Digital radiography versus conventional radiography in chest imaging: diagnostic performance of a large-area silicon flat-panel detector in a clinical CT-controlled study

Imaging techniques in Veterinary Medicine. Part I: Radiography and Ultrasonography

In Veterinary Medicine all the Imaging techniques are used and described but, due to organizational, managerial and, mostly, economical reasons, Radiography and Ultrasonography are the most used.

Veterinary Radiology teaching has a relatively small number of educational credits in the degree courses but, nowday, educational opportunities are remarkably increased thanks to a number of post-degree courses and masters, organized both by the universities and private veterinary associations. The relevance of Diagnostic Imaging is particularly true in Veterinary Medicine, in which Radiology could be considered “indispensable” for diagnosis, prognosis and follow up. Furthermore, it should not be forgotten that the diagnostic image represents a “document” and, has a relevant role in legal medical debats.

In this first part, Radiography and Ultrasonography are described.

Lung cancer screening by single-shot dual-energy subtraction using flat-panel detector

Purpose

The purpose of this study was to evaluate the usefulness of single-shot dual-energy subtraction (DES) method using a flat-panel detector for lung cancer screening

Materials and methods

The subjects were 13,315 residents (5801 males and 7514 females) aged 50 years or older (50–97 years, with an intermediate value of 68 years) who underwent lung cancer screening for a period of 1 year and 6 months from January 2019 to June 2020. We investigated whether the number of lung cancers detected, the detection rate, and the rate of required scrutiny changed, when DES images were added to the judgment based on conventional chest radiography.

Results

When DES images were added, the number and percentage of cancer detection increased from 16 (0.12%) to 23 (0.17%) (P < 0.05). Five of the newly detected 7 lung cancers were in the early stages of resectable cancer. The rate of participants requiring scrutiny increased slightly from 1.1 to 1.3%.

Conclusion

DES method improved the detection of lung cancer in screening. The increase in the percentage of participants requiring scrutiny was negligible.

Value of thoracic and abdominal screening in dogs with neurological signs

OBJECTIVES

To detect the incidence of clinically important thoracic and abdominal imaging abnormalities in patients with neurological signs but with no clinical signs or laboratory findings consistent with thoracic or abdominal disease.

MATERIALS AND METHODS

Review of imaging findings in dogs with neurological signs but no thoracic or abdominal signs that underwent thoracic, or thoracic and abdominal screening during the same hospitalisation as the neurological investigation.

RESULTS

Two hundred and six dogs were included in the thoracic study. Of those, only eight (3.9%) had clinically important findings and in only five cases (2.4%) were the findings related to pathology identified on MRI. One hundred and forty-seven dogs were included in the abdominal study. Abnormalities were found in 23 dogs (15.6%), but in only eight (5.4%) were they considered to be of current clinical importance and in only three (2%) were they related to the pathology identified on MRI. Ultrasonography provided valuable additional information in 22 cases (15%) but this was only considered important in four (2.7%) and related to the neurological condition in one (0.7%). As expected, abdominal ultrasonography often provided more information than radiography alone in the abdominal screening but this was rarely clinically relevant or related to the reason for referral.

CLINICAL SIGNIFICANCE

Thoracic and abdominal screening of neurological patients with no clinically evident thoracic or abdominal clinical signs only infrequently identified occult but clinically important pathology which changed the current management plan, regardless of neurolocalisation or age.

Feasibility of lung cancer screening in developing countries: challenges, opportunities and way forward

Lung cancer is the leading cause of all cancer deaths worldwide, comprising 18.4% of all cancer deaths. Low-dose computed tomography (LDCT) has shown mortality benefit in various trials and now a standard tool for lung cancer screening. Most researches have been carried out in developed countries where lung cancer incidence and mortality is very high. There is an increasing trend in lung cancer incidence in developing countries attributed to tobacco smoking and various environmental and occupational risk factors. Implementation of lung cancer screening is challenging, so organised lung cancer screening is practically non-existent. There are numerous challenges in implementing such programs ranging from infrastructure, trained human resources, referral algorithm to cost and psychological trauma due to over-diagnosis. Pulmonary tuberculosis and other chest infections are important issues to be addressed while planning for lung cancer screening in developing countries. Burden of these diseases is very high and can lead to over-diagnosis in view of cut off of lung nodule size in various studies. Assessment of high risk cases for lung cancer is difficult as various forms of smoking make quantification non-uniform and difficult. Lung cancer screening targets only high risk population unlike screening programs for other cancers where entire population is targeted. There is a need of lung cancer screening for high risk cases as it saves life. Tobacco control and smoking cessation remain the most important long term intervention to decrease morbidity and mortality from lung cancer in developing countries. There is no sufficient evidence supporting the introduction of population-based screening for lung cancer in public health services.

Bedside Chest Radiographs in the Intensive care Setting: Wireless Direct Radiography Compared to Computed Radiography

OBJECTIVES

To compare image quality, visibility of anatomic landmarks, tubes and lines, and other clinically significant findings on portable (bedside) chest radiographs acquired with wireless direct radiography (DRw) and computed radiography (CR).

METHODS

In a prospective IRB-approved and HIPAA-compliant study, portable DRw (DRX-1C mobile retrofit portable wireless direct radiography, CareStream Inc., Rochester, NY) and portable CR (AGFA CR (DXG) version; NIM2103, AGFA Healthcare, Ridgefield Park, NJ) images of the chest were acquired within 24-hours in 80 patients in the intensive care unit (ICU). Image pairs of 75 patients (37% female) with a mean age of 60.7±16 years were independently compared side-by-side by 7 experienced thoracic radiologists using a five-point scale. When tubes and lines were present, the radiologist also compared an edge-enhanced copy of the DRw image to the CR image.

RESULTS

Most radiologists found significantly fewer artifacts on DRw images compared to CR images and all readers agreed that when present, these artifacts did not significantly preclude the ability to evaluate anatomic landmarks, tubes and lines, or clinically significant findings. None of the radiologists (0/7) reported superior visibility of anatomic structures on CR images compared to DRw images and some radiologists (3/7) found DRw images significantly better for visibility of anatomic landmarks such as the carina (p=0.01-0.001). Most radiologists (6/7) found DRw images to be better or clearly better than CR images for position of tubes and lines, and edge-enhanced DRw images to be especially helpful for evaluation of central venous catheters and esophageal tubes (p=0.027-0.001). None of the radiologists deemed CR images superior for visibility of clinically significant findings.

