Selenium radiography versus storage phosphor and conventional radiography in the detection of simulated chest lesions

Detectability of simulated interstitial pneumonia on chest radiographs: comparison between irradiation side sampling indirect flat-panel detector and computed radiography

OBJECTIVE

To compare the detectability of simulated interstitial pneumonia on chest radiographs between an irradiation side sampling indirect flat-panel detector (ISS-FPD) and computed radiography (CR).

METHODS

Simulated interstitial pneumonia findings (ground-glass opacity, reticular opacity and honeycomb lung) were superimposed on an anthropomorphic chest phantom. Chest radiographs were acquired under three exposure levels (4.0, 3.2 and 2.0 mAs) with an ISS-FPD and with CR. 5 thoracic radiologists evaluated 72 images for the presence or absence of a lesion over each of 6 areas. A total of 1296 observations were analysed in a receiver-operating characteristic analysis. A jackknife method was used for the statistical analysis.

RESULTS

The areas under the curves (AUCs) for the detection of simulated honeycomb lung obtained with the ISS-FPD were significantly larger than those obtained with CR at all exposure conditions. For the detection of simulated ground-glass opacity and reticular opacity, there were no significant differences between the two systems. In addition, the AUCs for the detectability of simulated honeycomb lung obtained with the ISS-FPD at all exposure levels were significantly larger than those obtained with CR at 4 mAs.

CONCLUSION

The ISS-FPD was superior to CR for the detection of simulated honeycomb lung. Provided that the chosen model is representative of interstitial pneumonia, the use of an ISS-FPD might reduce a patient's exposure dose during the detection of interstitial pneumonia.

ADVANCES IN KNOWLEDGE

The ISS-FPD has shown its advantage compared with CR in the detection of honeycombing, one sign of interstitial pneumonia.

Investigation of optimum X-ray beam tube voltage and filtration for chest radiography with a computed radiography system

The purpose of this study was to determine the optimum tube voltage and amount of added copper (Cu) filtration for processed chest radiographs obtained with an Agfa 75.0 Computed Radiography (CR) system. The contrast-to-noise ratio (CNR) was measured in the lung, heart/spine and diaphragm compartments of a validated chest phantom using various tube voltages and amounts of Cu filtration. The CNR was derived as a function of air kerma at the CR plate and with the effective dose. As rib contrast can interfere with detection of nodules in chest radiography, a tissue-to-rib ratio (TRR) was derived to investigate which tube voltages suppress the contrast of rib. Although processing algorithms affect the signal and noise in a way that is hard to predict, we found that, for a given set of processing parameters, the CNR was related to the plate air kerma and effective dose in a logarithmic manner (all R(2) >or=0.97). For imaging of the lung region, a low voltage (60 kVp) produced the highest CNR, whereas a high voltage (125 kVp) produced the highest TRR. In the heart/spine region, 80-125 kVp produced the highest CNR, while in the diaphragm region 60-90 kVp produced the highest CNR. For chest radiography with this CR system, the optimal tube voltage depends upon the region of interest. Of the filters tested, a 0.1 mm Cu thickness was found to provide a statistically significant increase in the CNR in the diaphragm region with tube potentials of 60 kVp and 80 kVp, without affecting the CNR in the other anatomical compartments.

A method to optimize the processing algorithm of a computed radiography system for chest radiography

A test methodology using an anthropomorphic-equivalent chest phantom is described for the optimization of the Agfa computed radiography "MUSICA" processing algorithm for chest radiography. The contrast-to-noise ratio (CNR) in the lung, heart and diaphragm regions of the phantom, and the "system modulation transfer function" (sMTF) in the lung region, were measured using test tools embedded in the phantom. Using these parameters the MUSICA processing algorithm was optimized with respect to low-contrast detectability and spatial resolution. Two optimum "MUSICA parameter sets" were derived respectively for maximizing the CNR and sMTF in each region of the phantom. Further work is required to find the relative importance of low-contrast detectability and spatial resolution in chest images, from which the definitive optimum MUSICA parameter set can then be derived. Prior to this further work, a compromised optimum MUSICA parameter set was applied to a range of clinical images. A group of experienced image evaluators scored these images alongside images produced from the same radiographs using the MUSICA parameter set in clinical use at the time. The compromised optimum MUSICA parameter set was shown to produce measurably better images.

