Correction of rotational distortion for catheter-based en face OCT and OCT angiography

Abstract

We demonstrate a computationally efficient method for correcting the nonuniform rotational distortion (NURD) in catheter-based imaging systems to improve endoscopic en face optical coherence tomography (OCT) and OCT angiography. The method performs nonrigid registration using fiducial markers on the catheter to correct rotational speed variations. Algorithm performance is investigated with an ultrahigh-speed endoscopic OCT system and micromotor catheter. Scan nonuniformity is quantitatively characterized, and artifacts from rotational speed variations are significantly reduced. Furthermore, we present endoscopic en face OCT and OCT angiography images of human gastrointestinal tract in vivo to demonstrate the image quality improvement using the correction algorithm.

Circumferential optical coherence tomography angiography imaging of the swine esophagus using a micromotor balloon catheter

“…The micromotor catheter exhibits significantly improved NURD performance compared with proximal rotary scanning [24,36,37]. Using a fiducial based correction algorithm, residual NURD in the OCT images can be corrected [24].…”

“…3(a) and 3(b)). Our previous method used the metal strut edges in the cross-sectional OCT images as fiducial markers to measure the instantaneous rotational speed of the micromotor [24]. These locations were used to cubic spline resample the OCT data, such that the pixels in the transverse direction were spatially equally spaced.…”

“…Finally, a threshold mask was applied to the averaged cross-sectional OCTA images to remove regions with low OCT signal where the OCTA data is invalid [21,24,32]. In this study, an empirical threshold of ~mean (background noise) + 1.6 x standard deviation (background noise) was used.…”

“…Recently, our group demonstrated ultrahigh speed endoscopic OCT using a MEMS-tunable vertical-cavity surface-emitting laser (VCSEL) light source and a micromotor imaging catheter in the rabbit [20] and human GI tracts in vivo [21]. The VCSEL light source enables ultrahigh speeds with MHz A-scan rates [20,22] while the micromotor enables imaging at a high frame rate with minimal NURD [19,23], which can be further corrected using fiducial based, non-rigid registration algorithms [24].…”

Correction of motion artifacts in endoscopic optical coherence tomography and autofluorescence images based on azimuthal en face image registration

“…Cardiac and respiratory motion artifacts can be reduced to some degree by decreasing the image acquisition time, but even then there remains a need to compensate for NURD artifacts. Catheters using micromotors to directly rotate the optical assembly are expected to have less severe NURD artifacts compared to proximally driven torque cable catheters; 8 however, the miniaturization of these catheters to access the narrowest organ sites is limited by the relatively large size of the motor. Moreover, due to the difficulty in fabricating perfectly balanced micromotors, NURD can still degrade image quality.…”