A risk explicit interval linear programming model for uncertainty-based environmental economic optimization in the Lake Fuxian watershed, China.
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A linear program formulation for the segmentation of Ciona membrane volumes.
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We address the problem of cell segmentation in confocal microscopy membrane volumes of the ascidian Ciona used in the study of morphogenesis. The primary challenges are non-uniform and patchy membrane staining and faint spurious boundaries from other organelles (e.g. nuclei). Traditional segmentation methods incorrectly attach to faint boundaries producing spurious edges. To address this problem, we propose a linear optimization framework for the joint correction of multiple over-segmentations obtained from different methods. The main idea motivating this approach is that multiple over-segmentations, resulting from a pool of methods with various parameters, are likely to agree on the correct segment boundaries, while spurious boundaries are methodor parameter-dependent. The challenge is to make an optimized decision on selecting the correct boundaries while discarding the spurious ones. The proposed unsupervised method achieves better performance than state of the art methods for cell segmentation from membrane images. (+info)
Transportation or CT scanners: a theory and method of health resources allocation.
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Cost containment and access to appropriate care are the two most frequently discussed issues in contemporary health policy. Conceiving of the health services available in specific regions as "packages" of diverse items, the authors of this article consider the economic trade-offs among the various resources needed for appropriate care. In the discussion that follows, we examine the trade-offs between two divergent offering of the health care system: high technology medicine and support services. Specifically, we examine several strategies designed to achieve an optimal mix of investments in CT scanners and transportation resources in the South Chicago region. Using linear programming as a method for examining these options, the authors found that 1) the proper location of CT scanners is as important for cost containment as optimal number, and 2) excess capacity in the utilization of a single resource--CT scanners--need not imply inefficiency in the overall delivery of the service. These findings help demonstrate the importance of viewing health care as a package of interrelated services, both for achieving cost containment and for providing access to appropriate care. (+info)
Probabilistic constraint satisfaction: application to radiosurgery.
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Although quite successful in a variety of settings, standard optimization approaches can have drawbacks within medical applications. For example, they often provide a single solution which is difficult to explain, or which can not be incrementally modified using secondary "soft" constrains that are difficult to encode within the optimization. In order to address these issues, we have developed a probabilistic optimization technique that allows the user to enter prior probability distributions (Gaussian) for the parameters to be optimized as well as for the constraints on the parameters. Our technique combines the prior distributions with the constraints using Bayes' rule. The algorithm produces not only a set of parameter values, but variances on these values and covariances showing the correlations between parameters. We have applied this method to the problem of planning a radiosurgical ablation of brain tumors. The radiation plan should maximize dose to tumor, minimize dose to surrounding areas, and provide an even distribution of dosage across the tumor. It also should be explainable to and modifiable by the expert physicians based on external considerations. We have compared the results of our method with the standard linear programming approach. (+info)
Impact of expanded-duty assistants on cost and productivity in dental care delivery.
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Data from an experimental dental program are used to develop a linear programming model of dental care delivery that the authors use to examine the economic implications of introducing expanded-duty dental assistants (EDDA's) in three types of dental practices. The authors examine the changes in productivity and profitability that result from hiring one or more EDDAs and conclude that a dentist in solo practice can more than double his net revenue by hiring one EDDA but will not increase his productivity further by hiring additional EDDAs. Two- and three-dentist groups also can increase revenue by hiring EDDAs, but, beyond a certain point, an inverse relationship exists between the number of auxiliaries hired and net revenue generated. (+info)
A national study of the efficiency of hospitals in urban markets.
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Using a sample of 3,000 urban hospitals, this article examines the contributions of selected hospital characteristics to variations in hospital technical efficiencies, while it accounts for multiple products and inputs, and controls for local environmental variations. Four hospital characteristics are examined: hospital size, membership in a multihospital system, ownership, and payer mix (managed care contracts, percent Medicare, and percent Medicaid). Ownership and percent Medicare are consistently found to be related significantly to hospital efficiency. Within the ownership variable, government hospitals tend to be more efficient and for-profit hospitals less efficient than other hospitals. Higher percentages of Medicare payment are negatively related to efficiency. While not consistently significant across all five of the MSA size categories in which the analyses are conducted, possession of managed care contracts, membership in a multihospital system, and size all are consistently related positively to hospital technical efficiency. These variables are also all significant when the hospitals are examined in a combined analysis. Percent Medicaid was not significant in any of the analyses. Implications for policy and the need for methodological work are discussed. (+info)