The Protomedicato Tribunal and minorities in Castile at the end of the 17th century: the case of surgeon Roldán Solimán

[EN] This note aims to provide a small set of documents which report the vicissitudes of a North-African Muslim surgeon who tried to settle professionally during the late seventeenth century in the Kingdom of Castile. The four letters exchanged between the Royal Palace and the Castilian tribunal of the Protomedicato reveal that the Spanish king Charles II (1661-1700) resoluted supported the surgeon's aspirations, and the Protomedicato's concerted resistence to the royal will. These eloquent documents shed light on the history of the Castilian Protomedicato during the final years of the reign of the last Habsburg king in Spain by providing evidence about the role of this institution in the process of segregation/exclusion of ethnic minorities from the practice of health professions.[ES] El objeto de esta nota es presentar y editar una colección documental muy breve cuyo contenido nos informa sobre las vicisitudes de un cirujano musulmán norteafricano que a finales del siglo XVII busca su asentamiento profesional en la Corona de Castilla. Las cuatro cartas entre el Palacio Real y el Tribunal del Protomedicato, que se conservan en relación a este asunto, revelan tanto el decidido apoyo del Rey Carlos 11 (1665-1700) a las pretensiones del cirujano, como la fuerte resistencia ofrecida por el Protomedicato a la voluntad real. Esta expresiva documentación arroja luz en torno a la historia del Protomedicato en la Corona de Castilla durante los años finales del reinado del último Habsburgo en España, ilustrándonos sobre el papel entonces jugado por esta institución en el proceso de segregación/exclusión de las minorías étnicas, de la práctica de las ocupaciones sanitarias.Peer reviewe

A GPU implementation of a track-repeating algorithm for proton radiotherapy dose calculations

An essential component in proton radiotherapy is the algorithm to calculate the radiation dose to be delivered to the patient. The most common dose algorithms are fast but they are approximate analytical approaches. However their level of accuracy is not always satisfactory, especially for heterogeneous anatomic areas, like the thorax. Monte Carlo techniques provide superior accuracy, however, they often require large computation resources, which render them impractical for routine clinical use. Track-repeating algorithms, for example the Fast Dose Calculator, have shown promise for achieving the accuracy of Monte Carlo simulations for proton radiotherapy dose calculations in a fraction of the computation time. We report on the implementation of the Fast Dose Calculator for proton radiotherapy on a card equipped with graphics processor units (GPU) rather than a central processing unit architecture. This implementation reproduces the full Monte Carlo and CPU-based track-repeating dose calculations within 2%, while achieving a statistical uncertainty of 2% in less than one minute utilizing one single GPU card, which should allow real-time accurate dose calculations

Analytical expressions for stopping-power ratios relevant for accurate dosimetry in particle therapy

In particle therapy, knowledge of the stopping-power ratios (STPRs) of the ion beam for air and water is necessary for accurate ionization chamber dosimetry. Earlier work has investigated the STPRs for pristine carbon ion beams, but here we expand the calculations to a range of ions (1 <= z <= 18) as well as spread out Bragg peaks (SOBPs) and provide a theoretical in-depth study with a special focus on the parameter regime relevant for particle therapy. The Monte Carlo transport code SHIELD-HIT is used to calculate complete particle-fluence spectra which are required for determining STPRs according to the recommendations of the International Atomic Energy Agency (IAEA). We confirm that the STPR depends primarily on the current energy of the ions rather than on their charge z or absolute position in the medium. However, STPRs for different sets of stopping-power data for water and air recommended by the International Commission on Radiation Units & Measurements (ICRU) are compared, including also the recently revised data for water, yielding deviations up to 2% in the plateau region. In comparison, the influence of the secondary particle spectra on the STPR is about two orders of magnitude smaller in the whole region up till the practical range. The gained insights enable us to propose an analytic approximation for the STPR for both pristine and SOBPs as a function of penetration depth, which parametrically depend only on the initial energy and the residual range of the ion, respectively.Comment: 21 pages, 5 figures, fixed bug with figures in v

TH‐C‐T‐617‐05: Monte Carlo Simulations of a Nozzle for the Treatment of Ocular Tumors with High‐Energy Proton Beams

Purpose: To develop a Monte Carlo simulation model for ocular proton beam therapy, validate its predictions with measurements, and commission an ocular treatment planning system using simulated proton beam data. Method and Materials: We commissioned the EYEPLAN ocular treatment planning system for proton radiotherapy using only dosimetric data from Monte Carlo simulations. The commissioning comprised two main tasks: generating nozzle‐specific parameters and dose profiles and entering them into the treatment planning system, and testing the accuracy of the planning system\u27s dose predictions under various beam conditions that are representative of ocular melanoma treatments. The MCNPX Monte Carlo simulation code was used with a detailed, 3‐dimensional model of an ocular beamline. Simulations were carried out to generate both input dose distributions for the treatment planning system as well as validation data to test the accuracy of the TPS predictions. The simulation model was benchmarked against measured dose distribution from Harvard Cyclotron Laboratory (Cambridge) and the Northeast Proton Therapy Center (Boston). Measurements were made with ionization chambers, diodes, and radiographic film. Results: Benchmark comparisons revealed maximum differences between absorbed dose profiles from simulations and measurements of 6% and 0.6 mm, while typical differences were less than 2% and 0.2 mm. The computation time for the entire virtual commissioning process is less than one day. Conclusion: The study revealed that, after a significant development effort, a Monte Carlo model of a proton therapy apparatus is sufficiently accurate and fast for commissioning a treatment planning system. With relatively little additional effort, additional capability can be added to the model, such as the prediction of output factors. © 2005, American Association of Physicists in Medicine. All rights reserved