CONCLUSIONS

Critical care chest radiography with a portable DRw system can provide similar or superior information compared to a CR system regarding clinically significant findings and position of tubes and lines.

Pulmonary involvement in rheumatoid arthritis: evaluation by radiography and spirometry

OBJECTIVE

To determine whether simple diagnostic methods can yield relevant disease information in patients with rheumatoid arthritis (RA).

METHODS

Patients with RA were randomly selected for inclusion in a cross-sectional study involving clinical evaluation of pulmonary function, including pulse oximetry (determination of SpO2, at rest), chest X-ray, and spirometry.

RESULTS

A total of 246 RA patients underwent complete assessments. Half of the patients in our sample reported a history of smoking. Spirometry was abnormal in 30% of the patients; the chest X-ray was abnormal in 45%; and the SpO2 was abnormal in 13%. Normal chest X-ray, spirometry, and SpO2 were observed simultaneously in only 41% of the RA patients. A history of smoking was associated with abnormal spirometry findings, including evidence of obstructive or restrictive lung disease, and with abnormal chest X-ray findings, as well as with an interstitial pattern on the chest X-ray. Comparing the patients in whom all test results were normal (n = 101) with those in whom abnormal test results were obtained (n = 145), we found a statistically significant difference between the two groups, in terms of age and smoking status. Notably, there were signs of airway disease in nearly half of the patients with minimal or no history of tobacco smoke exposure.

CONCLUSIONS

Pulmonary involvement in RA can be identified through the use of a combination of diagnostic methods that are simple, safe, and inexpensive. Our results lead us to suggest that RA patients with signs of lung involvement should be screened for lung abnormalities, even if presenting with no respiratory symptoms.

Visibility and variability of pleural fissures on normal digital chest radiographs of 1,000 healthy adults

PURPOSE

To investigate the visibility and variability of pleural fissures on digital chest radiographs.

METHODS

Posteroanterior digital chest radiographs of 566 males and 434 females were retrospectively reviewed for the frequencies and/or appearances of various pleural fissures.

RESULTS

The right only, left only and bilateral minor fissures were visible in 722 (72.2 %), 1 (0.1 %) and 7 (0.7 %) subjects, respectively. The right minor fissures were visible as more than one line in 219 (30.0 %) subjects, i.e., 2, 3 and 4 lines in 214 (29.3 %), 4 (0.5 %) and 1 (0.1 %), respectively. The 955 visible right minor fissures exhibited variable length (<1/3 of right hemithorax, 17.8 %; 1/3-2/3, 60.1 %; >2/3, 22.1 %), alignment (medial higher 40.9 %; lateral higher 54.2 %; horizontal 4.8 %) and contour (convex upward 68.6 %; convex downward 2.7 %; flat 24.9 %; sigmoid 3.8 %). Superolateral major fissures were visualized in 14.8 % (right only 3.0 %; left only 9.0 %; bilateral 2.8 %), superomedial major fissures in 0.3 % (right 0.1 %; left 0.2 %), vertical fissures in 0.5 % (right 0.2 %; left 0.3 %), inferior accessory fissures in 5.4 % (right 4.8 %; left 0.6 %), right superior accessory fissures in 1.2 % and azygos fissures in 0.2 %.

CONCLUSION

The right minor fissure was most frequently visible and exhibited variable appearances. Other pleural fissures were occasionally seen.

Reliability and validity of soft copy images based on flat-panel detector in pneumoconiosis classification: comparison with the analog radiographs

RATIONALE AND OBJECTIVES

The aim of this study was to evaluate the reliability and validity of soft copy images based on flat-panel detector of digital radiography (DR-FPD soft copy images) compared to analog radiographs (ARs) in pneumoconiosis classification and diagnosis.

MATERIALS AND METHODS

DR-FPD soft copy images and ARs from 349 subjects were independently read by four-experienced readers according to the International Labor Organization 2000 guidelines. DR-FPD soft copy images were used to obtain consensus reading (CR) by all readers as the gold standard. Reliability and validity were evaluated by a κ and receiver operating characteristic analysis, respectively.

RESULTS

In small opacity, overall interreader agreement of DR-FPD soft copy images was significantly higher than that of ARs, but it was not significantly different in large opacity and costophrenic angle obliteration. In small opacity, agreement of DR-FPD soft copy images with CR was significantly higher than that of ARs with CR. It was also higher than that of ARs with CR in pleural plaque and thickening. Receiver operating characteristic areas were not different significantly between DR-FPD soft copy images and ARs.

CONCLUSIONS

DR-FPD soft copy images showed accurate and reliable results in pneumoconiosis classification and diagnosis compared to ARs.

Utility of digital radiography for the screening of pneumoconiosis as compared to analog radiography: radiation dose, image quality, and pneumoconiosis classification

The purpose of this study was to compare digital radiography (DR) and analog radiography (AR) for the screening of pneumoconiosis with respect to radiation dose, image quality, and pneumoconiosis classification. DR was performed on 50 subjects who were enrolled for an examination of pneumoconiosis (Digital Diagnost™, Philips, Netherlands), and AR (MXO-15B, Toshiba, Japan) was performed the same day after the study was approved by the Institutional Review Board and written informed consent was obtained from all subjects. Entrance surface doses (ESDs) of DR and AR were measured using a glass dosimeter attached to a Rando human phantom (Alderson Co., U.S.) under exposure conditions commonly used in clinical practice in Korea. Visibilities on all images were evaluated using a 5-point scale by four chest radiologists using a modified form of the European Chest Guidelines (EUR 16260). All the images were classified using the ILO's guidelines by referencing standard analog radiographs. ESDs of DR were significantly lower than those of AR (0.15 mGy vs. 0.21 mGy, p < 0.05). All anatomic structures were significantly more visible by DR images (p < 0.0001), especially the left main bronchus, ribs, and thoracic spine. Body mass index did not correlate with anatomic structure visibility by DR (r = -0.029, p = 0.842) or AR images (r = -0.076, p = 0.602). Overall intra- and inter-reader agreements for DR images were significantly higher than for AR images. DR offers improved image quality with a significant reduction of up to 23.6% in radiation dose and more accurate pneumoconiosis classification than AR.

