George et al.14 concluded based on a 24-patient, multisession study that audio-visual biofeedback can significantly reduce residual motion variability for a given duty cycle, thus potentially improving the accuracy of respiratory-gating. From the results of this study it was seen that audio-visual biofeedback reduced motion by 0.5 cm (0.29 to 0.24 cm) for exhale breathing and 1.5 cm (0.46 to 0.36 cm) for inhale breathing.