Retrieval of cardiac phase from IVUS sequences

Abstract

Most of the quantitative measures from Intravascular Ultrasound (IVUS) images vary with the cardiac cycle. Although ECG-gated acquisition can prevent the pulsations from influencing the measurements, it may extend the acquisition time, and furthermore, very few IVUS systems currently in clinical use incorporate ECG-gated function. In this paper, we present a practical method to retrieve cardiac phase information directly from in vivo clinical IVUS image sequences. In an IVUS image that contains a cross-section of coronary artery, there are three regions annularly distributed from the center of the image - catheter, lumen, and part of the vessel wall. The catheter region exhibits virtually no change from frame to frame during the catheter pullback. While the lumen is a dark region, the vessel wall region appears bright. The change in lumen size and position that accompanies the pulse causes the image intensity of the IVUS images to exhibit a periodic variation along the pullback path. By extracting this signal attributed to the cardiac cycle, a subsequence of frames during pullback at the same phase of the cardiac cycle can be selected. The method was tested by the IVUS images of both a coronary phantom and a patient.