Christine Jesser

Assessment of coronary plaque with optical coherence tomography and high-frequency ultrasound

This study compares the ability of intravascular optical coherence tomography (OCT) and high-frequency intravascular ultrasound (IVUS) to image highly stenotic human coronary arteries in vitro. Current imaging modalities have insufficient resolution to perform risk stratification based on coronary plaque morphology. OCT is a new technology capable of imaging at a resolution of 5 to 20 microm, which has demonstrated the potential for coronary arterial imaging in prior experiments. Human postmortem coronary arteries with severely stenotic segments were imaged with catheter-based OCT and IVUS. The OCT system had an axial resolution of 20 microm and a transverse resolution of 30 microm. OCT was able to penetrate and image near-occlusive coronary plaques. Compared with IVUS, these OCT images demonstrated superior delineation of vessel layers and lack of ring-down artifact, leading to clearer visualization of the vessel plaque and intima. Histology confirmed the accuracy and high contrast of vessel layer boundaries seen on OCT images. Thus, catheter-based OCT systems are able to image near-occlusive coronary plaques with higher resolution than that of IVUS.

Feasibility of optical coherence tomography for high-resolution imaging of human gastrointestinal tract malignancies

Abstract: Optical coherence tomography (OCT) is a new imaging technology which can perform high-resolution, cross-sectional imaging of the internal microstructure of biological tissues. OCT is analogous to ultrasound, except that it measures the intensity of back-reflected infrared light rather than sound waves. OCT performs two- and three-dimensional imaging of tissue microstructure in situ and in real time. It can achieve image resolutions approaching the cellular level over approximately the same imaging depths as a conventional biopsy. In this article we examine the feasibility of OCT for high-resolution imaging of gastrointestinal malignancies with ex-vivo imaging of normal and pathologic microstructures. Tissue, both normal and neoplastic, was obtained from patients undergoing surgical resection after an initial diagnosis of a gastrointestinal malignancy. The tissue samples were imaged prior to fixation using a laboratory OCT system. The OCT system consists of a fiber optic-based Michelson interferometer, a commercially available amplified superluminscent light source, and a computer for data acquisition. The images were subsequently compared with histological cross-sections corresponding to the imaged areas. The stratified squamous epithelium of the normal esophagus was clearly visible in the OCT images and contrasted to the disorganized and non-uniform nature of the mucosal layers of Barretts esophagus and squamous carcinoma. The columnar epithelial morphology as well as other mucosal structures in normal colon were distinctly visible using OCT. In contrast, disorganization of the normal mucosal layers and ulcerative lesions were identified in tissues from ulcerative colitis and adenocarcinoma of the colon. The ability of OCT to image tissue microstructure at high resolutions makes it a potentially powerful technology for minimally invasive assessment of the gastrointestinal tract and the evaluation of early neoplastic changes.

Index Matching to Improve Optical Coherence Tomography Imaging Through Blood

BackgroundMost myocardial infarctions are caused by the rupture of small rather than large plaques in the arteries of the heart that are beyond the detection limit of current technologies. Methods and ResultsRecently, optical coherence tomography (OCT) has demonstrated considerable potential as a method for high-resolution assessment of vulnerable plaque. However, intravascular OCT imaging is complicated by the need to remove blood from the imaging field because blood results in substantial signal attenuation. This work examines index matching as a method for increasing penetration. Index matching is based on the hypothesis that the predominant source of scattering in blood is the difference in refractive index between the cytoplasm of erythrocytes and serum. By increasing the refractive index of serum to a value near that of the cytoplasm, or index matching, scattering can be substantially reduced. The concept was tested with a system that pumped blood in vitro through transparent tubing. The test compounds, dextran and intravenous contrast agent, both led to significant improvements in penetration (69±12% and 45±4%). No significant effect was seen with the saline control. For dextran, the effect could not be attributed to reductions of red cell number or volume because changes in these parameters were not different from the control. In the case of intravenous contrast, a small but significant relative reduction in red cell volume was seen. ConclusionsThis study demonstrates the feasibility of index matching for improving OCT imaging through blood. Future studies are required to identify compounds for effective index matching in vivo.

