Volume detection threshold: quantitative comparison of computed radiography and screen-film radiography in detection of pneumothoraces in an animal model that simulates the neonate

Neonatal Chest Computed Radiography: Image Processing and Optimal Image Display

OBJECTIVE

The purpose of this study was to determine soft-copy image display preferences of brightness, latitude, and detail contrast for neonatal chest computed radiography to establish a baseline for future work on low-dose imaging.

CONCLUSION

Observers preferred brighter images with higher detail contrast and narrow to middle latitude for soft-copy display compared with the typical screen-film hard-copy appearance. Future research on low-dose neonatal chest imaging will be facilitated by an understanding of optimal soft-copy image display.

Flat-panel display (LCD) versus high-resolution gray-scale display (CRT) for chest radiography: an observer preference study

OBJECTIVE

Our objective was to compare cathode ray tube (CRT) display with liquid crystal display (LCD) for soft-copy viewing of chest radiographs in a clinical setting.

MATERIALS AND METHODS

We displayed 80 posteroanterior digital chest radiographs side by side on a 5-megapixel CRT display and a 3-megapixel LCD. Gradation characteristics of both monitors were adjusted to DICOM display standards. Using a 4-point scale, seven radiologists ranked overall image quality and visibility of anatomic landmarks. Data analysis included Wilcoxon's rank sum test to assess the significance of preference for the different display modes and calculation of the percentage of images ranked equally by at least five of the seven radiologists.

RESULTS

Wilcoxon's rank sum test found significant preferences (p < 0.001) for the CRT display for visualization of structures in low-attenuation areas of the thorax and for the LCD for visualization of structures in high-attenuation areas of the thorax. Overall image quality was ranked equal by at least five radiologists in 70% of cases, whereas for the remaining images a significant preference was found for the CRT display.

CONCLUSION

We conclude that, under subdued ambient lighting conditions and without use of windowing, for most images the overall quality is equal with high-resolution CRT display and LCD. In images judged preferentially, we found a significant superiority for LCD for delineating mediastinal structures and for CRT display for delineating structures in the lung.

Automatic detection of foreign objects in computed radiography

This paper presents an effective two-step scheme for automatic object detection in computed radiography (CR) images. First, various structure elements of the morphological filters, designed by incorporating available morphological features of the objects of interest including their sizes and rough shape descriptions, are used to effectively distinguish the foreign object candidates from the complex background structures. Second, since the boundaries of the objects are the key features in reflecting object characteristics, active contour models are employed to accurately outline the morphological shapes of the suspicious foreign objects to further reduce the rate of false alarms. The actual detection scheme is accomplished by jointly using these two steps. The proposed methods are tested with a database of 50 hand-wrist computed radiographic images containing various types of foreign objects. Our experimental results demonstrate that the combined use of morphological filters and active contour models can provide an effective automatic detection of foreign objects in CR images achieving good sensitivity and specificity, and the accurate descriptions of the object morphological characteristics.

Computed radiography versus screen-film radiography: detection of pulmonary edema in a rabbit model that simulates neonatal pulmonary infiltrates

PURPOSE

To determine if computed radiography is equivalent to screen-film radiography in depicting pulmonary edema and to determine if radiation exposure can be reduced with computed radiography while maintaining equivalent diagnostic accuracy for pulmonary edema.

MATERIALS AND METHODS

Oleic acid was intravenously injected into three rabbits at each of four doses: 0, 0.02, 0.04, and 0.06 mL/kg. Two hours later, chest computed radiographs and screen-film radiographs were obtained at 60 kVp and 1.1 mAs. Additional computed radiographs were obtained after reducing milliampere seconds or by reducing milliampere seconds and increasing the kilovolt peak, which reduced bone marrow exposure by up to 20%. The presence of pulmonary opacities, "truth," was established by the wet-dry weight ratio and by chest computed tomography (CT). The radiographs were masked and randomized. Four observers rated the images for the presence of parenchymal opacities with a dichotomous score and judged the quality of the radiographs on a scale from 1 (worst) to 6 (best). Cochran Q tests and McNemar tests were used to analyze the differences in paired comparisons. Image quality was evaluated with logistic regression analysis.

RESULTS

There was no significant difference between truth and observer ability to detect opacity for either modality or for any exposure (P > .05). There was no significant difference between computed radiography and screen-film radiography for image quality (P > .05).

CONCLUSION

Computed radiography is equivalent to screen-film radiography in the detection of pulmonary edema. Radiation exposure reduction of 20% can be achieved without affecting pulmonary edema detection or image quality.

Clinical experiences with computed radiography

Computed radiography (CR) based on photostimulable phosphor is currently the only feasible way for a radiological department to digitize the bulk of radiological data: the lung and skeletal examinations. Regarding the quality of images for diagnostic purposes, CR imaging is never inferior to a screen/film system (SF) and for several clinical entities CR is superior. Of the many processing possibilities of the image plate (IP) image, the unsharp masking or edge enhancement should be used at a minimum. Dose reduction with CR ranges from 15% to 95%; at our institution it is 37%. Softcopy reading of CR images is advantageous due to the many postprocessing and improved display facilities. Currently there is little use for a 4000 x 4000 (4 K) pixel imaging and display. All images (including mammography) can be read in 2 K without any loss of clinically important information. To include CR in a picture archive and communication system (PACS) is demanding because of the load of data that each CR image represents. Networks for image distribution are essential if digital imaging is to have any impact on patient treatment and hospital organization.

Computed radiography in neonatal and pediatric intensive care units: a comparison of 2.5 K x 2 K soft-copy images vs digital hard-copy film

OBJECTIVE

The goal of the study was to determine whether soft-copy images on high-resolution monitors (2.5 K x 2 K) are suitable for primary interpretation of images from pediatric and neonatal intensive care units. The hypotheses were that hard and soft images yield similar diagnostic information, and that both residents and faculty radiologists can use monitors effectively. Previous reports have produced conflicting results; the need for larger sample sizes has been emphasized.

MATERIALS AND METHODS

One thousand one hundred and four images produced by computed radiography using the Kodak Ectascan Imagelink system were prospectively analyzed by two pediatric radiologists, one reading hard copy and the other soft copy of the same images. Bias was controlled by equal distribution of modalities between observers and by daily alternation of modality. Hard- and soft-copy observations of presence or absence of nine specific tubes and nine specific diagnostic findings were compared. Interobserver differences between pediatric radiologists and radiology residents were studied on additional images. The kappa statistic was used to evaluate the level of agreement for all observations.

RESULTS

There was excellent agreement between hard and soft copy interpretation for each tube and diagnostic finding (kappa values 0.93-1.0) and excellent interobserver agreement between two pediatric radiologists (kappa values 0.84-1.0). The level of agreement between radiology residents and pediatric radiologist was excellent for the most objective findings. All results were statistically significant (p < 0.001).

CONCLUSION

High resolution soft-copy images are suitable for primary interpretation in patients in pediatric and neonatal intensive care units.