ROC-analysis of detection performance by analogue and digital plain film systems in chest radiography

We have previously reported that a microcarrier-attached human hepatoma (Hep G2) cell line responds to hydrodynamic shear upon transfer to an agitated, clean, autoclaved spinner flask with a transient increase in cytochrome P450IA1 (CYPIA1) activity. Physiological changes induced by hydrodynamic stress could be problematic in the scaleup of microcarrier cultures. A better understanding of how stress alters cell physiology may assist in reactor scaleup. The induction of CYPIA1 activity was dependent on the agitation level of the cultures, and the level of CYPIA1 induction was comparable to that obtained with exposure to approximately 0.1 nM TCDD (2, 3, 7, 8-tetrachlorodibenzo-p-dioxin). It has been well documented that hydrodynamic shear stress can cause alterations in the metabolism of phospholipid membrane-bound arachidonic acid (AA) in adherent cells in a parallel plate system. The present study was carried out to determine if either AA or a metabolite of AA was involved in the induction of CYPIA1 activity in the microcarrier cultures of Hep G2 cells. Addition of exogenous AA followed by initiation of the stress resulted in an increase in the level of CYPIA1 activity. Pretreatment of the cultures with quinacrine, an inhibitor of phospholipase A2, reduced the stress-induced CYPIA1 activity. Furthermore, addition of propranolol, an inhibitor of phosphatidic acid phosphohydrolase, resulted in an increase in the response in addition to sustaining the induced enzyme activity. Pretreatment with the cyclooxygenase inhibitor, indomethacin, or the lipoxygenase inhibitor, caffeic acid, had no effect on the response, suggesting that the cyclooxygenase and lipoxygenase pathways were not involved in generating AA metabolites that alter CYPIA1 activity. The agent, nordihydroguaiaretic acid, blocks the monooxygenase pathway and blocks CYPIA1 activity increases. These observations suggest a possible mechanism where the stress on the cells induces phospholipase D, resulting in the formation of phosphatidic acid which then activates phospholipase A2, resulting in the release of AA. Further, these results are consistent with a mechanism in which the metabolism of AA, most likely through the monooxygenase pathway, results in a metabolite that by a yet unknown mechanism induced CYPIA1.     

Standardization of digital radiologic images

The need for uniform digital formats of radiologic images obtained from the human body by the various methods (CT, MRI, DF, DSA, NM) is felt by both the manufacturers and the radiologists since a long time. The ACR-NEMA standard was initially established to overcome this problem, however it was not fully satisfactory. Its up-dated version, DICOM 3 seems a more successful approach to the solution of the problem. The rationale on which DICOM 3 is based, the main guidelines with some reference to the various parts of the new standard, are analyzed. Its advantages as well as disadvantages are considered in view of a future complete integration of data and images of a radiology department within a hospital information system. In the appendix, a list of DICOM components and addresses where to find the original documentation are supplied.     

Correction of background noise in direct digital dental radiography

OBJECTIVES: To clarify the source of noise in direct digital intra-oral radiography with RVG-S (Trophy Radiologie, Vincennes, France) and to use these to develop a method for correction of background noise. METHODS: Sensor temperature, image acquisition time and X-ray dose were independently analysed with the IPLab Spectrum (Signal Analytics, Vienna, VA) software. RESULTS: The decrease in pixel value due to the dark current was linearly related to the image acquisition time. Although a variation in sensitivity was observed when the sensor was exposed to X-rays, the mean pixel value of the entire image was linearly related to the exposure time. The image showing only the signal due to X-ray dose was derived from the original RVG-S image by correcting for the dark current and the pixel-by-pixel sensitivity variation of the CCD sensor. CONCLUSION: The image formed only by X-ray dose distribution can be derived by correcting for the background noise.     

The use of digital images in pathology

Many parallel processes occur during the final stages of apoptosis. It is not clear which of these processes occur in all or most models of apoptosis and which occur only in some. In addition, the temporal relationship of these events is not always well understood. Correlated flow cytometric measurements were used to address these questions. Several models of apoptosis were studied, including thymocytes treated with dexamethasone. MOLT-4 cells treated with etoposide, U937 cells treated with anti-Fas, HL-60 cells treated with camptothecin, Raji cells grown in low serum, and aged neutrophils. All models showed a decrease in LDS-751 and fluorescein diacetate (FDA) staining, an increase in staining with dihydrorhodamine 123 (dhR123) or dihydroethidium, and an acidification of the cytoplasm. In each model, these changes were highly correlated, appearing simultaneously as multiparameter measurements. Changes in membrane status detected with merocyanin 540 (MC540) and annexin V behaved differently. A population with LDS-751 and FDA changes but without annexin V or MC540 changes could be demonstrated in some models. Several models did not show any change in annexin V binding, and HL-60 did not show a change in MC540 binding during apoptosis. The loss of cell surface antigens (CD45 and CD16) from aged neutrophils occurred in the entire LDS-751 and FDA dim population, even though other membrane changes (including the appearance of annexin V binding sites) were only apparent in a subset of these cells. These results suggest a model for the ordering of some of the terminal processes in apoptosis, with annexin V and MC540 changes trailing other events in apoptosis. These results confirm the need for caution in using a single-parameter measurement as an indicator of apoptosis for any new model being studied.     

