Eugene J. Keefe Memorial Lecture. The Canadian health care system: an overview.

Canada has 21 years of experience with a national health care insurance program. This lecture describes the program, its evolution, financing, and attitudes and perceptions of the consumer, the provider (physicians and hospitals), and the funding agencies (governments). Comparisons, where appropriate, with the system in the United States are incorporated.

Illusory consolidation of the left lower lobe: a pitfall of portable radiography.

The definition of the left hemidiaphragm is frequently lost when patients are evaluated with portable radiographic equipment. Experimental evidence, based on results of radiography and subsequent sagittal sectioning of a frozen, unembalmed human thorax, corroborated the authors' hypothesis that this finding is related to loss of tangential imaging of the apex of the hemidiaphragm due to cephalic angulation of the central beam accompanied by projection of extrapleural fat onto the base of the left lung. In eight of ten patients in whom portable radiography was performed in 10 degrees-15 degrees of lordosis, varying degrees of loss of definition of the left hemidiaphragm were seen, in the absence of disease. This potential pitfall can be avoided by ensuring that the central beam is tangent to the hemidiaphragm. To do otherwise can create the false impression of disease in the left lower lobe, pleural space, or both.

The anterior junction anatomy.

It is useful to consider the anterior junction anatomy in terms of three components: the superior recesses, the line, and the inferior recesses. Each component localizes to a specific area retrosternally: the superior recesses--behind the manubrium; the line--behind the upper two thirds of the sternal body; and the inferior recesses--behind the lower third of the sternal body and below where the cardiac mass abuts the anterior chest wall. Since the anterior chest wall curves backward from bottom to top (Figure 61), the coronal plane of the superior recesses is behind that of the anterior junction line, the coronal plane of the inferior recesses being in front of that of the anterior junction line. Accordingly, then, anteroposterior conventional tomograms will usually demonstrate the inferior recesses on the most anterior levels, the line a centimeter or so behind the inferior recesses, the superior recesses a centimeter or so behind the line. Understanding the anterior junction anatomy in terms of three components has widespread use, as shown above, by many examples obtained from everyday film reading. The presence, absence, and location of disease may be diagnosed. As well, mistaken diagnoses may be avoided. Since the anterior junction lung relates to the anterior pleural space, pleural space processes may alter the anterior junction anatomy. It must be realized that although visualization of the normal anterior junction anatomy components may help to exclude the presence of retrosternal abnormality, they are not infallible. It is possible for a small lesion to be entirely contained within the anterior mediastinum and, thus, not alter the normal anterior junction components. A deep retrosternal space, where normally the anterior junction line is formed, may allow an anterior mediastinal mass to be present and a normal anterior junction line to be seen if the mass does not occupy the entire depth of the space. Furthermore, in patients with markedly hyperexpanded lungs, it is conceivable that the cardiac mass may abut the chest wall at the level of the inferior recesses to a lesser degree than usual, or not at all. Marked lung hyperexpansion may also conceivably cause the superior recesses to extend above the manubrium.

The posterior junction anatomy.

The anatomy of the posterior junction is more than just the well-recognized posterior junction line. It is helpful to consider this anatomy in terms of three components, each corresponding to a specific area. (a) The Line--Contact of the parietal and visceral pleural surfaces of the right and left lungs, usually anterior to thoracic vertebral bodies 3-5; (b) The Superior Recesses--Edges of lung contact with the mediastinum, usually anterior to thoracic vertebral bodies 1 and 2, which edges marginate a "V" shaped area above the posterior junction line; (c) The Inferior Recesses--Edges of lung contact with the mediastinum over the posterior azygos and aortic arches and in the vicinity of the superior intercostal veins, which edges marginate an inverted "V" shaped area.

Intravenous self-administration of metallic mercury.

Embolization of metallic mercury is extremely rare. The literature has consisted primarily of scattered case reports. Two cases of patients with mercury embolization are presented. The differential diagnosis of the chest radiograph is discussed.

The effect of lobar atelectasis on pleural fluid distribution in dogs.

