Analysis and evaluation of BC-mode OCT image visualization for microsurgery guidance

Abstract

Optical coherence tomography (OCT) has been gaining acceptance in image-guided microsurgery as a noninvasive imaging technique. However, when using B-mode OCT imaging, it is difficult to continuously keep the surgical tool in the imaging field, and the image of the tissue beneath the tool is corrupted by shadow effects. The alternative using C-mode OCT imaging is either too slow in imaging speed when operating in a high-resolution mode, or provides a poor image resolution in a high-speed mode, with the sweep rate less than one million hertz. Moreover, the 3-dimensional rendering of C-mode OCT image makes it difficult to visualize the tissue structure and track the surgical tool beneath the tissue surface. To solve these problems, we propose a BC-mode OCT image visualization method. This method uses a sparse C-scanning scheme, which provides a set of high-resolution B-mode OCT images at sparsely spaced cross sections. The final BC-mode OCT image is obtained by averaging the image set, with inter frame variance processing to enhance the signal of the surgical tool and tissue layers. The performance of BC-mode OCT images, such as image resolution, signal to noise ratio (SNR), imaging speed, and surgical tool tracking accuracy, is analyzed theoretically and verified experimentally. The feasibility of the proposed method is evaluated by guiding the insertion of a 30-gauge needle into the cornea of an ex-vivo human eye freehand. The results show that this provides better visualization of both the surgical tool and the tissue structure than the conventional B-or Cmode OCT image.

Higher-order regression three-dimensional motion-compensation method for real-time optical coherence tomography volumetric imaging of the cornea

“…Note that due to the refractive power of the cornea and crystalline lens, the OCT image of the retina is distorted and does not represent the true curvature of the retina so that additional image processing is required to obtain the true reference image. However, for many applications (including robotic tool guidance that we are pursuing 2 , 28 – 30 ), an optically distorted image is sufficient and only the relative position and the curvature are needed to correctly assess the tool to tissue distance. Therefore, even for retinal imaging, one could still use the same processing methods to obtain motion-free retinal images.…”

Demonstration of Optical Coherence Tomography Guided Big Bubble Technique for Deep Anterior Lamellar Keratoplasty (DALK)

“…Kang et al used the common-path OCT image to guide the microinjector for subretinal injection [26,27]. B-mode and C-mode OCT imaging have also been used to track various surgical tools underneath the tissue [28][29][30]. Based on these imaging techniques, a group at Duke University used a cooperative device along with real-time B-scan OCT data to assist in DALK needle insertion [31] and Shin et al used an M-mode OCT integrated needle for lamellar keratoplasty [32].…”