Apparatus and Method of Image Registration

A system for aligning IVUS and OCT images comprising:

• a probe for OCT and IVUS imaging comprising:
• a sheath having a first end and a second end and a wall defining a lumen;
• a marker that is opaque to light and ultrasound and is located between the first end and second end of the sheath;
• and
• an IVUS/OCT probe head positioned within the sheath;
• an analysis and instrumentation unit in communication with the probe;
• and
• a display in communication with the analysis and instrumentation unit;
• wherein the processor is configured to locate the marker in each of an OCT image and an IVUS image and rotates at least one of the OCT image and IVUS image until the marker in each image is in register with the other.

A system for aligning IVUS and OCT images comprising:

• a probe for OCT and IVUS imaging;
• an analysis and instrumentation unit in communication with the probe;
• and
• a display in communication with the analysis and instrumentation unit;
• wherein the processor is configured to locate the same symmetry in each of an OCT image and an IVUS image and rotates at least one of the OCT image and IVUS image until the asymmetry in each image is in register with the other.

A method of bringing an IVUS image and an OCT image into register comprising:

• obtaining an IVUS image of an area of a lumen;
• obtaining an OCT image of the same area of the lumen;
• determining the same asymmetry in each of the IVUS and OCT images;
• and
• overlaying the IVUS and OCT images and rotating them with respect to one another until the asymmetry in each of the IVUS and OCT images are in register,
• determining the angle of rotation that resulted in the registration.

A method of bringing an IVUS image and an OCT image into register comprising:

• obtaining an IVUS image of an area of a lumen having a marker;
• obtaining an OCT image of the same area of the lumen having the marker;
• determining the orientation of the marker in each of the IVUS and OCT images;
• overlaying the IVUS and OCT images and rotating them with respect to one another until the marker in each of the IVUS and OCT images is in register with the other;
• and
• determining the angle of rotation that resulted in the registration.

A method of checking the calibration of an OCT system comprising a probe having a probe head and a known reflector, and having an IVUS system comprising an ultrasonic transducer on the probe head, the method comprising the steps of:

• calibrating the IVUS system by measuring the amount of time it takes for the ultrasonic pulse to leave and return to the IVUS transducer;
• calibrating the OCT system by measuring the distance to the known reflector;
• acquiring an IVUS image and an OCT image of a vessel comprising a wall defining a lumen;
• processing each image to measure the distance from the probe location in the lumen to the wall of the vessel;
• and
• comparing the OCT distance measurement with the IVUS distance measurement to determine if the two measurements are equivalent to within a predetermined value.

A method for determining the identity of the fluid being used as a flushing fluid in a vessel having a wall having a landmark, the wall defining a lumen, the method comprising the steps of:

• measuring the distance to a landmark on the wall of the vessel from a probe head using OCT;
• measuring the round-trip time it takes for the IVUS ultrasonic pulse to reach the same landmark and return;
• dividing the OCT measured distance by half the IVUS measured round-trip time to obtain a measured speed of sound in the fluid;
• and
• comparing the measured speed of sound in the fluid to the speed of sound in various flushing solutions.

A method of characterizing a tissue comprising the steps of:

• measuring, using OCT, the distance to an edge of the tissue;
• measuring using OCT, the distance to another landmark within the tissue;
• subtracting the distance to the edge of the tissue from the distance to the landmark in the tissue to determine a thickness of the tissue between the tissue edge and the landmark;
• measuring the time it takes for an IVUS acoustic pulse to reach the same edge of the tissue;
• measuring the time it takes for the IVUS acoustic pulse to reach the landmark;
• subtracting the time it takes the IVUS acoustic pulse to reach the edge of the tissue from the time it takes the IVUS acoustic pulse to reach landmark, to calculate the transit time through the tissue to the landmark;
• dividing the thickness of the tissue measured by OCT by the transit time, measured by IVUS, to determine the measured speed of sound in the tissue;
• and
• comparing the measured speed of sound to the speed of sound in various tissue types to determine the tissue characteristic.