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.

Computed and conventional chest radiography: A comparison of image quality and radiation dose

The aim of this study was to compare the image quality and entrance skin dose (ESD) for film-screen and computed chest radiography. Analysis of the image quality and dose on chest radiography was carried out on a conventional X-ray unit using film-screen, storage phosphor plates and selenium drum direct chest radiography. For each receptor, ESD was measured in 60 patients using thermoluminescent dosemeters. Images were printed on 35 x 43 cm films. Image quality was assessed subjectively by evaluation of anatomic features and estimation of the image quality, following the guidelines established by the protocols of the Commission of the European Communities. There was no statistically significant difference noted between the computed and conventional images (Wilcoxon rank sum test, P > 0.05). Imaging of the mediastinum and peripheral lung structures were better visualized with the storage phosphor and selenium drum technique than with the film-screen combination. The patients' mean ESD for chest radiography using the storage phosphor, film-screen combination and selenium drum was 0.20, 0.20 and 0.25 mGy, respectively, with no statistically significant difference with P > 0.05 (chi(2) tests).

Comparison of a digital flat-panel versus screen–film, photofluorography and storage-phosphor systems by detection of simulated lung adenocarcinoma lesions using hard copy images

The purpose of this study was to compare hard copy images from a flat-panel detector digital radiography system with conventional radiography, photofluorographic radiography and storage phosphor radiography for the detection of simulated lung adenocarcinoma lesions and also for radiation dose. To test the diagnostic performance of these four systems, the authors used 15 types of lung adenocarcinoma phantom according to Noguchi's classification and an anthropomorphic chest phantom. The visual evaluation of tumour detectability by four radiologists and two general thoracic surgeons was examined with a five-level confidence scale. Lung doses were measured with glass dosemeters for the chest radiology systems under the conditions used by each hospital and centre. Our results indicated that flat-panel detector digital radiography and storage phosphor radiography are not necessarily superior to conventional radiography and photofluorographic radiography for detecting lung adenocarcinomas when only hard copy images are used, and this suggests a need to carefully optimize chest radiography.

Comparison of eight different digital chest radiography systems: variation in detection of simulated chest disease

OBJECTIVE

In a short period, a variety of technically different digital radiography chest systems have become available for clinical use. Our purpose was to assess the diagnostic performance of eight different digital radiography chest systems for detection of simulated chest disease under clinical conditions.

MATERIALS AND METHODS

Assessed were four different flat-panel detector systems, two different charge-coupled device systems, one selenium-coated drum, and one storage phosphor system. For each system, 10 chest images of an anthropomorphic chest phantom were obtained. Each image contained one to 12 simulated chest lesions. Eight radiologists performed soft-copy interpretations. Entrance dose was measured and effective dose calculated. A semi-parametric logistic regression model was used for statistical analysis.

RESULTS

Statistically significant differences were found in the diagnostic performance of the eight digital chest systems (p = 0.01). Best performance was observed with the charge-coupled device system with slot-scan technology, yielding a sensitivity of 46% (132 of 288) lesions detected. The performance of three flat-panel detectors and the selenium-drum system was not significantly different from the slot-scan charge-coupled device system. Fewer lesions were detected with the storage phosphor system than with all other digital technologies, with a sensitivity of 34% (99 of 288) lesions detected, slot-scan charge-coupled device system versus storage phosphor system, p < 0.001. The effective dose varied among the digital systems.

CONCLUSION

We found differences in diagnostic performance among the eight different digital chest systems. Differences in detection rates are predominantly explained by detector design.

Investigation of optimum energies for chest imaging using film-screen and computed radiography

The purpose of the study was to compare the image quality of film-screen (FS) and computed radiography (CR) for adult chest examinations across a range of beam energies. A series of images of the CDRAD threshold contrast detail detection phantom were acquired for a range of tube potential and exposure levels with both CR and FS. The phantom was placed within 9 cm of Perspex to provide attenuation and realistic levels of scatter in the image. Hardcopy images of the phantom were scored from a masked light-box by two scorers. Threshold contrast indices were used to calculate a visibility index (VI). The relationships between dose and image quality for CR and for FS are fundamentally different. The improvements in VIs obtained using CR at 75 kVp and 90 kVp were found to be statistically significant compared with 125 kVp at matched effective dose levels. The relative performance of FS and CR varies as a function of energy owing to the different k-edges of each system. When changing from FS to CR, the use of lower tube potentials may allow image quality to be maintained whilst reducing effective dose. A tube voltage of 90 kVp is indicated by this work, but may require clinical verification.

