Teleoroentgen Kymography

THE development of multiple slit roentgen kymography has provided a simple method for graphically recording the movements of the heart, which has yielded much information of physiological and clinical interest. The movements of the various chambers throughout the cardiac cycle, recorded in the form of a wave, are characteristic. The ventricular waves bear a close resemblance to experimental curves of ventricular volume changes. Zdansky and Ellinger (1), impressed by the close correspondence, regarded the kymographic wave of the left ventricle as practically a pure volume curve, and with restrictions accepted differences in amplitude of the wave as an index of changes in stroke volume. Johnson (2) found a close correspondence between the amplitude of the kymographic ventricular wave and stroke volume determined by the dye method. The change in cardiac contour which the kymogram records is not purely a volume change however, but is a resultant of the predominant contractile thrust, of rotary movement, and of positional changes of the heart as a whole. The greatest objection to any quantitative interpretation of the kymographic waves is that until now kymograms have generally been taken at about a thirty-inch distance. Due to magnification of the image resulting from the shortened focal distance, no valid conclusions concerning heart size and its changes could, therefore, be drawn. Teleoroentgenographic distance has not been attained hitherto because of the high energy factors required of the x-ray tube. In the first of his contributions on roentgen kymography, Hirsch (3) stated, in discussing technic: “The ideal arrangement would appear to be a very narrow slit, a high speed of film movement, and a long focal distance. But the smaller the slit, the faster the movement, the longer the distance, the greater would be the intensity of radiation necessary to make a satisfactory kymogram at a two-meter distance. Thus, with 0.4 mm. slits and 1.2 cm. per second film speed, it is necessary to energize the tube with 300 ma. at 100 kv. over a period of one second for a distance of 200 centimeters. It is apparent, therefore, that at present technical limitations to the production of the ideal kymogram exist.” The kymograph employed by Hirsch fulfilled these conditions more closely than any apparatus constructed up to that time. Table I, taken from Hirsch's articles (3, 4), summarizes the technic used by various investigators. The factors employed in our study are appended. Hirsch's kymograms were taken with 87 kv. and 100 ma. for an exposure of one second, at 100 cm. Teleoroentgenographic distance has been made possible in our studies by the use of a tube of sufficiently high capacity, energized by a three-phase generator, which tends to maintain an almost even potential near peak value: 180 ma.-sec. at from 60 to 85 kv., depending on the thickness of the chest and the obliquity of exposure, were employed for from a one to one and one-half seconds exposure.