PubMed Health⌕ Search

Biomedical subjects

M E Brezinski

Publications and source records attributed to M E Brezinski.

At least 19 recordsLinked to original sources
PubMed2006

Quantitative optical coherence tomographic elastography: method for assessing arterial mechanical properties.

Optical coherence tomography elastography represents a potentially attractive new technique for measuring elastic properties of tissues on a micron scale. In this study, the feasibility of optical coherence tomography (OCT) to study the mechanical properties of phantoms and atherosclerotic arterial samples is reported. The elastic modulus of tissue-mimicking phantoms was measured using OCT and correlated with mechanical measurements. The results indicate that elastography based on OCT represents an attractive technique for evaluating the mechanical properties of tissues.

Aorta↗
PubMed2004

Optical coherence tomographic elastography technique for measuring deformation and strain of atherosclerotic tissues.

OBJECTIVES: To evaluate optical coherence tomographic elastography as a method for assessing the elastic properties of atherosclerotic plaque and the parameters that influence interpretation. METHODS: Phantoms and aorta were examined in vitro to quantify speckle modulation and measure the displacement and strain maps. A correlation method was used as a speckle tracking technique for measuring axial and lateral displacement vectors and calculation of strain maps. The influence of correlation kernel size on accuracy of the method was evaluated. RESULTS: In terms of a percentage error between calculated and measured displacements, the best results for phantoms were obtained with a 41 x 41 kernel (1.88% error). For both phantom and aorta images, it was found that, with the increasing size of cross correlation kernel, the axial and lateral displacement maps are less noisy and the displacement vectors are more clearly defined. However, the large kernels tend to average out the differences in displacements of small particles in phantoms and decrease the ability of speckle tracking to make microstructural assessments. Therefore, it is important to select kernel size carefully, based on the image features. CONCLUSIONS: Optical tomographic elastography can be used to assess the microstructural properties of atherosclerotic tissue at micrometre scale resolution, but preselected analysis criteria must be understood in a critical interpretation of the results.

Arteriosclerosis↗
PubMed2003

A new approach for assessing early osteoarthritis in the rat.

Several animal models have been developed to investigate osteoarthritis and potential disease-modifying therapeutics. However, early disease data from these models are limited by the resolution of current imaging modalities. In this in-vitro study, an optical coherence tomography (OCT) system with an axial resolution of 15 micro m was used to track sequential changes in osteoarthritic rat knees. Osteoarthritis was induced via transection of the medial collateral ligament and an artificial full thickness meniscal tear. Imaging occurred at one, two, and three weeks after surgery. OCT successfully detected early signs of osteoarthritic change, including alteration of the cartilage surface and disruption of the bone-cartilage interface. This study demonstrates that OCT, along with the induction of mechanical injury, provides an excellent model for monitoring the sequential changes of osteoarthritis.

Animals↗
PubMed2003

New technology for assessing microstructural components of tendons and ligaments.

This study investigated the ability of optical coherence tomography (OCT), a recently developed technology with micron-scale resolution, to assess the microstructure of tendons and ligaments. In vitro structural- and polarization-sensitive OCT was performed on human ACL, Achilles tendon, and biceps tendon (obtained postmortem). Histology was performed on all imaged samples and compared to the corresponding OCT data. OCT images correlated well with histology. Most importantly, through polarization-sensitive OCT, the collagen in normal tissue was easily distinguished from the surrounding, supportive tissue due to the birefringent properties of organized collagen. Since the integrity of collagen is an important indicator of structural stability and pathologic state, the ability of OCT to assess collagen could be a powerful diagnostic tool in assessing tendon and ligament properties.

Humans↗
PubMed2001

High-resolution imaging of the middle ear with optical coherence tomography: a feasibility study.