MO‐G‐BRC‐02: Patient Specific Out‐Of‐Field Dose Calculation Tool for 6MV and 18MV: Development and Validation

Purpose: A factor that greatly limits the use of Monte Carlo methods for patient specific dose calculations in research is the substantial amount of effort required to define the Monte Carlo geometry of the actual treatment and patient setup. The purpose of this study was to develop and validate computational infrastructure to automatically convert radiation field parameters and computed tomography (CT) data from Digital Imaging and Communications (DICOM)format to Monte Carlo input format, and automate a Monte Carlo based dose calculation system for external beam photon radiation therapy. Methods: Computational infrastructure was developed using DCMTK, the DICOM tool kit. The dose calculation system (ADCS) was automated using a shell script. For validation of the ADCS, infield doses calculated by the ADCS were compared with those calculated by the treatment planning software using an eight‐field, 6 MV, step‐and‐shoot intensity modulated radiation therapy plan. Doses were calculated in a water phantom, and an anthropomorphic phantom based on CT data. Results: For each field, more than 95% of the dose voxels passed 3% and 3‐mm criteria of gamma‐index analysis of 3‐D dose distributions in the water phantom. The central axis depth dose curve agreed with in 15% (1stardard deviation) to the TPS calculations in the anthropomorphic phantom for a single representative field of the RT plan. Conclusions: The ADCS can accurately extract patient‐specific radiation treatment parameters and automatically incorporate them into the Monte Carlo format and create final dose distributions compatible with commercial treatment planning systems. This automated calculation infrastructure reduces the time required to define the Monte Carlo geometry and potential for human error. This system is capable of automating and calculating doses for conventional radiation therapy and 18MV. It is also capable of calculating out‐of‐field doses (region of interest in patient anatomy can be selected prior to running ADCS). © 2011, American Association of Physicists in Medicine. All rights reserved

Neutron radiation area monitoring system for proton therapy facilities

A neutron radiation area monitoring system has been developed for proton accelerator facilities dedicated to cancer therapy. The system comprises commercial measurement equipment, computer hardware and a suite of software applications that were developed specifically for use in a medical accelerator environment. The system is designed to record and display the neutron dose-equivalent readings from 16 to 24 locations (depending on the size of the proton therapy centre) throughout the facility. Additional software applications provide for convenient data analysis, plotting, radiation protection reporting, and system maintenance and administration tasks. The system performs with a mean time between failures of \u3e6 months. Required data storage capabilities and application execution times are met with inexpensive off-the-shelf computer hardware. © The Author 2005. Published by Oxford University Press. All rights reserved

SU‐GG‐T‐415: Automated Photon Monte Carlo Linear Accelerator Model for Calculating In‐Field and Out‐Of‐Field Dose

Purpose: Monte Carlo methods have been used extensively to calculate radiation does to organs both in‐field and far‐field. However, particularly for out‐of‐field dose calculations, this process has relied on the very time consuming and potentially error‐prone manual conversion of radiation field parameters and CT datum to a Monte Carlo input format. The purpose of this study was to develop computational infrastructure to automate a Monte Carlo‐based dose calculation algorithm for a previously modeled and benchmarked Varian 2100 linear accelerator operating at 6 MV. This system would be suitable for in‐field and out‐of‐field calculations. Method and Materials: A computer program was written using a Digital Imaging and Communications Tool Kit (DCMTK) to extract patient position data and radiation field parameters from a photon radiation therapy (RT) file and, based on this data, set the MCNPX simulation geometry for the modeled linear accelerator. A shell script was written to automate extraction, writing MCNPX geometry input files and submission of simulations to a computer cluster. The accuracy of the automation process was tested by examining the accuracy of the in‐field dose from an eight‐field, intensity modulated radiotherapy plan. Each field corresponded to a different gantry angle and set of control points. For each field, simulated depth‐dose curves and cross‐filed dose profiles at isocenter were compared with dose profiles calculated from Varian treatment planning software (Eclipse). Results: In‐field dose profiles calculated from the automated system agreed within 4% to dose profiles calculated using the Eclipse. Statistical uncertainty of simulated in‐field dose profiles was at most 4%. Conclusion: The automated dose calculation system accurately extracted the complex treatment geometry parameters, and successfully incorporated them into the Monte Carlo framework. This process substantially reduces the time required, and potential for error, for conducting Monte Carlo simulations within or outside the treatment field. © 2010, American Association of Physicists in Medicine. All rights reserved

Neutron shielding verification measurements and simulations for a 235-MeV proton therapy center

The neutron shielding at the Massachusetts General Hospital\u27s 235-MeV proton therapy facility was investigated with measurements, analytical calculations, and realistic three-dimensional Monte Carlo simulations. In 37 of 40 cases studied, the analytical calculations predicted higher neutron dose equivalent rates outside the shielding than the measured, typically by more than a factor of 10, and in some cases more than 100. Monte Carlo predictions of dose equivalent at three locations are, on average, 1.1 times the measured values. Except at one location, all of the analytical model predictions and Monte Carlo simulations overestimate neutron dose equivalent. © 2002 Elsevier Science B.V. All rights reserved