Computed tomography, magnetic resonance imaging, and digital radiography

There are three milestones in the history of thoracic radiology. Thoracic radiology started in 1897 when Williams developed thoracic fluoroscopy and introduced the basic concepts of roentgenologic interpretation. At the same time, the first chest films were performed allowing decisive improvement in the diagnosis of many chest diseases. Continuous technical improvement is responsible for the fact that, even today, the conventional chest film remains a highly accurate and frequently used imaging modality. A third milestone was the development of digital radiography and its use in the chest. Computerised tomography changed thoracic imaging dramatically; in a first step mainly as a tool to visualise soft tissue abnormalities and, later on, also as a modality to study lung disease. The recent development of the digital chest radiograph has again added new perspectives to the approach and diagnosis of chest disease.     

The teaching of computer programming and digital image processing in radiography

The increased use of digital processing techniques in Medical Radiations imaging modalities, along with the rapid advance in information technology has resulted in a significant change in the delivery of radiographic teaching programs. This paper details a methodology used to concurrently educate radiographers in both computer programming and image processing. The students learn to program in visual basic applications (VBA), and the programming skills are contextualised by requiring the students to write a digital subtraction angiography (DSA) package. Program code generation and image presentation interface is undertaken by the spreadsheet Microsoft Excel. The user-friendly nature of this common interface enables all students to readily begin program creation. The teaching of programming and image processing skills by this method may be readily generalised to other vocational fields where digital image manipulation is a professional requirement.     

Automatic background recognition and removal (ABRR) in computed radiography images

A novel method to automatically recognize and remove background signals in computed radiography (CR) images caused by X-ray collimation during projection radiographic examinations is presented. There are three major steps in this method. In the first step, a statistical curve is derived based on many hierarchical CR sample images as a first approximation to loosely separate image and background pixels. Second, signal processing methods, including specific sampling, filtering, and angle recognition, are used to determine edges between image and background pixels. Third, adaptive parameter adjustments and consistent and reliable estimation rules are used to finalize the location of edges and remove the background. In addition, this step also evaluates the reliability of the complete background removal operation. With this novel method implemented in a clinical picture archiving and communication system (PACS) at the University of California at San Francisco, we achieved 99% correct recognition of CR image background, and 91% full background removal without removing any valid image information.     

Bounds on null functions of linear digital imaging systems

OBJECTIVE: The purpose of this investigation was to quantitatively assess abnormally low attenuation of the lung by use of three-dimensional volumetric reconstructions from routine helical CT and to assess their correlation with pulmonary function tests. MATERIALS AND METHODS: Helical CT was performed in 100 patients in full inspiration. Examination was also performed in full expiration in 53 of these patients. Three-dimensional volumetric reconstructions were performed for total lung volumes at inspiration and at expiration, with a threshold of -896 H on inspiratory CT and -790 H on expiratory CT, to quantify emphysematous change. Correlation was made with pulmonary function tests in 79 patients. RESULTS: CT volumetric assessments of abnormally low attenuation of the lung at inspiration and expiration had a high correlation (r2 = .84, p < or = .0001). In comparison with pulmonary function tests, both inspiratory low attenuation of the lung and expiratory low attenuation of the lung correlated well with the logarithm of the ratio of the forced expiratory volume in 1 sec (FEV1) to the forced vital capacity (r2 = .74, p < or = .0001 and r2 = .74, p < or = .0001, respectively) and with the percentage of predicted ratio of the FEV1 to the forced vital capacity (r2 = .69, p < or = .0001 and r2 = .69, p < or = .0001, respectively). Linear correlations were also seen with FEV1, residual volume, and forced residual capacity. CONCLUSION: Three-dimensional volumetric reconstructions of hypoattenuating lung correlate well with pulmonary function tests. In addition, inspiratory and expiratory data are also correlative, suggesting that a dedicated expiratory examination is not needed. This easily obtainable information will prove useful for patients with obstructive lung disease from emphysema, providing a measure of pulmonary function status in this population.     