Chest radiography with a digital flat-panel detector: experimental receiver operating characteristic analysis

PURPOSE

To evaluate the influence of different detector radiation doses and peak kilovoltage settings on diagnostic performance and radiation dose at posteroanterior (PA) chest radiography performed with an amorphous silicon flat-panel detector (FPD).

MATERIALS AND METHODS

All examinations were performed by using a digital FPD. PA chest radiographs of an anthropomorphic chest phantom were obtained with detector radiation doses of 2.50 microGy (system speed, 400), 1.56 microGy (speed, 640), and 1.25 microGy (speed, 800) and with peak kilovoltage values of 100, 120, and 140 kVp. Four types of simulated lesions-nodules of different sizes, polylobulated lesions, interstitial-nodular lesions, and interstitial-reticular lesions-were superimposed on the phantom. After four radiologists assessed all of the images, receiver operating characteristics analysis was performed. In addition, the entrance surface dose was measured and the effective dose was calculated.

RESULTS

Reduced detector dose led to significantly decreased diagnostic performance in overall lesion detection (P <.05). However, over pulmonary areas only, this effect could not be seen. With use of the same kilovoltage values, reducing the detector dose, even to 1.25 microGy (speed, 800), did not lead to significantly decreased lesion detectability. In terms of diagnostic performance and effective dose, 120 kVp was the most effective.

CONCLUSION

Standard PA chest radiographs should still be acquired at a detector dose of 2.50 microGy (speed, 400) with 120 kVp to yield the highest diagnostic performance. However, when the present analysis was focused on the lung fields only, no significant loss in diagnostic performance could be demonstrated, even after a 50% reduction in radiation dose.

State-of-the-art screening for lung cancer (part 1): the chest radiograph

The chest radiographic methods used in prior studies of lung cancer screening and in current prospective clinical trials of lung cancer screening do not incorporate, as part of their prospective design, the newer methods available for the detection of lung nodules. DR, image processing, ES, and CAD have been shown to enhance lung nodule detection. TS is a promising method but with less supporting data currently available. These techniques, alone or in combination, do not equal the nodule detection capability of lung CT, but they are likely to benefit patients having CXRs for other clinically indicated purposes and when the detection of a nodule is incidental to the clinical indication for the radiographic study.

Comparison of liquid crystal versus cathode ray tube display for the detection of simulated chest lesions

The purpose of the study was to compare the detection performance of a cathode ray tube (CRT) monitor versus a liquid crystal display (LCD) monitor for simulated subtle pulmonary lesions. Ten templates containing simulated lung lesions were superimposed on an anthropomorphic chest phantom. Posteroanterior radiographs were obtained using flat panel technology and were displayed on a CRT and an LCD monitor. Image processing and reading conditions were equivalent for both softcopy displays. Five observers assessed lesion detectability using receiver-operating characteristic (ROC) methodology. A multivariate test (Pillai trace) was used to test the significance of differences (P<0.05). The multivariate test revealed significantly different detection rates for the lesion types, but no significant difference between the two display modes. Detection performance for both monitors was higher for nodules and micro-nodules and lower for lines and patchy opacities. Analysis of lesion subgroups according to their location in lucent/obscured lung areas was also not statistically significant. Under ideal reading conditions, CRT and LCD displays perform equivalently for the detection of simulated subtle pulmonary lesions.

