Digital Storage Phosphor Radiography Research Articles

Should 3K zoom function be used for detection of pneumothorax in cesium iodide/amorphous silicon flat-panel detector radiographs presented on 1K-matrix soft copies?

The purpose of the study was to evaluate observer performance in the detection of pneumothorax with cesium iodide and amorphous silicon flat-panel detector radiography (CsI/a-Si FDR) presented as 1K and 3K soft-copy images. Forty patients with and 40 patients without pneumothorax diagnosed on previous and subsequent digital storage phosphor radiography (SPR, gold standard) had follow-up chest radiographs with CsI/a-Si FDR. Four observers confirmed or excluded the diagnosis of pneumothorax according to a five-point scale first on the 1K soft-copy image and then with help of 3K zoom function (1K monitor). Receiver operating characteristic (ROC) analysis was performed for each modality (1K and 3K). The area under the curve (AUC) values for each observer were 0.7815, 0.7779, 0.7946 and 0.7066 with 1K-matrix soft copies and 0.8123, 0.7997, 0.8078 and 0.7522 with 3K zoom. Overall detection of pneumothorax was better with 3K zoom. Differences between the two display methods were not statistically significant in 3 of 4 observers (p-values between 0.13 and 0.44; observer 4: p = 0.02). The detection of pneumothorax with 3K zoom is better than with 1K soft copy but not at a statistically significant level. Differences between both display methods may be subtle. Still, our results indicate that 3K zoom should be employed in clinical practice.

462 - Portal and verification imaging of electron beams by digital storage phosphor radiography

462 - Portal and verification imaging of electron beams by digital storage phosphor radiography

Quality control of storage phosphor digital radiography systems

Quality control (QC) of storage phosphor devices is important in assuring that the image information entered into an Image management and communication (IMAC) system is sufficient for diagnosis. QC of storage phosphor digital radiography systems is complex because of the self-corrective nature of the image-processing software used in these machines. Currently, one must produce hard copy to perform adequate QC. Inspection of images with reject analysis and inspection of cassettes and imaging plates has helped us in our QC program. For those QC tests using control limits, the appropriate settings for these limits are unknown. Starting approximations are given. Recommended tests are described.

Clinical application of single dual-energy subtraction technique with digital storage-phosphor radiography

We used a single-exposure dual-energy subtraction technique with a storage-phosphor computed radiography (CR) system to evaluate various pulmonary diseases. Clinical applications of this method have been studies at our institution. In our experience, the dual-energy subtraction technique provided better visualization of pulmonary nodules, tracheobronchial abnormalities, pulmonary vascular diseases, calcification in a nodule, and rib lesions than conventional CR images did. Single-exposure dual-energy subtraction images were obtained with a sandwich technique using two storage-phosphor imaging plates with a 1-mm-thick copper filter interleaved between the two. The front plate obtains a lower kilovoltage image, whereas the back plate obtains a higher kilovoltage image. We can visualize soft tissue and bone images as well as unsubtracted digital images by the subtraction process.

Storage Phosphor Digital Radiography in Portable Chest Imaging: Comparison of Image Quality with Conventional Film-Screen System with Variation of mAs

Storage Phosphor Digital Radiography in Portable Chest Imaging: Comparison of Image Quality with Conventional Film-Screen System with Variation of mAs

Subtle pulmonary nodules: detection and identification with storage phosphor radiographs and conventional chest films

To determine the value of digital storage-phosphor radiography (SR) on the detection and identification of subtle lung nodules, postero-anterior (PA) and lateral (LAT) film-screen (FR) chest radiographs were compared with isodose SR images of 45 patients with metastatic malignancies. The SR postprocessing was done with a particular mode previously optimized for routine chest radiography. Pulmonary metastases were found in 34 patients and were proved or excluded by CT (n = 28) or longterm follow-up FR (n = 17). Chest images were divided into four regions for evaluation of image quality, number of lung nodules per region and marked pulmonary structures by receiver-operating characteristics (ROC) analysis (45 patients; 125 nodules; 2810 observations; five readers). Of the nodules selected for an ROC study 82 % were 0.5–1.0 cm in diameter. Overall image quality was rated better for FR concerning lung fields (PA) and mediastinum/hilum (LAT). More lung-field nodules were detected on FR than on SR chest images (P < 0.05). Use of FR was superior to SR in the general identification of nodules (PA chest), especially concerning intermediate (P < 0.01) and subtle abnormalities (P < 0.05), whereas there was no significant difference for LAT chest images. Our results show, that currently FR still has advantages over SR in the detection and identification of subtle lung nodules in routine clinical radiography.