Fluid was introduced into the pleural space in upright anesthetized, ventilated and/or spontaneously breathing dogs, and its distribution was studied radiographically and confirmed on frozen slices. Various lobes were collapsed to determine the resulting effect on fluid distribution and thereby gain an understanding of so-called "atypical" effusions in a clinical setting. It was found that fluid collects in the dependent portion of the thorax and its distribution is affected by deformation of the chest wall and lung. Airway obstruction causes lobar collapse, which creates negative local pressures secondary to distortion of the lung and chest wall. The effusion moves to the area of distortion to diminish these presures. To the extent that these mechanisms operate in man, it appears that pleural effusions remain subpulmonary until atelecasis of the adjacent lung or distortion of the chest wall causes fluid redistribution.

The value of abdominal computed tomography in the pre-treatment assessment of small cell carcinoma of the lung.

Computed tomographic (CT) scans of the abdomen were obtained in 65 patients with biopsy-proved but untreated small cell carcinoma of the lung. Intra-abdominal metastases were found in 24 (37%), the majority being in the liver and adrenals. Abdominal CT before treatment is recommended as a part of the staging process in patients with small cell carcinoma of the lung, since extent of disease is relevant to prognosis.

Pneumomediastinum revisited.

Pneumomediastinum may result from a variety of causes that may be either intrathoracic (eg, narrowed or plugged airway, straining against a closed glottis, blunt chest trauma, alveolar rupture) or extrathoracic (eg, sinus fracture, iatrogenic manipulation in dental extraction, perforation of a hollow viscus [corrected]. The radiographic signs of pneumomediastinum depend on the depiction of normal anatomic structures that are outlined by the air as it leaves the mediastinum. These signs include the thymic sail sign, "ring around the artery" sign, tubular artery sign, double bronchial wall sign, continuous diaphragm sign, and extrapleural sign. In distal esophageal rupture, air may migrate from the mediastinum into the pulmonary ligament. Pneumomediastinum may be difficult to differentiate from medial pneumothorax and pneumopericardium. Occasionally, normal anatomic structures (eg, major fissure, anterior junction line) may simulate air within the mediastinum. Iatrogenic entities that may simulate pneumomediastinum include helium in the balloon of an intraaortic assist device. In addition, pneumomediastinum may be simulated by the Mach band effect, which manifests as a region of lucency adjacent to structures with convex borders. The absence of an opaque line, which is typically seen in pneumomediastinum, can aid in differentiation. Computed tomographic (CT) digital radiography and conventional CT can also be helpful in establishing or confirming the diagnosis.

Lung involvement in angioimmunoblastic lymphadenopathy (ail).

Two patients with angioimmunoblastic lymphadenopathy (AIL) in whom the disease process involved the lungs are reported. One patient died in respiratory failure. Details of the radiologic appearance, abnormalities of lung function and lung histology are presented together with response to steroid therapy in one patient. Life-threatening involvement of the lung parenchyma can be a mode of presentation of the disease and can contribute to the morbidity and mortality of the disorder.

Radiologic features of miliary tuberculosis in children and adults.

We reviewed the radiologic features of 19 children and 26 adults with miliary tuberculosis. Children had a very high prevalence of associated lymph node enlargement compared to the adults (95% vs. 12%). Pulmonary consolidation was more common in children (42% vs. 12%). Pleural effusions were uncommon in both groups. The miliary pulmonary lesions cleared faster in children. Evidence of previous tuberculosis was seen in 31% of the adults but none of the children. Most of these differences in radiologic features between children and adults probably represent differences in pathogenesis for hematogenous spread in the two groups.

Hypersensitive lung disease due to avian antigens.

Five patients, three exposed to budgerigars (parakeets) and two to chickens, had immunological lung reactions. A Type III hypersensitivity response likely accounts for the pulmonary alteration. The inflammatory exudate accumulates within the alveolar walls and adjacent lobular septa. Radiologically, this is manifested as reticular linear densities and/or multiple small nodules, the interstitial pattern. With spillage into the distal air spaces, an acinar pattern emerges. As this disease is reversible in its early stages, increased awareness and proper management may lead to a reduction in the number of patients who are subsequently diagnosed as having "idiopathic pulmonary fibrosis".

North American blastomycosis in Central Canada. A review of 36 cases.

Experience with 36 cases of North American blastomycosis in Central Canada is reported. Symptoms referable to the respiratory tract predominated, but no uniform clinical pattern for the disease process was evident. Cutaneous and genitourinary tract involvement was present in only a small proportion of patients. The majority of the patients resided in rural areas or were associated with some form of outdoor occupation or activity. No characteristic radiologic appearance could be identified in this series. Amphotericin B administered intravenously is the treatment of choice for this condition. North American blastomycosis is more widespread on this continent than has been previously demonstrated.

