An iodine-calcium separation analysis and virtually non-contrasted image generation obtained with single source dual energy MDCT

Dual energy CT enables the differentiation between various materials by analyzing their unique attenuation spectral response. These responses are represented as vectors on an image-based energy map. Practically, this spectral information can be very noisy requiring further analysis. Furthermore, the material response vectors may be affected by beam-hardening and varied between images. A new dual-energy analysis, approach is proposed to improve iodine-calcium separation. The new algorithm estimates the material response vectors of iodine, calcium and soft tissue. Then it estimates a voxel probability to be either iodine or calcium. This algorithm yields a better separation between iodine and calcium compounds. The above analysis can be used to generate virtually noncontrasted images. A complementary algorithm uses the estimated probabilities and the material response vectors to replace the iodine Hounsfield unit enhancement by the original soft tissue texture. This algorithm has the potential to eliminate the need for an initial non-contrast scan in multi-phasic MDCT clinical procedures, leading to reduced radiation exposure and fully registered studies. Phantom and clinical studies were performed using a single source double-decker dual-energy MDCT prototype. The results showed a robust and reproducible iodine-calcium separation, even in cases with low dose and beam hardening effects. The virtual images, evaluated by two experienced radiologists, had similar image quality as compared to conventional noncontrasted images.