Misconceptions regarding the pathogenicity of silicas and silicates.

Several inhaled substances, from occupational or other environmental exposure, produce significant pulmonary disease and abnormalities demonstrated by pulmonary imaging. Areas of controversy and misconception relate principally to the extent and nature of both the clinical disease and the imaging abnormalities specific to each substance. The size and shape of the inhaled particles is an important determinant of the nature and severity of the disease produced, with fibrous shapes usually being the most pathogenetic. Fibrogenicity is another important pathogenetic characteristic of talc and kaolin, as well as asbestos. Talc produces four distinct forms of pulmonary disease, depending not only on the other substances with which it is inhaled, but also whether it is inhaled or injected intravenously. When inhaled alone, talc does not appear to produce significant pulmonary fibrosis or malignancy. Kaolin, mica, fuller's earth, zeolite, and fiberglass all vary in disease production according to their shape and fibrogenicity. Silica, diatomaceous earth, and other forms of silica are all highly fibrogenic and thus produce clinically obvious disease with sufficient inhalation. The largest particles usually produce nodular patterns in the upper pulmonary fields, as is typical of silicosis. The fibrous particles are more likely to manifest themselves as interstitial patterns in the lower pulmonary fields.

Vasculitis in the lung.

Pulmonary vasculitis occurs most commonly in the collagen vascular diseases and in granulomatous pulmonary disease. In the collagen vascular group, vasculitis causes diffuse interstitial inflammation and subsequent fibrosis, resulting in interstitial radiographic patterns, especially in the lower lung fields. Vasculitis accompanied by granulomatosis typically produces focal inflammation and is, therefore, manifested as nodules and masses. The more typical collagen vascular diseases include rheumatoid arthritis, systemic lupus erythematosus, systemic sclerosis, and dermatomyositis. The most common vasculitis granulomatosis is Wegener's, with similar radiographic abnormalities occurring in lymphomatoid granulomatosis. Atypical examples of vasculitis pulmonary disease include ankylosing spondylitis, in which upper-lung field fibrobullous changes are seen. Periarteritis nodosa and Behcet's syndrome include abnormalities of large vessels and thromboembolic phenomena. Bronchocentric granulomatosis and allergic granulomatosis involve airway abnormalities as well as vasculitis and granuloma formation.

Nocardiosis of the lung: chest radiographic findings in 21 cases.

Pulmonary manifestations of nocardial infection were present in 21 patients, with microbiologic proof in all and pathologic proof in 12. An analysis of the findings in these patients, combined with a review of previous reports of nocardiosis, suggests several important conclusions for radiologists. First, nocardiosis may occur in otherwise healthy persons but is most common in compromised patients, especially those being treated with anti-inflammatory agents, particularly corticosteroids, for chronic obstructive pulmonary disease and other systemic diseases. As pathologic manifestations are both suppurative and granulomatous, the chest radiographic manifestations are pleomorphic and not specific. Consolidations and large irregular nodules, often cavitary, are most common; nodules, masses, and interstitial patterns also occur. Pleural effusions are quite common, and lymph nodes may be enlarged. Difficulty and slowness of culture growth, along with the lack of a serologic test for nocardiosis, necessitate its inclusion in the differential diagnosis for both compromised and noncompromised patients in whom an apparent pulmonary infection cannot be rapidly diagnosed.

Talc: understanding its manifestations in the chest.

Four distinct forms of pulmonary disease caused by talc have been defined. The first form, talcosilicosis, is caused by talc mined with high-silica-content mineral. Findings in this form are identical with those of silicosis. Talcoasbestosis closely resembles asbestosis and is produced by crystalline talc, generally inhaled with asbestos fibers. Pathologic and radiographic abnormalities are virtually identical with those of asbestosis, including calcifications and malignant tumor formation. The third form, talcosis, caused by inhalation of pure talc, may include acute or chronic bronchitis as well as interstitial inflammation; radiographically, it appears as interstitial reticulations or small, irregular nodules, typical of small-airway obstruction. The fourth form, due to intravenous administration of talc, is usually associated with abuse of oral medications and production of vascular granulomas manifested by consolidations, large nodules, and masses. Radiographic abnormalities associated with talc can be predicted when there is sufficient history of the nature of exposure, including the region of origin of the talc in cases of inhalation. Radiographic changes, such as diaphragmatic plaques, often attributed to both talc and asbestos have not been documented to be caused by talc alone. The author provides review of 18 well-documented cases.

