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Purpose : Groupe Européen de Curiethérapie (GEC) and European Society for Radiotherapy & Oncology (ESTRO) has proposed a rectal dose constraint of the most exposed 2-cc volume (D 2cc of ≤ 75 Gy EQD 2α/β = 3) during external- beam plus high-dose-rate brachytherapy (HDR-BT) in localized prostate cancer patients. This study aimed to evaluate D 2cc for rectal contouring via interobserver variability. Material and methods: Four blinded observers contoured rectums of 5 patients. Rectal contouring anatomical limits were determined through previous consensus. Dose-volume histogram (DVH) dosimetric parameters (D 0.1cc , D 1cc , and D 2cc ) were analyzed according to GEC/ESTRO recommendations and subjected to intra- and interobserver comparisons. Latter comparisons involved coefficients of variation. For each parameter, the mean, standard deviation (SD), and range were evaluated. The effect of interobserver variation on total dose was analyzed by estimating the biologically equivalent rectal dose (EQD 2α/β = 3). Results : Interobserver coefficients of variation for D 0.1cc , D 1cc , and D 2cc were 5.7%, 4.5%, and 4%, respectively. The high­est interobserver rectal delineation variation yielded a rectal dose difference up to 5.8 Gy EQD2. Estimated intraobserver variation for the reported D 2cc was 5.5% in the worst-case scenario (non-significant). Conclusions : We observed acceptable interobserver variability in EQD2 for D 2cc , with strong impacts on clinical threshold levels (D 2cc ≤ 75 Gy EQD2) in some cases. This small, single-center analysis will be extended in a multicenter study.

In order to help address and contribute to the emerging demand for LOX/Methane propulsion research is conducting a suite of investigations and a series of articles. The work presented here is a continuation for the article "Cryogenic System Development for LOX/Hydrocarbon Propulsion Research", presented at the 2011 JPC conference, . Many of the research projects conducted at the Center for Space Exploration Technology Research (cSETR) at The University of Texas at El Paso (UTEP) require a system capable of producing in-house liquid methane (LCH4) and delivering that LCH4 as well as Liquid Oxygen (LOX) to the various test articles and apparatus. This requirement includes the necessity for remote control and data acquisition. The system’s requirement for a methane condensation process surfaced due to the local unavailability of liquid Methane in manageable quantities and was done interatively with the development and testing of several preliminary small-scale condensers. The operation of the test articles required that the propellants were fed to the system in a cryogenic state, therefore purging and cool down features were incorporated in the delivery system design. The delivery process is activated and monitored remotely through a DAQ and controls system. It has also been equipped with a redundant manual system to allow for operations during an emergency or anamoly override of the automated system. The presented cryogenic delivery system is designed to comply with industry standards and university safety regulations and the technical approach, system capability and effort are presented herein for the benefit of others seeking similar system design or function.

This paper details the Multi-Purpose Optically Accessible Combustor (MOAC) and its utilization for injector design and combustion research. The MOAC is intended for experimentation and research of combustion of liquid and gaseous propellants. For the uses at the Center for Space Exploration Technology research, there is a particular focus on using the MOAC with liquid Oxygen and liquid Methane as propellant fuels. The MOAC system is versatile and can be used with a number of injector styles. Current interest centers on Shear Coaxial injectors common with Oxygen and Methane systems. Descriptions of the test procedure to ensure proper ignition and testing are described. Instrumentation critical to obtaining test data for analysis of the thermodynamic properties of both the propellants and the combustion chamber are detailed as well. Optical instrumentation associated with the MOAC system is thoroughly described to identify the characteristics of the spray and combustion dynamics. Finally testing parameters will be explained as well as a summary of initial test results concluded from initial testing.

This paper details the design and development process of a Multi-Purpose Optically Accessible Rocket Combustor (MOAC) at the Center for Space Exploration Technology Research (cSETR) at the University of Texas at El Paso. The MOAC is intended for studying combustion characteristics of liquid and gaseous propellants, in particular liquid Oxygen (LOX) and liquid Methane. The MOAC derived additional design considerations from data necessary for the development of a 25 lbf LOX-Methane engine (material compatibility with propellants, temperatures up to 3500°K, and pressures reaching 20 Bar). The design goals include modular combustor.