Digital storage phosphor radiography for treatment verification in radiotherapy.

The potential of digital storage phosphor radiography (SR) to improve image quality of portal radiographs is evaluated. Conventional film radiographs (FR) and corresponding SR verification images of an anthropomorphic phantom and various irradiation ports of patients were obtained with high-energy photon beams. For both techniques conventional films and storage phosphor screens were placed into a cassette with steel screens. Images were evaluated according to contrast and spatial resolution, delineation of anatomical structures, position of shielding blocks and accuracy of field alignments. Evaluation of 33 pairs of SR and FR portal images yielded a superior contrast resolution of SR in 47% (contrast air-soft tissue) and 37% (bone-soft tissue). Thus SR allows quick and easy detectability of anatomical structures as well as a better definition of block positions and field alignments. Shorter exposure times for computed images may result in a reduction of motion artefacts. SR images are indispensable in modern radiation therapy units, as they are instantly available in a computerized network for further image processing and analysis.

Digital imaging of the chest in newborns: influence of radiation exposure on image quality

In order to evaluate the influence of radiation exposure on image quality in digital storage phosphor radiography, 200 digital storage phosphor chest radiographs, obtained on a neonatal Intensive Care Unit, and the same number of conventional screen-film radiographs (speed 250) were assessed for the visibility of anatomical structures and catheters. The same exposure parameters were used in both groups. Normal variations of radiation exposure under free exposure conditions were estimated in all digital images using a formula calculating radiation dose in the screen-plane from image sensitivity, latitude and average grey value of the right lung. There was already a significant (P < 0.001) decline in image quality in the digital images with a 30–50% reduction in radiation exposure, which was most severe for structures such as trachea, retrocardiac space, lung texture and low-contrast catheters. Compared with optimally exposed conventional images, only those digital images with a slightly higher than normal dose had an equivalent image quality.

Dosisbestimmung bei der Speicherfolienradiographie

For digital storage phosphor radiography systems a linear relationship exists between the digital gray-level measured at the workstation and the logarithm of the dose (air kerma) in the screen plane. Parameters of this relationship are the S factor (amplification factor) and L factor (logarithmic dose range) and an energy dependent factor P. A formula is presented for calculation of radiation dose in screen plane. P values for different kVp have been experimentally determined.

Interstitial lung disease: impact of postprocessing in digital storage phosphor imaging.

The ability to resolve the fine linear structures of interstitial lung disease is one measure of the limiting performance characteristics of an imaging system. Conventional screen-film radiography was compared with six algorithms of isodose storage phosphor digital radiography (0.2-mm x 10-bit pixel matrix) in the detection of interstitial lung abnormality documented by means of computed tomography in 40 patients with abnormalities and 25 healthy control subjects. Performance was evaluated with an analysis of variance (the Fisher paired comparison test; P less than .05) of the average receiver operating characteristic area of 2,730 observations by six readers. The moderately and the more markedly high-frequency edge-enhanced algorithms of storage phosphor digital radiographs were equivalent in performance to screen-film radiography. The default mode, low- and medium-frequency edge-enhanced algorithms, and gray scale reversed mode of storage phosphor digital radiography were inferior to screen-film radiography. The authors conclude that high-frequency edge-enhanced algorithms can perform as well as screen-film radiography in the detection of interstitial disease.

Detection of bullous lung disease: conventional radiography vs digital storage phosphor radiography.

The detection of fine linear contours and altered aeration are requirements for the radiologic diagnosis of bullous lung disease and are severe measures of the spatial and contrast resolution of chest imaging systems. We compared plain film radiography with five postprocessing algorithms of storage phosphor digital radiography (2144 x 1744 x 10 bit matrix with 0.2-mm pixel size) in the detection of CT-proved bullous lung disease (35 patients and 25 normal control subjects). Receiver-operating-characteristic analysis of 2160 observations by six interpreters was done to evaluate the observers' performance. By analysis of variance (p less than .05), we found that the default digital algorithm and the three edge-enhancing algorithms of high and medium frequencies performed less well than plain films did, but the differences fell short of statistical significance. Gray-scale reversal was the only digital algorithm that performed significantly less well than plain films did. We conclude that any differences between digital algorithms and plain films in the detection of bullous lung disease were too small to be detected in this study. Any difference between the two methods in providing clinically important, diagnostic information is likely to be insignificant.

Mediastinal abnormalities: detection with storage phosphor digital radiography.