Impact of resolution and noise characteristics of digital radiographic detectors on the detectability of lung nodules

One of the unanswered questions in digital radiography is the connection between physical image quality metrics and clinical detection performance. In this paper, we examine the impact of two physical metrics, resolution and noise, on the detectability of nodules in a pulmonary background for specific digital radiographic detectors. A detection experiment was performed on a simulated image set using anatomical backgrounds from a high-quality lung radiograph and three different simulated nodule sizes (2-3.5 mm). The resolution and noise of the resulting images were modified using existing routines to simulate a selenium-based and a cesium iodide-based flat-panel detector at comparable exposures. A location-known-exactly (LKE) observer performance experiment was performed in which four experienced chest radiologists and three physicists specializing in chest radiology scored the images. The data from the observer experiment were analyzed by receiver operating characteristic (ROC) methodology. The detectability, as measured by the parameter Az, was higher for the selenium detector than the cesium iodide detector for all nodule sizes by an average of 8.5%. For one nodule size (2.75 mm), the difference between detectors was statistically significant (p < 0.01). The findings indicate that for the particular task studied, the superior resolution performance of the selenium-based detector provided better detectability of subtle lung nodules even though the images had greater noise than images obtained with the cesium iodide detector.

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.

Comparison of indirect CsI/a:Si and direct a:Se digital radiography. An assessment of contrast and detail visualization

PURPOSE

To assess and quantify the image quality at two dose levels for an amorphous Silicon (a:Si) Cesium Iodide (CsI) flat panel system compared with a direct amorphous Selenium (a:Se) digital radiography system.

MATERIAL AND METHODS

A contrast detectability test was performed employing the CDRAD-phantom at mAs-values leading to approximately equal phantom entrance doses of 41.4, 57.9, 75.1 and 120.8 micro Gy for the a:Se and 39.9, 58.4, 75.6 and 117.9 micro Gy for the CsI system. Images were presented to 4 independent observers. For quantitative comparison, the image quality figure (IQF) was calculated. Statistical analysis was performed using Pearson's correlation and the Wilcoxon test. A ROC-analysis was performed employing the TRG-phantom in a high- and a low-dose setting leading to entrance doses of 126.2 and 35 micro Gy for the direct, and 125.9 and 34.4 micro Gy for the indirect system. Statistical significance was evaluated using the Wilcoxon test.

RESULTS

The flat panel a:Si digital system provided superior results compared with the a:Se drum digital system with respect to low-dose settings for CDRAD-phantom and ROC-analysis, ensuring a better image quality with respect to contrast and detail detectability. Higher-dose settings provided similar results for both systems.

CONCLUSION

Image quality of a:Si flat panel digital radiography proved to be superior to a:Se drum digital radiography using low-dose settings. If the primary target is dose reduction indirect flat panel technology should be used.

Detection of simulated chest lesions by using soft-copy reading: comparison of an amorphous silicon flat-panel-detector system and a storage-phosphor system

PURPOSE

To compare observer performance by using soft-copy images produced by an amorphous silicon flat-panel-detector system and a storage-phosphor system for the detection of simulated chest lesions.

MATERIALS AND METHODS

To test the diagnostic performance of these two systems, four types of simulated lesions (nodules, micronodules, lines, and reticular opacities) were superimposed over an anthropomorphic chest phantom. Digital chest radiographs were acquired with amorphous silicon flat-panel-detector (3-K [K = 1,000] matrix, 12 bits) and storage-phosphor radiography (4-K matrix, 10 bits). Six board-certified radiologists evaluated soft-copy images on a high-resolution video monitor (2,048 x 2,560 x 8 bits). A total of 14,400 observations were analyzed in terms of receiver operating characteristics.

RESULTS

Average performance in terms of nodule detection was significantly better (P <.05) with the flat-panel-detector system than with the storage-phosphor system. For micronodules, lines, and reticular opacities, no significant detection differences in averaged performance were found between the two detector systems.

CONCLUSION

In the evaluation of soft-copy images, the amorphous silicon detector system appears to be superior to the storage-phosphor system for the detection of pulmonary nodules.

Detection of pulmonary edema in pigs: storage phosphor versus amorphous selenium-based flat-panel-detector radiography

PURPOSE

To compare diagnostic accuracy of soft-copy selenium-based digital radiographic images and soft-copy computed radiographic images obtained for detection of pulmonary edema in pigs.

