Evaluation of xenon as a gaseous roentgenographic contrast material. A preliminary report.

Abstract

The roentgenographic properties of the chemically inert gas Xe were studied in a phantom whose proportions were designed to simulate a human chest. The experiment was performed utilizing 30-, 60-, and 100-kvp x rays and varying amounts of added Al filtration, ranging from 0.5 to 2.0 mm. A system of densitometry was used that included the pre-exposure of a portion of all roentgenograms with a step wedge to be used as a frame of reference and to determine film response. Xenon, in path-lengths ranging from 1.04 to 9.80 cm, casts a faint roentgenographic shadow relative to air; and differences of radiopacification can be seen visually as well as detected densitometrically. The difference of radiopacification of Xe relative to air, as determined densitometrically, is accentuated in exposures made at 30 and 80 kvp relative to those made at 100 kvp, but no difference can be detected between exposures made at 30 kvp and those made at 60 kvp. Addition of 0.5 to 2.0 mm Al filtration has no effect on the relative radiopacification of Xe and air at 60 to 100 kvp, but diminishes thus relative radiopacification at 3a kvp. Thus, it may be advantageous to make exposures of the chestmore » at 60 kvp with 2.0 mm of added Al filtration when using Xe as a gaseous contrast medium. A linear relation was found between centimeters of Al and centimeters of Xe, obtained by performing a regression analysis on all of the values obtained at 80 kvp, with 0 to 2.0 mm Al filtration, for a chest phantom with an antero-posterior dimension of 20 cm. A pilot study was undertaken to ascertain the actual magnitude of the roentgenographic shadow caused by Xe in the lungs of a patient with clinically normal pulmonary dynamics. The results of this preliminary clinical study indicated that the radiopacification due to Xe is insufficient to be readily useful with ordinary roentgenographic techniques. (BBB)« less