The accuracy of digital radiography in orthopaedic applications

BACKGROUND

Recent advances in technology and the use of image archiving and communication systems (PACS) has led some institutions to abandon conventional plain film radiography and rely solely on digital computed radiography. The level of accuracy of digital radiography in measuring distances for orthopaedic applications is unclear.

QUESTIONS/PURPOSES

Is it possible to accurately measure small distances using digital radiographs and PACS software?

MATERIALS AND METHODS

A model for measuring articular step-off was created using a commercially produced radiographic phantom with predetermined markings at known distances. Radiographs were taken using both indirect and direct computed radiography systems, then uploaded to a PACS system. Eighteen observers measured the distance between standardized, preselected points on the radiographic phantom. The measured values were compared with the known values for each measurement.

RESULTS

The mean measured values differed by 0 and 0.1 mm (SD, 0.5 mm) for indirect and direct radiographs, respectively, when measuring short distances and 1.4 mm and 2.6 mm (SD, 1.0 mm) for indirect and direct radiographs, respectively, when measuring longer distances. The intraclass correlation coefficient (ICC) for interobserver reliability was 0.82 for indirect and 0.75 for direct digital radiography. The ICC for intraobserver reliability was 0.94 for indirect and 0.90 for direct digital radiography.

CONCLUSION

Although the mean measured values were very accurate (within 0.1 mm for a known distance of 3.2 mm), the SD of measurements (0.5 mm) could affect the interpretation of data, especially in clinical situations such as evaluating the quality of fracture reduction.

Flat-panel versus 64-channel computed tomography for in vivo quantitative characterization of aortic atherosclerotic plaques

BACKGROUND

Flat-panel computed tomography (FpCT) provides better spatial resolution than 64-channel CT (64-CT) and may improve in vivo quantitative assessment of atherosclerotic plaques.

METHODS AND RESULTS

Lesions in 184 aortic histology sections from 6 Watanabe heritable hyperlipidemic rabbits were quantitatively compared with 64-CT (image thickness, 0.625 mm) and FpCT (image thickness, 0.150 mm) images. Images were re-oriented perpendicular to the vessel centerline. For detecting plaque, FpCT and 64-CT were not significantly different (sensitivity, 76% vs 66%; P=NS). Although FpCT was significantly more sensitive (42% vs 0%; P=<0.001) for detecting eccentric lesions, the area under the curve (AUC) for FpCT (0.6) was not significantly different from that for 64-CT (0.45; P=NS). In detecting plaques with ≤ 10% lipid (low attenuation foci), FpCT was significantly more sensitive than 64-CT (24% vs 0.7%; P<0.00) and had a significantly greater AUC (0.6 vs 0.5; P<0.006). Additionally, FpCT was more sensitive (65% vs 0%; P<0.00) in detecting plaques with ≤ 5% calcium (high attenuation foci) but not in detecting branch points. Both FpCT and histology allowed us to detect low-attenuation foci as small as 0.3mm in diameter, whereas 64-CT allowed us to detect only low-attenuation foci ≥ 1.5mm in diameter.

CONCLUSIONS

Flat-panel CT seemed to have more potential for quantitatively screening low-risk small atherosclerotic lesions, whereas 64-CT was apparently more useful when imaging established, well-characterized lesions, particularly when measuring the vascular wall thickness in a rabbit model of atherosclerosis.

Ability of chest X-ray to detect faint shadows documented as ground-glass attenuation in images of computed tomography: a comparison between flat-panel detector radiography and film-screen radiography

PURPOSE

To compare flat-panel detector (FPD) radiography and film-screen (FS) radiography in detectability of faint shadows documented as ground-glass attenuation (GGA) areas in images of computed tomography (CT).

MATERIALS AND METHODS

Study population was comprised of 50 patients who underwent FS and another 50 patients who underwent FPD. Standard of reference (SOR) was determined on the basis of area of GGA in all cross-sections of CT, in terms of GGA extent and presence or absence of GGA in each trisected lung fields (GGA distribution). Eight radiologists assessed the GGA extent with the 5-grade scale and the GGA distribution. Inter-observer variances of the GGA extents and distributions, degree of divergences and correspondence in the GGA extent and distributions with SOR, were compared between the FS and FPD by the jackknife method and Fisher's exact test.

RESULTS

Inter-observer variance in the GGA extent and distribution were slightly larger in the FS than in the FPD. The GGA extent scale corresponded with SOR in the FS statistically significantly better (p=0.001), as the correct ratio was 0.428 in the FS and 0.310 in the FPD. Divergence in the GGA extent scale with SOR was smaller in the FS, as average kappa pseudo-value of Kendall's rank correlation coefficient was 0.474 in the FS and 0.433 in the FPD.

CONCLUSION

These results indicate that some lesions of GGA documented in CT may not be reflected and are difficult to be detected in chest X-ray radiographs with the FPD.

The influence of liquid crystal display monitors on observer performance for the detection of interstitial lung markings on both storage phosphor and flat-panel-detector chest radiography

PURPOSE

To compare observer performance with a flat-panel liquid crystal display (LCD) monitor and with a high-resolution gray-scale cathode ray tube (CRT) monitor in the detection of interstitial lung markings using a silicon flat-panel-detector direct radiography (DR) and storage phosphor computed radiography (CR) in a clinical setting.

MATERIALS AND METHODS

We displayed 39 sets of posteroanterior chest radiographs from the patients who were suspected of interstitial lung disease. Each sets consisted of DR, CR and thin-section CT as the reference standard. Image identities were masked, randomly sorted, and displayed on both five mega pixel (2048x2560x8 bits) LCD and CRT monitors. Ten radiologists independently rated their confidence in detection for the presence of linear opacities in the four fields of the lungs; right upper, left upper, right lower, and left lower quadrant. Performance of a total 6240 (39 setsx2 detector systemsx2 monitor systemx4 fieldsx10 observers) observations was analyzed by multi-reader multi-case receiver operating characteristic (ROC) analysis. Differences between monitor systems in combinations of detector systems were compared using ANOVA and paired-samples t-test.

RESULTS

Area under curves (AUC) for the presence of linear opacities measured by ROC analysis was higher on the LCDs than CRTs without statistical significance (p=0.082). AUC was significantly higher on the DR systems than CR systems (p=0.006). AUC was significantly higher on the LCDs than CRTs for DR systems (p=0.039) but not different for CR systems (p=0.301).

