Manual and Fully Automated Segmentation to Determine the Ferromagnetic Status of Bullets Using Computed Tomography Dual-Energy Index: A Phantom Study

Objective The aim was to determine if dual-energy computed tomography (DECT) can discriminate ferromagnetic bullets from nonferromagnetic ones. Methods The ferromagnetic properties of 29 bullets were determined. All bullets underwent a DECT evaluation, and a manual measurement of the dual-energy index was performed by 2 radiologists, followed by a fully automatic measurement, in 3 different positions in a phantom (air, water, and bone). Results Twenty-one bullets were found to be nonferromagnetic. There were significant differences between the mean of the dual-energy index measured in the core of ferromagnetic projectiles and those of nonferromagnetic ones in the lung position of the phantom (P = 0.007). Specificity was 86.36%, and negative predictive value was 90.48%. Among the 29 bullets, 24 were correctly classified. Conclusions Our study demonstrates that DECT can assess the ferromagnetic status of bullets and their magnetic resonance imaging compatibility using an extended computed tomography scale in an ex vivo phantom model.