Allergic diseases in the lungs.

Four basic immune reactions in the lung are fundamental to our understanding of allergic lung diseases. The first, immediate hypersensitivity, principally involves airway obstruction because of hypersecretion and bronchospasm. Resulting roentgenographic changes are those of large and small airway disease. The second reaction, cytotoxic antibody-mediated disease, produces air space filling by hemorrhage. The third form, immune complex-mediated hypersensitivity, causes mixed patchy consolidation and interstitial roentgenographic patterns caused by inflammation stimulated by antigen-antibody complexes. Fourth, cell-mediated immunity usually produces a granulomatous reaction, roentgenographically manifest by nodules, masses, and enlarged lymph nodes. Applying our understanding of these four basic reactions permits understanding the common allergic disease of the lungs: hypersensitivity pneumonitis, asthma, allergic bronchopulmonary fungal disease, chronic eosinophilic pneumonia, hypereosinophilic syndrome, Goodpasture's syndrome and idiopathic pulmonary hemosiderosis (IPH), Wegener's granulomatosis, and allergic granulomatosis (Churg-Strauss disease). The clinical, pathologic, and roentgenographic manifestations of these diseases are explained and related to the basic immune mechanisms.

Mediastinal masses: a system for diagnosis based on computed tomography.

A revised system for mediastinal mass differentiation has been developed and used at the Veterans Administration Medical Center, San Diego, and University Hospital of the University of California, San Diego. Contrast medium infusion or bolus computed tomography of the entire mediastinum is obtained, except when the mass is probably a thyroid mass (123I scan then obtained first) or an esophageal mass (barium swallow evaluation then obtained first). Next computed tomography density is determined, and only subsequently are masses of similar density subdivided by location. Further differentiation is based on computed tomography imaging parameters. A new algorithm for evaluation of mediastinal masses has resulted from use of this system. The system has been shown to increase specificity of differential diagnosis and to result in increased efficiency of evaluation of patients with mediastinal masses.

Improving specificity of computed tomography in diagnosis of malignant mediastinal lymph nodes.

Four parameters of lymph node appearance on computed tomography were studied to improve specificity for malignancy in bronchogenic carcinoma: 1) node location, 2) homogeneity, 3) border definition, and 4) delineation by fat. Of 54 carcinoma patients, nodes were pathologically malignant in 21. Computed tomography showed enlarged nodes (over 1 cm) in 20 of these (true-positive rate, 96%), but also in 13 of the 33 patients with pathologically benign lymph nodes (false-positive rate, 39%). A combination of all four computed tomography parameters reduced the false-positive rate from 39 to 21% and decreased the true-positive rate from 96 to 86%. The criterion of border definition alone reduced the false-positive rate from 39 to 6%, but decreased the true-positive rate from 96 to 61%. The most useful computed tomography parameter was delineation, which reduced the false-positive rate to 15% and decreased the true-positive rate only to 86%. The computed tomography appearance of enlarged lymph nodes may be used to improve selection of patients with enlarged nodes for preoperative biopsy.

Sensitivity of chest radiography, computed tomography, and gallium scanning to metastasis of lung carcinoma.

To determine the efficacy of radiologic techniques in preoperative staging of the mediastinum for lung carcinoma, the authors studied 45 patients with chest films supplemented with oblique views, esophagrams, gallium scans, and computed tomograms (CT). They interpreted the studies and correlated surgical findings using a modified classification of lymph node regions. The mediastinum was positive on chest films in 14 of the 21 cases with pathologically proved mediastinal metastases (33% false-negative). Gallium scans in cases with a positive primary were positive in 12 of 15 cases with mediastinal or hilar metastases (20% false-negative). Computed tomography showed nodes over 1 or 1.5 cm in size in or adjacent to the biopsy-positive node region in 18 of 19 patients (5% false-negative), extranodal mediastinal involvement, and 9 of 10 proven hilar metastases. Computed tomography is a sensitive screening technique in patients who would otherwise require an invasive staging procedure, but is not highly specific (false-positive rate 38%).

