Accurate z-offset calibration for oct system

An optical coherence tomographic (OCT) imaging system, comprising:

• a catheter having a catheter sheath spanning from a proximal end to a distal end along a catheter axis;
• an imaging core enclosed inside the catheter sheath and configured to guide a light beam from the distal end of the catheter sheath at a nominal angle with respect to the catheter sheath;
• and
• a processor configured to:
• control the imaging core to scan a cylindrical phantom which has a known thickness, wherein the imaging core acquires the OCT image of the cylindrical phantom by transmitting the light beam through the cylindrical phantom, and collecting light reflected and/or backscattered from an inner surface and an outer surface of the cylindrical phantom;
• display the OCT image of the cylindrical phantom on a display device;
• determine a location of the inner surface and a location of the outer surface of the cylindrical phantom within the OCT image;
• and
• set the location of the inner surface and/or the location of the outer surface of the cylindrical phantom within the OCT image to an initial z-offset position to correct for variations in optical path length of the catheter and/or variations in the nominal of the light beam.

A method of using a calibration phantom for z-offset calibration of an optical coherence tomography (OCT) system, the OCT system comprising a reference arm and a sample arm having substantially equal optical paths lengths, the method comprising:

• receiving a catheter enclosed within a sterile package, wherein the catheter includes a catheter handle and a catheter body spanning from a proximal end to a distal end with an imaging core enclosed inside the catheter body, and wherein the proximal end is configured to be connected to the OCT system via the catheter handle and the distal end is configured to guide a light beam at a nominal angle with respect to the catheter body;
• removing at least the catheter handle from the sterile package;
• attaching the catheter handle to the OCT system while the catheter body remains at least partially protected by the sterile packaging;
• positioning the distal end of the catheter body inside a calibration phantom such that the calibration phantom is optically aligned with the light beam;
• scanning the calibration phantom with the light beam;
• forming an OCT image of the calibration phantom by collecting light reflected and/or backscattered from one or more surfaces of the calibration phantom;
• detecting a positon of a first surface and/or a positon of a second surface of the calibration phantom within the OCT image;
• and
• performing z-offset calibration by the setting the position of the first surface and/or the position of the second surface of the calibration phantom in the OCT image to a nominal value,
• wherein the known nominal value is related to one or more of the known thickness of the calibration phantom or a diameter of the catheter body or the nominal angle of the light beam or a maximum imaging range of the OCT system.