CONCLUSION

In clinical conditions, performance of the LCD monitor appears to be better for detecting interstitial lung markings when interfaced with DR systems.

Detectability of lung nodules using flat panel detector with dual energy subtraction by two shot method: Evaluation by ROC method

The aim of this study was to evaluate the effectiveness of dual-exposure dual energy subtraction technique in flat-panel chest radiography for lung nodules detection. Chest radiographs were acquired in 100 patients (57 men and 43 women; mean age, 60.2 years; range, 18-89 years) using a flat-panel digital chest system. These images were evaluated by seven radiologists. A continuous rating scale of 0-100 was used to represent each observer's confidence level regarding the presence or absence of lung nodules. Observer performance for detection of lung nodules with subtraction images was tested by using receiver operating characteristic (ROC) analysis of individual and averaged reader data. The average area under the ROC curve (Az value) significantly increased with subtraction images (Az=0.79 in standard radiographs versus Az=0.84 with subtraction images, p<0.05). In conclusion, the two-exposure dual-energy subtraction chest radiography significantly would improve detection of lung nodules.

Detection of simulated nodules on clinical radiographs: dose reduction at digital posteroanterior chest radiography

PURPOSE

To determine to what extent dose reduction results in decreased detection of simulated nodules on patient digital posteroanterior (PA) chest radiographs.

MATERIALS AND METHODS

Raw data from 20 clinical digital PA chest images that were reported as having normal findings and that were obtained with a slot-scan charge-coupled device system were used. For research protocol that concerns data with patient identities concealed, institutional review board approval is not required. One hundred twenty nodules varying in size and signal intensity were digitally simulated and added to the chest images. Hard copies were printed to represent a 100% dose and, by adding noise, to represent simulated patient doses of 50%, 25%, and 12%. Four radiologists reviewed images. Each lesion was registered as "detected" or "not detected." A semiparametric logistic regression model was used for statistical analysis.

RESULTS

The decrease in radiation dose from 100% to 50%, 25%, or 12% had no effect on lesion detection in the lungs. The decrease in radiation dose had an effect on lesion detection in the mediastinum, as probabilities deteriorated from the 100% dose to the 50%, 25%, and 12% dose with each step. Probabilities of smaller detection rates when compared with that of the reference category (100% dose) were 0.97 (95% confidence interval [CI]: -0.86, 0.012) for the 50% dose, 1 (CI: -0.59, -0.61) for the 25% dose, and 1 (CI: -2.41, -1.22) for the 12% dose. CIs for the effects were on the log(odds). Detection probability decreased with smaller and lower signal intensity lesions.

CONCLUSION

At clinical digital radiography, dose reduction resulted in decreased observer detection of simulated nodules in the mediastinum but not in the lungs.

Image quality and radiation dose on digital chest imaging: comparison of amorphous silicon and amorphous selenium flat-panel systems

OBJECTIVE

The aim of this study was to compare the image quality and radiation dose in chest imaging using an amorphous silicon flat-panel detector system and an amorphous selenium flat-panel detector system. In addition, the low-contrast performance of both systems with standard and low radiation doses was compared.

MATERIALS AND METHODS

In two groups of 100 patients each, digital chest radiographs were acquired with either an amorphous silicon or an amorphous selenium flat-panel system. The effective dose of the examination was measured using thermoluminescent dosimeters placed in an anthropomorphic Rando phantom. The image quality of the digital chest radiographs was assessed by five experienced radiologists using the European Guidelines on Quality Criteria for Diagnostic Radiographic Images. In addition, a contrast-detail phantom study was set up to assess the low-contrast performance of both systems at different radiation dose levels. Differences between the two groups were tested for significance using the two-tailed Mann-Whitney test.

RESULTS

The amorphous silicon flat-panel system allowed an important and significant reduction in effective dose in comparison with the amorphous selenium flat-panel system (p < 0.0001) for both the posteroanterior and lateral views. In addition, clinical image quality analysis showed that the dose reduction was not detrimental to image quality. Compared with the amorphous selenium flat-panel detector system, the amorphous silicon flat-panel detector system performed significantly better in the low-contrast phantom study, with phantom entrance dose values of up to 135 muGy.

CONCLUSION

Chest radiographs can be acquired with a significantly lower patient radiation dose using an amorphous silicon flat-panel system than using an amorphous selenium flat-panel system, thereby producing images that are equal or even superior in quality to those of the amorphous selenium flat-panel detector system.

A KNOWLEDGE-BASED LUNG NODULE DETECTION SYSTEM FOR HELICAL CT IMAGES

In this paper, we describe a knowledge-based system for segmenting and labeling lung nodule on helical CT images. The system was developed under a blackboard environment that incorporates a lung knowledge model, image processing model, inference engine and a blackboard. Lung model, which contains both analogical and propositional knowledge about lung in the form of semantic networks, was used to guide the interpretation process. The system works in a hierarchical structure, from large structures to the final nodule candidates by focusing on the interested region step by step. The symbolic variables, introduced to accomplish high-level inference, were defined by fuzzy confidence functions in the lung model. Composite fuzzy functions were applied to evaluate the plausibility of the mapping between the image and lung model objects. Anatomical lung segments knowledge was embedded in the system to direct 3D validation of suspicious objects. Structures were identified and abnormal objects were reported. The experimental results obtained demonstrate the proof of concept and the potential of the automated knowledge-based lung nodule detection system.

Are Occult Pneumothoraces Truly Occult or Simply Missed?

BACKGROUND

Nonradiologists typically diagnose pneumothoraces (PTX) based on a visible pleural stripe. PTXs not seen on supine AP chest radiographs (CXR), but appreciated on a computed tomographic (CT) scan, termed occult pneumothoraces (OPTX), are increasingly common. The purpose was to (1) determine whether perceived OPTXs were truly occult or simply missed and (2) address factors that contribute to the poor sensitivity of the supine CXR.

METHODS

A previous study of severely injured patients (ISS >or =12) identified 44 patients with OPTXs. JPEG images of these CXRs were randomly arranged with images of 11 injured patients without PTXs (CT proven). Three unique groups of radiologists reviewed the images for signs of PTXs, and determined if a thoracic CT was subsequently required.

