Biomedical subjects

Aaron Benson

Publications and source records attributed to Aaron Benson.

3 recordsLinked to original sources

PubMed2005

Statins and cognition: what can we learn from existing randomized trials?

BACKGROUND: Statins are being developed as treatments for Alzheimer's dementia based on evidence from preclinical and observational studies. However, cholesterol plays an integral role in cell membrane signal transduction and suboptimal cholesterol level could potentially impair neuronal function. Additionally, results of observational nonrandomized studies may have been affected by treatment bias. METHODS: We performed a systematic literature review in MEDLINE from January 1966 to July 2004 and included published prospective, randomized, and placebo-controlled human studies that examined the cognitive effects of statins. RESULTS: Nine studies with sample sizes ranging from 22 to 20,000 and duration of 3 weeks to 5 years, met criteria for review. Study populations and cognitive outcomes varied. Four studies were >6 months or longer. Overall, none of these studies reported finding a positive benefit for any statin on cognition in non-demented subjects although there was inconsistent evidence for acute cognitive worsening in some studies. CONCLUSION: While statins intuitively have appeal for the prevention or treatment of dementia, any conclusions about their efficacy should await more definitive evidence from on-going prospective clinical trials.

Alzheimer Disease↗

PubMed2005

Simulating the continuous curvilinear capsulorhexis procedure during cataract surgery on the EYESI system.

This paper describes a technique for simulating the capsulorhexis procedure during cataract surgery on the EYESI system. The continuous curvilinear capsulorhexis technique can be a difficult procedure for beginning ophthalmology surgeons. In the initial phase of tearing the tissue, the tear vector is tangential to the circumference of the tear circle. However, without the proper re-grasping of the flap of torn tissue close to the tear point, the tear vector angle quickly runs downhill possibly causing severe damage to the tissue. Novice surgeons tend to try to complete the capsulorhexis without the time consuming re-grasping of the tissue flap. Other factors such as anterior bowing of the lens diaphragm, patient age, and shallow anterior chambers add to the problematic nature of the procedure. The tissue area is modeled as a curvilinear mesh of nodes and springs. Deformation is accomplished via a physically based particle model utilizing a heuristic algorithm to constrain the deformation calculations to the locality of the tear area to speed up computations. The training software alerts the user of any potential tear problems before they occur thus instructing the novice surgeon. The EYESI hardware system (from VRMagic GmbH) provides the user with stereoscopic images thus providing 3D viewing. Our capsulorhexis simulator software models a number of tear problems and anomalies to provide a useful training environment without the dangers of using live patients.

Capsulorhexis↗

PubMed2005

Using an approximation to the euclidean skeleton for efficient collision detection and tissue deformations in surgical simulators.

This paper describes a technique for efficient collision detection and deformation of abdominal organs in surgical simulation using an approximation of the Euclidean skeleton. Many researchers have developed surgical simulators, but one of the most difficult underlying problems is that of organ-instrument collision detection followed by the deformation of the tissue caused by the instrument. Much of the difficulty is due to the vast number of polygons in high resolution complex organ models. A high resolution gall bladder model for instance can number in the tens of thousands of polygons. Our methodology utilizes the reduction power of the skeleton to reduce computations. First, we recursively compute approximations to the Euclidean skeleton to generate a set of skeletal points for the organ. Then we pre-compute for each vertex in each polygon the associated skeleton point (minimal distance discs). A spring is then connected from each vertex to its associated skeleton point to be used in the deformation algorithm. The data structure for the organ thus stores for each skeletal point its maximum and minimum distances and the list of associated vertices. A heuristic algorithm using the skeleton structure of the instrument and the skeleton of the organ is used to determine instrument collisions with the organ.

Computer Simulation↗