Intracoronary ultrasound (ICUS) imaging, an invasive catheter-based imaging modality, has been widely used in clinical diagnosis of coronary artery diseases. Motion artifacts due to cyclic cardiac motion and pulsatile blood are the main factors that hinder the visualization of ICUS longitudinal cut and 3D vessel reconstruction from ICUS image sequence. The aim of this work is to propose an off-line gating method based on ICUS image properties to suppress motion artifacts for continuous pullback ICUS image sequences acquired in vivo covering several cardiac cycles without the help of ECG signals. Based on analysis of intensity features of each ICUS frame, a difference matrix is firstly constructed. Then, potential information about cardiac cycle is extracted from the matrix and the correspondence of each ICUS frame in successive cardiac cycles is obtained through finding a globally optimal path with the lowest cumulative difference value in the matrix. Finally, a subsequence of frames each acquired at the end-diastole of each cardiac cycle is selected to obtain the gated sequence. The main advantage of this method is that it is applicable to those ICUS sequences where the subject's heart rate may be irregular during image acquisition. Also, any high-level image analysis performed to ICUS images is not needed. Results are given for clinical image data of patients in order to validate the proposed method. (C) 2010 Elsevier Ltd. All rights reserved.