RESULTS

Retrospective review identified only 12 to 24% of the OPTXs depending on radiology group. The kappa inter-observer agreement value was 0.55 to 0.56 (poor agreement). PTXs were most commonly identified via the deep sulcus sign (75-90%). CXRs were considered inadequate in 16 to 25% of OPTX images and in 0 to 18% of images without OPTXs. Thoracic CT scans were recommended in 18 to 33% of patients with inadequate CXRs, but 67 to 82% of patients with adequate CXRs.

CONCLUSIONS

Less than 24% of all OPTXs might have been inferred from subtle radiologic findings, such as the deep sulcus sign. The majority of OPTX cases (50-64%) did not warrant a CT scan based on other findings. Concern for an OPTX after severe trauma is a valid indication for thoracic CT.

Computed Radiography and Direct Radiography

PURPOSE

We sought to evaluate the performance of dual-readout and single-readout computed radiography compared with direct radiography for detecting subtle lung abnormalities with a standard and a low-dose technique.

MATERIALS AND METHODS

Posteroanterior radiographs of an anthropomorphic chest phantom were obtained with a single-readout storage phosphor radiography system (CRS, pixel size 200 microm), a dual-readout storage phosphor radiography system (CRD, pixel size 100 microm), and a direct detector (DR, pixel size 143 microm) at dose levels of 400 and 800 speed. Ten templates were superimposed to project 4 types of lesions over low- and high-attenuation areas, simulating nodules, micronodules, lines, and patchy opacities. Six radiologists evaluated 60 hard-copy images for the presence or absence of lesions. Statistical significance of differences was evaluated using receiver operating characteristic analysis and analysis of variance.

RESULTS

For both low- and high-attenuation areas, CRD (Az = 0.85 and 0.66) was superior to CRS (Az = 0.75 and 0.58) for overall performance and all lesion subtypes (P < 0.05). DR (Az = 0.87 and 0.67) performed slightly better than CRD, being significant only for the detection of micronodules. Acquisition dose significantly affected only the detection of lines and micronodules, whereas the detection of nodules and patchy opacities was not significantly different with reduced exposure, regardless of the system used.

CONCLUSION

The dual-readout CR system significantly outperformed the single-readout CR and almost equaled the performance of DR. Dose reduction was more critical for small-sized lesions (micronodules, lines) than for nodular or patchy opacifications and affected mainly the lesions in high attenuation areas.

Does digital imaging decrease patient dose? A pilot study and review of the literature

The potential for decreasing patient dose is one of the main arguments for the justification of the cost of digital imaging equipment. However, the literature review with respect to patient doses using digital imaging modalities, presents conflicting results. During this study, patients' entrance surface doses were measured for three simple radiographic examinations, in European centres equipped with a computed radiography digital system. Results showed that doses between centres varied from 30% for chest LAT to 250% for chest PA examination. With the digital image quality criteria still under discussion, and with the post-processing parameters and/or image documentations varying, any dose comparisons between conventional/digital systems, as well as dose comparisons between different centre using digital units, are difficult. Clinical trials are required in order to define reference levels associated with quality of digital image necessary to address specific clinical requirements.

Contrast-Detail Phantom Study for X-ray Spectrum Optimization Regarding Chest Radiography Using a Cesium Iodide-Amorphous Silicon Flat-Panel Detector

RATIONALE AND OBJECTIVES

The purpose of this study evaluating a cesium iodide-amorphous silicon-based flat-panel detector was to optimize the x-ray spectrum for chest radiography combining excellent contrast-detail visibility with reduced patient exposure.

MATERIALS AND METHODS

A Lucite plate with 36 drilled holes of varying diameter and depth was used as contrast-detail phantom. For 3 scatter body thicknesses (7.5 cm, 12.5 cm, 21.5 cm Lucite) images were obtained at 113 kVp, 117 kVp, and 125 kVp with additional copper filter of 0.2 and 0.3 mm, respectively. For each setting, radiographs acquired with 125 kVp and no copper filter were taken as standard of reference. On soft-copy displays, 3 observers blinded to the exposure technique evaluated the detectability of each aperture in each image according to a 5-point scale. The number of points given to all 36 holes per image was added. The scores of images acquired with filtration were compared with the standard images by means of a multivariate analysis of variance. Radiation burden was approximated by referring to the entrance dose and calculated using Monte Carlo method.

RESULTS

All 6 evaluated x-ray spectra resulted in a statistically equivalent contrast-detail performance when compared with the standard of reference. The combination 125 kVp with 0.3 mm copper was most favorable in terms of dose reduction (approximately 33%).

CONCLUSION

Within the constraints of the presented contrast-detail phantom study simulating chest radiography, the CsI/a-Si system enables an addition of up to 0.3 mm copper filtration without the need for compensatory reduction of the tube voltage for providing constant image quality. Beam filtration reduces radiation burden by about 33%.

Digital Slot-Scan Charge-coupled Device Radiography versus AMBER and Bucky Screen-Film Radiography for Detection of Simulated Nodules and Interstitial Disease in a Chest Phantom

PURPOSE

To evaluate the diagnostic performance of full-field slot-scan charge-coupled device (CCD)-based digital radiography in the detection of simulated chest diseases in clinical conditions versus that of two screen-film techniques: advanced multiple beam equalization radiography (AMBER) and Bucky radiography.

MATERIALS AND METHODS

Simulated nodules and interstitial nodular and interstitial linear lesions were attached onto an anthropomorphic chest phantom. One hundred sixty-eight lesions were distributed over 25 configurations. A posteroanterior chest radiograph of each configuration was obtained with each technique. The images were presented to six observers. Each lesion was assigned one of two outcome scores: "detected" or "not detected." False-positive readings were evaluated. Differences between the imaging methods were analyzed by using a semiparametric logistic regression model.

RESULTS

For simulated nodules and interstitial linear disease, no statistically significant difference was found in diagnostic performance between CCD digital radiography and AMBER. The detection of simulated interstitial nodular disease was better with CCD digital radiography than with AMBER: Sensitivity was 71% (77 of 108 interstitial nodular lesions) with CCD digital radiography but was 56% (60 of 108 lesions) with AMBER (P =.041). Better results for the detection of all lesion types in the mediastinum were observed with CCD digital radiography than with Bucky screen-film radiography: Sensitivity was 45% (227 of 504 total simulated lesions) with CCD digital radiography but was 24% (119 of 504 lesions) with Bucky radiography (P <.001). There were fewer false-positive observations with CCD digital radiography (35 [5.7%] of 609 observations) than with Bucky radiography (47 [9.5%] of 497 observations; P =.012).