Bronchopulmonary dysplasia. A radiologic-pathologic correlation.

In 26 deaths from the neonatal unit with a histologic diagnosis of bronchopulmonary dysplasia (BPD), the histologic stage was compared to the radiologic stage according to the criteria described by Northway and Rosan. In 18 patients (69%), the histologic stage corresponded exactly to the radiologic stage. In the remaining eight patients (31%), there was a difference of one stage. If the 14 cases of Stages I and II were taken together there would be a discrepancy of one stage between the histologic and radiologic stages in 50%. However, with Stages III and IV the discrepancy was only 8.3%. There appears to be better correlation as the severity of BPD increases.

Colliding forces in radiology: technologic imperative, resource limitations, and accountability demands.

Advances in radiology over the past 20 years are the product of a technologic imperative that has produced new approaches to the acquisition of medical images and modifications to conventional approaches. The imperative has placed radiology at the leading edge of the computer-technology era of modern medicine and has also produced several big-ticket technologies that have been identified as major contributors to rising health care costs. Consequently, the demands for quantitative data on the impact and cost-effectiveness of the use of these technologies in the clinical arena are increasing. Meeting the growing demand for accountability in radiology requires that the discipline adopt innovative approaches for assessing its technologies and acquire new types of data, including documentation of cost savings accrued by selective use of radiologic technologies and demonstration of the efficiency and cost-effectiveness of triage schemes that lead to more effective decision making. The requirement of quantitative accountability represents a new way of doing business for radiology and a new approach to management for those responsible for business.

The effects of intravenous infusion of saline on lung density, lung volumes, nitrogen washout, computed tomographic scans, and chest radiographs in humans.

In this study we examined the effect of a 15% increase in extracellular fluid volume on lung density, lung volumes, nitrogen washout, chest radiographs and computerized tomographic (CT) scans of the thorax in 5 volunteers. The objective of the study was to determine the sensitivity of these techniques in detecting small changes in lung water. Lung density was measured by a gamma ray Compton scatter technique and with an Ohio nuclear delta 2020 CT scanner. We measured or derived functional residual capacity, residual volume (RV), vital capacity (VC), and total lung capacity by helium dilution. Single-breath nitrogen washout was used to measure closing volume and the slope of phase III nitrogen washout (delta N2). Chest radiographs were taken in the posteroanterior and lateral projections. With the CT scanner we obtained slices 1 cm thick through the bases of the lungs and at 6 and 12 cm up from the bases. All these measurements were made before and 20 to 90 min after the intravenous infusion of 30 ml/kg body weight of warm saline over a period of 20 min. The most striking findings were a 24% increase in delta N2, a 14% increase in RV, and a 4.5% decrease in VC. Chest radiographs and the CT scans showed an increase in the size of the azygos veins. There was no change in Compton scatter density or the CT numbers. These results suggest that (1) tests of small airway function, such as RV and delta N2, are more sensitive than radiographic techniques to small increases in lung water, (2) there is some protection of the lung to increases in extracellular fluid volume.

Chest radiographic image quality: comparison of asymmetric screen-film, digital storage phosphor, and digital selenium drum systems--preliminary study.

Conventional screen-film radiography does not display all regions of the thorax satisfactorily. Three chest radiographic techniques display both the lung and the mediastinum with good contrast. These techniques are asymmetric screen-film (ASF), digital storage phosphor (DSP), and digital selenium drum (DSD) imaging. ASF systems use two asymmetric screen-film combinations to produce a wide-latitude image of the thorax with good contrast in the lungs. In DSP systems, image data are acquired digitally with a wide dynamic range by using the optical output of a photostimulable phosphor plate; in DSD systems, the wide-range digital image data are acquired by using the electronic charge generated on a drum coated with a thin layer of amorphous selenium. The appearance of a DSP or DSD radiograph is then determined by user-selected image processing operations: tone scaling, spatial frequency processing, and dynamic range compensation. Digital chest radiographs processed with strong regional equalization provide both excellent contrast in the lungs and effective display of the mediastinum and chest wall. At visual comparison, the high lung contrast and good mediastinal, retrocardiac, and subdiaphragmatic detail provided by the DSD method distinguish it from the other two methods.