MATERIALS AND METHODS

Oleic acid was injected intraatrially into three pigs (weight, 20-25 kg) at doses of 0.04, 0.05, and 0.06 mL/kg to induce pulmonary edema. Thirty-seven sets of computed radiographic, digital radiographic, and thin-section computed tomographic (CT) scans were obtained every 20-30 minutes in three pigs over 4-6 hours. Images were masked for identity, randomly sorted, and displayed on a monitor. Four radiologists rated each image for presence of parenchymal opacities by using a dichotomous scoring system in two sessions. Presence of pulmonary edema was determined with thin-section CT and a severity scale. Intra- and interobserver variations were determined with the kappa statistic and the Z test and with the Cochran Q test and the McNemar test, respectively. True-positive, true-negative, false-positive, and false-negative rates were determined. McNemar test was used to determine statistical significance of differences in detection between computed and digital radiographic images.

RESULTS

There was no significant intra- or interobserver variation, except for one pair of observers during the first interpretative session with computed radiographic images (P =.016, McNemar test). Overall sensitivity (92.1%) and diagnostic accuracy (90.2%) of digital radiography were significantly higher than those of computed radiography (79.6% and 83.4%, respectively) (P <.001 for sensitivity, P =.01 for diagnostic accuracy, McNemar test). In detection of minimal and mild pulmonary edema, sensitivity of digital radiography (84%) was significantly higher than that of computed radiography (58%) (P <.001).

CONCLUSION

Soft-copy digital radiographic images are superior to soft-copy computed radiographic images obtained for detection of mild pulmonary edema in pigs.

Digital chest imaging: selenium radiography versus storage phosphor imaging. Comparison of visualization of specific anatomic regions of the chest

RATIONALE AND OBJECTIVES

To compare selenium- versus phosphor-based digital chest imaging for visualization of various anatomic regions of the chest.

METHODS

Thirteen observers analyzed pairs of posteroanterior (PA) and lateral chest radiographs of 63 patients. One radiograph in each pair was obtained with a digital selenium chest radiography system, and the other with a storage phosphor-based technique. Each observer rated the visibility and the radiographic quality of 21 anatomic regions.

RESULTS

The observers rated visualization obtained with the selenium system as better than that obtained with the storage phosphor system in 12 anatomic regions (right lower lobe, retrodiaphragmatic, upper lobes, minor fissure, hilum, carina, azygoesophageal recess, ribs, soft tissue, upper mediastinum on the PA image, and major fissure and sternum on the lateral image). Five regions were equally appreciated (retrocardiac on the PA, lower lobes, lingual-middle lobe, soft tissue, and subdiaphragmatic region on lateral images). Four regions were rated better on phosphor imaging than on selenium films (thoracic spine on PA, upper lobes, lower, and upper thoracic spine on lateral films) (17,199 observations, P < 0.05, sign test).

CONCLUSIONS

On PA images the digital selenium chest system provides better visualization of most anatomic structures than the phosphor system. Lateral images show an almost equal preference.

Selenium-based digital radiography versus high-resolution storage phosphor radiography in the detection of solitary pulmonary nodules without calcification: receiver operating characteristic curve analysis

OBJECTIVE

The purpose of this study was to compare selenium-based digital radiography with high-resolution storage phosphor radiography for the detection of solitary pulmonary nodules without calcification.

MATERIALS AND METHODS

One hundred twenty-four patients underwent selenium-based digital radiography, high-resolution storage phosphor radiography, and chest CT for evaluation of pulmonary nodules. Thirty-one patients with pulmonary nodules smaller than 3 cm in diameter and 40 patients with normal lungs were selected for receiver operating characteristic curve analysis. Five board-certified radiologists who were unaware of the CT results independently reviewed each of the hard copies of selenium-based digital radiography and storage phosphor radiography, identified pulmonary nodules, and graded their confidence for the presence of each nodule. For each radiologist, we calculated the areas under the receiver operating characteristic curve (AUC) for selenium-based digital radiography and storage phosphor radiography.

RESULTS

The average performance of selenium-based digital radiography (AUC = 0.72) was higher than that of high-resolution storage phosphor radiography (AUC = 0.64), which is statistically significant (p <0.05).

CONCLUSION

Our results indicate that selenium-based digital radiography is superior to high-resolution storage phosphor radiography for detecting solitary pulmonary nodules without calcification.

Digital selenium radiography: detection of subtle pulmonary lesions on images acquired with and without an additional antiscatter grid

OBJECTIVE

the objective of this ROC-study was to evaluate the diagnostic efficacy of images acquired with a grid in digital selenium radiography compared to that on images obtained with the integrated air gap only.