CONCLUSION

Differences were in favor of the full-field slot-scan CCD digital radiographic technique. This technique provides a digital alternative to AMBER and Bucky screen-film radiography.

Dose reduction in patients undergoing chest imaging: digital amorphous silicon flat-panel detector radiography versus conventional film-screen radiography and phosphor-based computed radiography

OBJECTIVE

We sought to compare the radiation dose delivered to patients undergoing clinical chest imaging on a full-field digital amorphous silicon flat-panel detector radiography system with the doses delivered by a state-of-the-art conventional film-screen radiography system and a storage phosphor-based computed radiography system. Image quality was evaluated to ensure that the potential reduction in radiation dose did not result in decreased image acuity. SUBJECTS AND METHODS. Three groups of 100 patients each were examined using the amorphous silicon flat-panel detector, film-screen, or computed radiography systems. All patient groups were matched for body mass index, sex, and age. To measure the entrance skin dose, we attached 24 calibrated thermoluminescent dosimeters to every patient. The calculation of the effective dose, which represents the risk of late radiation-induced effects, was based on measurements on an anthropomorphic phantom. Image quality of all three systems was evaluated by five experienced radiologists, using the European Quality Criteria for Chest Radiology. In addition, a contrast-detail phantom study was set up to assess the low-contrast detection of all three systems.

RESULTS

The amorphous silicon flat-panel detector radiography system allowed an important and significant reduction in both entrance skin dose and effective dose compared with the film-screen radiography (x 2.7 decrease) or computed radiography (x 1.7 decrease) system. In addition, image quality produced by the amorphous silicon flat-panel detector radiography system was significantly better than the image quality produced by the film-screen or computed radiography systems, confirming that the dose reduction was not detrimental to image quality.

CONCLUSION

The introduction of digital flat-panel radiography systems based on amorphous silicon and cesium iodide is an important step forward in chest imaging that offers improved image quality combined with a significant reduction in the patient radiation dose.

Lumbar spine radiography: digital flat-panel detector versus screen-film and storage-phosphor systems in monkeys as a pediatric model

PURPOSE

To assess image quality and exposure dose requirements of a flat-panel detector system versus screen-film and storage-phosphor systems for radiographic depiction of the lumbar spine in Cynomolgus monkeys as a pediatric model.

MATERIALS AND METHODS

Twenty Cynomolgus monkeys underwent anteroposterior radiography of the lumbar spine. The size and weight of these monkeys are comparable to those of infants 3-4 months of age. Images were acquired with speed class 400 screen-film, flat-panel, and storage-phosphor systems with identical exposure dose. All other conditions were matched exactly. Additional images were acquired with the flat-panel and storage-phosphor systems at exposure doses equivalent to speed classes 800 and 1600. All images were obtained at 66 kVp without antiscatter grid. Images were assessed independently by three radiologists for visibility of 60 anatomic structures by using a five-point confidence scale. Scores were calculated for the seven combinations of imaging mode and exposure dose and were compared by using the Friedman test.

RESULTS

Scores were 1.70 (speed class 400), 1.97 (speed class 800), and 2.27 (speed class 1600) for the flat-panel system; 2.50 (speed class 400) for the screen-film system; and 2.58 (speed class 400), 2.77 (speed class 800), and 3.13 (speed class 1600) for the storage-phosphor system. Scores for the flat-panel system at speed classes 400 and 800 were significantly lower (indicating better visibility) than those of the screen-film and storage-phosphor systems (P <.05).

CONCLUSION

The flat-panel system is superior to screen-film and storage-phosphor systems in lumbar spine radiography in monkeys. With the flat-panel system, exposure dose can be reduced by 75% without loss in image quality.

A survey of non-accidental injury imaging in England, Scotland and Wales

AIM

To identify the potential national variation in non-accidental injury (NAI) imaging in England, Scotland and Wales.

MATERIALS AND METHODS

A postal survey was sent to 323 hospitals with both paediatric and radiology departments. These were identified by a search through the Medical Directory.

RESULTS

One hundred and thirteen of 323 postal questionnaires were returned within the study period (35%). Sixteen were excluded from the study because either no NAI imaging was performed at that institution or an incorrect address had been used. The total number of completed questionnaires was 97 (30%). Extensive variation was seen in all aspects of NAI imaging including imaging techniques used, total case numbers, follow-up imaging and those who report the NAI imaging.

CONCLUSIONS

There is currently no national protocol that incorporates all aspects of NAI imaging in England, Scotland and Wales. Extensive variation in practice has been shown by this survey. Further standardization of NAI imaging practice is required. The draft BSPR skeletal survey guidelines and routine neurological imaging is recommended.

A comparison of conventional film, CR hard copy and PACS soft copy images of the chest: analyses of ROC curves and inter-observer agreement

STUDY OBJECTIVE

The aim of this study was to determine whether the accuracy of diagnosis of a spectrum of chest pathology was affected by the imaging technique used, and to compare conventional film/screen, hard copy computed (phosphor plate) radiography (CR) and soft copy CR (PACS) images.

MATERIALS AND METHODS

For each of 44 patients who had a CT examination of the thorax, PA and lateral chest radiographs were produced using conventional film, hard copy CR and soft copy PACS images. Five radiologists independently scored all images for the presence of abnormalities. The data were analysed in two stages using the result of the CT scan as the reference standard diagnosis: firstly, to investigate differences in abnormality scores between image modalities and observers using ROC analysis; secondly, to investigate the agreement of the diagnoses with the reference standard by the analysis of kappa scores.

RESULTS

The ROC analyses and comparison of kappa scores showed no differences between image modalities (P=0.72, P=0.87), but highly significant differences between observers (P<0.001, P=0.003).

CONCLUSION

The detection of chest lesions did not vary between conventional film, CR hard copy and PACS soft copy images. For all three image types, there were statistically significant differences between observers.

