Room: Exhibit Hall | Forum 9
Purpose: We present a new concept of multi-energy cone-beam CT using spectral modulator and flying focal spot technology, where scatter correction is embedded in a physics-based material decomposition.
Methods: A spectral modulator that is made of attenuating blockers and placed in front of X-ray source can partially filter the spectrum of the X-ray in an alternating way across the detector field of view. By moving the source point using the flying focal spot technology, one can collect projection data at multiple energy levels without down-sampling of projection data. Given the fact that cone-beam CT detector pixel size is small, high-resolution multiple-energy cone-beam CT can be archived using an imaging geometry that maximizes the use of spectral modulator. Taking advantage of the similarity for scatter among a pair of multi-energy rays and an assumption that scatter is dominated by low-frequency components, we put scatter as another unknown term (but with constrains) into a new material decomposition model, leading to scatter being simultaneously removed after material decomposition.
Results: An imaging configuration is included in Fig.1 to illustrate the new concept, where a pair of low- and high- energy projection rays is generated from two focal spots as the high-energy one is filtered by the attenuating block. A scatter included two-material decomposition model is established, from which one can correct for scatter when doing material decomposition. In a simulation study, we generated triple-energy projection rays of a head phantom with scatter insertion, emulating both X- and Z- flying focal spot. Using the constrains on scatter distribution, one can solve the two-material decomposition problem, leading to scatter and beam hardening free CT images, showing its potential in practical applications.
Conclusion: Spectral modulator and flying focal spot enables a full-scale multi-energy cone-beam CT and simultaneous scatter correction. Further in-depth proof-of-concept study are underway.