Amplitude correlated 4-dimensional cone beam CT

We have developed an amplitude correlated (AC) 4-dimensional cone beam CT (4D-CBCT) imaging technique on the Varian cone beam CT system. We use the Varian Real-time Positioning Monitoring (RPM) system to synchronize the recording of the respiratory motion and the 4D-CBCT imaging. The projection data of the same amplitude in respiratory motion are used to reconstruct an image of the corresponding amplitude in RPM. In the absence of hysteresis of respiratory motion, we can utilize the two CBCT projections in the same breathing cycle: one in the inspiration to expiration and one in the expiration to inspiration to improve the signal to noise ratio, reduce the aliasing due to insufficient sampling in the angular direction.