Conventional film radiography (FR) and six postprocessing algorithms of isodose storage phosphor digital radiography (SR) (0.2-mm X 10-bit pixel matrix) were compared in the evaluation of 40 mediastinal and 30 pulmonary lesions in 60 patients who underwent computed tomography of the chest. The six SR algorithms varied among each other in only one image parameter. One algorithm approximated conventional image characteristics. The other five algorithms were designed to optimize imaging of the mediastinum and tested the effects of gray-scale reversal, adjustment of optical density, a linear instead of a sigmoid gradation curve, and moderate edge enhancement of high and medium spatial frequencies. Performance was evaluated by calculating the average area under the receiver operating characteristic curve (Az) of 5,040 observations by six readers. Post-processing with high-frequency edge enhancement and density optimization for the mediastinum significantly improved performance of SR over FR in the detection of mediastinal lesions (Az = .80 +/- .02 vs .73 +/- .01, respectively). Gray-scale reversal significantly decreased performance (Az = .64 +/- .03). All SR algorithms that were postprocessed to optimize imaging of the mediastinum were significantly inferior to FR in the detection of pulmonary lesions.

Storage-phosphor digital radiography in genitourinary radiology

A digital-projection radiography system with potential applications in genitourinary imaging is presented. The system replaces the traditional film-screen combinations by storage phosphor screens but continues to use cassettes in conventional X-ray equipment. Technical features such as consistently optimal image brightness and contrast across an extremely wide exposure range and edge-enhancement capabilities overcome deficiencies seen with conventional film-screen systems, such as improper exposure and poor contrast discrimination. Images obtained with a dual-energy radiation spectrum selectively demonstrate soft-tissue- or bone-equivalent structures and diminish the obscuring effect of bowel gas. Problems resulting from the singular reliance on film as a display and storage medium in conventional radiography are resolved in digital radiography by fast and simultaneous electronic access to images that can be displayed on high-resolution monitors or laser-printed films. The basic technical features of storage-phosphor digital imaging as compared to conventional radiography are described. A summary of recently published results relevant to genitourinary examinations is given and radiographic examples are presented.

Screening for Asbestos-Related Pleural Disease with Digital Storage Phosphor Radiography

Digital storage phosphor radiography (SR) has a wide dynamic range and unique postprocessing capabilities that may improve the performance of screening studies for asbestos-related pleural disease compared with conventional film radiography (FR). In a group of 32 asbestos-exposed and nine control subjects with established pleural data, we compared the screening performance of FR and SR obtained with a single isoexposure, dual-energy technique (system resolution 0.2 mm, 10 bits). Performance was evaluated for 7320 observations by eight readers using a paired t test (P less than .02 with Bonferroni correction) of averaged receiver operating characteristic curve (ROC) areas (Az +/- standard error). We found that SR alone and SR supplemented by dual-energy soft-tissue and calcium images (SRde) were superior to FR in the overall detection of pleural abnormalities (Az = 0.90 +/- 0.01, 0.90 +/- 0.01, and 0.88 +/- 0.01, respectively). In the specific detection of pleural calcification, SRde was superior to FR (Az = 0.91 +/- 0.01 and 0.87 +/- 0.01, respectively; P less than 0.01). Analysis of variance indicated that SRde most closely reproduced an established pleural score based on the International Labor Organization (ILO) classification of the pneumoconioses (P less than 0.05, Scheffé's multiple comparison test). We conclude that isodose SR performs at least as well as FR in screening for asbestos-related pleural disease. SR supplemented by dual-energy images might improve the specific detection of pleural calcifications compared with FR.

Digital storage phosphor imaging versus conventional film radiography in CT-documented chest disease.

The advantages of imaging the chest with digital storage phosphor radiography (SR) may be nullified by its spatial resolution, which is lower than that of conventional film radiography (FR). To test the reader detection performance with the two modalities under clinical conditions, the authors compared 140-kVp isoexposure SR (system resolution: 0.2 mm, 10 bits) and FR images of a variety of chest abnormalities proved by computed tomography (CT) (157 patients, 244 abnormalities, 5,652 observations, six readers). In all tests, SR was as good as or better than FR (P less than .05). In overall detection, indicated by the average area of receiver operating characteristics, SR and FR were equivalent. SR was superior for mediastinal lesions and for pulmonary opacities greater than 2 cm in diameter. For all other types of pulmonary lesions and pleural abnormalities, SR and FR were equivalent. Currently available commercial SR systems can replace film radiographic systems in the detection of a wide variety of chest lesions. SR is likely to enable better visualization than FR in the detection of mediastinal and large pulmonary abnormalities.