Abstract: A catheter-based optical imaging system for imaging a patient includes a catheter-based imaging device configured to direct optical radiation towards a vessel wall and to receive reflected radiation therefrom. A displacement mechanism is configured to vary the position of the imaging device relative to the catheter as a function of time during an imaging scan. An input is configured to receive cardiac event timing data, such as ECG data, from the patient. A trigger module is configured to initiate an imaging scan based on the cardiac event timing obtained from the cardiac event timing data. By triggering the optical imaging scans between cardiac events, artefacts in the image data can be reduced or eliminated.