X-線間接像を利用した心臟實大測定法について

抄録

1. The author calculated the ratio of enlargement applicable to conversion of the short distance roentgenogram, shch as taken from the fluoroscopic image, into a picture that practically corresponds to an orthodiagram or tele-roentgenogram.
If a cone of rays originating from a point source on the z-axis of the three-dimensional rectangular Cartesian coodinate system cast a shadow of a sphere with the center on the z-axis upon the x-y plane, the distance from the z-axis of any point (x, y) on the optical edge on the sphere is expressed by. √x²+y². Let the “focal” distance onto the fluoroscope be F; the angle between the z-axis and the ray touching the sphere at the point (x, y) be. θ, and the fluoroscopic image corresponding to thelength. √x²+y² cast on the x-y plane (represented by the fluoroscope) will be F tan. θ. Thus the ratio of magnification, M, is
M=F tanθ√x²+y²
The author theoretically showed applicability of this formula.
2. A model of the heart was cut out from diatomaceous earth (Kieselguhr), and the applicability of the above formula was tested with satisfactory result.
The actual site of the optical edge was also determined on a cadaveric normal human heart, and it was confirmed that the calculation with the above formula would not be affected by the displacement of the optical edge due to the change of focal distance.
3. Measures representing twelve principal points on the cardiac silhouette and the transverse diameter of the chest, as obtained by the orthoscopic technique in ventro-dorsal and right lateral positions were compared with those calculated from the data on the fluoroscopic image by means of the above formula. The result confirmed the validity of the author's procedure, even in the case of large hearts of athletes.
4. The author considered various condition, such as the position of the chest, the phase and depth of respiration, the phase of the cardiac cycle, the half shadoW, and the geometric sharpness of the fluorecent screen. The effect of the displacement of the chest to the right or the left on the breadth of the aorta was very distinct.
5. The data obtained by the present method of conversion from the short distance roentgenogram can be compared with those of teleroentgenography with discrepancies not larger than 2%.
6. Various convenient procedures on the above principle were also tried and suggested.