High resolution imaging of endometriosis and ovarian carcinoma with optical coherence tomography: feasibility for laparoscopic-based imaging

High resolution imaging of gynaecological tissue offers the potential for identifying pathological changes at early stages when interventions are more effective. Optical coherence tomography (OCT) is a high resolution high speed optical imaging technology which is analogous to ultrasound B–mode imaging except reflections of light are detected rather than sound. The OCT technology is capable of being integrated with laparoscopy for real–time subsurface imaging. In this report, the feasibility of OCT for differentiating normal and pathologic laparoscopically–accessible gynaecologic tissue is demonstrated. Differentiation is based on architectural changes of in vitro tissue morphology. OCT has the potential to improve conventional laparoscopy by enabling subsurface imaging near the level of histopathology.

OCT imaging of osteoarthritic cartilage: structure, polarization sensitivity, and clinical feasibility

This work demonstrates the feasibility of OCT for identifying early osteoarthritic pathology. In addition to structural abnormalities, changes in collagen fiber organization, an indicator of very early osteoarthritis, were assessed with a polarization sensitive OCT system. A portable, real time, modular OCT system, suitable for both laboratory and clinical settings, has been developed. Preliminary in vivo imaging results obtained during partial knee replacement surgery are discussed.

Correlation of polarization-sensitive optical coherence tomography with early osteoarthritis and collagen disorganization

Summary form only given. Osteoarthritis (OA) is a major cause of disability and morbidity. However, conventional imaging methods lack the resolution or are impractical for assessing early OA. Recently, optical coherence tomography (OCT) has demonstrated a feasibility for assessing articular cartilage. In vitro studies have demonstrated that OCT can determine cartilage width at a resolution of 20 /spl mu/m in addition to the identification of fibrillations, fibrosis, and breakdown of the subcondral plate. It was also noted that the normal cartilage was polarization sensitive. In the study, two theories are tested. The first hypothesis is that the origin of polarization sensitivity in normal cartilage is organized collagen. The second hypothesis is that the loss of polarization sensitivity, and therefore collagen disorganization, is a sign of osteoarthritis that precedes cartilage thinning.

Increasing OCT penetration through blood with index matching

Blood substantially reduces image quality during intravascular OCT imaging. In this preliminary work, increasing the refractive index of the serum to that near the cytoplasm, or index matching, was used to increase penetration through blood. The hypothesis was tested by adding compounds to blood in an in vitro system. Increased penetration was noted for dextran and IV contrast which could not be explained by changes in hematocrit or hemoglobin. This study demonstrates the feasibility of index matching for dealing with the blood problem associated with intravascular OCT imaging.

High-resolution imaging of neoplastic lesions using optical coherence tomography

A technology capable of imaging tissue, at or near the cellular level, could lead to the detection of neoplasias at earlier stages than currently possible. This could significantly improve patient outcomes, since once cancer becomes metastatic, cure is difficult. Optical coherence tomography (OCT), a recently developed imaging technology, has ben shown to achieve resolution in the cellular and subcellular range, and it could improve the diagnostic range of clinical imaging procedures. To assess the clinical applicability of OCT, neoplastic specimens from the urinary, gastrointestinal and female reproductive tract were imaged. Sharp differentiation of structures included the mucosa/submucosal/muscularis boundaries, epithelium, glands, supportive tissue, and intramural cysts. The ability of optical coherence tomography to image tissue microstructure at or near the cellular level make it a potentially powerful technology for minimally invasive assessment of tissue microstructure. The resolution of optical coherence tomography, which is greater than any current clinical imaging modality, make it particularly attractive for the assessment of early neoplastic changes.

In vivo imaging of osteoarthritic changes with optical coherence tomography

Optical coherence tomography (OCT) is a powerful medical imaging technology because it permits the high resolution imaging of cross sectional microstructure in situ and in real time [1].