Computed Tomography Simulation
BROWN
All patients underwent CT simulation in a supine position immobilized on the breast bracket (CIVCO, Medical Solutions). Before simulation, preparatory DIBH coaching and training were performed with computer-controlled, visual feedback active breathing control (ABC) system (Elekta), and the threshold of inspiration volume was identified individually at a comfortable level, typically 70% to 90% of the maximum inspiration volume. Two sets of simulation CT scans, an FB CT scan, and an ABC assisted-DIBH CT scan using the identified threshold of inspiration volume from training were acquired using the same isocenter for each patient (The heart displacement on voluntary deep inspiration breath-hold (VDIBH) as compared with free-breathing (FB) simulation. Green contour: heart position on FB; Brown contour: heart position on VDIBH.