Experimental Study of CT-densitometry on Physical Phantoms

Abstract

Objective: to assess the accuracy of CT densitometry as a method for measuring the X-ray density of an object, as well as factors affecting the measurement results.

Material and methods. X-ray density indicators were measured in various zones of phantoms containing drinking water with a volume of 0.5, 1.0, 1.5, and 2.0 l, as well as 5 identical vials with a capacity of 0.25 l with iopromide solutions with a concentration of 0, 5.2, 7.6, 10 and 20 ml/l. For each phantom, from 5 to 10 scans were made, followed by measuring the X-ray density of the contents in the central zone closest to the CT system center of rotation, and two zones located to the periphery from the center of rotation.

Results. As a result of analyzing the values of measuring X-ray density in various parts of water-containing phantoms, an increase in the values of X-ray density near the center of rotation of the system and in the upper sections of the phantom with an increase in the volume of phantom was revealed. In the lower peripheral zone in 1.5 and 2.0 liter phantoms, the X-ray density was unchanged. The overestimation of the X-ray density values of the CT images of phantoms with small and large concentrations of iopromide during co-scanning compared with separate scanning was determined.

Conclusion. CT densitometry is a highly sensitive method for measuring the X-ray density of image elements, however, the X-ray density of neighboring structures and the location of this zone relative to the center of rotation of the CT system affect the CT densitometry results. During jointly scanning phantoms of various densities, their mutual influence and the appearance of specific artifacts in the form of dark stripes on the lines of continuation of horizontal levels and “pulling up” the edges of these horizontal contrast levels to the center of rotation of the system were noted.