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Biomedical subjects

Srinivasan Rajagopalan

Publications and source records attributed to Srinivasan Rajagopalan.

4 recordsLinked to original sources

Tissue engineering templates using minimal surfaces.

The status quo of tissue engineering can be summarized as "a random walk through the design space". The existing scaffold designs based on computeraided design (CAD) and solid freeform fabrication (SFF) are anti-biomorphic and mechanically weak cubic partitions with sharp edges. We introduce minimal surface based unit cells to create biomorphic scaffolds with optimal stress/strain distribution and superior mechanical strength.

Computer Simulation↗

Optimal segmentation of microcomputed tomographic images of porous tissue-engineering scaffolds.

The morphometric properties of the porous tissue-engineering scaffolds play a dominant role in the initial cell attachment and subsequent tissue regeneration. These properties can be derived nondestructively with the use of quantitative analysis of high-resolution microcomputed tomography (microCT) imaging of scaffolds. Accurate segmentation of these acquired images into solid and porous subspaces is critical to the integrity of morphometric analysis. The absence of a single image-processing technique to provide such accurate separability immune to all the intricacies of the acquired data makes this seemingly simple task significantly error prone. Consequently, an optimal segmentation has to be selected by ranking the segmentations produced by a multiplicity of methods. This article proposes a robust, easy-to-implement, unambiguous, signal-processing-based, ground-truth-free, segmentation rating metric that correlates with visual acuity. With the use of this metric it is possible, for the first time, to threshold the data with a wide range of techniques and select automatically the technique that best delineates the acquired image. The proposed solution has been extensively tested on microCT images of scaffolds fabricated with biodegradable poly (propylene fumarate) (PPF) with the use of a solvent casting particulate leaching process. The approaches proposed and the results obtained may have profound implications for accurate image-based characterization of tissue-engineering scaffolds.

Biocompatible Materials↗

Enhancing profitability of dry mill ethanol plants: process modeling and economics of conversion of degermed defibered corn to ethanol.

An Aspen Plus modeling platform was developed to evaluate the performance of the conversion process of degermed defibered corn (DDC) to ethanol in 15- and 40-million gallons per year (MGPY) dry mill ethanol plants. Upstream corn milling equipment in conventional dry mill ethanol plants was replaced with germ and fiber separation equipment. DDC with higher starch content was fed to the existing saccharification and fermentation units, resulting in higher ethanol productivity than with regular corn. The results of the DDC models were compared with those of conventional dry mill ethanol process models. A simple financial analysis that included capital and operating costs, revenues, earnings, and return on investment was created to evaluate each model comparatively. Case studies were performed on 15- and 40-MGPY base case models with two DDC process designs and DDC with a mechanical oil extraction process.

Biotechnology↗

Interrogative visualization: embedding deformation and Constructive Solid Geometry into volume visualization.

Existing volume visualization algorithms lack sophisticated volumetric modeling capabilities to represent, construct and manipulate objects of interest within a volumetric dataset. Integrating manipulations such as non-linear deformations and constructions similar to those in solid modeling into the visualization process would have significant value in surgical planning and simulation. Interrogative visualization--the ability to extract, enumerate, deform and track objects of interest is also crucial in other visualization tasks. The conventional approach to visualize the volume deformation and construction process is to construct an intermediate volume for each step of manipulation. This is prohibitively time consuming and costly. This paper presents an approach to overcome this constraint. We model the target capture space as octrees. The target octree is adaptively subdivided to efficiently balance the complexity of deformation and visualization. The source volumetric data can either be in octree or conventional 3D array format. Deformations are specified by landmark displacements, and in-between deformation is filled in by scattered data interpolation. Volumetric modeling is supported by a Constructive Solid Geometry (CSG) structure. Spatial Coherency is exploited in the view-dependent node traversal and projection of individual octree nodes.

Algorithms↗