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Background: Dual‐energy (DE)‐CBCT represents a promising imaging modality that can produce virtual monoenergetic (VM) CBCT images. VM images, which provide enhanced contrast and reduced imaging artifacts, can be used to assist in soft‐tissue visualization during image‐guided radiotherapy. Purpose: This work reports the development of TIGRE‐DE, a module in the open‐source TIGRE toolkit for the performance of DE‐CBCT and the production of VM CBCT images. This module is created to make DE‐CBCT tools accessible in a wider range of clinical and research settings. Methods: We developed an add‐on (TIGRE‐DE) to the TIGRE toolkit that performs DE material decomposition. To verify its performance, sequential CBCT scans at 80 and 140 kV of a Catphan 604 phantom were decomposed into equivalent thicknesses of aluminum (Al) and polymethyl‐methylacrylate (PMMA) basis materials. These basis material projections were used to synthesize VM projections for a range of x‐ray energies, which were then reconstructed using the Feldkamp‐Davis‐Kress (FDK) algorithm. Image quality was assessed by computing Hounsfield units (HU) and contrast‐to‐noise ratios (CNR) for the material inserts of the phantom and comparing with the constituent 80 and 140 kV images. Results: All VM images generated using TIGRE‐DE showed good general agreement with the theoretical HU values of the material inserts of the phantom. Apart from the highest‐density inserts imaged at the extremes of the energy range, the measured HU values agree with theoretical HUs within the clinical tolerance of ±50 HU. CNR measurements for the various inserts showed that, of the energies selected, 60 keV provided the highest CNR values. Moreover, 60 keV VM images showed average CNR enhancements of 63% and 66% compared to the 80 and 140 kV full‐fan protocols. Conclusions: TIGRE‐DE successfully implements DE‐CBCT material decomposition and VM image creation in an accessible, open‐source platform. [ABSTRACT FROM AUTHOR]

Welfare economics must adapt to the growing consensus over the assignment of rights to animals. We extend nonmarket valuation techniques to the study and measurement of the preferences of Chinook salmon regarding their aquatic habitat and the value of their existence. We find that these techniques are as valid for fish as they are for humans. Our applied study indicates that opportunities exist for Pareto-improving trades between salmon and California agricultural and hydropower interests. (JEL Q510), I. INTRODUCTION In an important book, Roderick Nash (1989) places the development of environmental ethics into the broader framework of the expansion of rights. He argues that the extension of [...]

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.jenvman.2005.09.012 Byline: Yassert Gonzalez-Alvarez (a), Andrew G. Keeler (b), Jeffrey D. Mullen (c) Keywords: Water; Irrigation; Economics; Groundwater Abstract: We create a proxy for the cost of irrigation water in Georgia from a sample of Georgia irrigators by investigating the marginal cost of pumping groundwater. We then combine this proxy with agronomic and climatic variables to estimate the response of agricultural water use to differences in the marginal cost of irrigation. The results show that pumping costs are a significant determinant of water use, and imply that agricultural water use would be moderately affected by institutional changes that would explicitly price water. Author Affiliation: (a) Planning Department, Southwest Florida Water Management District, Brooksville, FL, USA (b) School of Public Policy and Management, The Ohio State University, 310-C Page Hall, 1810 College Road, The Ohio State University, Columbus, OH 43210, USA (c) Department of Agricultural and Applied Economics, The University of Georgia, Athens, GA, USA Article History: Received 17 December 2004; Revised 29 August 2005; Accepted 21 September 2005

Emissions trading markets have been successful in addressing pollution problems where regulated entities can be treated in a similar manner and precise control of emissions quantities across time and space is not critical. In other situations, trading must account for individual circumstances, complexity, and the patchwork of existing regulations. In these circumstances trading systems have elements of contracts, in that transactions are unique and must be negotiated and approved individually. Such programs imply a high payoff to improved environmental information and to innovations in trading systems that allow making better use of such information. (JEL Q21, Q25, Q28), I. INTRODUCTION Emissions trading programs have been riding a wave of ascendancy in environmental policy since the Clean Air Act Amendments of 1990 created the Acid Rain Trading Program. This [...]

A study was conducted to determine if exposure of minorities to environmentally unsafe toxic releases constitutes aversive racism. An empirical investigation of the association between race and exposure for Census block groups in George and Ohio revealed that the role of race is influenced by the breadth of the explanatory model used in the analysis. Implications for environmental policymaking are discussed.

Simulation results based on a model of landfill costs express certain reservations with the currently held belief that disposing larger volumes of wastes in regional landfills is cost effective. By considering factors such as construction, operating, externality and political costs, the model reveals that the advantages of a larger consignment is offset by the increase in transportation charges and political costs of existing zonal facilities. Intended host facilities may encounter problems from regional partners.

Three competing local options are examined by developing a model of municipal choice of solid waste disposal technologies. The three options include incineration in energy recovery facilities (ERF), landfilling and recycling. It is shown that incineration and the ERF optimum depend on the underlying costs of the different disposal options and the characteristics of the waste stream.

An enforcement model was developed wherein non-compliance penalties are determined by the strategic interaction between regulatory agencies and industries. The balance between monitoring and sanctioning activities is highly dependent on the power of the regulator's enforcement technology. This power reflects the political, legal and social opinions toward the issues being enforced. The model proves that grave offenses will be characterized by low detection rates and strong enforcement while pollution will be characterized by frequent interaction with regulators and relatively mild enforcement activity.

In this paper we develop a model to simulate the impacts of changes in freshwater flows into and out of the San Francisco Bay/Delta on the California Central Valley salmon fishery. The model also describes interactions among these water flow controls, hatchery operations, and harvest regulation. Traditionally, the management of California's freshwater resources and anadromous fisheries has been undertaken separately, in the literature and in practice. We demonstrate the potential gains from a coordinated management approach.