BACKGROUND: Optical coherence tomography (OCT) is a new medical imaging technology that generates cross-sectional images of tissue microstructure with micron-scale resolution. Optical coherence tomography is analogous to ultrasound, measuring the intensity of infrared light rather than acoustical waves. OBJECTIVE: To demonstrate the feasibility of using OCT for ultra-high-resolution imaging of the middle ear via ex vivo imaging studies of human tissue. DESIGN: Images of the tympanic membrane and middle ear were acquired ex vivo, through the ear canal, without perforating the tympanic membrane. MATERIALS: Four excised intact temporal bones and the auditory apparatus were harvested from cadavers and imaged fresh, without previous fixation. RESULTS: The resulting images were compared with the gross sample and verified the ability of OCT to delineate relevant structures, such as the tympanic membrane and its sublayers, and the middle ear ossicles, nerves, and tendons at higher resolutions than possible with standard clinical imaging technologies. CONCLUSION: The ability of OCT to produce high-resolution images of tissue structure, without contact and in real time, as well as its ability to be integrated with endoscopes, suggests that this technology could become a useful modality for the diagnosis and management of a range of clinical middle ear abnormalities.

Ear, Middle↗
PubMed2001

Real-time optical coherence tomography for minimally invasive imaging of prostate ablation.

OBJECTIVE: Numerous ablation techniques have been developed to alleviate urethral obstruction and improve urodynamics in benign prostatic hyperplasia. Most techniques, however, rely on visual observation of surface changes for ablation end points. The feasibility of using real-time optical coherence tomography (OCT) for minimally invasive imaging to guide and monitor prostate resection is demonstrated with representative techniques of laser and radiofrequency ablation. Empiric comparisons of ablation dynamics are made, and the use of OCT as a high-resolution, subsurface modality for image guidance is evaluated. MATERIALS AND METHODS: Optical coherence tomography is a high-resolution, high-speed near-infrared imaging technique analogous to ultrasound imaging, except that reflections of light are detected rather than sound. High-speed OCT is used to image the dynamic process of laser and radiofrequency ablation of in vitro human prostate tissue. OCT images of ablation sites are compared with corresponding histology. RESULTS: Based on comparisons between OCT images and corresponding histology, OCT imaged transurethral prostate tissue morphology, including urethral sinuses and submucosal glands. Real-time OCT imaging provided rapid feedback and control of ablation dynamics. The compact and portable OCT technology is amenable to minimally invasive beam-delivery devices. CONCLUSIONS: Optical coherence tomography offers a minimally invasive means of assessing transurethral prostate morphology. Real-time OCT has the potential to provide image guidance of prostate resection for many of the existing surgical treatments directed at alleviating urethral obstruction associated with benign prostatic hyperplasia.

Catheter Ablation↗
PubMed2001

Correlation of collagen organization with polarization sensitive imaging of in vitro cartilage: implications for osteoarthritis.

OBJECTIVE: Optical coherence tomography (OCT), a new method of high resolution imaging, has shown feasibility for assessing articular cartilage to identify early changes in osteoarthritis (OA) and monitor therapy. OCT is analogous to ultrasound, measuring the intensity of backreflected infrared light rather than sound. The resolution of this technology is up to 25 times higher than existing methods. We investigated the correlation between changes observed by OCT and the degree of collagen organization in OA cartilage. METHODS: Polarization sensitive OCT (PSOCT) imaging was used to assess changes in cartilage collagen organization in vitro. RESULTS: The presence (or absence) of PSOCT changes correlated with collagen organization (or disorganization) on histology as assessed by picrosirius polarization microscopy (no significant difference). In multiple cases, cartilage was abnormal by both PSOCT and polarization microscopy, but was grossly normal by routine staining, showing cartilage thickness > 2 mm and no fibrillations. CONCLUSION: This in vitro study suggests PSOCT changes in cartilage are due to the state of collagen organization. The combination of high resolution structural imaging and birefringence detection make OCT a potentially powerful technology for early assessment of OA.

Cartilage, Articular↗
PubMed2000

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.

Coronary Artery Disease↗
PubMed2000

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

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 Barrett's 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.

Adenocarcinoma↗
PubMed2000

Optical coherence tomography: advanced technology for the endoscopic imaging of Barrett's esophagus.

