PO-0638: Adaptive dose painting by numbers for head and neck cancer: interim analysis of a randomised trial

International audience1. Recherches sur le Fayuan zayuan yuanshi ji de Sengyou (445-518), première anthologie de rites bouddhiques (suite : le contenu des juan 4 et 5) Notre travail de reconstruction du Fayuan zayuan yuanshi ji 法苑雜緣原始集 (Anthologie [pour comprendre] le commencement et l’origine de diverses [pratiques] dans le jardin des devoirs ; ci-après Fayuan) de Sengyou 僧祐 (445-518) nous a amenés cette année à nous pencher sur les 22 premiers titres de la section sur le saṃgha (Sengbao 僧寶, « Le joyau de la Loi ..

Design and Fabrication Concepts of a Compact Undulator with Laser-Structured 2G-HTS Tapes

To produce small-scale high-field undulators for table-top free electron lasers (FELs), compact designs have been proposed using high temperature superconducting (HTS) tapes, which show both large critical current densities and high critical magnetic fields with a total tape thickness of about 50 μm and a width of up to 12 mm. Instead of winding coils, a meander structure can be laser-scribed directly into the superconductor layer, guiding the current path on a quasi-sinusoidal trajectory. Stacking pairs of such scribed tapes allows the generation of the desired sinusoidal magnetic fields above the tape plane, along the tape axis. Two practically feasible designs are presented, which are currently under construction at KIT: A coil concept wound from a single structured tape with a length of 15 m, which is a progression of a design that has been presented already in the past, as well as a novel stacked and soldered design, made from 25 cm long structured tapes, soldered in a zig-zag-pattern. In this contribution the designs are briefly recapped and the experimental progress is presented

Pre-segmented 2-Step IMRT with subsequent direct machine parameter optimisation – a planning study

<p>Abstract</p> <p>Background</p> <p>Modern intensity modulated radiotherapy (IMRT) mostly uses iterative optimisation methods. The integration of machine parameters into the optimisation process of step and shoot leaf positions has been shown to be successful. For IMRT segmentation algorithms based on the analysis of the geometrical structure of the planning target volumes (PTV) and the organs at risk (OAR), the potential of such procedures has not yet been fully explored. In this work, 2-Step IMRT was combined with subsequent direct machine parameter optimisation (DMPO-Raysearch Laboratories, Sweden) to investigate this potential.</p> <p>Methods</p> <p>In a planning study DMPO on a commercial planning system was compared with manual primary 2-Step IMRT segment generation followed by DMPO optimisation. 15 clinical cases and the ESTRO Quasimodo phantom were employed. Both the same number of optimisation steps and the same set of objective values were used. The plans were compared with a clinical DMPO reference plan and a traditional IMRT plan based on fluence optimisation and consequent segmentation. The composite objective value (the weighted sum of quadratic deviations of the objective values and the related points in the dose volume histogram) was used as a measure for the plan quality. Additionally, a more extended set of parameters was used for the breast cases to compare the plans.</p> <p>Results</p> <p>The plans with segments pre-defined with 2-Step IMRT were slightly superior to DMPO alone in the majority of cases. The composite objective value tended to be even lower for a smaller number of segments. The total number of monitor units was slightly higher than for the DMPO-plans. Traditional IMRT fluence optimisation with subsequent segmentation could not compete.</p> <p>Conclusion</p> <p>2-Step IMRT segmentation is suitable as starting point for further DMPO optimisation and, in general, results in less complex plans which are equal or superior to plans generated by DMPO alone.</p

EXclusion of non-Involved uterus from the Target Volume (EXIT-trial): An individualized treatment for locally advanced cervical cancer using modern radiotherapy and imaging techniques

Background: Definitive chemoradiotherapy is standard of care in locally advanced cervical cancer (LACC). Both toxicity and local relapse remain major concerns in this treatment. We hypothesize that a magnetic resonance imaging (MRI) based redefining of the radiotherapeutic target volume will lead to a reduction of acute and late toxicity. In our center, chemoradiotherapy followed by hysterectomy was implemented successfully in the past. This enables us to assess the safety of reducing the target volume but also to explore the biological effects of chemoradiation on the resected hysterectomy specimen. Methods: The EXIT-trial is a phase II, single arm study aimed at LACC patients. This study evaluates whether a MRI-based exclusion of the non-tumor-bearing parts of the uterus out of the target volume results in absence of tumor in the non-high doses irradiated part of the uterus in the hysterectomy specimen. Secondary endpoints include a dosimetric comparison of dose on normal tissue when comparing study treatment plans compared to treatment of the whole uterus at high doses; acute and chronic toxicity, overall survival, local relapse- and progression-free survival. In the translational part of the study, we will evaluate the hypothesis that the baseline apparent diffusion coefficient (ADC) values of diffusion weighted MRI and its evolution 2 weeks after start of CRT, for the whole tumor as well as for intra-tumoral regions, is prognostic for residual tumor on the hysterectomy specimen. Discussion: Although MRI is already used to guide target delineation in brachytherapy, the EXIT-trial is the first to use this information to guide target delineation in external beam radiotherapy. Early therapy resistance prediction using DW-MRI opens a window for early treatment adaptation or further dose-escalation on tumors/intratumoral regions at risk for treatment failure

Mitigation of parasitic losses in thequadrupole resonator enabling directmeasurements of low residual resistancesof SRF samples

The quadrupole resonator QPR is a dedicated sample test cavity for the RF characterization of superconducting samples in a wide temperature, RF field, and frequency range. Its main purpose is high resolution measurements of the surface resistance with direct access to the residual resistance, thanks to the low frequency of the first operating quadrupole mode. In addition to the well known high resolution of the QPR, a bias of measurement data toward higher values has been observed, especially in higher harmonic quadrupole modes. Numerical studies show that this can be explained by parasitic RF losses on the adapter flange used to mount samples into the QPR. Coating several micrometers of niobium on those surfaces of the stainless steel flange that are exposed to the RF fields significantly reduced this bias, enabling a direct measurement of a residual resistance smaller than 5 n amp; 937; at 2 K and 413 MHz. A constant correction based on simulations was not feasible due to deviations from one measurement to another. However, this issue is resolved given these new result

Systems of Differential Algebraic Equations in Computational Electromagnetics

Starting from space-discretisation of Maxwell's equations, various classical formulations are proposed for the simulation of electromagnetic fields. They differ in the phenomena considered as well as in the variables chosen for discretisation. This contribution presents a literature survey of the most common approximations and formulations with a focus on their structural properties. The differential-algebraic character is discussed and quantified by the differential index concept