were obtained from the results of observation. Image quality figures (IQF) were also calculated from the individual observer performance tests. The results indicated that digital contrast-detail curves and IQF are, on average, are equal those of the screen-film system.     

Depiction of low-contrast detail in digital radiography: comparison of powder- and needle-structured storage phosphor systems

PURPOSE: We sought to evaluate the low-contrast performance of a newly developed needle image plate/line scanner (NIP) computed radiography system in comparison with a standard powder image plate/flying-spot scanner (PIP) system. MATERIALS AND METHODS: A total of 36 images of a CDRAD phantom, simulating low-contrast structures with different drill holes of different diameters, were obtained with both imaging systems using 9 different exposure variables. All images had window and level set to generate consistent density and contrast. In addition, multiscale contrast-dependent contrast amplification was applied to some of the images. All images obtained were printed and presented to a total of 10 observers (5 radiologists, 5 engineers/physicists), who were blinded to both the image plate and parameter setting used. The smallest detectable drill hole depth (= contrast) correctly identified was recorded for each diameter. The median values observed were calculated and tested for statistical differences between PIP and NIP using Student t test for matched pairs (level of significance P < or = 0.05). RESULTS: At all but 2 settings of the variables, NIP images depicted significantly lower contrast levels (= lower depth of drill holes) compared with PIP images. The 2 settings also showed a trend towards better low contrast depiction with NIP. In no case was low contrast performance better using PIP images. CONCLUSION: Images obtained with needle image plate/line scanner provide superior low contrast performance compared with the images obtained with powder image plate/flying-spot scanner.     

Organ doses and subjective image quality of indirect digital panoramic radiography

OBJECTIVES: To determine if slight variations in exposure will affect diagnostic image quality and absorbed radiation doses for digital and analogue panoramic radiography. METHODS: Thermoluminescent dosimeters were placed in the thyroid gland, eyes, submandibular glands, parotid glands and skin of two human cadaver heads. Three different exposure settings were used: 70 kV, 120 mAs; 77 kV, 75 mAs; and 81 kV, 60 mAs. Subjective image quality was assessed using a phantom head. Storage phosphor (SP) images were printed on film and both analogue and SP images were assessed for their subjective image quality on a five-point rating scale. The results were statistically analysed using logistic regression analysis and chi(2) tests. RESULTS: Highest organ doses were measured for the submandibular glands, followed by the parotid glands. Salivary gland doses tended to be higher at lower kV settings. Image quality was not statistically different for the different exposure settings. Imaging technique did not seem to influence diagnostic image quality, except for the periapical status of upper premolars where SP was better. The main reason for any differences appeared to be interobserver variation. CONCLUSIONS: Analogue and SP panoramic radiography performed equally well for subjective diagnostic image quality. No significant differences could be found at the exposure settings used in this study. Radiation doses were highest for the salivary glands, especially at lower kV settings.     

Physical evaluation of a system for direct digital intra-oral radiography based on a charge-coupled device.

OBJECTIVES: To determine technical properties of a direct digital intra-oral radiographic system, the Dixel(R) (J Morita Corporation, Kyoto, Japan). METHODS: A dose response function and the dark current were calculated from two series of exposures to a homogeneous radiation field. The line spread function (LSF) and the modulation transfer function (MTF) were determined from radiographs of an edge. The noise power spectrum (NPS) was determined at three exposures from radiographs exposed to homogeneous radiation fields. Noise equivalent quanta (NEQ) were calculated from the one-dimensional NPS and the MTF. The detective quantum efficiency (DQE) was determined from the NEQ and a representative value of the photon fluence. Signal-to-noise ratios (SNR) were calculated from the NEQs and different signal contrasts. RESULTS: The dose response function demonstrated a slight curvature. There was no effect of the dark current. NPS ranged from 10-5 - 10-7 mm2 depending on exposure and frequency. At a peak of about 2 cycles/mm the DQE is on an average about 30 per cent. SNRs are favorable. CONCLUSION: The technical properties found in this study indicate that the Dixel(R) system is suitable for intra-oral dental radiography.     

Water-soluble contrast media in radiography of small bowel obstruction. Comparison of ionic and non-ionic contrast media

Fifty patients with possible gastrointestinal obstruction, referred for enteric follow-through examination, were randomized for a double-blind, parallel comparison of the hyperosmolar contrast medium Gastrografin and the low-osmolar Omnipaque. The result was that Omnipaque retained its radiographic density in the small bowel better than Gastrografin. Omnipaque was thus a better alternative than Gastrografin in follow-through examinations of intestinal obstruction. Also, 23 patients out of 28 with small bowel obstruction due to peritoneal adhesions, had spontaneous relief of symptoms during the observation period following contrast medium ingestion with no significant difference between the two media. This indicated that enteric follow-through procedures may have a therapeutic efficacy similar to the treatment of small bowel obstruction using nasogastric suction and gastrointestinal rest. Possible mechanisms for this action of the contrast media are discussed.     