Pulmonary cryptococcosis: radiologic-pathologic correlates of its three forms.

To better understand the radiographic appearance of pulmonary cryptococcosis, 23 human cases and three cases in zoo animals were studied in which both radiographic and pathologic material was available for correlation. Radiographs in 44 additional cases were studied in which documentation was microbiologic but not pathologic. Three forms of pulmonary cryptococcal disease are recognized: (1) air-space collections of fungus with minimal or no inflammatory reaction, causing well defined masses both radiographically and pathologically, as documented by five cases in this series; (2)granulomatous infection, demonstrated here by 21 cases, producing segmental consolidation, poorly defined masses, or "infiltrative masses," often accompanied by lymph node enlargement; and (3) airway colonization without parenchymal infiltration resulting in no significant or specific radiographic findings and no specific pathology. The most specific and distinctive radiographic finding in pulmonary cryptococcosis is the "infiltrative mass," which resembles a mass in one view and an infiltrate in the 90 degree different view. A review of cryptococcosis shows the value of pathologic correlation of the form of the disease in understanding the radiographic abnormalities.

New perspectives on interstitial lung disease.

Pulmonologists, pulmonary pathologists, and radiologists disagree about the pathogenesis, manifestations, and prognosis of the diseases included as "interstitial." The author attempts to place the current understanding of the interstitial diseases in a usable perspective centered on the abnormal chest roentgenogram. Special consideration is given to the progression of several types of interstitial pneumonitis to end-stage lung disease.

The effect of vasospasm on perfusion radionuclide imaging in experimental pulmonary embolism.

Experiments were conducted to further evaluate previously observed discrepancies between postembolic perfusion scans and angiograms, and the relationship of these discrepancies to pulmonary vasospasm. Nonresorbable emboli were formed from Ivalon, muscle, or heated autologous clot. Scans and angiograms were compared at 24-hour intervals for two to eight days. During the first two days after embolism, angiographic-scan discrepancies occurred in most dogs, characterized by decreased size of scintigraphically demonstrated perfusion defects at the same times that the angiogram showed stable or even progressive obstruction. This discordant behavior of scan and angiogram is thought to reflect subsidence of postembolic vasospasm. In the 17 experimental dogs, 13 showed evidence of vasospasm, and four did not. In those that developed spasm, direct angiographic evidence of such spasm was present in all but one, manifest as diffuse constriction of small arteries and diminished parenchymal stain in vascular beds that were not directly obstructed mechanically. Although spasm diminished rapidly during the first 6 hours, there was continued and appreciable further resolution for over 48 hours in some dogs. This study reconfirms the frequent existence of vasospasm in three different embolic models, and indicates subsidence of spasm over a much longer time frame than was formerly supposed. Regression of spasm over an interval of several days suggests that perfusion scans should be performed clinically as soon as possible after a suspected embolic episode, prior to subsidence of spasm, in order to exploit the added sensitivity provided by spasm.

Multilocular cystic nephroma: a radiographic-pathologic correlation of 58 patients.

Clinical radiographic, and pathologic findings of multilocular cystic nephroma (MLCN) in 58 patients are presented. The lesion that affects predominantly boys in childhood and women in adulthood is usually solitary but rarely can be multiple, and it commonly occurs as an asymptomatic mass, occasionally with hematuria. Tumors may grow slowly over years or rapidly within months. A mass that is usually identified on plain radiographs occasionally has curvilinear calcification. Excretory urography and retrograde pyelography are helpful when pelvic herniation of the tumor is recognized, or when septae are noted with total body opacification. Angiography showed an avascular mass (six lesions), a hypovascular mass (14 lesions), or a hypervascular mass three lesions). Ultrasonography is helpful when multiple circumscribed sonolucent areas are identified. Similarly, a multilocular mass with septae is usually identified by computed tomography (six of seven cases). Our findings and a review of the literature indicate that this lesion is a neoplasm that can be strongly suspected preoperatively if pelvic herniation or a multilocular pattern is noted on imaging studies.

