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Biomedical subjects

S Yazdanfar

Publications and source records attributed to S Yazdanfar.

At least 19 recordsLinked to original sources
PubMed2003

Electrostatic micromachine scanning mirror for optical coherence tomography.

Compact electrostatic micromirror structures for use in the scanning arm of an optical coherence tomography (OCT) system are described. These devices consist of millimeter-scale mirrors resting upon micrometer-scale polyimide hinges that are tilted by a linear micromachine actuator, the integrated force array (IFA). The IFA is a network of deformable capacitor cells that electrostatically contract with an applied voltage. The support structures, hinges, and actuators are fabricated by photolithography from polyimide-upon-silicon wafers. These devices were inserted into the scanning arm of an experimental OCT imaging system to produce in vitro and in vivo images at frame rates of 4 to 8 Hz.

Electricity↗
PubMed2001

Real-time optical coherence tomography of the anterior segment at 1310 nm.

BACKGROUND: Recent advances in high-speed scanning technology have enabled a new generation of optical coherence tomographic (OCT) systems to perform imaging at video rate. Here, a handheld OCT probe capable of imaging the anterior segment of the eye at high frame rates is demonstrated for the first time. OBJECTIVE: To demonstrate real-time OCT imaging of anterior segment structures. DESIGN: Survey of anterior segment structures in normal human subjects. SETTING: Laboratory. MAIN OUTCOME MEASURES: Achieving real-time imaging of the anterior segment, satisfactory image quality, and convenience of a handheld probe. RESULTS: Optical coherence tomographic imaging of the anterior segment of the eyes of human subjects was performed using 1310-nm wavelength light with an image rate of 8 frames per second. Imaging trials demonstrated clear resolution of corneal epithelium and stroma, sclerocorneal junction, sclera, iris pigment epithelium and stroma, and anterior lens capsule. The anterior chamber angle was clearly visualized. Limited imaging of the ciliary body was performed. Real-time imaging of pupillary constriction in response to light stimulus was also performed. CONCLUSION: High-speed OCT at 1310-nm wavelength is a potentially useful technique for noninvasive assessment of anterior segment structures. CLINICAL RELEVANCE: Our results suggest that real-time OCT has potential applications in glaucoma evaluation and refractive surgery.

Anterior Chamber↗
PubMed2001

Photothermal coagulation of blood vessels: a comparison of high-speed optical coherence tomography and numerical modelling.

Optical-thermal models that can accurately predict temperature rise and damage in blood vessels and surrounding tissue may be used to improve the treatment of vascular disorders. Verification of these models has been hampered by the lack of time- and depth-resolved experimental data. In this preliminary study, an optical coherence tomography system operating at 4-30 frames per second was used to visualize laser irradiation of cutaneous (hamster dorsal skin flap) blood vessels. An argon laser was utilized with the following parameters: pulse duration 0.1-2.0 s, spot size 0.1-1.0 mm, power 100-400 mW. Video microscopy images were obtained before and after irradiations, and optical-thermal modelling was performed on two irradiation cases. Time-resolved optical coherence tomography and still images were compared with predictions of temperature rise and damage using Monte Carlo and finite difference techniques. In general, predicted damage agreed with the actual blood vessel and surrounding tissue coagulation seen in images. However, limitations of current optical-thermal models were identified, such as the inability to model the dynamic changes in blood vessel diameter that were seen in the optical coherence tomography images.

Animals↗
PubMed1999

Use of stents to treat kinks causing obstruction in a left internal mammary artery graft.

Left internal mammary arteries (LIMA) are used routinely as grafts to the left anterior descending coronary artery (LAD) in selected patients undergoing coronary artery bypass graft (CABG) surgery because of better long-term patency rates. Pathology other than fibrointimal hyperplasia, accelerated atherosclerosis, or thrombus can sometimes cause obstructive lesions in such grafts. This report illustrates a kink in a LIMA graft to the LAD causing an obstructive lesion shortly after surgery and describes the subsequent management of this lesion with intracoronary stents.

Adult↗
PubMed1999

Coronary dissection and thrombosis associated with exercise testing three months after successful coronary stenting.

Exercise testing is commonly performed to assess the functional result of coronary revascularization procedures and is usually not associated with any complications. However, this report documents a rare case of coronary dissection and thrombosis, which resulted in an acute myocardial infarction, in a patient who underwent stress testing 3 months following successful coronary stent implantation.

Aged↗
PubMed1999

Three-dimensional reconstruction of blood vessels from in vivo color Doppler optical coherence tomography images.

PURPOSE: Current laser treatment for vascular disorders such as port wine stains can have incomplete or unacceptable results. A customized treatment strategy based on knowledge of the patient's blood vessel structure may effect an improved clinical outcome. PROCEDURE: We tested the feasibility of using color Doppler optical coherence tomography (OCT) and image processing techniques to locate, measure and reconstruct cutaneous blood vessels in rat and hamster skin. OCT is a recent, potentially noninvasive technique for imaging subsurface tissue structures with micrometer scale resolution. RESULTS: Blood vessels were identified in a series of cross-sectional images, then a three-dimensional reconstruction was made. Parameters that can affect optimum laser treatment parameters, such as average blood vessel depth and luminal diameter, were found from the images. CONCLUSION: This study shows that color Doppler OCT is a potential tool for improving laser treatment of vascular disorders.

