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The initial radiographic features of 188 patients with pulmonary infections due to Mycobacterium tuberculosiswere compared to 184 patients with M kansasiiand 100 patients with M intracellularisinfections. The patients were all from the University of Texas Health Center at Tyler, all had at least two positive sputum cultures and no other potential pathogen, and none had a past medical history of any type of tuberculosis. The comparison showed that all three organisms have a strong tendency to produce cavitary infiltrates in the posterior portions of the upper lobes. No distinctive or pathognomonic feature could be found. The atypical organisms were more likely to produce thin-walled cavities and far advanced unilateral disease, but both of these patterns also occurred with M tuberculosis. Endobronchial spread and volume loss were common in all three diseases. The only definite difference seems to be the absence of a primary or juvenile form of atypical tuberculosis and a much greater incidence of empyema and postprimary pleural effusions with M tuberculosis. In an individual case, the roentgenographic manifestations of the three diseases are indistinguishable.

A partial chest phantom was constructed to compare two commonly employed radiographic techniques, 70 kVp without a grid and 120 kVp with a grid, for the detection of pulmonary nodules. The phantom consisted of human ribs embedded in paraffin, the lungs of a dog injected with silicone rubber, a tissue equivalent wax heart and beeswax nodules. The nodules ranged in size from 3–7 mm. A series of 120 films was exposed, half with each technique, and the films were interpreted by three senior residents and seven staff radiologists. More nodules of all sizes except 3 mm were detected with the 120 kVp technique. The 3 mm nodules were rarely detected with cither technique. The disadvantages of the 120 kVp technique were an approximate 50 percent increase in patient exposures and almost twice as many false-positive nodule detections.