# Algorithm for using dual energy computed tomography to determine chemical composition: A feasibility study

## TL;DR

This study presents a new algorithm using dual-energy CT to determine the chemical composition of materials with high accuracy, which could improve radiation therapy planning.

## Contribution

A novel algorithm is developed to determine elemental composition and weight fractions using dual-energy CT data.

## Key findings

- The algorithm accurately identified chemical constituents of unknown materials with differences <0.01% for compounds using mono-energetic X-rays.
- For spectral X-rays, the algorithm showed 2.98% difference for compounds and 6.03% for mixtures.
- The method reduces uncertainty in SPR calculations, improving dose accuracy in radiation therapy.

## Abstract

Using dual-energy computed tomography (CT), this study aims to develop an algorithm to identify the chemical constituents of an unknown material (compound or mixture) and improve the accuracy of material discrimination. The algorithm requires mass attenuation coefficients (MAC) that were obtained using a dual energy CT as an input, identifies the elemental composition, and then calculates its weight fraction. To evaluate the functionality of the developed algorithm, it was used to determine the chemical constituents for human tissues. Furthermore, the results were compared with those provided by the National Institute of Standards and Technology (NIST). We used dual energies 80/140 kVp for spectral CT scans, as inputs to the algorithm, in addition to a set of 50/80 and 80/100 keV for mono-energetic X-rays. The algorithm correctly determined the chemical constituent elements of unknown materials. Results were obtained for the fractional weights of each component for mono-energetic X-rays and spectral X-ray use. For mono-energetic X-rays, the differences were < 0.01% for compounds and 6.02% for mixture, respectively. For the spectral X-rays, the differences in 2.98% for compounds and 6.03% for mixtures, respectively. We developed an algorithm to determine the type and weight fraction of an element using the MAC of dual-energy CT. The algorithm can exclude the inherent uncertainty of SPR calculations and improve the accuracy of dose calculations in radiation therapy planning.