Effects of geometric and screen-film unsharpness in conventional and 350-kVp chest radiography

Clinical comparison of 350- and conventional 120-kVp techniques indicates that small linear structures, such as small pulmonary blood vessels, are shown better at 120 kVp, due in part to two factors affecting image unsharpness: geometric and screen-film unsharpness. The combined effects of geometric (Ug) and screen-film unsharpness were evaluated for both kVp levels. The total-system modulation transfer function (MTFUg X MTFscreen-film) demonstrates differences in unsharpness under two conditions: (a) when the same screen-film system is used with different magnifications (i.e., extreme planes in the chest) and (b) when different screen-film systems are used for magnification of the midplane of the chest.

Mobile 240 kVp phototimed chest radiography

Chest radiographs obtained with mobile equipment for 240 kVp phototimed technique and conventional technique were compared in 161 patients. Features of interest were visualization of air space, interstitium, mediastinum, pleura and vessels, tracheobronchial tree, catheters and tubes. The 240 kVp system demonstrated consistently good visualization of central air passages, hilar contours, and pulmonary detail. It was superior to the conventional portable in eliminating respiratory motion, defining lung infiltrates, and localizing the endotracheal tube relation to the carina. The 240 kVp system had noticeable deficiencies in depicting calcifications, bone detail, and fat planes. These deficiencies were not of clinical significance. Although the equipment was compact, easily maneuverable, and simple to operate, the cassette holder was somewhat heavy--a detrimental but manageable factor. Another shortcoming was poor visualization of homogeneously opacified catheters within the mediastinum, although catheters with a dense radiopaque stripe alleviated this problem.

Rotating disk device for slit radiography of the chest

A pair of rapidly rotating disks was assembled with multiple radial slits for obtaining chest radiographs in 1/60-1/20 sec., using automatic exposure timing, without visible images of individual slits. Substantial reduction of scattered radiation levels is achieved (one half to one fourth), especially in the retrocardiac and central mediastinal areas of the chest film. Full realization of the potential contrast improvement resulting from this degree of scatter reduction is impaired by the limited latitude of x-ray films used for radiography. These problems and potential solutions are discussed.

Positioning device for cardiac series

The author describes a new positioning device for use during radiography of the chest. This device is particularly helpful when doing a cardiac series.

Digital radiograph of the chest using a computed tomography instrument

Digital radiography (DR) was compared with conventional chest radiography in patients with mediastinal adenopathy, sarcoidosis, and metastatic adenocarcinoma. Contrast resolution was improved by the new technique, offering a wider latitude and edge enhancement. While small, low-contrast details were resolved best by conventional radiography, DR was superior for resolution of nodules. With further improvement of spatial and contrast resolution, DR could become the preferred technique of chest radiography.

Thoracic and pulmonary radiographic modification during immersion in apnea: 1--a special apparatus

Thoracic and pulmonary radiographic modification during immersion in apnea, were studied. An Apparatus "Nuclearisub" was used, it consists of two parts: An x-ray generator (100 KV, 40 mA) and a image intensifier tube (brightness gain 1200) with a transistorized telecamera. Through continuous radioscopy during immersion, can be analyzed the variations caused by redistribution of the blood, as well as the changes in pressure.

Intensive care unit radiology. Problems of interpretation

The radiographic examination of the chest plays an important role in the evaluation of patients in the intensive care unit. The maximum diagnostic value of the radiographs can be achieved only if the films are frequently reviewed, preferably in a daily working conference of the radiologist with the clinicians. Without detailed knowledge of the patient's clinical status, the radiologist will be severely limited in the precision with which the radiographs can be used to evaluate the status of a patient in the intensive care unit.

Limitations of portable roentgenography of the chest in patients with acute respiratory failure

The ability of the portable roentgenography of the chest to define the amount of physiologic shunting and the severity of noncardiogenic pulmonary edema was evaluated in 37 observations of 11 patients. Ten of the 11 patients had acute respiratory failure. The roentgenologic assessment of the amount of pulmonary edema and the severity of left ventricular failure was compared with the physiologic shunt fraction, tracer measured lung water and the pulmonary arterial wedge pressure. The roentgenologic scores for edema did not predict the shunt fraction or tracer measured lung water. The roentgenologic score for congestive heart failure correlated with the wedge pressure but not well enough to be clinically useful. Five per cent of the roentgenograms were false-positive and 11 per cent were false-negative. Roentgenologic findings lagged behind physiologic derangements. Thus, the roentgenogram could predict the shunt value of the preceding day. Results indicate that it is hazardous to accept a portable roentgenographic diagnosis of congestive heart failure as a cause of pulmonary edema.

Chest tomography by gamma camera and external gamma source: concise communication

To obtain tomographic images of the chest, we used a large-field gamma camera to detect the 90 degrees scattered radiations (180 keV) from a linear source of Hg-203 (279 keV). The primary beam traveling across the chest is scattered according to the relative density of tissues. Chest sections can be visualized at different depths on frontal and sagittal planes. The resolution of the technic is that of the gamma camera.

Clinical evaluation of the 350-kV chest radiography system

A chest radiography unit employing 350 kV was evaluated and found to be superior to conventional low-kV systems. Visualization of air/soft-tissue boundaries, mediastinal structures, the retrocardiac area, and lung apices was improved. Other benefits of the high-kV system include reproducibility, reliability, rapid installation, and economy of operation.

Use of a double screen-film combination in bedside chest roentgenography

A double-screen/double-film combination in a single cassette overcomes technical difficulties encountered in bedside radiography with mobile equipment.

Depth resolution: a mechanism by which high kilovoltage improves visibility in chest films

Depth resolution, a measure of the thinnest layer of tissue which will cast a detectable radiographic shadow, significantly limits visibility in conventional chest technique. Depth resolution, averaged over the chest area, improves with increasing kilovoltage, and thin, soft tissues can be seen more readily. The visibility of calcifications increases with kilovoltage in some areas of the chest and decreases in others, which is again explained by depth resolution. Densitometric data verify the mechanism involved: the latitude of the radiographic image matches that of the conventional film at high kilovoltages, so that more chest images are recorded at high contrast where visibility is best.