There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

The American Society for Testing and Materials (ASTM) is an independent organization devoted to the development of standards.

American Society for Testing and Materials

비만아 부모의 돌봄 경험: q 방법론

Purpose: This pilot study was aimed to demonstrate the clinical feasibility of using hyperspectral computed tomographic spectroscopy to measure blood oxygen content in human retinal vessels. Methods: All procedures were performed under a University of Southern California Institutional Review Board–approved protocol and after obtaining informed consent. Fifty-seven subjects with and without diabetic retinopathy were dilated for standard fundus photography. Fundus photographs and retinal vascular oxygen measurements (oximetry) were made using a custom-made hyperspectral computed tomographic imaging spectrometer coupled to a standard fundus camera. Oximetry measurements were made along arteries (Aox) and veins (Vox) within vessel segments that were 1 to 2 disk diameters from the optic disk. Results: For all control subjects (n = 45), mean Aox and Vox were 93 ± 7% and 65 ± 5% (P = 0.001), respectively. For all diabetic subjects (n = 12), mean Aox and Vox were 90 ± 7% and 68 ± 5% (P = 0.001), respectively. In subjects with proliferative diabetic retinopathy, Aox was significantly lower, and Vox was significantly higher than other groups (85 ± 4% and 71 ± 4%, respectively; P = 0.04, analysis of variance). There was a highly significant difference in the arteriovenous difference between subjects with proliferative diabetic retinopathy and those in the control group (14 vs. 26%, P = 0.003). Conclusion: Hyperspectral computed tomographic spectroscopy is a clinically feasible method for measurement and analysis of vascular oxygen content in retinal health and disease. This study uses the techniques relevant to oximetry; however, the breadth of spectral data available through this method may be applicable to study other anatomical and functional features of the retina in health and disease.

/pdf/noninvasive-assessment-of-retinal-vascular-oxygen-content-1dhzr52hue.pdf

Noninvasive assessment of retinal vascular oxygen content among normal and diabetic human subjects: a study using hyperspectral computed tomographic imaging spectroscopy.

A cannula is described having a housing, a first lumen, a second lumen, and a port capable of fluid communication with the first lumen. The second lumen configured to receive fluid from the first lumen and to direct the fluid to a surgical site. A light emitting diode light source is positionable within the housing and configured to direct light through the second lumen to the surgical site.

Self contained illuminated infusion cannula systems and methods and devices

Objective: Current elastography techniques in the field of ophthalmology usually target one specific tissue, such as the cornea or the sclera. However, the eye is an inter-related organ, and some ocular diseases can alter the biomechanical properties of multiple anatomical structures. Hence, there is a need to develop an imaging tool that can non-invasively, quantitatively, and accurately characterize dynamic changes among these biomechanical properties. Methods: A high resolution ultrasound elastography system was developed to achieve this goal. The efficacy and accuracy of the system was first validated on tissue-mimicking phantoms while mechanical testing measurements served as the gold standard. Next, an in vivo elevated intraocular pressure (IOP) model was established in rabbits to further test our system. In particular, elastography measurements were obtained at 5 IOP levels, ranging from 10 mmHg to 30 mmHg in 5 mmHg increments. Spatial-temporal maps of the multiple ocular tissues (cornea, lens, iris, optic nerve head, and peripapillary sclera) were obtained. Results. The spatial-temporal maps were acquired simultaneously for the ocular tissues at the 5 different IOP levels. The statistical analysis of the elastic wave speed was presented for ocular tissues. Finally, the mapping for the elastic wave speed of each ocular component was acquired at each IOP level. Conclusion: Our elastography system can concurrently assess the biomechanical properties of multiple ocular structures and detect changes in biomechanical properties associated with changes in IOP. Significance: This system provides a novel tool to measure and quantify the biomechanical properties of the whole eye.

Simultaneous Assessment of the Whole Eye Biomechanics Using Ultrasonic Elastography

Biological Considerations for an Intraocular Retinal Prosthesis.- Artificial Vision: Vision of a Newcomer.- The Effects of Visual Deprivation: Implications for Sensory Prostheses.- Prosthetic Vision Simulation in Fully and Partially Sighted Individuals.- Testing Visual Functions in Patients with Visual Prostheses.- The IMI Retinal Implant System.- Challenges in Realizing a Chronic High-Resolution Retinal Prosthesis.- Large-scale Integration-Based Stimulus Electrodes for Retinal Prosthesis.- Development of a Wireless High-Frequency Microarray Implant for Retinal Stimulation.- Visual Prosthesis Based on Optic Nerve Stimulation with Penetrating Electrode Array.- Dynamic Interactions of Retinal Prosthesis Electrodes with Neural Tissue and Materials Science in Electrode Design.- In Vitro Determination of Stimulus-Induced pH Changes in Visual Prostheses.- Electrochemical Characterization of Implantable High Aspect Ratio Nanoparticle Platinum Electrodes for Neural Stimulations.- High-Resolution Opto-Electronic Retinal Prosthesis: Physical Limitations and Design.- Computational Modeling of Electromagnetic and Thermal Effects for a Dual-Unit Retinal Prosthesis: Inductive Telemetry, Temperature Increase, and Current Densities in the Retina.- Microstimulation with Chronically Implanted Intracortical Electrodes.- A Tissue Change After Suprachoroidal-Transretinal Stimulation with High Electrical Current in Rabbits.- Electrical Stimulation of Mammalian Retinal Ganglion Cells Using Dense Arrays of Small-Diameter Electrodes.- A Mechanism for Generating Precise Temporal Patterns of Activity Using Prosthetic Stimulation.- Electrophysiology of Natural and Artificial Vision.

Artificial sight : basic research, biomedical engineering, and clinical advances

Implanted drug pump devices can be refilled with a refill needle inserted through a fill port in the drug reservoir of the drug pump device. Proper needle insertion may be verified visually or using electrical, magnetic, optical, acoustic, or other suitable sensing mechanisms.

Mark S. Humayun

Papers

Noninvasive assessment of retinal vascular oxygen content among normal and diabetic human subjects: a study using hyperspectral computed tomographic imaging spectroscopy.

Self contained illuminated infusion cannula systems and methods and devices

Simultaneous Assessment of the Whole Eye Biomechanics Using Ultrasonic Elastography

Artificial sight : basic research, biomedical engineering, and clinical advances

Implantable drug pumps and refill devices therefor