Logical analysis in roentgen diagnosis.

During the first year of my residency training I had occasion to ask my chief, Dr. Robert Stone, how I could be sure of the accuracy of my roentgen diagnosis. In the course of our discussion he told me about his former chief, Dr. Howard Ruggles, an excellent diagnostician who was able to make a high percentage of correct diagnoses after a brief examination of the films. Sometimes physicians felt that Dr. Ruggles' ready diagnoses were perhaps not too reliable and they might ask: “Dr. Ruggles, what makes you think this shadow is a metastatic lesion?” To which his just as ready reply would be: “Because it looks like it!” All of us to some extent make diagnoses in this way, and often it is difficult to describe the many possible variations of certain lesions, as, for instance, the protean manifestations of pulmonary tuberculosis. But what about the traps set for the unwary radiologist who uses this “looks like it” method too freely? Figure 1 shows the lung manifestations of four different diseases. The roentg...