Animals↗
PubMed1999

Hypoxia due to patent foramen ovale in the absence of pulmonary hypertension.

In most patients with a patent foramen ovale, blood flows from the left atrium to the right atrium in the absence of pulmonary hypertension. Our report describes a patient with a patent foramen ovale in whom flow occurred from the right atrium to the left atrium in the absence of pulmonary hypertension. We discuss hemodynamic findings and present a brief review of the pertinent medical literature regarding this phenomenon. We also discuss the role of transesophageal echocardiography in the diagnosis of this condition and in the elucidation of the underlying mechanisms, and we suggest several mechanisms that may explain the occurrence of this phenomenon in our patient.

Aged↗
PubMed1998

Fatal alveolar hemorrhage and Abciximab (ReoPro) therapy for acute myocardial infarction.

We describe two cases of diffuse alveolar hemorrhage and development of ARDS in patients who underwent percutaneous transluminal coronary angioplasty (PTCA) with stenting in whom Abciximab (ReoPro) was used in combination with other agents interfering with the hemostatic mechanism. The development of pulmonary infiltrates, associated with a fall in hemoglobin after the administration of Abciximab, should strongly suggest the possibility of diffuse alveolar hemorrhage. Physicians should be aware of the possible association between the use of Abciximab and the development of alveolar hemorrhage.

Abciximab↗
PubMed1997

Guide catheter exchange techniques: bi-coaxial and other methods.

Maintaining the position of a guidewire across coronary artery lesions during angioplasty is important to allow rapid and reliable access. Stabilizing these small caliber angioplasty guidewires during guide catheter replacement is often difficult, if not impossible at times. This article reviews the techniques for exchanging guide catheters while maintaining coronary guidewire position. It also introduces the bi-coaxial guide catheter exchange technique.

Angioplasty, Balloon, Coronary↗
PubMed1994

Directional coronary atherectomy can be successfully performed in the elderly.

The influence of age on the clinical and angiographic outcome of directional coronary atherectomy is evaluated. Results demonstrate that DCA can be performed successfully in the vast majority (78.7-90%) of patients in all age groups. However, there is a non-statistical trend toward decreased success rates in the elderly (P > .05). Major ischemic complications and groin complications tend to be more common in the elderly (P > .05). Blood transfusions are required significantly more often in the elderly (P < .05). Directional coronary atherectomy is a useful method of coronary artery revascularization in all age groups, including the elderly.

Aged↗
PubMed1994

Internal mammary artery collateral to the external iliac artery: an angiographic consideration prior to coronary bypass surgery.

The role of routine selective angiography of the internal mammary artery prior to myocardial revascularization is controversial. We report a patient with coronary artery disease and peripheral vascular disease in whom the left internal mammary artery supplied blood flow to the left external iliac artery via a collateral network. Thus, selective angiography of the internal mammary artery did play a major role in the proper management of this patient who required coronary bypass surgery. A major potential postoperative complication of left lower extremity ischemia may have been prevented.

Aged↗
PubMed1994

Angiographic evidence of right coronary bridging.

Systolic constriction of the left anterior descending coronary artery is a well-recognized angiographic and autopsy finding. The etiology of this phenomenon is an intramural course of the coronary artery. Even though there has been autopsy evidence of an intramural course of the right coronary artery, this rare finding has not been associated with systolic constriction, "bridging" on coronary angiography. There is evidence that strenuous exercise can induce ischemia in an intramural left coronary artery. We therefore present a case report of angiographic evidence of systolic constriction of the right coronary artery.

Aged↗
PubMed1994

Directional coronary atherectomy in women compared with men.

The influence of gender on the procedural outcome of directional coronary atherectomy (DCA) is controversial. This study of 373 consecutive patients (418 lesions) undergoing DCA demonstrates that the procedural success rate of DCA is significantly lower in women compared with men (72.7 vs. 82.9%, p = 0.011). Women have significantly smaller coronary arteries than men (2.5 mm vs. 2.7 mm, p = 0.028) and were older than men (66 vs. 61 years, p = 0.0001). Multivariate analysis identifies small coronary vessel size rather than female gender per se as an independent predictor of poor procedural outcome. Procedural success rates in women with coronary vessel size > or = 2.5 mm is significantly higher (92.2%) than in women with coronary vessel size < 2.5 mm (73.1%), and parallels that in men with vessel size > or = 2.5 mm (89.3%). Inability to engage the ostium of the coronary artery adequately with the guiding catheter and to cross the lesion with the atherectomy device is significantly more common in women compared with men. Major ischemic complication rates are similar in women and men (8.5 vs. 8.7%). Groin complications are significantly more common in women compared with men (13.5 vs. 2.9%). We conclude that procedural success rates in women may be improved by careful patient selection, with particular attention to small vessel size. DCA is best performed in vessels > 2.5 mm in diameter.

Aged↗