We present a polarization-sensitive optical coherence-domain reflectometer capable of characterizing the phase retardation between orthogonal linear polarization modes at each reflection point in a birefringent sample. The device is insensitive to the rotation of the sample in the plane perpendicular to ranging. Phase measurement accuracy is ±0.86°, but the reflectometer can distinguish local variations in birefringence as small as 0.05° with a distance resolution of 10.8 μm and a dynamic range of 90 dB. Birefringence-sensitive ranging in a wave plate, an electro-optic modulator, and a calf coronary artery is demonstrated.

Polarization-sensitive low-coherence reflectometer for birefringence characterization and ranging

Since its introduction, optical coherence tomography OCT technology has advanced from the laboratory bench to the clinic and back again. Arising from the fields of low coherence inter- ferometry and optical time- and frequency-domain reflectometry, OCT was initially demonstrated for retinal imaging and followed a unique path to commercialization for clinical use. Concurrently, sig- nificant technological advances were brought about from within the research community, including improved laser sources, beam delivery instruments, and detection schemes. While many of these technolo- gies improved retinal imaging, they also allowed for the application of OCT to many new clinical areas. As a result, OCT has been clinically demonstrated in a diverse set of medical and surgical specialties, in- cluding gastroenterology, dermatology, cardiology, and oncology, among others. The lessons learned in the clinic are currently spurring a new set of advances in the laboratory that will again expand the clinical use of OCT by adding molecular sensitivity, improving image quality, and increasing acquisition speeds. This continuous cycle of laboratory development and clinical application has allowed the OCT technology to grow at a rapid rate and represents a unique model for the translation of biomedical optics to the patient bedside. This work presents a brief history of OCT development, reviews current clinical applications, discusses some clinical translation challenges, and re- views laboratory developments poised for future clinical application.

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Optical coherence tomography: a review of clinical development from bench to bedside

Objectives We present the first clinical experience with intracoronary optical frequency domain imaging (OFDI) in human patients Background Intracoronary optical coherence tomography (OCT) is a catheter-based optical imaging modality that is capable of providing microscopic (∼7-μm axial resolution, ∼30-μm transverse resolution), cross-sectional images of the coronary wall Although the use of OCT has shown substantial promise for imaging coronary microstructure, blood attenuates the OCT signal, necessitating prolonged, proximal occlusion to screen long arterial segments OFDI is a second-generation form of OCT that is capable of acquiring images at much higher frame rates The increased speed of OFDI enables rapid, 3-dimensional imaging of long coronary segments after a brief, nonocclusive saline purge Methods Volumetric OFDI images were obtained in 3 patients after intracoronary stent deployment Imaging was performed in the left anterior descending and right coronary arteries with the use of a nonocclusive saline purge rates ranging from 3 to 4 ml/s and for purge durations of 3 to 4 s After imaging, the OFDI datasets were segmented using previously documented criteria and volume rendered Results Good visualization of the artery wall was obtained in all cases, with clear viewing lengths ranging from 30 to 70 cm at pullback rates ranging from 5 to 20 mm/s A diverse range of microscopic features were identified in 2 and 3 dimensions, including thin-capped fibroatheromas, calcium, macrophages, cholesterol crystals, bare stent struts, and stents with neointimal hyperplasia There were no complications of the OFDI procedure Conclusions Our results demonstrate that OFDI is a viable method for imaging the microstructure of long coronary segments in patients Given its ability to provide microscopic information in a practical manner, this technology may be useful for studying human coronary pathophysiology in vivo and as a clinical tool for guiding the management of coronary artery disease

Three-dimensional coronary artery microscopy by intracoronary optical frequency domain imaging.

Optical coherence tomography (OCT) is now a well-established modality for high-resolution cross-sectional and three-dimensional imaging of transparent and translucent samples and tissues. Conventional, intensity based OCT, however, does not provide a tissue-specific contrast, causing an ambiguity with image interpretation in several cases. Polarization sensitive (PS) OCT draws advantage from the fact that several materials and tissues can change the light's polarization state, adding an additional contrast channel and providing quantitative information. In this paper, we review basic and advanced methods of PS-OCT and demonstrate its use in selected biomedical applications.