计算机X线摄影能量减影与直接数字摄影对胸部软组织病变检测能力比较

目的 比较计算机X线摄影能量减影技术(ES-CR)与直接数字摄影技术(DR)对肺内软组织信号的探测能力。方法 应用胸部放射学体模和X线摄影统计学体模摄取ES-CR和DR影像,由6位放射科医师用5等级判别法各自独立阅读影像,编写程序对观察结果进行受试者操作特性曲线(ROC)分析。收集28例病理证实小肺癌患者的胸部DR影像和ES-CR影像,由3位放射科医师一起做出诊断,分析其真阳性率的差异性。结果 体模影像的ROC分析,ES-CR和DR的 Az 值分别为0.727和0.827,差异有统计学意义( Z =2.96, P<0.05)。28例小肺癌两成像系统的差异也有统计学意义(χ²=5.14, P<0.05)。结论 用DR诊断的真阳性率要高于ES-CR。ES-CR对胸部软组织信号的检出能力尚不如DR。     

直接数字化摄影在尘肺病检查及诊断中的应用研究

目的：探讨直接数字化摄影（DR）技术在尘肺病检查和诊断方面的应用价值。方法选择来我院欲提交诊断的20世纪60～80年代参加国防施工的复退军人及部分经职业健康查体筛选的企业工人共计811例,同时拍摄高千伏（HkV）胸片及DR胸片,部分加照CT扫描胸片,并对二组胸片进行质量及尘肺病诊断一致性等方面的比较。结果二组胸片的质量对比发现：DR胸片总体质量优于高千伏胸片,尤其DR胸片的一级片率明显高于 HkV胸片,DR胸片的三级片率明显低于HkV胸片,且差异有统计学意义（ P ＜0．05）;DR胸片在图像清晰度及肺部微细结构显示方面较好,两组胸片的诊断结果基本一致,尘肺患者胸片在小阴影形态、总体密集度、分布范围方面无明显差别。结论 DR胸片质量好于HkV胸片,三级片率明显低于HkV胸片;DR摄影可用于尘肺病检查与分期诊断。     

The detection of wooden foreign bodies: An experimental study comparing direct digital radiography (DDR) and ultrasonography

IntroductionThis experimental study compares the appropriateness of direct digital radiography (DDR) and ultrasonography at detecting soft-tissue wooden foreign bodies (FBs) in extremities.MethodsVarying wooden FB splinters (2 mm, 5 mm and 10 mm) were inserted into eight porcine feet to simulate a patient presenting with a soft-tissue FB injury. Each of the FBs was placed in muscle distant, behind and near bone in the porcine feet. Control groups were used to check for false-positive diagnoses and, based on the presence of FBs; images were given a score depending on the level of visibility by the researcher.ResultsA higher detection rate was achieved for all FBs in muscle distant from bone using ultrasound. All of the 2 mm and 5 mm wooden FBs were not detected using DDR. The sensitivity in detecting the FBs was 5.8% and 30% in DDR and ultrasound respectively.ConclusionPoor sensitivities and specificities were identified in this study. However, this study shows that ultrasound remains superior to DDR at identifying small foreign body objects. This study demonstrates that ultrasound can be a clinically effective tool for detecting suspected wooden FBs >5 mm in the foot and thus should be considered as the primary imaging modality of choice for referring clinicians.     

Comparison of digital and conventional musculoskeletal radiography: an observer performance study

Interpretations of 122 musculoskeletal radiographs were compared with interpretations of their digital counterparts at a resolution of 1,024 X 840 X 12 bits. Images were evaluated by four readers and included subtle and nonsubtle abnormalities and normal findings. Joint receiver operating characteristic (ROC) analysis results were averaged over all readers and demonstrated no statistically significant difference between the two imaging methods. High interobserver variability limited identifiable differences. Review of cases with subtle findings on the digital system at a resolution of 2,048 X 1,680 X 12 bits (2.5 line pairs per millimeter) revealed adequate visualization of the abnormality in every case. It is concluded that a resolution of 1,024 X 840 X 12 bits is adequate for the interpretation of many musculoskeletal abnormalities but that a resolution of 2,048 X 1,680 X 12 bits is needed for visualization of some subtle abnormalities.     

Optimisation of radiographic acquisition parameters for direct digital radiography: A systematic review

IntroductionThe objective of this systematic review was to uncover and synthesise all available literature regarding appropriate acquisition parameters for direct digital radiography. It sought to either confirm current practices as optimal, or to uncover practices that may produce more optimised results.MethodsA comprehensive search of published and unpublished literature was undertaken to find studies that evaluated how adjustment of different acquisition parameters affected subjective image quality and patient radiation dose. Eight hundred and fifty-eight studies were retrieved for title and abstract screening. Eighty-nine studies were retrieved for full-text screening, and 23 were included for review and methodological quality screening.ResultsNarrative synthesis of the 23 included studies revealed limited evidence to guide any potential change or acceptance of currently accepted best practice. Meta-analysis was unable to be performed for any of the included studies due to high levels of methodological heterogeneity. A key finding of this review was that the goals of optimisation research varied greatly across the included studies.ConclusionSignificant methodological heterogeneity in the included studies limited the number of clinically relevant findings that would give evidence to an acceptance of, or suggest changes to, currently accepted best practice. Improving consistency in approach across future works of technique optimisation will ensure future systematic reviews will be able to provide strong evidence and meta-analysis will be able to be performed.Implications for clinical practiceThis review highlights that in the literature, studies of optimisation of radiographic acquisition parameters have varying goals. This methodological heterogeneity limits the applicability of systematic reviews and precludes the use of meta-analysis. The authors recommend that a framework for optimisation research be produced as a priority to help improve homogeneity in future research.     

Human breast cancer specimens: diffraction-enhanced imaging with histologic correlation--improved conspicuity of lesion detail compared with digital radiography

Seven breast cancer specimens were examined with diffraction-enhanced imaging at 18 keV with a silicon crystal with use of the silicon 333 reflection in Bragg mode. Images were compared with digital radiographs of the specimen, and regions of increased detail were identified. Six of the seven cases (86%) showed enhanced visibility of surface spiculation that correlated with histopathologic information, including extension of tumor into surrounding tissue.