BACKGROUND AND STUDY AIMS: Endoscopic optical coherence tomography (OCT) is an emerging medical technology capable of generating high-resolution cross-sectional imaging of tissue microstructure in situ and in real time. We assess the use and feasibility of OCT for real-time screening and diagnosis of Barrett's esophagus, and also review state-of-the-art OCT technology for endoscopic imaging. MATERIALS AND METHODS: OCT imaging was performed as an adjunct to endoscopic imaging of the human esophagus. Real-time OCT (13-microm resolution) was used to perform image-guided evaluation of normal esophagus and Barrett's esophagus. Beam delivery was accomplished with a 1-mm diameter OCT catheter-probe that can be introduced into the accessory channel of a standard endoscope. Different catheter-probe imaging designs which performed linear and radial scanning were assessed. Novel ultrahigh-resolution (1.1-microm resolution) and spectroscopic OCT techniques were used to image in vitro specimens of Barrett's esophagus. RESULTS: Endoscopic OCT images revealed distinct layers of normal human esophagus extending from the epithelium to the muscularis propria. In contrast, the presence of gland- and crypt-like morphologies and the absence of layered structures were observed in Barrett's esophagus. All OCT images showed strong correlations with architectural morphology in histological findings. Ultrahigh-resolution OCT techniques achieved 1.1-microm image resolution in in vitro specimens and showed enhanced resolution of architectural features. Spectroscopic OCT identified localized regions of wavelength-dependent optical scattering, enhancing the differentiation of Barrett's esophagus. CONCLUSIONS: OCT technology with compact fiberoptic imaging probes can be used as an adjunct to endoscopy for real-time image-guided evaluation of Barrett's esophagus. Linear and radial scan patterns have different advantages and limitations depending upon the application. Ultrahigh-resolution and spectroscopic OCT techniques improve structural tissue recognition and suggest future potential for resolution and contrast enhancements in clinical studies. A new balloon catheter-probe delivery device is proposed for systematic imaging and screening of the esophagus.

Barrett Esophagus↗
PubMed2000

Evaluation of the adaptive speckle suppression filter for coronary optical coherence tomography imaging.

During the last few years, optical coherence tomography (OCT) has demonstrated considerable promise as a method of high-resolution intravascular imaging. The goal of this study was to apply and to test the applicability of the rotating kernel transformation (RKT) technique to the speckle reduction and enhancement of OCT images. The technique is locally adaptive. It is based on sequential application of directional masks and selection of the maximum of all outputs. This method enhances the image features by emphasizing thin edges while suppressing a noisy background. Qualitatively, the RKT algorithm provides noticeable improvement over the original image. All processed images are smoother and have better-defined borders of media, intima, and plaque. The quantitative evaluation of RKT performance showed that in terms of average contrast-to-noise ratio, there is a significant improvement in image quality between original and enhanced images. The RKT image enhancement technique shows great promise in improving OCT images for superior boundary identification.

Coronary Angiography↗
PubMed1999

High-resolution optical coherence tomography-guided laser ablation of surgical tissue.

BACKGROUND: Optical coherence tomography (OCT) is a compact high-speed imaging technology which uses infrared light to acquire cross-sectional images of tissue on the micrometer scale. Because OCT images are based on the optical backscattering properties of tissue, changes in tissue optical properties due to surgical laser ablation should be detectable using this technique. In this work, we examine the feasibility of using real-time OCT imaging to guide the placement and observe the dynamics of surgical laser ablation in a variety of tissue types. MATERIALS AND METHODS: More than 65 sites on five ex vivo rat organ tissue types were imaged at eight frames per second before, during, and after laser ablation. Ablation was performed with a coincident continuous wave argon laser operating at 514-nm wavelength and varying exposure powers and durations. Following imaging, tissue registration was achieved using microinjections of dye followed by routine histologic processing to confirm the morphology of the ablation site. RESULTS: High-speed OCT imaging at eight frames per second permitted rapid tissue orientation and guided ablation in numerous organ specimens. Acquisition rates were fast enough to capture dynamic changes in optical backscatter which corresponded to thermal tissue damage during laser ablation. CONCLUSIONS: The ability of high-resolution high-speed OCT to guide laser ablation and image the dynamic changes suggests a role in image-guided surgical procedures, such as the ablation of neoplasms. Future in vivo studies are necessary to demonstrate performance intraoperatively.

Abdominal Muscles↗
PubMed1999

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.

Endometriosis↗
PubMed1999

High resolution in vivo intra-arterial imaging with optical coherence tomography.

