Biomedical subjects

Steven Barrett

Publications and source records attributed to Steven Barrett.

6 recordsLinked to original sources

PubMed2007

Cancer risks in thiazolidinedione users compared to other anti-diabetic agents.

PURPOSE: We conducted three nested case-control studies to evaluate the risk of breast, colon, and prostate cancers developing in patients exposed to thiazolidinediones (TZDs) compared with other anti-diabetic agents. METHODS: Cancer cases were matched to five controls by age, gender, calendar year, and time in the database from a cohort of 1 26 971 diabetic patients taking anti-diabetic medication in the US Integrated Healthcare Information Services database. Five hundred thirteen breast cancer cases were matched with 2557 controls, 408 cases of colon cancer were matched with 2027 controls and 643 cases of prostate cancer were matched with 3176 controls. Exposure to an anti-diabetic agent within 90 days preceding the index date was defined as recent exposure and at any time during the follow-up was defined as ever exposed. RESULTS: The adjusted odds ratios and 95%CI of cancer from ever exposure to TZDs compared to oral monotherapy, oral dual therapy, oral triple therapy, insulin monotherapy, insulin and oral therapy and all non-TZD anti-diabetic agents were, respectively for breast cancer: 0.91 (0.69-1.20), 0.80 (0.56-1.14), 0.87 (0.32-2.35), 1.27 (0.61-2.67), 0.71 (0.36-1.37), 0.89 (0.68-1.15); for colon cancer: 1.06 (0.80-1.40), 1.12 (0.77-1.63), 1.73 (0.39-7.78), 4.46 (1.05-19.00), 1.06 (0.50-2.26) 1.03 (0.80-1.32) and for prostate cancer: 1.08 (0.85-1.37), 0.89 (0.66-1.21); 0.82 (0.33-2.06); 1.80 (0.79-4.07), 1.10 (0.55-2.18), 1.04 (0.83-1.31). Results for exposure within 90 days of the date of the cancer were similar. CONCLUSIONS: Our findings suggest that the effect of TZDs on the likelihood of development of the cancers studied (colon, prostate and breast) appears to be neutral and do not support a beneficial or deleterious effect of TZD on the cancers studied.

Administration, Oral↗

PubMed2006

Further safety enhancement of a specialized power assisted tricycle for a child with osteogenesis imperfecta type III and design of an adjustble hand power tricycle.

Several tricycles, one a customized power assisted tricycle, and the second a hand powered tricycle were developed, which offered a unique opportunity to serve multiple purposes in several children's development throughout Wyoming. In Both cases these tricycles provide the children with the opportunity to gain muscle mass, strength, coordination, and confidence. The power assisted tricycle was completed as a senior design project in 2002, and over time safety enhancements have been completed to make the tricycle safer for operation. Unfortunately, the safety system enhancements were not acceptable for it to be released for use. For this reason the tricycle was further redesigned to include more redundant safety systems which will allow the tricycle to be safe for the child's use. The second tricycle was designed to allow for a group of children who have limited use of their legs, to be able to use the same tricycle to give them more upper body strength. A gear system using multiple gear sprockets was adapted to a preexisting tricycle to provide hand power rather than foot power. Without these improvements, the children would not have the opportunity to use these tricycles to help with their development.

Bicycling↗

PubMed2005

Next generation autonomous wheelchair control.

Often times the physically challenged, limited to a wheelchair, also have difficulty with vision. In order to help, something must "see" for them. Therefore there must be some way for a wheelchair to know its environment, sense where it is, and where it must go. It also must be able to avoid any obstacles which are not normally part of the environment. An autonomous wheelchair will serve an important role by allowing users more freedom and independence. This design challenge is broken into four major steps: wheelchair control, environment recognition, route planning, and obstacle avoidance. The first step is to reverse engineer a wheelchair and rebuild the controls, which will be the main topic of discussion for this paper. Two big challenges with this step are high power motor control and joystick control. An H-bridge motor interface, controlled by a microprocessor, was designed for the motors. The joystick control is handled with the same microprocessor.

Artificial Intelligence↗

PubMed2005

Software model of a machine vision system based on the common house fly.

The vision system of the common house fly has many properties, such as hyperacuity and parallel structure, which would be advantageous in a machine vision system. A software model has been developed which is ultimately intended to be a tool to guide the design of an analog real time vision system. The model starts by laying out cartridges over an image. The cartridges are analogous to the ommatidium of the fly's eye and contain seven photoreceptors each with a Gaussian profile. The spacing between photoreceptors is variable providing for more or less detail as needed. The cartridges provide information on what type of features they see and neighboring cartridges share information to construct a feature map.

Algorithms↗

PubMed2003

Automated Abdominal Aortic Aneurysm segmentation using MATLAB.

Abdominal Aortic Aneurysms (AAA) are the 10th leading cause of death in older men. It is estimated that about 5% of men over 50 have AAA but the prevalence and risk of death due to rupture increase with age to estimated 10% prevalence and almost 1% of male deaths over the age of 65. AAA is defined as a focal dilation of the artery at least 50% larger than the normal diameter. If the defect is not surgically repaired prior to rupture, the mortality is about 80%. The role of clotted blood (thrombus) lining the walls of the AAA has been speculated to play a role in aneurysm expansion. Although aneurysm diameter is easily measured from a CT scan, accurately measuring the relative amount of clotted blood (thrombus load) cannot be readily done with a ruler. This paper presents a process to segment the relative thrombus area and aneurysmal area from CT images using computer algorithms. We have developed an image processing based technique, using MATLAB, to aid in the detection of a threatening AAA condition. This technique uses segmentation-based techniques to extract the desired data. The process of segmentation involves several steps to obtain desirable results. This algorithm uses primarily thresholding techniques, erosion, and dilation filters to segment the wall and determine the bounds of the aorta; then segmentation is done to enhance and isolate areas of interest.

Algorithms↗

PubMed2002

Computer-assisted laser photocoagulation of the retina--a hybrid tracking approach.

A system for robotically assisted retinal surgery has been developed to rapidly and safely place lesions on the retina for photocoagulation therapy. This system provides real-time, motion stabilized lesion placement for typical irradiation times of 100 ms. The system consists of three main subsystems: a digital-based global tracking subsystem; a fast, analog local tracking subsystem; and a confocal reflectance subsystem to control lesion parameters dynamically. We have reported previously on these individual subsystems. This paper concentrates on the development of a second hybrid system prototype. Considerable progress has been made toward reducing the footprint of the optical system, simplifying the user interface, fully characterizing the analog tracking system, using measurable lesion reflectance parameters to develop a noninvasive method to infer lesion depth, and integrating the subsystems into a seamless hybrid system. These system improvements and progress toward a clinically significant system are covered in detail within this paper. The tracking algorithms and concepts developed for this project have considerable potential for application in many other areas of biomedical engineering.

Biomedical Engineering↗