Comparing image quality of flat-panel chest radiography with storage phosphor radiography and film-screen radiography

OBJECTIVE

To evaluate image quality of a large-area direct-readout flat-panel detector system in chest radiography, we conducted an observer preference study. A clinical comparative study was conducted of the flat-panel system versus the storage phosphor and standard film-screen systems.

MATERIALS AND METHODS

Routine chest radiographs (posteroanterior) of 30 patients that were obtained using flat-panel, storage phosphor, and film screen systems were compared. The visibility of 10 anatomic regions and the overall image quality criteria were rated independently by three radiologists using a 5-point scale. The significance of the differences in diagnostic performance was tested with a Wilcoxon's signed rank test. Dose measurements for the three modalities were performed.

RESULTS

The flat-panel radiography system showed an improved visibility in most anatomic structures when compared with a state-of-the-art conventional film-screen system and an equal visibility when compared with a storage phosphor system. The flat-panel system showed the greatest enhancement in the depiction of small detailed structures (p < 0.05) and achieved this with a reduction in overall radiation dose of more than 50%.

CONCLUSION

The visibility of anatomic structures provided by this flat-panel detector system is as good as if not better than that provided by conventional or storage phosphor systems while emitting a reduced radiation dose.

Digital radiography of the chest: detector techniques and performance parameters

Substantial advances in detector technology characterize digital chest radiography. This article compares the various systems from a radiologist's point of view. Computed radiography (CR) is a well-established system that is robust, has good reproducibility, and is relatively inexpensive. Image quality has been continuously improved in recent years while the physical size of the readout units has been reduced and the throughput increased. CR is the only digital system that can be used for bedside chest radiographs. Improved detector properties and dual reading have made it a dose-efficient system. Although now widely available, a 4K image matrix does not appear to offer a general diagnostic improvement for imaging the chest. New developments with respect to detector composition and readout process can be expected in the future. Direct radiography (DR) is the common name for different technologies that are characterized by a direct readout matrix that covers the whole exposure area. Conversion of x-ray intensity into electric signals can either be direct (selenium-based systems) or indirect (scintillator/photodiode systems). Advantages of DR systems are a high image quality and the potential for dose reduction. The role of selenium radiography (Thoravision) has decreased after the advent of DR systems although this dedicated chest unit offers high image quality at 400 speed acquisition dose. Especially in a PACS environment, CR and DR systems will increasingly substitute for conventional radiography with advantages for CR for bedside chest radiographs and for DR for high-end chest stands.

Performance of a flat-panel detector in the detection of artificial erosive changes: comparison with conventional screen-film and storage-phosphor radiography

The purpose of this study was to compare a large-area, direct-readout, flat-panel detector system with a conventional screen-film system, a storage-phosphor system, and a mammography screen-film system with regard to the detection of artificial bone erosions simulating rheumatoid disease, and to assess its diagnostic performance with decreasing exposure dose. Six hundred forty regions were defined in 160 metacarpophalangeal and proximal interphalangeal joint specimens from 20 monkey paws (4 regions per joint). Artificial bone erosions were created in 320 of these 640 regions. Specimens were enclosed in containers filled with water to obtain absorption and scatter radiation conditions similar to those of a human hand. Imaging was performed using a flat-panel system, a speed class 200 screen-film system, a mammography screen-film system, and a storage-phosphor system under exactly matched conditions. Different exposure doses equivalent to speed classes of S=100, 200, 400, 800, 1600, and 3200 were used. In all images the presence or absence of a lesion was assessed by three radiologists using a five-level confidence scale. Receiver operating characteristic (ROC) analysis was performed for a total of 21,120 observations (1920 for each imaging modality and exposure level) and diagnostic performance estimated by the area under the ROC curve (A(z)). The significance of differences in diagnostic performance was tested with analysis of variance. The ROC analysis showed A(z) values of 0.809 (S=200), 0.768 (S=400), 0.737 (S=800), 0.710 (S=1600), and 0.685 (S=3200) for the flat-panel system, 0.770 for the speed class 200 screen-film system, 0.781 (S=200), 0.739 (S=400), 0.724 (S=800), 0.680 (S=1600) for the storage-phosphor system, and 0.798 for the mammography screen-film system. Analysis of variance showed significant differences between different combinations of imaging modalities and exposure doses ( p<0.05). The diagnostic performance of the flat-panel detector system is superior to that of a screen-film system and a storage-phosphor system for the detection of erosive lesions at clinical exposure settings (S=200). Using the flat-panel system the exposure dose can be reduced by 50% to obtain a diagnostic performance comparable to a speed class 200 screen-film system.

Detection of subtle undisplaced rib fractures in a porcine model: radiation dose requirement--digital flat-panel versus screen-film and storage-phosphor systems

PURPOSE

To compare a large-area direct read-out flat-panel detector radiography system with screen-film and storage-phosphor systems with regard to detection of subtle undisplaced rib fractures and to assess the diagnostic performance of the flat-panel system with decreasing exposure level.

MATERIALS AND METHODS

Subtle fractures were created artificially in 100 of 200 porcine rib specimens. Specimens were enclosed in containers of water to generate absorption and scatter radiation conditions similar to those of a human chest wall. Imaging was performed with flat-panel, screen-film, and storage-phosphor systems with conditions that were exactly matched. Different exposure levels equivalent to speed classes (S) of 400, 800, 1,600, and 6,400 were used. All images were independently assessed for the presence of fracture by three radiologists with a five-level confidence scale. Receiver operating characteristic (ROC) analysis was performed for a total of 4,200 observations (600 for each imaging system and exposure level). Diagnostic performance was estimated with area under the ROC curve (Az). Significance of differences in diagnostic performance was tested with analysis of variance.

RESULTS

ROC analysis yielded mean Az values for the flat-panel system of 0.879 (S = 400), 0.833 (S = 800), 0.765 (S = 1,600), and 0.576 (S = 6,400). Az values were 0.834 (S = 400) for the screen-film system and 0.789 (S = 400) and 0.729 (S = 800) for the storage-phosphor system. Analysis of variance revealed significant differences in diagnostic performance between various combinations of imaging system and exposure levels (P <.05).

CONCLUSION

The flat-panel system is superior to the screen-film and storage-phosphor systems for detection of subtle undisplaced rib fractures at clinical exposure settings (eg, S = 400). With the flat-panel system, radiation dose can be reduced by 50% to achieve diagnostic performance comparable to that of a speed class 400 screen-film system.

