The authors investigated the possibility of the quantitative evaluation of the regional pulmonary circulation from the chest X-ray film. Theoretically, the density of the chest X-ray film depends upon the pulmonary air content and blood volume in the lung. So, if pulmonary air content was fixed, the X-ray penetration through the chest, i. e. the density of the chest X-ray film should be decided by the pulmonary blood volume. The momentary changes of the pulmonary blood volume were devised to pick up with a mini-computer and to plot on a diagram in four different colors.
Two roentgenograms were taken in a standing position at the terminal moments of systolic and diastolic phase of the heart in the terminal phase of resting inspiration, by means of the breathing-heart beat X-ray synchronizer. Each of the films was developed under the same condition. The synchronizer was controlled by both signals from the thermister mounted in the nose and the photoelectric plethysmograph mounted on a finger tip.
The subtractive density of the two chest X-ray films was measured at each level of all lung fields with a film scanning method—subtractive densitometry, using a small digital computer with a dual channel scanner. Then the signals of this subtractive density were calibrated to the changes of the chest thickness, and displayed by the graphic plotter on a diagram with four different colors according to the difference of the density (red, violet, green and yellow green from maximum to minimum).
In the same patients, macroaggregated albumin labelled with
131I was injected from the antecubital vein in a sitting position, and the radioactivity in the lung was scanned on a scintilation plot diagram in a supine position. The obtained scintigram was compared with the former data.
For the convenience of comparison, plotted diagrams of the lung fields obtained by both methods were divided into four dimensions: upper and lower fields of bilateral lung. When, in all four quadrants, the results agreed with each other, it was evaluated as good correlation; in three quadrants, as fair; in two or less quadrants, as poor.
Consequently, in 3 out of 4 normal subjects had a good correlation. The other was shown as poor. In the patients of respiratory diseases, 3 out of 10 showed good correlation, 4 fair, and 3 poor.
It was suggested that the present method of semiquantitative evaluation of the regional pulmonary circulation would be usefull for the physiological and clinical study of the lung.
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