A New Outlook on the Ability to Accumulate an Iodine Contrast Agent in Solid Lung Tumors Based on Virtual Monochromatic Images in Dual Energy Computed Tomography (DECT): Analysis in Two Phases of Contrast Enhancement.

Arkadiusz Zegadło,Magdalena Żabicka,Ewa Więsik-Szewczyk,Aleksandra Różyk

doi:10.3390/jcm10091870

Arkadiusz Zegadło, Magdalena Żabicka + Show 2 more

Open Access

https://doi.org/10.3390/jcm10091870

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Abstract

For some time, dual energy computed tomography (DECT) has been an established method used in a vast array of clinical applications, including lung nodule assessment. The aim of this study was to analyze (using monochromatic DECT images) how the X-ray absorption of solitary pulmonary nodules (SPNs) depends on the iodine contrast agent and when X-ray absorption is no longer dependent on the accumulated contrast agent. Sixty-six patients with diagnosed solid lung tumors underwent DECT scans in the late arterial phase (AP) and venous phase (VP) between January 2017 and June 2018. Statistically significant correlations (p ≤ 0.001) of the iodine contrast concentration were found in the energy range of 40–90 keV in the AP phase and in the range of 40–80 keV in the VP phase. The strongest correlation was found between the concentrations of the contrast agent and the scanning energy of 40 keV. At the higher scanning energy, no significant correlations were found. We concluded that it is most useful to evaluate lung lesions in DECT virtual monochromatic images (VMIs) in the energy range of 40–80 keV. We recommend assessing SPNs in only one phase of contrast enhancement to reduce the absorbed radiation dose.

Highlights

The degree of correlation between the concentration of accumulated iodine and the absorption of photon energy in lung tumors was presented in numerical form, determining the R correlation coefficient assuming the statistical significance of the results at the level of p ≤ 0.001
Based on the theoretical basis of inducing a photoelectric effect in matter, we have demonstrated in practice that the intravenous administration of an iodine contrast agent has an impact on the evaluation of focal lesions in dual energy computed tomography (DECT) based on the analysis of iodine concentration, provided that the appropriate level of scanning energy is used
Since the iodine concentration in lung tumors has the same value depending on the amount of contrast in the tumor vessels on the virtual monochromatic images (VMIs) maps, we used the accumulated iodine atoms to assess their influence on the photon energy absorption and to investigate for which scanning energies the images obtained are strictly dependent on injected contrast agent, and for which it is not the case, which helps to optimize the use of DECT in clinical practice

Summary

Introduction

X-rays (discovered in 1895 by W.C. Roentgen) [1] are produced when fast-moving electrons expelled by the cathode in the X-ray tube collide with the anode. Two different radiation types are generated: braking radiation (Bremsstrahlung radiation) depending on the lamp voltage (keV) and characteristic radiation, where the energy of the photon is characteristic of the anode material. An essential feature of both types of radiation is penetration, i.e., the ability to pass through matter. This feature depends on the energy of the emitted photons and the atomic structure of the material. The attenuation of radiation passing through the tissue occurs due to two processes: (1) Compton scattering and (2) the photoelectric effect

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