Clinical comparative study with a large-area amorphous silicon flat-panel detector: image quality and visibility of anatomic structures on chest radiography

OBJECTIVE

The objective of this study was to compare clinical chest radiographs of a large-area, flat-panel digital radiography system and a conventional film-screen radiography system. The comparison was based on an observer preference study of image quality and visibility of anatomic structures.

MATERIALS AND METHODS

Routine follow-up chest radiographs were obtained from 100 consecutive oncology patients using a large-area, amorphous silicon flat-panel detector digital radiography system (dose equivalent to a 400-speed film system). Hard-copy images were compared with previous examinations of the same individuals taken on a conventional film-screen system (200-speed). Patients were excluded if changes in the chest anatomy were detected or if the time interval between the examinations exceeded 1 year. Observer preference was evaluated for the image quality and the visibility of 15 anatomic structures using a five-point scale.

RESULTS

Dose measurements with a chest phantom showed a dose reduction of approximately 50% with the digital radiography system compared with the film-screen radiography system. The image quality and the visibility of all but one anatomic structure of the images obtained with the digital flat-panel detector system were rated significantly superior (p < or = 0.0003) to those obtained with the conventional film-screen radiography system.

CONCLUSION

The image quality and visibility of anatomic structures on the images obtained by the flat-panel detector system were perceived as equal or superior to the images from conventional film-screen chest radiography. This was true even though the radiation dose was reduced approximately 50% with the digital flat-panel detector system.

Performance of a flat-panel detector in detecting artificial bone lesions: comparison with conventional screen-film and storage-phosphor radiography

PURPOSE

To compare a large-area direct-readout flat-panel detector system with a conventional screen-film system and a storage-phosphor system in detecting small artificial osseous lesions simulating osteolytic disease and to assess diagnostic performance with decreasing exposure dose.

MATERIALS AND METHODS

Artificial lesions (0.5-3.0 mm) were created in 100 of 200 predefined regions in 20 porcine femoral specimens. Specimens were enclosed in containers filled with water to create absorption and scatter radiation conditions comparable with those in a human extremity. Imaging was performed with a flat-panel detector system, a conventional screen-film system, and a storage-phosphor system. Levels of exposure equivalent to speed classes 400, 800, 1600, and 3200 were used. In all images, the presence or absence of a lesion was assessed by three radiologists using a five-point confidence scale. Receiver operating characteristic (ROC) analysis was performed for 4,800 observations (600 for each imaging modality and exposure level) and diagnostic performance estimated with the area under the ROC curve (A(z)). The significance of differences in diagnostic performance was tested with analysis of variance.

RESULTS

ROC analysis showed A(z) values of 0.820 (speed class 400), 0.780 (class 800), 0.758 (class 1600), and 0.676 (class 3200) for the flat-panel detector; 0.761 (class 400), 0.725 (class 800), and 0.662 (class 1600) for the storage-phosphor system; and 0.788 (class 400) for the conventional screen-film system. The A(z) value for the flat-panel detector at speed class 400 was significantly higher than that for all other systems (P <.05). A(z) values for the speed class 400 screen-film system and flat-panel detector system at speed class 800 were not significantly different.

CONCLUSION

The flat-panel detector has diagnostic performance superior to that of conventional screen-film and storage-phosphor radiography for detecting small artificial osseous lesions at clinical exposure settings. With the flat-panel detector, exposure dose can be reduced by 50% to obtain diagnostic performance comparable with that of a conventional speed class 400 screen-film system.

Assessment of abdominal aortic aneurysms using a cone-beam CT system: an experimental phantom study and an initial clinical evaluation before and after stent-graft treatment in patients with an abdominal aortic aneurysm

The aim of this study is to conduct a quantitative analysis of cone-beam CT (CBCT) images using a phantom, and then to evaluate the clinical usefulness of CBCT in the assessment of abdominal aortic aneurysms (AAA) before and after stent-grafting, both qualitatively as well as quantitatively. The phantom used in this study was a rectangular plate made of an acrylic resin, which contained eight through-holes to mimic blood vessels. Each columnar cavity was filled with contrast media and the diameter of each was then measured using a cone-beam multiplanar reformation/curved planar reformation (CB-MPR/CPR) technique, and the results were compared with the corresponding results obtained by actual measurement. In the clinical assessment, nine patients with AAA (consisting only of males with an average age of 68 years old: 56 approximately 80) were enrolled. The clinical qualitative analysis of CBCT consisted of: 1) for the pre-operative state, the shape of the aortic aneurysm, the relationship between the aneurysm and the aortic branches, and 2) for the post-operative state, the shape of the stent and any endoleakage present. The clinical quantitative analysis of CBCT included, for the aneurysm, its inflection angle, its maximum diameter, the diameter of the proximal and distal necks, and the distance of these two necks from specific reference points. The quantitative analysis using the phantom showed no significant differences between the results based on CB-MPR/CPR and those obtained by actual measurement. In the clinical qualitative analysis three-dimensional CBCT (3D-CBCT) depicted the anatomical relationship between the aneurysm and the aortic branches well, an accomplishment that was not possible by conventional angiography. Cone-beam maximum intensity projection (CB-MIP) was as good in tracing the migration and deformation of the stent following endovascular intervention as plain radiograms and conventional angiograms. CB-MPR/CPR enabled us to obtain any cross-sectional image of the aorta desired, including a curved, longitudinal cross-section of the aorta. Thus, with the CB-MPR/CPR technique it is easy to determine the distance of the proximal and distal necks of the aneurysm, and the inflection angle, and those results were not significantly different from those obtained by angiography. The diameter of the aneurysm, and the diameter of the proximal and distal necks as measured by CB-MPR/CPR images were significantly different from those obtained by conventional contrast enhanced-CT (p<0.05). This suggests that CB-MPR/CPR yields a cross-sectional view that is more perpendicular to the longitudinal direction of the aorta than that given by conventional contrast enhanced-CT, and thus provides a more accurate cross-sectional image of the aneurysm than the latter. We conclude that, in the experimental phantom study CBCT had a high quantitative reliability, and that, in the clinical study CBCT provided useful information for both qualitatively and quantitatively evaluating AAA before and after stent-grafting.