BACKGROUND: Optical coherence tomography (OCT) is a new method of catheter based micron scale imaging. OCT is analogous to ultrasound, measuring the intensity of backreflected infrared light rather than sound waves. OBJECTIVE: To demonstrate the ability of OCT to perform high resolution imaging of arterial tissue in vivo. METHODS: OCT imaging of the abdominal aorta of New Zealand white rabbits was performed using a 2.9 F OCT imaging catheter. Using an ultrashort pulse laser as a light source for imaging, an axial resolution of 10 micrometer was achieved. RESULTS: Imaging was performed at 4 frames/second and data were saved in either super VHS or digital format. Saline injections were required during imaging because of the signal attenuation caused by blood. Microstructure was sharply defined within the arterial wall and correlated with histology. Some motion artefacts were noted at 4 frames/second. CONCLUSIONS: In vivo imaging of the rabbit aorta was demonstrated at a source resolution of 10 micrometer, but required the displacement of blood with saline. The high resolution of OCT allows imaging to be performed near the resolution of histopathology, offering the potential to have an impact both on the identification of high risk plaques and the guidance of interventional procedures.

Animals↗
PubMed1999

High resolution imaging of transitional cell carcinoma with optical coherence tomography: feasibility for the evaluation of bladder pathology.

Significant challenges regarding patient morbidity and mortality remain in the management of transitional cell carcinoma (TCC). Among the most important of these challenges is the inability to identify early neoplastic changes and to assess the degree of tumour invasion into the bladder wall in vivo. Optical coherence tomography (OCT) has been recently developed to provide in situ, high resolution, catheter/endoscope based imaging. This study explored the feasibility of OCT for the evaluation of bladder pathology. Both in vitro and in vivo studies were performed. In vitro imaging of pathological human bladder was performed and compared with normal specimens and histopathology. In vivo imaging of normal rabbit bladder was also performed with our current catheter/endoscope based systems. In the in vitro studies, OCT was able to delineate normal microstructure of the bladder, such as the mucosa, submucosa and muscularis layers. This was in contrast to specimens of invasive carcinoma, where a disruption of the normal bladder wall architecture was seen. The in vivo experiment demonstrated current limitations of the catheter/endoscope based systems and provided valuable information for developing an improved system for bladder imaging. The ability of OCT to delineate microstructure of the bladder wall suggests feasibility for endoscopic based imaging. In particular, there is a potential role envisioned for OCT in the management of TCC, identifying pre-malignant states and the depth of tumour invasion.

Animals↗
PubMed1999

High resolution imaging of normal and osteoarthritic cartilage with optical coherence tomography.

OBJECTIVE: We describe optical coherence tomography (OCT), a high resolution micron scale imaging technology, for assessment of osteoarthritic articular cartilage microstructure. OCT is analogous to ultrasound, measuring the intensity of backreflected infrared light rather than acoustical waves. METHODS: OCT imaging was performed on over 100 sites on 20 normal and osteoarthritic cartilage specimens in vitro. RESULTS: Microstructures that were identified included fibrillations, fibrosis, cartilage thickness, and new bone growth at resolutions between 5 and 15 microm. In addition, the polarization sensitivity of imaging suggested a diagnostic role of polarization spectroscopy. CONCLUSION: OCT represents an attractive new technology for intraarticular imaging due to its high resolution (greater than any available clinical technology), ability to be integrated into small arthroscopes, compact portable design, and relatively low cost.

Arthrography↗
PubMed1999

High-resolution imaging of gynecologic neoplasms using optical coherence tomography.

BACKGROUND: A modality capable of imaging the female reproductive tract, at or near the cellular level, could lead to the detection of diseases at earlier stages than currently possible. Optical coherence tomography achieves high resolutions in the cellular range (4-20 microm) and could accomplish that level of detection. METHOD: Optical coherence tomography imaging of gynecologic tissue was studied in vitro on normal and neoplastic human cervical and uterine tissue. EXPERIENCE: The structures of the normal ectocervix and endocervix, including epithelium, basal membrane, and glands, were identified clearly. These findings were compared with changes associated with carcinoma in situ and invasive carcinoma. The optical coherence tomography images of the uterus also showed changes between microstructural features of normal tissue and endometrial adenocarcinoma. CONCLUSION: Optical coherence tomography of tissue microstructures showed potential for powerful, minimally invasive assessment of the female reproductive tract at a resolution greater than any current clinical imaging method.

Feasibility Studies↗