MATERIALS AND METHODS

seven types of simulated lesions were superimposed onto an anthropomorphic chest phantom. Selenium radiography images were obtained either with or without an additional antiscatter grid. For images acquired with a grid either a similar or increased exposure level was used. Both normal and obese patients were simulated.

RESULTS

When a grid was used with an equivalent detector dose and a higher exposure, diagnostic performance was significantly improved as compared to images obtained with only the air gap. ROC curve areas for mediastinal nodules and catheters were substantially higher for images acquired with a grid and the same exposure level compared to images obtained without a grid. However, detection of linear, net-shaped and reticulonodular structures in peripheral lung regions was significantly worse when a grid was used with an equivalent exposure level. Concerning the interpretation of images obtained from the normal and obese phantom models, no substantial differences were observed.

CONCLUSION

a marked improvement in diagnostic performance could be achieved by means of the use of an additional antiscatter grid and an equivalent detector dose. However, when the same exposure was used, images acquired with the grid allowed a better detection of mediastinal structures although a worse performance was evident in radiolucent lung regions. Therefore, the routine use of a grid without increased exposure is not recommended.

Digital chest radiography with a selenium-based flat-panel detector versus a storage phosphor system: comparison of soft-copy images

OBJECTIVE

We compared the soft-copy images produced by a digital chest radiography system that uses a flat-panel X-ray detector based on amorphous selenium with images produced by a storage phosphor radiography system for the visualization of anatomic regions of the chest.

MATERIALS AND METHODS

Two chest radiologists and two residents analyzed 46 pairs of posteroanterior chest radiographs on high-resolution video monitors (2560 x 2048 x 8 bits). In each pair, one radiograph was obtained with a storage phosphor radiography system, and the other radiograph was obtained with a selenium-based flat-panel detector radiography system. Each pair of radiographs was obtained at the same exposure settings. The interpreter rated the visibility and radiographic quality of 11 different anatomic regions. Each pair of images was ranked on a five-point scale (1 = prefer image A, 3 = no preference, 5 = prefer image B) for preference of technique. Statistical significance of preference was determined using the Wilcoxon's signed rank test.

RESULTS

The interpreters had a statistically significant preference for the selenium-based radiography system in six (unobscured lung, hilum, rib, minor fissure, heart border, and overall appearance) of 11 anatomic regions (p<0.001) and for the storage phosphor system in two regions (proximal airway and thoracic spine) (p<0.05). Chest radiologists strongly preferred selenium-based images in eight regions, and they did not prefer storage phosphor images in any region.

CONCLUSION

The soft-copy images produced by the selenium-based radiography system were perceived as equal or superior to those produced by the storage phosphor system in most but not all anatomic regions.

Digital selenium radiography: anti-scatter grid for chest radiography in a clinical study

The purpose of this study was to evaluate the diagnostic performance of an additional stationary anti-scatter grid in digital selenium radiography (DSR) compared with images acquired with only an air gap. Chest radiographs were obtained with DSR in 100 patients with and without an anti-scatter grid. Four observers scored 12 anatomical landmarks, catheters and wire cerclages for their visualization in both subsets of images. Statistical analysis was performed using a paired t-test. Anatomical landmarks, catheters and wire cerclages were statistically better visualized in regions of high attenuation when the images were performed with an anti-scatter grid. No statistically significant difference was noted for peripheral regions, nor for sex and weight of the patient between the two modalities. Therefore, an anti-scatter grid is not recommended for chest radiography as it increases the radiation exposure of patients without having a significant impact on visualization for all regions of the chest.

Selenium-based digital radiography in the detection of bone lesions: preliminary experience with experimentally created defects

PURPOSE

To compare the diagnostic performance of selenium-based digital radiography with that of conventional screen-film radiography and storage phosphor radiography for the detection of bone lesions simulating osteolyses.

MATERIALS AND METHODS

Artificial osseous lesions 1.0-3.0 mm in diameter were created in 80 of 160 predefined regions in 16 porcine femoral specimens. Specimens were enclosed in containers filled with paraffin to ensure accurate repositioning and to obtain an absorption condition comparable to that of a human extremity. Imaging was performed with a selenium-based digital radiography system, a conventional screen-film system, and a storage phosphor radiography system with an exposure identical to that used during clinical imaging. The presence of a lesion was assessed with a five-point confidence scale. Receiver operating characteristic (ROC) analysis was performed for a total of 1,440 observations (480 per modality), and diagnostic performance was estimated with the area under the ROC curve (A(z)). Differences in diagnostic performance were assessed with the paired Student t test.

