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Heart Size from Routine Chest Films

1946; Radiological Society of North America; Volume: 47; Issue: 4 Linguagem: Inglês

10.1148/47.4.355

1527-1315

Paul C. Hodges,

Cardiac Imaging and Diagnostics

Roentgen ray determination of the size of the human heart may be extremely precise if one employs sufficiently refined technics, such as those for volume, or a mere approximation if the subjects have heart disease and the criterion of size is the transverse diameter of the frontal plane silhouette. Estimation of frontal plane area from orthodiagrams or from specially made films constitutes a practical compromise between these two extremes, and tables and equations have been developed for predicted normal area from height and weight. The general radiologist faces daily the task of passing judgment on the shape and size of the hearts that he sees in routine chest films. In our laboratory such films invariably are stereoscopic and are accompanied by a record of the patient's height, weight, and anteroposterior chest diameter. Exposure times range from 1/30th of a second to 1/10th of a second, depending on the thickness of the chest, and there is no attempt to synchronize exposures with a particular point in the cardiac cycle. In spite of this, we find that there is seldom much difference in the size of the heart shadows in the two films. Occasionally one shadow will be distinctly smaller than the other, but in such cases reraying usually yields two shadows approximately alike and approximately the same as the larger shadow in the first pair. These observations have led us to believe that the systolic size rarely is recorded on routine chest films and that the larger shadow in a pair of such films may be accepted as of approximately diastolic size. When general inspection suggests cardiac enlargement or there is clinical reason to suspect it, we measure gross frontal plane area from the larger of the two shadows in our chest films and then correct this value for divergent distortion. If the net frontal plane area thus obtained is within plus or minus 10 per cent of the normal area predicted by the patient's height and weight, we report it as normal but add in brackets the actual percentage variation from normal. When the variation exceeds 10 per cent, we report the heart as N percent over- or undersize. Technical Details With a wax pencil the right and left borders are sketched in as solid lines and the arbitrarily drawn upper and lower limits as broken lines. These lines are now transferred to white tracing paper and, by means of a planimeter, the area enclosed within the solid and broken lines is measured—in other words, the gross frontal plane area of the heart. In our laboratory the outlining and tracing are done by the radiologist, the measurements by stenographers. Correction for Divergent Distortion Because of the divergent distortion that is always present in ordinary roentgenograms, gross area is greater than true or net frontal plane area, the latter being obtained from the former by multiplying gross area by a correction factor F, obtained from the equation: