Abstract
We developed a micromotor based miniature catheter with an outer diameter of 3.2 mm for ultrahigh speed endoscopic swept source optical coherence tomography (OCT) using a vertical cavity surface-emitting laser (VCSEL) at a 1 MHz axial scan rate. The micromotor can rotate a micro-prism at several hundred frames per second with less than 5 V drive voltage to provide fast and stable scanning, which is not sensitive to the bending of the catheter. The side-viewing probe can be pulled back to acquire a three-dimensional (3D) data set covering a large area on the specimen. The VCSEL provides a high axial scan rate to support dense sampling under high frame rate operation. Using a high speed data acquisition system, in vivo 3D-OCT imaging in the rabbit GI tract and ex vivo imaging of a human colon specimen with 8 μm axial resolution, 8 μm lateral resolution and 1.2 mm depth range in tissue at a frame rate of 400 fps was demonstrated.
Highlights
Optical coherence tomography (OCT) performs micrometer-scale, cross-sectional and threedimensional imaging by measuring the echo time delay of backscattered light [1]
Many scanning mechanisms have been realized in catheter based endoscopic OCT systems, such as proximal rotation of a torque cable and fiber with distal micro-prism [2,4,5,6,7,8,9,10,11], swinging the distal fiber tip by a galvanometric plate [12], swinging the fiber on a cantilever by piezoelectric transducer (PZT) actuators [13,14,15], and beam scanning using microelectromechanical systems (MEMS) [16,17,18,19]
Imaging using proximal rotary actuation can cover a large area with a simple scanner configuration and is used in most endoscopic OCT applications, but the scanning may be hindered by bending the catheter because the rotation is transmitted from the proximal motor through a long torque cable to the distal imaging optics
Summary
Optical coherence tomography (OCT) performs micrometer-scale, cross-sectional and threedimensional imaging by measuring the echo time delay of backscattered light [1]. Imaging using proximal rotary actuation can cover a large area with a simple scanner configuration and is used in most endoscopic OCT applications, but the scanning may be hindered by bending the catheter because the rotation is transmitted from the proximal motor through a long torque cable to the distal imaging optics. Distal scanning methods using PZT or MEMS based actuators, on the other hand, can provide micron-level precision scanning because the mechanical motion can be directly controlled These methods usually have a limited imaging area because the size of the scanner is limited by the catheter size. With advances in micromotor technology, imaging using distal rotary scanning can be achieved, which can provide large scanning area while maintaining high speed, uniform rotation without degrading the image quality. This study demonstrated very high frame rates, the sampling density was limited at higher frame rates due the OCT system imaging speed [24]
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