Paul R. Herz

Micromotor endoscope catheter for in vivo, ultrahigh-resolution optical coherence tomography

A distally actuated, rotational-scanning micromotor endoscope catheter probe is demonstrated for ultrahigh-resolution in vivo endoscopic optical coherence tomography (OCT) imaging. The probe permits focus adjustment for visualization of tissue morphology at varying depths with improved transverse resolution compared with standard OCT imaging probes. The distal actuation avoids nonuniform scanning motion artifacts that are present with other probe designs and can permit a wider range of imaging speeds. Ultrahigh-resolution endoscopic imaging is demonstrated in a rabbit with <4-microm axial resolution by use of a femtosecond Cr:forsterite laser light source. The micromotor endoscope catheter probe promises to improve OCT imaging performance in future endoscopic imaging applications.

Ultrahigh resolution optical biopsy with endoscopic optical coherence tomography

Optical coherence tomography (OCT) is an emerging medical imaging technology that can generate high resolution, cross-sectional images of tissue in situ and in real time. Although endoscopic OCT has been used successfully to identify certain pathologies in the gastrointestinal tract, the resolution of current endoscopic OCT systems has been limited to 10-15 microm for in vivo studies. In this study, in vivo imaging of the rabbit gastrointestinal tract is demonstrated at a three-fold higher resolution (< 5 microm), using a broadband Cr(4+):Forsterite laser as the optical light source. Images acquired from the esophagus, trachea, and colon reveal high resolution details of tissue architecture. Definitive correlation of architectural features in OCT images and histological sections is shown. The ability of ultrahigh resolution endoscopic OCT to image tissue morphology at an unprecedented resolution in vivo advances the development of OCT as a potential imaging tool for the early detection of neoplastic changes in biological tissue.

Optical coherence tomography contrast enhancement using spectroscopic analysis with spectral autocorrelation

Enhanced tissue contrast in developmental biology specimens is demonstrated in vivo using a new type of spectroscopic optical coherence tomography analysis that is insensitive to spectroscopic noise sources. The technique is based on a statistical analysis of spectral modulation at each image pixel, and provides contrast based on both the intensity of the backscattered light and the distribution of scattering particle sizes. Since the technique does not analyze optical power at absolute wavelengths, it is insensitive to all spectroscopic noise that appears as local Doppler shifts. No exogenous contrast agents or dyes are required, and no additional components are needed to correct for reference arm motion.

High‐resolution imaging of the thyroid gland using optical coherence tomography

Current diagnostic imaging modalities of the thyroid gland cannot reliably distinguish benign from malignant lesions, primarily because of their inability to visualize microscopic structure. A high‐resolution imaging technique capable of examining thyroid tissue architectural morphology in real time is needed. Optical coherence tomography (OCT) has been shown to achieve high resolutions approaching the cellular range (1–15 μm). The feasibility of optical coherence tomography for imaging thyroid tissue was explored ex vivo on the human thyroid gland.

Ultrahigh resolution OCT imaging with a two-dimensional MEMS scanning endoscope

This paper reports preliminary results from the development and application of a two-dimensional MEMS endoscopic scanner for OCT imaging. A 1 mm diameter mirror provides high aperture over large scan angle and can scan at rates of hundreds of Hz in both axes. The mirror is integrated with focusing optics and a fiber-optic collimator into a package of ~5 mm diameter. Using a broadband femtosecond laser light source, ultrahigh axial image resolution of < 5 um in tissue is achieved at 1.06 um center wavelength. Ultrahigh resolution cross-sectional and three-dimensional OCT imaging is demonstrated with the endoscope with ~12 um transverse resolution and < 5 um axial resolution.

Arrays of nanowires on silicon wafers

Nanowires made of thermoelectric-relevant materials were grown in the pores of alumina templates fabricated on silicon wafers. This architecture combines the nanometer-scale, self-assembly nature of the anodic alumina with the micro-scale, versatile nature of integrated circuits processing. The nanowires can be made by the pressure injection technique, and even more conveniently by electrochemical deposition. The geometry is adequate for 2-point transport measurements on the nanowire arrays, and for fabrication of nanowire-based devices made of several materials and several components. In this context, a fabrication scheme for a thermoelectric device, containing both n-type and p-type legs, is suggested.