Postpartum pleural effusion: a common radiologic finding.

We did a retrospective study of 112 patients and prospective study of 30 patients and 30 controls to ascertain the incidence of postpartum pleural effusion. An effusion was shown on chest radiographs in 51 patients (46%) in the retrospective study, and 20 patients (67%) in the prospective study. The incidence of pleural effusion in obstetric patients in the prospective study was significantly greater than that of controls (chi-squared test, 20.4, p less than 0.001). There was no difference between patients with effusion and those without in age, race, parity, antepartum complications, method of delivery, fetal outcome, or postpartum complications. We conclude that pleural effusion occurs frequently in the first 24 hours after delivery and that, in the absence of symptoms or signs of cardiopulmonary disorder, no intervention is necessary.

Role of radiology in aviation accident investigation.

Radiographic screening of fatality victims for skeletal detail, dental and surgical artifacts, personal effects, and foreign bodies is of established value. Radiography as the primary means of positive victim identification, through comparison with antemortem films and records, is an important new role. Data on sources of injury and relationships between victims and the crash environment may be derived from radiographic injury patterns and may be correlated with mechanisms of injury production. The result of such analysis is improved safety design. Such radiography poses unique technical and logistical problems, often involving temporary or remote facilities, which must be solved with consideration for privacy and safety. Advance planning is essential for maximum benefit from radiographic investigation.

Diagnosis of pulmonary embolism: experimental evaluation of the accuracy of scintigraphically guided pulmonary arteriography.

Technically refined angiograms and scintigrams were extremely sensitive in demonstrating experimental canine thromboemboli, both immediately after embolization and during the entire course of embolic lysis. Technical refinements included subselective, scintigraphically guided, magnification arteriography and eight-view perfusion scintigraphy. During thromboembolic lysis, excellent angiographic-scintigraphic correlation persisted. For every postembolic perfusion defect, the embolic basis could be demonstrated angiographically. Thus, apparent disparities between angiographic and scintigraphic evidence of embolism can no longer be attributed to lysis. Studies using nonresorbable Ivalon emboli indicated that localized spasm may play an important role in the perfusion defects that develop within a half hour after embolization, and that this spasm subsides considerably within 24 hours.

Traumatic splenic cyst: radiologic-pathologic correlation from the Armed Forces Institute of Pathology.

Traumatic splenic cyst is one of many diagnostic choices when a mass is found in the left upper quadrant. In the appropriate clinical setting, demonstration of an intrasplenic, unilocular, avascular, homogeneous, fluid-filled mass with a smooth, sharply marginated wall should suggest a splenic cyst. On pathological examination, an epithelial lining implies a developmental origin. More commonly, no such lining is found and old trauma is assumed to be the etiology.

Chest radiography in desquamative interstitial pneumonitis: a review of 37 patients.

Follow-up radiographs were obtained in 37 cases of desquamative interstitial pneumonitis (DIP) in order to assess the degree to which the radiographic appearance could be used to follow the course of the disease and/or predict prognosis. The films were compared to the clinical outcome in 21 patients and the histology of the original biopsy was studied in 16 cases. The radiographic appearance was most commonly nonspecific, consisting of irregular opacities especially at the bases. Only six cases had the "classic" appearance of hazy, ground-glass densities in the medial parts of the lower lung fields. Of the 21 patients, 16 showed clinical improvement, usually after corticosteroid therapy. The radiographic changes accurately reflected the clinical course in 18 of 21 patients, although specific patterns could not be associated with any specific outcome and the films became completely normal in only four of the 16 patients who improved. Histologic characteristics within the confines of those diagnostic of DIP were not useful in predicting outcome. These results confirm the utility of radiography in following the course of DIP, although specific radiographic appearances cannot be used to predict prognosis. The favorable prognosis demonstrated in DIP favors the separation of DIP and UIP (usual interstitial pneumonitis) as independent diseases.