Quantification of breast composition by using a dual-energy technique with a photon-counting detector: Monte Carlo simulation studies

Photon-counting detectors with energy-discrimination capabilities are able to reduce radiation dose and suppress noise compared with conventional detectors for X-ray imaging. These detectors are suitable for spectral X-ray imaging because they can measure the energy of each photon and provide spectral information. One potential application of photon-counting detectors with energy-discrimination capabilities is the quantification of breast composition by using dual-energy techniques. In this study, we implemented quantitative breast imaging with dual-energy techniques by using Monte Carlo simulations. An X-ray imaging system was simulated with a photon-counting detector based on cadmium zinc telluride and a micro-focus X-ray tube. In order to decompose three materials with two spectral measurements, we applied an additional constraint that the sum of the volumes of each material be equivalent to the volume of the mixture. Inverse fitting functions with the least-squares estimation were used to obtain fitting coefficients and calculate volume fractions for each material. The results showed that the degree of decomposition for the composition included in the mixtures varied with the type of composition and the inverse fitting function. High-order fitting functions increased the quantitative accuracy, but the uncertainty of the decomposed images was increased for high-order fitting functions. This study demonstrates that it is possible to quantify breast composition by using dual-energy techniques and photon-counting detectors without an additional exposure and that the decomposed images should be evaluated by considering both their uncertainties and quantitative accuracies.