RESULTS

ROC analysis results showed A(z) values of 0.656 for selenium-based digital radiography, 0.679 for storage phosphor radiography, and 0.680 for conventional screen-film radiography. Differences between the three modalities were not significant (P =.60-.93).

CONCLUSION

Image quality with selenium-based digital radiography was comparable to that with conventional screen-film radiography and storage phosphor radiography.

Chest radiography with a large-area detector based on cesium-iodide/amorphous-silicon technology: image quality and dose requirement in comparison with an asymmetric screen-film system

The purpose of this study was to evaluate a large-area, flat-panel X-ray detector, which uses cesium-iodide (CsI) and amorphous silicon (a-Si). Conventional images were compared with digital images acquired with equal dose (2.5 microGy) and with 50% dose reduction. Fifteen consecutive patients were studied prospectively using an asymmetric screen-film system (detector dose, 2.5 microGy). Digital images were taken from the same patients in a posteroanterior view with detector doses of 2.5 and 1.25 microGy, respectively. The CsI/a-Si active-matrix imager had a panel-size of 43 x 43 cm, a matrix of 3 x 3k, and a pixel-pitch of 143 microm. Hard copies were presented in a random order to eight independent observers, who rated image quality according to six subjective quality criteria. Statistical significance of differences was evaluated with Student's t test for paired samples (confidence level, 95%). Digital radiographs with 2.5 and 1.25 microGy were superior to conventional images regarding all quality criteria. Statistically significant differences were observed for five of six criteria at a detector dose of 2.5 microGy and for only one quality feature at 1.25 microGy. Flat-panel digital imagers based on CsI/a-Si technique have the potential to replace conventional systems and might allow a reduction of radiation dose by 50% without loss of image quality.

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

OBJECTIVE

The objective of this study was to compare the diagnostic performance of a digital large-area silicon flat-panel detector with that of a conventional screen-film system in clinical chest imaging using abnormal findings documented by CT as the reference standard.

SUBJECTS AND METHODS

Eighty patients (46 men and 34 women; age range,18-91 years; mean age, 63 years) who underwent CT of the chest were examined with the new digital radiography system, which is based on a 43 x 43 cm silicon flat-panel detector, and with a conventional screen-film system, which is used routinely in clinical practice. Posteroanterior and lateral radiographs were obtained. Four radiologists analyzed the digital and conventional images separately for chest abnormalities and rated the images using a five-level scale of confidence; CT was used as the reference standard. Diagnostic value was assessed using receiver operating characteristic curves for each abnormality.

RESULTS

No significant differences were found between the area under the receiver operating characteristic curve of the digital and that of the conventional radiography method for almost all investigated criteria. The only exception was mediastinal abnormalities, for which the digital method provided better results than the conventional method (p < 0.05).

CONCLUSION

The diagnostic performance of the new large-area silicon flat-panel detector is equivalent or superior to that of the conventional screen-film system for clinical chest imaging and can replace conventional radiography systems. This new technology offers transmission and storage possibilities inherent to digital radiology that would facilitate daily practice and reduce the initial high costs in the long-term.

Pelvic imaging with a selenium-based detector (Thoravision). Comparison with screen-film radiography in 75 patients

OBJECTIVE

To evaluate whether the selenium detector (Thoravision) provides sufficient diagnostic confidence in digital pelvic imaging compared with a conventional screen-film combination.

METHODS

In 75 patients, pelvic imaging with conventional screen-film and isodose selenium radiography using a dedicated postprocessing mode was compared independently by three radiologists. The depiction of cortical and cancellous bone was evaluated in the iliac wings, sacral and pubic bones, acetabulum, femoral head, and trochanter. Demarcation of soft tissue was assessed in the iliac and trochanteric region.

RESULTS

Visualization of cortical bone and soft tissue in the iliac area as well as soft tissue and cortical and cancellous bone in the trochanteric region was significantly superior with the selenium detector. However, conventional imaging was better in the trabecular bone of the sacral region, where results with the selenium system were particularly poor.

