Advances in contrast enhancement for optical coherence tomography

High resolution in vivo imaging of the lamina cribrosa

The lamina cribrosa (LC) is considered to be the principal site of retinal ganglion cell axon injury in glaucoma. Imaging technology has steadily improved in recent years, allowing greater resolution of fine details of laminar structure. Histological studies have elucidated the details of LC structure, both in normal and glaucomatous eyes, but such studies are limited by smaller sample size, greater difficulty of conducting prospective studies, and possibility of altered tissue architecture during histologic processing. We reviewed the literature describing the LC in primate and human eyes using in vivo imaging devices and provided a brief explanation of the imaging technology and main results of the articles. We also discuss the advantages and limitations of each imaging modality described, including optic disk photography, confocal scanning laser ophthalmoscopy (CSLO) and optical coherence tomography (OCT). These modalities provide en face and/or cross-sectional images of the LC in vivo. Enhanced depth imaging OCT has recently led to important advances in imaging deeper structures of the posterior segment, including the LC. Adaptive optics has been adopted in CSLO and OCT imaging to correct for ocular aberration and has improved resolution and contrast of the LC images. Post-image processing techniques to compensate for light attenuation and enhance contrast in OCT images enabled better visualization of the LC beneath the neuroretinal rim, vascular structures, and scleral rim. Long-wavelength probe OCT has shown good visualization of the LC with improved penetration when combined with swept-source OCT. Contrast agents for enhanced visualization of selective target structures in OCT have been developed. All these technologies hold great promise for improved in vivo imaging of the LC and require further investigation.

Silica-gold nanoshells as potential intraoperative molecular probes for HER2-overexpression in ex vivo breast tissue using near-infrared reflectance confocal microscopy

Obtaining negative margins is critical for breast cancer patients undergoing conservation therapy in order to reduce the reemergence of the original cancer. Currently, breast cancer tumor margins are examined in a pathology lab either while the patient is anesthetized or after the surgical procedure has been terminated. These current methods often result in cancer cells present at the surgical resection margin due to inadequate margin assessment at the point of care. Due to such limitations evident in current diagnoses, tools for increasing the accuracy and speed of tumor margin detection directly in the operating room are still needed. We are exploring the potential of using a nano-biophotonics system to facilitate intraoperative tumor margin assessment ex vivo at the cellular level. By combining bioconjugated silica-based gold nanoshells, which scatter light in the near-infrared, with a portable FDA-approved reflectance confocal microscope, we first validate the use of gold nanoshells as effective reflectance-based imaging probes by evaluating the contrast enhancement of three different HER2-overexpressing cell lines. Additionally, we demonstrate the ability to detect HER2-overexpressing cells in human tissue sections within 5 min of incubation time. This work supports the use of targeted silica-based gold nanoshells as potential real-time molecular probes for HER2-overexpression in human tissue.