High-Resolution 3D OCT Imaging with a MEMS Scanning Endoscope

Three-dimensional imaging is achieved by optical coherence tomography (OCT) integrated with a two-axis MEMS scanner to enable noninvasive volume imaging of biological tissues. The longitudinal scan is obtained by optical coherence interferometry. The transverse scan is obtained by tilting the two-axis MEMS mirror to scan the optical beam across the target. High-resolution OCT imaging has enabled in vivo observation of tissue architectural layers and differentiation of normal from tumor lesions within the human gastrointestinal tract. MEMS scanner based catheters with distal beam scanning can image with higher speed, precision, and repeatability than conventional linear scanning catheters. In this work, a 1-mm diameter MEMS scanning mirror with collimator and focusing optics is integrated into a compact 5-mm diameter package that is compatible with limited space in the endoscope. A large fill factor mirror provides high aperture over large scan angle and frequencies of hundreds of Hz in both axes. Using a broadband femtosecond laser light source, high axial image resolution of ~5 um is achieved at 1.06 um wavelength. Transverse resolution of ~ 12-um is demonstrated for cross-sectional image with the endoscope.

Ultrahigh-resolution endoscopic optical coherence tomography for gastrointestinal imaging

Optical coherence tomography (OCT) is an emerging medical imaging technology which can generate high resolution, cross-sectional images of tissue in situ and in real time, without the removal of tissue specimen. Although endoscopic OCT has been used successfully to identify certain pathologies in the gastrointestinal tract, the resolution of current endoscopic OCT systems has been limited to 10-15 um for clinical procedures. In this study, in vivo imaging of the gastrointestinal tract is demonstrated at a three-fold higher axial resolution (<5 um), using a portable, broadband, Cr4+:Forsterite laser as the optical light source. Images acquired from the esophagus and colon on animal model display tissue microstructures and architectural details at ultrahigh resolution, and the features observed in the OCT images are well-matched with histology. The clinical feasibility study is conducted through delivering OCT imaging catheter using the standard endoscope. OCT images of normal esophagus and Barretts esophagus are demonstrated with distinct features.

Ultrahigh-Resolution Optical Coherence Tomography Using Femtosecond Lasers

1 Ultrahigh-Resolution Optical Coherence Tomography Using Femtosecond Lasers J.G. Fujimoto, A.D. Aguirre, Y. Chen, P.R. Herz, P.-L. Hsiung, T.H. Ko, N. Nishizawa, and F.X. Kärtner . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.

Ultrahigh-resolution endoscopic optical coherence tomography

Early detection of gastrointestinal cancer is essential for the patient treatment and medical care. Endoscopically guided biopsy is currently the gold standard for the diagnosis of early esophageal cancer, but can suffer from high false negative rates due to sampling errors. Optical coherence tomography (OCT) is an emerging medical imaging technology which can generate high resolution, cross-sectional images of tissue in situ and in real time, without the removal of tissue specimen. Although endoscopic OCT has been used successfully to identify certain pathologies in the gastrointestinal tract, the resolution of current endoscopic OCT systems has been limited to 10 - 15 m for clinical procedures. In this study, in vivo imaging of the gastrointestinal tract is demonstrated at a three-fold higher resolution (< 5 m), using a portable, broadband, Cr4+:Forsterite laser as the optical light source. Images acquired from the esophagus, gastro-esophageal junction and colon on animal model display tissue microstructures and architectural details at high resolution, and the features observed in the OCT images are well-matched with histology. The clinical feasibility study is conducted through delivering OCT imaging catheter using standard endoscope. OCT images of normal esophagus, Barretts esophagus, and esophageal cancers are demonstrated with distinct features. The ability of high resolution endoscopic OCT to image tissue morphology at an unprecedented resolution in vivo would facilitate the development of OCT as a potential imaging modality for early detection of neoplastic changes.