Radiation exposure in abdominal radiography with digital luminescence radiography and conventional screen-film system: an experimental animal study]

Progress in the care of the critically ill patient with life-threatening infection has been hampered by inconsistent, often confusing terminology. The clinical syndrome of sepsis-familiar to all yet definable by none-describes a highly heterogeneous group of disorders with different causes and differing prognoses. The imminent availability of mediator-directed therapy has created a sense of urgency to develop better methods for delineating discrete clinical syndromes and to modulate the host response, which may bring both benefit and harm, depending on the clinical circumstances. The term systemic inflammatory response syndrome (SIRS) was introduced several years ago to describe the familiar clinical syndrome of sepsis, independent of its cause. SIRS can result from trauma, pancreatitis, drug reactions, autoimmune disease, and a host of other disorders; when it arises in response to infection, sepsis is said to be present. SIRS describes a dynamic process that has adaptive survival value for the host. The maladaptive consequence of this process in the critically ill patient is the development of progressive but potentially reversible remote organ dysfunction-the multiple organ dysfunction syndrome. The development of cogent conceptual frameworks for classification of the septic response in critically ill patients is more than a question of linguistic pedantry. Optimal therapy presupposes identification of an homogeneous patient population with a characteristic disease process and a predictable response to an intervention. Although progress has been made in identifying such groups of critically ill patients, the disappointing results of clinical trials of agents that so clearly demonstrate efficacy in animal models indicates that considerable work remains.     

Impact of rapid advancement of international standardization on technical requirements for new drug registration

Internationalization of new drug research and development is rapidly progressing. When mutual international acceptance of clinical trial data is realized, scientifically superior data will eradicate and replace all not so scientific data. This means that healthy competition would benefit the data of clinical trials. The same is true of anti-tumor drugs. Some Japan originated antitumor drugs were developed in foreign countries prior to domestic clinical development. In future, geographic centralization of clinical trials in areas which can conduct scientifically more consistent trials is expected. There are only a limited number of institutes which can conduct high-quality clinical trials of antitumor drugs, so they want Japan, a potential country, to come to other areas to produce high-quality clinical trial data. The resolution of a number of daily stumbling blocks such as informing the patient that he or she is suffering from cancer is a prerequisite for conducting high-quality clinical trials. But every effort must be made so that it will not be said: "Data produced overseas are better. There is no need for Japan to use its knowledge and effort in the field of clinical development."     

6-bit and 8-bit digital radiography for detecting simulated periodontal lesions

Considerable controversy exists in the orthopedic and neurosurgical literature over the true incidence and nature of spinal deformity after multiple-level cervical laminectomy in children. Eighty-nine patients with a mean radiographic follow up of 5.1 years (range 2-9 years) were reviewed. Mean age at surgery was 5.7 years (range 1 month-18 years). Most common diagnoses were Arnold-Chiari malformation, syringomyelia, or both (81%). Significant deformity developed in 46 patients (53%), with 33 developing a mean kyphosis of 30 degrees (range 5-105 degrees) and 13 developing a mean hyperlordosis of 62 degrees (range 40-95 degrees). Peak age at surgery of 10.5 years correlated weakly (P = 0.08) with the development of kyphosis. The development of hyperlordosis was strongly correlated (P = 0.01) with a peak age at surgery of 4.2 years. There was no correlation between diagnosis, sex, location, or number of levels decompressed and the subsequent development of deformity.     

Automated detection of BB pixel clusters in digital fluoroscopic images

Small ball bearings (BBs) are often used to characterize and correct for geometric distortion of x-ray image intensifiers. For quantitative applications the number of BBs required for accurate distortion correction is prohibitively large for manual detection. A method to automatically determine the BB coordinates is described. The technique consists of image segmentation, pixel coalescing and centroid calculation. The dependence of calculated BB coordinates on segmentation threshold was also evaluated and found to be within the uncertainty of measurement.     

Analytical methodology in quantitative digital subtraction radiography: analyses of the aluminum reference wedge

An aluminum wedge can be used to quantify volumetric change in crestal alveolar bone which has been identified through subtraction radiography. This study compares two methods for using an aluminum wedge for this purpose: 1) the aluminum wedge is present in both radiographs and used to determine the aluminum equivalent bone density present in the region of change for each radiograph; and 2) the aluminum wedge is present in only one radiograph and the difference image of the wedge in the subtraction image is used to calculate the aluminum equivalent change in bone density. Pairs of standardized x-rays were taken with synthetic bone chips of known weights placed when the second x-ray was taken. The volumetric change produced by the bone chips was calculated by the two methods. The relationship of the calculated volumes to the chip weights had a higher r2 value (P < 0.05) for the two-wedge method than for the one-wedge method. The two-wedge method is recommended for volumetric quantification of alveolar bone change. The influence of the clarity of the aluminum wedge image in the x-ray pairs was also examined in this study and found to be significant. Attention must be given to factors which affect the aluminum wedge image characteristics to achieve optimal results.