Analysis of the intraocular jet flows and pressure gradients induced by air and fluid infusion: mechanism of focal chorioretinal damage.

PURPOSE: To comprehend the mechanism of focal chorioretinal damage by analysis of the pressure distribution and dynamic pressure induced by infused air during fluid-air exchange. METHODS: A precise simulation featuring a model eye and a fluid circuit was designed to analyze fluid-air exchange. The pressure distribution, flow velocity, and dynamic pressure induced by infusion of air into an air-filled eye were analyzed using an approach based on fluid dynamics. The size of the port and the infusion pressure were varied during simulated iterations. We simulated infusion of an air-filled eye with balanced salt solution (BSS) to better understand the mechanism of chorioretinal damage induced by infused air. RESULTS: Infused air was projected straight toward a point on the retina contralateral to the infusion port (the "vulnerable point"). The highest pressure was evident at the vulnerable point, and the lowest pressure was recorded on most retinal areas. Simulations using greater infusion pressure and a port of larger size were associated with elevations in dynamic pressure and the pressure gradient. The pressure gradients were 2.8 and 5.1 mm Hg, respectively, when infusion pressures of 30 and 50 mm Hg were delivered through a 20-gauge port. The pressure gradient associated with BSS infusion was greater than that created by air, but lasted for only a moment. CONCLUSIONS: Our simulation explains the mechanism of focal chorioretinal damage in numerical terms. Infused air induces a prolonged increase in focal pressure on the vulnerable point, and this may be responsible for visual field defects arising after fluid-air exchange.

A study on the correlation between patients' physical characteristics and effective dose of liver computed tomography.

This suggests indicators to be considered in the protocol for setting up equipment and minimizing patient doses by identifying the effective dose and correlations of each equipment company according to a patient's body characteristics in liver CT. The study was conducted with 445 patients who went to the hospital and received liver CT at the diagnostic radiology department of S medical center from 2010 January to June. As the statistical methods, t-test, one-way ANOVA, and Pearson's correlation analysis were used. The study results show that as height, weight, and BMI increased, the effective dose increased with all equipment vendors. Correlations between a patient's body characteristics and the effective dose were shown to be positive with all equipment vendors in regard to weight, BMI, and height, in order.