CONCLUSIONS

The selenium detector (Thoravision) is advantageous in imaging soft tissue adjacent to the iliac wings and the trochanter, but results for the cancellous sacral bone are poor. Further modifications of postprocessing modes may lead to improved depiction of this critical pelvic area.

Detection of simulated interstitial lung disease and catheters with selenium, storage phosphor, and film-based radiography

PURPOSE

To evaluate the diagnostic performance of storage phosphor and digital selenium radiography (DSR) with asymmetric and symmetric screen-film systems at different speeds in the detection of simulated interstitial lung disease and catheters.

MATERIALS AND METHODS

Patterns of simulated interstitial lung disease and catheters were superimposed over an anthropomorphic chest phantom. Hard-copy images were generated at DSR (200-, 400-, and 600-speed), storage phosphor radiography (200- and 400-speed), and asymmetric (400-speed) and symmetric (200- and 400-speed) screen-film imaging. Surface doses were measured, and receiver operating characteristic analyses were performed.

RESULTS

No statistically significant differences were found between the detector systems with the same speeds for each interstitial pattern. Significantly poorer results were found at 600-speed DSR than at 200-speed DSR. Detection of catheters and nodules over high-attenuation areas was significantly worse with the symmetric screen-film system than with the other detectors. The surface dose with the DSR system, without a grid, was about 50% less than that of the other detector systems, with grids, at the same speed.

CONCLUSION

No significant difference was found in the diagnostic performance at DSR, storage phosphor radiography, and film-based radiography for simulated interstitial lung disease at corresponding speeds; there was a reduction in the surface dose of about 50% with the 400-speed DSR system.

Comparison between a screen-film system and a selenium radiography system. An ROC study using simulated thoracic lesions

RATIONALE AND OBJECTIVES

To evaluate the diagnostic image quality of the hard copies of a commercially available selenium detector-based computed radiography system compared to that of a conventional screen-film system.

METHODS

Ten radiographs of an anthropomorphic chest phantom with simulated nodular and linear-reticular lesions were produced using either system. Each radiograph was subdivided into 15 fields containing zero lesions, one nodular lesion, one linear-reticular lesion, or both lesions. The total of 150 fields for each modality was reviewed by six radiologists, and receiver operating analysis was performed.

RESULTS

The conventional screen-film system performed significantly better for nodular lesions, whereas no statistically significant difference was found between the detection rates of both systems for linear-reticular lesions.

CONCLUSIONS

The better detection of nodules with the dedicated selenium detector can be explained by the higher dynamic range of the system. Detection of linear-reticular lesions was slightly but not significantly better with the screen-film system, but the detection rate of the selenium detector might be further improved with a different image processing technique.

Detection of simulated chest lesions with normal and reduced radiation dose: comparison of conventional screen-film radiography and a flat-panel x-ray detector based on amorphous silicon

RATIONALE AND OBJECTIVES

The authors compared a solid-state amorphous silicon (a-Si) detector and screen-film radiography (SFR) with regard to the detection of simulated pulmonary lesions. Evaluation of the impact of a dose reduction of 50% with this digital flat-panel detector was of special interest.

METHODS

A self-scanning flat-panel detector, based on a-Si technology with 143 x 143 microm pixel size, 1 k x 1 k matrix and 12-bit digital output was used. An asymmetric state-of-the-art screen-film system was compared with a-Si images taken at the same dose as SFR-images and at a dose reduced by 50%. An anthropomorphic chest phantom was superimposed by templates containing nodules, linear structures, reticular, and micronodular opacities in a random distribution. Receiver operating characteristic analysis was performed for 23,040 observations made by four independent observers. Student's t test (95% confidence-level) was used for statistical analysis.

RESULTS

Receiver operating characteristic analysis showed that a-Si images taken at the same dose as SFR-images were significantly superior to SFR with respect to the detectability of lines (P = 0.01) and micronodular opacities (P < 0.01). For the other objects and the a-Si images taken at a reduced dose, it yielded no statistically significant differences between both imaging modalities.

CONCLUSIONS

The results of this phantom study indicate that a-Si detector technology holds promise in terms of dose reduction in chest radiography without loss of diagnostic accuracy compared with SFR.