Polarization sensitive optical coherence tomography – a review [Invited]

This paper presents a review of the development of optical coherence tomography (OCT), its principles and important applications. Basic OCT systems are described and the physical foundations of OCT signal properties and signal recording systems are reviewed. Recent examples of OCT applications in ophthalmology, cardiology, gastroenterology and dermatology outline the relevance of this advanced imaging modality in the medical field.

Optical coherence tomography - development, principles, applications.

Polarization-sensitive optical coherence tomography (PS-OCT) combines the advantages of OCT with image contrast enhancement, which is based on its ability to detect phase retardation and the fast-axis angle. Both PS-OCT images and histopathology have demonstrated similar features that allowed differentiation of atherosclerotic structures (i.e., plaques) from normal tissue. Moreover, the picrosirius polarization method was used to confirm PS-OCT assessment of collagen in the fibrous cap of atherosclerotic plaques, and high-frequency (40 MHz) ultrasound images were used to identify calcium in the vessel wall. Our preliminary ex vivo investigation of human aortic specimens indicated that PS-OCT might help to identify atherosclerotic lesions.

Polarization-sensitive optical coherence tomography for imaging human atherosclerosis

Atherosclerosis is unquestionably the leading cause of morbidity and mortality in developed countries. In the mean time, the worldwide importance of acute vascular syndromes is increasing. Because collagen fiber is a critical component of atherosclerotic lesions; it constitutes up to 60% of the total atherosclerotic plaque protein. The uncontrolled collagen accumulation leads to arterial stenosis, whereas excessive collagen breakdown weakens plaques thereby making them prone to rupture finally. Thus, in this study, we present the first application, to our knowledge, of using polarization-sensitive optical coherence tomography (PS-OCT) in human atherosclerosis. We demonstrate this technique for imaging of intensity, birefringence, and fast-axis orientation simultaneously in atherosclerotic plaques. This in vitro study suggests that the birefringence change in plaque is due to the prominent deposition of collagen according to the correlation of PS-OCT images with histological counterpart. Moreover, we can acquire quantitative criteria based on the change of polarization of incident beam to estimate whether the collagen synthesized is "too much" or "not enough". Thus by combining of high resolution intensity imaging and birefringence detection makes PS-OCT could be a potentially powerful tool for early assessment of atherosclerosis appearance and the prediction of plaque rupture in clinic.

Correlation of collagen synthesis with polarization-sensitive optical coherence tomography imaging of in vitro human atherosclerosis

A novel differential-phase optical coherence reflectometer (DP-OCR) was proposed using a low-coherence source, integrating it with an analog differential-phase decoding method. In the experiment, the DP-OCR performed a localized surface profile measurement of an optical grating (1200 lp/mm) and demonstrated its ability to measure the translation speed of a tilted mirror. Experimentally, the resolution of the axial displacement of proposed DP-OCR at 185 pm was demonstrated.

Analog differential-phase detection in optical coherence reflectometer

A novel polarization-sensitive optical coherence tomography (PS-OCT) using only linearly polarized light is proposed. To compare with conventional PS-OCT which use circular polarized incident light, linear PS-OCT shows three advantages: (1) in a turbid medium with linear birefringence, the degree of polarization of backscattered light for linearly incident light dose not change significantly; (2) phase retardation (PR) of the sample can be obtained totally from the phase-difference between the polarization heterodyne signals, thus common phase noise rejection mode is introduced inherently. These advantages lead to the immunity of background phase noise and laser frequency noise simultaneously, and also lead to the better sensitivity of PR measurements; (3) the dynamic range of PR in this system is between 0deg to 180deg, which is two times larger than that of conventional circular PS-OCT

Huan Jang Huang

Papers

Polarization-sensitive optical coherence tomography for imaging human atherosclerosis

Correlation of collagen synthesis with polarization-sensitive optical coherence tomography imaging of in vitro human atherosclerosis

Analog differential-phase detection in optical coherence reflectometer

Correlation of collagen synthesis with polarization-sensitive optical coherence tomography imaging of in vitro human atherosclerosis

Development of Linearly Polarized Optical Coherence Tomography and the measurement on Porcine Tendon Birefringence