Experimental verification of particle-range prediction in biological tissue by single- and dual-energy computed tomography

We introduce a hybrid experimental setup to accurately measure x-ray and ion absorption in tissue or other materials. With this setup using a 3D-printed sample container, the stopping-power ratio (SPR) of homogeneous materials can be measured with an uncertainty of below 0.1%. A total of 40 homogeneous porcine and bovine soft-tissue samples were prepared for measurement, comprising five samples each of eight tissue types (three different muscle and fatty tissues, liver, lung). Using a standard stoichiometric calibration for single-energy CT (SECT) as well as a state-of-the-art dual-energy CT (DECT) approach, SPR was predicted for all tissues and then compared to the measured reference. With the SECT approach, the SPR of all tissues, excluding lung due to its large heterogeneity, was underestimated by up to -3% with a mean (absolute) error of -1.5% (1.5%). In contrast, the DECT-based SPR prediction showed no significant bias with a mean error below the measurement uncertainty of 0.1% and a mean absolute error of 0.2%. In this study, the potential of DECT to decrease range uncertainty could thus be confirmed in biological tissue.